Altec 421-8H Series II

[stratsrus]

I am building a PA System for a rock band. I have four Altec 421-8H series II LF drivers for the mains. I wish to take The design of the Electrovoice TL-606 cabinet and tweak them for a 421-8H Series II driver based on Thiele Small Parameters published on this site. Does anyone have any idea how to do this? If so, what would the new dimensions be? I would also consider a design similar to the Yamaha SW115V, tweaked for T/S parameters. Any Speaker plans for this driver would be appreciated.

[bfish]

I don't know of any Altec plans for cabs specifically for 421-8HIIs, though they were used for this app in A7 cabs. For a more-portable alternative, there are plans for the 1233, which used a 421-8LF at;

http://www.lansingheritage.org/images/altec/plans/1970's-lf-plans/enclosures15.jpg

A little creative port tuning should allow your 421s to work well in the 1233. I think you may find the need to include a HF component for mains apps, as the 421 is supposed to be more of a bass driver than full range. A modified 1233 design, using 2 421s and a single HF unit might work for you and be simple to construct.

I'm not familiar with the other cabs you mentioned, but be patient, there are others here that can help more than I.

[stratsrus]

Thanks for the speedy response. I plan on using two sets of 288-16Gs with 511E horns for the HF. I am looking to build efficient LF cabs. The horns will be in seperate cabs on top. The creative tuning you mentioned is what I am interested in learning about. I have been able to find two kinds of information on the topic: too general and way over my head. So I am looking for a practical set of plans to build the enclosures for this specific Speaker to be used in a p.a. system that will have Instruments and vocals passed through them. Thanks again for the help.

[bfish]

While trickier to build, you might get the best results from a pair of 817 cabs with your 288/511 units on top, and get better XO phase response with the physically aligned drivers. I think 421-8Hs have been used in unmodified 817s quite a bit with good results for PA. Likely the best match for the horns you're using. Plans at;

http://www.lansingheritage.org/images/altec/plans/1970's-lf-plans/enclosures10.jpg

[Old Guy]

Bfish is right that cab does work well for the 421. I've seen- and I'm not exaggerating- tons of them.

I'm really impressed though- 4 288 G's and 4 511 E's!!!

That's about $3000-3500 worth of stuff on Ebay.

I'd almost consider selling the 288's and buying 299's. The difference would finance a good chunk of the PA.

Then again, if I had 288 G's I doubt I'd be able to let go of them.

[Old Guy]

I need to make sure I've got the right cabinet- is the 606 the one with the small cover in front that can be used to block part of the port?

If it is, I successfully ran 421-8h's in those way back when. I would recommend leaving the port cover on to make the port smaller.

The suggestion of adding a hf unit is a good one, I'd even consider it necessary. For live PA I like the larger format drivers better, the best pick is the 299.

If you are really on a budget, there's only one cheap driver I recommend for live work. A little off topic here, but look at the BMS (I think 4550) one inch driver. Around $115 new. Works quite well actually on an Altec 511. I'd suggest damping the 511, do a search here some of the guys have gotten really good at getting the ring out.

Two of either cab and a horn would make a nice small PA stack. Clean and pretty loud, that's what it's all about.

[bfish]

Here's an old thread with pics of a fellow member's DIY 817s;

http://www.hostboard.com/cgi-bin/ult...c&f=3729&t=928

Then again, if you have to help roadie, you might like 4- 816s better than 2-817s.....
easier to move and more versatile.

[stratsrus]

I already have the 511E's and 288-16G's. They will be bi-Amped. I have an Electrovoice XEQ-2 which is the same as an Altec 1641A, I have a crown XS-500 and a Yamaha CP2000 for the LF drivers. I built one set 816-A's which came out great. They are a little awkward to handle my self. I was told that the TL-606 was a more efficient design and obviously they are more portable. 30 years ago I used to move four 816's loaded with 421-8h series II's by myself, plus an Ampeg SVT top complete with 8x10 Botttom and a rack of amps including an Altec 9440A. Now days, I need a nap just thinking about it. I want a more compact set up, but I still want the same Altec quality sound and the power. By the way all my friends thought I was nuts rebuilding my PA from 1977, right up until they heard it. Nothing beats the sound of an Altec PA. My friends all agree that it sounds better than anything they have heard.
I think I will try the TL-606 design, should I change the dimensions? After all the 421's are 16" as opposed to 15".

[Old Guy]

The info you got regarding the TL 606 being more effcient isn't correct. As far as sheer output, a small bass reflex box can't compare to the extra db's added by horn loading.

The question is, do you need those db's? Amplifier power is cheaper than it ever has been.
And you can up the power handling a bit with subsonic filtering- probably 40-50 hz or so. Remember this is a live PA not a stereo. A limiter will make the system sound better and help protect the speakers. Be careful of course about driving the system so hard the limiter is always engaging. You can put out a very high average power doing that.

The TL 606 is probably a flatter box however. And there's no question about it being easier to move.

The Altec is actually a 15" speaker. It has a 16" outside frame, but it's a big frame. I wouldn't worry about changing dimensions other than the cutout to match the Altec. As I said before, would recommend leaving the port cover on.

My 2 cents again. Your mileage may vary, and all that.

[bfish]

Big 10-4, efficiency isn't compact!

LOL! "need a nap just to think about it". That hits too close to home for comfort!