Dear Sirspeedy: I love you man ! and that's why ( I take my time for this. ) I give you next some high-lights that different people ( including me ) posted on this thread on the subject ( two subwoofers/IMD/HD ):
this one was an answer to what you posted:
Dear Sirspeedy: +++++ " if the main speakers can support a certain low frequency,before rolling off,it will be best to bring in the sub at just under this point. " +++++
Well this is one approach that mainly goes to have a lower bass response: it is the REL approach and other subwoofer manufacturers but not all of them.
My approach is different from yours, mine goes to obtain ( first place ) a better quality performance in my main speakers and in second place to achieve a better quality bass performance that could goes lower too.
I use two subwoofers in true stereo way to achieve those targets, the first one ( that you can't achieve with your approach. ) is obtained lowering the Intermodulation Distortion ( main speakers ), this means to stop to ask to the woofers ( main speakers ) the simultaneous reproduction of frequencies between 20Hz and 200HZ or higher( if yours goes flat to 30Hz then you still have some distorted response at 20Hz that makes higher the IMD subject/problem ), this means ( again ) that we have to choose a crossover frequency higher than what the main woofers are handled : in my case 60 Hz and in Eldartford 80Hz.
In this manner the main woofers will be free/less stressed of the low bass reproduction working from 60Hz-80Hz up and lowering ( cleaning in deep ) the IMD: this fact makes a huge improvement ( in any speaker including yours ) in the quality sound reproduction of the main speakers ( it is not matters what you think about or what I think about, lowering the IMD always improves the quality performance of " that " driver, physics laws. ).
The second advantage on this approach is that now the low bass frequency response not only goes down through the subwoofers but with a better quality bass performance due that those bass frequencies will be reproduced for " drivers /amplifiers " that were designed specific for those kind of bass frequencies. " +++++
+++++ " Where the subs can help us ? :
Intermodulation Distortions ( harmonic distortions ): Almost any three ways speaker ( all two ways/one way ) has it's crossover frecuency ( low driver ) between 150Hz and 450Hz. I can assume that any of ours speakers system goes down flat ( at least ) between 60Hz to 20Hz.
What does that means ?, well that a single driver has to reproduce frecuencies/harmonics from 20Hz/60Hz to 150Hz/450Hz. With that kind of frecuency range here exist a great intermodulation distortions that put it's " color " on the sound reproduction.
You have to imagine that that single woofer/driver has to reproduce, at the same " time ", a 30Hz frecuency along a 350Hz frecuency: here is where exist that IM that gives heavy distortions in what we hear ( there is no perfect driver: moving coil, electrostatic, ribbon, etc.. The speaker designers has to choose the best " trade offs ", but the distortions are there. ): less clarity, less resolution, less precision, less natural balance, less pitch, les, less, less......., and this is what we are really hearing: LESS MUSIC.
What happen when that low driver is free from those frecuencies ? ( main speakers: monitors or full range, it does not matters. My main speakers are flat to 22Hz and only 5db +.- at 18Hz and I have benefits with the subwoofers integration to my system ), below 60Hz ( this is the crossover frecuency that we find the best point to start to blend a subwoofer. Mines are at around this 60Hz frecuency: 78Hz,yours ( I think ) will be around that frecuency. ):
SUDDENLY the " lights are on ", your music/audio " life " its born: the mid bass is clean, the midrange is clean, the highs are clean: high resolution every where ( the distortions are almost gone ), and now you can really hear for the first time the MUSIC through your home stereo audio system: what a pleasure!!!!!. " +++++
Mark the second subwoofer is not to obtain more bass but to even and smooth the room bass response:
08-02-05: Skushino
After adding a second sub to my system, there was smoother bass response. Again, this isn't about louder or stronger bass, in fact, I was seeking lower, smoother bass. Ironic that the path to this goal was accomplished by adding a sub! My girlfriend is a great listener and concurred that bass was better quality. Since I returned the second sub (on loan from my neighbor), I miss the performance " +++++
this quote comes from a in deep research made by Harman International Group:
+++++ " Using very large numbers of subwoofers would result in
cancellation of room modes. For practical numbers of
subwoofers, there appears to be no obvious correlation.
Two subwoofers, at opposing
wall midpoints, performs very nearly as well as four at the
midpoints and gives a much better LF factor
Can a sufficiently large number of
subwoofers cancel out all room
modes?
