Funk Audio

1 hour ago, chrapladm said:

Well thanks for this. BC IPAL's are the best value for myself and where I live. The IPAL pair would be the same price as a delivered 24UHT.  So if the 21" version kept up with the 21IPALS down low then the 24 should be a better option for me if I can swing the payment right now. Above 40-50hz the IPALS run away from the 24" but I'm only after ULF in a sealed alignment.

Would @Ricci have time to ever test a 24uht?

I looked at possibly getting one and having one shipped to him. Although I would then have to get a quote for shipping from Ricci to myself in Australia. Either way I'm not in a hurry for a build yet as I have a lot going on. SO I have plenty of time if he is interested.

Last I talked to Josh, sounded like he would be game for my idea, if only this covid thing would go away already.... maybe one day hopefully.

I suggested to fly him and his gear up here, we have a suitable area to test, and for the cost of sending him a couple things we could do, well everything we can manage to have prepped 🤪.

You can see how the early version of this did for seeing what kind of excursion the GUJ platform is capable of here;

https://data-bass.com/#/systems/5c2682df1cefb00004803ab5?_k=4sikz2

You can see it can out travel the dual IPAL21 tested, and this version has over twice the normalized motor strength.

11 hours ago, SME said:

Do you know what assumptions are involved?  Particularly concerning the air?  The situation is very different if the air is stagnant than if it is allowed to convect freely.  My guess is that a heat-sink calculator would assume free (natural) convection under some particular mounting configuration (say installed onto an infinite slab).  A sealed box stuffed with insulation may not allow much if any natural convection, so the situation may be worse than this calculation suggests.

On the up side, if the coil is mounted in very close physical proximity (on the order of one millimeter or less, by my rough calc) to other metal parts of the driver, enough heat could travel them through the air to make a difference.

The calculator I found allows orientation and ambient temp settings, if I set it to 20c and face down the power drops to 42watts. I am sure one could calculate the thermal resistance of the air in the box and the wood as well and input the degrees/watt resistance to the calculator as well to get a more accurate sim. If I change the ambient temp to 50c degrees, to assume the inside of the enclosure might stabilize at that then the power to get the coil over 220c drops to 35watts. Adding steel helps but even setting the final surface area to what a huge motor would have keeping the source(coil) the same size and setting 1mm air between the coil and steel brings us up to ~55watts at 50c ambient, ~65watts at 20c.  My main point is no matter what you do its usually going to be a dismally low amount of true RMS power a driver can take for an infinite period of time.

That actually becomes a calculable thing at that point. You can call the coil a flat heat sink, there are online calculators to tell you how many watts will reach what temp in ambient air. I put in the area for a 4" coil 2" long, at 50watts it hits 225c so that's where it would melt, high temp coil insulation is rated at 220.

5 hours ago, Ricci said:

Since we are discussing some type of HIL related rating here...I'd like your opinions. 

Should I use max burst for it, which will tend to favor passive systems at the higher frequencies due to the absurd amount of amplifier on tap, or use the max long term sweeps which will be more granular and more fair between turn-key systems and the passive stuff, but may under represent the actual dynamic potential by a large amount?

Alternatively should it be discarded altogether? Too much work, not enough pay off, too confusing for casual enthusiasts?

I think long term would be best, as most of the time the power level used on a passive system to get the highest sweep is about the amount of power that would be spec'ed for it in use, so even if a system can do more with more power in the upper frequencies most applications wont bother taking advantage of it.

26 minutes ago, SME said:

Thanks for your input re humidity vs speaker parts.  I don't see a rubber surround being too happy at -40 deg.

Expensive how?  A servo controlled woofer is likely to rely on (re)active DSP.  The Apple HomePod uses a servo woofer in addition to adjusting its room EQ in realtime using data from built-in mics.  I believe many cars already use active noise cancellation.  Some cars also play fake engine noise through their speakers.  I think Harley may do something like this on the outside for its European bikes, in order to provide a "Harley-like sound" while staying within EU noise restrictions.

