The coat of tar worked very well for me. But the kerfed wood may have been thicker than what you are starting with.
Bondo will get hard, won't it? Will it damp well when hard?
The idea of the tar is that it remains pliable, though it does form a skin. Some of the big multi-cell horns were tar filled for the same reason. Others seem to have this "auto body tar" on the cells with paint over it. Such was the case with the 1505s I used.
Bondo will get hard, won't it? Will it damp well when hard?
The idea of the tar is that it remains pliable, though it does form a skin. Some of the big multi-cell horns were tar filled for the same reason. Others seem to have this "auto body tar" on the cells with paint over it. Such was the case with the 1505s I used.
Yes, it works very well. I used it for my own 511B horns and now if I tap it with my fingernail, all I hear is “thud”. Before the treatment, it would ring like a bell. It needs to be about half inch thick which adds a bit of weight but unless portability is the main issue, I don’t see a problem. Plus, it’s smooth to touch and has color of my choice.panomaniac said:
Even harmonics said:
I use automotive "Gravel Guard" to damp metal horns. I use a compressor driven "Schutz Gun" (undercoating gun) to apply a thick coat of this stuff to the back sides of the horns. I tried automotive undercoating -- it damped the horn OK but it never dried -- it remained a messy goo. The "Gravel Guard" is just as effective at damping as the undercoat -- but it dries into a neat coating.
Don't want to completely threadjack Bear, so I started a new thread on horn damping.
Horn Damping Thread.
Horn Damping Thread.
Evenharmonics said:
Yes, Bondo will stiffen nicely. Almost ideal because of it's ability to stick.
Problems:
- icky to work with
- gotten ******* expensive now - like $16 USD for an unfull gallon pail and the horns will take two gals to do!
- inexact catalyst mixing
- scary fast set up times for the current stuff makes it hard to work
Thinking of thinset floor leveling mix w/sand added. I tried it and it seemed to work ok...reverse problem, slow overnight set... :-(
_-_-bear
Recently, I did some Altec design as well, together with Guido Tent and Bruno Putzeys.
http://homepage.mac.com/marc.heijligers/audio/files/altec.html
Mechanics are a disaster indeed, and the filter needs heavy modification. But after that, it sounds pretty nice.
Marc
I thought I'd make a suggestion, that isn't necessarily cheap and I've never used on horns, but may work for this application. I've had some luck using epoxy (System3 in my case) mixed with Pulverized Lime (the stuff that is used for marking fields at sporting events). Mixed to a thick paste it has the ability to be worked and gives you the time to correct anything that may not be quite right. I'd advise against large batches (because of heat and accelerating the set up time) and a thin coat of straight epoxy applied first and allowed to set up would provide a primer coat of sorts for the subsequent Lime/Epoxy material. It can be sanded, but it's fairly hard so it's probably better to work it before it sets up.
I have used this for filleting the space between the Magnet and frame of drivers, and it work well for that application. BTW: the Lime seems to come in two grades, you want the Pulverized Lime that is the consistency of sifted flour, not the variety that have chunks in it. A bag (50-60 lbs.) usually costs two or three dollars and should be more than enough and it also offsets the higher cost of the epoxy.
Final Disclaimer: I have not used this for horns, so you may want to try in out on something else first. The lime, however, can be used on your lawn to green up the grass and kill moss
Best Regards,
TerryO
I have used this for filleting the space between the Magnet and frame of drivers, and it work well for that application. BTW: the Lime seems to come in two grades, you want the Pulverized Lime that is the consistency of sifted flour, not the variety that have chunks in it. A bag (50-60 lbs.) usually costs two or three dollars and should be more than enough and it also offsets the higher cost of the epoxy.
Final Disclaimer: I have not used this for horns, so you may want to try in out on something else first. The lime, however, can be used on your lawn to green up the grass and kill moss
Best Regards,
TerryO
Yeah marche,
That stock response below 50Hz. is awful!!
I am surprised that you got the final to be as smooth as it is where the 15 incher is running in that cabinet.
Did you mod the box from stock??
TerryO,
I'd advise against using Lime, as lime is very reactive.
Better stuff would include talc, wood flour, sawdust, fine sand and glass beads (available in a variety of micro sizes).
Again the cost of fiberglass resin these days is not low... so I'm not totally psyched to go that way. Sticky to wood, solid drying is what I'd like to find, CHEAP!!
