I'm considering buying this kit from Madisound with the pre-built cabinets. In discussing this with them, their cabinet is unbraced. They claim it's not needed, which I find hard to believe given the size of the cabinet.
1. How should I brace these if I buy them from Madisound? For example, put a rod at the midpoint of the height, add some sort of mass loading panels on the midpoints of the sidewalls, etc.
2. Have the cabinets built custom with bracing instead?
1. How should I brace these if I buy them from Madisound? For example, put a rod at the midpoint of the height, add some sort of mass loading panels on the midpoints of the sidewalls, etc.
2. Have the cabinets built custom with bracing instead?
Hmm, your first option seems fine, front to back might make sense, volume shouldn't change much.
Or would it be more interesting to add a second layer using a soft adhesive, ala CLD?
Or would it be more interesting to add a second layer using a soft adhesive, ala CLD?
That is quite a sum for a pair of veneered cabinets, 439 bucks. Doing it yourself is not an option, I suppose?
Cabinet bracing sounds like a good idea, but it's actually a can of worms. 😀
Light fillets can make for strength, but the main event is panel damping. This is done with rubbery stuff stuck to the panels. This being an old Spendor. Considered a decent design.
Light fillets can make for strength, but the main event is panel damping. This is done with rubbery stuff stuck to the panels. This being an old Spendor. Considered a decent design.
Seas A26 Questions
I'm really close to ordering this kit from Madisound, including the pre-built cabinets. I have some questions:
1. Should the cabinets be braced, or sidewalls damped in traditional BBC fashion using something like Dynamat? The Madisound pre-built cabinets are un-braced (just like the Seas kit shows on their website)
2. Are they fussy with the amount of acoustifill you add?
3. Honest assessment of sound quality for those who've built it?
4. I assume they're tube friendly?
I'm really close to ordering this kit from Madisound, including the pre-built cabinets. I have some questions:
1. Should the cabinets be braced, or sidewalls damped in traditional BBC fashion using something like Dynamat? The Madisound pre-built cabinets are un-braced (just like the Seas kit shows on their website)
2. Are they fussy with the amount of acoustifill you add?
3. Honest assessment of sound quality for those who've built it?
4. I assume they're tube friendly?
1/ i would not build without braces and using quality plywood. I’d guess the Madisound cabinets are MDF since they come veneered.
2/ i would expect yes
4/ tube friendly is one of those terms tha turns out to be very useful. If you have a tube amplifier (or SS) with high Rout like a typical SE amp, yo want a speaker with fairly flat impedance. Few PP amps do not have this issue, but flattish impedance is still nice given the output transformers.
dave
2/ i would expect yes
4/ tube friendly is one of those terms tha turns out to be very useful. If you have a tube amplifier (or SS) with high Rout like a typical SE amp, yo want a speaker with fairly flat impedance. Few PP amps do not have this issue, but flattish impedance is still nice given the output transformers.
dave
Attachments
Newbie Help Needed: Cabinet Wall Damping
Can someone recommend the right material(s) to damp the interior walls of this cabinet, just a SIMPLE solution:
http://seas.no/images/stories/diykits/pdfdataheet/A26_cab.pdf
SEAS A26 Kit
I'm lost, can't find any consensus on what to use. The cabinets come pre-made from Madisound exactly like the kit plans, i.e., un-braced. I'm OK with that, but I'm wondering if I should mass load with Dedshete a la BBC protocol, use eggcrate foam, etc.
Can someone recommend the right material(s) to damp the interior walls of this cabinet, just a SIMPLE solution:
http://seas.no/images/stories/diykits/pdfdataheet/A26_cab.pdf
SEAS A26 Kit
I'm lost, can't find any consensus on what to use. The cabinets come pre-made from Madisound exactly like the kit plans, i.e., un-braced. I'm OK with that, but I'm wondering if I should mass load with Dedshete a la BBC protocol, use eggcrate foam, etc.
PDF doesn't say anything about wall damping
50 grams of damping material (example: polyfill), evenly distributed.
50 grams of damping material (example: polyfill), evenly distributed.
I am aware, and speaking with Madisound, they only supply simple foam sheet:
Dampers: Foam Sheet 27" x 42" x 5/8"
And they told me that I need to experiment and that's the fun of DIY. I'm pretty OCD (aren't we all on this forum) and goofing with loudspeaker damping is not something I want to engage my OCD on
There is two types of materials that are referred to as "damping", because there are two types of resonances we must be concerned about.
First type is acoustical resonance inside the cabinet. The solution is simple and easy: acoustical damping. This can be fiberglass insulation, rock wool, polyester fiber fill, wool, shredded denim insulation, or several types of foam.
Almost all speaker cabinets will require acoustical damping. Rock wool is cheap and easy to find, and it actually works very well. For a sealed box woofer enclosure or midrange enclosure I would fill the space with loosely arranged rock wool. For a vented box, I would line the walls with a 2 inch layer. Specialty sound absorbing foams can be easier to work with for vented boxes. Polyester fiber fill is very easy to work with (no itch).
The second type is structural damping to help tame structural resonance. All of the common wood-products use to make speaker cabinets have internal damping, but sometimes people add additional damping. Examples of this would be layers of heavy rubbery compounds bonded to the inside cabinet walls, or even layers of rubbery compounds encased within the cabinet walls. There is some debate as to whether this is needed. Most speakers sound just fine with no additional structural damping. Some people are enthusiastic about structural damping.
