I always drool when I see that pic Cal. Beautiful multicells that look to be in excellent condition. Did the ever do tar filled versions of those giants? Must have needed a crane to position them if they did.
I'm gearing up to do some measurements, err sometime... 😛
Anyway this tutorial looks good if you've haven't used HOLM before.
HOW TO: Measure using HOLM and ARTA - AVS Forum
I'm gearing up to do some measurements, err sometime... 😛
Anyway this tutorial looks good if you've haven't used HOLM before.
HOW TO: Measure using HOLM and ARTA - AVS Forum
What happened when you ran your 288's down to 300hz? I spoke to Bill at GPA and was told the 288's have an extremely low fs, below 20hz. Obviously excursion could be a problem, but at home listening levels and a 4th order slope x-over, that shouldn't be a problem.
I've also read that it's a good idea to cross well above the horns lower cut off to avoid any honking, but I've always preferred to push the sound of the CD/horn to their cut-off (or a bit below). Maybe my DIY mid-bass horn has issues.. 😛
At any rate these 1003 horns 288 (RWB's) were speced together as a PA system for Denver's Union Station. At least that was the story that went along with the sale, and judging by the many layers of paint shared between the two, I'd believe it 😀.
I also forgot to mention, another advantage of the 1505, over the 1003 would be smoother FR due to the larger mouth. However the band pass might be too high for this to come into play - can anyone comment?
Clarification...
Steve,
Thank you! Very useful link... But this was not the question. I would like to compare the performances of my 1505B and 291-16B with others.
I have measured a frequency curve which is slightly different from what I have found in litterature (Jean Hiraga). In fact, the curve is OK when I measure at the horn mouth, but the high fequencies start to drop from 2000 Hz at about 6db per octave when I measure 3 ft from the horn.
I would like to check if others have found the same thing. I am not using Altec genuine throats and I would like to be sure that this is not a problem specific to my setting.
Steve,
Thank you! Very useful link... But this was not the question. I would like to compare the performances of my 1505B and 291-16B with others.
I have measured a frequency curve which is slightly different from what I have found in litterature (Jean Hiraga). In fact, the curve is OK when I measure at the horn mouth, but the high fequencies start to drop from 2000 Hz at about 6db per octave when I measure 3 ft from the horn.
I would like to check if others have found the same thing. I am not using Altec genuine throats and I would like to be sure that this is not a problem specific to my setting.
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So they're down 18db @ 8Khz?! 6db/oct from 2000hz sounds very wrong but then again I'm not that familiar with the 291.
Can you take them outside and measure just to be sure? Is your mic calibrated?
I never measured my but by my ear and that is why I went to the super tweeter. The 1505 started sounding a little dull above 8k.....livable, but dull. I cross it to the tweeter at 7k with a 24db slope and it transition very nicely.
When I cross the horn to the woof below 700hz, it started sounding honky.
When I cross the horn to the woof below 700hz, it started sounding honky.
My Altec 620A
I like to show you my Altec 620A tri amped with 604-G's and an AH midrange horn/Altec 802.
The speaker was removed from an Ontario movie theatre in ca. 1982, it served as one off the surround speakers there. The bass driven with a Technics SE-9060 dual mono power amp, the mid and the HF horns are driven with a 4Ch hybrid 6DJ8/Hitachi lateral MosFet amp. The 3 way electronic xover was build after an eighties Elektor article , the frequencies are 800/5000Hz. The speaker has the usual very relaxed Altec sound and no noticeable honk. I originally used the 511 horn for the midrange, but I had to change it , because of the very disturbing honk.
I like to show you my Altec 620A tri amped with 604-G's and an AH midrange horn/Altec 802.
The speaker was removed from an Ontario movie theatre in ca. 1982, it served as one off the surround speakers there. The bass driven with a Technics SE-9060 dual mono power amp, the mid and the HF horns are driven with a 4Ch hybrid 6DJ8/Hitachi lateral MosFet amp. The 3 way electronic xover was build after an eighties Elektor article , the frequencies are 800/5000Hz. The speaker has the usual very relaxed Altec sound and no noticeable honk. I originally used the 511 horn for the midrange, but I had to change it , because of the very disturbing honk.
Attachments
They just didn't play that low. And distortion started to rise quickly in that region, maybe around 400Hz - I'd have to double check. I don't think it was a limitation of the horn, but the driver. My drivers started life as 291s, but I put GPA 228 'frams in them. Same motor a 291/288, different diaphragms.
I have not measured the 1505, but the 1005 starts dropping above ~7KHz with my drivers. That's about where I bring in the tweeter.
I wonder about those Westrex drivers that Mr. Hiraga has on his A5s. They are supposed to be equivalent to the 288, but they don't look like them. And I never ran them with tweeters, even tho Hiraga did. The tweeters did add something, but I found them unnecessary. Maybe the Westrex have a better top end?
The mic is not calibrated, but as the curve is good when the mic is closed to the horn mouth, by comparison, I do tend to believe that the mic is not the reason of the issue. I made a mistake with the 6 db per octave. I am at home now and I attache a picture showing the measure (ble close to the horn, red 3 ft).