Plaster or gypsum materials are candidates, but they'll need to be put in place and then released, then glued into the spot, then the gaps filled after the fact... but that's an extra operation and needs GOOPY adhesive. There isn't much really good GOOPY adhesive around these days. I could probably get away with a well slathered PVA/Titebond to put the cast-in-place part in... but again that pesky extra operation...
_-_-bear
That stock response below 50Hz. is awful!!
I am surprised that you got the final to be as smooth as it is where the 15 incher is running in that cabinet.
Did you mod the box from stock??
TerryO,
I'd advise against using Lime, as lime is very reactive.
Better stuff would include talc, wood flour, sawdust, fine sand and glass beads (available in a variety of micro sizes).
Again the cost of fiberglass resin these days is not low... so I'm not totally psyched to go that way. Sticky to wood, solid drying is what I'd like to find, CHEAP!!
Plaster or gypsum materials are candidates, but they'll need to be put in place and then released, then glued into the spot, then the gaps filled after the fact... but that's an extra operation and needs GOOPY adhesive. There isn't much really good GOOPY adhesive around these days. I could probably get away with a well slathered PVA/Titebond to put the cast-in-place part in... but again that pesky extra operation...
_-_-bear
How about Plaster of Paris? It is available in fast (normal) set as well as slow from some building supply places in 50 lb. bags and it isn`t that expensive. I have plans to cast a couple of large mid horns from the stuff in a pouring mold.
You can imbed wire mesh, window screen or that expanded diamond mesh sheet made for plaster lath walls also available at the same building supply to give what you make some strength. It sands, machines well and can be sealed and painted.
You can imbed wire mesh, window screen or that expanded diamond mesh sheet made for plaster lath walls also available at the same building supply to give what you make some strength. It sands, machines well and can be sealed and painted.
A7 cab
Bear,
The subject has come before on this and other forums. Repeatedly. No surprise, I guess, considering the age and the intended purpose a "pro sound" enclosure, where portability was the primary goal. Perhaps cinema, too, where you're far enough away to not hear the cabinet as much.
Some of this presumes the owner will allow serious mods to the enclosures.
You will need to change out the woofers if deep bass is required. Or, as a friend did, use dual 15s each side to augment the low bass.
Try bracing the interior of the cavity from outer horn walls over to the cabinet side walls with several 3/4" wood dowels. Poplar or the equivalent. Then coat with the kerfed radius with goo of choice.
I bought a gallon of pick-up bed coating mixed with chopped fiberglass at Auto Zone for $12. It ain't purdy and needs serious forced air to carry away the fumes, but works great once set. Something like tar and synthetic feathers. Not for the faint of heart.
A single deflex subwoofer sheet on the rear wall will clean up the lower mids and upper bass once the box is stable and well braced, but carpet pad may accomplish the same thing.
Clay is often mentioned as a filler for the resonant cavities, and for damping the metal horns, but the oil-based variety could, in theory at least, eventually give off enough oily residue to migrate into the driver. Something like creeping ferrofluid ? I doubt this is a real concern unless Exxon or Shell is on the label.
The horn flange mounted to a wood horn enclosure will deaden the HF horns to a great extent. The horn may also be wrapped in a sheets of the latest greatest auto sound damping material, if you have deep pockets. I think reworking the crossover, as the other group project post showed, will effectively remove some of what people may mistakenly attribute to the metal horn ringing. The highs will never be spectacular, but the real goal is balanced and smooth sound, for me anyway.
You could add new plywood sheets to the exterior of the box with long wood clamps, test as needed, then permanently attach if suitable to clean up the unwanted resonance. I tried this on my own boxes and it works well, however now and then you do come up with the odd leftover sheets that only fit the one box . Table saws cure that problem, but at the cost of good 18 mm cabinet grade russian birch ply, this can get pricey. Actually, just clamping the boxes in various places while playing test tones will give you some notion of placement of braces or outer sheets. A pair of long clamps, of course, with wood pads under to span across from front to back, top to bottom, or side to side as needed.
Good Luck
Tim
Bear,
The subject has come before on this and other forums. Repeatedly. No surprise, I guess, considering the age and the intended purpose a "pro sound" enclosure, where portability was the primary goal. Perhaps cinema, too, where you're far enough away to not hear the cabinet as much.
Some of this presumes the owner will allow serious mods to the enclosures.
You will need to change out the woofers if deep bass is required. Or, as a friend did, use dual 15s each side to augment the low bass.
Try bracing the interior of the cavity from outer horn walls over to the cabinet side walls with several 3/4" wood dowels. Poplar or the equivalent. Then coat with the kerfed radius with goo of choice.
