Dayton Audio Ultimax UM18-22 in a 24 cuft enclosure: what design?

[Infrasonic]

4 minutes ago, Droogne said:

If you say simulated numbers are irrelevant, how do I know if I'm between those .577 and .8? 

What I mean is trying to attain a finished product with a "F3 of something..." will be irrelevant because that F3 you simulated will no longer be the actual inroom F3. 

The riser will extend down as low as your electronics and displacement allow.

[Droogne]

2 minutes ago, Infrasonic said:

What I mean is trying to attain a finished product with a "F3 of something..." will be irrelevant because that F3 you simulated will no longer be the actual inroom F3. 

The riser will extend down as low as your electronics and displacement allow.

Oh yes, I wasn't aiming at some kind of particular F3 with those simulations. Was using it for comparison.

 

[SME]

8 hours ago, Droogne said:

Wow! You guys are awesome! Lots to read! I'm trying to understand everything, but as even you guys are not sure about everything it will take me a while

When modeled against qtc I get these values (see pictures). I'm now not sure what to extract from this.. Should I try to land a Qtc as low as I can, which is at least between 0.707 and 0.53? If so, when modeled for 1 driver In get a Qtc: 0.605 and an F3: 30.2hz. 2 drivers: Qtc 0.6712 and F3: 29.2hz. 3 drivers: Qtc 0.737 and F3: 28.9 .

There is no volume where I get the lowest F3 and an Qtc below 0.707. "Best of both worlds" is at 9.71 cuft where the F3 is also 28.9 (only slightly higher than the lowest possible)

I will be using Auddyssey MultiEQ in my Marantz SR7011. Will be buying a seperate EQ in the future (from the moment I need more than 2 seperate LFE frequency ranges). 

Power is not a problem to be considered, I want to finetune this setup under the consideration that I have enough power. I will upgrade if necessary. Using a pair of seperate ported subs is a possibility in the future if I don't like the sound.

As @Infrasonic suggested, you should probably ignore F3, which is largely irrelevant if you have EQ capability.  And you should make having EQ capability a priority if at all possible.   I think there's consensus that it's absolutely necessary in order to compensate for room differences, if nothing else.  Even a lot high value commercial products offer at least rudimentary signal shaping these days.  For DIY, it's probably easiest to buy an amp with EQ capability built-in.

A more important parameter than F3 is the resonance frequency of the sealed system, often called Fb.  This is where the transition between flat(-ish) response and 12 dB/octave roll-off is centered, in the anechoic response without EQ.  The Qtc roughly describes the bandwidth of the transition and indirectly indicates important trade-offs that affect the maximum performance of the system that can be obtained using EQ.

Essentially any one of three things limit the output of a subwoofer system at the low end:

• displacement
• amp voltage
• amp power

Displacement is the amount of air the cones can move.  You can estimate this by multiplying the number of drivers by the cone surface area (Sd) and the maximum excursion (Xmax).  These are usually published in mm^2 and mm, and you can convert the final number to liters by dividing by one million.  For a sealed system, anechoic output is directly related to displacement at a given frequency, and the requirement increases by 12 dB/octave as frequency drops.  In practice, your room will provide gain at the low end, and the displacement requirement doesn't increase as fast down there when used in-room.  If the displacement limit is exceeded, the subs may sound bad, and some drivers can even be damaged.

Amp voltage is the maximum voltage the amp can output.  It is a fundamental limitation of the amp's design.  This information is rarely published in the specs, even though it ought to be.  It will usually be at least as high as the voltage required to achieve the rated power into 8 ohm impedance and typically not much more than that.  This voltage can be estimated using: V = sqrt(P*Z) where Z equals 8 ohm and P equals the power rating into 8 ohm.

Amp power is the maximum power the amp can output, and is often less than what the max voltage would theoretically deliver, when impedance is less than 8 ohm or so.  Whereas the max voltage is essentially defined precisely by the design, max power can be a bit harder to pin down, despite what the specs may seem to suggest.  Often, an amp will be able to deliver a lot of power for a very short time (burst), but its ability to deliver high power for longer durations may be limited by the capability of the power supply and/or the power reserves in its capacitance.  Unfortunately, many amp vendors exaggerate their real world power capabilities in the specs, quoting a "burst" number that is based on max voltage and valid only under very ideal circumstances, which may not even apply at all to low frequencies.  Furthermore, even a very powerful amp, when driven for long enough can overheat and reduce power output because of thermal limitations.  For subwoofer use, the burst numbers tend to be too short term to be of use, but thermal limits are much less likely to be a problem.  The important information is power output on a moderate timescale of maybe a few seconds.  Some people on here and at AVSForum have done some "real world"  testing of true moderate timescale power capabilities, which are likely of interest when shopping for an amp.

The reason I distinguish between amp voltage and amp power is important and has to do with the Qtc.  The Qtc affects both the sensitivity (output at each frequency vs. voltage) and the impedance.  The impedance of a subwoofer is frequency-dependent, and it relates to how much power is consumed for a given voltage.  The voltage going to the sub is essentially the same as the signal fed to the amp, except with some constant (dB) gain.  The actual amount of power consumed (turned into heat in the voice coil) depends on the impedance which varies considerably by frequency, especially around Fb.  The higher the impedance, the less power consumed.   A sealed system always has an impedance peak at Fb, and so a sine wave that Fb will draw and dissipate very little power from the amp.  As such, a sealed system is also extremely efficient (output at each frequency vs. power) right at Fb.

