x over question,sirs-

[sunnysdad]

i have a pair of jbl m962s with an 18,an 8 and a 2462 driver/horn(i believe this is the driver)-anyway,it has 1 crossover for the entire box-in other words,1 power amp runs the sub,the mid and the horn-i want to put another cross over in the back of the box where i can run 1 amp for the sub and 1 amp for the mid/high(bi amp)-OR 1 power amp each for the sub,mid,horn(tri amp)
what is the proper passive x-over i can use?an N7000?
or should i just wire the sub and mid/high seperatley using a neutrik and run it through a active xover?

thanks to all

[blackwell]

Your second option is the winner.
Pull the sub off the passive crossover and drive it from a seperate amp with active crossover. The only issue will be that the mid will still be high passed so you would want to get rid of the HP portion of that crossover. I would do a freq. resp. sweep of the mid first then go and short out the largest cap you can find in the passive crossover. Then resweep. It's better if you trace out the crossover and be sure of the circuit change that you are doing. The other effect that you will see is that the passive mid crossover didn't really look like a high pass and a low pass, it looked more like a bandpass so when you cancel out the HP it may lower the mid band portion of the response.
Anyway, it's shouting in the dark a bit if you don't have the schematic but it's still fun. Maybe someone on this site has the schematic for this crossover. Then we can simulate the effect of loosing the HP part of the Mid's crossover.

Eric

[Zilch]

I don't find a JBL M962. :dont-know

[sunnysdad]

you are right-it is a MR 935

sorry!

[sunnysdad]

yes,an active x over would be fun HOWEVER .however,there is only one(1) quarter inch jack running the entire cabinet-
let the fun begin!
what i would like is an passive x over,from jbl that i could just plug into with two seperate power amps that runs the subs and mid/high
so so simple,yet so far away................
is there such an animal from jbl out there?

[Zilch]

http://www.jblproservice.com/pdf/MR9...ries/MR935.pdf

Two 1/4" plus a Neurtik, no?

[blackwell]

http://www.jblproservice.com/pdf/MR9...ries/MR935.pdf

Two 1/4" plus a Neurtik, no?

-------

Yes, this looks good to me. Just remove both C5 caps, cut the lower 1/4" jack trace leading from it's tip connection and jump it over to the woofer connection. This isolates the lower jack from the mid and hf and just connects it to the woofer. The protection circuit of the woofer will be disabled though but this will increase your damping factor and you just have to use your ear and common sense to protect the woofer. I would then short one of the C2 caps to remove the high pass nature of the mid range crossover and probably I would short B1 removing the protection, again common sense. Remember, that once you do this the mid range unit will lose a little of it's peakyness, but this is probably fine, the mids just won't be as tubby sounding.

If you like playing around with this stuff it's well worth the experience just don't forget that you must use common sense when running without protection. JBL drivers are the toughest out there but even they have their limits.

Eric

[Baron030]

Hi Sunnysdad
Here are my own thoughts on bi-amplify some MR935s.
1. Electronic Crossover Network:
You will need an electronic crossover network and I would suggest the Ashly xr-2001 or xr-1001. The
Ashly xr-2001 is a stereo 3 way, while the Ashly xr-1001 is a stereo 2 ways.
The reason why I am even suggesting the xr-2001 is that it would allow you to add some sub-woofers at
later date or it could be configured as a high pass filter preventing the 2032H drivers from being
damaged by excessive low frequency cone excursion.
2. Amplifier Selection:
Lets first look at the power ratings of each of the drivers, 2032H = 300 watts, M209-8 = 150 watts, and
the 2418H = 100 watts. Since, the 2032H driver has a 300watt rating, consider an LF amplifier in the 300
to 500 watt per channel range. After considering that the HF amplifier will be powering two drivers,
then I would suggest something with about 200 watt per channel would be about right.
3. Electronic Crossover Setup:
If you’re using a 2 way network then set the crossover point at 600Hz.
But, if you decide to go with a 3-way network then try 40Hz and 600Hz.
Actually, it would be best to determine at what frequency that the enclosure is tuned at and then adjust
the lower crossover point to be just a few Hertz lower then the port tuning. This would provide the best
protection for the 2032H drivers.
4. Modifying the MR935s:
You should not be too quick in hacking up the existing crossover network.
There is a possibly that you might decide on selling these at some later date and it would be nice to be
able to return these back to their original condition. So, one option would be building your own passive
crossovers to replace the originals or it might be possible to modify the originals in some reversible
way. In either case, here is a modified schematic, for converting the MR935s to a Bi-amp setup.
I know you asked about the possibly of a tri-amp setup. Personally, I think having a separate amplifier
for the 2418H drivers is not going to buy you a lot. But, add some 2242H subs and then using the 2032Hs
as mid-bass drivers in a tri-amp setup would be mighty sweet.

Well, thats my 2 cents.

Baron030