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post #151 of 337 Old 02-16-2016, 05:46 AM
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Originally Posted by Augerhandle View Post
I didn't get the context and go on a tangent
1db has to do with the difference between stuffed (example polyfil) quite a bit and not stuffed as much. Not the internal volume. That's what I referred to as having 1db easy gain in a dual enclosure setup. Pay attention!
But furthermore, the gain is that you don't have to guess how much bracing you need. You don't guess how much power you need, you don't guess anywhere in your build, except when it comes to the bracing. The tune is set in stone, you argue nine million hours about how much pillow-stuffing is correct and where to place it, endless discussions about how to wire the drivers to particular amps and what wire gauge to use, surge protection choice, acoustic treatments, etc. Then bracing is just "I'll eyeball it, will probably be quite enough, I guesssssssssssss".

Double the frequency require 1/4 the xmax to produce the same db output. Double the frequency until you get up to 750hz like the -3db point on the crossover for my speaker, then its quite small movement that is required for there to be actual db output from the enclosure surfaces.
Thus my full range speaker requires stronger faces than a regular marty.
But how much? Well that's what we can find out with simulation.
The sound, any sound, coming from the enclosure faces, is distortion. Stuff people pay out their behinds to not have on their drivers and speakers, not to mention their entire electronics portion. Then they put acoustic panels and diffusion elements and carpets and bass traps and they remove rattles and stuff by remodeling the interior of the room. Maybe with decoupled sheetrock and green-glue, special AC vents that don't make any noise and don't transport noise out of the room. They play their expensive lossless tunes on balanced expensive cables through a meticulously EQ'd system on drivers that cost a grand extra each to have the absolute minimum distortion. Heck, maybe the cones are carbon fiber, and even more exotic HF driver material.

Then the enclosure makes more distortion than all the drivers combined because its filled with pillow-stuffing not bracing (the faces vibrate even if you fill it with stuffing). And they would never know, and conclude their DIY martys and DIY LCR's are braced enough. But they didn't touch a CAD program. Then they go on to someone else and say "I braced this much and its great".
So a guessed amount of bracing with no known amount of benefit is great. Imagine if you actually knew how much you braced and how much effect it has had, there aren't words in the English language for it, if the unknown guessed brace is described as great.

PS: Here's the actual text you READ, but didn't read at the same time:
But in any case you could get a lot more output if you didn't need any filler in a marty because of having a very rigid enclosure. Well, "a lot more" being comparative to its cost. 1db more output from a double subwoofer setup by bracing and removing filler isn't difficult. If it costs you 2 grand to double your wooferage to 4 with twice the amps, then 1db for 10 bucks or something in glue in addition to some cut-off material, is a quite rational expenditure of calories.

PPS: And my build only goes up to 750hz where it tapers off. Because the compression driver doesn't apply anything above that inside, it all goes out the horn because the driver itself is closed at the back.
Other builds can have mid woofers instead of compression drivers, that do 6000hz before they pass over the responsibility to some HF drivers. Imagine 6000hz audio waves striking the internal faces and then having guessed amounts and configuration of the bracing. Do you know how little movement is required to get db output akin to the distortion figures of a driver, if the frequency is 6000hz and the area (cone area as it were) is up to six enclosure sides?

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post #152 of 337 Old 02-16-2016, 07:42 AM
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Originally Posted by ronny31 View Post
1db has to do with the difference between stuffed (example polyfil) quite a bit and not stuffed as much. Not the internal volume. That's what I referred to as having 1db easy gain in a dual enclosure setup. Pay attention!
But furthermore, the gain is that you don't have to guess how much bracing you need. You don't guess how much power you need, you don't guess anywhere in your build, except when it comes to the bracing. The tune is set in stone...
No one guessed before. The OP asked for advice and was told what was best. Then you jumped in with your GFR ribs and other nonsensical advice. And according to your previous claims, the tune is not set in stone. Remember, your bracing/stuffing scheme adds 1 dB for every 10 bucks spent
Quote:


(goes off on tangent with three paragraph off-topic straw man rant about pillows)


... But they didn't touch a CAD program. Then they go on to someone else and say "I braced this much and its great". ...And they would never know, and conclude their DIY martys and DIY LCR's are braced enough. But they didn't touch a CAD program. Then they go on to someone else and say "I braced this much and its great"...So a guessed amount of bracing with no known amount of benefit is great. Imagine if you actually knew how much you braced and how much effect it has had, there aren't words in the English language for it, if the unknown guessed brace is described as great.

