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

[Geekstar]

Which horn?

[Coendert2011]

Horn is the 511-E.

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

[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?

[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.

[Coendert2011]

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?).

[vuki]

Since it's A7 cabinet you could try Hiraga's crossover . It's for a multicell horn, but it should be at least listenable. http://web.archive.org/web/200502060...s/HiragaA5.pdf

[Coendert2011]

Thanks,

Unfortunately it is just a simple sectoral horn. I've been lurking for multicells but found the price uncomfortable (>2k$ for 1505). AFAIK the Hiraga filter is tailored to the 15 cell horn with 288 driver. There is even an lift for HF in the curve, that should make things even worse. Currently the 288-8ks spit out way more HF than the 802s.

For now I think this harshness is not crossover related, but I didn't check out other caps or topology.

[Geekstar]

Well, if the horns play well enough to pass with 802s/adapters, I would not expect them to sound totally horrible with 288s.

When I speak out against the 511B, I am being a little bit picky... they are not "needles in ear" bad, just a little hard sounding. I have read forum posts claiming the E is a lot better (with 802s and adapters). 511E is not very common but I am sure somebody around here knows the horn.

If the 802 combo is tolerable, I suspect something more dramatic is at fault than corksniffing horn preferences.

Do you have a test CD or a way to hook up a laptop to the system to run frequency sweeps? Maybe you can hear if the driver is flipping out at certain frequencies...

One other possibility...are you sure the drivers are both wired in phase? Seems obvious but I recently picked up some 802-8Gs and one was wired backwards...that sounded very strange indeed. At first, I thought the diaphragms were fried.

[Geekstar]

On 288 extension:

I found a note from Altec Best on DIY forum saying 288s on 511E are good out to 12k.

Never saw an FR graph but presumably the acoustic EQ of the horn is such that it would bolt right up to a 288 without requiring correction for the old "3k haircut."

Whoa: Found AB's measurements here:

http://www.audioheritage.org/vbullet...on-a-511E-horn

[RonSSS]

Do you have a test CD or a way to hook up a laptop to the system to run frequency sweeps? Maybe you can hear if the driver is flipping out at certain frequencies...
.

I agree. I would sweep them slowly with a low level sine wave and see whare they start going bad. The frams could be cracked in a way you can't see but surely would be able to hear.

Ron