I can correct it using the preamp which is offerering a +10 db correction.
With the corrective curve, the result is very good (measures and listening)
Second image show bass and medium corrected.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
That looks better than what I've been seeing with the 291+1005. I'll have to run a few more sweeps and post here. Thanks for your graphs.
You're welcome! All around the HF horn to quell any reflections just like the picture shows.
GM
Greets!
The driver access cover is of course, but the main rear panel where the XO is mounted should be glued in on the 825, which he seems to have. The 828 has a full height removable rear cover that's reversible IIRC.
GM
Nope.
djn appears to have a very reverberant room, so combined with a pair of such large multi-cells, I imagine he sits well within their near-field, probably even closer than with the 825, so a very spacious, if not near holographic presentation, is possible with a good stereo recording. I experienced it regularly when I had stacked 511s on top of 211s. Telephones ringing, doors slamming, chairs being slid around, etc. off screen and behind me on some movies and TV shows would sometimes have my head jerking around involuntarily.
My fave was a sequence on one of the early Pink Floyd albums where you hear someone climbing up steps and chasing/swatting a fly around the room and finally splatting it. Well, in my other house the acoustics were such that it sounded like they were climbing up a stairwell behind the sofa, chasing the fly around the sofa and splatting it on the coffee table in front of us! It really unnerved some folks. In my current room with only a single 511 on top of dual 515s, the sound-stage isn't nearly as tall/deep, so everything happens between the speakers and sofa and it's a somewhat shallow stomp up the stairwell.
Just one more reason why I advocate large mids systems with low XO points, though I still contend that multi-cells per se are a bit too 'colorful' for all but the largest HIFI/HT apps if not XO'd to a super tweeter system in the 3 kHz region, in which case the basic horn without all the individual cells should suffice. Such a horn should be easy to DIY, so rather surprised no one on any of the forums has done it AFAIK except 'in the round'.
GM
Nice! Yeah, the 511 needs a bit of tweaking and/or a ~1200 Hz XO to roll it off enough down low to avoid its 'honk'.
GM
I think they are 1804's. All 18 cell Altec Multi's are dual driver only the 1505 had a single throat out of the Big Multi's 1505,1803,etc.
Altec never made a 500 Hz 18 cell I'm pretty sure,they made 1803,1804,only IIRC
For the honk on the 511 you just need the E variant that is covered with Aquaplas.I think they are much,much better than the regular 511.With the 21216 attachment you can run small format 802,902,etc.. with them too.
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Cal's are 1803's that came standard with a single driver waveguide and a 24 ohm 288. The 1804 was the dual 288. No such thing as an 1805 AFAIK.
Hmm, the old data I have says all the large format multi-cells can be (1) or (2) driver loaded depending on the adapter/throat combo and the 1004, 1504, 1804 can be loaded with (2) dual driver throats, i.e. (4) drivers, making for 100+% eff.! with 290s.
Well, the 511E is an alternate way to reduce it somewhat since its 1" throat is sawed off and re-flanged to accept a 1.4" throat driver, but the trade-off is reduced HF extension, so for some (many?) folks it's not an acceptable alternative.
Note too that adding gasketed joints via adapters to it shouldn't yield as smooth/extended a response with the same polar response as the 1" throat 511 if my tweaking experiments with the latter combined with scratch building a variety of horn profiles with differing throat diameters is any indication. Only one way to know for sure though.
GM
edit: Found my catalog data sheets in pdf format: http://www.altecpro.com/pdfs/vintage...ar Horns.pdf
Well, the 511E is an alternate way to reduce it somewhat since its 1" throat is sawed off and re-flanged to accept a 1.4" throat driver, but the trade-off is reduced HF extension, so for some (many?) folks it's not an acceptable alternative.
Note too that adding gasketed joints via adapters to it shouldn't yield as smooth/extended a response with the same polar response as the 1" throat 511 if my tweaking experiments with the latter combined with scratch building a variety of horn profiles with differing throat diameters is any indication. Only one way to know for sure though.
GM
edit: Found my catalog data sheets in pdf format: http://www.altecpro.com/pdfs/vintage...ar Horns.pdf
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511
I never thought about that, I had the impression at the 511 meant 500Hz, but it make sense, if I recall the honk it was around 1.5-2kHz. It's a good thread about the subject here: http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted.html
Also the 511B or 511E is unknown to me, but when I used my 511's I noticed a reduction of the honk if I stuffed the lips of the horn, but not enough.
Regards, Miklos
I never thought about that, I had the impression at the 511 meant 500Hz, but it make sense, if I recall the honk it was around 1.5-2kHz. It's a good thread about the subject here: http://www.diyaudio.com/forums/multi-way/161627-horn-honk-wanted.html
Also the 511B or 511E is unknown to me, but when I used my 511's I noticed a reduction of the honk if I stuffed the lips of the horn, but not enough.
Regards, Miklos