Altec 511 Horns - Are they supposed to be this squawky?

Hiya,

I built an Altec 211 bass horn and I found some Altec 511 sectoral horns to go with it. I've got Altec 802G drivers and some Emilar EA 175 Alnico drivers to use with the 511s.

The first thing I tried was plugging the output directly from a 35 watt tube amp I built. It sounded horrible: "squawky, honk-y, and harsh" are words I'd use to describe it. I tried it with a few different amps I have and ultimately got slightly better results on that front with a different amp.

I've experimented with a lot of different crossover points and slopes, using a White Instruments 5024 digital processor. To my ears the Emilar drivers are a lot less harsh than the Altecs. I also find that these horns are happiest crossed over at 1000 on the bottom and 4500 on the top. I feel that 24dB Linkwitz-Riley crossovers sound the best.

Anyway, here's the weird part: the only way I can make them bearable to listen to is to apply a -6dB/octave lowpass filter at around 1500hz. This seems to make the 511s sound a lot more lifelike and not physically painful to behold.

i guess I'm looking for guidance. Are horns really this difficult to tame? I've read a lot of posts about how flat they are, response-wise but my experience is just the opposite. Granted, horns do an almost magical thing to vocals and brass instruments, so figuring this out remains worthwhile to me.

Thanks for any experience-based advice anyone has on the matter.
rs

That about sums up my experiences with the 811 and 511. 2K and up is all I could stand. Bought a pair of 2420's on 2307/2310 and sold the last of the ones I had soon after and never went back...

That said, I have heard them sound really nice using the Model 19 crossover that lets you dial in the response you want.

Part of the problem is that the horns are not inherently well damped. At the very least they should be bolted to a heavy plywood baffle board. You will find in various audio forums discussions on what further measures can be taken such as loading down the body of the horn with duct seal, and similar strategies.

Also, unless you are using new diaphragms you are shooting in the dark when swapping drivers and horns around.

With that bass module I think you need a 500hz crossover point and a large format driver. The 1.4" throated Altec series would seem the logical choice. Of course you will need to find the right horns, and they may not be easy to find or inexpensive unless you use some of the later MR series. You will likely want a tweeter horn above 5k or so. Your Alnico emilars on some emilar 1210's would be good for that.

Yes, they need damping for any serious listening. I filled the bells of mine with PL Premium polyurethane construction adhesive, and coated the horn bodies liberally with it. There are lots of other ways people have damped 511s; if you Google you'll find them. For good measure, the flanges of mine are firmly bolted to well-damped MDF boxes. I cross mine at 800Hz; crossing them at 500Hz may be part of your problem with honkiness. As for flat, mine needed various EQ tweaks to get +/-1dB flatness, although to be fair I'm using a TAD driver (TD-2002) not made for the horn. When you measure frequency response be sure to get a reasonable distance from the horn; I measure at about 5 feet away and that seems to give consistent results. They were a bit of trouble to get working right, but they sound neutral and realistic, with excellent imaging and clarity. YMMV, and all that.

Francis

Good people, thanks for the responses. I've actually built baffles for these but didn't have any idea that they would significantly affect the sound, so I've just got one laying on a table to test it. I've also got some very efficient ribbon tweeters to use with these, but the emilar "tweeter horn" is something I'll look into.

Attached is v1 of my baffle system, though I'm probably going to reconfigure them in a more standard "left and right" setup.

These horns are definitely finicky and not without their quirks, but the way they sound dialed-in makes them worthwhile anyway to me!

rs

Quote:

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Originally Posted by speakerdave

Part of the problem is that the horns are not inherently well damped. At the very least they should be bolted to a heavy plywood baffle board. You will find in various audio forums discussions on what further measures can be taken such as loading down the body of the horn with duct seal, and similar strategies.

Also, unless you are using new diaphragms you are shooting in the dark when swapping drivers and horns around.

With that bass module I think you need a 500hz crossover point and a large format driver. The 1.4" throated Altec series would seem the logical choice. Of course you will need to find the right horns, and they may not be easy to find or inexpensive unless you use some of the later MR series. You will likely want a tweeter horn above 5k or so. Your Alnico emilars on some emilar 1210's would be good for that.

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You have a valid point about the damping. In the past I have used that black squishy stuff with the adhesive back to tame metal horns. I think it can be purchased at Parts Express. I have also read some time ago, that some folks lather on RTV on the outer surfaces, but that can get quite expensive, and eventually the RTV will disassociate itself from the horn.

As for a 1.4" throat. ALTEC manufactured the 511E to mate up with the 288 drivers. They are rare as hens teeth on Ebay, and sell for a tidy sum. Bill Hanuschak has experience modifying 511A horns to the 511E in the proper manner. There is no reason a 511 should not sound good, and the basic reason they don't is the crappy dividing networks ALTEC designed. A properly designed network using high quality components can do wonders with ALTEC horns.

H.F.

Quote:

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Originally Posted by ryansupak

Attached is v1 of my baffle system, though I'm probably going to reconfigure them in a more standard "left and right" setup.

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I may not be seeing this correctly, but from your photo it would appear that your 511 horns are far above ear height... realize that if you can't look into the throat you won't hear them sounding even remotely close to what they are capable of sounding like.


Widget

Yes sir you are seeing that correctly, and that is exactly why I'm throwing away v1. :)
rs