A gross understatement! Drop a modern GPA alum. or Pascalite diaphragm in it and it becomes a much smoother, extended 802 series.
GM
I have been enamored with the Altec stuff for awhile and as fate has it I have a semi local CL opportunity for (3) 511 w/808a for about $100 each. Horns were media blasted and repainted/pretty and new diaphragms in drivers from Simply Speakers. Seems like a decent chance to venture into the Altec world. I just want to get a bare bones horn system going and from the research the best XO is the GPA 19 or equivalent/Zilch diy. Confused on XO points. I know the 511 does 500 but I think that was mainly a cinema thing. IIRC 19 XO does 1200. I want to cobble together a passive XO to at least get it running. Mids are these horns with EVM 15L: http://www.diyaudio.com/forums/subwoofers/275639-id-mid-horn.html For some reason I am not enamored with the tops I have... I guess I don't feel like spending $$$ to fix. Any thoughts or suggestions appreciated. Not looking forward to the drive to acquire... 4 hours+ roundtrip Also contemplating the SEOS 15 with Denovo driver but it lacks the je ne sais quoi of the Altecs...
Actually, the 511 was originally a stand alone PA horn and why the double mounting tabs and no flange mounting holes on the 'A' series with an adjustable wall/pole bracket option.
Later, it was initially used in HIFI/ studio monitor apps, then in theater apps that required greater directivity control such as multiple channel conversions of small mono 'neighborhood' cinemas, etc.. Not sure how much time lapsed in between, though not much as best I can tell since stereo arrived in '57, about the same time as the 511, so may have been designed in anticipation.
When higher power amps became the norm, Altec was forced to first go to 800, then 1200 Hz XOs to protect the drivers as well as tame enough of its 'honk' when driven with a vanishingly low output impedance SS amp, which also of course lowers available efficiency since it's mostly reduced to being a 'rising on axis' WG and turns the 811 into a bonafide WG, the main reason combined with its CD horn EQ that the M19 is considered the best sounding of the consumer Altecs, though I believe that some of the early designs would win out if driven with the period correct electronics they were 'voiced' with.
Unfortunately, the 'voters' haven't, so agree it is in the post analog society, though DIYing new cabs can audibly improve them if taller is acceptable.
In short, if driving the horn with a ~period correct high output impedance, preferably 'matching' or at least has variable DF tone controls, then 500 Hz is fine, otherwise I recommend 700+ Hz min..
This assumes the driver has no loading cap [black Bakelite rear cover], which is normally preferred for HIFI apps. With it, 500 Hz is OK, it just needs its tuning 'hump', faster LF roll-off accounted for in the XO design, i.e. no 'textbook' designs like Altec did to save $$$ plus figured it would be dealt with during the 'dialing in' the audio in the intended app.
Later, they added separate filters to deal with it in some of its studio, consumer speakers, so a DIY option some choose to replicate: http://www.lansingheritage.org/images/altec/specs/pro-systems/9846-8a/page03.jpg
GM
Later, it was initially used in HIFI/ studio monitor apps, then in theater apps that required greater directivity control such as multiple channel conversions of small mono 'neighborhood' cinemas, etc.. Not sure how much time lapsed in between, though not much as best I can tell since stereo arrived in '57, about the same time as the 511, so may have been designed in anticipation.
When higher power amps became the norm, Altec was forced to first go to 800, then 1200 Hz XOs to protect the drivers as well as tame enough of its 'honk' when driven with a vanishingly low output impedance SS amp, which also of course lowers available efficiency since it's mostly reduced to being a 'rising on axis' WG and turns the 811 into a bonafide WG, the main reason combined with its CD horn EQ that the M19 is considered the best sounding of the consumer Altecs, though I believe that some of the early designs would win out if driven with the period correct electronics they were 'voiced' with.
Unfortunately, the 'voters' haven't, so agree it is in the post analog society, though DIYing new cabs can audibly improve them if taller is acceptable.
