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

What design?  

3 members have voted

  1. 1. What design would fit the best with this driver and (fixed) enclosure volume?

    • Single driver, sealed
      0
    • Doubledrivers, sealed
      1
    • Triple drivers, sealed
      0
    • Single driver, ported
      0
    • Double drivers, ported
      2
    • Single driver with Passive Radiators
      0


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Hey

I'm planning on making a couch riser, and now I got the crazy idea to use it as a nearfield subwoofer enclosure. Although I could change the internal volume if truely necessary, the external is fixed. That is why I was wondering, what would the best possible enclosure design for this kind of internal volume? What has the most potential in the lowest frequencies? I will cross over @ 35hz so all output above that is irrelevant in this design question. Extra potential in the sub 10hz range is a plus, but less important.

I know some of the designs in the poll cost a lot  more than the others, but I'm wondering about the potential of the enclosure. I will ofcourse go for the easiest and cheapest design choice if the difference is negligible (or if the difference is only relevantly present @ + 115-120 db). 

Love to hear what you guys all think!

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I run a subwoofer riser with dual 18's. The internal volume is approximately 12cuft or so, sealed. My 18's are similar to the Ultimax18's. I use the subwoofer riser to augment the ultra low frequencies although I can and have used it "full range" and in the full bandwidth of the LFE channel.

 

What exactly are you going for? There is a lot of loaded questions in your post.

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What kind of sub capability do you already have?  How big is your room including adjoining areas?

For now, my vote is for an option that's not listed:

Crowson tactile transducers; either under the couch or under the riser.  Assuming the riser only has one normal size couch, two or four ought to do the trick.  That ought to get you what you want in the tactile domain.  Then, if you want more sub capability, build some big ported cabinets to put in the corner(s), tuned to 12-15 Hz.  I think that'll be the best of both worlds.

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10 hours ago, Infrasonic said:

I run a subwoofer riser with dual 18's. The internal volume is approximately 12cuft or so, sealed. My 18's are similar to the Ultimax18's. I use the subwoofer riser to augment the ultra low frequencies although I can and have used it "full range" and in the full bandwidth of the LFE channel.

 

What exactly are you going for? There is a lot of loaded questions in your post.

Hey man! You are exactly the man I need! I got the idea from your AVS HT build post ! (and you have also been quoted again in the post I started over there about this platform).

I know design choices are never simple, that's why I tried to simplify by already giving a specific driver. As for what I'm looking for.. Well I tried to be as non specific, but I missed the ball I think. Ill explain my situation. 

I have an 18" hornloaded PA sub which can (without EQ) reach as low as 35hz (105db SPL, 1000W RMS), I was wanting to push it lower (which the designer told me could get me down to 25-30 hz), but that was not a great idea I learned. I then got the idea to fill this range with another Horn loaded sub. And although I'm still not really against it, the required measurements would not allow me to put it in my room. 

I then saw your post and thought, that is exactly what I need! I was already thinking about DIYing a platform with some construction wood, but your platform gave me an opportunity. I would not need to use any extra space to put a new sub, and because of the required size the enclosure would have an enormous potential, size wize. 

This is why I got the idea to fill up the lower range with a different sub design, and cross it over at 35hz. So what am I looking for precisely? Something to fill up the (audible) range below 35hz, and I was really hoping to go for some useful output below 20hz, and possibly below 15hz. Listening levels should not go extremely high (110-115db is OK), but I would like some low distortion levels down to my wanted range. Does this sub 20hz need to be produced by a sub? No. I'm more than happy to use transducers (I contacted a nearby seller for a price check on the Crowson transducers). I would still need a sub to fill up the 20-35hz range.  

Am I sold to the nearfield design? No. I"m open for all suggestions! The fact that I would be able to use the riser space as an enclosure is a huge plus though. A huge plus, but not a absolute requirement. I do have spare space or other placement options. I could make one of those coffee table subs for example. I also think I can manage some corner placed subs, although I was keeping those for a possible Klipschorn pair.  Other placements (between the LCR for example) are also possible. The nearfield enclosure just looks like a terribly exciting idea! It also looks pretty awesome.

But I agree.. while writing this I realise that there are better options. I found a B&C 21SW152 second hand today (for 300 euro) which could set me on a path for a riser with appropriate transducers and the B&C to take over the 20-35hz range in a sealed box (http://data-bass.com/data?page=system&id=72&mset=78). I'm of course open to other suggestions, or the best way to still use my original riser plan.

Some extra info: 

Room volume: 84 square meter (ca 30 000 cuft). Room plan included as attachment (adjacent kitchen not show, but considered in the room volume. Coin is where television will be).

