"Best" is a relative term. All three work, but if you prefer to use polyfil it'll get the job done. You just need to use more of it than the other two. And I'm only looking at the ability of the stuffing to damp the interior of the box from the perspective of that one panel. The real difference between these is probably low enough that it really doesn't matter. With that said, when compared by weight, fiberglass and rockwool nose out the polyfil by a small margin. My preference for fiberglass mostly came from almost always having some on hand. I like to use what I have and tend to be realistic about the differences between materials. Even if there is an audible difference, a difference doesn't necessarily mean one is better than the other. Moving on to direct panel damping, rubber damping was almost useless and doubling the panel thickness is effective but mostly down low. Double layer CLD is effective across the tested frequency range. I would consider that to be something worth doing if you are looking for peak performance. Like I said in the video, it can be combined with stuffing to make it even more effective. Important to put all of this in perspective. These differences are relatively insignificant when compared with other much more important design considerations when build a speaker. Driver selection, box design (volume, alignment) and crossover design are orders of magnitude more important to how the speaker will sound. I do these tests to demonstrate just how small the difference actually is between these and how little they will affect the sound.
This is all wrong. The whole idea of stuffing a box was not the dampening effects, it's the ability to cancel waves and make the box appear "bigger" if I am thinking correctly. I don't have the math in front of me, but I've seen this test done here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-kc4AvfomdIQ.html
Two great videos, thanks! The preferred CLD method in UK DIY years ago was bituminous felt panels (a thick roofing product) covering all box internal surfaces. I built the Wireless World Tabor DIY design using Audax drivers using this technique in the late 70s. I had many comments regarding their excellent sound quality. When it comes to bracing, the matrix method first introduced by B&W and, later, used by Paradigm is beyond the capabilities of most DIYers. It is used in my present speakers Paradigm Studio Monitor 30s purchased twenty years ago that I have never felt the need to replace. However, I must admit I'm tempted by the KEF LS50 Metas with their use of a sculptured disc to absorb high frequency energy within the box, truly revolutionary and a tribute to British engineering.
Interesting series mate. Used to work as a Q&R for Bowers & Wilkins many moons ago in one of my brief career deviations. Materials, material density, isolation and insulation is something that can be talked about without end. As is shape and compartmentalisation. Whether you want a speaker characteristic or a flat response etc. All about marginal gains at a certain level. For DIY'ers, I think your info is sound. Good stiff box, braced and plenty of fixings as you've done. Also driver sensitivity matching as best you can which I think you've touched on. Acoustic loose fill stuffing (looks like cotton wool) is effective and cheap alternative to the stuffing options you've shown. Particularly good around internal bracing.
I build my encloser from 3/4 inch (19mm) Burch ply. It had a slight buzzy ring. So, cut the front baffle off, put a heaver mid brace inside. Then used 'Flex-Seal' brush on rubber on all surfaces inside and out. Then I lined the inside back and sides with a scrap piece of "Mohawk" Berber carpet but no other filling. So much better. I do not have all the 'Wiz-Bang' test gear but to these damaged Tinnitus ears, it sounds so much better. I have ear damage that shows up as a 20 dB White Noise shusssss all day and night.
Very interesting! what software were you using for the test? The damping material used is usually to control the resonance and other box parameters without regard to panel vibrations. Speaker enclosures can be viewed as filter networks, particularly for vented enclosures (such as Butterworth alignments.) However, controlling resonances will indirectly control the amount of energy available at any frequency to flex panels. You might consider using a measurement microphone to measure the acoustic radiation from a panel as opposed to the contact sensor on the panel. You might consider a box made of mdf instead of plywood. Mdf is a good material for do it yourself enthusiasts has high density and greater acoustic losses. Internal bracing is also effective in reducing any panel vibrations. Of course if you really want to eliminate you can build enclosures out of concrete, which I did for a customer in the mid 1970s. Wharfedale had speakers, which you poured sand into a sandwich construction enclosure in the 1960s. A speaker box has 6 surfaces, the most important is the baffle which is aimed at the listener, any radiation from top, sides, and rear are radiating into the room and contributing to reflected and not direct sound. The bottom of the speaker if sitting directly on a floor is coupled to that radiating 'panel', which changes the sound. That can be modified in a number of ways, a layer of material such as Vibrathane, a large mass (concrete), speaker spikes, or a combination of these.Keep up the good work! - Paul - former speaker designer.
My understanding is that stuffing mainly reduces reflections from coming out through the speaker cone, and any damping properties are secondary. It would be interesting to see this with a different box design. What would be even more interesting would be a double walled box with sand fill. This is supposed to do wonders for resonance. I would be most interested in seeing it with a big driver in a big box, vs a small driver in a small box. At what frequency does the sand stop doing anything? Thanks, I enjoy the content.
