Ringing 511B Horns?

I'm running A7s with 511B horns (Emilar EA175 drivers). I'm running the crossover at 800. The horns looked terrible, so I had them powder coated (white!) while I was having other stuff done. Eventually, I'll be doing the cabinets back to factory gray. .

My question is regarding the "ringing" issue people have discussed. I know that knocking on them will produce a ring and damping them will reduce that.

But in terms of actual sonics, what way have people tested the effects of this? If we run a sweep through, is there a frequency that ringing occurs? What methods have folks used to test the practical issues related to ringing and what is the best way to isolate and compare?

I know there's been a lot of discussion regarding various damping methods (tar, sand, Quiet Kote, etc.), but I'm curious about the sonic difference between painted/undamped horns and damped ones? What's the best way to test this?

I've never seen any attempt to define its ringing frequency response, but it's over a wide BW primarily due to bell modes and the fact that if you cut the welds out of the vanes [or cut them out altogether] much of it is gone. Cut the joining welds out and watch the two pieces spring into warped shapes tell you where almost all of the rest of the problem is. Last is the mouth's imperfect termination that sends mass quantities of reflections back to the throat, modulating the diaphragm a bit as the front chamber it too small acoustically to quell them much. These can be reduced to insignificance by adding a suitable foam or other damping material around its perimeter [i.e. foam or similar 'baffle'].

To test, suspend the horn in a large space away from any early reflections and feed it BW limited pink noise to find how each type damping affects its response.

GM

I've wondered the same thing. I have mine out of the cabinets right now, so I'll put an rta on them tomorrow and see what kind of reading I get. I'll try to see what damping does for them, too.

GeeDeeEmm

Not to dispute those who have more experience and knowledge of this topic than I do but...

I have never heard an audible ringing that others say is the main downfall of the 511 / 811. It may be something that needs to be pointed out to be heard consistently. I damped mine with duct seal and that stopped any ringing that occurs when they are tapped when free standing. When they are cabinet mounted, there is very little ringing noticeable. Another option is to not tap them as music does not seem to create the ringing.
I found that there is an audible improvement (that I have no idea how to measure) when the inner weld spatters are filed smooth and the groove between the two halves is filled and sanded. I used Bondo and a round file to do this. This simple change produced a much smoother upper mid and high freq when compared to a pair of stock 811's. It's repeatable and I've switched between them several times with similar results.

I have the filled and smoothed pair of 811's as well as a pair with the vanes cut out (no audible change) and 2 stock pairs of 811's as well as 2 pair of stock 511's. The filled and smoothed pair are in Model 19's with 416-8B's and slightly modified crossovers.

My thoughts are to fill the interior grooves, sand them smooth and repaint the horns. I believe it's the best sound I've got from the 811 and if done right, it's reversible if you don't like it.

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Originally Posted by zelgall

Not to dispute those who have more experience and knowledge of this topic than I do but...

I have never heard an audible ringing that others say is the main downfall of the 511 / 811. It may be something that needs to be pointed out to be heard consistently. I damped mine with duct seal and that stopped any ringing that occurs when they are tapped when free standing. When they are cabinet mounted, there is very little ringing noticeable. Another option is to not tap them as music does not seem to create the ringing.
I found that there is an audible improvement (that I have no idea how to measure) when the inner weld spatters are filed smooth and the groove between the two halves is filled and sanded. I used Bondo and a round file to do this. This simple change produced a much smoother upper mid and high freq when compared to a pair of stock 811's. It's repeatable and I've switched between them several times with similar results.

I have the filled and smoothed pair of 811's as well as a pair with the vanes cut out (no audible change) and 2 stock pairs of 811's as well as 2 pair of stock 511's. The filled and smoothed pair are in Model 19's with 416-8B's and slightly modified crossovers.

My thoughts are to fill the interior grooves, sand them smooth and repaint the horns. I believe it's the best sound I've got from the 811 and if done right, it's reversible if you don't like it.

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Would have a few good pictures of this? I?d like to see how it appears aesthetically.

If you look at how Altec used them, when used with 800 series drivers (511a/b there was no sound deadening applied. When used with large format drivers (511e), Altec applied aquaplas.

I don't think the 800 series drivers have enough energy to make them ring. Especially when mounted to a baffle.

511's always sounded better to me with a stick of duct seal per horn anyways. Maybe it's just in my head.

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Originally Posted by Elitopus1

511's always sounded better to me with a stick of duct seal per horn anyways. Maybe it's just in my head.

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Where are you putting the duct seal?

I used to put it about an inch away from the horn exit. I built a little ridge of ductseal about an inch wide and high, that spanned the length of the horn.

I have seen some guys spread a thin coat of ductseal over the entire outside of horn.

Ductseal works as well for me as anything else I have tried. My Emilar horns are coated with some kind of thick paint. Not sure what it is, but you can pick it off with your fingernail.

My 805's have aquaplas on them. They are coated on most of the horn bell section. Those horns are dead dead

Well, darn it - I forgot to throw my rta on the 511s while they were out of the cabs. But, guess what? It doesn't matter, because even with super-density closed cell foam and old feather pillows tightly stuffed around them in the cabs, they STILL ring - and at what sounds like the same frequency. The only way I can almost eliminate the ring is by damping the outer horn lips - just as Elitopus pointed out.

In the long run, though, it may not matter. Once these are up and running I'll be able to experiment and measure them with and without external lip damping. We'll see what happens.

GeeDeeEmm

If you use big gap filler from the depot, you will find that it stops "all" ringing and you can cut it with a knife, paint it, and it's reversible.