For frequencies far below Fb, a large box volume and lower Qtc will generally give you better voltage sensitivity *and* power efficiency, and the effect of the box volume is rather modest for frequencies far above Fb.  However, for frequencies around Fb, the choice of box volume and resulting Qtc involves a trade-off between sensitivity and efficiency.  In a larger box with lower Qtc, the sensitivity around Fb will be diminished compared to a smaller box and higher Qtc.  This is what you see when you plot simulated "frequency response" curves (which are really just sensitivity curves) in a design simulator.  Lower Qtc systems begin transition from flat to roll-off at a much higher frequency (leading to a higher F3), but the transition region, where roll-off is less than 12 dB/octave,  is also much wider than for a higher Qtc system.  However, this does not tell the whole story.  Even though the "response" (sensitivity) is diminished around Fb in a low Qtc system, the efficiency is actually a lot higher there than in a high Qtc system.  Most design simulators do not plot efficiency directly, but efficiency is important, both for determining whether the amp is capable of driving the system to the desired output and to understand how much power is being dissipated in the coil.

Note that it is always possible to increase the sensitivity of a system by running a second driver in parallel.  When two drivers are run in parallel, the overall impedance drops by half; the efficiency goes up by 3 dB; and the sensitivity goes up by 6 dB.  The caveat, of course, is that the amp must now operate into a lower overall impedance, and double the power will be required to drive both to full displacement.

As such, there is a rather complicated balance to be achieved between each of the three limiting parameters in an optimal design.  To try to simplify things, here's a list of problems that you may encounter if the box is "too small" or "too big":

Too small (high Qtc):

• Output far below Fb limited by max voltage or max power
• Low overall low-end efficiency ==> more power dissipated in the coils ==> more likelihood of power compression or even thermal damage during heavy use

Too large (low Qtc):

• Output around Fb limited by max voltage (but not max power)
• Easier to exceed displacement limits at bottom end ==> more likelihood of damage from over-excursion (also depending on driver choice)

Apart from that, there is no "right" answer as far as what Qtc is best.  It depends on the driver, the amp, and the intended use.   Simulations can be very helpful here.  More sophisticated design programs will plot impedance along with response and excursion for a given input voltage.  Power requirement can be computed for a particular frequency using:  P = V^2/Z.  Using this information, you can estimate how much output (under anechoic or ground-plane conditions) at each frequency you can achieve before hitting one of the aforementioned limits, and which of those limits you'll hit.  And then you can optimize from there.

Or if that's more than you want to be bothered with, you can try copying an existing build using the same drivers and match the enclosure size, accepting whatever compromise the original designer chose.  Plenty of people avoid the complexity of doing their own design and are perfectly satisfied with the results.

Sorry again about the length and complexity of the discussion.  I think it'd be better with some example plots, but I don't have those handy.  Some day maybe we (here at DataBass) can do a kind of comprehensive article, a "technical guide for laypeople" if you will.

[SME]

2 hours ago, Infrasonic said:

Very little. Of course you can feel some vibration while standing on the "floor" of the riser but it is insignificant compared to what is felt while sitting on the futon.

It very much does. The mattress and any one on it.

Some ULF effect are not unlike this:

More motion when sitting.

 

Wow, great pic!

From what you describe, the mass/inertia of the cone is probably not important.  So I expect the goal would be for as much displacement capability as possible and the amp voltage and power needed to achieve that capability for the given enclosure design.

[Droogne]

1 hour ago, SME said:

As @Infrasonic suggested, you should probably ignore F3, which is largely irrelevant if you have EQ capability.  And you should make having EQ capability a priority if at all possible.   I think there's consensus that it's absolutely necessary in order to compensate for room differences, if nothing else.  Even a lot high value commercial products offer at least rudimentary signal shaping these days.  For DIY, it's probably easiest to buy an amp with EQ capability built-in.

A more important parameter than F3 is the resonance frequency of the sealed system, often called Fb.  This is where the transition between flat(-ish) response and 12 dB/octave roll-off is centered, in the anechoic response without EQ.  The Qtc roughly describes the bandwidth of the transition and indirectly indicates important trade-offs that affect the maximum performance of the system that can be obtained using EQ.

Essentially any one of three things limit the output of a subwoofer system at the low end:

• displacement
• amp voltage
• amp power

Displacement is the amount of air the cones can move.  You can estimate this by multiplying the number of drivers by the cone surface area (Sd) and the maximum excursion (Xmax).  These are usually published in mm^2 and mm, and you can convert the final number to liters by dividing by one million.  For a sealed system, anechoic output is directly related to displacement at a given frequency, and the requirement increases by 12 dB/octave as frequency drops.  In practice, your room will provide gain at the low end, and the displacement requirement doesn't increase as fast down there when used in-room.  If the displacement limit is exceeded, the subs may sound bad, and some drivers can even be damaged.

Amp voltage is the maximum voltage the amp can output.  It is a fundamental limitation of the amp's design.  This information is rarely published in the specs, even though it ought to be.  It will usually be at least as high as the voltage required to achieve the rated power into 8 ohm impedance and typically not much more than that.  This voltage can be estimated using: V = sqrt(P*Z) where Z equals 8 ohm and P equals the power rating into 8 ohm.