A small amount of stuffing/carpet especially on the inside back wall helps break up standing waves. But the primary reason for lots of polyfill type stuffing is to act as an air spring....i.e slow the speed of sound down a bit. This has the effect of making the box look bigger to the speaker But this is only if a small amount of stuffing is used and packed in a "fluffy" manner. If the box is packed too much it will have the opposite effect and actually increase the sound speed and make the box look smaller. Plus all this packing comes at the cost of some damping and efficiency loss.
Would be Interesting to see a test of "no rez " a product made for this purpose. I was also told vinyl floor tile with foam glued to it would work well.
Speaker fill has two purposes: to increase the relative internal volume "seen" by low bass frequencies, and to absorb mid to high frequencies. That being said, there's not a situation where speaker fill will dampen the side panel resonance, unless you use an enormous amount of fill. If making a 3 way design, the mix woofer should be sealed in a separate enclosure, and densely stuffed. The reason to densely stuff the mid woofers compartment is to eliminate internal reflection, which would otherwise interact with the woofer and cause resonance in the frequency response. For the bass section, if ported, then an "ideal" amount of fill should be used based off the internal volume. Since the crossover will limit mid and high frequencies, the main purpose of this fill is to increase the relative volume, and therefore the bass output. In a two way speaker design, ported, a hybrid approach can be taken. Dense fill behind the driver, loose fill everywhere else. There's plenty of online documentation demonstrating the best method to fill your speaker based off the speaker design.
Another thing to try is to put a cavity between two panels and fill it with sand. This should be even more effective than the CLD. One more experiment to try is to mount the woofer compliantly to the box. Add a ring of soft material between the woofer and the box. I read a study years ago and that had a big effect.
I found it odd that the various stuffings weren't directly behind the woofer. I always thought the role of any stuffing was to absorb/diffuse the rearward wave of the cone and flatten the impedance curve, kinda like how the vintage dynaco speakers did with their aperiodic design. Every acoustic suspension speaker I've ever opened up had the stuffing directly behind the woofer.
I've opened some older ones (from the 60's) that had wool material on the sides bottom and top, but nothing on the back wall. When I added rock wool to the rear wall it hurt the bass performances alot. So, I decided the people who designed them knew what they were doing and returned them back to stock. The bass came back. Not sure why
The Dynaco A35 is an interesting sealed design where the woofer chamber was greatly filled with mineral wool, and then a slot in a wall divided that chamber from another chamber which was empty!
Very interesting testing. However, the point of internal stuffing has nothing to do with damping the speaker cabinet resonances. It's purpose is two fold a) to change (slow) the speed of sound within the box, thus altering tuning, effectively makes the box bigger from the perspective of the drive unit, and more importantly b) to absorb and damp internal acoustic resonances which will impact the drive units frequency response. To see the real impact of internal speaker stuffing, you need to measure the drive units response with each (and with nothing as a reference point). It would have been intersting if you'd had a 5mm (or so) matt of low compliance rubber to place between the two panels when doing the constrained damping test. I think that would work better at actually isolating the outer panel from being driven by the inner panel than silicone would, as it's more compliant.
I like your videos a lot because I don't have the software to take some measurements, but I have to agree with some of the comments posted that stated damping is used mostly to avoid sound from the bass driver to bounce back in the cabinet and coming back with a delay and smearing the response. The fact that some materials are damping the cabinet walls is just an added bonus, so that material should be placed in the area around the mid-bass driver to absorb or slow down those pesky resonnances. My preference goes to acoustical foam because it is a very efficient sound absorbant and its elastic properties damp slightly the cabinet walls and stay where you put it. Beside what I have said before, I still appreciate the efforts you put on those videos, they make our knowledge about acoustic advance by leap and bounds. Thanks!
the theory behind it is, that the silicone layer has a different "wave resistance" than the wooden panel. that creates a reflection. so, one single wave is split up in two waves, one that goes through and one that is reflected back. better is to have three wooden panels with different thickness and two silicone layers. then you have 4 reflection points in that sandwich where the energy is bouncing back and forth multiple times and therefor getting absorbed a bit more.
I use wall insulation the one they use to insulate walls on homes and it works exelent i have some vintage sony speakers and what they use is polyfill sony speakers dont come with a crossover an on top of that they use polyfill and they sounded horrible i put a pair of crossovers and pulled out the polly fill and put some wall insulation inside and wow! what a diffrence it made your right about the polyfill its horrible a lot of electronics companys cut corners so they can make a product at an afordable cost them and in the process they end up selling garbage to the consumer you got it right polyfill is horrible
Back in the 1950's and 1960's JBL (Jim Lansing, the Lansing in Altec Lansing) used a proprietary particle board. This particle board was made with random sized wood particles. The purpose was to make a resonate free cabinet. The resonant frequency of the particles were random. This effectively prevented the wood from resonating at any one frequency. I read somewhere that the actor Richard Boone gave him the idea. Even the Ranger Paragon used this material with a fine vaneer overlay. Plywood is not a good material for speaker cabinets. All the laminations are the same size and resonate at a common frequency.
