• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

"Too many speakers" in a small room

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
? What does this even mean? The literal size of the speaker?
I think what it really means is:

If you accept the premise that speaker manufacturers measure/setup/tune their speakers in an anechoic or quasi-anechoic method,
then they are no doubt doing so in the far-field, (where measurements need to be as per a couple of links in my last post.)

So this is where all the driver(s) EQ's, xover design, directivity matching, etc, took place..
And is where the speaker is designed to work best.

That minimum distance mic-to-speaker, that gets into the far-field, can most often be approximated by 3X the largest speaker dimension.

The minimum far-field distance is where all frequencies begin to attenuate at -6dB per doubling of distance, and continue to do so with greater distance.
So any listening distance further than the 3X r.o.t is hearing the speaker as it was designed, and as it measures..

(1m response curve specs are simply mathematical adjustments to measurements made in the far-field, unless the speaker is truly small enough to measure accurately at 1m)

I know how often folks talk about trying to recreate what the artist intended....
how about what the speaker manufacture intended ? Lol
Because any listening distance closer than the onset of far-field can't be such !
 

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,425
Likes
7,941
Location
Brussels, Belgium
? What does this even mean? The literal size of the speaker?

One 'rule of thumb' I know of is to place the MLP about 2/3-3/4 of the distance from the front wall (aka 1/3-1/4 from the rear wall). This is based on room mode characteristics of 'typical' rectangular rooms. AFAIK it has naught to do with the 'dimension of the speaker'.

Placement of the front speakers themselves is usually recommended to be an equilateral triangle (though certainly not absolutely required IME) , mindful of boundary effects on bass (though these can be either exploited, or can be corrected by room EQ) , and rear speakers of a 5.1 system placed circa 110 degree angle wrt MLP. These are only guidelines. Actual room measurements and use of e.g. REW would of course be even better.

Having an elaborate surround setup can work fine as long as you have an AVR that does good distance compensation and room (i.e. speaker) EQ, and good subwoofer placement. And the more point sources you have firing direct at you, the more the room is masked.

I like to use a set of audio test signals that locate left, center, right, half left, half right, side midpoints, left rear, right rear, right center etc, to fine tune position and aiming of speakers for accurate imaging.

Lets say a speaker is 30*20*40 cm big, then you need to sit at least 120 cm away from it.
 

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
These are all encompassed in one way or another with Speaker size.

Speaker size only indicates something about the baffle step frequency. It indicates nothing reliable about radiation pattern or interdriver spacing or crossover frequency. Of course it helps to know something about the ear's angular resolution in the vertical plane at the crossover frequencies too.

I used to make a stand-mount speaker that was 53 cm tall by 30 cm wide by 38 cm deep. What does that tell you about the radiation pattern, interdriver spacing(s), or crossover frequency(s)? Does it even reliably predict the baffle step frequency? Feel free to make some predictions based on the speaker's size.
 
Last edited:

abdo123

Master Contributor
Forum Donor
Joined
Nov 15, 2020
Messages
7,425
Likes
7,941
Location
Brussels, Belgium
Speaker size only indicates something about the baffle step frequency. It indicates nothing reliable about radiation pattern or interdriver spacing or crossover frequency. Of course it helps to know something about the ear's angular resolution in the vertical plane at the crossover frequencies too.

I used to make a stand-mount speaker that was 53 cm tall by 30 cm wide by 38 cm deep. What does that tell you about the radiation pattern, interdriver spacing(s), or crossover frequency(s)? Does it even reliably predict the baffle step frequency? Feel free to make some predictions based on the speaker's size.

The thing is a baffle is bigger than any horn that may be on it and is longer than any driver distance the speaker has because at the end of the day the drivers will have to take space on the baffle.

So I don’t see how a particular distance would be enough for the baffle but not the other thing you mention.
 

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
The thing is a baffle is bigger than any horn that may be on it and is longer than any driver distance the speaker has because at the end of the day the drivers will have to take space on the baffle.

And I think that the specifics are FAR more useful than this particular "rule of thumb".

For instance, this is how you fit a 12" woofer and a 12" horn into an 11" wide enclosure:

Gamma.jpg


Having taken a single quick look at the specific design, NOW you can make an educated guess about radiation pattern, crossover frequency, interdriver spacing, and baffle step!

As for interdriver spacing, which (along with crossover frequency) plays a role in predicting the minimum distance for coherent driver blending, speaker dimensions do not tell you anything about whether or not the speaker is a coaxial.

Nor do the speaker dimensions tell you much about how the designer juggled the tradeoffs between optimizing for farfield conditions (where the baffle step is no longer in play but any compensating EQ certainly is) versus nearfield or transition zone conditions (where the baffle step is in play to a greater or lesser degree).
 