Amp power is the maximum power the amp can output, and is often less than what the ax voltage would theoretically deliver, when impedance is less than 8 ohm or so.  Whereas the max voltage is essentially defined precisely by the design, max power can be a bit harder to pin down, despite what the specs may seem to suggest.  Often, an amp will be able to deliver a lot of power for a very short time (burst), but its ability to deliver high power mfor longer durations may be limited by the capability of the power supply and/or the power reserves in its capacitance.  Unfortunately, many amp vendors exaggerate their real world power capabilities in the specs, quoting a "burst" number that is based on max voltage and valid only under very ideal circumstances, which may not even apply at all to low frequencies.  Furthermore, even a very powerful amp, when driven for long enough can overheat and reduce power output because of thermal limitations.  For subwoofer use, the burst numbers tend to be too short term to be of use, but thermal limits are much less likely to be a problem.  The important information is power output on a moderate timescale of maybe a few seconds.  Some people on here and at AVSForum have done some "real world"  testing of true moderate timescale power capabilities, which are likely of interest when shopping for an amp.

The reason I distinguish between amp voltage and amp power is important and has to do with the Qtc.  The Qtc affects both the sensitivity (output at each frequency vs. voltage) and the impedance.  The impedance of a subwoofer is frequency-dependent, and it relates to how much power is consumed for a given voltage.  The voltage going to the sub is essentially the same as the signal fed to the amp, except with some constant (dB) gain.  The actual amount of power consumed (turned into heat in the voice coil) depends on the impedance which varies considerably by frequency, especially around Fb.  The higher the impedance, the less power consumed.   A sealed system always has an impedance peak at Fb, and so a sine wave that Fb will draw and dissipate very little power from the amp.  As such, a sealed system is also extremely efficient (output at each frequency vs. power) right at Fb.

For frequencies far below Fb, a large box volume and lower Qtc will generally give you better voltage sensitivity *and* power efficiency, and the effect of the box volume is rather modest for frequencies far above Fb.  However, for frequencies around Fb, the choice of box volume and resulting Qtc involves a trade-off between sensitivity and efficiency.  In a larger box with lower Qtc, the sensitivity around Fb will be diminished compared to a smaller box and higher Qtc.  This is what you see when you plot simulated "frequency response" curves (which are really just sensitivity curves) in a design simulator.  Lower Qtc systems begin transition from flat to roll-off at a much higher frequency (leading to a higher F3), but the transition region, where roll-off is less than 12 dB/octave,  is also much wider than for a higher Qtc system.  However, this does not tell the whole story.  Even though the "response" (sensitivity) is diminished around Fb in a low Qtc system, the efficiency is actually a lot higher there than in a high Qtc system.  Most design simulators do not plot efficiency directly, but efficiency is important, both for determining whether the amp is capable of driving the system to the desired output and to understand how much power is being dissipated in the coil.

Note that it is always possible to increase the sensitivity of a system by running a second driver in parallel.  When two drivers are run in parallel, the overall impedance drops by half; the efficiency goes up by 3 dB; and the sensitivity goes up by 6 dB.  The caveat, of course, is that the amp must now operate into a lower overall impedance, and double the power will be required to drive both to full displacement.

As such, there is a rather complicated balance to be achieved between each of the three limiting parameters in an optimal design.  To try to simplify things, here's a list of problems that you may encounter if the box is "too small" or "too big":

Too small (high Qtc):

• Output far below Fb limited by max voltage or max power
• Low overall low-end efficiency ==> more power dissipated in the coils ==> more likelihood of power compression or even thermal damage during heavy use

Too large (low Qtc):

• Output around Fb limited by max voltage (but not max power)
• Easier to exceed displacement limits at bottom end ==> more likelihood of damage from over-excursion (also depending on driver choice)

Apart from that, there is no "right" answer as far as what Qtc is best.  It depends on the driver, the amp, and the intended use.   Simulations can be very helpful here.  More sophisticated design programs will plot impedance along with response and excursion for a given input voltage.  Power requirement can be computed for a particular frequency using:  P = V^2/Z.  Using this information, you can estimate how much output (under anechoic or ground-plane conditions) at each frequency you can achieve before hitting one of the aforementioned limits, and which of those limits you'll hit.  And then you can optimize from there.

Or if that's more than you want to be bothered with, you can try copying an existing build using the same drivers and match the enclosure size, accepting whatever compromise the original designer chose.  Plenty of people avoid the complexity of doing their own design and are perfectly satisfied with the results.

Sorry again about the length and complexity of the discussion.  I think it'd be better with some example plots, but I don't have those handy.  Some day maybe we (here at DataBass) can do a kind of comprehensive article, a "technical guide for laypeople" if you will.

I love your lengthy explanations! Yes it's all very complicated, but you explain it very well! I will have to reread a few times to be sure I understand it, but I would love to know more about subject. I love the "science", but it has been a few years since  I had physics at school. Would you recommend winISD? This driver wasn't in their database, which is why I didnt try it out at first. Will now add the Ultimax into it and play with it, and see what it gets me.  

Tried to calculate the Fb and got this results, but will check it out in winISD (if possible).