Theoretically yes
With 5000 subwoofers, modal variation is virtually
eliminated. !!!! " +++++
+++++ " I don't know at which frecuency you are cutting your REL. But, for example, if the crossover is at 27-30Hz and if the low pass filter is of second to fourth order then your REL is reproducing frecuencies as high like 80-100Hz that are interfering with the same frecuency range of your main speakers " +++++
this quote comes from a friend ( Agon ) that send to me for this thread. The research/investigation or whatever were made by: Audio Perfectionist Journal and Vandersteen:
+++++ " Suppose I told you that you could add two
components to your system that would reduce
intermodulation distortion in the midrange by a
factor of two or more, dramatically improve the
resolution of midrange and high frequency detail,
double or triple the dynamic range capability of
your system without changing your existing
amplifier or speakers and improve imaging more
than you can imagine. You would probably be
interested, right? But wait, theres more.
These same components would allow the
amplifier to maintain tighter control over the
speakers in the mid-bass and lower midrange.
They could extend bass response to infrasonic frequencies
while lowering bass distortion and
improving the systems ability to accurately convey
the rhythm and pace of music. And these
same components could virtually eliminate the
uneven response at lower frequencies caused by
room standing waves.
Does all that sound too good to be true?
Are you concerned about the possible cost of all
this improvement? If all this is so easily achievable,
are you wondering why youve never heard
about it before?
Let me assure you that all these sonic
improvements can be yours and Ive been conservative
in my estimates of the level of audible
improvement youll get.
When properly integrated with the system,
subwoofers blend seamlessly with the main
speakers and dont make their presence known.
But thats a very hard sell to the average consumer
and selling is the name of the audio game.
Subwoofers are supposed to add bass, right?
After their initial forays into the market,
few manufacturers continue to try to make subwoofers
that accurately represent music. Why try
to educate consumers when its easier to just give
them what they think they want? Boom!
Subwoofer makers soon learned what
dealers had already figured out: if they cant hear
it woof they wont buy it. Manufacturers started
to build subwoofers with high-Q alignments and
vents in order to provide more slam. Dealers
started to set up their demonstrations for maximum
thump, and maximized sales figures.
Awareness of the basic concepts of specialized
bass reproducers faded or was suppressed.
Home theater exacerbated this situation.
People today expect a subwoofer to rattle their
fillings and the exaggerated bass that most subwoofers
deliver is incompatible with accurate
music reproduction.
But there is more to bass than boombass
is the foundation of all music. And there is more
to subwoofers than bass. They reproduce bass frequencies
to be sure, but bass extension is possibly
the least of the sonic benefits offered by good
powered subwoofers.
Why Good Subwoofers Improve Sound
In order to provide the benefits mentioned
at the beginning of this article, subwoofers must
utilize a dedicated bass amplifier, and the main
amplifier and speakers must be high-pass filtered
using a passive, first-order device.
A high-pass filter does just what you
would expect: it allows frequencies above the cutoff
point to pass, and blocks frequencies below
that cut-off point. " +++++
this is another quote on the subject:
+++++ " - There is no single external / stand alone amplifier that can work or do a better job than a low bass dedicated amplifier like the one that comes with a powered subwoofer:
think that this dedicated bass amplifier was designed/tailored to match every single woofer parameter: impedance, frecuency response range, damping, power, distortion, etc, etc,...
- It is not only this dedicated amplifier what makes this subwoofer approach/technology ideal to handle the low bass octaves.
The driver/woofer is designed/tailored too for that specific frecuency range.
There is no passive FRS ( full range speaker ), at any price with any amplifier, that could beat a self powered subwoofers in that frecuency range. When you have and hear the subs on your system you never can live again with out those subwoofers.
Here we have to remember other important issue: the best subwoofers are SERVO CONTROLLED, this characteristic give to the subwoofer a heavy advantage over a FRS about the low distortion that a well designed subwoofer had against a higher distortions on any FRS.
- With a subwoofer we not only gain with a lowest harmonic distortion but with a lowest intermodulation distortion too. This means better quality sound reproduction.
- Other advantage is that with the integration of two subwoofers in a true stereo fashion to a full range speakers system: the main ( s ) amplifier will be free of those high power consumtion low bass frecuency range: this means too, better quality music sound reproduction. No exception.
- Other advantage with the subs integration is that facilitate the integration of our mains speakers to the room.
Do you think that your FRS audio system sounds great? Wait till you do the subwoofers integration: you will be on music heaven !!!!!!!! Nothing less. Try it. " +++++
Please read carefully, I only want ( I would that ) that you understand the whole subject concept, if you want to aplicate or not is a totally different subject.
Regards and enjoy the music.
Raul.
