Large format Coaxial designs

[bfish]

Sorry to interupt guys.....

Old Guy, if you have a manual for the old HP 8050A, I'd pay good for a copy or scan (no hurry). Alternatively, do you remember what mic they're calibrated for?

[Old Guy]

Hi Bfish-Mine came with a B & K measurement mic. The mic was supplied with a curve which you had to allow for in making your measurements.

I haven't seen the thing in a while. I know I didn't get rid of it.

Just trying to be honest- I get side tracked. If you don't hear from me on this, you have permission to occasionally bug me about it. Money won't be an issue. I don't have ability to scan to PDF yet, would JPG be OK?

I have about 20 projects scattered about in various phases of completion. It's a running joke here.

Convergence, your comments are a bit unwarranted. I'm trying to disagree with you and keep it pleasant.

The 515 was and still is a great speaker. But it's day in live sound was never big, and it's gone now. The 12 inch is a much better mid bass. Asking the 515 to go to 1200 hz is just too much.

A 15" cone is beaming seriously at that point. Frankly a 12" is also but not as bad. Many mid bass units are using phase plugs on 12's at that frequency.

As far as your comments on EAW, it just shows you're a bit out of touch. EAW doesn't make transducers. If Altec was still alive EAW would be one of their best customers.

EAW is number one on almost all of the riders I get. Altec isn't in that market anymore. Altec Pro is a joke. The people carrying the Altec heritage are Great Plains and Iconic. As time goes on I hope to sample the Iconic stuff and give them as much financial support as I can. An old friend and is making noises about opening a retail outlet, I'd like to quit moving gear around.


I've heard rumors the 417 is gonna be reissued. I'll be able to use those.

I still use 299's. The Ebay supply hasn't dried up, and they are easy to use in boxes that came with other drivers.

But have you ever tried to find an 18" Altec? I might be able to find a pair for my stereo with a lot of searching. But where am I gonna get 16 for a system? And another 16 for the second system? Plus something to sell customers? Not until Iconic or Great Plains markets something.

I love Altec. But the reality is I gotta use what I can. Even the best from 10 years ago is obsolete by today's standards. You can't show up with 10 year old gear and make a living at anything except local stuff. If Altec was alive they'd be building newer and better gear. And I'd be buying it.

Lastly the EV. Please read the driver list. It lists 2 different drivers. It does not use a coaxial driver like the Altec. It has 2 horns coaxially mounted.
It's been pretty much settled the Duplex technology predates Altec. Western Electric is the earliest with written proof.

http://www.audioheritage.org/html/interact/research.htm

Posted is the first page of WE's patent. It could be argued that since Altec bought WE's technology they are the heirs, but not the originator. The 604 did put the technology on the map, it wasn't successful in the market before.

[cclark65]

As much as I would love to use all Altec's for my PA, it's just not feasible. I was blowing drivers left and right. They just don't hold up to the hard and loud music that I push through them. The EAW's have held up much better than any of the Altec, even the 3165's that I have. I have 5 of them here, 1 has a voice coil that has literally blown apart the paper (under the dust cover, took me a while to figure out what was wrong with that one!) Most of them have started ripping around the surround. I must say they did sound better than the EAW's, but I need them to hold up better also. I'll always have all Altecs in my home system, and for a smaller PA that I use for vocal groups with older crowds. They love the clarity and projection since they are hard of hearing already, it makes it an enjoyable performance when they can actually understand it! With the younger crowd, hard and loud, with the older crowd, it must be crystal clear, then it won't seem so loud when it's loud enough for them to hear it.

[LICORNE]

Hi Old Guy,

My apologies for the EV large coax. You were right .It's 2 separate drivers. Not a true one point source.


..............................................

[Old Guy]

My apologies for the EV large coax. You were right .It's 2 separate drivers. Not a true one point source.

<font size="2" face="Verdana, Helvetica, sans-serif">Hey let's just agree to disagree without being disagreeable. I hope that made sense- it did to me at one point. (grin) Apology never necessary for a minor mistake.

Argue with me as much as you like. I won't take it personally. If you teach me something it's worth all the time invested.


And as much as we might have irritated each other, I'm sure we both walked away from the conversation with something.

What's a true point source though? This unit's hf diapragm is in front of the woofer. The 604 is in the rear. At normal working distance, it would seem both approximate a point source. The diaphragm's are in line. I think it becomes semantics at some point. Just an opinion.

Frankly I wouldn't buy the EV. I was only showing it a an example.