[SME]

I think what I've used was "WinISD Pro" with some success.  It is a bit quirky and some stuff isn't documented clearly.  For example, the "power input" parameter is not for specifying power so much as voltage, albeit indirectly.  The power you specified is used to compute a voltage: V = sqrt(P*Re) where Re is the minimum resistance of the driver.  If your simulation includes multiple drivers, then IIRC they are treated as in parallel.  So the power you input here to see what output you get at amp's max voltage might be quite a bit higher than the actual power rating of the amp.

Another program that's real popular around here is Hornresp.  Its user interface is a lot uglier and less intuitive, but it is a much more capable program after you learn what all the parameters mean.  It does not accept "power" input and has you input a voltage directly instead, which makes more sense.

In your plots above, note that "frequency response" shown is relative.  The sensitivity would have the same curve shape, albeit shifted up or down to some absolute dB SPL, anticipated at some standard condition such as "1 meter ground plane".  The 1 meter refers to distance from the source.  Ground plane, also called half-space, refers to the theoretical condition in which the driver is flush with an infinitely rigid surface of infinite extent.  The measurements that @Ricci here does by taking the subs out to a large parking lot closely approximate ground plane, though he standardizes to 2 meters instead, which yields numbers 6 dB less than at 1 meter.

I'm not sure what is meant by "power response" above but it appears to give an absolute dB SPL value.  The question is what the conditions are for it.  IIRC, WinISD Pro gives dB SPL at 1 meter in ground plane.

[Droogne]

15 hours ago, SME said:

I think what I've used was "WinISD Pro" with some success.  It is a bit quirky and some stuff isn't documented clearly.  For example, the "power input" parameter is not for specifying power so much as voltage, albeit indirectly.  The power you specified is used to compute a voltage: V = sqrt(P*Re) where Re is the minimum resistance of the driver.  If your simulation includes multiple drivers, then IIRC they are treated as in parallel.  So the power you input here to see what output you get at amp's max voltage might be quite a bit higher than the actual power rating of the amp.

Another program that's real popular around here is Hornresp.  Its user interface is a lot uglier and less intuitive, but it is a much more capable program after you learn what all the parameters mean.  It does not accept "power" input and has you input a voltage directly instead, which makes more sense.

In your plots above, note that "frequency response" shown is relative.  The sensitivity would have the same curve shape, albeit shifted up or down to some absolute dB SPL, anticipated at some standard condition such as "1 meter ground plane".  The 1 meter refers to distance from the source.  Ground plane, also called half-space, refers to the theoretical condition in which the driver is flush with an infinitely rigid surface of infinite extent.  The measurements that @Ricci here does by taking the subs out to a large parking lot closely approximate ground plane, though he standardizes to 2 meters instead, which yields numbers 6 dB less than at 1 meter.

I'm not sure what is meant by "power response" above but it appears to give an absolute dB SPL value.  The question is what the conditions are for it.  IIRC, WinISD Pro gives dB SPL at 1 meter in ground plane.

I have started playing with winISD, but I'm not always sure what to put in the parameters. What do I have to put in the box "Q", is that the calculated Qtc? Or can I just leave it at 2? 

What is a cone excursion I should aim for? My xmax I figure, but how much above that should I allow? 0mm over my xmax @15hz if I want it clean down there?

[Infrasonic]

20 hours ago, SME said:

Wow, great pic!

From what you describe, the mass/inertia of the cone is probably not important.  So I expect the goal would be for as much displacement capability as possible and the amp voltage and power needed to achieve that capability for the given enclosure design.

You're probably right.

Though I never felt ULF effects like that on several other similarly capable nearfield systems. Some even more powerful than mine.

 

[dgage]

By the way, I delivered a pair of my 18” subs the other day and when he was giving me a demo on his suspended floor I told him the Crowson’s gave a nice effect.  The next day, he told me the Crowson’s had been turned off when he gave the demo.  

 

If on a suspended floor, I would go with some sealed subs, which will also give you plenty of tactility.  

 

If you’re on concrete, I’ve done some testing regarding different building techniques for putting wood over concrete to get more tactility.

http://www.avsforum.com/forum/19-dedicated-theater-design-construction/2443450-comparison-wood-platforms-concrete-tactile-bass.html

 

[SME]

5 hours ago, Droogne said:

I have started playing with winISD, but I'm not always sure what to put in the parameters. What do I have to put in the box "Q", is that the calculated Qtc? Or can I just leave it at 2? 

What is a cone excursion I should aim for? My xmax I figure, but how much above that should I allow? 0mm over my xmax @15hz if I want it clean down there?

I don't know about "Q" there.  Like I said, I think I used "WinISD Pro" instead.  IIRC, that was recommended by the community over the other version.

As far as cone excursion, obviously the amount depends on how much voltage the amp is giving it.  Xmax is a rough guideline for where distoriton will begin to rise rapidly.  In most cases, Xmax is a bit of an optimistic figure and distortion begins to rise a lot before you actually hit it.  Though at the same time, the in-room response can suppress some of that distortion as well.  A key benefit of having extra available displacement, other than greater max output, is less distortion at moderately output levels.

At the same time, excursion is much higher for low frequency content, and having extra power (above that which is necessary to achieve Xmax) is often considered desirable to provide a reserve for reproduction of high frequency content that occurs simultaneous to low frequency content.

