stuck on configuration

madrat01

hi i have just purchased a dbx pa drive rack and have the following configuration pa set up:

2 x 6 way stereo config

Horns = P.Audio BM-D750 2inch nomial impedance 8ohms
Frequency response 500HZ - 18KHZ
Power Handling 100watts RMs

Mid = 2 front loaded cabinets containing 2 x P.Audio P150/2226 15inch woofers in each
Resonance Frequency Fs 48.8Hz of each woofer

Sub = 2 horn loaded cabinets containing 2 x JBL 2226H 15inch woofers
30Hz - 2.KHz ersponse

High Amplifier = Deton 650 x 650watt into 4ohms
Mid Amplifier = Quest QA 3004 1100 x 1100 into 4ohms
Sub Amplifier = Quest QA 4004 1700 x 1700 into 4ohms

can you help me with the set up i need for the configuration i am running

Dra

How did you have it set before?

I'd set the x-over something like this...
Subs -
HPF 40-45hz BW18
LPF 100hz LR24

Mids -
HPF 108hz LR24
LPF 1500hz (or so) LR24 The lower you go towards 500hz the short the life of the horn.

Highs -
HPF 1500hz (or so) LR24 The lower you go towards 500hz the short the life of the horn.

Do you have the RTA mic?
Have you been to the READ ME FIRST section yet? If not, do. I t ALL applies.

DRA

madrat01

yes i do have an rta mic with the drive rack

Gadget

A couple of problems here...Lets start at the bottom...

You need to verify if the JBL's are reverse wound. I have a list somewhere that tells me but I'm too lazy to go find it.. so you get to do it manually, unless you already know the answer. Take a nine volt battery and apply the + on the battery to the + on the speaker...( TYPICAL speaker configurations would have the RED terminal as positive.. I think JBL is color blind...) perhaps at the amp end to verify cable and all. The Negative - to the - on the speaker, verify what direction the cone of the speaker moves when the battery is applied...If it goes toward the magnet It's reverse wound... never mind I found it, but now you know how to test it...JBL states \"with a positive voltage on the BLACK terminal a forward diaphragm motion will be present\" This in fact means the speaker is REVERSE wound, and if wired conventionally the subs would be traveling BACKWARDS to the woofers in the tops! DISASTROUS!!!!!!

problem 2...speaker cabinets of unknown design and frequency response...most likely proprietary (home built in this case... Were the cabs built from some \"PLAN\" or were they boxes some drivers were thrown into that \"fit the holes\"...Don't laugh you wouldn't believe the things I have found in even known commercial cabinets... The problem is exacerbated by the fact that if the cabinet isn't properly designed all sorts of sonic chaos can happen, the worst of which is that the speaker cone can over excrude damaging the voice coil, or the cone itself and generally NOT giving optimum sonic characteristics... this makes tuning difficult...

Having designed and built any number of speakers I can testify to these facts with great alacrity... Make no mistake, P Audio components are awesome, I use many myself. but their specs are well.. not very accurate...So verify the movement on those P150's as well. With 4\" voice coils and a heavy cone those were primarily designed for sub duty and make a less than optimum midrange... the BMD 750 is a fine driver but with those midranges I would cross those closer to 1000-1200 hz... with a 3\" voice coil and a 500 hz frequency lo cutoff the limiting factor is the horn design. However as DRA points out, the lower you go the less longevity the diaphragm will have. So, with that in mind, and the tradeoffs here I would try and get as low as I could and let the BMD handle the critical \"clarity\" areas...

You definately have a job ahead of you...

Gadget