What you keep ignoring is that someone qualified already ran the numbers and designed the Marty subs accordingly. There was no guesswork until you got involved. You made erroneous and uneducated claims about bracing (in a BRACING THREAD, this isn't a pillow thread), and have backpedaled ever since.

Then you download a program, and you think you're a speaker designer....
Quote:

PS: Here's the actual text you READ, but didn't read at the same time:
But in any case you could get a lot more output if you didn't need any filler in a marty because of having a very rigid enclosure. Well, "a lot more" being comparative to its cost. 1db more output from a double subwoofer setupby bracing and removing filler isn't difficult. If it costs you 2 grand to double your wooferage to 4 with twice the amps, then 1db for 10 bucks or something in glue in addition to some cut-off material, is a quite rational expenditure of calories.

(more off-topic rant)...

You weren't talking about bracing (see blue text above)? I am supposed to conclude that the references to bracing, 10 bucks worth of glue and some cut-off material is all about stuffing?


And what about the rest of what I quoted?


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Originally Posted by ronny31 View Post
This method of bracing is so effective that you need less than a quarter the material to get the same strength. Of course the way that uses FOUR times the amount of material is going to look "beefier", but it isn't.
The less material you have internally for bracing the more volume you have for added efficiency which means more db output at lower frequencies....

I expect that you'll discover fire next...
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post #153 of 337 Old 02-16-2016, 08:10 AM
 
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Originally Posted by Augerhandle View Post
I expect that you'll discover fire next...
Well, he did just get burned.
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post #154 of 337 Old 02-16-2016, 08:36 AM
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So someone "qualified" has worked out the bracing for every size marty out there (marty short-hand for vented enclosure I assume) that people ask about on this forum?

It was my opinion that cutoff and fiberglass is an apt method of bracing enclosures, was being the operative word. I assumed the other opinions given was not the word of "qualified authority" but the word of opinions.

"But in any case (signifying moving onto another topic) - you could get a lot more output if you didn't need any filler (pause here in your mind if you can't keep up) in (a connecting bit of the sentence which signifies that the previous bit specifies a situation) a marty (situation specified) because (another link of the sentence which arguably could have been put after a punctuation) of having a very rigid enclosure. Well, "a lot more" being comparative to its cost. 1db more output from a double subwoofer setup by bracing and removing filler isn't difficult (this is what has bee measured by Bill himself if I'm not mistaken, . If it costs you 2 grand to double your wooferage to 4 with twice the amps, then 1db for 10 bucks or something in glue in addition to some cut-off material, is a quite rational expenditure of calories."

I can't remember who linked to the actual measurement of stuffing amount vs db or where it was, but I'm sure Bill has that actual bookmark and did actually follow the point I made, since he didn't jump in all fingers-on-fire like Auger.
Auger, its not backpedaling when I have to explain what sentences mean to you. I backpedaled in one sentence long ago admitting that my initial opinion was hogwash in not so many words. Since then I made the point that an adequate amount of bracing can lower filler need and thus increase db. This is a bracing thread, and bracing = less filler = more db, is perfectly within the bounds of the thread.

PS: Auger made a good post disproving that the volume gained from more effective bracing would affect tuning significantly.
The only problem is, I didn't say there was 1db difference in tuning from saving 75% volume on bracing. But its an easy misinterpretation of the sentence I admit.

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post #155 of 337 Old 02-16-2016, 09:05 AM
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Originally Posted by ronny31 View Post
So someone "qualified" has worked out the bracing for every size marty out there (marty short-hand for vented enclosure I assume) that people ask about on this forum?

