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Unused Speakers (subwoofers) In Listening Room...

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I've read in the past....now I'm having trouble finding this info....that having unused speakers/subwoofers in your listening room will resonate and possibly have an effect on your sound.

 

If I recall correctly... ported, unused speakers were more susceptible to this because the bass from your speakers/subwoofers that are in use will creep into the unused enclosures and the woofers will resonate.

 

In my case, I have two different sets of subwoofers that I switch back and forth with. The ported 18" subs when not in use are clearly vibrating when I put my hand on one of the woofers. Feels just like it's on....not thumping away....but vibrating even at low volumes 65-70db.

 

I'm wondering that if this is actually detrimental to the sound, would it be worthwhile to plug the ports or do something else. Removing them is obvious but like I said I frequently like to switch subs because I'm mental when it comes to bass.

 

Thanks!

 

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Everything will vibrate. Drywall, windows, doors. I can't see how an unused sub would be any more detrimental.

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....because it's a ported enclosure designed to make sound.

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They will resonate.  How much is a question of location in proximity of other low bass producing speakers.  For the most, it is not detimental.  My Fortes did this located next to my subs.  It may effect setup in autocalibration to a slight extent.  I don't know if plugging the ports makes a big difference.  Sealed boxes will also resonate as mention, everything in the room has a resonant frequency.

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Yeah, they definitely resonate. It's just a question of how audible is the resonating and how much is it actually affecting the sound quality.

Bass is tough. It's harder to discern what it's doing compared to the mids and highs.

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I plugged the ports.....gonna do a little experimenting.

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I guess another way to rephrase my question would be "is the unused cab making bass?" Also, is this a good thing, bad thing or doesn't make a difference?

 

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Most likely, the passive resonant frequency is 20-30 db less than the sound from the active speakers and is not very audible.  All this depends on how picky we are.  Some people on the forum claim to be able to here a subwoofer with 1% vs 2% distortion.  I don't believe it but, I can't tell anyone what they can and can't hear.  I just glad that I fit more in the normal hearing range and can't detect those small of differences.  95% of us are in the normal hearing range.

 

Is the unused box making bass. Sure but, is it audible?

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My guess is that at low to moderate listening levels it will not be discernable until you get north of say 85 to 90db's.....but that's just my uneducated guess.

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It could be analogous to seeing a flock of eagles coming to attack you with a humming bird in the mix.  

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On the other hand, these are large cabs with two 6" ports in each and are only 11 feet from the sweet spot.

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It could be analogous to seeing a flock of eagles coming to attack you with a humming bird in the mix.  

 

 

Yeah but that could be one bad a$$ humming bird hanging with all those eagles.

 

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I always give credit for the guys chasing a zebra and being stampeded by horses.  It may be one bass A$$ bird but, most like is not the cause of a major problem and the time spent is better focusing on more obvious causes.  What are you detecting while playing music vs movies?  You must be detecting something that is clearly audible.

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At low volumes I'm not detecting anything. Like I said in the OP, there was a thread on this that I cannot find. This thread is not because I have an issue but more for conversation....like most threads here. If I eventually find it on Audiokarma I will post it here.

 

As far as the humming bird goes, sometimes it's the little things that make a bigger difference that you might think....or hear. Bass is tricky.....if you can hear it. Or I should say if you can hear what it's doing to the system as a whole.

 

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EVERYTHING resonates.  Everything.  The presence of a port is also irrelevant.  A sealed woofer also resonates at the frequency dictated by the mass of the cone and the spring rate of the woofer's suspension and the air trapped behind it, just like the ported system resonates at the frequency dictated by the mass of the cone, the mass of the air in the port and box and the spring rate of the cone's suspension.  

 

The likely thing to happen is the unused subwoofer will absorb energy at its resonant frequency and it will be unmeasurable in the room's response. 

 

Why let it go unused?  Multiple subs in different places evens out the bass response throughout the room.  Mulitiple Subs - Number and Locations.pdf

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Why let it go unused?  Multiple subs in different places evens out the bass response throughout the room.



