Best Stuffing for Speakers Tested - Unexpected Results
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- Опубліковано 2 жов 2021
- "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.
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"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.
What would be the effect if you'd put acoustic foam on the panels inside walls?
@@joruss
In this accelerometer test, most likely nothing would change.
Helo look this ! ua-cam.com/video/FH3mmRLjKxU/v-deo.html
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: ua-cam.com/video/kc4AvfomdIQ/v-deo.html
Mineral wool or you call rock wool is nasty to work with but it works great insulating 500 to 600 degree pipe
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
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.
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👍
Useful information. There are soooo many different materials used. Nice to see someone putting some effort into this area.
Great video, for years in car audio I used to put carpet padding on all sides of the inside of the box! Except the subwoofer side, Thanks for the video.
Great experiment. Gives great examples as to why to brace and double baffling with cld!
Thanks for sharing your thoughts and ideas.
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.
Well done experiment. Thank you!
What a great video! Learned so much. Thank you.
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!
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.
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.
How can they use fiberglass with vented enclosures , just imagine all the tiny glass particles you are breathing . 😥🖐🔊😡
great video, i always seek to improve my cabinet designs.
i have not done much testing, but i do like to use things that have weight to it, when a 20 liter box has 1 kilo of bitumen or a kilo of damping stuffing then things are having an effect. i use "recycled textile fiber", its pretty heavy and packs in pretty nicely(for sealed box only)
Well done!
I like your scientific approach and testing.
Raw data doesn't lie.
John, very interesting video. My thoughts on dampening materials had always been centered on the driver output difference, or lack thereof, but seeing how they changed panel vibration was intriguing. However being you have this setup ready could you please do a quick comparison of the effects on driver output? Too many times I've read differing opinions on the subject and I believe it would be beneficial for more than just "Toids DIY Audio" ( iirc) having tested the subject on video. Thanks either way though as now I know I could use less bracing and more stuffing if necessary.
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.
Don't know if I will ever build a speaker but if I do I will remember this technique!
nice video bud, very useful info
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.
so this test is wrong, rigth?
@@chicotruco no, this test is fine. That's another test for you to make a video on
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
No not nessescarily. Not directly any way.
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!
Watch this as 2xs Speed. Great video, thanks
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!
I always used fiberglass but recently have been using rockwool. I think it works even better.
Love your testing, I am afraid cld increases the volume of the sound coming out through the driver but maybe more stuffing will compensate for that and still be the best.
Thank you for this, I love these type of tests, one thing I've heard of was car sound deadening sheets, have you ever tested those? Thanks
Very informative. Thank you. Would like to have seen result of using rubberized lead damping panels. also in CLD between plywood and mdf. Just curious.
Hi John. I enjoyed your new videos about speakers a lot. Thanks for the content. I was always looking to build speakers but never could find the time (Job). While research I did came up with Tech Ingredients "Worlds Best Speakers" video and tried them with birch ply. They sounded really nice (careful: amateur here) What would be your opinion on these? Could one implement such a panel speaker into a normal speaker system? A Swiss company called JMC Soundboard builds really nice ones out of birch.
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.
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.
Hi John. Do you think something like 3M's VHB tape would work better then the silicone? Kinda pricey to cover the side with it. But it's a 1/16" thick and kinda like a neoprene foam so would/may act different then the silicone.
Also, do you think there'd be a difference made with how you've got the panel attached? Gluing it to the box vs the screws as used?
Thanks!
Ha! Nice to see the sandwich panel at work!
I believe a thinner, more even layer of rubber adhesive damps better than a thick layer of silicone (because the glue is working in shear mode?)
i'd love to see a similar video (if you don't have one already!) covering how these different kids of stuffing materials affect the response/impulse measurements from a microphone. i recently built my first "kit" speaker, the desktop minis from GR and there are certain things i'm finding i'm not a fan of. they have a weird upper midbass resonance or chestiness to them, i realize i'm probably using the wrong terms to describe. some electronic music seems to sound harsh, gratingly metallic in the top end. there's probably not much i could do to help the latter, but i wonder if i should have gone with rockwool or fiberglass instead of polyfill, if that might have helped with the midbass/midrange. (i'm not bashing them, i think they were a decent value for 200 bucks) i'm excited for my next project either way
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.
