be wrote:

Instead of defining the ULF range from the reproduced instruments, it is much smarter to do it based on the first resonance frequency of the listening room, because the frequency response of a closed room has a 12dB/oct rise in frequency response, due to the cavity effect starting approximately half a octave below the fundamental mode of the room.

Yes, I would agree BUT there is one thing. The division upon LF an ULF is purely semantic division that we invent in order to stratify out verbiage. We presume that LF is bass and ULF is not tonally auditable bass. In reality there is no such a division. A playback might have ULF channels the will set to aggressive and “modulate” a tonal output of midbass of LF channel. It also might be that a normal LF channels might not have any tonal information. Between those two polar examples there are zillion possibilities that do not comply with any rules of stratifications. So, with all out conversation there is always a give or take leverage. A playback might have some kind of a channel that goes from 100Hz and all the way down and still to be perfectly operational.

My desire to separate, at list logically bass on LF and ULF is primary derive from the fact that in most practical cases LF and ULF is need different attention. If you look at my particular case then it is obvious that only after “inventing” the separation of LF and ULF I was able to understand what I am doing with my one playback. I have no LF but midbass and ULF. It does not bother me at all but while setting the thing up it was very critical to me to get the idea that my Midbass and my Lowers Bass are different players in the auditablety game.

Generally I agree that the first room resonance along with reverberation time in the room are very big players but I feel that they might be overridden by audio methods. The crossover slope at lower frequency channel is superbly powerful tool that can do some amassing things. Unfortunately it is VERY hard, virtually impossible, to find good hard-suspended low Fs bass drivers the work with low crossovers. The low Fs drivers have cones that have to much inertia and too much freedom. Combine this driver with no enclosure air suspension (open or infinite baffle) and you have the bass driver that shaking like jelo-cake during earthquake. Put in there tone character and it is absolutely not accomplishable mixture. There was one very good 14” hard-suspended Klangfilm driver (if I am not mistaken it was 405, it was long time ago when I experimented with it) that had nice tone and worked very well with no enclosure suspension but it was 50Hz driver and below it was rapidly dying. If you want the same at 25-30Hz then good luck to find it.

If it was up to me to experiment then I would get 10 per side Altec 416/515 drivers, put them in sealed array and try to see what happen. Altec had 515B with 24Hz of Fs, I am sure it is possible to drive Fs even lower. The key is do not let them to excurt to much. If each of them moves for a few mm then it might be a good result. Where to get 20x515B drivers and to be able to much their characteristics? Do not ask and do not tell if you know where…

Just how important are  subharmonics and undertones in audio, and how they affect tone? 

I played around for a while with the Townshend supertweeters,  this is a ribbon tweeter that you can barely listen to:  you plug it in and put it next to your ear and can barely listen to a hishsishisi (they claim 20khz-100khz).  Once you place it on top of a speaker with limited high frequency response,  say 18 khz,  a big change can be heard on the sound mainly on midbass!! Of course this is an effect caused by subharmonics and overtones going higher than what we are able to hear! (Good luck time aligning these things at 20 khz!!!)

To have a tweeter that goes up to at least 40 khz is a big thing and really helps a lot to the "tone" or perception of audio, we all have listened to this effect.
A bunch of modern tweeters go up to 50 khz.  I just use the example above because it does nothing under say 18khz and it is funny how it is hard to see if they are even working! 

I like to think of ULF on these same terms, it is a frequency we can barely hear (depending on xover steepness) but which brings those undertones and subharmonics that "complete" the sound of a musical wave with all its companions...

BR cabinets and other bass solutions need to have a high pass installed, to avoid excessive cone movement,  thus limiting the frequencies they are playing to a certain point,  ussualy 20- 25 hz,  even if they never really get down there,  it is mainly a mechanical solution.  A sealed enclosure can have what is called an open bottom,  meaning no high pass at 20 hz.  This allows for the driver to bring out a certian level of undertones even if they come at a lower amplitude,  say minus 6-9 db they are still present and one can notice them.  

Now I play a lot with a bass solution that inlcudes a LF and ULF with different drivers in different cabinets:  Pro drivers down to 45 hz and a big 15" servo subwoofer from around 40 hz down to supposedly 16 hz (no way to really measure down there).  Both have sealed cabinets; the bass is very good. But it is a PITA to put in phase.  When not in phase both drivers can fight each other to the point where lowering the level on the LF or ULF can add bass to the room!  The thing is we are using a 140 hz UBH and we needed a LF solution that would go up to 150 hz with stamina!  I could not find anything that could go up to say 200 hz and down to 20 hz with the dynamics and character needed to match up to a horn system!  And we really wanted it to go under 30 hz!!!

So eventually the ULF channel should work in the same way a "supertweeter" UHF works,  adding all these harmonics to the fundamental note.


Now someone is about to jump out with a new product  made out of cow dung from the hymalayas and silver covered Berylium that resonates in such a way that you cannot listen to it "ever" but adds these subharmonics and undertones that make your system sound sooo much better,  and it can even be aplied over the phone!!

Romy the Cat wrote:

noviygera wrote: p.s from my experience of having a 500 sq. ft. listening room with 7 ft. ceiling and having two 18" woofers in a infinite baffle configuration, it is not enough to pressurize the room. I am talking about low and medium listening levels. Four 18" would be just acceptable. Eight 18" woofers in infinite baffle will be good for a 500 sq. ft. room so there is your rough ratio according to my experience. Herman, I would like to ask what methodological reasoning you uses to assess that your room of 500 sq feet having two 18" woofers in a infinite baffle it is not enough? Do you feel that not enough bass? You do not have more power or gain in your amplification? Do your drivers excurt too much? Do you hear too high distortions or compression?  Do you have measurements in the room at the frequencies that you are interested in? The reason I ask as I feel that 4x 18 inchers for 500sq feet room is certainly wonderful but it is nowhere near absolute minimum. A good pair of 416/515 drivers with moderate 40Hz would perfectly fine for 500 sq. ft. Sure the more drivers and more size is better but when we do it we just minimize the excursion of each driver and improve sound by spreading all problem across multiple transducers allowing each transducer to be not as good as a single driver. Anyhow, I would be interested to know how you came to the concussion you have came.    The caT