Xmech is also important parameter.  That is the maximum excursion that the manufacture deems to be safe for the driver.  You probably want to avoid exceeding that in your design unless you intend to use some kind of electronic limiter or trust yourself to be careful with the volume control.  (Not necessarily a good idea, especially if you or your friends like to drink, heheh.)  A lot depends on the driver here too.  A few drivers like the infamous TC Sound LMS-Ultra 18" are notoriously unforgiving about over excursion, and have been known to go from "sounding real nice" to permanently damaged with only a slight increase in output.  Other drivers, especially pro-style drivers, are a lot more abuse tolerant and provide ample warning that you are pushing them too hard.  Typically these drivers compress a lot before they reach their mechanical limits and may require quite a bit more voltage to reach Xmech than a WinISD simulation (which assumes no compression) would suggest.

Admittedly, I don't know much about the overload behavior of the Ultimax UM18-22.  Maybe someone else can comment.

3 hours ago, Infrasonic said:

You're probably right.

Though I never felt ULF effects like that on several other similarly capable nearfield systems. Some even more powerful than mine.

 

Very interesting.  Maybe it's your futon?  Now we know the secret.    I am kind of serious here.

Though a lot could also depend on the response of the driver after EQ.  I imagine that tactile sensation may depend more on the anechoic than in-room response of the driver, which means that a room with a lot of gain that doesn't need as much boost for a flat in-room response may have a diminished anechoic response and less tactile effect.  Though you are in a pretty small room, so I'd expect your room gain to be pretty remarkably high, and you also have plenty of other subs in the room for ULF SPL response too.

1 hour ago, dgage said:

By the way, I delivered a pair of my 18” subs the other day and when he was giving me a demo on his suspended floor I told him the Crowson’s gave a nice effect.  The next day, he told me the Crowson’s had been turned off when he gave the demo.  

 

If on a suspended floor, I would go with some sealed subs, which will also give you plenty of tactility.  

 

If you’re on concrete, I’ve done some testing regarding different building techniques for putting wood over concrete to get more tactility.

http://www.avsforum.com/forum/19-dedicated-theater-design-construction/2443450-comparison-wood-platforms-concrete-tactile-bass.html

 

I think we can agree that concrete is a real downer for ULF tactile sensation, but unfortunately, a suspended floor does not seem to be a guarantee of tactile response either.  That's what I had to discover for myself.  I do get a fair amount of shake in the low 20s, at around 16 Hz, and at 10-12 Hz, but below 10 Hz seems to be totally inert.  Hence, Crowsons are in my future.

[Infrasonic]

On 10/26/2017 at 12:53 PM, SME said:

 

Very interesting.  Maybe it's your futon?  Now we know the secret.   

Heheh. Yeah, maybe!

Quote

I am kind of serious here.

Me too. I don't understand all the things that are going on.

Quote

Though a lot could also depend on the response of the driver after EQ.  I imagine that tactile sensation may depend more on the anechoic than in-room response of the driver, which means that a room with a lot of gain that doesn't need as much boost for a flat in-room response may have a diminished anechoic response and less tactile effect.  Though you are in a pretty small room, so I'd expect your room gain to be pretty remarkably high, and you also have plenty of other subs in the room for ULF SPL response too.

Thanks. While I do have a lot of woofer power in my room. The single dual 18 riser swamps the output of the rest of the subs. At least in regards to overall intensity and tactile-ness.

I doubt "room gain" has any impact on the tactile-ness of the riser. I think it would be just as tactile outside in a field.

EQ does have an effect, yes. I didn't have to do much at all. The "response" (going by feeling) was always adequate, as far as I could tell. Got really into it when I got wrapped up in the Vibsensor testing. Months and months spent adjusting this and that. Times I would be happy with the results, other times I hated it. Tried running it off completely for a while, then I was back and re-adjusted more. Took a while to get it where I like it now. There isn't so much EQ work as there is just getting the levels right. I have plenty of capabilities left on the table but I like it how I have it set now simply supplementing the rest of the HT system rather than being so saturated by it it overtook the rest of the HT experience.

Got to this happy point where I don't feel the need to adjust anything but the volume (and maybe tweak the bass/treble tone here or there) and I like this spot.

Quote

I think we can agree that concrete is a real downer for ULF tactile sensation, but unfortunately, a suspended floor does not seem to be a guarantee of tactile response either.  That's what I had to discover for myself.  I do get a fair amount of shake in the low 20s, at around 16 Hz, and at 10-12 Hz, but below 10 Hz seems to be totally inert.  Hence, Crowsons are in my future.

That's what I thought until I built this riser.

Now I know there is a dagger that can pierce the heart of the evil dragon we call the 'concrete slab'. It's not the only countermeasure either as you are aware.

[SME]

25 minutes ago, Infrasonic said:

I doubt "room gain" has any impact on the tactile-ness of the riser. I think it would be just as tactile outside in a field.

Well, my thinking here is that if one was using the near-field riser exclusively, without other subs and if the response was calibrated for flat in-room response, then the room gain would affect how much ULF woofer motion there would be in the ULF.  More room gain means less need for ULF boost, meaning less woofer motion, and presumably less tactile feel if the feel has more to do with local woofer motion than in-room SPL.

