JEL OB page update

Altec Open Baffles, etc.

JEL OB page update

Postby setup1 » Mon Jan 24, 2005 3:44 am

Joel has requested I upload a few more pictures to avoid any confusion in building the OB.

Image

This is a scan of my xerox copy of the original plan published in Stereo Sound Tube Kingdom which might be out of print.

Image

Image

For larger pics, click here:
http://members.myactv.net/~je2a3/open.htm

Regards,

JE
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Postby ichabod » Mon Jan 24, 2005 8:19 am

Looking at the baffles drawing here, I noticed that the ones made for my altec 403s have the 8" x 6" flaps a little lower by about 2 inches. Now I'm being a little picky here, but will that make a difference in dBs?

Thanks and best, james
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Postby setup1 » Mon Jan 24, 2005 9:52 am

ichabod wrote:Looking at the baffles drawing here, I noticed that the ones made for my altec 403s have the 8" x 6" flaps a little lower by about 2 inches. Now I'm being a little picky here, but will that make a difference in dBs? Thanks and best, james


I don't think it makes that much of a difference because the OB I have in my hideout system also has the 6" x 8" positioned about 2" down and I don't hear a significant difference in sound over the pair I have here. You can see the picture [top] in the background at this link:
http://members.myactv.net/~je2a3/JELhideaway.htm


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Postby ichabod » Mon Jan 24, 2005 10:27 am

THanks again. Enjoyed the accompaying pictures better now since I've listened at Joel's, and having met you here in Cebu. If Pasamba has any of his cello works on cds, I'd be happy to get them as well. The cello's tone sounds very good on the OBs with the 403As. Looking at a pair of altec biflex 12 inchers. Are they any better on OBs? Thanks.
Last edited by ichabod on Tue Jan 25, 2005 7:24 am, edited 1 time in total.
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Postby setup1 » Mon Jan 24, 2005 11:52 am

ichabod wrote:THanks again. Enjoyed the accompaying pictures better now since I've listened at Joey's, and having met you here in Cebu. If Pasamba has any of his cello works on cds, I'd be happy to get them as well. The cello's tone sounds very good on the OBs with the 403As. Looking at a pair of altec biflex 12 inchers. Are they any better on OBs? Thanks.


I don't think Willie P. has any CDs at the moment. He's in Kansas and we just email from time to time but if I hear something I'll let you know.

Even if the 419A and 412 Biflexes were advertised as full range they really gel with a nice upper midrange horn [811/802, 3000 or Fostex horn]. The 419As Nilo owns came from me and I tried them in both BR [more bass] and OB [better mids]. He finally settled using them as the bass/mid in his 2-way horn set up.

If midrange is a top priority you are better off staying with 8" drivers. For perspective listen to Joel's 755C since that's as close to the best 8" sound one can get IMHO short of a 755A. What sets the 755 series apart from other vintage 8" drivers isn't really a matter of specs, it's their ability to present a 3D quality [especially in the midrange] that fools the ear to think that it's bigger and more extended than it actually is. Of course it goes without saying that all other ancilliary components in the signal chain were voiced to squeeze out the last ounce of performance out of these drivers. IIRC, the bolt pattern of a 403A is shared with the 755s. You should bring it to Joel's place. Who knows maybe that day he might also have 755As, PIM8s, or other drivers there for comparison. Yikes that'll be a gruelling session....

The best midrange performance from 10-12" FR designs are the WE/Altec 756 and 728 which unfortunately are unobtainable, still they need help above 10khz and don't go as low as the later Altec Biflexes. If you want to extend both frequency extremes and stay realistic in price, you may want to investigate vintage Electovoice 12" or 15" trx or trxbs and also Altec 601, 603 or 604. But be ready to sacrifice some of that midrange purity from a good 8" driver....as you see it's still all about compromise and finding one you can live with.

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Postby setup4 » Mon Jan 24, 2005 11:03 pm

hi joseph!

don't forget the RCA LC1A's. for me the LC1A's midrange is very close with that of the 755A's. i wonder how this will sound in an OB. maybe joel can try this one too.
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Postby setup1 » Mon Jan 24, 2005 11:59 pm

setup4 wrote:hi joseph!
don't forget the RCA LC1A's. for me the LC1A's midrange is very close with that of the 755A's. i wonder how this will sound in an OB. maybe joel can try this one too.


Nonong is right, the RCA LC1 and LC1A were the monitor speakers used to produce the famous "shaded dog" recordings. The reason I forgot about this is because they are even harder to find compared to all the drivers mentioned above. Production was comparatively low since these were never used in theater installations or PA. Most of them ended up in RCA studios, executive suites or custom installed in luxury homes. They are also more fragile compared to Altec and replacement cones, voice coils and other parts no longer exist. Sonically they are in the same league as the WE/Altec 755, 756 and 728 but I think the best way to get ultimate performance from this driver is not in an OB but in those ~ 6 cf furnace style BR cabinets.

Thanks for reminding me!

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Postby setup2 » Tue Jan 25, 2005 12:21 am

setup4 wrote:hi joseph!

don't forget the RCA LC1A's. for me the LC1A's midrange is very close with that of the 755A's. i wonder how this will sound in an OB. maybe joel can try this one too.


How I wish those LC1As are just 8" speakers... I remember trying out the Altec 604B 15" duplex speakers on OBs... Mounting them alone will break your back... :( I think the LC1As are just as heavy...

But it would be nice to try them out on OBs... as long as you help me in mounting them on OBs...

Regards,
Joel
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Postby ichabod » Tue Jan 25, 2005 7:22 am

Thanks for the list of drivers and their possibilities. I'm spoiled over what I'm hearing now from these altec 403As. The midrange rivals the LS 3/5a, only that it gets clearer and bigger even. Truth to tell, I'm getting the same hearing impression on the 403As regarding its ability to give a layered sound into the treble region that's like the LS. So I'll content myself with these until I get some reference, better, I expect from the 755s.

What a delight it is to be SETUP like this!
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