Is there such a thing as "box sound"?

[Keith_W]

People keep telling me that they like open baffle speakers because there is no "box sound", but every time I ask them what they mean, they can't tell me. And no, "other speakers sound boxy" is not an answer. I have heard answers such as "it sounds free" or "it doesn't sound constrained", etc. and then I ask them to point at a specific measurement that shows this. Nobody can do it.

I am looking for an answer that can specifically be attributed to a "box". I grant that boxed speakers have a different radiating pattern to open baffle / dipole speakers, but in that case it is better to say that you like "dipole sound" so that it is clear that it is the radiating pattern that someone is referring to. If you have an omnidirectional speaker in a box (e.g. Beolab 90), does it still sound "boxy"? Wouldn't it be better to simply say "monopole sound"?

Today, someone told me that they heard a pair of 18" open baffle subwoofers and said "it doesn't have a box sound, the bass is just there". Subwoofers are omnidirectional, so they can't have a "monopole sound". I asked him what he meant, and I didn't get a very satisfying answer.

Some have said that "box sound" might be caused by the rear wave reflecting off the enclosure and passing through the driver cone or interfering with driver movement, especially since I have heard claims that it can not be measured with a steady-state tone because somehow the cabinet reflection and driver movement are in equilibrium. That sounds like a nonsense made-up argument to me, but I am not so sure.

A more interesting argument is "low Q sound" vs. "high Q sound". Well, boxes can be tuned to different Q's. And drivers for open baffle speakers can be chosen with different Q's. I have been told that "low Q sound" sounds strained and muffled, but I don't have the experience of listening to high Q vs. low Q speakers. And: what measurement would show the effect of Q? Surely all you need to look at is the impulse/step response to see how long the driver rings for?

I am starting to think that "box sound" has no descriptive value, in the same way that "musical" is a useless term. I don't think people agree with what it means, and to the extent that boxes sound different to dipoles, it is better to specifically refer to the radiation pattern ("monopole sound") instead of "box sound". Or "high Q" vs. "low Q" sound. Am I wrong about this?

 

[wwenze]

Empty box = resonance from an empty box.

Open baffle is highly dependent on the user being in the "near region" to hear any semblance of bass. Also how would you have a pair of 18" subwoofers in a room. So I presume we are talking about big spaces, in which case the reflections or, again, resonance, this time of the bigger room. With open baffle the sound pressure of the bass disappears once you're some distance away from the baffle hence avoiding sending power to the rest of the room for that resonance.

Q is just mathematical. I only know the sound of the mathematical Q, so higher Q = higher peaks and narrow frequency. Possibly some people interpret it as "tight" or "one note" since all the energy goes to that frequency.

Or in summary, without proper definitions, it's all gibberish.

 

[ppataki]

I have no idea what they mean with that but personally I tend to hear speakers sound 'boxy' if the 100-300Hz region is dominant (= there is a peak there for whatever reason)
Especially around the 100Hz region it tends to 'hurt' my ears
Once correct DSP (EQ) is applied it goes away immediately

A more interesting argument is "low Q sound" vs. "high Q sound". Well, boxes can be tuned to different Q's. And drivers for open baffle speakers can be chosen with different Q's. I have been told that "low Q sound" sounds strained and muffled, but I don't have the experience of listening to high Q vs. low Q speakers. And: what measurement would show the effect of Q? Surely all you need to look at is the impulse/step response to see how long the driver rings for?

The frequency response will show that immediately; see:

Red is Q=0.5 (critical damping), orange is Q=1 (not ideal, cabinet is way too small)
This will have an impact on GD, IR and phase too - high Q value will sound like 'one note bass'

Personally I always go for the lowest possible Q when designing closed speakers (but avoid going below 0.5 as it does not make sense)
Btw. the classic 'textbook' Q value is 0.707 (so-called air suspension design)
However, if one uses adequate DSP this whole Q thing is really a non-issue (provided enough amp power is available for the compensation)

 

[voodooless]

I guess much of the "open baffle" sound comes from the fact that there is little bass to begin with, unless your woofers are truly massive, and you boost them to hell.

A more interesting argument is "low Q sound" vs. "high Q sound". Well, boxes can be tuned to different Q's. And drivers for open baffle speakers can be chosen with different Q's. I have been told that "low Q sound" sounds strained and muffled, but I don't have the experience of listening to high Q vs. low Q speakers. And: what measurement would show the effect of Q? Surely all you need to look at is the impulse/step response to see how long the driver rings for?

The Q of the box is really meaningless without the room. The room will basically dominate the Q (and frequency response). Looking at the one thing without the other is mostly pointless.