I could definitely implement reactive capabilities with my current PC-based DSP system, if there was a good justification for it.  I live in a climate that has fairly large humidity fluctuations.  It's reasonable to assume that indoor relative humidity will correlate with outside dew point temperature, given enough time for the air in the house to equalize.  A/C usage is likely to affect things a bit too.  I now casually monitor dew points published by NWS here.  In the last week, I've seen multiple jumps from 58 deg F (14.5 deg C) to 28 deg F (-2 deg C) and back, each in less than 24 hours.

Humidity changes have a very measurable effect on absorption in the air of ultra high frequencies.  It's probably reasonable to assume that human listener adapt to these changes when listening to "normal sounds" but audio reproduction systems typically have flaws, and the humidity changes could affect the relative audibility of said flaws, leading to intermittent changes in apparent sound quality.

I am aware of the things you mention, what I am talking about is going the next level and implementing it in a high end system made up of all kinds of different components, and compensating for driver specific changes, meaning you would need to know what to have the system change to compensate, and where for each part of the system, a little harder to do when its not a complete integrated system. Also I am talking about not just frequency response correction. Again though there is the question of what do you bother compensating for, to what degree and would it be of much detectable value.

2 minutes ago, Ricci said:

+1

Home audio has it easy with a relatively stable environment. Outdoor pro audio work at festivals and the like is a whole other deal. The worst is car audio. 100+ deg temperature variations, random humidity and barometric pressure, road noise, etc...Forget that tightly dialed in DSP. 

🤔"reactive dsp" I wonder if that could be a thing, albeit prohibitively complex and expensive I am sure. Have sensors that detect temp humidity pressure and even outside noise, that feedback into a system that compensates in the dsp signal processing with some noise canceling action too.

7 hours ago, SME said:

Definitely agree about not really knowing what to test in drivers.  I think it's fascinating that some of the most audible "distortion" is often the hardest to directly measure.  An example of a weird thing I worry a bit about these days is how humidity changes to driver suspension might affect stability of sound quality in a very tight in-room bass calibration.  It may not really matter, or it could have rather profound effects.  I don't really know.  Perception is extremely sensitive to certain aspects of sound and seemingly completely ignorant of others.  Which stuff matters?

That's what keeps things interesting for me, always trying to learn more, the hows whys and what matters, then how to correlate the science to the perception, by no means does anyone have it "all figured out". Some of science's biggest discoveries have been accidents. I have to humbly admit I have discovered some things by accident myself.

Humidity can very well affect some materials, thick untreated paper cones would change in mass/damping properties, I have never investigated this so I cant say how significant the differences would be. Most suspensions shouldn't be affected much with the synthetic materials and resins used, temperature certainly can change them though, that is something I consider in designs. For things like that you factor for a range, min max, and make sure everything still falls within desired spec at each end of the range. Luckily we don't need worry about the speakers/subs any of us use(make) working right at -40 or anything like that, I believe that would cause some issues.

2 minutes ago, Ricci said:

 this type of output density rating is really just for "learning" rather than salesmanship to consumers. They have a ton of other usually more pressing considerations like, cost, looks, warranty service, availability, etc. 

I do believe your right on that.

4 hours ago, Wayne said:

Here is all active commercial subs on data-bass (plus the F113) . Looks to me that linear volume vs log SPL is a decent fit.  The r squared is 0.6684 or a correlation of 82%.  The JTRs also outperform the trend on output at 20 Hz vs size.

 

Have to say I am kicking myself now for not sending in the square versions of the 18.0 and 21.0, those curved sides 🤔

The 18.0 we make in a 20"x20"x20" cube and the 21.0 in a 22.25"x22.25"x16", both have identical internal volume to the ones tested.

1 hour ago, SME said:

Well, for subs measured by Data-Bass, there are the max long-term output, power compression, and harmonic distortion plots.  For DIY systems there're also impedance and raw driver response plots which offer at least some hints as to how inductance effects may impact sound quality.

