Why do my 288-8Ks sound like cr@p?

**Coendert2011** · May 24th, 2012, 06:05 PM

Hello,

Another little question for the died in the wool experts on this friendly forum.

For years I have a pair of 288-8ks laying around. When I rediscovered these and bolted them to my horn I immediately remembered why they where laying around. Totally unlistanable.
The culprit is that there is some serious HF issue. It's like someone hammering fine needles in your ear. Very unpleasant and very unlike my 802-Ds which are supersmooth.

The units look visually ok and the only thing I can think of is the diaphragm. I've been informing at GPA and they suggested that I measure for problems. I've been planning for an impedance setup, but can't find the time and energy to build it. Otoh I might just not like the character of these units.

Well, before putting them back in the closet, I thought to post first here to inform if anyone had a similar experience or issue with these.

thanks for the help, Coen

**Old Guy** · May 24th, 2012, 06:21 PM

First thing to look for is cheap Chinese frams...

**bowtie427ss** · May 24th, 2012, 06:32 PM

Agree.

Can you post a pic of your phragms?

Are both drivers equally unlistenable?

**Coendert2011** · May 24th, 2012, 06:50 PM

Hi,

Thanks.
I've no easy way of making and adding a pic. Frams are black lipped frames with '1.4-20-035414' and 'Altec Lansing Corp' cast into the plastic. It looks rather original. The rubber gasket of the rear cover was almost glued. I guess they haven't been open for a long long time, you can almost smell the 80s.

No visible damage on the alu dia either and yes both units have the same issue. They are very identical.

**Geekstar** · May 24th, 2012, 07:40 PM

Which horn?

**Coendert2011** · May 25th, 2012, 01:05 AM

Horn is the 511-E.

I've had them on different amp tube and ss...

**Geekstar** · May 25th, 2012, 01:29 AM

I never heard the 511E but if it is similar to the 511B, and I think it might be, that could be your problem right there.

In my estimation, none of the Altec cast aluminum horns are as good as the drivers. Some people like them but I could never make them work. The 511b particularly strikes my ear as rather harsh.

Are you using the 802s on 511s also?

I had 311-90, 31A, 32B, 349A, 511, 811...junked them all. Now retrying the 32B.

I'd say try a good horn...multicell or maybe even a modern creation like a LeCleach. Any 288 in proper working order should be capable of refined smooth sound--maybe even smoother than the 802 (but not as extended on HF).

Maybe you need to clean the gaps on the drivers?

**vuki** · May 25th, 2012, 02:13 AM

You can't just swap the driver and hope everything would sound fine. The drivers have different sensitivity and frequency response so the crossover should be redone. You can't do it without measuring it.

**Coendert2011** · May 25th, 2012, 02:44 AM

Originally Posted by Geekstar

I never heard the 511E but if it is similar to the 511B, and I think it might be, that could be your problem right there.

In my estimation, none of the Altec cast aluminum horns are as good as the drivers. Some people like them but I could never make them work. The 511b particularly strikes my ear as rather harsh.

Are you using the 802s on 511s also?

I had 311-90, 31A, 32B, 349A, 511, 811...junked them all. Now retrying the 32B.

I'd say try a good horn...multicell or maybe even a modern creation like a LeCleach. Any 288 in proper working order should be capable of refined smooth sound--maybe even smoother than the 802 (but not as extended on HF).

Maybe you need to clean the gaps on the drivers?

Thanks. I use the 802 with an adapter, never heard any harshness. The horns are covered with some cementlike stuff and don't ring. They have some nasty peaks when playing loud. They are a little suspicious though, the throat section of the horn is rather ugly. Random blobs of stuff (turned out to be white) Make this a not so smooth transition to the horn.

I have some old pics here: https://picasaweb.google.com/coenski...eat=directlink

I tried to smoothen them out, but got lazy. They are in a hard to reach spot and the stuff is quite resistant too. As a matter of fact they work very well with the 802s at least to my liking.

Without the horn the driver sound 'intense' but not as irritating. You may be right that it is the horn.

I guess gleaning the vc doesn't harm either.

Thanks, Coen

**Coendert2011** · May 25th, 2012, 02:47 AM

Originally Posted by vuki

You can't just swap the driver and hope everything would sound fine. The drivers have different sensitivity and frequency response so the crossover should be redone. You can't do it without measuring it.

Good point. I took a redesign of the co into consideration. Yet I would expect that the whole system would be out of balance, not sounding needly (harsh?).