Two pairs of the speakers in the same room - is it a problem?

[SlowCar]

Hi all,

as many of You I am considering best of two worlds - HiFi and HT - in the same room. One of options is to set up 2 completely separate systems. The question is, if there is something wrong with putting 2 pairs of speakers side by side? I think that I have read somthing about why it's a bad idea but I can't find those information now.
Picture below shows what I have in mind.

 

[Danaxus]

You might have trouble getting the speaker positions exactly as you want them, as you'll have other speakers taking up space. I don't have any experience doing that, so not sure how much so many blocks of mass will affect first reflections.

If it were me, instead of getting 2 pairs of speakers, I'd rather get 1 much nicer pair of dead neutral ones (or perhaps a really nice subwoofer or two), then EQ the hell out of it to get the desired effect. That said, if it's what you want to do, go right ahead! If it's calling to you, I'm sure you'll enjoy it, regardless of the compromises.

 

[hex168]

Speaker crossovers are designed for a specific baffle width (this is called baffle step compensation if you care to search). Above a frequency that depends on the baffle width, the speaker radiates into half space, and below that frequency into full space. This cases a gradual 6dB rise above that frequency.

Two speakers next to each other would have a wider effective baffle than one speaker, changing that transition frequency. A flat speaker will no longer be flat. This would likely be EQable.

In addition, diffraction occurs at the baffle edges. The crossover would be designed to take this into account to some degree. With speakers next to each other, diffraction effects will be different than what was anticipated in the design.

Of course, the same effects occur when you place a speaker next to anything.

 

[AdamG]

Any decent pair of speakers should do both tasks equally well. Listening to music using only 2 channels and incorporating a center speaker for movies. Most modern AVR’s will accommodate settings for both situations. Unless I’m missing something important that makes you want different speakers for these tasks?

 

[abdo123]

Anything other than the speaker floating in the air in 3-dimensional space will have an influence on the sound.

So yeah the answer is yes, what you want to do with that information is up to you.

 

[Bugal1998]

Hi all,

as many of You I am considering best of two worlds - HiFi and HT - in the same room. One of options is to set up 2 completely separate systems. The question is, if there is something wrong with putting 2 pairs of speakers side by side? I think that I have read somthing about why it's a bad idea but I can't find those information now.

I can't speak to problems other than possibly sub-optimal location, or interference with reflection points.

I'd vote for putting the money for two systems into one superior system and have better sound for both experiences (that's what I did).

I'll be able to easily move the speakers between the optimal surround position and two channel position with ease.

If you're set on two sets of speakers you could put them on a turntable (back to back) so you simply rotate the set in use to the ideal location. Or if one set needs to be in front of the other set, put the offending set an a rail system to slide them out of the way.

Or put them both on sliders with markers so you can easily move them.

Or just get one set of great speakers. Good luck!

 

[Ken Tajalli]

Speakers use their cabinets, ports or transmission lines to boost the bass output at the point, where the output of the driver diaphragm is loosing effective ity.
Consider a pair of speakers as Drums! if you tap the diaphragm, it generates a sound. The frequency of that sound is tuned by the designer to have a fundamental at a certain frequency, unique to that speaker. Different speakers, create sounds (if the diaphragm is excited in any way) of different fundamental frequencies.
Here is our problem!
- The unused-speaker's diaphragm gets excited by the sound of the music-playing speaker. What does it do? it generates the said tuned-frequency, which will get mixed up with the sound of the active speaker, distorting its sound! Actually a drum in the room, acts in a very similar manner.
There is one method, hifi dealers minimize this effect. That is by short-circuiting the terminals of inactive speakers. This uses the back-emf of the diaphragm-coil to dampen the effect.

 

[Vladimir Filevski]

as many of You I am considering best of two worlds - HiFi and HT - in the same room. One of options is to set up 2 completely separate systems.

Instead of purchasing 2 pairs of speakers, for the same amount of money buy only 1 pair (presumably better). One good pair of loudspakers will handle both HiFi and HT duties easily.

 

[fpitas]

I'm hoping for a Thunderdome outcome here.

 

[Dumdum]

Get an AVR with pre outs and use the f l+r into a power amp if you wish, then use a preamp or dac with volume to also go into the power amp, one real nice set of speakers in the optimum position via two sources

Or just get a really nice AVR and stereo mode

I use a 3700 and some Dali floorstanders for a decent stereo image, i prioritise the stereo aspect as the movie side is less finicky with centre speakers etc

 

[abdo123]

Speakers use their cabinets, ports or transmission lines to boost the bass output at the point, where the output of the driver diaphragm is loosing effective ity.
Consider a pair of speakers as Drums! if you tap the diaphragm, it generates a sound. The frequency of that sound is tuned by the designer to have a fundamental at a certain frequency, unique to that speaker. Different speakers, create sounds (if the diaphragm is excited in any way) of different fundamental frequencies.
Here is our problem!
- The unused-speaker's diaphragm gets excited by the sound of the music-playing speaker. What does it do? it generates the said tuned-frequency, which will get mixed up with the sound of the active speaker, distorting its sound! Actually a drum in the room, acts in a very similar manner.
There is one method, hifi dealers minimize this effect. That is by short-circuiting the terminals of inactive speakers. This uses the back-emf of the diaphragm-coil to dampen the effect.

