Standard Wizard Crossover frequencies and Martin W3/W2A rig

alaistair

Hi – hope you can help.

I recently took over PA duties at a church running a reasonably sized Martin Audio/QSC/DBX Driverack rig. And I was checking over settings and config – and I don’t think it’s well set up and I was looking for some advice on the crossover frequencies I should use in the DBX Driverack.

Details of the rig are:

Soundcraft Series Two desk feeding into DBX DriveRack PA.
Driverack PA set up in 2x6 setup (stereo triamp setup).
Driverack Low output connected to QSC PLX1804 driving 2x Martin Audio W2A Subs
Driverack Mid output connected to 2xQSC RMX2450 driving low input on 4x Martin Audio W3 (2 each side)
Driverack High output connected to 2x QSC RMX1450 driving high input on the 4x Martin Audio W3

These have been setup using the standard DBX Driverack PA “wizard� for speaker setup and “Pinking� the room (via their automated RTA mic input)

Looking through the final config….it looks like the standard crossover frequencies in the “wizard� are
Low (subs) 34-100Hz
Mid (to low of W3 speakers) 100hz – 6.5khz
High (to high of W3 speakers) 6.5khz up

However…looking at the specs of the W3
http://www.martin-audio.com/products/W3.asp
It looks like the low input on the W3s only drives the 15� driver
And the high input drives the mid/high drivers (via a passive internal 3.3khz crossover)

Reading the specs of the W3, it looks like the EXTERNAL crossover should be operating at 650hz driving the 15� separately from the mid/high?

Is this correct?

So should I change the crossover settings on the DBX Driverack to
Low (subs) 34-100Hz
Mid (to low of W3 speakers) 100hz – 650hz
High (to high of W3 speakers) 650khz up

Thanks for any help….

Alaistair

alaistair

Sorry - I should also have asked....in the Wizard, there are Flat, A,B,C,D curves. Is there any suggestion what "situation" curves A-D suit (is there a rock/disco/etc sort of mapping to these curves)

Gadget

Wow! That's MESSED UP!!if that were the case there would be a hole in the sound from probably about 2-4Khz (depending where the 15" woofer starts to fall off frequency wise) to the 6.5khz crossover point?

These things would DEFINITELY sound like crap under this scenario..

What they have done is let the woofer do whatever it can but I assume that that drivers response is going to start to fall off around 4khz...?? Maybe higher, but the crossover point for the hi outs is well into the tweeter range and the MF driver isn't doing ANYTHING!

No, the xover should be 650hz>out on the HF like you suspected...

My recommendations would be

Subs (hopefully running stereo one per side of the 1804)
HPF 45hz BW18 (this because you are SERIOUSLY underpowered with those subs @ 800 watts per cab)
LPF 100hz LR24
tops
15" (LF input)
HPF 100hz LR24
MF/HF input
HPF 650hz LR24

LR 24 chosen for it's linear xover points and near symmetric delay through the crossover)
BW 18 chosen as a steep falloff point for speaker over excrusion protection.

We have provided an extensive help section...
"Start Here"
viewtopic.php?f=61&t=959

and FAQ's
viewforum.php?f=60

So you can find information on setup and tuning, and different topics that may be of interest...

Welcome, Alaistar!
gadget



LPF 650hz LR24

Gadget

Sorry - I should also have asked....in the Wizard, there are Flat, A,B,C,D curves. Is there any suggestion what "situation" curves A-D suit (is there a rock/disco/etc sort of mapping to these curves)

Nope, not to my knowledge... but I find that the FLAT is the most useful, but you can set up a preset of each and easily toggle through them.

I "think" that "C" was actually designed as a DJ preset, and A is classical/jazz preset ... but that's about all I know.
G

alaistair

Thanks!!!! (I won't tell anyone it has been running like this for 4 years!)

It seems strange that the mid to high crossover defaults to 6.5khz it the wizard - I would feel that's quite high for most speaker setups that have subs and then probably 15" drivers in the bass-mid range???

I wont also mention that the guy originally "pinked" the room with an SM58!

I did quickly reconfig the system with these new crossover frequencies on Sunday morning - but the system sounded incredibly "toppy". But I think that was probably with the eq of all the stuff on the desk....I did a bit of a reset and it started to sound better.

I did get some complaints...but I guess its because it sounded "different"?
(hence this post to confirm I wasn't being stupid)

For the RTA - I used a Rode M3 that I have in my mic collection. I do like that mic and its very "natural" sounding. I've picked up a DBX RTA mic this week from ebay....looks a bit crappy compared to my M3...will it make a big difference? I can repink the room for this weekend in time for Sunday morning....

Gadget

Did you re set the balance once you set the crossover properly? Looks like you diss-engaged the GEQ also?

I don't trust any of the setups unless they are from JBL directly...they had a Peavey SP218/ SP2 combo crossed at 190hz? WTH?

As for the mic, the M3 looks pretty good as long as the response curve posted is ACCURATE ... and not a "best of batch" scenario...The hump @ 6k5 could easily be dealt with if known about...It will be interesting to see how different it is...but one thing is for sure, even the exact same location for the mic will yield different results.

Why? Because for one thing, you cannot equalize a room.. only a bulldozer can do that what you CAN do is equalize a speaker system with RESPECT to the room...

If you are running a center cluster that is one thing, but if your running L/R mains it's a recipe for disaster...Even with a center cluster I would only use the center most speaker on, and the mic on the floor on a towel or carpet strait out about 20-25 feet. If there are pews close by try and cover them with blankets to deaden them from reflected sound to the mic, doesn't have to be the whole place just those close...This will help eliminate reflections interfering with the Auto Eq. If there 3 speakers center clustered and the outer speakers are on a separate feed then you would want to have a separate Auto Eq for each side of the out fills as well... An off axis Auto Eq of the center speaker only would be useful as well and averaged (with listening) into the response eq...

If the speakers are L/R... boy... that's a tougher one, I'd take one down and do a Flattening pass on one speaker (see new indoor method or the other outdoor tuning methods in the FAQ section)and then see what the room is doing to the sound by maybe placing a table on the pews/chairs (assuming no floor space directly out from the speakers 20-25 feet)

In the end the ears rule, but I highly recommend flat response for the Auto Eq.