It was my opinion that cutoff and fiberglass is an apt method of bracing enclosures, was being the operative word. I assumed the other opinions given was not the word of "qualified authority" but the word of opinions.

Auger. I can't predict what parts of sentences you lay weight on.

It's easy. They will be the incorrect parts
Quote:

I can't remember who linked to the actual measurement of stuffing amount vs db or where it was, but I'm sure Bill has that actual bookmark and did actually follow the point I made, since he didn't jump in all fingers-on-fire like Auger.
Auger, its not backpedaling when I have to explain what sentences mean to you....

Bracing means bracing to me. Nothing in the word bracing remotely makes me think of pillows. It could be me, but I doubt it. I speak and understand the English language. I had four years of it in High School. My daughter graduated college Summa Cum Laude with a double major, one of which was English. She teaches English. I'll ask her.[QUOTE]

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post #156 of 337 Old 02-16-2016, 09:09 AM
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Ask her if she agrees with the use of argument from authority as an effective way to reach consensus :P
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post #157 of 337 Old 02-16-2016, 09:16 AM
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Nope. She said bracing means bracing, and pillows mean pillows. That is, if we are using them as nouns. She said Aftershave can be bracing as well...but not pillows.


Edit: She also said I shouldn't capitalize "summa cum laude".

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post #158 of 337 Old 02-16-2016, 09:23 AM
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Originally Posted by Bigus View Post
The only thing to keep in mind is that there are many solutions that give the same resonant frequency, but not all behave the same under a given input force. The high string on the guitar (I play brass instruments, not string other than the piano!) might resonate at 330Hz (Google is my friend), but so might a 1/4" diameter steel rod of a certain length. Both will sound the same note when played, but given the same "pluck" from your finger, which do you think will vibrate at a greater amplitude (and thus louder)? Going further, it may be that a certain huge steel beam in a skyscraper also resonates at 330Hz. Do you think it will move much with a typical finger pick??
The string's resonance is mainly determined by the mass of the materials, the length, gauge and tension. Just as the pitch increases when fretting the note, it will increase further from bending the string and increasing its tension. The length increases and the gauge slightly changes during the bend, too- as long as it hasn't reached the yield point, it will generally return to its original shape.

This brings me to a point that I think should be made- resisting movement in opposite panels can be achieved through adding a rigid strut between them, or by connecting the two with a mechanism that can be tensioned, like all-thread, T-nuts and a coupling nut in the middle. This way, it can be tuned as needed.

This would be best if the sides are double-layer, so any distortion in flatness would be reduced.
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post #159 of 337 Old 02-16-2016, 09:42 AM
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Originally Posted by ronny31 View Post
Ask her if she agrees with the use of argument from authority as an effective way to reach consensus :P

I don't need to ask her. "Argument from authority" is a fallacy only if the authority is speaking outside their field of expertise. You dismissed information given you by experts in the field under discussion, and straw-manned "argument from authority" when non-experts gave you internet links to authoritative information by other experts.

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post #160 of 337 Old 02-16-2016, 10:01 AM
 
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Originally Posted by ronny31 View Post
I can't remember who linked to the actual measurement of stuffing amount vs db or where it was, but I'm sure Bill has that actual bookmark and did actually follow the point I made, since he didn't jump in all fingers-on-fire like Auger.
I didn't jump in because there's no point. You're completely wrong, but to go to the effort of explaining what stuffing actually does, which is to alter impedance and Q (and as a result response) would just be going off into another aspect of loudspeaker design that you're completely unaware of. IMO this thread has devolved into an example of Dunning-Kruger effect personified, and it's not worthy of further comment.
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post #161 of 337 Old 02-16-2016, 10:19 AM
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Originally Posted by Bill Fitzmaurice View Post
I didn't jump in because there's no point. You're completely wrong, but to go to the effort of explaining what stuffing actually does, which is to alter impedance and Q (and as a result response) would just be going off into another aspect of loudspeaker design that you're completely unaware of. IMO this thread has devolved into an example of Dunning-Kruger effect personified, and it's not worthy of further comment.
Sure thing.
Green = no damping.
Blue = Damped with 3 polyfill pillows.


