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Author Topic: Bridging QSC MX2000a with 2 LabHorns parellel  (Read 6271 times)

Greg Koepke

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Bridging QSC MX2000a with 2 LabHorns parellel
« on: November 24, 2008, 01:35:34 pm »

I am using a QSC MX2000a in bridge mode that will support a load up to 4 Ohms and would like to run two LabHorns off this one power amp. I have ready articles on this great web site and have read that you can not just use an ohm meter to measure impedance. You have to take the loading of the speaker into the labhorn as well and am unable to obtain this.

Has anyone ran 2 labhorns per side into a bridged power amp that will support a 4 ohnm load? Since each speaker is rated at 6 ohms I believe that two labhorns ran in parellel would get to me around 1.5 ohms. But have read here that it is more like 3 to 4 ohms.

I could run a cabinet on each channel but want to avoid that. I could trying wiring a cab in series as well as someone else stated but want to avoid that as well. I could go and but a QSC PowerLight 6.0\9.0 IF I had the coin but want to avoid that.

I have been running one labhorn on the bridged QSC MX2000a without any issues. I love these cabs! Now I want to get 2 per side and would like to keep the power amp bridged. Would I be risking damaging the power amp and the speakers?

Thanks to all of you who post messages as this place is a wealth of knowledge;)
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gkoepke

Ivan Beaver

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #1 on: November 24, 2008, 07:14:45 pm »

You are asking a lot for an amp to do that.  Yes it "might" Rolling Eyes drive them, but at what quality and for how long?

Buy another amp.  I have not seen an actual impedance plot, but would consider it a 4 ohm cabinet in terms of amplifier loading.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Josh Billings

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #2 on: November 25, 2008, 03:27:37 am »

I remember driving some dual 15" tops with a qsc rmx2450 and it would shut off every 15 minutes or so...not a good idea to run something at less than 2 ohms per side.

People say the LAB acts like a 4 ohm speaker, but i've seen the impedence plots and it goes as low as 3 so in a situation where you bridge an amp to 2 of them you are essentially sending a .75 ohm load per channel on the amp...just way too much to ask for any amplifier.

That amp could probably be brided into one sub (2k watts @ 4 ohms). I've used a PLX3402 in stereo on them and it works really well.

I currently run a RMX4050HD amp and one LAB per channel. Great match if you plan to drive them on the harder side (stay out of the clip). The 5050 is a better choice if you're doing music with lots of dynamics. They are heavy but sound great on subs.

P.S. I think QSC is doing a rebate thing again...but it was a pain in the ass getting the rebate. I was a rare case though, but a lot of people have had no problems.

-Josh Billings
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Elliot Thompson

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #3 on: November 25, 2008, 05:15:02 pm »

Josh,

Greg is asking about the MX 2000a.  Very Happy


I own two QSC MX 2000a amplifiers and wouldn't recomend driving it under 4 ohms bridged mono. It is a very robust amplifier but, it isn't that robust to operate under it's minimum load for long periods.

Trying to be creative with speaker impedance ratings is more detrimental to the overall amp's performance than you might imagine.

Best Regards,
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Elliot

Ivan Beaver

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #4 on: November 26, 2008, 12:11:26 pm »

I guess he could wire the cabinet drivers in series (instead of parallel) and get around 16 ohms/cabinet.  Then the amp would be fine. Very Happy
 
But he would not have that much power available to each cabinet-but then again, he probably would not tear up drivers either.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Elliot Thompson

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #5 on: November 27, 2008, 10:59:06 pm »

The results (Output) should be the same as the 4 ohms per channel route.

QSC MX 2000a  = 1300 watts @ 8 ohms Bridged Mono.

QSC MX 2000a = 650 watts per channel @ 4 ohms, Stereo Mode.

He may even have a lower output for the drivers sensitivity drops once you wire two loudspeakers into series. It is a no win situation in my opinion.

Going from 1300 watts to 2000 only yields a 1.8 dB gain. Which is piss-poor for amplifier headroom much less expecting more volume in the bass department. But some guys must bridge their amplifiers no matter what so, who am I to argue?  Razz

Best Regards,
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Elliot

Ivan Beaver

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #6 on: November 28, 2008, 07:36:03 am »

True in regards to power.  But with 16 ohm cabinets there will be less loss across the cables-for whatever little that might be Rolling Eyes .

I prefer not to bridge amps-especially sub amps if at all possible.  The tightness is just not as good as in normal operation.  But the application may warrant it.

I had overlooked the overall output power situation, and was "focused" on his wanting to go bridged and the impedance loads.

Looking back, you are right, it is probably better just to run 1 cab/side.

I will "disagree" on the sensitivity part.  Yes, the 16 ohm cabinet will be less sensitive to a particualr input voltage, but with equal "power", the end results (SPL) would be the same as if they were wired in parallel.
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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

Ivan Beaver
dB Audio & Video Inc.
Danley Sound Labs

Greg Koepke

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Re: Bridging QSC MX2000a with 2 LabHorns parellel
« Reply #7 on: December 01, 2008, 12:24:55 am »

Thanks for the input guys!  It appears that I have too little power using a QSC MX2000a to drive to labhorns per side.  I have two MX2000a's and was going to bridge each amp and run two labhorns per side.  Each MX2000a would drive two labhorns per side.  I'll start looking for a QSC PowerLight 6.0 and believe that should do the trick.  Since I have seen the PL6.0 in action last weekend driving 3 Martin subs per side I was impressed with the sheer power that that amp can produce for subs.  If I am lucky I could score a MarcoTech 5000;)

Thanks again for the input.
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gkoepke
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