The frequency response will show that immediately; see:

Red is Q=0.5 (critical damping), orange is Q=1 (not ideal, cabinet is way too small)
This will have an impact on GD, IR and phase too - high Q value will sound like 'one note bass'

Well, this is highly dependent on the driver used and how much room you give it to breathe. If you have the same Q peak at 20 Hz instead of 200, there would not be much of an audible issue. You won't fit tractor tires on your Ferrari, unless it looks like this:

 

[DanielT]

I guess much of the "open baffle" sound comes from the fact that there is little bass to begin with, unless your woofers are truly massive, and you boost them to hell.

But with a fair amount of power handling and a woofer with high sensitivity, it is possible to EQ in an open baffle.

For example, this one:
SB Audience Bianco-15OB350
Which according to the manufacturer has:
Power Handling (RMS)
350 Watts
Power Handling (max)
700 W and 98 dB sensitivity.

BIANCO-15OB350

BIANCO-15OB350

www.sbaudience.com

Here is the Joseph Crowe's open baffle with measurements on them. If he starts from around 40 Hz, he can file down and smooth out FR above 40 Hz and get around 90 dB sensitivity. That's not bad for an open baffle, I think.

In the video, he also shows results of outdoor/distortion measurements.:

 

[voodooless]

But with a fair amount of power handling and a woofer with high sensitivity, it is possible to EQ in an open baffle.

High sensitivity won't help you much. It just saves you some power. You need an excursion, above all! Or make your baffles insanely wide, as in your last video, so you push the cancellation peak way down in frequency.

 

[DanielT]

High sensitivity won't help you much. It just saves you some power. You need an excursion, above all! Or make your baffles insanely wide, as in your last video, so you push the cancellation peak way down in frequency.

Which for me and probably most people makes it quite problematic to have such large wide speakers in a combined listening-living room.

But okay, if you have the space, why not.

 

[mhardy6647]

Had I more discipline, given the offset in technical knowledge & acumen 'twixt @Keith_W and me (in his favor!), I'd probably not offer a reply -- but given my lack of impulse control, I'm afraid that I will do so anyway.

It seems to me that the boxy colorations ascribed to... well... boxed loudspeakers may (carefully chosen weasel word) trace to enclosure (system) resonances and diffraction-related (?) anomalies in dispersion. I suspect (WW #2) that these issues call attention to the location of the loudspeaker in space resulting in opaque loudspeakers, as opposed to transparent ones.

EDIT: I offer as anecdotal evidence some of the most obviously opaque loudspeakers I've encountered in my six-ish decades of fiddling with this stuff: e.g., the Sansui "kabuki" designs putting too-large woofers in too-small boxes (sealed or ported), and many (most) of the once very popular Radio Shack (US) loudspeaker such as the, to my ears and taste, truly execrable Mach One (which also suffered from the big woofer/small box alignment disease).

I further suspect (WW hat trick! ) that the sins of a sinful loudspeaker system would probably manifest themselves analytically to a pair of ears by conducting a fairly slow frequency sweep. In fact, I suspect that people like me, who knowingly enjoy certain demonstrably colored-sounding loudspeakers, would be chagrined if not horrified to do that test on certain beloved models.

I will say that I've played around with open baffles quite a bit, albeit far from systematically, over the years ,and - so far -I've always gone back to enclosures of some sort for woofers.

Not sure if any of this helps, or is even contributory, but those are, for better or worse, my rather unscientific thoughts on the matter.

N.B. I have very little experience with "open baffle subwoofers", so I don't really have any opinions on them. The old rule of thumb would put high Qts drivers on open baffles to give a qualitative illusion of bass extension, but that's probably irrelevant to the modern crop of open-box subwoofers.

 

[RickS]

Which for me and probably most people makes it quite problematic to have such large wide speakers in a combined listening-living room.

But okay, if you have the space, why not.

maybe you want to stay married!

 

[voodooless]

Which for me and probably most people makes it quite problematic to have such large wide speakers in a combined listening-living room.

But okay, if you have the space, why not.

There are other options

Because it's about pathlength, so it doesn't have to be width. It can also be depth! Obviously, this will influence the directivity pattern (like all configurations do). Like these ones:

 

[HalSF]

I realize these issues are technical more than psychological, but it still seems that a non-trivial portion of the problem with speakers in an enclosed box-shaped cabinet sounding “boxy” is like silver speaker wire supposedly sounding “bright” — powerful subjective associative thinking.

 

[mhardy6647]

There are other options

Because it's about pathlength, so it doesn't have to be width. It can also be depth! Obviously, this will influence the directivity pattern (like all configurations do). Like these ones:

View attachment 513421
View attachment 513422

^^^ those look like prototypes for small scale nuclear fusion devices.

 

[terryforsythe]

what measurement would show the effect of Q?

Frequency domain:

Time domain:

 

[Keith_W]

The Q of the box is really meaningless without the room. The room will basically dominate the Q (and frequency response). Looking at the one thing without the other is mostly pointless.