I always thought the exact opposite would happen and the extra speakers would act like Helmholz resonators and absorb bass frequencies.

 

[Boris Badinov]

Are you thinking of using 1 pair for music and the other pair for HT?

 

[MaxwellsEq]

This was a hot topic in the 80s. Linn insisted you should only have one set of speakers in the room at a time. They even considered that the TV speaker interacted with sound negatively, as did the earpiece on the telephone!
There is actually some engineering logic to back them up. Their argument was the other speakers "played along" with the main speakers, but in an out of control manner, disturbing timing.
Aside from whether this is true or not, moving a properly located speaker by a few centimetres can change interaction with room nodes, so there is probably one "best" location per speaker, in which case, the other speaker will be in a suboptimal location.
The best approach is to have a single good pair.

 

[gnarly]

Speakers use their cabinets, ports or transmission lines to boost the bass output at the point, where the output of the driver diaphragm is loosing effective ity.
Consider a pair of speakers as Drums! if you tap the diaphragm, it generates a sound. The frequency of that sound is tuned by the designer to have a fundamental at a certain frequency, unique to that speaker. Different speakers, create sounds (if the diaphragm is excited in any way) of different fundamental frequencies.
Here is our problem!
- The unused-speaker's diaphragm gets excited by the sound of the music-playing speaker. What does it do? it generates the said tuned-frequency, which will get mixed up with the sound of the active speaker, distorting its sound! Actually a drum in the room, acts in a very similar manner.
There is one method, hifi dealers minimize this effect. That is by short-circuiting the terminals of inactive speakers. This uses the back-emf of the diaphragm-coil to dampen the effect.

Yes, exactly. Unused speakers definitely resonate ....how much, and how audible surely a complex subject.

I do alot of multi-way DIY speaker building, and have found it's imperative to short out drivers not being measured, to get valid measurements of the driver being tested.
For instance, even a compression driver must be shorted to keep from mucking up a 12" low/mid.

Of course, this "drivers effecting each" other phenom is stronger in the same speaker, than with adjacent speakers, but it is still surprisingly stronger between larger cones.
For kicks one day, i used one 18" sub to play music and pink noise loudly, and another of the same 18" sub as a microphone, hooking its terminals up to a soundcard and voltmeter.

The 'sub as microphone' put out a full 1 volt output ! (when i blasting away with the playing sub!
1 volt input on that sub equals an 87dB output !!! So yes, they resonate

 

[abdo123]

I do alot of multi-way DIY speaker building, and have found it's imperative to short out drivers not being measured, to get valid measurements of the driver being tested.
For instance, even a compression driver must be shorted to keep from mucking up a 12" low/mid.

Why would you do that if the end product has both drivers working at the same time?

 

[Bugal1998]

Yes, exactly. Unused speakers definitely resonate ....how much, and how audible surely a complex subject.

I do alot of multi-way DIY speaker building, and have found it's imperative to short out drivers not being measured, to get valid measurements of the driver being tested.
For instance, even a compression driver must be shorted to keep from mucking up a 12" low/mid.

Of course, this "drivers effecting each" other phenom is stronger in the same speaker, than with adjacent speakers, but it is still surprisingly stronger between larger cones.
For kicks one day, i used one 18" sub to play music and pink noise loudly, and another of the same 18" sub as a microphone, hooking its terminals up to a soundcard and voltmeter.

The 'sub as microphone' put out a full 1 volt output ! (when i blasting away with the playing sub!
1 volt input on that sub equals an 87dB output !!! So yes, they resonate

Genuine question… wouldn’t the 87db output into the microphone input mean the energy is being removed from the room?

 

[gnarly]

Why would you do that if the end product has both drivers working at the same time?

Don't mean to veer off topic, but the answer is the best way to tune an active multi-way is to first tune each driver/passband individually.
Which requires shorting out the other drivers.
Shorting them out makes them act like they are connected to an amp, where their resonances are damped. This better replicates the state all the drivers will be in when working together.

Alternative to shorting out unused drivers, is to leave unused hooked to an amp turned on, but with no signal.
Would work for OP's side by side scenario too. Probably the easiest way to hear if it matters....

 

[abdo123]

Don't mean to veer off topic, but the answer is the best way to tune a active multi-way is to first tune each driver/passband individually.
Which requires shorting out the other drivers.
Shorting them out makes them act like they are connected to an amp, where their resonances are damped. This better replicates the state all the drivers will be in when working together.

Alternative to shorting out unused drivers, is to leave unused hooked to an amp turned on, but with no signal.
Would work for OP's side by side scenario too. Probably the easiest way to hear if it matters....

I didn’t know that, thank you.

 

[gnarly]

Genuine question… wouldn’t the 87db output into the microphone input mean the energy is being removed from the room?

Sorry i wasn't clearer about the experiment.
The sub that was being used as a microphone was just for the purpose of seeing how much voltage output it would produce when excited by another sub.
(Like a passive radiator, but one that has a voice coil...)
So the 87dB output, or rather the 1 volt output, wasn't being fed back into electrical signal. The energy was solely acoustic resonance and I have no clue how it interacted in the room with the primary (real) sub's acoustic output.

 

[gnarly]

I didn’t know that, thank you.

You bet, and you're very welcome