Rest of my setup (or what I'm planning it to be): Klipsch LaScala LCR, 4x Heresy II surrounds and 4x Klipsch Heresy II hight channels. 

 

 

 

 

 

 

20986464_1733258510051697_2014791738_n.png

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7 hours ago, SME said:

What kind of sub capability do you already have?  How big is your room including adjoining areas?

For now, my vote is for an option that's not listed:

Crowson tactile transducers; either under the couch or under the riser.  Assuming the riser only has one normal size couch, two or four ought to do the trick.  That ought to get you what you want in the tactile domain.  Then, if you want more sub capability, build some big ported cabinets to put in the corner(s), tuned to 12-15 Hz.  I think that'll be the best of both worlds.

The crowson transducers do look expensive.. what would you say about the butkicker (minis)? 

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Crowsons have some nice and natural feeling effects.  Buttkicker, at least the ones I’ve heard, are not as nuanced and so are quite noticeable in their effects.  For me personally it would be Crowsons or nothing based on my limited listening of a few Buttkicker systems vs the single Crowson system I heard.

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3 minutes ago, dgage said:

Crowsons have some nice and natural feeling effects.  Buttkicker, at least the ones I’ve heard, are not as nuanced and so are quite noticeable in their effects.  For me personally it would be Crowsons or nothing based on my limited listening of a few Buttkicker systems vs the single Crowson system I heard.

I'm still waiting on the price from my local store so I cant really compare them yet. But when using a platform coupled buttkicker, would that not help in giving a more nuanced feeling? In any case, the buttkicker mini is only 120 euros and would be a nice temporary solution. If I do decide to upgrade to the Crowsons I'd move the buttkicker mini to my office chair. 

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After experiencing A LOT of HT systems with either: nearfield subwoofer (of various capability), Buttkickers, Crowsons... and combinations of such, they all have their pro's and con's.  If you need those listed, I can do so but... I don't think you came in here looking for a run down on what is the "best tactile transducer". There really is no "this is bad, go with this instead" approach.

Going from your description of your system and what you want, I'd recommend a simple sealed subwoofer-based riser. It sounds like that was your original plan. Might as well act on it.

Transducers are good but different. It should be up to decide where you want to take this.

But....if you want my opinion, I have not had such a revelation of tactile bass or sensation of that elusive ULF "feel" since adding this riser. After much time with it, I found that it was so powerful that I had to reign it in a bit and chose to for it to only supplement my main subwoofer system (of which the dual 18" riser would easily out-gun, sad to say) for ULF effects only. You are saying you are quite happy with the 30hz and up performance, I can't think of a better solution for you than to copy what I did. Of course there are alternatives but going off what you have posted, this would be my first recommendation.

For context (important)... I chose to build a nearfield subwoofer riser for these reasons: test the waters myself of the "nearfield sub" that was heavily trending, I also had two spare 18's that I wanted to use for something, I had redesigned my HT room and had designed it around needing a riser anyway. I also had an extra amp. Just had to build a riser. Why not? Glad I did.

 

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10 minutes ago, Infrasonic said:

After experiencing A LOT of HT systems with either: nearfield subwoofer (of various capability), Buttkickers, Crowsons... and combinations of such, they all have their pro's and con's.  If you need those listed, I can do so but... I don't think you came in here looking for a run down on what is the "best tactile transducer". There really is no "this is bad, go with this instead" approach.

Going from your description of your system and what you want, I'd recommend a simple sealed subwoofer-based riser. It sounds like that was your original plan. Might as well act on it.

Transducers are good but different. It should be up to decide where you want to take this.

But....if you want my opinion, I have not had such a revelation of tactile bass or sensation of that elusive ULF "feel" since adding this riser. After much time with it, I found that it was so powerful that I had to reign it in a bit and chose to for it to only supplement my main subwoofer system (of which the dual 18" riser would easily out-gun, sad to say) for ULF effects only. You are saying you are quite happy with the 30hz and up performance, I can't think of a better solution for you than to copy what I did. Of course there are alternatives but going off what you have posted, this would be my first recommendation.

For context (important)... I chose to build a nearfield subwoofer riser for these reasons: test the waters myself of the "nearfield sub" that was heavily trending, I also had two spare 18's that I wanted to use for something, I had redesigned my HT room and had designed it around needing a riser anyway. I also had an extra amp. Just had to build a riser. Why not? Glad I did.

