Scrot,

> Does anyone happen to know where the Mid and High tone nobs on JBL model 4312 are set in order to be "flat"? <

I don't know that model, but I have a pair of JBL 4430s - huge mammas with a 15-inch woofer and a horn - and flat is when both the mid and high controls are set to full up. Not when set according to the panel markings.

This assumes your JBLs are passive speakers. If they are active then my advice may or may not be correct.

--Ethan

I've used JBL drivers for years in live performances and find the compression drivers are very efficient. This is on the order of 10 to 17 dB more efficient than the bass drivers.

JBL bass drivers are also very efficient, but with a steep rolloff curve as the design trade-off for the efficiency.

Unless JBL attenutates the compression drivers, they will be significantly hotter than the bass driver. Also considering the bass driver rolloff, thinking of the JBL system as 'flat' requies a long stretch of imagination.

It would be very interesting to hang a real time analyzer in front of the JBLs. An RTA would be useful for setting the attenuator controls as close to flat as is possible.

In studio monitoring work, would it then be appropriate to EQ the bottom higher for a flat response?

BG,

> It would be very interesting to hang a real time analyzer in front of the JBLs. <

That's exactly what I did. My JBL 4430s are biamped, and I measured the room response while setting the relative level of the low and high band power amps. The flattest response, and best sound, was with the mid and high level controls on the speakers all the way up. A friend of mine has the same speakers but they're not biamped. I never analyzed his system, but his speakers also sound best with both controls all the way up.

--Ethan

The JBL's I'm referring to are passive. I do not have them bi-amped, but would like to try...how would I go about that? being they have only one jack (+ and -) would I have to access the crossover internally?

I have read somewhere in this forum a thread in which someone adressed the JBL's tone controls setting but I can't find it in any search...Im not sure if that was the same model as I have anyway. There is a vast difference in the sound obtained by using these controls and I really cant tell (without an RTA) where the heck flat could be (if at all). Your right, Ethan, they sound best all the way up, but that makes me a little bit suspicious...lol

Scrots,

> The JBL's I'm referring to are passive. <

Yes, mine are too. I have a Rane crossover and a pair of Crown power amps putting out more than a kilowatt in total. :D

> I do not have them bi-amped, but would like to try...how would I go about that? being they have only one jack (+ and -) would I have to access the crossover internally? <

In that case it's probably not worth the effort. I'm not up on all the models, and it may be that the only thing your speakers have in common with mine is the name printed on the front panel.

> they sound best all the way up, but that makes me a little bit suspicious <

Unless you plan to buy or borrow proper analysis tools, just play a variety of commercial CDs you think sound good and set the speaker controls to sound best for the most CDs.

--Ethan

[ August 25, 2003, 09:54 AM: Message edited by: Ethan Winer ]

Thanks Ethan. Makes sense.

I bi-amp also, Rane crossover, but a pair of QSC instead of crown. I like the Rane toys, for sure... have a bunch of 'em.