Newbie A7 questions

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10-02-2006, 06:32 PM
Horniac

Newbie A7 questions

Greetings all,

I'm a bit of a greenhorn:o: when it comes to this stuff and I have a couple of questions. If these have been answered elsewhere please direct me to those posts.

I heard a friend's Altec A7's a few years ago and thought "I gotta get me some of that!" I live in New Zealand and it's taken a looong time to find the parts but finally I have (from three different sources),

Some beat up A7 cabinets
511 horns with 808 8A drivers
Altec 416 8C 15" woofers

OK here's the questions,

1. The guy who sold me the 808 8A drivers used them in a PA rig and said he would put in different diaphrams as they wouldn't be suitable for home use. How can I tell the difference between a PA and a "studio" diaphram?

2. I don't have an Altec crossover. These should crossover at 500hz right? Does anyone have a schematic for a 500hz crossover? Are the ones on the internet calculators ok? Or should I try and source an Altec one?

3. I tried the cabinets with some old RCA 15" drivers and a homemade crossover but there wasn't much bass. I'm hoping that the 416 drivers will give me more (I haven't recieved them yet) but if I want to add the RCA's as subwoofers how do I do it? Do I need a three way crossover? Do I somehow make them active? (Active crossover?).

4. Similarly if I wanted to add a supertweeter some time - how do I do that?

I know some of you have moved on from A7's because "they ain't too subtle!" But you've gotta start somewhere right?

Thanks in advance for your time.
10-02-2006, 07:01 PM
Storm

Moved on?

I have a pair of 846 U speakers and they are my first and only speakers. I have heard other high end speakers and the JBL L100 and I would never "move on". Once you get yours up and running, you will never need to move on up.

Just tame them with a good equalizer and they should be fine.

Good luck with your DIY project.

:D
10-02-2006, 07:16 PM
Horniac

When I said "moved on" I meant that some reckon A7's don't suit domestic spaces because they need a lot of room to "breathe."

I don't have a huge room but I want to build the speakers in the hope one day I'll have a bigger space that suits them...

...I'm an optimist!

Anyone on the other questions?
10-02-2006, 08:09 PM
Horniac

Quote:

Originally Posted by Storm

Good luck with your DIY project.

:D

Cheers Storm :)
10-02-2006, 08:51 PM
Mr. Widget

Quote:

Originally Posted by Storm

I have a pair of 846 U speakers and they are my first and only speakers. I have heard other high end speakers and the JBL L100 and I would never "move on". Once you get yours up and running, you will never need to move on up.

:rotfl:

Yeah sure whatever....

Quote:

Originally Posted by Horniac

I tried the cabinets with some old RCA 15" drivers and a homemade crossover but there wasn't much bass. I'm hoping that the 416 drivers will give me more (I haven't recieved them yet) but if I want to add the RCA's as subwoofers how do I do it?

Storm has all the bass, midrange inner detail, and delicate highs he needs... you may find the A-7s to your taste as well, however if you do need more deep bass, you'll need something that can keep up with the horn loaded upper bass and treble. I think something along the lines of a 2242H sub in a refrigerator sized box or an even much larger horn loaded sub should do the trick.

Using an active crossover is always a major complication, but when adding woofers/subwoofers... it tends to be the best route.

If you decide you need a proper tweeter, there are many to choose from and even more opinions. As for your Altec specific questions... I have never memorized their naming system... they have several families of diaphragms and there is no shortage of opinions on which of those sound the best either... you may want to check out Todd White's site... they are much more Altec centric and there will likely be even more useful info and additional opinions there too.

But that is just my opinion.:bouncy:

http://alteclansingunofficial.nlenet.net/index.html

Widget

BTW: Storm... please take my post as a bit tongue in cheek. I honestly do believe that the A-7 and it's derivatives do have a lot to offer. They just aren't the speaker I'd take to the desert island.
10-03-2006, 11:55 AM
spkrman57

I'll try to answer your questions.

Quote:

Originally Posted by Horniac

Greetings all,

OK here's the questions,

1. The guy who sold me the 808 8A drivers used them in a PA rig and said he would put in different diaphrams as they wouldn't be suitable for home use. How can I tell the difference between a PA and a "studio" diaphram?

For home Hi-Fi use a aluminum diaphram is best(Pascalite is hardened aluminum and I use them in my 902s and they sound great) Bill Hanuschack at Great Plains can supply your needs for diaphrams!

2. I don't have an Altec crossover. These should crossover at 500hz right? Does anyone have a schematic for a 500hz crossover? Are the ones on the internet calculators ok? Or should I try and source an Altec one?

I differ from others in this regard. I would use a 1500hz crossover(2nd order low-pass and 3rd order high-pass)

Thanks in advance for your time.

Hope this helps you out some!

Regards, Ron
10-03-2006, 12:30 PM
Don McRitchie

To answer the original questions:

1) The 808 driver used a composite diaphragm called "Symbiotic" that employed a mylar surround attached to an aluminum diaphragm. It was intended for higher power applications since the mylar surround would not fatigue and the diaphragm was a heavier gauge of aluminum to resist shattering at high excursion. The problem is that, due to mass roll-off, these diaphragms do not have the extension of their original, thinner, all aluminum counterparts. The good news is the Symbiotic diaphragm can be swapped with an all aluminum diaphragm that will turn the driver into an 802 which was used for hi-fi applications. Great Plains Audio supplies new examples of these diaphragms. Pascalite (hardened aluminum) diaphragms are another option. Many find them identical to the original aluminum ones, but others have stated that the originals still sound best.

BTW, you can tell if your 808's still have Symbiotic diaphragms by looking at them. If there is a red, plastic looking rim surrounding the diaphragm, then it is symbiotic.

2) The 500hz cross-over is the lowest recommended cross-over point for the 802/808 and 511 horn. In their last production versions, Altec moved the cross-over point up to 1200hz. I prefer the higher cross-over. I think it removes the horn coloration. The 416-8C works fine at the higher cross-over point as well. If you can, I would look for an Altec 1201 cross-over. This network also contains equalization to mitigate the peaked midrange response that was a characteristic of all previous A7's to result in a more neutral sounding loudspeaker.

3) A driver swap is not going to increase the bass response. It is just a fact of life that the A7 enclosure is not a deep bass design. The horn is too small for deep extension and the bass reflex augmentation can only do so much given the much higher efficiency of the direct radiating horn. If you want full range response, you have to use a subwoofer.

4) I believe that a supertweeter works well with the 802/511. Many have reported success in using a JBL 077/N8000 or its pro equivalents. The pro versions are quite easy to find on Ebay.
10-03-2006, 02:18 PM
Horniac

Thanks very much for the advice guys, much appreciated.

I'm pretty sure my diaphragm's are symbiotic - they are definitely surrounded by plastic but it's black not red. I'll look into replacing them.

I'll experiment with a 1200hz crossover - will have to build one from an internet calculator for now.

The subs and supertweeter will have to wait 'till the wallet is recharged!:(

Cheers.