Hello mate. Ive got a pair of celestion ditton 44 mk 2 (with the passive radiator) what filling should I use? Thanks in advance.
@@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.
@@noahnovotny2100 some bracing with inch and half rock wool it is then. Cheers mate I appreciate your swift reply
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. 😀
Hi John, what are your thoughts on both of the "Worlds best speakers" videos by Tech Ingredients? Thanks
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.
Hi, I always enjoy your videos. Can you tell us which accelerometer you use and where you buy it? Thanks
Nice video! 👏👏👏 One suggestion for the same video.... May it could be interesst to show the same test with the same speaker in different types of gabinets. Ones that TLs are in theory non ressonant...
Excellent, John! I almost always use stovetop stuffing… turkey flavored of course.
More a fan of the homemade variety, myself.
@@IBuildIt sounds delicious …see what I did there? 😇
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.
Thanks for this really good video. Do you have details of the accelerometer you used, and what method it uses to connect to your computer, etc? I would like to try to replicate your experiment method to help with some speakers I'm building.
Happy if you have an affiliate link you'd like to share. Thanks again.
Natural lambs wool, I find is the best, because its a natural & not man-made, like fiberglass & polyester dacron, that colour the sound, nice video👍
What about an equal volume(m^3, not amplitude) test?
Also it would be interesting to see some difrent laminations and even more complex bracing setups.
I am rebuilding a set of Berkley cabinets for my 12" Gold Monitors. When I originally built them in 1972 and used Rockwool for sound deadening. I have worked in multlex theatres installing sound panels. I have a few left. They are one inch thick of compressed of what looks like insulation. What are your thoughts on putting this on the cabinets walls instead?
Thanks
Would it make a difference if the 1/8 rubber was loose? Maybe just corner staples to hold it?
I'd like to see the results of just gluing acoustic foam to all surfaces of the inside of the box. Use the type that studios have on the walls. The 1 inch thick stuff with the triangle cuts.
Awesome test, ive always found fiberglass best also, but what about trying the no rez that danny ritchie uses, i had it in the encores and was amazing stuff, but more expensive.
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
Interesting. I've had to deal with sound attenuation on a couple of building projects that needed some serious noise reduction. Your fill test with different media was conducted by weight rather than volume, I think that it skews the results. The mineral wool at about 3lb/cu.ft. vs fiberglass at .6lb/cu.ft. doesn't utilize the density advantage by volume filled. That's still a marginal advantage anyway. Your conclusion with vibration inhibiting barriers that create isolation is the best process. You may even try a sound attenuation drywall that incorporates an isolation barrier built in. Pricey stuff, probably close to $100.00/4x8 sheet. Another product that works very well is a caulking called Green Glue, specifically designed for soundproofing and attenuation. Fasteners that bridge the isolation barrier( like screws) will negate the full effects of isolation. It take a bit of thought to bypass that sound transference issue. Good stuff John, by the time you are done you may blow all my suggestion out of the water, or I may have contributed. ;-)
Just wondering if you have tried cncing a diverse surface inside the box? Similar to room treatment. Might be fun.
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.
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.
It would be interesting to try some form of wood fiber insulation, as it has a better sound dampening effect than rockwool.
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
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?
Thumbnail looks like you are stuffing raw chicken into speaker ;)
That exactly wot l thought, 🤭
PS love yah John . Been watching for at least 8 yrs? Need more orig 90s rock shirts I kept recognising shirts I got at concerts during early 90s
I am wondering if the polyfill would block the aeroport vent.any thoughts on that
By the way, i like the idea to use an accelerometer. How you rigged to the laptop? Is there an interface in between?
At this moment im using my cellphone app.
And if you tried Sorbothane instead of rubber?
Or sheet lead, glued to the facing (not mounted) side of Sorbothane?
Or the same *volume* of Rockwool?
I used 2” foam padding inside a ported box. Stapled it to walls.
Lost out on higher notes but gained down low on lower hz music.
Scientific experiment entered the chat!
Esa Merilainen (author of current-driving of loudspeakers)
Also ran some tests.