Last edited:

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
Speaker size only indicates something about the baffle step frequency. It indicates nothing reliable about radiation pattern or interdriver spacing or crossover frequency. Of course it helps to know something about the ear's angular resolution in the vertical plane at the crossover frequencies too.
Hi, i don't think that's true. In fact, i'd say the 3X r.o.t. has much less to do with baffle step frequency than inter driver spacing issues.
(Plus, there isn't a single baffle step frequency...each driver has it's own "baffle ramp" relative to the mount surrounding it ( ramp...my new term..i've always hater the term step lol)

IMO, the 3X longest speaker dimension r.o.t. is completely about inter driver spacing issues, and how long the summation of those driver spacings take to settle down into phase coherency. I think adbo123's 'end of the day summary' hit's at the guts of it.
 
Last edited:

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
Hi, i don't think that's true. In fact, i'd say it has much less to do with baffle step frequency than inter driver spacing issues.
(Plus, there isn't a single baffle step frequency...each driver has it's own "baffle ramp" relative to the mount surrounding it ( ramp...my new term..i've always hater the term step lol)

Baffle size tells you almost nothing about the actual interdriver spacing, aside from putting an upper end on the reasonable possibilities.

IMO, the 3X longest speaker dimension r.o.t. is completely about inter driver spacing issues, and how long the summation of those driver spacings take to settle down into phase coherency.

Nope. In addition to interdriver spacing, crossover frequency and even crossover slope come into play in driver summation. Baffle dimensions do not.

I also made a floorstanding speaker which used the same drivers and same spacing and same baffle width and same crossover frequency and slope as the one in the photo in post #25. Do you really think the distance for the drivers to sum correctly was TWICE as far because that speaker was TWICE as tall?

It is the SPECIFICS which matter, not a rule of thumb which is only a good predictor in some cases, and which does NOT directly correspond with the factors which ARE determinative.

"If you assume things are true by convention, which is actually what most people do, then it's difficult to gain insight into how things might be bettered." - Elon Musk

Don't let rules of thumb become the boxes you cannot think outside of.
 
Last edited:

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
Baffle size tells you almost nothing about interdriver spacing
Well, the 3X r.o.t. does come from prosound circles, where keeping inter driver spacing to a minimum is always an objective.
Nope. Crossover frequency and even crossover slope come into play.

I also made a floorstanding speaker which used the same drivers and same spacing and same baffle width as the photo. Do you really think the distance for the drivers to sum correctly was TWICE as far because that speaker was TWICE as tall?

So I can see where you don't see the 3X r.o.t. ....cause home audio often does things in pursuit of aesthetics....(at odds with acoustics)
And no, of course the 3X speaker dimension wouldn't hold for a taller box like you describe with the same driver spacing as the shorter one.
It is the SPECIFICS which matter, not a rule of thumb which is only a good predictor in some cases.

I think it's a decent, fairly well known, and time-respected rule of thumb, for speakers that don't have excessive size vs their drivers, which like you illustrate isn't always the case in home audio.

I don't think xover frequency and slope come into play that much, w.r.t. the distance a speaker transitions into the far-field.
because I think both of those are determined by the acoustic design, which reflects driver sizes chosen, and their spacing. Which again will generally tie to speaker size.
 

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
I don't think xover frequency and slope come into play that much, w.r.t. the distance a speaker transitions into the far-field.
because I think both of those are determined by the acoustic design, which reflects driver sizes chosen, and their spacing.

The onset of the "far-field" and the distance "where the drivers blend well" are two different things.

Where the acoustic "far-field" starts is where the reverberant field (or reflection field if we're talking about small rooms) surpasses the net energy of the direct sound. This is not the same thing as the distance where the drivers perceptually blend into a coherent single voice.

The distance where the far-field begins has to do with the direct-to-reverberant sound ratio, which in turn is a function of loudspeaker directivity and room acoustics.

The distance where the drivers perceptually blend does depend in part on the crossover frequency because the ear's vertical angluar resolution peaks around 4 kHz, declining slowly as the frequency goes up or down from there, then declining rapidly below about 1.5 kHz (as I recall). Controlled blind listening tests have shown that the ear tends to mis-judge high frequencies as coming from a HIGHER angle than they actually do, and to mis-judge low frequencies as coming from a LOWER angle than they actually do. So putting the tweeter BELOW the woofer (like in the Buchardt models with the waveguide) makes sense psychoacoustically if not aesthetically because it serves to DECREASE the distance at which the relatively-widely-spaced woofer and tweeter blend well.

