After alot of testing and listening, I decided the altec 805b multi cell horns need to stay. They just simply sound better than anything else. I was able to buy a used pair of 10" mid woofers locally for $120/pair. (RCF L10-750y) and installed them in my Onkens by flipping the baffle so the 416 is on the bottom, allow room to mount the mids with a small compression chamber mounted on the baffle. I used a 20uf and 2.0mh 12db slop low pass on them around 1200hz where they cross over to the horns. Much improved sound! I recommend to anyone with a 2 way Altec system to consider a mid woofer. Male vocals, snare, and bass guitar are all more prominent and coherent.
Also, I bought a pair of Alnico Beyma CP-21's for the top. The 288/805b will have a low pass at 7khz. They extend out to past 13khz but there's alot of breakup and not good. Te Beyma's should complete the 4way, and provide equal dispersion charactistics. They are in the mail.
I never seen those in alnico 🙂 I had an early pair of ceramic and they were really good, much better than a new pair I had a couple years ago. The new ones had a real nasty peak around 6K.
Ya, I snatched them. I'm anticipating the older alnico versions are even better. Got them for only $150.
Looking really nice! (that wood floor is killing me) 
Cool idea with the 10" mid. We used 10' mids a lot in pro, with a short front horn. That was back before line arrays took over. I didn't use one on my A5 at home because the short front horn on the 15" woofer seemed to match well with the 1005 horn. But I can see where it would help on the Onken.
Ditto on my 288s. They did go up to about 14K, but it was rough up there. Better to stick a small inductor in series and roll then off at 7K, as you did.
Cool idea with the 10" mid. We used 10' mids a lot in pro, with a short front horn. That was back before line arrays took over. I didn't use one on my A5 at home because the short front horn on the 15" woofer seemed to match well with the 1005 horn. But I can see where it would help on the Onken.
Ditto on my 288s. They did go up to about 14K, but it was rough up there. Better to stick a small inductor in series and roll then off at 7K, as you did.
Yeah, these drivers were designed to roll off at ~3 dB octave above ~2.5 kHz when behind a screen and movie soundtracks were physically limited to something like 9 kHz/F6, so folks who use them any higher have more tolerance than me, at least before my HF hearing went away. I haven't auditioned one in decades though, so just assuming.
'Different strokes' WRT using a 'small' filler driver with a multi-cell or other large compression loaded horn. For me and many others, using dual HE 15" with at least one being optimized for a wide BW mid-bass for the 'filler' allows the 288 to operate at a low enough power to XO at 500 Hz due to a better matching efficiency and polar response where the sonics of a compression horn is superior to any cone driver except possibly a smaller ultra low Qt Lowther or similar limited to a fairly narrow BW.
GM
'Different strokes' WRT using a 'small' filler driver with a multi-cell or other large compression loaded horn. For me and many others, using dual HE 15" with at least one being optimized for a wide BW mid-bass for the 'filler' allows the 288 to operate at a low enough power to XO at 500 Hz due to a better matching efficiency and polar response where the sonics of a compression horn is superior to any cone driver except possibly a smaller ultra low Qt Lowther or similar limited to a fairly narrow BW.
GM
The Altec 1285 xover has a selector switch on the back to switch between 500/800/1200hz xover, which easily allows for quick A/B'ing. I have found that even though the 288/805b can extend easily to 500hz, I wouldn't nessesarily call it superior in that range. I find the metalic 'horn sound' is more prominent when going too low. The challenge for me is it's the only horn in a direct radiating system, so avoiding that sound is a priority. Also I considered a dual 15" approach, but caused more problems than it solved. #1 being it would have screwed up the onken bass reflex tuning and pushed it way too high, whereas now I have a pretty flat output down to 30hz. #2, as good as the 515-8g is, it doesn't sound as clear in the 500-1500hz range as the 10" RCF, especially revealing in lower male vocals. It's still early however, and I still have to adjust the dampening and tuning slightly. I'm usually against modern pro audio stuff, but this midbass has a very powerful motor and very light weight cone-hard for a 15" to compete with.
That's strange. The 288/805 extend out past 13khz on my REW test mic, with a nasty peak at 10khz. I certainly plan on adding a low pass. Unless the Hiraga xover has some sort of correction circuit?
This is pretty much what I plan to do. Good to hear that somebody with a lot more experience is recommending it. I'll bend it a bit by using a 700 Hz crossover between the 515 and HF horn, but Altec freely used both 500 and 800 Hz crossovers in their designs, so it'll probably work.
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Just so we're clear, I wasn't 'attacking' your choices nor promoting mine as superior for your app, just that any filler driver to a horn be sized correctly and that in mine any many folks experience over the decades have found by both listening and measurements that through our acute hearing BW a point source driver can't compete with a properly implemented compression driven horn [particularly WG] except over a very narrow BW, i.e. just enough to fill a dip in the response as is sometimes used when one doesn't want to sacrifice too much of a large woofer’s high power handling capability when mated to an acoustically tiny [super] tweeter [horn].