But I agree. Nothing constructive happened after post 144. It shows how to brace as simply as anyone want using corner bracing.

Pieces can be any scrap material you have laying around. Just put a 45 degree edge on them with a circular saw.
The "authorities" didn't suggest such bracing, even though it uses half the material and gets this difference in performance:


(bigger displacement is worse)
Guess what you can do with the other half of the material you didn't use, you may as well strengthen the enclosure further.
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post #162 of 337 Old 02-25-2016, 10:53 PM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post
1. 2 only braces in two dimensions.
Bill, curious if I could get your opinion. Typical rib style bracing I have seen seems to brace the baffle at the strongest point of the circle, close to the edge. Would it be better to use 4 dowels connecting to the back panel and placed more in the open part of the baffle? See attached example. Thanks
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post #163 of 337 Old 02-26-2016, 04:59 AM
 
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The baffle is most prone to flex close to the driver hole, as the driver itself wants to move back and forth and pull the baffle along with it. That's why my diagram shows braces as anchoring points for the driver attachment screws, to lock the driver/baffle/cabinet back into a solid unit.
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post #164 of 337 Old 02-26-2016, 07:19 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post
The baffle is most prone to flex close to the driver hole, as the driver itself wants to move back and forth and pull the baffle along with it. That's why my diagram shows braces as anchoring points for the driver attachment screws, to lock the driver/baffle/cabinet back into a solid unit.
Right, and when selecting the best 4 points putting them where the baffle is the furthest from the edge makes the best sense? See attached.
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post #165 of 337 Old 02-26-2016, 07:48 AM
 
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Yes, as the points furthest from the edges is where the baffle will flex the most.
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post #166 of 337 Old 02-26-2016, 10:18 AM
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Originally Posted by bob_m10 View Post
Bill, curious if I could get your opinion. Typical rib style bracing I have seen seems to brace the baffle at the strongest point of the circle, close to the edge. Would it be better to use 4 dowels connecting to the back panel and placed more in the open part of the baffle? See attached example. Thanks
It also works to move the dowels to the edge of the woofer cutout. If you lineup the woofer mounting bracket to where the dowels are then your screws mounting the woofer go through the baffle and into the dowels. This make the baffle strong by supporting it directly to the back of the cabinet and removes the need for extra wood pieces or t-nuts to keep the woofer tight against the baffle.
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post #167 of 337 Old 02-26-2016, 12:00 PM
 
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Originally Posted by bitmap42 View Post
It also works to move the dowels to the edge of the woofer cutout. If you lineup the woofer mounting bracket to where the dowels are then your screws mounting the woofer go through the baffle and into the dowels. This make the baffle strong by supporting it directly to the back of the cabinet and removes the need for extra wood pieces or t-nuts to keep the woofer tight against the baffle.
In other words, what I said.
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post #168 of 337 Old 02-26-2016, 02:10 PM
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Originally Posted by bitmap42 View Post
It also works to move the dowels to the edge of the woofer cutout. If you lineup the woofer mounting bracket to where the dowels are then your screws mounting the woofer go through the baffle and into the dowels. This make the baffle strong by supporting it directly to the back of the cabinet and removes the need for extra wood pieces or t-nuts to keep the woofer tight against the baffle.
My driver/bracing/baffle ended up being like this by accident lol (2 screws anyway)
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post #169 of 337 Old 02-26-2016, 11:23 PM - Thread Starter
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Yes, as the points furthest from the edges is where the baffle will flex the most.
Overall how big of a deal is resonance? If you build a small sub with 3/4" MDF and do not brace, would you really hear it?
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post #170 of 337 Old 02-26-2016, 11:28 PM
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I'd use something square, cheap 1x1 or whatever, so I can glue them to the other braces where they meet.
Yes!
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post #171 of 337 Old 02-26-2016, 11:58 PM
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Overall how big of a deal is resonance? If you build a small sub with 3/4" MDF and do not brace, would you really hear it?
Depends entirely on enclosure size and subwoofer power and the frequencies it does. But if you aren't making a full marty with very very powerful subwoofers, then probably not. The largest difference is output amount. A tiny movement in the faces mean energy from the cone moving, is lost, and does not end up compressing the air inside the enclosure like the simulation predicts. So the output is lower than what is predicted. If its a small cheap system, the amount lost is insignificant. But the bigger output you want and you get up to several expensive subwoofers, then at some point lots of money worth of output can be wasted. When +6db means you need to buy 4000 usd worth of subwoofers and amps (because you already have 4000 usd worth of subwoofers and amps), then you really want all your enclosures to be as solid as concrete if at all possible and practical. Because its not going to cost more than 1/40th the amount to get concrete-level enclosures.