 

 

Would you happen to know if the fact that there is a couch above the woofers has any relevant influence on the perceived sound produced by the nearfield sub? Fact that I would only use it for 35hz and lower leads me to think that it doesnt, but I cant be sure enough ;) If I'm planning to not add any subs in the (near) future, would you recommend the dual sealed setup, or would a single sealed also work? Would the double give a better response for the whole couch (as in, that you wouldnt be able to localise it beneat you independent of where you are seated). Again, because of the non directionality of low frequencies I'm guessing it doesnt, but maybe it does because of the small distance. If you recommend single, would the B&C 21SW152 sealed work? Or is the Ultimax because of it's higher Xmax better suited (22 vs 14mm)? And what if I do decide on a driver (amount), do I stay with this enormous enclosure of 24cuft, or do I make it smaller so it fits the optimum internal volume? 

PS, the only way I will ever find out the best tactile LFE is by trying ;) I already have an ultra cheap Dayton Audio transducer which served me well, and I'm gonna keep using it. Main reason: it's silent. I do have neighbours, so that means that the transducers will make it less painful to pull the plug on the subwoofers in the evening. Is it a bad idea to put the transducer on the same platform as the nearfield sub? Will the vibration distort the sub? 

 

Again, thank you!

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It's hard to say for sure but I can say that I like the sensation (with ULF) more with my subwoofer riser than any other nearfield sub while firing into the back of a chair. It should also be mentioned that most people's systems I've experienced (with TT's) have had 'theater style' seats or a Laz-E-Boy type chair. My seating is a futon couch that actually uses a full bed mattress as the cushion. This of course will affect how the transfer for bass will feel from one room/system to another. Not to forget that settings for how these are configured to the system will vary wildly. These alone can affect the whole experience and said observations.

For a long time I didn't care much for the Buttkicker transducer system. Any version of it and I've tried them all (or most). Poor configuration can really hurt the experience. It wasn't until I got to feel more of other people's systems that I could see the light. Even D-Box can be poor but on paper you'd think it would provide an awesome, immersive movie experience but on the contrary, in real life, it is anything but immersive. Takes you right out of the movie. Anyway, my point is that just configuring things right, you can make a good "tactile" bass system out of any type of transducer or active driver(s).

How many drivers should be up to how you plan on seating. Is this for a single seat? Love seat? Couch? Sectional? One driver per person works well and is what most people do. I happened to have two extra 18's and two 18's fit underneath my futon couch like nobody's business so .... *profit!* It sorta sounded like you were on a budget so I guess just plan accordingly.

Between those two drivers, I'd choose the 18. Simply because it is meant to be a home theater subwoofer and has the most excursion (between the two) which may be a key ingredient for such a system, I think. I don't have any scientific evidence to back it up. Though I feel that I get the most "sensation" from a system that has higher inertia. The B&C driver is wicked good but it would not be my first choice for a '30hz and down' system or tactile transducer. It wouldn't be the worst choice by any means! But optimal? I don't think so. Plus, it's pretty $$$$$.

Size should relate to an optimal volume for the driver(s). In my particular case, I just wanted a riser to fit the width of the futon (I have a very narrow room) with some foot room. It pretty much ends at the back of the futon. It is quite compact. I did have a certain height I was aiming for and considered that in the full dimensions of the thing. Ended up with a volume of space that happened to be ideal for my Sound Splinter RLp18 drivers. Made no modifications to the design besides the basic dimensions. They all fell within the range I needed. Could I have built something bigger? Well, not really. Would it have impacted the performance if it were bigger? Maybe. Depends on many things. I don't see any reason to build it bigger than it needs to be. How big it needs to be depends on the seating layout, driver amount and type, etc. Either way, it is always a good idea to match the right driver with the appropriate airspace. Even when used as a riser/nearfield/tactile system.

 

Yes, of course a large benefit to traditional tactile transducers is their silent operation.

 

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5 hours ago, dgage said:

Crowsons have some nice and natural feeling effects.  Buttkicker, at least the ones I’ve heard, are not as nuanced and so are quite noticeable in their effects.  For me personally it would be Crowsons or nothing based on my limited listening of a few Buttkicker systems vs the single Crowson system I heard.

Of tactile transducers, I mostly agree with this post. Crowson's are by far the most "natural" feeling transducer system I've ever experienced. Best way I could describe them is that they felt like sitting on a subwoofer (in a good way). BK's tend to be a big heavy-handed in their effect, mostly. I can only think of one or two times I thought the BK integration was seamless enough that I wouldn't have guessed that they were BK's. So I think with the right setup BK's can be alright too. They are certainly cheaper than Crowson's.

Another cool thing about Crowson's that justify's their higher price is that they are also the smallest (yet very effective) of the bunch. A full size BK isn't a huge thing but it's large enough to notice or not fit at all under certain kinds of seating. Crowson's slip right under the feet of essentially any type of seat or chair. Very versatile that way.