That is true, but people talk about "boxy sound" well up in the frequency range, above the Schroder frequency. Here, the Q is no longer dominated by the room. The driver is effectively free-field, so the Q should purely be determined by Qms and Qes, shouldn't it?

It seems to me that the boxy colorations ascribed to... well... boxed loudspeakers may (carefully chosen weasel word) trace to enclosure (system) resonances and diffraction-related (?) anomalies in dispersion.

Re: the first point, enclosure resonances are a very minor part of the total resonance of a loudspeaker, unless the loudspeaker was incompetently designed. Some of those Audio Note speakers with deliberate flimsy cabinets made from exotic woods come to mind. I heard someone say that those speakers are designed "like musical instruments" Otherwise, in most normal loudspeakers, the resonances of a loudspeaker is dominated by driver resonance.

Re: the second point. Diffraction related anomalies are not absent in dipole speakers. Any driver mounted in a baffle will produce diffraction anomalies, as long as the wavelength is not "long" in relation to the baffle dimensions. So I don't think that this is an explanation for "boxy" sound.

I realize these issues are technical more than psychological, but it still seems that a non-trivial portion of the problem with speakers in an enclosed box-shaped cabinet sounding “boxy” is like silver speaker wire supposedly sounding “bright” — powerful subjective associative thinking.

Well put! This was the default position I had when I started this thread. But I thought I better check that I am not dismissing an actual real phenomenon first.

 

[voodooless]

That is true, but people talk about "boxy sound" well up in the frequency range, above the Schroder frequency. Here, the Q is no longer dominated by the room. The driver is effectively free-field, so the Q should purely be determined by Qms and Qes, shouldn't it?

You can't really see the upper range as an isolated component. Things happening in the bass can influence how you hear the midrange as well. Also, the higher frequencies do not interact with the box much. So "box sound" doesn't make much sense there.

Obviously, the directivity is different. That may be one of the things that can be audible. Also, additional reflections of the rear waves to the walls may yield a different sounding result.

 

[OCA]

People keep telling me that they like open baffle speakers because there is no "box sound", but every time I ask them what they mean, they can't tell me. And no, "other speakers sound boxy" is not an answer. I have heard answers such as "it sounds free" or "it doesn't sound constrained", etc. and then I ask them to point at a specific measurement that shows this. Nobody can do it.

I am looking for an answer that can specifically be attributed to a "box". I grant that boxed speakers have a different radiating pattern to open baffle / dipole speakers, but in that case it is better to say that you like "dipole sound" so that it is clear that it is the radiating pattern that someone is referring to. If you have an omnidirectional speaker in a box (e.g. Beolab 90), does it still sound "boxy"? Wouldn't it be better to simply say "monopole sound"?

Today, someone told me that they heard a pair of 18" open baffle subwoofers and said "it doesn't have a box sound, the bass is just there". Subwoofers are omnidirectional, so they can't have a "monopole sound". I asked him what he meant, and I didn't get a very satisfying answer.

Some have said that "box sound" might be caused by the rear wave reflecting off the enclosure and passing through the driver cone or interfering with driver movement, especially since I have heard claims that it can not be measured with a steady-state tone because somehow the cabinet reflection and driver movement are in equilibrium. That sounds like a nonsense made-up argument to me, but I am not so sure.

A more interesting argument is "low Q sound" vs. "high Q sound". Well, boxes can be tuned to different Q's. And drivers for open baffle speakers can be chosen with different Q's. I have been told that "low Q sound" sounds strained and muffled, but I don't have the experience of listening to high Q vs. low Q speakers. And: what measurement would show the effect of Q? Surely all you need to look at is the impulse/step response to see how long the driver rings for?

I am starting to think that "box sound" has no descriptive value, in the same way that "musical" is a useless term. I don't think people agree with what it means, and to the extent that boxes sound different to dipoles, it is better to specifically refer to the radiation pattern ("monopole sound") instead of "box sound". Or "high Q" vs. "low Q" sound. Am I wrong about this?

Never heard an open baffle but I am sure it has its merits given all of the spikes you see after the peak in the impulse graph below are "box" related and this is sort of a high end speaker:

 

[tineared]

 

[mhardy6647]

View attachment 513457

the quintessential lossy box.

 

[RickS]

Suggest the openness is more about speaker directivity as dipoles and omnipoles also tend to be considered less boxy too. Openness is not limited to open baffle speakers. Even some open baffles (most notably Linkwitz’s LX521) use a backfiring tweeter to even up dipole radiation.

 

[DanielT]

Speaking of baffles. The most well-known baffle in speaker circles is, guess which one it is:

Spoiler

What is a Frequency Response Chart? | Jensen Loudspeakers

www.jensentone.com