[Old Guy]

As much as I would love to use all Altec's for my PA, it's just not feasible. I was blowing drivers left and right. They just don't hold up to the hard and loud music that I push through them. The EAW's have held up much better than any of the Altec, even the 3165's that I have. I have 5 of them here, 1 has a voice coil that has literally blown apart the paper (under the dust cover, took me a while to figure out what was wrong with that one!) Most of them have started ripping around the surround. I must say they did sound better than the EAW's, but I need them to hold up better also. I'll always have all Altecs in my home system, and for a smaller PA that I use for vocal groups with older crowds. They love the clarity and projection since they are hard of hearing already, it makes it an enjoyable performance when they can actually understand it! With the younger crowd, hard and loud, with the older crowd, it must be crystal clear, then it won't seem so loud when it's loud enough for them to hear it.

<font size="2" face="Verdana, Helvetica, sans-serif">Hi Charles- you've pretty much summed up the plight of the Altec user. If I went out with all Altecs I'd physically have to hang so many the economics would get out of hand. I mean, there are honest to gosh 1200 watt RMS bass drivers out there. And yes they are efficient, and they don't sound too bad. Not as good as Altec would have done, I agree. But I can carry one instead of 3. Or maybe 6.

Take a look at the EAW kf 940 bass horn. 109 db at 1 watt. And handles gobs of power. I don't own them cause I can't afford them. But if I want pro sound contracts that's the kind of stuff I have to compete against. Can't do it with a whole bunch of 1990's boxes.


Your right about stereo. Altecs rule. And as I said, as Iconic and Great Plains develop products they'll be up to modern standards. I'm optimistic for the future.


Here's BTW some plans for a 1-12" and 2-12" coaxial mid bass. I think I'd sill reccommend the 2-12" box as discussed earlier. This site makes more sense if you click on the British flag (grin). If you need more info we'll keep talking, the usual problem is shutting me up.

http://www.speakerstore.nl/index.php?l=en&pg=11&c=13

http://www.speakerstore.nl/index.php?l=en&pg=11&c=12

[cclark65]

The horns I would use are 11x11 inches, so they aren't huge. They are about the same size as whats in the Altec Pro horn I believe, the only difference being that I dont' have coax drivers, I'll mount the HF driver in front of the 12" driver. They cross theirs over at 950, I am crossing mine about 1100 currently, but am not opposed to changing that.

Any idea what frequency would be interruped a lot by the other horn? If it's too low, then it won't work good for me because I'll be blowing out diaphragms with the levels that I push these things to!

[cclark65]

Another thing that bothers me is that they say it has a 40x60 pattern, but I can't believe that a horn that small would be able to maintain it down to 950 Hz. I think the 11x11 size horn will only maintain it down to about 1800 or so at the lowest, more like 2000 probably.

So, with a crossover that low, they lose a lot of pattern control in the lower frequencies of the HF horn. I have no idea how low the control of the bass horn will go.

[GM]

I know this doesn't pertain much to the old Altec, but can anybody tell me what effect the larger horn has when placed in the mouth of the bass horn, such as in this Altec cabinet: http://www.altecpro.com/pdfs/DE6412_SS.pdf
I was thinking about building a cabinet similar to that, and using my MRII64 horns with 299 drivers on it. I know the driver will come close to the woofer, but maybe that will help a little as if it were a phase plug?

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

It completely compromises the integrity of the basshorn's gain/BW, so at minimum this ungainly phase plug's Vb must be offset, ergo for a given gain/BW, the design flare will need to be 'faster', with the attendant longer axial length and larger mouth. Since this 'phase plug's' contour is totally 'wrong' and with no way to sim it AFAIK, about the only thing you can do is use digital EQ like Altec Pro to shape its response since you won't be able to XO it low enough in a high power app to side-step the issue.

All this assumes you use an expo flare like the DE6412. If you were to scale up the MRII64's profile it wouldn't need as much EQ, but I doubt the drivers could handle the high compression at anywhere near rated power.

Regardless, since the HF is in front, digital delay on the HF will be required to mimic a coaxial point source.

GM

[cclark65]

ugh, too many things to think about! But that's what I asked for, all the different opinions about the concept, and I thank everybody for their input!

However, as for the part about point source delay, if the back of the horn driver was about an inch above the dust cap, I am pretty sure the voice coils will be in closer alignment than with it passing through the magnet and the HF driver attached to the back of it. Like 2 or 3 inches closer. There will probably always be an alignment issue. The only way I can see to get around the problem is if the voice coil was suspended in the same gap as the woofer coil, on the same side of the gap even. If the diaphragm is attached to the back of the magnet and shoots through the vent hole, then it's close, but still about in inch or so away, probalby not much closer than having it suspended in front of the woofer with a rear loaded driver.

I am thinking more and more about the 2-12 cabinet that Old Guy sent me the link on.