Still not there yet. I mean this:
I have tried to grossly exaggerate the height differences just for illustration. After you split each brace into two fingers, those fingers should be fixed to opposite panels, not the same panel.
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Speaker Cabinet Design Considerations
- Thread starter Rick Sykora
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Still not there yet. I mean this:
I have tried to grossly exaggerate the height differences just for illustration. After you split each brace into two fingers, those fingers should be fixed to opposite panels, not the same panel.
Biblob
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Aren't panel resonances and vibrations difficult to measure while speakers are excited ? So if any particular design concept is used it will be little difficult to evaluate the minor differences as/and so much will depend on 'compliance' of damping material between batons on panel. My beginner curiosity is why not make small panels(top+bottom) thick to damp it and on large side panels a heavy object (SS metal disk ?) with damping material between them ? I suppose it would serve the same purpose. if we let this weight do the work.
OP
- Thread Starter
- #106
This appears to move back towards your original post. Gathering the CLD is the darker shading? Does this mean some of the cabinet walls are CLD too? If so, it appears much thicker than in the previous “sandwich”.
My dream design is small tower and the current design has window braces. Seen anything that suggests how often this dampener might need to occur in a larger cabinet?
Btw, I have little evidence that proves it is effective, but have been using windshield adhesive to dampen crossovers and port tubes. It comes in a thick ribbon. 30 feet is about $20. It is essentially butyl rubber and is readily available. Would be interested if it is suitable as CLD?
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somebodyelse
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https://www.sciencedirect.com/topics/engineering/butyl-rubber
Page cites multiple sources noting its use in vibration damping, so it's certainly worth a try. Ready availability in a consistent form is certainly an advantage. How you work out the right combination of length, width and thickness (do they offer different thicknesses?) to get the right stiffness for a given panel is another matter. Some experiment may be needed...
I've heard anecdotally that neoprene is also an effective damping material. I don't know whether it's either of these that's used in the rubber chevron springs that are sometimes used in railway primary suspensions, but in that application they provide the required damping.
Biblob
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Sorry, missed this one.
The thing is that the damping material should be viscoelastic. Soms forms of rubber are elastic but not viscoelastic.
A source, that will explain it better than me:
https://www.sorbothane.com/the-difference-between-elastic-materials-and-viscoelastic-materials.aspx
maty
Major Contributor
Yes, add viscolelastic material inside the loudspeaker is a great improvement. Better as a sandwich with other material and absorbent.
It is unacceptable that even expensive or very expensive commercial loudspeakers do not use it. They only spend money on the visible, which is how most decide their purchases, be they loudspeakers or cars.
It is unacceptable that even expensive or very expensive commercial loudspeakers do not use it. They only spend money on the visible, which is how most decide their purchases, be they loudspeakers or cars.
OP
- Thread Starter
- #110
Lol, after researching a bit more, found I live about 15 minutes from Sorbothane, Inc. Anecdotally, am around the corner from Audio Technica, US too. They have annual warehouse sales that are good deals. Was even more fun when they made speakers.
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somebodyelse
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EDM1029, EDM1016 and CL1151automotive damping materials from 3M. The EDM ones are an alternative to butyl/aluminium materials, but with a claim of better performance and/or reduced weight and cost. The CL one is an aluminium tape with a viscoelastic adhesive. I've no idea where you buy them in small quantities.
OP
- Thread Starter
- #112
As I was hunting around on the sad demise of Philharmonic Audio, I found they referenced a cabinet maker: https://www.speakerhardware.com/
Anybody have experience with them?
Anybody have experience with them?
OP
- Thread Starter
- #113
Well I created a damping brace for my subwooofer (pics forthcoming) using the butyl rubber windshield sealant and liquid nails. Need to install and run some tests. One part of the brace was only connected via the sealant and had to add screws to keep it in place. The sealant sticks well to non-porous materials; not so well to MDF.
Yeah I had some cabinets made by them. Custom work, good prices. I have a thread here showing the cabinet they made for me.
https://www.audiosciencereview.com/...akers-with-waveguide.10021/page-3#post-272812
maty
Major Contributor
Well I created a damping brace for my subwooofer (pics forthcoming) using the butyl rubber windshield sealant and liquid nails. Need to install and run some tests. One part of the brace was only connected via the sealant and had to add screws to keep it in place. The sealant sticks well to non-porous materials; not so well to MDF.
[PDF] https://us.kef.com/pub/media/documents/rseries/rseries2018-white-paper.pdf
[ There are two common ways of reducing panel output:
• Adding bracing between the panels to increase stiffness.
• Adding damping pads to the panels.