 

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38 minutes ago, Infrasonic said:

It's hard to say for sure but I can say that I like the sensation (with ULF) more with my subwoofer riser than any other nearfield sub while firing into the back of a chair. It should also be mentioned that most people's systems I've experienced (with TT's) have had 'theater style' seats or a Laz-E-Boy type chair. My seating is a futon couch that actually uses a full bed mattress as the cushion. This of course will affect how the transfer for bass will feel from one room/system to another. Not to forget that settings for how these are configured to the system will vary wildly. These alone can affect the whole experience and said observations.

For a long time I didn't care much for the Buttkicker transducer system. Any version of it and I've tried them all (or most). Poor configuration can really hurt the experience. It wasn't until I got to feel more of other people's systems that I could see the light. Even D-Box can be poor but on paper you'd think it would provide an awesome, immersive movie experience but on the contrary, in real life, it is anything but immersive. Takes you right out of the movie. Anyway, my point is that just configuring things right, you can make a good "tactile" bass system out of any type of transducer or active driver(s).

How many drivers should be up to how you plan on seating. Is this for a single seat? Love seat? Couch? Sectional? One driver per person works well and is what most people do. I happened to have two extra 18's and two 18's fit underneath my futon couch like nobody's business so .... *profit!* It sorta sounded like you were on a budget so I guess just plan accordingly.

Between those two drivers, I'd choose the 18. Simply because it is meant to be a home theater subwoofer and has the most excursion (between the two) which may be a key ingredient for such a system, I think. I don't have any scientific evidence to back it up. Though I feel that I get the most "sensation" from a system that has higher inertia. The B&C driver is wicked good but it would not be my first choice for a '30hz and down' system or tactile transducer. It wouldn't be the worst choice by any means! But optimal? I don't think so. Plus, it's pretty $$$$$.

Size should relate to an optimal volume for the driver(s). In my particular case, I just wanted a riser to fit the width of the futon (I have a very narrow room) with some foot room. It pretty much ends at the back of the futon. It is quite compact. I did have a certain height I was aiming for and considered that in the full dimensions of the thing. Ended up with a volume of space that happened to be ideal for my Sound Splinter RLp18 drivers. Made no modifications to the design besides the basic dimensions. They all fell within the range I needed. Could I have built something bigger? Well, not really. Would it have impacted the performance if it were bigger? Maybe. Depends on many things. I don't see any reason to build it bigger than it needs to be. How big it needs to be depends on the seating layout, driver amount and type, etc. Either way, it is always a good idea to match the right driver with the appropriate airspace. Even when used as a riser/nearfield/tactile system.

 

Yes, of course a large benefit to traditional tactile transducers is their silent operation.

Well to say I'm on a budget.. that is true and it's not. It really depends on how much I would gain by upgrading. I'll have to figure out the enclosure thing though.. When I combined the info from their site (lowest single sealed F3 @7cuft) and put that into my app (Speaker Box Lite) I got some similar info. For one driver the app says the lowest F3 I can get is 28,8hz which I can get from exactly 180 liters to 263L. F3 @700L (ca. what I'll get from my enclosure) is still 30.2hz which is not that big a difference. F3 @700L is 29.2hz for 2 drivers, 28.8hz for 3 and 28.9 for 4. I would nearly be able to place 4 woofers in that enclosure, but I doubt that would be necessary. Nice to know I could though. 3 woofers is not that crazy an idea. I could start out with 1 driver in the middle. And when I have the money cut out 2 new flanking holes to put 2 new drivers in. 

Nice to hear some good comments on transducers, have not had this clear answers on the subject! Will not pump any real money in buttkicker. Will buy a mini to allow me to have some LFE at later hours. Will disable it at daytime when using the subwoofers.

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If I'm reading right, you have a rather huge space to fill, especially if we're talking about 30k cuft.  I'm having trouble understanding your drawing.  What are the units for the dimensions?  It looks like the right side is open.  Is the left side open too?

In any case, it may be tough to get a lot of output below 20-30 Hz in that space, especially if you want the system to be able to keep up with the horns.  While two 18s in the riser can provide some tactile sensation, I don't think you're gonna get much output down low with just those subs in sealed form.

The reason I personally favor the Crowsons for tactile response is that I believe they are more likely to give consistent results because of how they are designed.  The Buttkickers act more as shakers, so results will depend more on the characteristics of the furniture.  With drivers installed into a riser, the response will depend on how the riser is constructed because its flexure is a big variable.  It's encouraging that @Infrasonic is satisfied with the results of his.  I gather if you duplicated his design (and your futon plus listeners weighed about the same), you would probably get similar results.  Otherwise, it's hard to say what will happen.  I'm sure it'll be fun as long as it isn't too stiff.  I also completely agree with him that a lot depends on the quality of the integration.  Optimizing levels, crossover, and possibly even EQ are likely to lead to a much more satisfying experience regardless of what you choose. 