30 minutes ago, Infrasonic said:

EQ does have an effect, yes. I didn't have to do much at all. The "response" (going by feeling) was always adequate, as far as I could tell. Got really into it when I got wrapped up in the Vibsensor testing. Months and months spent adjusting this and that. Times I would be happy with the results, other times I hated it. Tried running it off completely for a while, then I was back and re-adjusted more. Took a while to get it where I like it now. There isn't so much EQ work as there is just getting the levels right. I have plenty of capabilities left on the table but I like it how I have it set now simply supplementing the rest of the HT system rather than being so saturated by it it overtook the rest of the HT experience.

Out of curiosity, what kind of EQ did you use?  Is there an LPF on them?  How high?  I can see levels being critical as you are trying to get a good match so the tactile and sound balance and blend well.

[Droogne]

17 hours ago, Infrasonic said:

 

EQ does have an effect, yes. I didn't have to do much at all. The "response" (going by feeling) was always adequate, as far as I could tell. Got really into it when I got wrapped up in the Vibsensor testing. Months and months spent adjusting this and that. Times I would be happy with the results, other times I hated it. Tried running it off completely for a while, then I was back and re-adjusted more. Took a while to get it where I like it now. There isn't so much EQ work as there is just getting the levels right. I have plenty of capabilities left on the table but I like it how I have it set now simply supplementing the rest of the HT system rather than being so saturated by it it overtook the rest of the HT experience.

I'm gonna test some more in winISD, but I doubt I will ever know when I hit the sweet spot  would I be safe if I just build the riser to the measurements I need for my couch/place and buy 1x UM18-22? Then try it out and play with the EQ? That way I'll have real time results. 

 

[SME]

13 hours ago, Droogne said:

I'm gonna test some more in winISD, but I doubt I will ever know when I hit the sweet spot  would I be safe if I just build the riser to the measurements I need for my couch/place and buy 1x UM18-22? Then try it out and play with the EQ? That way I'll have real time results.

The sweet spot really depends, and the room gain response matters too.  FWIW, the DataBass testing was done in a 4 cuft enclosure, so 20 cuft will definitely be generous for one driver.  It could probably easily handle 2-4.  Three is an odd number that may not work optimally with the amp you have.  What kind of amp do you plan to use?  That is quite important.

If you do try only one driver in a large enclosure, keep in mind that you may need to modify or rebuild the enclosure to get what you want.  And be careful not to overdrive it with very low frequencies.  The DataBass review suggests that it is fairly robust, and should at least make some ugly sounds before the driver is in any serious danger.

Another option is to build a sealed test box for a single driver to do in-room measurements and then decide on how many drivers and how much volume to put in the riser for the performance you want.

[Droogne]

3 hours ago, SME said:

The sweet spot really depends, and the room gain response matters too.  FWIW, the DataBass testing was done in a 4 cuft enclosure, so 20 cuft will definitely be generous for one driver.  It could probably easily handle 2-4.  Three is an odd number that may not work optimally with the amp you have.  What kind of amp do you plan to use?  That is quite important.

If you do try only one driver in a large enclosure, keep in mind that you may need to modify or rebuild the enclosure to get what you want.  And be careful not to overdrive it with very low frequencies.  The DataBass review suggests that it is fairly robust, and should at least make some ugly sounds before the driver is in any serious danger.

Another option is to build a sealed test box for a single driver to do in-room measurements and then decide on how many drivers and how much volume to put in the riser for the performance you want.

 3 is an odd number, but as I havent decided on amps yet I could still go for 2x woofers in parallel and a third driver by another amp. I will probably just stick with 2 woofers though. I also tried working with winISD pro but I dont seem to be able to add the info for the Ultimax... If I'm not planning on using it to extreme SPL levels the way to large enclosure could work right? The amp I'll be using at the moment only has 530watt @4ohm (it's a PSA2700) so I doubt I'll overdrive it. Could I impose on you?  What enclosure size would be safest to try out? Could you have a look in winISD or the likes? And if I'm talking about the sweetspot in winISD, I'm talking about the best calculations you can do without knowing the exact influence of the room. 

[Droogne]

I think, if I calculated correctly, I can get a 120db flat response from 15-35hz with EQ. It would not exceed max. excursion in this range, and would only take 27 watt power. This would be at only 20cm (less than a feet). As discussed earlier, room response does not have as much influence as it would have on a normal sub as it fires directly on me from a very small distance. Persons sitting next to me would get a much much lower SPL. Only 104db. If I use 2 drivers this would get up to 126db and 110db in this range beneath excursion (with 70 watts of power).

[SME]

On 10/29/2017 at 5:21 AM, Droogne said:

 3 is an odd number, but as I havent decided on amps yet I could still go for 2x woofers in parallel and a third driver by another amp. I will probably just stick with 2 woofers though. I also tried working with winISD pro but I dont seem to be able to add the info for the Ultimax... If I'm not planning on using it to extreme SPL levels the way to large enclosure could work right? The amp I'll be using at the moment only has 530watt @4ohm (it's a PSA2700) so I doubt I'll overdrive it. Could I impose on you?  What enclosure size would be safest to try out? Could you have a look in winISD or the likes? And if I'm talking about the sweetspot in winISD, I'm talking about the best calculations you can do without knowing the exact influence of the room. 

Sorry.  The computer I used to run WinISD Pro and Hornresp is broken at the moment.  It's kind of a long running TODO for me to fix it, and it probably won't happen for a while.

