Originally Posted by KidHorn
I don't find it surprising at all that multiple dissimilar subs sound good.
Well, we don't know what his reference is for "sounds good". We don't have any "context" to compare what he thinks "sounds good" vs. what he thinks "sounds bad." For all we know, his room may sound like a disco with lots of BOOM and Sizzle, and he may think that sounds "good." (OP, please don't take offense. I am merely using your post as an example of the imprecise nature of subjective descriptions such as "sounds good.")
For that matter, we don't know *your*
definition of what "sounds good." AFAIK, you've never posted what your system(s) are comprised of, or how you have them set up. More importantly, you've never posted any measurements of your system(s) that I'm aware of. How are we to know what "good" sound means to you? The only thing I do know about your listening preferences is that you've stated that don't prefer to listen at "loud" levels. Once again, that's a subjective statement and we have no context of what "loud" means to you. You may be satisfied with 30 Hz extension, (similar to the LF extension in most movie theaters), and less than Reference Level output. If so, that's fine for you. However, this would cloud your judgement about how to set up multi-subwoofer systems for ultimate performance. We can make a lot of things work at modest levels. It's only when ask our systems to produce prodigious levels that real performance comes into play.
Non-identical subs can't possibly work as synergistically as identical subs at levels were an inferior sub would hold back the performance of a superior sub. It's simply not possible.
* Subs with different -3 dB points and roll-offs will have... (wait for it...) ...different -3 dB points and roll-offs.
* Subs with different maximum output limits will have... different maximum output limits.
* Subs with different distortion/compression limits will have... different distortion/compression limits.
* Subs with different transient responses will have... different transient responses.
Because non-identical subs will always have different performance characteristics, it will always be more difficult to integrate them into a "system".
For example... If you use a ported sub with a -3 dB point of 35 Hz, a roll-off of 24 dB per octave, a maximum output of 90 dB at 25 Hz and 10% THD at 25 Hz... in the same system with a sealed sub with a -3 dB point of 20 Hz, a roll-off of 12 dB per octave and a maximum output of 100 dB at 20 Hz, and 1% THD at 20 Hz, then the lesser, ported sub will clearly hold back the better sealed sub. You might be able to make the "system" work, and the sound might be "better" than the cheap, ported sub alone, but it will be nowhere near as good as the better, sealed sub would perform all by itself. The "system" might sound better up to about 93 dB, (or 3 dB above the limits of the lesser sub.) Beyond that, the "system" will be limited to the output/extension/distortion limits of the far inferior ported sub. You'll never be able to achieve the full output/extension of the better sub! Why bother getting a much more expensive sub and then hold it back with a cheaper, far inferior sub? In the same breath, why take the risk of destroying the lesser sub while trying to experience the output capabilities of the more potent sub?
If you use identical subs, they'll both have the same -3 dB point, the same roll-off below tune/resonance, the same maximum output, the same transient response, the same distortion/compression limits. Neither sub will hold the other back; in fact they will both add
to the "system" limits, which will be *higher*
than the individual limits of the individual subs. Neither sub will distort/compress before the other sub. (Of course, all this assumes that the user gain-matches and properly integrates the two identical subs.)
Bottom line... in a system where the subs are used at close to their performance limits, there is no way two non-identical subs can work as well as two identical subs, (at least not within any reasonable price/performance delta.). Even if the two non-identical subs are very close, one sub will always be inferior to the other sub in some aspect of performance, and it will hold the other sub back, and the overall system back, due to it's inferiority in that aspect.
You can claim all you want that you've made dissimilar subs work in various systems, but until you can post measurements that show the systems perform better with non-identical subs than with identical subs, and that the system limits are higher with non-identical subs, your claim is nothing more than your subjective opinion. That might work in the "Under $300" thread, but in the rest of the forum, we'll call BS.
Originally Posted by KidHorn
I don't see how having non matching subs is any different than having surrounds that aren't the same as the fronts or centers.
(No one ever claimed it was necessary to match the subs to your speakers, so I don't see how this comparison relates to using different subs together. The principles involved in this are completely different.)
Rather than comparing surrounds that don't match your front speakers, the better comparison would be mixing a different left surround with a different right surround. For example, let's say you used a dipole right surround and a monopole left surround. The timbre-match, dispersion, sensitivity and bass extension of the left surround would be completely different than the right surround. This might "work" in the sense that you would have "sound" from each surround speaker, but it would hardly be considered an optimal solution. Of course, the more similar the left surround is to the right surround, the "better" it will work, but nothing will beat matching the surrounds with identical speakers. Similarly, using non-identical subwoofers can "work", but due to different LF extensions, roll-offs and outputs, it is hardly an optimal solution. The ideal solution will always be matched, identical subwoofers being sent a matched, identical signal.
Originally Posted by KidHorn
Generally speaking, 3 subs will sound better than 2. It's more likely the third sub will even out the room response than it will cancel out the other subs.
Finally, something we can agree on... 3 identical subs will sound better than 2.
Now, whether 3 non-identical subs will sound better than two identical subs is a somewhat open question. IMO, for the most part, I don't think so, but some of it depends on the subs in question and it also depends on the ability of the integrator, the placement options and the room acoustics.
OTOH, whether 3 identical subs can sound better than 3 non-identical subs is not an open question. If the 3 identical subs are properly optimized, there is absolutely no doubt that their maximum potential is far higher than 3 non-identical subs.
To the OP:
If you are dead set on using three different subs together in one system, I suggest you try the technique of Geddes as related by Markus Mehlau: http://mehlau.net/audio/multisub_geddes/
If I were going to try to integrate 3 completely different subs into one system, that's the method I would use. Even at that, you'll need to be aware of the capabilities of the weakest sub in the group as it will be the limiting factor.
CraigEdited by craig john - 3/15/13 at 3:54pm