He concluded that cotton cloth performed best at converting sound energy to heat. He also said tissue paper worked. I think he packs his enclosures with these quite tightly.
I've used eggshell foam padding sprayed on glue on all the panels but obviously didn't test with anything... just used it bcuz I had some laying aound and I figured they use that similar setup in recording rooms
Is there a coating that can be applied to the interior of the cabinet that could reduce cabinet resonance?
Thank you.
once I read (I don't remember, maybe in Popular Mechanics Mag) about small speakers, inside with cardboard/aluminum/foamy, to "enhance" the sound and make the box to be shield agains magnetisms). can it be "good option" to add those?
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.
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.
No rez ist wie bo dum 800 viel zu teuer. Schweissbahn auf Bitumen 4-6 mm dick bedämpfen auch gut bassreflex gehäuse
@@thomasschafer7268agreed no res is very expensive to get shipped to Canada
I put polyfill in my ported box because it was a tad bit smaller than the recommendation come to find out it took the port noise away lowered the frequency and got a smoother response now if your vented enclosure is built to manufacture specs I don't recommend using polyfill?
I remember responding to this but nope. Firstly great work. Accepting the use of fiber fills, I have Used activated carbon or sand or glass bits in woven cloth bags to keep the glass from rattling. The glass didn't do anything. It isn't porous so no sound absorption just deflection and a ton of weight. The sand made a dead speaker - oops. The carbon was best for low frequencies and I could isolate it in bags. But it was very expensive because I have not looked into what chemical is used with the charcoal to produce the very porous cavities of "activated" carbon.
I noticed you left parts of the wood exposed when applying the rubber which seemed counter productive to me. I can't help but think that spraying the entire inside of the cube with rubber spray would be more thorough? But like you have shown, thickness of panels and an isolated speaker would also fix some resonance.
Again, great video. Thank you for the time and hard work.
What are your opinion in stuffing a car audio subwoofer box (sealed or ported)? Let's say fiber glass because it seems to be the best of these 3. Would you consider getting to hot in there? Subwoofer produce heat.
I am not referring to crank SPL but on regular listening?
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!
Isn't part of the function of stuffing to reduce internal reflections around the inside of the box as well? These reflections can be bounced around inside the enclosure, and get redirected out through the driver out of phase (or in phase) and affect the sound. In this case, would it not be better to actually line each panel with stuffing, to absorb these reflections, rather than just randomly putting in a plug of stuffing in half of the enclosure?
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
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.
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 UA-cam study on this. I spent my money on a JL audio 10 w3 and I want to treat it nicely for along time.
Surprised you didnt test 'acoustic' foam variants. I have some old B&W that are just lined with some 1 or 2 inch thick grey foam. Other boxes ive seen use adhesive foam. There must be all kinds of foam. What about memory foam? :)
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 UA-cam 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 Oh do I agree with this. I post nearly nothing on forums. For good reason. So many arm chair quarterbacks it sickening.
@@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 ;)
Very interesting as usual. I wonder if using rubber sheeting between the two panels instead of the silicon would have more or less effect.
I found 3m make some very specific rubber sheet. I wouldnt doubt they have something suitable.
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.
Some very high end speakers use CLD with a thin metal layer sandwiched between plywood.
If you use sheep's wool you might get some ba ba baaing above 1K! Well, bad joke of the day.
@@stevenholt5484 the bass will sound wooly
The silicon is very interesting to me as I made a turntable support from 2 pieces of MDF with silicon in-between. This worked really well.
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.
@@stefanweilhartner4415 I will experiment with that thanks
Great effort here, but have to say the shape of the cabinet is close to a cube, which can have significant standing wave problems and is less typical of the taller / thinner shape of many of todays speakers. A good experiment would be to buy actual speakers (whatever you can afford) and test these with their damping and remove it, then test other damping alternatives. The cabinet bracing would be held constant of course as you'd have a pre-manufactured product.
Bracing has the largest effect by raising the resonant frequency of the panel beyond the point that the driver, when crossed over will excite the panel. And by varying the location of the bracing so that no more than 2 panels share the same dimensions helps further.