I do agree that the Ultimax 18s are the better choice for the riser.  A driver like the 21SW152 is likely to be more beneficial if you have less volume to work with (i.e., you are power constrained rather than excursion constrained) with or if you care about output in the higher frequencies.  OTOH, a pair of low-tuned ported cabinets based on the 21SW152 could probably make some decent bass in that space.  I think it's worth producing actual bass below 20 Hz if you can, but the benefits are diminishing below that point and especially below 15 Hz.  Given the size of your space, you may want to compromise with a higher tune, depending on just how much output you want.  Placement also has a big effect.  For the lowest bass, you ideally, you want to place them adjacent to the largest/longest room surfaces, so if the left side of the room is closed, then placement along that wall may be best.  Of course, whatever placement you choose also impacts how easy it is to integrate all the different subs.

Will you have some kind of EQ capability such as in your amps?  That will help a lot, both for integrating subs and for getting the best performance out of them.  The F3 of the finished product is much less important when you have EQ to shape the response to your liking.  When you have EQ, what's important instead is whether you have enough excursion, voltage, and power to reach the output you want at each frequency.

15 minutes ago, Droogne said:

Semi-unrelated question. How realistic is it to completely disassemble an enclosure, and reassemble it later? 

Typically not realistic at all.  It could certainly be done if the enclosure were designed to allow for disassembly, but that would be a very challenging design.  For one thing, you need ensure that the assembled product is adequately sealed to prevent air-leaks, which means that you'd some kind of gasket system along each outer edge.  Furthermore, subs need to be braced to reduce leakage of sound from the cabinet and to reduce annoying panel resonances.  Anywhere that panels are touching one but not glued solidly is a potential source of buzz unless there is some soft material in between.  So unless you are some kind of design expert or have some crazy ambition, the answer is no.  I certainly have never seen it done before.

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14 minutes ago, SME said:

If I'm reading right, you have a rather huge space to fill, especially if we're talking about 30k cuft.  I'm having trouble understanding your drawing.  What are the units for the dimensions?  It looks like the right side is open.  Is the left side open too?

In any case, it may be tough to get a lot of output below 20-30 Hz in that space, especially if you want the system to be able to keep up with the horns.  While two 18s in the riser can provide some tactile sensation, I don't think you're gonna get much output down low with just those subs in sealed form.

The reason I personally favor the Crowsons for tactile response is that I believe they are more likely to give consistent results because of how they are designed.  The Buttkickers act more as shakers, so results will depend more on the characteristics of the furniture.  With drivers installed into a riser, the response will depend on how the riser is constructed because its flexure is a big variable.  It's encouraging that @Infrasonic is satisfied with the results of his.  I gather if you duplicated his design (and your futon plus listeners weighed about the same), you would probably get similar results.  Otherwise, it's hard to say what will happen.  I'm sure it'll be fun as long as it isn't too stiff.  I also completely agree with him that a lot depends on the quality of the integration.  Optimizing levels, crossover, and possibly even EQ are likely to lead to a much more satisfying experience regardless of what you choose. 

I do agree that the Ultimax 18s are the better choice for the riser.  A driver like the 21SW152 is likely to be more beneficial if you have less volume to work with (i.e., you are power constrained rather than excursion constrained) with or if you care about output in the higher frequencies.  OTOH, a pair of low-tuned ported cabinets based on the 21SW152 could probably make some decent bass in that space.  I think it's worth producing actual bass below 20 Hz if you can, but the benefits are diminishing below that point and especially below 15 Hz.  Given the size of your space, you may want to compromise with a higher tune, depending on just how much output you want.  Placement also has a big effect.  For the lowest bass, you ideally, you want to place them adjacent to the largest/longest room surfaces, so if the left side of the room is closed, then placement along that wall may be best.  Of course, whatever placement you choose also impacts how easy it is to integrate all the different subs.

Will you have some kind of EQ capability such as in your amps?  That will help a lot, both for integrating subs and for getting the best performance out of them.  The F3 of the finished product is much less important when you have EQ to shape the response to your liking.  When you have EQ, what's important instead is whether you have enough excursion, voltage, and power to reach the output you want at each frequency.

Typically not realistic at all.  It could certainly be done if the enclosure were designed to allow for disassembly, but that would be a very challenging design.  For one thing, you need ensure that the assembled product is adequately sealed to prevent air-leaks, which means that you'd some kind of gasket system along each outer edge.  Furthermore, subs need to be braced to reduce leakage of sound from the cabinet and to reduce annoying panel resonances.  Anywhere that panels are touching one but not glued solidly is a potential source of buzz unless there is some soft material in between.  So unless you are some kind of design expert or have some crazy ambition, the answer is no.  I certainly have never seen it done before.