What you are describing is marketing hype, where you say a material does this special thing (like not resonate) and that gets the buyers all jazzed up thinking they are getting something special. In another of my videos I show that even if the speaker doesn't vibrate (impossible, by the way), the walls in the room will. And depending on how the wall is built it will vibrate as much or more than the speaker cabinet panels do.
Hi John, thank you for the video! The following is my uneducated opinion. What if instead of using a bid of silicon gluing plywood and mdf, try to sandwich a whole rubber mat between them? Plywood layer actually seals the box, so anything outside do not need to be sealed. Also instead of rubber mat, the polyurethane mat can be used. The only parts that can transfer the vibration between layers are screws, but they are located, I believe, in the places with the least vibration energy. So, vibration has no choice but go through the mid part of the sandwich.
Rubber is a good idea but i would put it as a final layer on the inside of the enclosure. This is more stable. You will get the best results if you mix materials with different resonance-frequencies. A ceramic tile on 60-70% of the side and backwalls (inside) will quieten your box too (may some rubber or bitumen on top of the tiles).
I have been under the impression that stuffing was to dampen internal parallel reflections. Dampening the walls by rubberizing and bracing is in no way polyfills job, apples and oranges.
well what about a thicker rubber speaker gasket,rubber is used to stop vibration but would it show results with your test ? which i really enjoyed thank you,im one of those people that never go overkill on bracing and using double walls on enclosures,i cringe in using a double baffle in fact i use 3/4 mdf but when i go to put my double piece on i actually just use 1/2 mdf.my bracing is kinda like well whats right above your head ? if your sitting in your house look up,in the attic theres 2x6's vertical so i use a couple pieces of light weight pine not treated pine 2x4's and put them vertical under the baffle with screws on each side of the box and screws going into the 2x4 from the top.thats just me.ive never cut picture frame shaped bracing,to me it looks like it would interfere with back waves.
I have also used vinyl floor tile to line the cabinet interior, along with foam, and insulation. I believe a combination of materials might be effective too. Sorbothane and Desadamp are two other products but are definitely more expensive. Did you try testing the woofers output to see if there was any change to the frequency response?
I have used combinations of “dissimilar” materials of various density in a few speakers I have experimented with and the results were satisfying from an auditory standpoint. I used polyfill along with rockwool and strips of Noico sound deadening mats. Overkill? Possibly but I was satisfied with the improvement in response. The cabinet was deadened substantially and the Noico helped greatly in that regards
I had a question, where can I get one of those accelerometers? And also is it trs or xlr connection?? awesome videos always interesting to watch, keep it up
Man, you are a fking unit, i think the same way as you do, like, a 3% in thermal conductivity its matters, but dont. loving your videos keep it 100, i love this test with every possible material o technic, tecsrry for my english
I would never use fiberglass for anything unless it has resin in it. That garbage get in yhe air and into eyes, sinuses everywhere. Im thinking of using cork.
I did some tests 25 years ago with an SPL meter, two 12" subwoofers in a sealed enclosure (trunk tire well enclosure) and various amounts of polyfill. I did individual frequency plots on a graph, 1Hz intervals. I found that adding polyfill decreased peaks and extended lows. There was a threshold where overall I started to lose some amplitude on all frequencies if I stuffed the enclosure too much. It was a great experiment to prove to myself that spikey response in a subwoofer can be tamed some.
That's really cool, and I've seen your results repeated elsewhere on YT. Adding polyfill does have a point of diminishing returns, but until then it will reduce bass resonance.
That's essentially lowering the Q by slowing the air, thus the driver appears to have more internal volume to work with. Up to 40% of the internal volume is effective, if i recall. Check with ChatGPT/Bing/Bard.
To me, using fill is never something I do to “fix” cabinet wall resonances. It’s only to help reduce standing waves or port resonances within the enclosures. I have tried many types: polyfill, pink insulation, Dacron, rock wool, demin, etc. The way I test is with impedance sweeps. I have found that lining the walls with 1.5” fiberglass is the best in midbass speakers. I put cheese cloth type material over it in ported boxes for piece of mind. Putting filling in the cabinet like you did dampens the airflow to the port which reduces output. I think that’s why people say overstuffing boxes will get weak bass. In subwoofers I use 3 inch pink insulation because it does the best job of “increasing” box size. Again, I only line the panels and adhere it with spray adhesive or hot glue. It works best with slot ports because you can get large even coverage. Getting a 30% increase in theoretical box size is common in common shaped enclosures. Whether or not that box volume gives an output increase or just changes the port tuning is still up for debate in my lab. To fix cabinet resonances, bracing is the only thing I’ve found that truly makes a significant enough difference for me do it. I know your measurements show that it doesn’t help at higher frequencies, but my cabinets really never have any resonances that high other than ports. Honestly I’m not sure why your getting such high peaks on yours. Maybe I just don’t notice them as much as the low 100-400hz ones.
