My A7-500s. A journey

**Panomaniac** · December 2nd, 2009, 04:19 PM

Dave D up in B.C. uses Duct Seal and seems to love it. Does basket mods with it.

My emulsion + sand is a lot of work, but it's cheap and should be well damped. It's an adventure!

**Altec Best** · December 2nd, 2009, 06:15 PM

Pano,

Have you been taking pics of the work I think that could be helpful for others about to undertake this same procedure

**Panomaniac** · December 2nd, 2009, 06:26 PM

Yes - I have pix. Will post. Going to be hard to see the tarred horns - it's dark in there!

**Altec Best** · December 2nd, 2009, 06:37 PM

Great looking forward to them !!!

**Panomaniac** · December 3rd, 2009, 11:01 PM

Well my experiment with the sand mixed into the asphalt emulsion went well.
The emulsion will take a lot of sand! Maybe 2x or more its volume. And even at that it remains workable. But I found that about 3 handfuls of sand into a quart works well, spreads well and does not dry to stiff. The sand tends to stiffen the mixture.

After the braces were in place (see below) I tarred the insides of the bass horn flares. 3 coats on each. Nice and thick, tho not as thick as the spreadable tar. But I can always add more later.

Below is also a photo of the one of the 4 braces I made. I used cardboard to make the template, cut one wood brace and checked it (OK) then made 3 more. They really help.
One thing to look out for. One of the flares came unglued when I was shoving the brace in. All those years, all those bass notes. It came unglued near the mouth, where the driver is. C-clamps and glue fixed that.

They are running now. No extra bracing yet beyond the horn flares. Just a think layer of fiberglass batting on the wall behind the driver to brace the back of the driver to the back of the cab. It pushes tight against the driver. Helps keep driver and back wall quiet.

How do they sound? Strange.... Almost can't hear them. I know that was the goal, but it's still strange to see such a big box and not hear it. Some more well placed braces and they should completely disappear. Not bad for such a big old box.
Photos:

**Altec Best** · December 4th, 2009, 04:03 AM

Originally Posted by Panomaniac

Below is also a photo of the one of the 4 braces I made. I used cardboard to make the template, cut one wood brace and checked it (OK) then made 3 more. They really help.
One thing to look out for. One of the flares came unglued when I was shoving the brace in. All those years, all those bass notes. It came unglued near the mouth, where the driver is. Photos:

Pano, I was thinking about how did Altec let these leave the factory without those braces or some kind of brace in the horn flare.As for the horn flare becoming unglued could that have already been lose and been causing the issues with the flare resonating

Thanks for posting

**Old Guy** · December 4th, 2009, 09:06 AM

I am not sure when the horn braces disappeared. But it was done on a LOT of cabinets.

I chalk it up to Altec's money woes. They had to cut pennies to survive as long as they did.

I can say pretty much every 70's box I have seen had no braces for the horn.

**Panomaniac** · December 4th, 2009, 10:08 AM

Yes- really bad not to have the braces. They are definitely needed. In fact 2 per side should be the norm. And funny that my boxes used smooth ply for the flares. Not kerf cut on the back, like most. So maybe thinner than most. Tho the plywood on the boxes is decent and 3/4".

Yes AB, the flare that was loose vibrated the most. But they all resonated.

I don't know what folks with the sealed off cabs can do. There were versions built were the driver plate goes all the way across, sealing off the back of the flare. No way to get in there and brace it. Maybe pour in sand or kitty litter, as GM suggests. You'd want to be careful not to burst the flares!

The back panel resonates, too. Mostly the lower one now, as I have decoupled the top one to the back of the driver via a fiberglass pad. And the panels around the port resonate. Time for some bracing there. The sides are not too bad.

One thing not shown in the photos is that I loosely stuffed the areas behind the horn flare with fiberglass.

There is a set of big double 15 JBL horn cabs here in town that I know. Awful construction! Thin, resonant, flimsy. So it was not just Altec. Just Big and Loud was also Just Thin and Cheap.

**gearfreak** · December 4th, 2009, 03:52 PM

Originally Posted by Panomaniac

I don't know what folks with the sealed off cabs can do.

We bang our heads trying to decide if it is worth hacking up our NM cabs. ;-)

Considering drilling some pilot holes first for later re-alignment, then seeing if the plate can be removed w/o damaging the integrity of it, or cosmetics too badly.

Probably not going to happen any time terribly soon though.

**Audio_by_Goodwill** · December 4th, 2009, 04:37 PM

Originally Posted by Panomaniac

I don't know what folks with the sealed off cabs can do. There were versions built were the driver plate goes all the way across, sealing off the back of the flare. No way to get in there and brace it. Maybe pour in sand or kitty litter, as GM suggests. You'd want to be careful not to burst the flares!

You won't hurt anything by pouring something in like sand. The only force would be the weight. You do have to be careful if using expanding foam. It the foam expands to much it will start cracking the wood.