As for crossover slope, first-order crossovers are far more sensitive to listener height relative to the designed-for vertical axis height, assuming a non-coaxial configuration. So if your ears are not going to be in the designed-for vertical plane, you might want to avoid first-order crossovers.
 
Last edited:

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
The onset of the "far-field" and the distance "where the drivers blend well" are two different things.

Where the acoustic "far-field" starts is where the reverberant field (or reflection field if we're talking about small rooms) surpasses the loudness of the direct sound. This is not the same thing as the distance where the drivers perceptually blend into a coherent single voice.

The distance where the far-field begins has to do with the direct-to-reverberant sound ratio, which in turn is a function of loudspeaker directivity and room acoustics.

Ahh...i see the source of our crossed paths...

My training:

is that Near-field and Far-field are not about in-room response.
Those terms, when used for measuring speakers, refer to when phase has settled down and a speaker begins to obey inverse square law distance.
I'd point to the Klippel link again.

And In-room response is better characterized by direct field and reflected field.
The direct field ends and the reflected field begins at the distance where the two are equal. And is termed the critical distance.

I also think it is implicit that manufacturers' measurements are far-field measurements (or damn well should be ! )
I mean, far-field is what the Klippel NFS is putting out, after it does it's math.
 

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
Ahh...i see the source of our crossed paths...

My training:

is that Near-field and Far-field are not about in-room response.
Those terms, when used for measuring speakers, refer to when phase has settled down and a speaker begins to obey inverse square law distance.
I'd point to the Klippel link again.

And In-room response is better characterized by direct field and reflected field.
The direct field ends and the reflected field begins at the distance where the two are equal. And is termed the critical distance.

Yup, I think you found it! My apologies for not catching that distinction between our different usages of terms, but now what you have been saying makes sense to me. Gnarly-good job!
 

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
Yup, I think you found it! My apologies for not catching that distinction between our different usages of terms, but now what you have been saying makes sense to me. Gnarly-good job!
Thank you Duke, kind words.
I appreciate the knowledge and patience you bring to the forum!
 

ABall

Senior Member
Forum Donor
Joined
Jan 5, 2020
Messages
329
Likes
159
Location
Reading (UK)
I've read that having "too many speakers" in a small room can cause audio related issues even if they are correctly positioned in the room. Is this true? If I recall correctly, it was something along the lines of "too much sound energy" for the room to handle or something.

For example, would a correctly placed 9.4.6 setup in a 12 x 10 x 9.5 ft room cause "issues" even if the angles and other attributes are done to recommendations?
I think some people get too hung up on recommendations sometimes, TV size is a classic. From the list you made it appears that you already have the speakers in situ? So, do you have a problem or are you worried there is a problem because you read there would be one? I have a typical UK room, 12x12 ish and I have 7 large floor standing speakers, 2 of these are in a bay window right up close to the sofa where I sit and 2 aren't far from its ends, I don't think I'm following those recommended rules but I love the sound from my system, my advice, if you are enjoying it then don't worry, the alternative is probably a world of pain.
 

Duke

Major Contributor
Audio Company
Forum Donor
Joined
Apr 22, 2016
Messages
1,523
Likes
3,745
Location
Princeton, Texas
Thank you Duke, kind words.
I appreciate the knowledge and patience you bring to the forum!

Thank YOU sir!

I also think it is implicit that manufacturers' measurements are far-field measurements (or damn well should be ! )
I mean, far-field is what the Klippel NFS is putting out, after it does it's math.

For us little guys who don't have a Klippel NFS system there are work-arounds, but having access to the Klippel throughout the design phase would be ideal.
 

gnarly

Addicted to Fun and Learning
Joined
Jun 15, 2021
Messages
992
Likes
1,390
For us little guys who don't have a Klippel NFS system there are work-arounds, but having access to the Klippel throughout the design phase would be ideal.
For sure !!
I'm an even littler guy yet, as all i work on are my DIYs.

Best work-around I've found is measuring outside off a 2nd floor deck that points into fairly open space....so comparatively reflection free.
A little over 3m measuring distance is about as far as i can keep a mic boom stable though....wish I could get a little further.
Still, i feel i get decent far-field spinoramas out of the setup.

One consoling thought for me about work-arounds vs Klippel, is that the higher freq resolution that's often touted as necessary, is available with either, when care is taken.
That said, I don't find 1/20th- 1/24th octave measurements all that valuable because who knows if the anomalies are minimum phase and can be legitimately acted on with EQ.
For finding resonances, I like slow sine sweeps still, where there's simply no denying when they want to sing along Lol

To OP: sorry if this has drifted off topic... but i do think the point abdo123 first raised about needing to be in the far-field for best speaker performance, has a lot of merit.
 
Top Bottom