cms, aka driver diaphragm suspension mechanical compliance: 0.000065 meter/Newton or in standard form 6.5e-05 m/N. (smaller number is better)
rms, aka driver diaphragm suspension mechanical resistance: 6.41 Newton.sec/meter. (higher number is better)
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post #172 of 337 Old 02-27-2016, 02:01 AM
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@BassThatHz I think it was did some measurements after adding a ton of bracing to his LCR speakers and reported them here somewhere... I cant find the link, I was looking for it today as I think I want to crack open my LCR's and do the same. Rip all the foam out and glue in struts and bits everywhere I can spare it, then glue the foam back in again. When he did it, there was a measurable difference in response, though it was pretty minor it was definitely there and visible in measurements.

Sensitive ears though would probably pick up box resonances in regular playback... I believe when listening to things at high output its what will make a speaker sound like it has more mass and heft.. more inert and actually let the woofers do their thing.

What ronny31 says above is half the story. The other half is the resonances don't just dampen the woofer output but the interior walls themselves end up acting as transducers and coloring the sound.

For LF subs it may not be as much of a deal (or I should say noticeable) IMO as highly sensitive high output full range towers, you don't want anything coloring the sound with those. I am very sensitive to things like vibrating mids, and I think I can kind of hear it in my new LCR's I just built. so thats something I would like to address with some more bracing.

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post #173 of 337 Old 02-27-2016, 05:41 AM
 
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Originally Posted by bob_m10 View Post
Overall how big of a deal is resonance? If you build a small sub with 3/4" MDF and do not brace, would you really hear it?
Resonance is moot. I thought I already covered that point. Vibration, which isn't the same thing, will detract from the performance of any speaker. If the speaker panels don't vibrate you're good to go. If they do then it's back to the old drawing board time.
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post #174 of 337 Old 02-27-2016, 05:46 AM
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This has been a very interesting discussion but I question that bracing is the sole focus of it. We should be looking at a total systems solution to the problem of reducing panel vibration to the point of inaudibility.

A few posts earlier Bill M posted about the pistonic motion of the driver cone and voice coil being transferred to the front panel, causing it to flex. That casn be taken care of by either using mechanically coupled dual opposed drivers or via an isolation mounting mechanism for the single driver. Doing the latter for a massive high excursion sub should be an interesting challenge for a mechanical engineer.

Once the physical driver motion has been taken care of there is the issue of the internal sound pressure itself causing the panels to move. I think BBC popularized the approach of lining box walls with graduated densities of foam and often a thin layer of bitumen damping material so the sound energy compresses the foam instead of causing the panels to move.

Damping should be part of any solution; all bracing alone will do is move the resonances to higher frequencies. You want any vibrations that remain to die out as quickly as the notes that caused them and their peaks to be reduced because so much energy is dissipated in the damping.

Consider constrained layer damping panel construction. Its much easier to laminate two thinner sheets of MDF or plywood together with green glue than to construct an elaborate matrix of braces, although its a pain waiting for the GG to cure. I actually built a hollow walled enclosure once and filled the walls with sand, a sonotube inside a plywood cylinder. I apparently didn't use enough sand because I could still feel vibration and that was just a 2-way SEOS's 12" woofer. This is where some analysis would have been helpful. Its difficult for the DIYer to obtain appropriate damping materials and to know without trying how well they will work.

