This thread makes me wonder whether the horn or the compression driver come first. Sort of embarrassed to say that I don’t do a lot of experimentation swapping drivers on different horns.
But, and I think I posted this before, I did get a really good deal on a pair of 805b multicellulars along with a pair of very badly rusted/corroded/seized 288c’s and single 288-16k. Kind of miraculously, I was able to dig out the voice coil gaps, but I have no idea whether they’re as good as new. Just ended up with the inexpensive Chinese diaphragms in them. Did some experimentation with aligning the voice coils without shims, just ran a 1k tone and watched the distortion harmonics, tightening, loosening, shifting until I got a good reading. Had to ream out the mounting holes in the cheap diaphragms to get some range of movement. Made a significant difference as I was getting some audible distortion when I just threw them in.
But, I did do some preliminary listening, just hooking up the horn in lieu of my Emilar eh800/ea175 combo, 416 in 620 cabinet.
The 288 k has a lot of output, louder than the c, kind of a more etched treble sound, and the top end falls away at a lower frequency. One might need a super tweeter with the k, which is surprising since the k has the tangerine phase plug.
The k is massive, by the way. Check this out…
Difference in phase plug size from the large vs small format drivers.
But the 288c, although quieter, struck me as having a more extended top. I was thinking that with careful eq, one would probably not need any help.
Both types, with the Chinese diaphragms, i recall having a boost in the very high frequencies with pink noise…wish I had taken a screenshot of the response. I’ve read that some say it’s due to distortion, not the signal, although, I didn’t see that distortion in that area when running 1k tones through them. What struck me was that there was a dip in the 7k-8k, that bugged me. Then they start dropping in the 13k range…the k more drastically than the c, and then further on up, is that bit of bump in the very high frequencies…don’t recall exactly where. But it gives me hope that with eq, kind of like Hiraga’s article suggested, attenuating the mids below 7k, you could flatten them out and extend them. Seems like it would be a different approach…perhaps more complicated…than the small format, 1 inches.
I don’t know if the sound, making no extra effort on the crossover, with cheap diaphragms was a massive difference from the Emilars, but one could easily hear that it had that effortless quality many apply to it, increased dynamics/slam, so there’s some definite potential. Another step towards not sounding like you’re hearing a speaker.
My plan is to put the horns on my 605a/612 combo, possibly use the small horn on the 605a as a super tweeter, but definitely use the woofer. Probably copy the Hiraga crossover from his article. There was a study mentioned in his article, the study investigated the question “do horns have an identifiable sound?” The multicellular Altecs, apparently in a blind test, no one could identify them as a horn. That was the Hiraga comment and in looking over the study, it did seem to confirm it…I think it was in the footnotes somewhere.
So, perhaps the horn is the star rather than the compression driver? I think if I didn’t get the drivers working, I probably would have bought some cheaper large format drivers than Altecs. I probably would not have traded 604’s for a pair of 288’s, either.
All the Altecs are fantastic, and it probably comes down to your room. The large format horn combos are huge. I’m 11 feet away from my speakers and that’s probably just enough for the large format horns. The duplexes or smaller two ways may work better in tighter places.
Also, the paper diaphragms someone reviewed on this site are on eBay for 288’s, so there is another option.