@@zukispur5493 if you think you are having problems with cabinet resonances you should consider putting some additional bracing instead of just adding filling. If you are trying to get rid of standing waves or internal resonances then I’d start with a 1.5 inch thick insulation, rockwool or fiberglass should both work. Since they are sealed with passive radiators you shouldn’t need to worry about dusting.
When you brace in the middle of the box you up with two panels of the same resonant frequency, this is why asymmetrical bracing and trapezoid boxes will generally give you a better performance. Mass does work but is best with Multiple techniques of dissimilar Materials that will not exasperate resident modes. Enjoy the hobby. 😀
I just found your Channel last night. My goodness do I appreciate what / how you are testing. I have a few projects that im procrastinating on and now im glad I did. Thank you
The purpose of "stuffing for speakers" is not to "damp the interior of the box" and the test methodology used here is not appropriate to demonstrate benefits. Measure the impedance peak in various configurations.
Nice test! Another option is the CLD with thinner panels that’s about the same thickness as a 19mm MDF. I bet the CLD wins. The old speaker books and articles always showed better performance from fiberglass vs poly stuffing, and the really old articles from the UK mention sheep’s wool as the best stuffing. Also, what about the speaker output due to the stuffing? I thought the speaker output is smoothed out because the stuffing damps out the interior acoustic resonances.
The CLD has the most potential, for sure. Probably a combination of panel thickness and stiffness and size to arrive at the best result, but by then it might be deep into the rabbit hole and the time would be better spent doing something that produces more net gains. I would like to get some wool to try, though.
I have always been a fan of the "CLD" technique, have glued thicker MDF panels with silicone inside factory speaker enclosures many times always given good solid results. Great video👍
With respect, I don't understand why you are using stuffing to damp panel resonances, that isn't what it is used for, generally. Bracing is the solution in regards to this problem. Divide the panels up has you have with this box but add more and make the resulting panels smaller and with a higher resonant frequency outside of your passband. If you dado 18x25mm birch ply strips in to a cabinet wall this will be very effective. Internal ribs.
There are just two reasons to stuff a speaker box: The first is to increase the apparent volume. The second is for damping. There aren't very many ways to directly measure how effective the material is at doing that, but one is to measure how much a panel moves. If the stuffing is good for damping, that will show up in the panel. I explained this in the video.
@@IBuildIt I can think of a handful of other reasons why you would put damping inside a speaker (reflections, quasi-aperidoic alignments etc). It doesn't increase the apparent volume, this is a misinterpretation of it's effect - Q of a sealed box decreases with stuffing/overstuffing. I understand you said this in the video but why not measure the effect of the stuffing with actualy near field driver measurements? You are using a solution for another problem(s) for this one. CLD is more appropriate but as I mentioned before, internal ribs create sub panels with a higher resonant frequency outside of the pass band. Here is a really good paper on bass reflex stuffing, hope you find it interesting: drive.google.com/file/d/16j9rOXLL6uPSykyZ1OI9yk0QjQ-fZCXb/view?fbclid=IwAR3bduPGdCxVh_Ged8wRfEbU6vSqvdx7ulZulEBEqv6LYz48JlE3jG-0Je8
Reflections are reduced by damping - that's what damping is. And I know what aperiodic loading is, but never heard of the quasi variety. You seem to be misinformed about the apparent volume issue as well. Box modelling software takes that effect into account and I've tested the results that match. Could be you are getting confused by the other testing I did at the end with direct panel damping to put the results into perspective. I should have been a bit more explicit in explaining my procedure, but it's very difficult to anticipate what needs to be emphasized. A frequency response test may show differences, but how would you interpret them? This methods shows definitive differences and there's no problem to see which ones are better.
@@IBuildIt Fair enough, but I am not confused. Impedance graphs will show the effect of damping as will frequency responses - noted in the above paper. I think what is more critical in damping is position and amount used not the material as they mostly act the same. Using the same weight of each isn't an apples for apples comparison unless all you care about is the amount of material you use which you state below in your pinned comment (1g of feathers = 1g of lead). My point re a 'quasi-aperiodic' alignment (made up term-ish) is that the effect of damping becomes more apparent depending on where it is used. In this instance I meant a cabinet with uniform fill so there is damping between vent and driver. Keep stuffing and the vent output drops/is damped. Do you use Hornresp? If not I think you may find the MLTL mode very useful for simulating bass reflec and positiong and amount of damping in a cabinet.