In short, if driving the horn with a ~period correct high output impedance, preferably 'matching' or at least has variable DF tone controls, then 500 Hz is fine, otherwise I recommend 700+ Hz min..
This assumes the driver has no loading cap [black Bakelite rear cover], which is normally preferred for HIFI apps. With it, 500 Hz is OK, it just needs its tuning 'hump', faster LF roll-off accounted for in the XO design, i.e. no 'textbook' designs like Altec did to save $$$ plus figured it would be dealt with during the 'dialing in' the audio in the intended app.
Later, they added separate filters to deal with it in some of its studio, consumer speakers, so a DIY option some choose to replicate: http://www.lansingheritage.org/images/altec/specs/pro-systems/9846-8a/page03.jpg
GM
The 808 and 802 drivers are exactly the same their were two versions the older ones had a annular slit phase plug then in the mid 70's Altec started using the tangerine phase plug. their were also to different diaphragms used symbiotic witch has a pascalite surround and the newer diaphragm witch are all aluminum. The 902-8a driver uses the tangerine phase plug and has a shorter path from diaphragm to horn and it has a higher gauss as a result it has more extended highs. On paper it seems to be the better driver but more people use the 808 802 style driver with the tangerine phase plug and all aluminum diaphragm. As far as the 511 horn goes in my opinion it's garbage i have owned many Altec speakers over the years and currently i own model 19's but i use a Tractrix horns witch play flat and that has allowed me to remove the compensation network in the model 19 crossover witch really improved the overall sound. Most Altec fans will hate me saying 511 horns suck but they peak the midrange frequency Tractrix horns play flat and sound more real than any other horn ive ever heard.
You're welcome!
Of course not, just use a good XO with some form of CD horn EQ and a bit of extra series resistance to pre-load the amp like me and others do to both 'force' the amp into its linear power band at typical average SPLs and semi-mimic a high output tube amp, though ideally you want an amp with at least the first 10 dB/10 W as Class A with a <80 DF after factoring in the added series resistance as it will otherwise have too much -fb.
GM
I forget whether it is 808 8 A or 808 8B, but one of the two becomes 802 8G as it has the tangerine phase plug. In either case you also need to remove the plastic loading cap, get shorter internal screws and add felt to the rear cap.
As to the fellow way back in this thread who said not to remove the little brace is wrong, especially if you do the horn cuts and fill them in with the rubber stuff. This is precisely what Altec did in the later years, I have a pair they did like this. I always found they rang worse with the brace, cut and rubber filled or not.
I alway prefered the 802 8G, tangerine phase plug, alnico magnets. dont know if I could actually hear the difference, but whatever.
Russellc
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Just depends..... Altec sectoral horns quit being ultra-fi when the high output impedance tube era ended, so early '60s?, though was still 'HIFI' until the Mantaray series came along in the early '80s to be ultra-fi for a short while before Klipsch resurrected the ancient tractrix after driver power handling had gone up enough to trade some more efficiency for a lower flare factor, though still far away performance wise from today's conical WGs due to its rising on axis response same as all the early horn designs before Olson's early conical WG and Altec's Mantaray CD diffraction horn decades later.
Anyway, the 511, etc., sectoral horns can be made quite a bit better overall with tweaking, but as I found out the hard way it's a lot of work to get right and ideally requires two/channel to go fully to 20+ kHz at a relatively high efficiency, so 100% agree that unless you want the kind of speaker used for decades to mix, reproduce movie soundtracks, analog recordings in general, then it's an obvious choice; otherwise for [ultra] HIFI I recommend 'skipping' past the tractrix and even the similar rising-on-axis JMLC horns to conical or the [theoretically?] superior oblate spheroid Dr. Geddes recommends, uses.
For sure, while I enjoy the old horns I guess due mostly from having the vast majority of my total listening time coming out of one model type or another, if I get around to making another horn system it will be some form of conical DSL Synergy concept unless something that performs better to me comes along.
GM
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