Thanks John, you are correct. Been there done that. In this case, my horn loaded subs are far superior so mixing them with the other subs doesn't make much sense.

Well, this conversation is quite a bit different than the one on Audiokarma that I can't find on my phone. That one emphasized that although 'everything in your room resonates', a speaker enclosure resonates MORE. A lot of it made sense to me but wanted to get opinions here.

I'm not gonna sweat it. I've got killer bass and I'm content. Just curious what others thought about this. Thanks for all the input.


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I doubt if the sympathetic vibrations of your subs will make any difference.  About 30 t0 40 years ago, the Linn company floated the rumor that any diaphragm in the room -- from speakers down to the tiny diaphragms in telephone receivers would make the sound worse, and make it hard to sing along with the music, as well.  Therefore, they said, no other speaker should be in a dealer's showroom where a Linn speaker was being demonstrated.  Highly convenient, I'd say. 

 

I think we can consign the idea that vibrations from unused speakers affect the quality of reproduction to the factoid pile, as Norman Mailer first defined a factoid -- something that seems to be a fact, but isn't. 

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In discussions with MikeTN (mikebse2a3) on this subject, he once stated that in an audio store showroom where he once worked that was typically room filled with loudspeakers, it was the decay times seemed to be enhanced--like using an amplifier with very high output impedance or perhaps dipole loudspeakers spaced away from the front wall.  The delayed, very low level vibrations that were present vibrated in sympathy to the main loudspeaker's acoustic output, and added apparent depth and spaciousness to the Khorns and/or Belles, etc. that were active and playing music at the time. This was apparent only after the high SPL peaks that excited the freely suspended diaphragms--mostly woofers (one would think).   This also includes contributions from midrange horns/drivers and passive radiators, perhaps ported boxes--although I believe that reversing the action of the surroundings around the port/box system isn't terribly efficient.

 

I've thought about this comment many times as it also corresponds to my experiences with dipoles and other sympathetically vibrating surfaces, not really "resonance" in the strictest sense, since most loudspeakers are sufficiently damped to preclude the classic "resonance effect".  This is like "the room feeling the loudspeaker vibrations" that Bob Carver once alluded to.  These are very low level--about -40 dB down from the amplitude of the main acoustic impulses arriving at the freely suspended but damped diaphragms.  The same thing is happening (I believe) with higher bit depth digital recordings--which present a more precise decay response that is indicative of the original recording space.  This has been discussed by others that have listened to original tapes vs. 44.1 kHz/16 bit CD recordings.  The differences are all in the quality of the original space decays that are reproduced by the loudspeakers.  Of course, this effect disappears in listening rooms that have not been acoustically treated properly and that experience very large reverberation times (i.e., RT60). 

 

When you think about the situation in context of large auditoriums, first without people filling the seats, then with people, you get an idea of the effect that most of us have experienced, albeit in the auditorium case--the time delays of decays are 10x or more delayed than in a small room that we typically call our listening room--like we are listening in a cave. 

 

I've experienced this effect in auditoriums that was so pronounced that I felt profoundly disoriented (hearing-induced) while playing in a wind ensemble on stage.  I apparently sat in a peak audience reflection position on stage when the auditorium was empty of people, whereby the returning echoes were reinforced back to my ears and created an enhanced sense of depth to the instruments playing on stage, that is, until there were people sitting in all of those seats, absorbing much of that returning sound.  I felt like I was about 6" high sitting on stage, with the sensation of sitting in a vacuum when the curtain opened and we began to play.  This effect was enhanced due to childhood synesthesia--which is actually a sensory integration disorder.  I've learned to live with this effect, but I've learned that most other people don't experience it.

 

Returning to your original premise: I'd think about the size of the subwoofer diaphragm vs. the open wall spaces, windows, and things like bookcase backs, then you can decide for yourself if you can detect the smallish 15" or 18" woofer diaphragm vibrating in sympathy on the decays. 

 

Chris

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They are acting like passive radiators and will have no dostortion at all but will add a bit of spl.  Norhing negative at all imo.  If you run surround sound but only the center is playing....everything else is still vibrating along w the center albeit a very small amount.   

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