@@grahamsquared it helps with damping because it reduces standing waves and resonances, you said it yourself when talking about quarter wave enclosures
I built speakers in my youth but never had access to the tools available now, so I have no experience with them. That said, I have a feeling you are scanning the frequency range way too fast. In my experience resonances take a while to build up. It makes sense right? Like if you push a kid on a swing it takes multiple cycles before the resonant amplitude builds up. You are not spending enough time at any given frequency for a panel resonance to build. (IMHO). So. Have you ever tried scanning much slower? I would be fascinated to see if that makes any difference.
Glass and rock wool slowly decomposes by the time, because of the mechanical vibrations from the sound. This glass dust particles make huge damages in the coil and spider area. We had this issue with old Telefunken TLX 2, 3, Kenwood trio LS, Pioneer and RCF speakers. Sometimes beyond unrepairable.
Stuffing is not for dampening panel resonances. Stuffing is for controlling internal box reflections, tuning the Q of the enclosure, or increasing the effective internal volume. Panel resonance is FAR more affected by bracing, material choice, and with direct contact dampening materials like vinyl or NoRes.
A well presented video. I like the control of parameters in one way. Having done quite a lot of work recently on exactly this type of internal dampening there are a few things to add. You have to keep something equal in the comparisons and that has to be in order for there to be a valid test of properties. Mass may not have been the best choice to create equality. Your explanation of how a fibrous panel can dampen internal energy from the air pressure created by the driver is spot on. Perhaps a more equal test of the different fibres would have been equal volume. With the Polyester fibres there was great contact with the box walls, and the glass fibers were in great contact with the box walls. The mineral wool was not. When you look up in the specs from each company that makes the insulation panels you'll find that Rockwool has a broader sound absorption than fiberglass when measured in thickness. I'm talking normal North American stud wall cavity thicknesses. Carpenter to Carpenter ( :) ) you know what I mean. Rockwool seems to have the edge due to what you referred to as the problem with Polyester Fibre. Mass. Rockwool is indeed heavy stuff. When in intimate contact with the cabinet walls it changes the cabinet wall behaviours. Again spot on is the attention to the resonant peaks at 350, 680, and 1.8 kilohertz. There is an approximate numerical relationship to these. They could be harmonics. And I'd love to see a impedance and phase plot to see their relationships. I'd be willing to bet that they are indeed harmonics. And this is the box singing along with the woofer. Note how some of the harmonics are actually louder than the signal. Nice demonstration of the panel bracing. That is a DIY loudspeaker myth as large as thick panels. Slaying the dragons one by one. Just because everyone is doing it does not mean that it is the best thing to do. Last thought. Placement of your absorber is also a variable. You had a resonant cavity behind the woofer without any absorber present.
Thanks Mark :) Hard to equally portion compressible material by volume and I think that would be less of a fair comparison because the rockwool is much denser than the other two. It would be the clear winner, just like a heavyweight fighter would easily beat lightweights of the same age in the same ring. And I don't see the empty space as a variable, since it was empty for all three.
@@IBuildIt I agree with you assessment that the heavier product wins. Hands down. But isn't that the goal in DIY audio? To take the state of the engineering art farther. DAmn the torpedoes versus cost and time involved. And be willing to intelligently apply these gains in our own creations. This is done for the companies that I design for. Apply the best of what is out there and connect the dots on the stuff that is either not published or simply becomes intuitive with greater experience. Keep these videos coming. You have a good handle on this stuff. Much better than I have seen from many people on RU-vid or otherwise.
As you have had some considerable exposure to audio forums, you'll agree with me when I say that what you say is best, might be completely rejected by someone else. Putting a denser stuffing into a cabinet might yield objectively better measured results, but it might not sound as good to someone who compares it to a less densely stuffed box. So I think the best I can do here with these tests it to try to show the apples to apples comparisons and the effects they have.
@@IBuildIt You should be able to find information of the density of the different materials. If you have that, then you could easily weigh out the 3 to the match the volume ;)
I always thought that the purpose of stuffing was more to dampen that hollow sound you get in an empty box as opposed to damping the resonance of the panels.
yes, you can damp the standing waves/resonances, but just a tiny bit. the best way is to put boards horizontally and vertically inside that partially reflect a wave. also using layers of light and heavy dampening create reflections between them. many different reflections result in shifting the energy from a single strong/loud resonances to many different smaller resonances.
Silicone is not the best choice. There are products made specifically for this purpose. Green Glue sound deadening compound is one I’m familiar with. You apply it with a caulking gun between layers.
I would have put the stuffing right behind the woofer. Also, try lining the inside with No-Rez dampening material as a comparison to an empty box - I would,bet that this alone would make a huge difference. The rubber lining you placed was way too thin to make a difference. The CLD method sounds interesting by sandwiching silicone in between the wood, but you have also effectively doubled the thickness of the wood. I would be interested to see if glueing the two pieces of wood was just as effective than the silicone. Interesting tests, thank you for posting!