If the panels themselves aren't damped, the braces can be.

So cheers to Ronny for doing the analysis that he did and a couple of broad hints as to the directions he might extend his work in the future.
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post #175 of 337 Old 02-27-2016, 07:53 AM - Thread Starter
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Resonance is moot. I thought I already covered that point.
You did I was confusing the terms. thanks
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post #176 of 337 Old 02-27-2016, 08:35 AM - Thread Starter
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This has been a very interesting discussion but I question that bracing is the sole focus of it. We should be looking at a total systems solution to the problem of reducing panel vibration to the point of inaudibility.

Damping should be part of any solution; all bracing alone will do is move the resonances to higher frequencies. You want any vibrations that remain to die out as quickly as the notes that caused them and their peaks to be reduced because so much energy is dissipated in the damping.
A few questions so I understand and lets assume sealed design,

1) If you have very good bracing, shouldn't that kill any vibration in the panels quickly should it start?
2) Why is it better to dissipate the energy with damping rather then letting the panels do it?
3) Say we are able to achieve perfect bracing, if we did not have any damping, would that put excess pressure on the back of the cone or is that what you want?

I do you Thank you for the sum up here. I have been trying to find a single white paper that puts all these concepts together which does not get too mathematical.
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Link describing simple bracing techniques described in this thread.

The author has five simple rules:

1. Keep unbraced spans appropriate for material used. (Under 10"-12" for 3/4" MDF/Plywood)

2. Brace across to opposite panels when possible, otherwise brace to adjoining panel.

3. Minimize bracing in corners where it is un-needed.

4. Take up the least amount of internal volume as possib

http://www.stevemeadedesigns.com/boa...o-brace-a-box/
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post #178 of 337 Old 02-27-2016, 09:37 AM
 
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A few questions so I understand and lets assume sealed design,
1) If you have very good bracing, shouldn't that kill any vibration in the panels quickly should it start?
Not quite. If properly braced vibration won't start at all. The panel will remain inert, or at least close enough to inert that whatever vibration that does occur doesn't result in audible coloration. One of the prime rules of loudspeaker design is that what you can't hear doesn't matter.
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2) Why is it better to dissipate the energy with damping rather then letting the panels do it?
It's not. The only place where mass damping is the better option is when bracing isn't an option. Sheet metal car doors, for example.
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post #179 of 337 Old 02-27-2016, 12:58 PM
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It actually depends on what the meaning of better is. If you are in the manufacturing business, its what is the lowest cost for an adequate solution. If you are a hobbyist, it might mean what is the best I can do within my constraints of time, materials, and tools.

It also depends on what you are building. Box coloration isn't much of an issue for subwoofers. Brace according to the common rules of thumb and you will raise the frequencies above the low pass cut off frequency of the sub. They will then never get excited. Having a sub rock or walk across the floor is likely more of a problem and thus you might want to think about dual opposed or isolation mounting, like I mentioned before. Or just make the box heavy enough not to do that.

If you are building a full range speaker, you can't raise the resonant frequencies high enough so that they never get excited. Instead you use more bracing than in a sub or a mix of damping and bracing. For a minimum solution, look at some of the DIYSG flat packs (but then you have to decide if and with what to line the walls). For overkill, look at some of the high end audiophile designs. Many of them have both damping and bracing.

Bill may well be right that will proper bracing you don't need damping; that is really just his definition of proper bracing - enough so you don't need any damping. Its likely also true that with some damping you don't need quite so much bracing. There is more than one way to skin this cat.
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post #180 of 337 Old 02-27-2016, 01:48 PM
 
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If you are building a full range speaker, you can't raise the resonant frequencies high enough so that they never get excited.
They may be 'excited', but that doesn't make them audible, and that's what counts. If, for instance, the panel resonant frequency is 500Hz but the panel is sufficiently stiff that it cannot vibrate enough to radiate 500Hz at sufficient levels to color the sound of the speaker then the resonant frequency simply doesn't matter.
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