A Detailed Look at the Importance of Proper Loudspeaker Cabinet Bracing

[mtrycrafts]

Here is a quote (edited the first part out because it doesn't apply to this topic) from Dr. Sean Olive that I found applicable to this thread.

It looks like he was in a discussion with someone on a forum. Do you have that link? It be interesting to read.

[Nuance AH]

It looks like he was in a discussion with someone on a forum. Do you have that link? It be interesting to read.

Sure thing:

B&W Nautilus vs Sonus Faber Cremonas

I believe Dr. Olive chimes in around page 6.

[haraldo]

Perhaps my previous remark was a bit different than what I intended......

Something like 15 to 20 years ago Celestion made some top notch mini monoitors, they were very clean and revealing with a truly uncolored lively genuinely pleasing and natural sound, no trace of resonances and they could play quite loud without any sign of harshness or feeling of being pushed. Really made it enjoyable to listen to music through them.

I had the pleasue of attending a presentation by the chief designer of Celestion at that moment (I just don't remember his name) and this was very interesting, the design goals at that time was to make the cabinets as stiff and properly brased as possible and at the samt time minimize the weight of the cabinets as much as absolutely possible, in order to minimize the amount of stored energy that could be entered into the cabinet walls... The chief designers clear thoughts about this is that the less weight, the less stored energy and less ringing... When we talk about their speakers at the time is must have been working because the products were sensational :-D

[Nuance AH]

So if I understand all of these articles and studies correctly, am I wrong in taking away from them that the quality and/or amount of bracing, along with the proper placement of said bracing is extremely important while the thickness of the cabinet walls takes a back seat?

[haraldo]

So if I understand all of these articles and studies correctly, am I wrong in taking away from them that the quality and/or amount of bracing, along with the proper placement of said bracing is extremely important while the thickness of the cabinet walls takes a back seat?

I think it's not what's stated here.... both is extremely important.... thickness of cabinet makes panels stiffer, which decreases vibrations... so increased thickness and bracing works together in union

[Nuance AH]

I think it's not what's stated here.... both is extremely important.... thickness of cabinet makes panels stiffer, which decreases vibrations... so increased thickness and bracing works together in union

Then what of Dr. Olive's sources and their study/findings? I would, of course, prefer a proper combination of sturdy cabinet walls and bracing, but Lipshitz and Vanderkooy's findings suggest that we may be putting too much importance into it.

Here's a portion of his quote for reference:

"Lipshitz and Vanderkooy concluded that you could get away with loudspeaker cabinets that were relatively light-weight and flimsy as long as you had adequate bracing judiciously placed etc to make the resonances fall below their detection threshold. "

I don't know how long ago their testing was, but I'd love to see this subject re-tested by professionals such as Dr. Olive or Lipshitz and Vanderkooy using the most modern technology and tools. I imagine things have changed quite a bit since their findings... I appreciate what Audioholics' team has done here, so don't take my statement the wrong way. Applying such findings to how it correlates with human detection would be nice, though. Perhaps a "Part 2" could be completed?

[mtrycrafts]

...

I don't know how long ago their testing was, but I'd love to see this subject re-tested by professionals such as Dr. Olive or Lipshitz and Vanderkooy using the most modern technology and tools. I imagine things have changed quite a bit since their findings... I appreciate what Audioholics' team has done here, so don't take my statement the wrong way. Applying such findings to how it correlates with human detection would be nice, though. Perhaps a "Part 2" could be completed?

It seems they did it before 1988 when Tool published his paper you referenced above.
I searched AES for a paper by him but didn't see one if it was published or I just didn't see one that could be it.

Thanks for that link to Olive's posts.

It would seem to me that with more bracing and thinner walls the resonance frequency would be going up and most likely of reduced amplitude to place it below the thresholds of detection or perhaps out thresholds are higher with frequency of this nature?

[tonmeister]

It seems they did it before 1988 when Tool published his paper you referenced above.
I searched AES for a paper by him but didn't see one if it was published or I just didn't see one that could be it.

Thanks for that link to Olive's posts.

It would seem to me that with more bracing and thinner walls the resonance frequency would be going up and most likely of reduced amplitude to place it below the thresholds of detection or perhaps out thresholds are higher with frequency of this nature?

The Lipzhitz et al. paper "An Investigation of Sound Radiation by Loudspeaker Cabinets" was written in 1991 -- 3 years after Floyd Toole and I published our paper on the detection of resonances, "The Modification of Timbre by Resonance: Perception and Measurement"

In re-reading the Lipshitz paper they conclude that some of the cabinet resonances on the worst-case speakers may be audible or "borderline audible" on certain signals based on our predictions of audibility of resonances.

The audibility of a resonance depends on its amplitude, Q, frequency and the signal exciting it (steady-state versus transient). The audibility of a resonance at a given level increases as the resonant frequency increases, and the Q decreases. So shifting the resonance up in frequency and lowering its Q will increase its audibility -- all things being equal.

[gene]

The Lipzhitz et al. paper "An Investigation of Sound Radiation by Loudspeaker Cabinets" was written in 1991 -- 3 years after Floyd Toole published our paper on the detection of resonances, "The Modification of Timbre by Resonance: Perception and Measurement"

In re-reading the Lipshitz paper they conclude that some of the cabinet resonances on the worst-case speakers may be audible or "borderline audible" on certain signals based on our predictions of audibility of resonances.

The audibility of a resonance depends on its amplitude, Q, frequency and the signal exciting it (steady-state versus transient). The audibility of a resonance at a given level increases as the resonant frequency increases, and the Q decreases. So shifting the resonance up in frequency and lowering its Q will increase its audibility -- all things being equal.

That assumes the amplitude remains the same which it doesn't as can be seen in David's analysis when adding more braces. You also need to look at more than a single point on the cabinet to see how the resonance modes change when stiffening is added.

Aside from simulations and analysis, I know from personal experience that I've never heard a boomy speaker that was well braced but I have heard many boomy speakers that had little to no bracing in them.

[lsiberian]

That assumes the amplitude remains the same which it doesn't as can be seen in David's analysis when adding more braces. You also need to look at more than a single point on the cabinet to see how the resonance modes change when stiffening is added.

Aside from simulations and analysis, I know from personal experience that I've never heard a boomy speaker that was well braced but I have heard many boomy speakers that had little to no bracing in them.

I think the real question and one I want answer is how much bracing is enough to be high quality sound. Wood may be cheap, but simplicity in construction is always preferred over complexity that nets no audible benefits.

David's Analysis is helpful for addressing the effects of bracing on a cabinet in a pure motion sense. What is the audible threshold when adding another brace makes no audible difference?