WRT to your app, yeah, if the horn isn't well damped, especially a 'tin knocker' made multi-cell, then up to a ~2.5 kHz XO is sometimes the only 'minimalist HIFI' option when driven with a low output impedance. Ditto the 511 if not heavily tweaked.
There's a very good reason the originals were tar filled as mine were, so even if yours are 'lucky' enough to have a heavy AquaPlas coating [precious few are AFAIK], it's still a 'ring-dingy', 'tin pan tootin' megaphone when 'pushed', i.e. not a driver problem per se except for being powerful enough [with a loading cap] to overload the horn throat into audible distortion when coupled to a 500 Hz multi-cell.
After all, it was originally designed for a 300 Hz low power, matching impedance system, ergo is just ‘loafing along’ in a properly implemented 500 Hz system even at a somewhat higher power, though of course nothing like what some modern compression drivers can dissipate.
Factor in that over time the solder joints can crack if not encased in tar, sand, Portland cement, lead 'shot' or similar high density damping material leaves me with little interest in recommending/gambling on any of the non-tar models without actually auditioning them with no XO to ascertain how structurally sound they are. Some just need a light tap from a hammer or similar to tell.
Note here that until circa 1970, Altec's XOs for woofer/horn combos were 'gapped' to time align them as much as practical, so an 800 Hz XO didn't mean it was the horn's, just some point along a curve, with the horn being somewhat higher depending on the woofer
There's much more to this 'story', but I digress too much already and what with today's XO computer design capability combined with relatively inexpensive adjustable digital XO, TD modules it's not really worth knowing unless one wants to get the most out of analog [passive] vintage systems.
Hmm, again, I wasn’t questioning/damning’ your driver choice, design trade-offs as obviously the Onken would require blocking off most/all the vents to lower tuning enough to accept a second 416/515 or even a modern 15” low Vas [mid]bass horn driver, probably rolling off the bass too much in the process and without a properly damped multi-cell combined with an optimized signal chain, you’re technically right as well WRT to a ‘small’, optimized mid-bass woofer sounding superior, though again, not a compression driver problem per se as some claim.
GM
I know, I was just sharing my findings. Thanks for the informative post GM.
I heard tar filled horns at a gentlemens home in Ottawa and they sounded very good. They were early 1 peice cast multicell Altec's (808?). He collects early "red white and blue" altec stuff. I didn't know what that meant at the time, until I started researching and saw the bonkers prices the really early stuff fetches.
My solution of adding a 10"'mid bass is sorta in keeping with the demise of Altec when JBL introduced the 4300 series. I can see how adding a mid bass and slot tweeter to Altec can be seen as 'Altec Heresy'! (Not that you're saying that)
http://www.audioheritage.org/html/history/jbl-pro/1970s.htm
Strips of wool carpet underlay stuffed between the cells does a good job at killing ring. My 1005s and 803s were aquaplast coated, so not very ringy.
Don't recall ever trying wedging any wool/whatever insulation between cells, but I imagine layers of the old, thick, jute padding used under high end/best commercial carpet to get that shoe insert 'air cushion feel' would really help; ditto 'framing' its mouth with a really thick rubber 'gasket' or even a plywood one to do double duty as the stand if 'floated' on a silicone caulk 'seal' similar to what I've seen done in some baffle mounted cab combos.
GM
GM
beautiful setup
does anyone here know if the cheap aftermarket diaphragms for 288/290-1 are decent? I've had a pair of old alnico Altec sitting for over a decade somewhere in my mess needing new diaphragms - horns are 203B
does anyone here know if the cheap aftermarket diaphragms for 288/290-1 are decent? I've had a pair of old alnico Altec sitting for over a decade somewhere in my mess needing new diaphragms - horns are 203B
Check with Great Plains Audio to see what they have. Phone call is best. I bought from them and as happy.
The old large and small format Radian replacements touted as being as good as originals were fine except for a more rolled off top end and actually could handle a bit more power, but don't know of any current units being available except for GPA, so I assume for now that they're either basically Radian or junk.
GM
GM
My 4 way system finally moved into the renovated living room!
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You're welcome!
Yes, [Altec] Lansing H808, highly prized and audibly superior to its 811 replacement.
Finally remembered the model number of Altec's [Japan spec] 9862 studio monitor with its 414, 416 combo to bridge the gap to a small diffraction WG and 'topped off' with a small super tweeter to counter the 4300 series, so hardly 'heresy' 😉, just apparently not the type of speaker alignment they were interested in [ditto its WG] until someone was willing to fund the project: The Altec "4343" - Page 4https://www.google.com/search?q=alt...ved=0ahUKEwjY05-EkOrJAhWMPT4KHQ2ABdAQ_AUIBygC
FWIW, I forget which member ATM, but there's a similar DIY version using a different horn on the Altec Forum:
GM
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