My tests show that it's harder to do that than it seems. The panels need to be very small to drive the resonance up high enough, which means a ton of bracing. And in a fullrange speaker there's always a driver that can excite it,
poly fill worked great in my Pearl Master BRX bass drum.. night and day difference
Have you tried using compressed chip foam or carpet underfelt / underlay. zig zag it in the box. Try high density foam.
Троелс же использует войлок ( у стены) + слой синтепона , они в паре работают на СЧ и НЧ, в блок НЧ битумная автоантивибра ещё нужна на стены.
What if I use the foam that you put the walls in the subwoofer box?
Now here in Germany we have a product called 'Reckhorn ABX'. It is a 2-2.5 mm thick sheet of butyl, covered with aluminium. It has a weight of 2.5kg/m². I would be really, interested in what that does to a panel. It has a relatively high density, so it doesn't take away a lot of volume, but also dampens really well.
Nehm Bitumen schweissbahn das ist billiger.
Hey man. Can you tell me which accelerometer that is so I can get one please?
I enjoy your videos. I have not built a speaker yet but I am very interested. I restore and tinker with cars as a hobby. When I saw what you were doing with the silicone I couldn’t help but think about the isolators that are used between engine intakes and carburetors, especially on high revving race engines. They do reduce resonant vibrations that cause problems for the fuel and air.
What would be the effect of isolating the woofer and tweeter by gaskets or silicone? I understand the purpose of a rigid box, but what happens if gaskets or silicone are sandwiched between all of the joints? Of course using a ported box.
I’m sure I’m way off here somehow, but I am curious.
You can use cellular rubber (1 or 2 mm thick) to reduce resonances and to mount the chassis airtight. Also a ported box needs an airtight mounted speaker. Mounting a chassis with some kind of rubber-metal-mix as they use on engines (Vergaserfuß in German [carburetor-foot]), the chassis would beginn to move in any diections. This would take a lot of acoustic energy, especially in the hights and cause many problems more. It would be the best mounting if the speaker is the baffle itself. No airleaks, no noise transmitting. Use the right screws and thighten them equally and it will work fine.
Measuring it's R factor should determine how much acoustic insulation you need and it's effectiveness. And also how dense you can make it and how easy to adhere the enclosure walls. I used to use lambs wool and also a material called Tufflex. Lambs wool was especially effective as it had a very high R factor but it was also difficult to work with and had a tendency to settle. Tufflex had a decently high R factor was easy to cut, came in rolls and (similar to foam) was rigid enough to stay in place.
Was Tufflex something like Kimberly-Clark's "Kimsul" ?
This is what every UA-cam video about audio should look like.
Thank you John for this. One thing that I would have liked to have seen done was to get the best results possible with the material you had, and not worry about the material being physically equal. So what is the best that you could get using various amounts of Rockwool vs various amounts of fiberglass. I understand that this would have taken much longer and it is way beyond my patience but it may be worth a try.
These tests can be used to decide how to get the best results without actually doing that.
But then the definition of "best" isn't an objective standard in audio. What's best for you might be less so for someone else - no, definitely would be less so for someone else, given how picky and contentious audiophiles are :)
@@IBuildIt ...re the last sentence... with some (many?) audiophiles it’s almost more important to find materials that can marketed well rather then work the best. An example is that FG has been criticized in the diy forums for many years, which are full of comments saying don’t use it or get rid of it.
Thanks
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.
I guess I should continue with my urethane filled cld panels/enclosure! Also what I've been using for fill is ultraTouch denim insulation, the absorption factor is as good or better than rockwool/fiberglass, it's kind of messy to work with, lots of loose fibers but I just hate fiberglass.
Love the work your doing!
Thanks for the video. I would just hang a thick blanket in strips... my metta 👌🥂☮️☺️
There are 2 problems to solve. 1 is to absorb the sound in the box so that it doesnt radiate back through the cone (using filling), the 2nd is to suppress panel vibrations being transmitted mechanically by the driver to the cabinet by constructing a rigid/well-damped box.
My methodology over many years is to use shelf bracing, often several horizontal and vertical in larger speakers (think B&W matrix) to raise the resonant frequency of the panels where they can be more easily controlled, then glue 1/2" felt to the walls and finally fill with lambs wool.
Have you tried a combination of plywood - polymer coating - plywood and an unequal cabinet?