I'll answer tomorrow as I'm going to bed, but want to adress something quickly. I'm terribly wrong! Not 30 000 cuft, but rather 2900 (80 cubic meters.  A 16x16 feet room with adjacent 8x11 feet room with an 8 foot height. ) Not sure how I got that completely wrong... Also yes, the room is open the right, but closed to the left. Meusurements are in centimeters (I live in Europe, Belgium)

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1 hour ago, Droogne said:

Well to say I'm on a budget.. that is true and it's not. It really depends on how much I would gain by upgrading. I'll have to figure out the enclosure thing though.. When I combined the info from their site (lowest single sealed F3 @7cuft) and put that into my app (Speaker Box Lite) I got some similar info. For one driver the app says the lowest F3 I can get is 28,8hz which I can get from exactly 180 liters to 263L. F3 @700L (ca. what I'll get from my enclosure) is still 30.2hz which is not that big a difference. F3 @700L is 29.2hz for 2 drivers, 28.8hz for 3 and 28.9 for 4. I would nearly be able to place 4 woofers in that enclosure, but I doubt that would be necessary. Nice to know I could though. 3 woofers is not that crazy an idea. I could start out with 1 driver in the middle. And when I have the money cut out 2 new flanking holes to put 2 new drivers in. 

 

Imho, all the specifics of attaining some ideal F3 are not so useful in this case. It's of my opinion that the real factor to consider is the momentum or inertia of the transducer. Because these will allow you to physical couple yourself to the bass you don't have to look at SPL numbers, alone. Because it really doesn't tell you all you need to know. What I'm about to say is worth discussion in it's own thread but for maximum sensation in the lowest frequencies, frequency response will not tell you how well you feel and perceive said frequencies. I've seen and been in lots of theaters that measure flat to single digits at the seat and the sensation never matches the actual audible response.

Like all subwoofers intended for fidelity, aiming for an alignment between maximally flat .707 to critically damped .5 is preferred. It's of my opinion that the excursion profile plays a part on how the tactile response is shaped. A maximally flat .707Qtc would have excursion profile that rises rapidly and then flattens out. A critically damped .5Qtc will have a slowly raising excursion that continues to increase as frequency decreases. I haven't tested this but I think it can affect things too.

Anyway, as long as the volume of this riser is large enough to be of optimal Qtc range then it is fine for a subwoofer riser. Don't get all hung up on meeting some specific number of F3 as it will all be irrelevant in actual use. You'll be EQ'ing this like any other bass system.

58 minutes ago, SME said:

If I'm reading right, you have a rather huge space to fill, especially if we're talking about 30k cuft.  I'm having trouble understanding your drawing.  What are the units for the dimensions?

Lol. Looks like centimeters.

58 minutes ago, SME said:

The reason I personally favor the Crowsons for tactile response is that I believe they are more likely to give consistent results because of how they are designed.  The Buttkickers act more as shakers, so results will depend more on the characteristics of the furniture.  With drivers installed into a riser, the response will depend on how the riser is constructed because its flexure is a big variable.  It's encouraging that @Infrasonic is satisfied with the results of his. 

Some people like to make their riser flimsy or flex naturally.

I did not design mine to be like that. In fact, it has one single 2x4 down the middle (short-wise) just to keep it from having any flex. It's the inertia of the twin 18's that provides the awesome ULF effect at the seat. Not the middle of the riser where there is zero contact with anything. I get the idea behind it but after doing the build, it's not important. There is tremendous ULF "trampoline effect" at my seat even with a stiffened riser floor.

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2 hours ago, Droogne said:

I'll answer tomorrow as I'm going to bed, but want to adress something quickly. I'm terribly wrong! Not 30 000 cuft, but rather 2900 (80 cubic meters.  A 16x16 feet room with adjacent 8x11 feet room with an 8 foot height. ) Not sure how I got that completely wrong... Also yes, the room is open the right, but closed to the left. Meusurements are in centimeters (I live in Europe, Belgium)

OK.  Yes, that makes a big difference!  It sounds like you are leaning toward doing the subs-in-riser, in which case I'd vote for going with a pair of the 18" drivers.  As for enclosure size, the optimal depends on what you are trying to accomplish.  Let me know if my discussion below is confusing, and I'll elaborate on it.  Do you know what amp(s) you will be using?  As I said, using amps with EQ capability can give you a lot more flexibility.

My thought is that you can see where the pair of 18s gets you in that space, and if you want more deep bass, you can build some separate ported subs.  Two ported 21SW152-based subs ought to be pretty capable in that space.