I don't know whether 530W is enough to overdrive it in a large box, but I wouldn't worry much.  If you hear any ugly sounds, then back off on the volume.  The main drawback to starting with the very large enclosure is that it may be very difficult to modify it to achieve a smaller volume, and rebuilding it may be a big pain.  Keep in mind that you want the sealed compartment to be solidly built, pretty much air-tight, braced well.

Yes, 3 is an odd number.  If you try to run the third woofer with a separate amp, it may not get the same voltage as the others, and this could lead to some weird side-effects if they are all installed in the same sealed chamber.  I think it'd be better to give the third its own chamber in that case.   And anyway, you won't get much extra output by adding a third woofer.  Certainly, it won't be a particularly good value if you have to buy an additional amp just for that driver.  It'd be much better to add 2 more if you want more than 2.

On 10/29/2017 at 6:19 AM, Droogne said:

I think, if I calculated correctly, I can get a 120db flat response from 15-35hz with EQ. It would not exceed max. excursion in this range, and would only take 27 watt power. This would be at only 20cm (less than a feet). As discussed earlier, room response does not have as much influence as it would have on a normal sub as it fires directly on me from a very small distance. Persons sitting next to me would get a much much lower SPL. Only 104db. If I use 2 drivers this would get up to 126db and 110db in this range beneath excursion (with 70 watts of power).

Calculations for 20 cm from the driver are completely pointless.  For a driver inside a riser, your head is going to be 1 meter away at the very least, and there's a good chance that room gain effects will still influence the ULF response at that distance.  I've seen room gain effects in measurements at like 12".  Note that this is a good thing because getting decent ULF response requires obscene amounts of displacement without the help of room gain.

[Droogne]

1 hour ago, SME said:

Sorry.  The computer I used to run WinISD Pro and Hornresp is broken at the moment.  It's kind of a long running TODO for me to fix it, and it probably won't happen for a while.

I don't know whether 530W is enough to overdrive it in a large box, but I wouldn't worry much.  If you hear any ugly sounds, then back off on the volume.  The main drawback to starting with the very large enclosure is that it may be very difficult to modify it to achieve a smaller volume, and rebuilding it may be a big pain.  Keep in mind that you want the sealed compartment to be solidly built, pretty much air-tight, braced well.

Yes, 3 is an odd number.  If you try to run the third woofer with a separate amp, it may not get the same voltage as the others, and this could lead to some weird side-effects if they are all installed in the same sealed chamber.  I think it'd be better to give the third its own chamber in that case.   And anyway, you won't get much extra output by adding a third woofer.  Certainly, it won't be a particularly good value if you have to buy an additional amp just for that driver.  It'd be much better to add 2 more if you want more than 2.

Calculations for 20 cm from the driver are completely pointless.  For a driver inside a riser, your head is going to be 1 meter away at the very least, and there's a good chance that room gain effects will still influence the ULF response at that distance.  I've seen room gain effects in measurements at like 12".  Note that this is a good thing because getting decent ULF response requires obscene amounts of displacement without the help of room gain.

As luck would it, I found an atelier in my city for DIY projects, and one of them is a speaker builder! Will be talking about my options with him, but you are right.. modiying the enclosure will be hard once I build it. I can place the single 18" in a place similar to where a second would be placed, and also place the braces so I leave a space open for the second one. That way I can add a second with having to change the internal.  Addionaly I could make the bracing in way that I can split the internal volume in 2 after removing the top plate. 

But good to know about the overdriving part! I will let you know what my local DIY contacts tell me

[SME]

Another thing you can do is test the driver using the amp in free air to get an idea of how it behaves at high excursion.  You can be assured that the excursion won't be any worse when you apply the same voltage to it in a sealed box of any size.

Be careful not to overheat the coil by driving it with a lot of power for more than a few seconds.  Even 500W can heat up and fry a voice coil if it's something high duty cycle like sine waves.  Music and movie effects are rarely anywhere near as thermally demanding.

Good luck on your project and keep us posted.

[Droogne]

On 31-10-2017 at 10:11 AM, SME said:

Another thing you can do is test the driver using the amp in free air to get an idea of how it behaves at high excursion.  You can be assured that the excursion won't be any worse when you apply the same voltage to it in a sealed box of any size.

Be careful not to overheat the coil by driving it with a lot of power for more than a few seconds.  Even 500W can heat up and fry a voice coil if it's something high duty cycle like sine waves.  Music and movie effects are rarely anywhere near as thermally demanding.

Good luck on your project and keep us posted.

As always, love your input and tips! Some extra info: as I'm a person who always seems tot go "too" hard, I have also started a DIY 3-way active speaker build (La Scala with a PH2380 Horn). This is ofcourse draining my resources, but I only started this second project because I sold my Klipsch Fortes II for a really good sum. This means I have the means to do both projects at once. Problem: time. Also: I'm completely new to DIY I will gain some experience by building the the 18" PA horn for which I have a building kit and an extensieve guide for. The LaScala I'm having build, the riser will be completely me. Big advantage of the LaScala project, it will involve a lot of reading in to measuring roomresponse (for which I will buy a special mic, the UMIK-1) with REW, and how to translate this REW into the correct active crossover settings. This will obviously give me some experience, and really helpfull devices, to configure the NF subriser. Will be putting the riser project on hold for few weeks till I'm really sure what height would be optimal. That because I might have a found a way to lower my tv when building a third LaScala to match the LaScala fronts. Will still build a riser in that case, but it will need to be lower. I know the riser should have an inherent minimum height due to the building depth of the woofer, but I would try to find a way around that by putting the woofer in a protruding part of the cabin. In that case the internal volume would be smaller. That leads me to a question. The UM18 sealed design, which is featured in the DIY list on this forum, lists a specific volume, why this volume? Optimal for this speaker, or just because it is the smallest possible external volume? Or are there no specific reason for the choices/is it hard to pinpoint the exact reason?