I mention both types because sometimes people confuse the two. Structural damping does not fix acoustical resonances, and acoustical damping does not fix structural resonances.
First type is acoustical resonance inside the cabinet. The solution is simple and easy: acoustical damping. This can be fiberglass insulation, rock wool, polyester fiber fill, wool, shredded denim insulation, or several types of foam.
Almost all speaker cabinets will require acoustical damping. Rock wool is cheap and easy to find, and it actually works very well. For a sealed box woofer enclosure or midrange enclosure I would fill the space with loosely arranged rock wool. For a vented box, I would line the walls with a 2 inch layer. Specialty sound absorbing foams can be easier to work with for vented boxes. Polyester fiber fill is very easy to work with (no itch).
The second type is structural damping to help tame structural resonance. All of the common wood-products use to make speaker cabinets have internal damping, but sometimes people add additional damping. Examples of this would be layers of heavy rubbery compounds bonded to the inside cabinet walls, or even layers of rubbery compounds encased within the cabinet walls. There is some debate as to whether this is needed. Most speakers sound just fine with no additional structural damping. Some people are enthusiastic about structural damping.
I mention both types because sometimes people confuse the two. Structural damping does not fix acoustical resonances, and acoustical damping does not fix structural resonances.
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Disengage! Disengage!
OK, trust me, I'm a loudspeaker design engineer and I also had exactly this experience with some much older speakers. Here's what I would do:
(1) Bracing
- Get some 1/2" or 3/4" dowel rod, whatever is handier, and get thee a file and or rough sandpaper.
- Measure the three inside dimensions very carefully, better in millimeters. Cut the dowel into three pieces a tiny bit longer than the dimensions (hey OCD part of the brain: that means 0.846 mm 😀 ).
- Jam them in there to put the cabinet faces under a bit of strain, and wood glue around where the dowel touches the inside of the cabinet wall. Yeah, this means six sets of drying time.
- Where to put them you'll have to fiddle with depending on how the drivers fill the inside of the cabinet. Off-centered on each panel is good. Where exactly the go will make less difference than having them or not.
(2) Wall damping
Get thee some of this stuff from a former coworker's business Vibration Damping Compound Reduces Noise and Increases Sound Output. and paint it on the inside
(3) Cabinet damping
Yeah, Acousta-Stuf is fine. Don't get it near the woofer cone, and leave several diameters clear of the port. No, I don't really believe in aperiodic ports. Nothing really wrong with them, just they are a kind of degenerated solution of other design cases. Experiment if you like and your OCD can handle it.
Short of buying some instrumentation and spending all your spare time making (likely non-repeatable) measurements, the above procedure will be more than good enough.
ENJOY!
Three threads discussing the same project have been merged.
Please do not start multiple threads like this as it causes confusion and duplication.
Dowels and either Duratex acoustic dampening paint or similar paint with sand mixed in to help damp cabinet resonances. Acoust-X Sound Damping Coating 1 Gallon - Acry-Tech Coatings
Then experiment with polyfill. I prefer to start small when it comes to fill.
Then experiment with polyfill. I prefer to start small when it comes to fill.
You should assemble the kit as suggested in the manual and not fuss around with different ideas. Listen to it for awhile and once you get accustomed to its sound, come back and report what you think of it.
Have you checked SEAS: The Art Of Sound Perfection ?
There is application notes from the designers of the original kit there
There is application notes from the designers of the original kit there
On the SEAS DIY-kit pages it says: "Adding internal bracing to stiffen the cabinet is a good idea for the advanced builder, and will further enhance the performance".
However, there is always a "catch". If you are unlucky - the bracing can transform the original resonances to more audible resonances at higher frequencies. This effect was discovered through the development of so-called BBC monitors (Spendor, Harbeth etc.). A quite safe and easy alternative is to use bitumen (soft heavy asphalt type) pads glued to the walls by a flexible adhesive.
However, there is always a "catch". If you are unlucky - the bracing can transform the original resonances to more audible resonances at higher frequencies. This effect was discovered through the development of so-called BBC monitors (Spendor, Harbeth etc.). A quite safe and easy alternative is to use bitumen (soft heavy asphalt type) pads glued to the walls by a flexible adhesive.
If one pushes the (potential) resonances far enuff up they are unlikely to ever be excited.
The other approach is the BBS style of pushing the resonances below 100 Hz where they are less audiable but very likely to get excited.
The A26 box is large enuff to require bracing IME.
dave
PS: here is an alternate enclosure Scott & i did for the A26 kit. From when it was a WAD kit. http://p10hifi.net/tlinespeakers/FAL/box-plans/classicTL-revisited-WD.pdf. Giving its age, probably worth a relook. Certainly a drawing revision.
The other approach is the BBS style of pushing the resonances below 100 Hz where they are less audiable but very likely to get excited.
The A26 box is large enuff to require bracing IME.
dave
PS: here is an alternate enclosure Scott & i did for the A26 kit. From when it was a WAD kit. http://p10hifi.net/tlinespeakers/FAL/box-plans/classicTL-revisited-WD.pdf. Giving its age, probably worth a relook. Certainly a drawing revision.