1 hour ago, Infrasonic said:

Imho, all the specifics of attaining some ideal F3 are not so useful in this case. It's of my opinion that the real factor to consider is the momentum or inertia of the transducer. Because these will allow you to physical couple yourself to the bass you don't have to look at SPL numbers, alone. Because it really doesn't tell you all you need to know. What I'm about to say is worth discussion in it's own thread but for maximum sensation in the lowest frequencies, frequency response will not tell you how well you feel and perceive said frequencies. I've seen and been in lots of theaters that measure flat to single digits at the seat and the sensation never matches the actual audible response.Like all subwoofers intended for fidelity, aiming for an alignment between maximally flat .707 to critically damped .5 is preferred. It's of my opinion that the excursion profile plays a part on how the tactile response is shaped. A maximally flat .707Qtc would have excursion profile that rises rapidly and then flattens out. A critically damped .5Qtc will have a slowly raising excursion that continues to increase as frequency decreases. I haven't tested this but I think it can affect things too.

For a sealed system with a given driver, excursion and output are tied together.  Output vs. excursion in a sealed system drops by 12dB/octave for all frequencies, regardless of Fb, Qtc, or anything like that.  With anechoic response shape having Q of 0.707, the transition between flat(-ish) and 12 dB/octave roll-off (centered at the Fb, the resonance of the sealed box system) is fairly narrow, so excursion remains relatively constant below the Fb.  With lower Q anechoic response shape, the transition is wider, so excursion can continue to increase quite a ways below Fb.

If the primary aim is tactile response, then it makes sense that one would want an *anechoic response shape* with a Q in the range you suggest.  That doesn't mean that the Qtc of the sub needs to match that Q.  With signal-shaping EQ, one can always adjust the anechoic response shape, again provided that the there is enough displacement, volts, and power to achieve the desired output.  I know the impact of this kind of electronic signal shaping can be simulated in WinISD.  Some other programs may be able to do this too.

A larger sealed enclosure will have a lower Qtc and will be much more efficient at lower frequencies in general, but it will need more volts for the same output around Fb and will need some EQ boost there relative to the surrounding frequencies for a higher Q response shape, even though it's still more power efficient.  This can still work well with amps that can deliver more volts and power around resonance than in the ULF, and the lower Qtc may make it easier to "get there" with such amps.  It will definitely help reduce power compression.

Note that the audible effects of the anechoic response shape (either with or without signal shaping) will be altered by the room as well.  Hearing most likely depends more on the in-room response shape.  Often an anechoic response with a Q well below 0.707 matches better with natural room gain.  As such, there may be a bit of a compromise between what sounds best and what feels best when relying entirely on the in-riser subs for reproduction of content below 35 Hz.  Obviously, this is a lot less of a problem if the bottom end is handled by separate subs.

Edit: With regard to the statement in bold above, I have to confess that I don't have any idea what response shape is best for tactile sensation.  When the time comes for me to install Crowsons and experiment with them, perhaps I'll have a stronger opinion.  If one wants tactile sensation well into the single digits Hz, then presumably one would want a relatively flat response that goes as low as possible or possibly even a response that slopes up.  Just about any sealed system will be rolling off rapidly by this point, unless it is adjusted by signal-shaping EQ, and to maintain a native flat response into the single digits requires enormous driver excursion for much audio output.  If the signal level is kept low, this could be fine for a tactile device, but then it would not provide much bass for hearing.  This is another reason why I lean toward using separate devices for sound vs. tactile, but that's not to say this approach can't produce pleasant results.

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2 hours ago, Infrasonic said:

Some people like to make their riser flimsy or flex naturally.

I did not design mine to be like that. In fact, it has one single 2x4 down the middle (short-wise) just to keep it from having any flex. It's the inertia of the twin 18's that provides the awesome ULF effect at the seat. Not the middle of the riser where there is zero contact with anything. I get the idea behind it but after doing the build, it's not important. There is tremendous ULF "trampoline effect" at my seat even with a stiffened riser floor.

It probably still has a bit of flex with the 2x4 down the middle.  The question is whether it is enough to be significant here.  You are feeling motion, so presumably the futon is moving.  This could be induced by air movement from the cone, in which case the cone mass (inertia) has no effect.  Or, it could be that the futon is moving because the riser is moving, which would occur either by flexure or by hopping off the floor (accompanied by a nasty chattering sound).  Or, it could be that the floor under the riser is flexing.  I guess the question is, which is it?  I gather you could find out if you stood up on the riser without sitting on the futon, and if you still felt sensation, then you could try standing on the floor next to the riser.  If you don't feel the bouncy effect unless you are sitting on the futon, then it is probably induced by the air movement from the driver, and neither the driver mass or riser flexure properties would come into play.

