That's one of the reasons for the burrito having the polyester batting for the outer layer. I thought about putting some chunks of rockwool in there as well but it didn't seem worth it. But the overall idea is varying the shape and absorbing materials to create better absorption and more complex impedance changes
Yes this kind of a cabinet can sound nice, requires fine tuning and/or luck to get it right.
Not the cabinet type for maximum oomph and tight bass with electronic music, it requires a heavy cabinet. But it might be very good for subjectively satisfying "music bass" with acoustic instruments. I have done a lossy enclosure (15mm plywood + bitumen) once and they were quite good subjectively! Hifi and especially speakers is a form of art in the end and there is no right and wrong.
If chosen to go down the uncolored, tight bass etc. road instead, I have begun to appreciate mdf more than before. I have always used 15-22mm birch plywood, which is very stiff and lighter compared to mdf, but 25mm mdf which I chose to my lates project, makes a much less "expressive" cabinet than my previous plywood cabinets. Mdf cabinet sounds dead and weights a ton. Plywood cabinets have a specific tone if they are not braced to death and because they weight much less they dont seem to produce quite as tight bass as a heavier cabinet. Mdf is also quite lossy, maybe it does not radiate/pass "through" it the back wave/sound as much as a more rigid and less lossy panel, who knows. Nevertheless mdf cabinet sounds "silent".
But if used "a low Qms, rubber surround, aluminum cone" etc. nightmare bass drivers, then maybe I would not put it in mdf cabinet. Plywood cabinet might give it subjectively "livelier" sound which the woofer inherently lack, and might work better in plywood cabinet? It a balancing act. Just came to my mind when I watched those videos. Regarding the videos, big room has a big room's sound. I like bigger rooms, sounds organic and there is natural "blacker backround" to sounds as early reflections are delayed more.
This has been my experience as well. MDF sounds dead. Its possible also to make a cabinet stiff in lower frequencies by bracing but then use thinner panels to add some mid range tone. This can add some warmth to certain recordings or take the edge off of certain room problems or cone issues.
Overall though I would say a dead cabinet is the most proper one and will image the best. The musical cabinet is more to correct for problems.
A foam pyramid seems like a good idea. Might be difficult to predict how it effects box volume, but thats what measurements are for.
Measuring cabinet sound is notoriously difficult. I'm curious to see what results you get.
Here is a picture of a box I did that I lined with foam. I know a lot more now then I did then. But even then I had to admit to myself it sounded bad. Like a muffled foamy mess. Of course one speaker with one material doesn't prove much. I do seem to remember that the walls of the cabinet where less resonant with a knuckle test. I ended up tearing all the foam out.
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But you're already predisposed to disliking that sound/idea/material. Same as people saying that copper cables sound warmer than silver cables which sound brighter.
If you listened to a Geddes waveguide with a foam HOM-reducing plug in it you'd probably say that it sounded muffled, whereas if you didn't know if the plug was in it (blind test), I'd venture to say that you probably wouldn't notice at all.
Even better, grade the stuffing so that it's more robust as you approach the walls. Hence the suggestions of thick felt - which would have the added benefit of reducing reflected sound by reducing the abruptness of the air/sidewall interface.
You could have built the box with 2 independent woofer chambers for the top and bottom,
then the longest dimension is 1/2 re how it is now. The top to bottom standing wave frequency would double and be easier to damp for that reason.
No standing waves below wavelength/2 so for 85cm box that is 170cm wavelength which equals 200Hz. So for a subwoofer playing less than 200Hz there is no standing waves in a box smaller than 85 cm or 2,5 feet.
However, due to the adiabatic pressure the temperature will rise and if you have stuffing in the box and lower the speed of sound the box actually gett bigger! Thats why you have stuffing in subwoofers.... To get smaller boxes...!
However, due to the adiabatic pressure the temperature will rise and if you have stuffing in the box and lower the speed of sound the box actually gett bigger! Thats why you have stuffing in subwoofers.... To get smaller boxes...!
Putting sound absorption in the middle seems intuitive to me but I'm also curious about the reasons. One thing it does is naturally divide up the cabinet into smaller sections with non parallel surfaces.
Well, it seems perfectly logical but I would like to read up on pressure, velocity, etc. minimums and maximums as relating to size, shape, volume, surface area, etc. I have heard under-stuffed and over-stuffed speaker boxes both. They both sound bad compared to the "ideal"...too much is a bad thing, not enough is also a bad thing; happy medium, middle compromise (middle pun intended!!!).
You can do something that is analogous to a VSWR measurement in a microwave waveguide,
by using a small (1/4") mic to probe inside the box to find high velocity points, that is where
you want to put damping to reduce a particular standing wave.
I didn't line the walls, but I suppose you could. I have so much bracing its not worth it. I personally like a little bit of a woody sound to the cabinet and don't want to get to carried away.
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