Also, really thinking about building the riser out of 2 pieces. This way it is a lot easier to move, then they can serve as a pair corner subs if I want to try another setup and it would be a lot easier to build in 2 parts (then I can spread the costs). Good idea soundwise?

[SME]

The particular sealed box volume used to test the UM18 on DataBass arises because that's the sealed test box that Ricci uses to test most 18" drivers.  He doesn't build a separate box to test each driver.  That'd be way too much effort.

Building the riser out of two pieces is fine.  Just make certain each individual piece is sealed.  Sound-wise it won't matter much except for the fact that you'll be giving the drivers ever so slightly less volume than if you made a single piece with combined volume.

[Infrasonic]

4 hours ago, Droogne said:

As always, love your input and tips! Some extra info: as I'm a person who always seems tot go "too" hard, I have also started a DIY 3-way active speaker build (La Scala with a PH2380 Horn). This is ofcourse draining my resources, but I only started this second project because I sold my Klipsch Fortes II for a really good sum. This means I have the means to do both projects at once. Problem: time. Also: I'm completely new to DIY I will gain some experience by building the the 18" PA horn for which I have a building kit and an extensieve guide for. The LaScala I'm having build, the riser will be completely me. Big advantage of the LaScala project, it will involve a lot of reading in to measuring roomresponse (for which I will buy a special mic, the UMIK-1) with REW, and how to translate this REW into the correct active crossover settings. This will obviously give me some experience, and really helpfull devices, to configure the NF subriser. Will be putting the riser project on hold for few weeks till I'm really sure what height would be optimal. That because I might have a found a way to lower my tv when building a third LaScala to match the LaScala fronts. Will still build a riser in that case, but it will need to be lower. I know the riser should have an inherent minimum height due to the building depth of the woofer, but I would try to find a way around that by putting the woofer in a protruding part of the cabin. In that case the internal volume would be smaller. That leads me to a question. The UM18 sealed design, which is featured in the DIY list on this forum, lists a specific volume, why this volume? Optimal for this speaker, or just because it is the smallest possible external volume? Or are there no specific reason for the choices/is it hard to pinpoint the exact reason?

I knew there was a reason I liked you.

4 hours ago, Droogne said:

Also, really thinking about building the riser out of 2 pieces. This way it is a lot easier to move, then they can serve as a pair corner subs if I want to try another setup and it would be a lot easier to build in 2 parts (then I can spread the costs). Good idea soundwise?

Ehhh.... soundwise, wah? It's a riser.

Just make sure to uhh....do whatever SME says with the "sealed" and all that stuff.

[Droogne]

11 minutes ago, SME said:

The particular sealed box volume used to test the UM18 on DataBass arises because that's the sealed test box that Ricci uses to test most 18" drivers.  He doesn't build a separate box to test each driver.  That'd be way too much effort.

Building the riser out of two pieces is fine.  Just make certain each individual piece is sealed.  Sound-wise it won't matter much except for the fact that you'll be giving the drivers ever so slightly less volume than if you made a single piece with combined volume.

Ok, that makes a lot of sense! I already saw a lot of those sealed boxes used the same volume. I think it will be a lot better to do it in 2 seperates, lots of advantages space and moving wise. It could also be that I have enough with 1 sub, as I'm gonna be the only one investing in the hometheatre so putting money in something to just give the person visiting more tactile is a bit unnecesary ( they would already be blown away by the bass I have from my Chorusses, let alone in combination with the 18" PA sub). Will let you know if I start building it! 

[Droogne]

I think I realised  it is just better to go with it  I think if I separate the riser I can try out a lot of things with it, start cheap and only build 1 side of the platform and use a concocted second half (a cheap spare pallet I have laying around). Once I have this sealed sub I can also put it in some other positions  in my room to try out some general room effects etc, as it is a far more moveable size (would be kinda hard to just "put" a 8x4x1 foot platform in a corner to hear how it sounds). Once I have the first riser build (still gotta figure out the bracing though) I can start EQing the hell out of  it with REW software and UMIK-1. The box of the riser might not be ideal, but oh well. I doubt any DIY project like this can be perfect from the start. If I stay realistic and use the EQ correctly I'll be undoubtly happy with the results. And if I'm not, then I'll probably know why, which will put me on the way to perfect it the next time  to above and beyond!

[Droogne]

@Infrasonic @SME

I'll be moving next week (finally!) so I'll have a better idea about the final height of the couch. Recently I learned about the super inexpensive Stereo Integrity 18" subs which were less expensive to ship from the us then buy the Ultimax locally, sadly the SI subs were discontinued not long ago.. I'll keep you posted when I ever start the build or make a decision! Till then I'll keep looking for a cheaper version of the Ultimax.