Of course none of these things can be conveniently distiled down into one SPL "output" number, but so what?  If you want the best, you're not going to find it by looking at a single chart or a single metric.  That kind of "make everything quantifiable" BS is a major error, perhaps even at the root of some of the major problems facing our society right now.  (Serious!)  BTW I say this as an engineer who specialized in study of computational science.

Also, why CEA at 20 Hz?  Many small rooms have a lot of room gain by then.  My room in particular dramatically boosts sub efficiency there.  The air starts noticeably rippling before the "signal present" lights even come on on the amp.  Tell me what the sub can do at 10 Hz, and then I'm interested.  But of course for someone who need something small to fill a large room, maybe 30 Hz is the money spot.

Hoffman's Iron Law can be overcome with brute (motor) force.  The limitation then is how much magnetic flux you can ultimately focus on a coil, and whether the end result is remotely affordable.

FWIW, I spent an excruciatingly long time deciding on which subs to buy for myself.  I had a very specific location and space budget, and wanted the best I could possibly get with that space.  I had to make a custom design.  There was no chart that told me which driver would work best.  I had to consider all the possibilities individually.

I have to agree with you there, firstly its impractical to test even all the known aspects, things like intermodulation distortion, and subharmonic distortion, are factors I consider in designs that also affect the sound but to test these adds a whole other level of complexity. Besides the fact that who besides the engineers designing drivers/systems know how to interpret them. As it stands a lot of people already don't know how or even misinterpret the measurements Databass does do. I know there are some out there who believe we know all there is to know about drivers and how they work, and how to test every aspect of them and that how they sound can be completely derived from these tests, but I have been listening to designing and building drivers for some time now and even with all the possible aspects we know about and test for I still believe its fully possible that there are things about drivers we haven't even put a name to yet let alone devised a way to test.  

Would be interesting if it could be made to work as such.

 

I think of the cooling on some of the Sundown and Stereo Integrity drivers with lots of little holes and how those could be coolant pipes or something. I don't know how to get liquid coolant into the motor and around the voicecoil without saturating the open gap with liquid coolant and most likely preventing proper action of the system.

 

There is no way other people haven't thought about this sort of thing. I guess it would require some serious R&D and engineering just to test it.

 

Might be easier to water cool an amplifier.

Air cooling still has a lot of potential before liquid cooling is needed, I have some ideas for some really crazy stuff with unique air cooling system(I do have some ideas for liquid cooling as well), but nothing that's really "practical" either way. That wont stop me though , just might be a while.

If the 18.0 is run on 240V you gain on average exactly .5db for the burst output, that brings it closer to the peak average. If you look at the "short term averages" chart yes the S1 would still have 0.7db higher burst average 10-125hz, I feel that's "close overall". Yes the S1 has more burst output, and quite a bit at some frequencies, but a little less at others. There are more aspects to consider than just burst output too, for example long term output average 10-125hz for the 18.0 on 120V would be almost identical to the S1, and on 240V about 1db higher. The S1, and S2 as this thread is for are great subs and the tests show it.

 

If you take 5 db off across the board for CEA-2010 Max Burst, then the S1 would have the following advantage over the FW18:

10 Hz:    +0.9 dB
12.5 Hz:  +0.7 dB
16 Hz:    +2.1 dB
20 Hz:    +3.7 dB
25 Hz:    +3.5 dB
31.5 Hz:  +2.3 dB
40 Hz:    +1.9 dB
50 Hz:    +1.5 dB
63 Hz:    +0.2 dB
80 Hz:    -0.7 dB
100 Hz:   -0.9 dB

I must be looking at a different product:

Sorry just looking at the wrong graph if your referencing where I said "the S1 and 18.0 look near equal 30hz down for long term output with the 18.0 having a clear advantage over 30hz, as it compares directly to the S2 40hz up"

That is burst output your showing, in reference to which I said "Burst output is very close across the board to the S1(take 5db off across the board for the S1 as per your comments on the S2 vs S1), each having a little more than the other in some areas"

Yep this thing is a beast, esp. for a sealed design -- 127dB . I would love to see this thing run up against the G213 or better yet, FunkAudio 18.2 just for fun