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6 hours ago, SME said:

It probably still has a bit of flex with the 2x4 down the middle.  The question is whether it is enough to be significant here.  You are feeling motion, so presumably the futon is moving.  This could be induced by air movement from the cone, in which case the cone mass (inertia) has no effect.  Or, it could be that the futon is moving because the riser is moving, which would occur either by flexure or by hopping off the floor (accompanied by a nasty chattering sound).  Or, it could be that the floor under the riser is flexing.  I guess the question is, which is it?  I gather you could find out if you stood up on the riser without sitting on the futon, and if you still felt sensation, then you could try standing on the floor next to the riser.  If you don't feel the bouncy effect unless you are sitting on the futon, then it is probably induced by the air movement from the driver, and neither the driver mass or riser flexure properties would come into play.

 

9 hours ago, Infrasonic said:

Imho, all the specifics of attaining some ideal F3 are not so useful in this case. It's of my opinion that the real factor to consider is the momentum or inertia of the transducer. Because these will allow you to physical couple yourself to the bass you don't have to look at SPL numbers, alone. Because it really doesn't tell you all you need to know. What I'm about to say is worth discussion in it's own thread but for maximum sensation in the lowest frequencies, frequency response will not tell you how well you feel and perceive said frequencies. I've seen and been in lots of theaters that measure flat to single digits at the seat and the sensation never matches the actual audible response.

Like all subwoofers intended for fidelity, aiming for an alignment between maximally flat .707 to critically damped .5 is preferred. It's of my opinion that the excursion profile plays a part on how the tactile response is shaped. A maximally flat .707Qtc would have excursion profile that rises rapidly and then flattens out. A critically damped .5Qtc will have a slowly raising excursion that continues to increase as frequency decreases. I haven't tested this but I think it can affect things too.

Anyway, as long as the volume of this riser is large enough to be of optimal Qtc range then it is fine for a subwoofer riser. Don't get all hung up on meeting some specific number of F3 as it will all be irrelevant in actual use. You'll be EQ'ing this like any other bass system.

Lol. Looks like centimeters.

Some people like to make their riser flimsy or flex naturally.

I did not design mine to be like that. In fact, it has one single 2x4 down the middle (short-wise) just to keep it from having any flex. It's the inertia of the twin 18's that provides the awesome ULF effect at the seat. Not the middle of the riser where there is zero contact with anything. I get the idea behind it but after doing the build, it's not important. There is tremendous ULF "trampoline effect" at my seat even with a stiffened riser floor.

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. 

 

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Screenshot_20171025-111211~2.png

Screenshot_20171025-111539~2.png

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How much is an Ultimax in Belgium? How much is a 21" B&C? I'm just curious. There may be other driver options that make more sense given his location.

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18 minutes ago, Ricci said:

How much is an Ultimax in Belgium? How much is a 21" B&C? I'm just curious. There may be other driver options that make more sense given his location.

I've looked pretty much anywhere and I do not find any good options for my purpose. The B&C is 700, the Ultimax 400. 

Someone on another forum convinced me to look for high Xmax (20mm), and I haven't found any driver that has these specs. Most drivers I find are pro drivers. If you would know some lessen known quality woofers in Europe I'm glad to contact them. Other B&C drivers might be possible too.

 

 

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Do you have Alpine? How much is a SWS-15d2 or an SWR-1522D?

$400 is a lot for a UM18.

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14 hours ago, SME said:

It probably still has a bit of flex with the 2x4 down the middle.  The question is whether it is enough to be significant here. 

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.

Quote

You are feeling motion, so presumably the futon is moving. 

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

Some ULF effect are not unlike this:

giphy.gif

Quote

This could be induced by air movement from the cone, in which case the cone mass (inertia) has no effect.  Or, it could be that the futon is moving because the riser is moving, which would occur either by flexure or by hopping off the floor (accompanied by a nasty chattering sound).  Or, it could be that the floor under the riser is flexing.  I guess the question is, which is it?  I gather you could find out if you stood up on the riser without sitting on the futon, and if you still felt sensation, then you could try standing on the floor next to the riser.  If you don't feel the bouncy effect unless you are sitting on the futon, then it is probably induced by the air movement from the driver, and neither the driver mass or riser flexure properties would come into play.

More motion when sitting.

 

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7 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).

Simulated F3's and net Q numbers are irrelevant in this case.

You will cross low (your stated intention was 30hz and down) and will likely use EQ.

7 hours ago, Droogne said:

 

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?

Anything between .577 and .8 is fine.

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5 minutes ago, Infrasonic said:

Simulated F3's and net Q numbers are irrelevant in this case.

You will cross low (your stated intention was 30hz and down) and will likely use EQ.

Anything between .577 and .8 is fine.

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

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