This is an interesting test, but I was always under the impression a thin layer of stuffing attached to the walls was dampening, but stuffing in the enclosure is tuning for a enclosure that is slightly too small for the speaker, the stuffing slows down the waves in the box causing it to act bigger. That said, I'm not sure how much sense that makes since a solid should conduct sound faster than air, but the explanation has aways been that you're preventing a direct path, kind of how insulation prevents a direct path for heat to escape by capturing some air volume. Not sure I buy either explanation, but you can audibly hear the difference in the speaker most of the time. FWIW, I've always been team fiberglass even though it seems like polyfill is preferred everywhere. I've typically used 'glass for my own stuff that I didn't care as much about and poly when it was supposed to match some spec or someone else's standard.
Sound waves are pressure waves moving through a medium like air, water, wood, plastics and any other material that exist. Some materials like rubber, foam or cork are good at damping pressure waves because of their elasticity. This mean they absorb and redirect that energy, transforming it into heat (yes, that's right, heat). The proportion in sound to heat ratio is quite low, but enough to slow down the sound waves and lower the cabinet rebound sound, particularly in the midrange. With some crossover artifacts like a notch filter, it help the speaker sound balanced without killing the dynamics.
2:55 I thought you're talking about damping and not about repress or quieten sound. This is not the same. sound damping means that you will lower the velocity and energy of soundwaves. Repress means that you will improve the enclosure to be quiet and take down all responses or resonances, making it 'acoustic dead'. With this accelerometer you measure how good your enclosure represses the forcees that are treating it. The reduction of enclosure movement in combination with the damping-stuff is a result of the reduced wave velocity and energy that is absorbed by the polyfill etc. 7:14 and 8:16 this is a good way to improve the enclosure. By mixing materials with different resonance-frequencies you will get a better result, Many high-end speaker builders use rubber mats as a final layer inside. Stoneware or ceramic tiles put some weight on larger sidewalls. You only need tiles on 60-70% of the area to have a good result. You can hear the quality of your work by knocking on your box. It will sound dull within a lower frequency. Then you can start damping your boxed in air. To much damping stuff can be contra-productive. Ported boxes don't need much damping, in fact they work less good if you put stuff into the way the air should move. They only need some flat panels on the sidewalls to dampen the mid frequencies. A 6th order bandpass sub dosent need any damping at all but will get better with a solid enclosure. Long things short: Polyfill is pretty good and it's cheap. You get NO advantages if you buy high end super state of the art Polyfill wich is 'extra' designed for high quality sound. That's bullshit. You even could use ikea pillow-filling with the exact same results. The only thing with this stuff is that it mostly comes in little pieces. They are a bit difficult to get them to stay where they should. But if this is no problem you could use them. Greetings from Germany.
You may try to drill holes in the Inside of the panel in a Helmholtz resonator pattern that you compute to act around the most offending frequency. About the same as your acoustic panels just inside the speaker box
It was great that you tested a wide variety of materials, but it should be compared by volume, as well as weight. Another material i haven't seen used much that i plan on trying my own tests when i get the chance is closed cell foam, not sure if any of you have had any experience with that.
Fiberglass cotton is nasty stuff to work with, I used it to insulate an attic and a porch and that is the extent of using this material, would never use it in speaker enclosures. I had poly-fill cotton on my 1982' home-built V-ported La Scala Klipsch horns, inside the woofer cavity, for tuning purpose but recently, while cleaning them, took it out and I am getting better sound from them. They are crispier though, but I do not run them at high volume as in my younger days. I also built a set of shelf speakers, in the 80's, these mini cannons, bottom V-ported which I also used poly-fill to tune them, but the real deal is in the additional Formica sheet reinforcement over 3/4" ply they are built from. The best solid shelf speakers I have built, why I call them mini cannons. Whatever sounds satisfying to one's ears is what counts, but the object is obviously to replicate live music as close as possible.
Instead of using rubber sheets (or as well as) I would have preferred you to use an actual sound absorbing product that is engineered to absord sound energy within the material by turning it into heat. Something like Noico or Dodomat. In the 'car world' these are known to absorb much more noise than cheaper materials like rubber or even shed felt (yes, people really do)!
Any thoughts on bracing asymmetrically? I'd like to see you test with an accellerometer attached right over the brace and on each of the panel sections created. Even summing those three (amplitude and phase) would be a very interesting excercise. I'm building speakers right now, an planning to use some of the leftover materials for asymmetricaly placed braces, lots of polyfill (almost getting a rash from just thinking of glass- or rock wool). and possibly adding glued/stapled on bitumen and heavy felt. The mains will be an active cardioid solution with front and rear drivers in a common volume, rear inverted and delayed to mimick an output more similar to a theoretical U-baffle.
hi John... pretty late to the party...i wondered if you have tried slower sweep rates, or, indeed, how your sweep rates run? in spectrum analysis, to fast a frequency sweep kind of "aliases" into the results, and, depending on the Q of the resonant system, you can easily sweep right past a peak... anyway, what do i know 'bout speakers!
