3-way crossover from N501

[Jack6428-2]

Hello,

I am working my way to creating a 4-way system for my 828 cabinets using an active crossover and separate amps for each speaker but am doing it in small steps.

Current status is:

- 416A (16 ohm)
- 290 (8 ohm) on 311-90 horn
- 802 (8 ohm) on 12 inch square Mantaray horn
- Amp is Dynaco ST70

I?m using a 3-way crossover from an Altec Model 9 speaker, which works but is probably far from ideal. I think the crossover frequencies are 700 and 6K Hz.

Would like to try using an N501-8 crossover along with a capacitor to limit the highs to the 802 to start at 5K Hz. Would let the 290 roll off naturally, which was suggested in previous threads.

Would I connect both the 290 and the 802 to the high end of the 501 except put a capacitor in line with the positive feed to the 802?

Any suggestions on capacitor value and what dielectric type?

Also, due to the assorted impedances of the setup, would any other components be suggested?

I realize this is kind-of a hodge podge of a setup but would like to provide more lows to my 311-90.

Hope I'm not duplicating what may already be in previous threads.

Thanks - NG

[bfish]

Hi, NG!

There are enough threads in the archive to answer all your questions, but are scattered in bits and pieces. Since I've been working on a similar setup for quite awhile, I'll try to offer some suggestions;

If you're going to go active, just do it, and live with the 2-way passive setup while you do it. You'll spend (waste) lot's of time trying to get a 4-way passive setup working right.

If your components are mis-matched impedance-wise, you're wasting your time attempting a passive solution IMO. You can use drivers of different Zs with active, just match the respective pairs with their amp Z.

If using a horn cabinet, use your 515s. They're designed specifically for horn-loading, and are fairly worthless for non-horn-loaded apps. Yes, the 416s go lower in an A7, but if you're adding a sub, you don't need it, and the 416s can be used better in standard cabs.

Find a smaller, wider-angle horn for the 802 supertweeter. I'd suggest the small MR horn used in later duplexes, (704, etc.). They're not a direct bolt-up, you'll need to fab a plate/bracket as in the 902MR HF app. GPA sells the horns as duplex replacements. You'd be surprised how well an 802/902 works as a supertweeter with no horn at all...they're just beamy.

I've found a great deal of helpful info on active 4-ways at the Lenard audio site;

http://www.lenardaudio.com/education/07_horns.html

Good Luck!

[bfish]

Thought I'd add another hint regarding your planning stage that really helped me; Forget everything you think you know about your Altec drivers, at least as far as their use in the old standard configurations. You're going to be needing them to do new jobs, so look at it as such. When I finally quit thinking of the 515 as a woofer (thanks GM!), and started thinking of it as the Low-Mid I wanted it to be, the system changes required, like reactance-annulling the 515 in a small back-chamber, all made sense.

One of the attractions of 4-way actives for me, is the reduced BW each driver has to cover. In most cases, you can be picky about the band you assign each driver, and select only the area of flattest/highest response to use, and it's usually far above resonance to boot. As you raise the XO, and with steep filters, you releive each driver of its hardest duty, and raise the power limitations as well.

There are some cases where you can get an active 4-way system, from a 3-way XO. (WAAYYY CHEAPER!). Some 3-ways also have a low filter for a sub, effectively making them 4-ways. I HIGHLY recommend that your system planning include your XO of choice! You could esily get into an expensive, unfixable spot if you don't. Once your physical driver layout is established, you can calculate the TD capabilities needed, filter slopes, etc., and select one that meets those needs, as well as interfacing well with your amps and pre. Or, you can fork out ~$2.5K for do-it-all model.....

[Jack6428-2]

Thanks Mr. Fish for all the suggestions.

I do have the little Mantaray horns from Duplexes, which I got from GPA with the bracket too. I?ll try that. Do you think the small rectangular horn in a Model 14 (about 5 X 12) or the similar bent horn of a Model 15 is still too big?

I?ll probably switch to the basic 515B for the mid bass, but might try out the 515 no suffix with phenolic spyder too. May even stick in a 904GHP Duplex for kicks. It already has the small horn so that may be interesting.

I already have a 4-way Rane AC24 active crossover. Hope this is a good enough unit. I also have a Rane AC23.

I was thinking about using the 3-way AC23 for sub, mid bass, and 290/802. This is where I could try out putting the 290 in parallel with the 802 but limiting the freq to the 802 with a cap. I keep harping on this but was once told to let the 290 roll off naturally and don?t know how else to do it.

Thanks again for your input - NG

[bfish]

[QUOTE]Originally posted by NebraskaGuy:
"Do you think the small rectangular horn in a Model 14 (about 5 X 12) or the similar bent horn of a Model 15 is still too big?"

Depends on the XO point you select, but likely, yes, too large. Short-wavelength HFs start to 'bounce around' and do funny things when the horn size exceeds the physical WL. The #14 horn has offset dispersion you don't need with the taller cabinet, and the #15 bent horn has other compromises it needed in its' smaller cab.

"May even stick in a 904GHP Duplex for kicks. It already has the small horn so that may be interesting."

Such a configuration which puts the HF horn inside the MF horn also exposes the HF diaphragm to potentially-damaging LF levels. Do so with caution. Also see above for short WLs in big horns.

"I already have a 4-way Rane AC24 active crossover. Hope this is a good enough unit."

Me too, that's what I bought. My limited testing is good so far, but I have yet to operate it as a complete system. Far more flexibility than the '23, but lots more $.

"I was thinking about using the 3-way AC23 for sub, mid bass, and 290/802. This is where I could try out putting the 290 in parallel with the 802 but limiting the freq to the 802 with a cap. I keep harping on this but was once told to let the 290 roll off naturally and don?t know how else to do it."

Parallelling dissimilar drivers is a no-no in my book. Natural rolloff is only for either extreme, you'll never match the slope with a passive XO, IMO. Since you've got the AC24, use it.

[bfish]

For help in deciding your XO points, horn sizes, and other such things, there's a handy online wavelength (WL) calculator, courtesy of McSquared;

http://www.mcsquared.com/wavelength.htm

[Jack6428-2]

Thanks for all the help Mr. Fish.
NG

[bfish]

You're Welcome!

Give us a review when you get it all setup.

I've only a week or so's work left to finish mine, but since I just took on a rush contract job, it'll be a month or more before I can spend much time on it. I started the project over a year ago, and can't wait till I can enjoy it, instead of wishy-washy wondering (hence the suggestion to "just do it"!), and working on it. I'm also using modified 825 cabs, and have "settled" on;

bipole 2245s, 1-9440A each, bridged for 600W ea., slaved for 1200WPC
515-8GHP, 9444A/SA 200 WPC
290-8K or 299-8A/MR5124, 9444A/SA 200 WPC
902/mini MR or Heil AMT1, 9442A, 100 WPC

I've also got a big, green rack, with a pair each of 1570s, 1569s, and 1568s that I may use for the top 3 channels, when I get done with amp restoration. The SS amps needed far less work, and are now tested and ready, so they're what I'll start with.

Plans are to run near 3 octaves per driver, though I expect I'll extend the 515 as far as practical, to keep the vocal band as XO-free as possible. This may mean the 299 will be chosen over the 290. (OK, maybe 2 weeks work). Another beauty of active systems, to swap components you only need to adjust the XO, not design and build a new one.

As I mentioned in another thread, it's deliberate overkill, and all about head room. (and pest control)


I also have a new pair of the large (AMT1) ESS Heil air-motion-transformers to experiment with in place of the 902s. If anyone has any experience with them, any input would be appreciated.