 Well if you look at the 21.0 tests, and add three db across the board, you get an idea how the 18.2 would look as they share the same motor structure and amplification(per driver) and proportionally more airspace. So it should be nearly matched for long term output under ~30hz, with similar distortion at max output, lower distortion at just below max as already the 21.0 is very close in distortion given the same output level(115db sweep for 21.0 compared to 105db sweep for S2) under 30hz when both are down a couple sweeps below max. Then it walks away for output over 30hz and distortion over 50hz. Not really a fair comparison though considering the cost. The S2, and proportionally the S1 shows awesome performance for the money under 40hz, the 18.2 shows what it takes to match that performance under 40hz at nearly half the size. Massively more power and cost, is what it takes to push the laws of physics hard up to the wall.

Comparing to the 18.0 is a little more fair as they are closer in box size and power per driver, although the 18.0 still costs more. Considering the S1 is said to be basically half the S2, so -5-6db across the board. Factoring that in the S1 and 18.0 look near equal 30hz down for long term output with the 18.0 having a clear advantage over 30hz, as it compares directly to the S2 40hz up. Burst output is very close across the board to the S1, each having a little more than the other in some areas, as well as distortion is comparable 30hz down. The advantage the 18.0 has is over 50hz where distortion and power compression are much lower, lower even than the S2 compared directly at similar outputs in that range.

Hi Dave,

Don't you think things like impulse response, group delay, power compression, distortion, and inductance related affects change the way things sound even with a matched FR?

The RF is significantly better in "all" these "factors"

I feel Josh downplayed it but he did say "it does seem like these changes resulted in a much better upper bass range through the crossover region. It definitely seems like there is a better sense of attack and punch on kick drums and sharp upper bass transients when the system is cranked up."

I have done enough work with drivers similar to the XXX(and the XXX itself), and with drivers like the RF to concur albeit much more strongly with the differences Josh has noticed, I will agree with the sheer number of drivers and amount of power on hand the differences at normal listening levels would be diminished, but even at that differences are noticeable. On a 1 to 1 basis when driven to limits the difference are Huge, "massive"... and some other descriptive words you may not like...

Hi Nathan,

 

Can you be more specific with what "driven hard" means in Ricci's room, how same FR can possibly sound different and any of the "many factors that will change the sound" that obviously aren't apparent to me?

In other threads, for example, there is howling and jeering over snake oil salesmanship claims of the benefits of using certain cables, etc., but here the terms "better in every way" and "massive step up in every possible way" are cool?

 

"Massive step up in every way"?

With 80-100 liters of displacement and >20KW of power there is no way to drive either system to the point of reversion to non-EQ'd response in Josh's room unless you purposely do it for no known reason.

He can theoretically raise the crossover if he wishes, although both traces show inaudible differences to 100 Hz. How hard would you have to push them to hear a massive difference?

 

Back when Josh was contemplating buying the XXXs he asked my opinion. I designed a sealed, DO, push/pull box of some 20 cubes net. I mentioned that 10 cubes per driver would be the minimum I would put the XXX in. There's an 8-10dB increase in sensitivity and efficiency <20 Hz with the XXX in >2X the box Josh has them in. Seems a reasonable choice to me to build better enclosures than to spend 10 grand more for drivers and claim "better in every possible way".

 

Josh said his goals were cost no object to see what he could do with the existing small boxes. I agree that he met those goals with happy results. But, to stretch that to "massive step up in every possible way" begs more specific data.

What am I missing? $20,000.00 vs $7,500.00 for same result. I was never a fan of the huge box requirement of the XXX driver or of stuffing it into such a radically small box but that neither here nor there in the comparo. I'm not seeing the big net gain everyone else seems to readily see... The FR at the seats is the same, neither system lacks headroom and power to drive the system is a non-issue.

That's the whole point the "result" is not even close to the same, the same FR is not the end all be all and does not mean they will sound the same, especially when driven hard, there are many factors that will change the resultant "sound". The RF's are a massive step up in every possible way.