@@IBuildIt I'm just your average nobody that fell off a baby when i was a high chair. line the inside of the box with the 3/8 padding with the adhesive put seal & peel on the lip of the woofer. all things will be made clear.
@@ellasfella1205 what's clear in audio (and most other things) is how many people think they know more than they really do. And then they get on forums or other places (like here) acting like they have the answers. I think the technical term is "talking out of one's rear-end".
@@IBuildIt i agree but then again not many people have had the privilege to work for a company that worked on Whitney Houston's Phil Collins and Metallica's stage speakers & equipment
@@IBuildIt i would like to apologize to you cause before today this was the only video i ever saw of yours. when i was giving you the advice i thought you were trying to be cocky & arrogant with your reply that's why i replied the way i did. but after seeing 2 more of your video's i can see your not that type at all you are genuine and like your delivery so once again i would like to apologize. when i was giving you the advice it was professional advice. back in the early 90s i worked for crest audio we worked on Whitney Houston's stage equipment and we also built special speaker cabinets for Phil Collins & Metallica we did the same thing to their cabinets. so keep doing what do and stay safe
And double the panels of the pressed board Sawdust stuff that is 1 1/2 inch thick of the denses panels you could have the same thickness plywood will be much flimsier and transfer the loss of energy in the sound waves instead of HITTING LIKE THEY SAY ITS SUPPOSED TO NOT VIBRATE EVERY THING AROUND IT SOUND DISTORTED AND NOT HIT YA WITH THE NEW RYTHUM OF YOUR HEART WITH CLEAR HITTING BASS THAT YOU CAN'T GET WITH PLYWOOD AND STUFFING YOUR BOXES WITH COTTON AND FOAM AND TRY THE FINE SAND POWDER JUST COAT T COMPLETE BOTTOM OF THE BOX ABOUT A EIGHTH OF A INCH I WOULD NOT SUGGEST TO USE IT IN PORTED BOXES THAT HAVE NO PANELS SO THE AIR DOESN'T JUST BLOW OUT WITH NO PRESSER SO WEN SECTIONED THE AIR KEEPS PRESSURE WHILE STILL MOVING AIR TROUGH THE PORT
I have much success with dynamat. Make sure you have a roller and get it on tight. Many speakers simply will not have enough room for getting the dynamat properly installed. I put sound barrier on top on it. Only helps poorly braced boxes that have low frequency resonances, mine being 300hz specifically.
your reading acoustic vibration in the box not changes in acoustic sound waves. are you just trying to damppen the panels or tricking sub in to thinking it in a little larger box?? back when I had a RTA I did a test with poly fill with and without and there was a noticeable difference of 7Hz lower and 1db higher average subs was rockford he2 12's 1.75cf each
An idea of fillings inside the box is to HIDE some air inside the box(inside the cavities in the fillings)...so speaker cone is free to move, fiberglass whole is the best i find, you get better dynamics ,Bass become more pleasurable
To me the stuffing also helps preventing internal acoustic resonnance or reflected waves propagating back to the speaker cone. Thus it would make more sense to compare the sound capture than the vibration.
I found early in my salvage of speakers to reuse in reused kitchen cabs as speaker cabs that fiber fill is ineffecient for adding enough mass in th enclosure to increas bass tones fron the box.. my silution was to use foam rubber from old couch cusions.make a cup of foam just large enough for the speaker then fill the remaining space with more foam, the result is no internal sound reflection and deeper bass. making a 2 cubic ft box sound 2 or 3 times its size. at first I used cotton upholstry fill then found that the foam rubber worked much better,
I see you are only using 70ish volts dc per channel ! Why are you shorting your own amp design ? Why not use 120 volts dc per channel for Best Result ? 😊 Nice Craftsmenship 😊
You don't want to used fiber glass insulation you will be breathing all fiber glass insulation blow through the port's ahhhhhh unless it's seal boxes ahhhhhh 🙊🙈🙉🤔🤥💰🔥🕳️🕳️🕳️🕳️🕳️
900 Hz resonance with the speed in air of about 343,2 m/s results in a wavelength of 0.381m. divided by two is about 19cm. is this the inner distance between your top and bottom panel? because i think you have a standing wave there. to break that up you would need a panel with 4 big holes in between but not exactly in the middle because that would result in two synchronous standing waves at about 1800Hz. you would need to split up the 19cm distance in an odd ratio that the resulting two compartments have a different height. usually the "golden ratio" is a good idea. then the two new standing waves are not feeding a combined resonance. does this "sound" reasonable?
Does anyone know which big companies made their cabinets like the CLD construction ? I know that JBL made their TI and L series out of a CLD cabinet (SandwichSonicWall). Thx.
