BillFitzmaurice.info

Hello all,

I have begun serious preparations for building some T48's. I had some questions about selecting optimal drivers, though. I think Seth mentioned that the PRV 15SW2000 are the new best. Looking through old threads, though, it seems the 3015LF may be best if I decide to do as wide as possible?

I’m also wondering how well they will match with the tops I have - 2 JBL MS115. They run 70-14khz (-3) and I quite like their sound - I plan on keeping them for the time being. I know with FLH having a rising efficiency that they could easily cover to 150Hz.

Is it recommended to match the sub to the top and have it cross over ~70Hz, or does it make more sense to have the sub operate over its full range?

In regards to how high up to run the subs, it is recommended to be below 120hz, or lower, since above that region one will be able to locate where the sub is. In your instance, you could run your tops down to 80-85hz, and have the subs run up somewhere near that point. Where that point is will be up to your ear.

Optimal crossover freq for the subwoofer hand-off is more often than not, situationally dependent. Measurement is highly recommended. Could be as basic as any flavor of SPL meter, a voltmeter, notepad, and pen...all the way up to a formal Smaart rig.

I see.

Are there specific phenomena you're trying to avoid or instigate by playing with the hand-off point, or is it as simple as what "sounds best"?

As in, are there specific principles and parameters in the literature I should familiarize myself with, or is it a trial and error; learn as I go primarily.

Obviously this whole hobby is about what "sounds best" but I like to read too

Have you read this? viewtopic.php?t=398

Part and parcel of proper sub placement is that they not be directionally locatable. That means crossing at 120Hz or lower, but no lower than necessary, to take the low frequency load off the mains. BTW, your JBLs are down 3dB at 70 Hz in half-space, but that means on the floor. Up where they need to be they're in full space, so you may need to go considerable higher than 70 Hz to preserve adequate excursion headroom.

Specific phenomena to avoid would be the all-to-common situation where the subs are taking a giant crap all over bottom octave of the mains. Once you discover what that sounds like, you'll hear it everywhere. Which is typically from choosing the wrong filter set points, choosing the wrong filter slopes for the application, setting things up by ear....or any combination thereof.

Yes, it is trial and error until you figure things out...early papers on crossovers by Thiel, Klipsch, and Mitchell helped me quite a bit. Keep your eyes peeled for jargon like "filter impulse response" and "pass band". Pertinent parameters are the usual suspects: Volts, dB SPL, and frequency.