...KEF Engineers developed a technique, originally for the LS50 loudspeaker system but applied to all R Series 2018 systems, that combines the two approaches and is more effective than both. The technique, called damped bracing, consists of strategically placed wooden braces that, instead of being rigidly coupled to the panels are joined via a lossy interface. The braces are placed where the panel movement would otherwise be greatest and the lossy layer, like normal damping pads, converts the energy into heat.
Additional damped braces are situated at the back of each driver, which reduce the level of reactionary vibration transmitted from the driver to the cabinet.
The reduction in sound output from the cabinet varies model by model, depending on the exact geometry, but is typically of the order of 20dB, as shown in figure 3.
Cabinet sound radiation is highly distorted and, at the resonance frequencies, causes time-smearing as the output hangs on. The increase in clarity wrought by the damped bracing is readily noticeable, is probably best in class for single-enclosure multi-way loudspeaker systems and is comparable to the best high-end systems ]
OP
- Thread Starter
- #116
My damped brace was patterned after the design in the KEF LS50 white paper. Since it is a much bigger cabinet, mine just goes horizontally. Since it is a sealed subwoofer, it will have high internal pressures...
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OP
- Thread Starter
- #117
Here is the brace pic...
From the bottom up, starts with a back brace, the first woofer brace is glued to it with liquid nails and has a strip of (black) mastic across where it attaches to the cabinet back. The center brace (with holes for airflow) has mastic on top and bottom where it attaches to the woofer braces. The upper woofer brace has mastic across its bottom and 3 screws hold it in place to the cabinet back. Finally, you see some polyurethane glue to keep the top brace attached to the center one (as mentioned in previous post, the mastic does not adhere well to MDF).
Finally, am considering a few options:
From the bottom up, starts with a back brace, the first woofer brace is glued to it with liquid nails and has a strip of (black) mastic across where it attaches to the cabinet back. The center brace (with holes for airflow) has mastic on top and bottom where it attaches to the woofer braces. The upper woofer brace has mastic across its bottom and 3 screws hold it in place to the cabinet back. Finally, you see some polyurethane glue to keep the top brace attached to the center one (as mentioned in previous post, the mastic does not adhere well to MDF).
Finally, am considering a few options:
- How the subwoofer attaches to the braces? Mastic is not a great option because it does not stay in place. Looking around the shop, also have some felt and some foam weatherstripping. The driver already has a rubber case around the magnet, so might be enough...
- Would there be benefit to adding some more damping material in the channel between the woofer braces? Am treating this as optional, but open to ideas on what material is suitable.
- How to possibly improve the front baffle? My original thought was to double up on the MDF thickness. With the damped brace approach, am considering adding a layer of plywood using liquid nails.
OP
- Thread Starter
- #118
Ouch. Good news is no major audible resonances without dampening, bad is that things are much worse with dampening engaged. I used a piece of outdoor styrofoam insulation between driver and brace. Will try again with something else.
OP
- Thread Starter
- #119
Ok, styrofoam was a bad idea. I replaced with mdf block with mastic between it and the woofer braces. This was much better. Although afterwards I removed it and no difference. I upped the output and was still good too.
So, either my bracing is very good, I need some other type of mastic or better way to measure. I had always wondered whether damping might be a major improvement. For now, am inconclusive to negative (at least for a subwoofer cabinet).
So, either my bracing is very good, I need some other type of mastic or better way to measure. I had always wondered whether damping might be a major improvement. For now, am inconclusive to negative (at least for a subwoofer cabinet).
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tuga
Major Contributor
This graph from Axiom Audio, posted in the "So we now have a speaker with >5% distortion..." thread by @MZKM , seems to validade the BBC Research Department's decision to keep cabinet distortion at a higher level but lower frequency than making the cabinet more rigid and raise the resonance frequency to a range that is more audible both due to the human ear sensitivity (equal-loudness contour curves) as well as distortion "detection":
The relevant BBC research paper:
Factors in the design of loudspeaker cabinets
H.D. Harwood, R. Matthews - January 1977
The mechanical properties of timber, wood products and other materials potentially suitable for the construction of loudspeaker cabinets have been measured and details of the results are given. Various commercially available damping materials have also been assessed and their relative efficiencies are listed. A new method of test for the cabinets of completed loudspeakers has been devised and a tentative performance specification has been produced.
http://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf
The relevant BBC research paper:
Factors in the design of loudspeaker cabinets
H.D. Harwood, R. Matthews - January 1977
The mechanical properties of timber, wood products and other materials potentially suitable for the construction of loudspeaker cabinets have been measured and details of the results are given. Various commercially available damping materials have also been assessed and their relative efficiencies are listed. A new method of test for the cabinets of completed loudspeakers has been devised and a tentative performance specification has been produced.
http://downloads.bbc.co.uk/rd/pubs/reports/1977-03.pdf
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