I bought a gallon of pick-up bed coating mixed with chopped fiberglass at Auto Zone for $12. It ain't purdy and needs serious forced air to carry away the fumes, but works great once set. Something like tar and synthetic feathers. Not for the faint of heart.
A single deflex subwoofer sheet on the rear wall will clean up the lower mids and upper bass once the box is stable and well braced, but carpet pad may accomplish the same thing.
Clay is often mentioned as a filler for the resonant cavities, and for damping the metal horns, but the oil-based variety could, in theory at least, eventually give off enough oily residue to migrate into the driver. Something like creeping ferrofluid ? I doubt this is a real concern unless Exxon or Shell is on the label.
The horn flange mounted to a wood horn enclosure will deaden the HF horns to a great extent. The horn may also be wrapped in a sheets of the latest greatest auto sound damping material, if you have deep pockets. I think reworking the crossover, as the other group project post showed, will effectively remove some of what people may mistakenly attribute to the metal horn ringing. The highs will never be spectacular, but the real goal is balanced and smooth sound, for me anyway.
You could add new plywood sheets to the exterior of the box with long wood clamps, test as needed, then permanently attach if suitable to clean up the unwanted resonance. I tried this on my own boxes and it works well, however now and then you do come up with the odd leftover sheets that only fit the one box . Table saws cure that problem, but at the cost of good 18 mm cabinet grade russian birch ply, this can get pricey. Actually, just clamping the boxes in various places while playing test tones will give you some notion of placement of braces or outer sheets. A pair of long clamps, of course, with wood pads under to span across from front to back, top to bottom, or side to side as needed.
Good Luck
Tim
Tim,
Thanks for your suggestions... I'll look into the "bed coating"... don't think I've seen that variation of it though.
Wrt the rest, I am extremely well aware of the issues, what to do to solve them, and how to do it.
The point of the post is/was to share the issue with others on this forum...
The cabinet will tune to ~30-32Hz. when done. I mentioned this in my opening post. Different driver, of course.
Not a fan of "deflex"... I think the solution I use is superior, but the idea is similar.
The one single issue that I have been wrestling with is the fastest best way to stiffen and damp the kerfed, thin, exponential section of the cabinet horn section.
_-_-bear
Thanks for your suggestions... I'll look into the "bed coating"... don't think I've seen that variation of it though.
Wrt the rest, I am extremely well aware of the issues, what to do to solve them, and how to do it.
The point of the post is/was to share the issue with others on this forum... The cabinet will tune to ~30-32Hz. when done. I mentioned this in my opening post. Different driver, of course.
Not a fan of "deflex"... I think the solution I use is superior, but the idea is similar.
The one single issue that I have been wrestling with is the fastest best way to stiffen and damp the kerfed, thin, exponential section of the cabinet horn section.
_-_-bear
bear said:
along the line of bedliner. Rhino Liner.
It is rubbery and stays rubbery and a bit flexible. It dries completely. The surface on the base of my pick up bed is at least 1/4" thick.
The only bad part ... it is only professionally installed. So you would need to find a vendor in your area and explain the project to them.
I am sure they would do it though. I have seen entire moto gas tanks, fenders, running boards on trucks ... everything .... even an entire van coated in the stuff.
Find a vendor and feel there samples .... I think it would make a great deadening material.
http://www.rhinolinings.com/
bear said:
What about using Water Putty to fill the kerfs? Same principle which was used on the Insignia mods by Danny over at http://www.gr-research.com/insignia.shtm
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
-Ken
Lots of great info in this thread, keep it up.
Tim: Tar and feather it - I love it!
Is that Durhams Rock Hard Water Putty you have there, KEC? Great stuff. Seems to be mostly plaster.
And speaking of plaster - what about plaster bandages? The stuff that has a mesh built in and comes in rolls. Is that still around?
Tim: Tar and feather it - I love it!
Is that Durhams Rock Hard Water Putty you have there, KEC? Great stuff. Seems to be mostly plaster.
And speaking of plaster - what about plaster bandages? The stuff that has a mesh built in and comes in rolls. Is that still around?
bear said:
The measurments are not anechoic, so the many dips and peaks can be explained by reflections. Above 200Hz, many of the dips and peaks are caused by reflections against the own cabinet or horn.
As usual in my filters, I've put a lot of emphasis on acoustic phase alignment in the crossover region. As this was a 1-day attempt, I haven't done more to improve the result.
The box was indeed from stock. Mechanically it was a disaster as you already mention in this thread, and therefore a lot of bracing and dampening has been applied.
Marc
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