AS2212 HF Network?

[johnaec]

I just picked up some JBL AS2212 cabinets for PA use, (2206H & 2246J), and while realizing they don't have a full-bore passive crossover, they do appear to have some kind of HF protection: http://www.jblproservice.com/pdf/AS%20Series/AS2212-STD.pdf

As can be seen, there are two 18uf caps in parallel, then inserted in series with the 2246J, (but 8 ohm DCR for the "J"). Can someone explain exactly what this "network" does? And when biamping with an active crossover in the 800-1Khz range, what kind of additive effects should I be aware of?

Also, if so inclined, could anyone recommend a simple passive network design for primarily crossover and matching levels between HF and LF so as to avoid biamping? I'm not so much concerned about compensating for horn directivity or roll-off, since I have graphic/parametric EQ's available.

Thanks for any info.

John

[Zilch]

Hi, John.

You've got it right, the capacitors are protection. The 36 uF in series with that 16-Ohm compression driver rolls off everything below about 300 - 500 Hz at 6 dB per octave.

It'll have no impact on active crossing over above that frequency other than to steepen the rolloff at the very low end.

For passive crossover, I'd start with 3110's if you have a pair, or 3110A's, which'll let you play with the HF boost a bit.

M552 active has built-in compensation for 80 series horns. Don't know if that applies to 2380A, though, but they cheap.

[Those be LOUD, I betcha.... ;) ]

[johnaec]

Thanks for the info, Zilch! I'll look into the crossovers you mentioned.

These are actually AS2212-64, with the 2385A 60x40 horns, but I've also picked up a pair of 2380A 90x40 horns to swap in/out. 'Some flexibility here... :)

John

[Zilch]

They'd supplement a monster sub nicely.

Consider them "Satellites." ;)

[johnaec]

They'd supplement a monster sub nicely.There's no way I could move that cabinet in your garage! :p Maybe we should have a block party at your place. :applaud:

John

[johnaec]

For passive crossover, I'd start with 3110's if you have a pair, or 3110A's, which'll let you play with the HF boost a bit.Well, I picked up a pair of 3110A's and they appear to do the job nicely. HF is still a little hot, though, (LF=95dB HF=114dB). 'Any idea on what I could put between the crossover and HF to tone it down a bit further? 'Something that won't screw up the crossover specs? Could I get away with some kind of HF L-Pad? These are just going to see PA use, (eventually with 2226H in place of the 2206H), so it doesn't need to be top-of-the-line audiophile quality components...

Those be LOUD, I betcha.... ;) 'Ya think? :blink: :shock:

BTW - I mentioned one of the HF dias. was blown but I've got the factory replacement. Thankfully, the other two dias. are fine. (Three AS2212-64's total, plus a couple 2380A horns to switch in and out with the 2385A's.)

John

[Zilch]

That'll be easy. You'll need three 16-Ohm power resistors (10 Watt or bigger) for each system.

One you put across the HF driver terminals.

The other two you put in parallel with each other, and the pair in series with one of the HF leads from the crossover (doesn't matter which). The other lead just hooks up regular to the driver and the first resistor.

That'll knock it down 6 dB, which will likely be enough.

I have a pair of those 16-Ohm L-Pads made up here for borrowin', if you're in the area.... :thmbsup:

[They made with 25 W resistors and 10 Ga Teflon wire. It'd take some consderable effort to smoke 'em.... :p ]

[johnaec]

Thanks, Zilch! 'Off to the electronics store to do a little resisting. I do think I'll run some basic RTA before and after to check out all the different curves. I'll post what I find, (though it may be a few days...).

John

[johnaec]

They made with 25 W resistors and 10 Ga Teflon wire. It'd take some consderable effort to smoke 'em.... :p I managed to pick up some 32 watt 16 ohm resistors, but they're cylindrical, (tubular), so my setup might not look as nice as yours...

John

[Zilch]

I managed to pick up some 32 watt 16 ohm resistors, but they're cylindrical, (tubular), so my setup might not look as nice as yours...Heh. If they get you the attenuation you want, we'll pretend to order the proper non-inductive type in the appropriate wattage for the application. :D

[johnaec]

Heh. If they get you the attenuation you want, we'll pretend to order the proper non-inductive type in the appropriate wattage for the application. :DOK - so I take it not all resistors are created equal? This was all the place had that were anywhere close to those values. Should I return them while I can, (no solder yet)? They were $1.50 each, but if I don't want to use them...

John

[Zilch]

Those'll be fine, John.

It's for PA use, right?

Not gonna matter....