Horn Dampening--811B

[Shane Shuster]

Has anyone charted the sound that comes from 811Bs, ring or not, before dampening and after dampening?
Gary

I had 511Bs that I damped using putty. They were mounted using the front baffle and from the rear. The frequency plot was so close as to be identical. Same with taking out the bug screen.

If you don't have them screwed down I would recommend that instead of messing with putty, dynamat, ect. Its easier and cleaner. I think guys hit the horn with their hand or an allen wrench and imagine the ring is worse than it is. I think its a scapegoat for the horn/driver combo's limitations.

If you do want to damp it you can kill the ring best by focusing on the middle of the upper and lower mouth lip.

[Mr. Widget]

I had 511Bs that I damped using putty. They were mounted using the front baffle and from the rear. The frequency plot was so close as to be identical. Same with taking out the bug screen.

I don't know what you were using to generate your FR plot, but I have discovered that when comparing different amplifiers, the FR plot that I got using CLIO to measure the outputs of the speakers will not change at all at times and very, very little at other times... even when zoomed in enough to readily see 0.25dB changes and yet the sound is distinctly different.

If you don't have them screwed down I would recommend that instead of messing with putty, dynamat, ect. Its easier and cleaner. I think guys hit the horn with their hand or an allen wrench and imagine the ring is worse than it is. I think its a scapegoat for the horn/driver combo's limitations.

I agree. Baffle mounting any horn will affect it's performance... typically for the better. This is partly due to effectively adding mass and reducing the resonant frequency, but also it aids in the acoustic coupling to the room. I do think that dampening these horns is a good idea, but the effects are subtle as there are other "horn/driver combo's limitations"


Widget

[Steve Gonzales]

"Filter" presumably incudes equalizer.

So, we have determined the "ring" is at 4 kHz, have we?

I should just shut up, rather than sayin' stuff folks don't want to hear here.

Slide over, Giskard, buddy....

Naw, don't go and do that Zilch. I appreciate the science and the measurements you share ,although it hasn't seemed that way in the past. Any serious speaker system that JBL, or any other company has ever produced, was engineered/R&D'ed within strict science based guidelines, and wouldn't be anything near as good without those calculations/principles. I want you to know that my arguement in the past has been for a balance here on the site in regards to how much importance is placed on raw data over how something actually sounds in someone's system at home. Numbers don't always tell the whole story and ears can't always be used to get the most out of a system. I feel the need to go the record with this because I want you and everyone else to know that I respect and admire what you do here. I don't want to be thrown in the "anti-science crowd" because there is a HUGE difference between the aforementioned balance and the complete lack of respect for science demonstrated in certain posts within this thread. I hope you recognize that. Thank you Zilch, for what you do for the benefit of this Forum, Regards, Steve Gonzales

[Shane Shuster]

I don't know what you were using to generate your FR plot, but I have discovered that when comparing different amplifiers, the FR plot that I got using CLIO to measure the outputs of the speakers will not change at all at times and very, very little at other times... even when zoomed in enough to readily see 0.25dB changes and yet the sound is distinctly different.
Widget

I don't use anything as precise as you. I usually listen, then measure, then listen again. With the bug screen I didn't hear a difference, then measured, saw no change. Dampening the horn I thought maybe I heard a difference, then measured, no change. Listened again and thought I heard a difference. I left them damped for 4 months then decided to take the putty off. I did not hear a difference with the putty off, the new mod effect must have worn off over the months.

I think its a small enough difference that if you want to hear it you will, and if you don't, you won't. I'd take the cheap and easy way out.

But if you have the horn just laying on a bass cabinet with books propping up the back, it would help to damp the horn.

[Steve Schell]

This business of ringing horns reminds me of the similar controversy over compression driver rear caps and their removal or lining with foam or felt.

I once measured a bunch of JBL 2440 drivers on a 2350 horn with and without the rear caps in place. There was virtually zero difference in the response curves with the caps on or off. I have always preferred the sound of compression drivers with the rear caps removed however, so either I'm nuts or the FR measurements are missing something that I am hearing. I think it is the latter.

It is probably the same situation with cast metal horns. One fellow described to me an AES paper that he had read that discussed pre-echo in cast metal horns; I have not seen the paper. Apparently when driver energy hits the throat, the resulting vibration can travel through the metal horn and radiate from the mouth well ahead of the corresponding sound waves in the air column. This creates some confusing information for our brains to unravel, yet this artifact would probably be many dB down and not easily seen in conventional measurements.

[hapy._.face]

At higher volume levels- the ringing of the 811B is real and audible. Granted, they were never intended for higher volume level playing in the first place.

The ringing is not audible by itself but there is a bell sound to all the music coming out of it- like a harsh reverb. It's annoying.

Another thing to consider is the vibrations from the other drivers in the same cabinet impacting the horn. I prefer to mount (not sit) the horn outside of the cabinet.

All of the above mentioned ideas are great for sound isolation, but it won't make them stop vibrating. To do that- you need mass. A sand filled balloon in the scoop of the horn's front is ugly but very effective. I suppose one of those notepads might do the trick, too. Perhaps even concrete..(?)

When you eliminate the ring- you have yourself a pretty nice horn. They do 800Hz much better with some weight in them; I like them just fine for my purposes.

[loach71]

100% transparency cannot be achieved without an unacceptable loss in pertinent musical information
after lots of attempts late last night, I stand corrected
I'm leaving mine alone, they'er still the best.

anybody up for shots o Yagermeister
35% non placebic

Make mine single malt scotch...
Jagermeister reminds me of Buckley's cough syrup!