Add fiberglass and ONLY fiberglass. Idiots use polyfill and don't seem to understand thermodynamics - the glass fibers pull heat away from the voice coil and act like a heatsink.
So with all that thumping does the fibreglass get airborne and stick to the speaker and over a small amount of time cause an unexpected effect ? I don’t know but I’m not doing that being a first time builder of my own box. Seems like common sense to me but I’m only just starting my RU-vid study on this. I spent my money on a JL audio 10 w3 and I want to treat it nicely for along time.
A Mic is for measuring the resonance from the case influencing the flatness of the curve of the speaker. You have to measure the speaker when you test stuffing. The accelerometer is used to test dampening material like bitumen. You will se much higher difference with stuffing in mic measurement and much higher difference's with the accelerometer when testing dampening materials. You mixed up the Methodes and the measurements. That's why all your measurements are equal. Because the stuffing does nothing to the wood and the accelerometer because that's not what I meant to do.😅 Please watch this video! Explains it! ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DtQkMpHsMro.htmlsi=pqQksFQRXjSi0t8J
Since as you say the advantage of fiberglass and rockwool is the higher density, I'm puzzled as to why you would disadvantage them by putting in the same weight as polyfill and not the same volume.
Why not, as they say, "think outside the box" (heh, heh), and experiment with concrete slabs, ceramic tile, cement-board, thick cork, sand/epoxy slabs, etc.?
I always had look at speaker as a form of a piano- box with a mechanical equipment generating unique sound, why stuff the speaker box if the idea is to resonate the natural material with sound production of the speaker and finding that unique sound. Or am I over looking the process of sound-vibration?
This is all wrong. The whole idea of stuffing a box was not the dampening effects, it's the ability to cancel waves and make the box appear "bigger" if I am thinking correctly. In other words, bigger box, bigger bass. I don't have the math in front of me, but I've seen this test done here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-kc4AvfomdIQ.html
Thank you for these tests, very interesting. I had the same idea as CLD, but I want to use vibration dampening materials from the car audio industry, they come in sheets with adhesive pre-applied, quite convenient to use and specifically designed for this task.
Speakers are an air pump ‘I’m sure fiberglass does wonders for your lungs ,never understood why speaker companies would blow glass fibers in peoples faces?
It seems to me, you are testing the wrong thing with regards to stuffing the box. Stuffing the box, as you found out, does almost nothing to diminish panel resonance. But that's not why one stuffs a box. Stuffing the box slows down the wave coming off the woofer, thus 'fooling' the woofer into thinking it's in a larger back. This is completely separate from trying to eliminate panel resonances. And your test with rubber sheets could have failed due to lack of an mechanical impedance match. If one does not have a close match, there is no way for the vibration from the panel to transfer to the damping material.
Since you used two equally thick layers with silicone in between you actually mad CSL pretty ineffective. Silicone itself is not good for CLD because it stores energy but this is not the main point. You should put CLD where the shear stress on the visco-elastic layer on the greatest i.e. on the outside layer of the panel. Interesting experiment would be to use damping glue, even silicone would do if nothing else is found and a thin layer of aluminum. When I say thin I mean like a thick foul or beer can thickness.
How about multi-layers of damping from light to heavy? Low bass will go through most things, only mass absorbs it. Less heavy layers absorb higher frequencies
I'm surprised that the panel transmits so much energy in the higher frequencies according to your graph. I would have thought it would only affect the lowest frequencies.
with a remark: I don't believe this sweep test is relevant as the moment you record the next upper frequency you don't know if the panel is free by resonances produced by the previous low frequency (meant the previous resonance in panel is complete damped). It is preferable then, if still insist on a sweep test, to sweep from high freq to low freq as the previous freq will be damped more fast in case of. As comparison I.ll do for same tested material a double sweep: from low to high and from high to low to confirm, or not, identical results. Otherwise the measurement will be derated by still stored energy in the panel.
Can a short signal sweep reveal any resonance frequency in the box. Intuitively I'd say it more likely to take a sustained signal in order to start some materials to resonate. I had a pair of speakers that started to resonate at 260 Hz under certain circumstances when played at or above a certain spl. Would it be beneficial to play the signal sweep way slower in order to get slow starting resonance going?
Hey i was wondering can i use the same principles as soundproofing a wall and eliminateing echoes by using like cone stryctures in all typses of hights to absorb the resonant frequencies or will that make the speaker sound dead? i am not experimenting with saw dust with pva. i made a speaker and i need a thicker front panel its a bluethooth portable 200w speaker so theres not much space. to be honest i would need to remake it cause the 100w sub is way to much for the thickness of that boerd but i was wondering if i could make a putty and just make the wood thicker that way. the first small plate i made isnt dry yet after some 15h but it looks like the adhesion is greeat and it seems to stay somewhat plastic and moldable maybe when it dries it will harden but right now if i can use the spike type of structure this would be amazing material to do it with.
