Horn Damping

[Pano]

So as to not threadjack Bear's A7 thread, here is a thread about horn damping. It's been covered before, but is worth repeating.

I had mentioned good results using Blackston automotive damping tar on the back of the kerfed plywood horns in an Altec A7 cabinet. Others had other suggestions.

Speaking of Bondo for damping Evenharmonics says:

Originally posted by Evenharmonics
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.

tt398 had this to say:

Originally posted by tt398
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.

My question. Does Gravel Guard come in spray cans? They would be easier, or at least cheaper for those of use who don't have a compressor and spray gun.

FWIW, I have 811B horns that rang until they were tightened into a frame. Once the front and back were bolted tight to wood, no more ringing. There is a slight ring still on the front edge, but that should be easy to cure.

Anyone else have good or bad experiences with horn damping they would like to share?

[Evenharmonics]

I’ve seen a picture of Altec 511B horn with latex paint mixed with sand and brush applied to dampen it. It would be cheap and quick way to do it but I don’t think it’s as good as Bondo due to limited thickness the paint can hold before start cracking when dries.

If the horn will be covered with enclosure or something (except for its mouth), then the appearance won’t be much of an issue, in which case you can use gravel guard spray / brush on. If it will be highly visible, I would suggest taking it as if it’s your car’s fender – Bondo, sand, prime and paint to match your décor.

[Zen Mod]

most effective way certainly is making box sand for horn,where driver end is enough protruded on back of box , so messing with driver doesn't mean digging horn from dirt

where this solution from any reason is out of question ,multiple coating with any sort of Gravel Guard is best ........ comming from entire different area I can just guess by name that's coating made for shielding auto chassis bellow doors......brink?

cheap and robust solution is also using felt strips mixed with any tar based coating

edit:
I guess that Gravel Guard can't be in spray doses......it isn't enough viscous for that

[tt398]

Originally posted by panomaniac
So as to not threadjack Bear's A7 thread, here is a thread about horn damping. It's been covered before, but is worth repeating.

I had mentioned good results using Blackston automotive damping tar on the back of the kerfed plywood horns in an Altec A7 cabinet. Others had other suggestions.

Speaking of Bondo for damping Evenharmonics says:


tt398 had this to say:



My question. Does Gravel Guard come in spray cans? They would be easier, or at least cheaper for those of use who don't have a compressor and spray gun.

FWIW, I have 811B horns that rang until they were tightened into a frame. Once the front and back were bolted tight to wood, no more ringing. There is a slight ring still on the front edge, but that should be easy to cure.

Anyone else have good or bad experiences with horn damping they would like to share?

I like the schutz gun -- it lets me quickly lay down a thick coat of this stuff -- very handy when doing a large horn like a JBL 2350. Gravel Guard is available in large aerosol spray cans. It stinks like heck when you spray it - a job best done outside. Once dry it has no odor -- and it does a good job dampening the metal horn resonances.

[bear]

The very very best way to fix a 511 or 811 horn is to crush it in a car compactor.

Of course the sandbox technique is very good, but heavy and hard to move.

The goo on the backside, whatever it is works ok.

The aluminum is already stiff - so it only need to be damped.
Otoh, the Altec Multicells are NOT stiff, and need to be stiff and damped. The old tar + lead that they had gooped on the back of them tends to delaminate off the thin metal. Thus the higher regard for the "tar filled" versions.

Automotive pick-up truck "bed liner" material is worthy of consideration as a DIY paint/spray on for damping.

The problem with the A-7's mid-bass horns is that they are thin plywood, and connected to the LF volume, they need to be stiff to control the bass energy, and to not ring with the midbass energy. So imho, damping is insufficient but necessary for them...

_-_-bear

[Cal Weldon]

Originally posted by panomaniac
Anyone else have good or bad experiences with horn damping they would like to share?

Not necessarily good or bad but I did find that you need to damp only the lips of the 811/511 horns. That's where the ring is coming from. Damping material on the back behind the flange is IMO a waste.

[Pano]

So you are just putting bags of wet sand in the top lip?
Wet sand I have plenty of - I live on Maui.

[Cal Weldon]

Yes and since I have the 811 stacked on the 511, I'm a double bagger.

I only did it while working on the XO and notch. When they are outside screaming away, I don't bother. The ring is far, far quieter than the music.

EDIT: I believe you are a little south of my parents up in Kihei no?

[GM]

Originally posted by bear
Automotive pick-up truck "bed liner" material is worthy of consideration as a DIY paint/spray on for damping.

The problem with the A-7's mid-bass horns is that they are thin plywood, and connected to the LF volume, they need to be stiff to control the bass energy, and to not ring with the midbass energy. So imho, damping is insufficient but necessary for them...

Greets!

It works very well and often used to brush, roll or spray whole PA cabs.

Very true and why if you have 825 cabs the horn sections need to be blocked off and all series filled with kitty litter or similar. Some folks claim the expanding foam will do the trick, but I'm skeptical. If anyone tries it though, be forewarned that if you aren't careful you'll either bulge or completely blow out the thin plywood flares.

GM

[GM]

Originally posted by Cal Weldon


Not necessarily good or bad but I did find that you need to damp only the lips of the 811/511 horns. That's where the ring is coming from. Damping material on the back behind the flange is IMO a waste.

Hmm, for sure that's where it's worst, but my experience has been that the dip between the throat transition and mounting flange benefits from plenty of damping in a HIFI app.

GM