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View Full Version : They Don't Call the Mouth of the Horn the Bell for Nothing



toddalin
10-17-2008, 11:54 AM
I took a pic of the spectrum produced by tapping on an H92 with a small metal hammer. Note the two promenent frequency spikes. The decay time was on the order of a second.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Concrete_Rocks/DSC_0001.jpg

grumpy
10-17-2008, 01:05 PM
If you're able (and have time) to do the same test with the horn mounted to a
chunk of mdf (roughly baffle-size :)), then, with it mass loaded on -both- ends
(attach a driver), it would be (more) interesting... either that or a lot less interesting.
Something to be learned, in any case.

toddalin
10-17-2008, 01:16 PM
If you're able (and have time) to do the same test with the horn mounted to a
chunk of mdf (roughly baffle-size :)), then, with it mass loaded on -both- ends
(attach a driver), it would be (more) interesting... either that or a lot less interesting.
Something to be learned, in any case.

A possibility once I remount the horns. But, at that point they will have a plasticized coating on them, so the test really wouldn't be valid.

At this point, I've already painted the inside of the horn used in the test (that had been stripped by a prior owner). I found with the finger taps that even the coating JBL puts on the horns provides some (but not much) deadening to the ringing.

(BTW, JBL certainly could have done a better job of casting these things. Once the paint is removed you can see all the flaws and seams in the metal-work.)

4313B
10-17-2008, 01:58 PM
(BTW, JBL certainly could have done a better job of casting these things. Once the paint is removed you can see all the flaws and seams in the metal-work.)They did what they were supposed to do. The old aluminum transducer frames also have voids which were undetectable until you start sandblasting them.

You could always have a pair made out of sonoglass.

grumpy
10-17-2008, 02:02 PM
OK. I can see a weekend of playing with 2312's on the horizon.
I've got a contact mic to play with as well (pseudo-accelerometer).

Will be interesting to get your opinion on your 2307->2312 system mod
once completed. :cheers:

Beowulf57
10-17-2008, 02:11 PM
Me too:duel:...the battle of the horns is on. I'm all ears for the comparison!

P.S. The ringing is reduced by attachment to a baffle, but still present and some form of coating helps to deaden it even further. Attachment to a driver alone however, made very little difference as the horn is still hanging out there in space, ringing like a bell.

grumpy
10-17-2008, 02:49 PM
Attachment to a driver alone however, made very little difference as the horn is still hanging out there in space, ringing like a bell.

... as one should well expect. Frankly, once mounted, I expect it to be difficult to
measure an audible, mechanical resonance, but it's an excuse to dust off some toys
and I might accidentally learn something :)

subwoof
10-17-2008, 07:04 PM
I used to keep an altec 811B horn suspended in the shop by a fishing line for customers to whack on with a 2X4.

The horn would ring at about 1.1K for MINUTES and this is why I was able to sell bands on the aquaplas coated horns or at the least, make them cabinets that properly mounted these type of horns...

Go to an auto finishing supplier in your area and coat the back of the horn with undercoating. Today there are a number of sound-deadening products for the automotive market that would work even better.

*ding*
"the note that goes on forever"
For bonus points, name the song/artist/album
:cheers:

hjames
10-17-2008, 07:44 PM
I used to keep an altec 811B horn suspended in the shop by a fishing line for customers to whack on with a 2X4.

The horn would ring at about 1.1K for MINUTES and this is why I was able to sell bands on the aquaplas coated horns or at the least, make them cabinets that properly mounted these type of horns...

Go to an auto finishing supplier in your area and coat the back of the horn with undercoating. Today there are a number of sound-deadening products for the automotive market that would work even better.

*ding*
"the note that goes on forever"
For bonus points, name the song/artist/album
:cheers:
A Day In the Life - The beatles - Sgt pepper ...

loach71
10-17-2008, 09:09 PM
To damp my 2350 horns I purchased a "schutz gun" and some gravel guard from an auto parts store. I sprayed on a liberal coating of the rock guard to the outside of the 2350s with the schutz gun and the bell-like ringing disappeared. The rock guard smoothed out the crinkle texture of the aquaplas, and once dry accepted a coat of gloss black enamel quite well. Total cost about $15 per horn.

Tim Rinkerman
10-20-2008, 06:35 AM
There's a good reason that old multi cells were made of lead and filled with tar!

robertbartsch
10-29-2008, 12:37 PM
34 years ago, I bought a pair of VOTT speakers with the 800 series metal horns mounted in furntiture cabinets. From what I remember from owning them for about 25 years is that they did not RING.

The old light green horns were not coated from the factory.

Recently, I purchased a single 500 series Altec horn for a HT center channel and it rang like a church bell. It was not mounted in a cab but just hung bare in the TV table.

The new horn is sitting quiet in the basement where it is likely to stay for at least the next 34 years.

Robh3606
10-29-2008, 01:36 PM
What happens when you have it mounted to a baffle board??

Rob:)

robertbartsch
11-06-2008, 11:43 AM
Well, the horn was intended to fit in a TV cabinet shelf as a component of a center channel in a HT, so I have not tried to mount the 811 Altec metal horn in a baffle.

Since I have a few fiberglass/plastic horns that do not ring, I'm using one JBL horn designed for a 2426 for this purpose.

Since they have had "glass/plastic" technology for many decades, I wonder why the old metal horns were in production for so long? I assume it has always been less costly to make a plastic horn; right?

Oh well, I suppose these poor management and marketing decisions led to the downfall of the once great Altec Lansing corporation.

One thing I will say about the old Altec horns. They were very effecient. I assume this has something to do with the shape where the waves first expand in the horn, then contract in the horn, and finally expand again near the end of the horn. Most newer horns only allow the waves to expand; right?