New bass rig! have a question about the power amp!

C

calmlikeabom

New member
k i just picked up my new rig

Peavey 410TVX™ 4 OHM
Peavey 115BVX™ BW 4 OHM
SKB 6 Space Rack
Behringer Bass-Vamp Pro Rack mount
Behringer fcb1010 Midi foot controller
QSC RMX 1450


Now my question is, do i run the power amp in bridged mono? or parralell?


thanks!

John DAvid
 
John,
I would run each cab from each channel of the QSC. That way you have control over the volume going to each cab which you may want to vary for different venues or even different songs.

That's quite a loud rig you've got. My 240 Watt Hartke rig has never been above 4 on the volume and that was playing on a 1000+ square foot stage.

Pete.
 
Match the impedence of the cab. In bridged mono, it's 8 ohms. Use an 8 ohm cab. There are 4 ohm cabs, but they're usually used for acoustics. Yes, as noted above, you've got enough power to drive 8 ohm cabs with a 4 ohm amp, but why? I would bridge to 8 ohms mono.-Richie
 
If your cabs are 4 ohms, then run in parallell. Whatever it takes to match the output and input impedence. If the cab wants 4 ohms, give it 4 ohms.-Richie
 
John,
Your power amp will work in two ways

1) Bridged - the two channels of the power amp working together as one channel to provide the total power into a single load. This usually means that only one of the two volume controls on the amp will work and only one speaker connection will work. For the QSC RMX 1450 in bridged mode it can deliver 900 Watts into 8 Ohms or 1400 Watts into 4 Ohms.

2) Stereo (two channel) - the two channels of the amp function independently with separate inputs, outputs and volume control. For the QSC RMX 1450 it can deliver 450 Watts per channel into 4 Ohms in this configuration.

The Parallel setting on your QSC relates to the inputs. I assume that this would enable a single input to be fed to both channels. If you are only using a single output from your V-Amp then the amp should be set to Parallel inputs so that the signal goes to both channels of the QSC from a single input.

Considering that both your cabs are 4 Ohm there are two ways that they could be connected together to provide a single load to work with your QSC in bridged mode.

1) Series - this would result in a total impedance of 8 Ohms
2) Parallel - this would result in a total impedance of 2 Ohms

The usual way in which speaker link outputs are wired is parallel. If this is how the ones on your Peaveys are wired then they cannot be used in this way with your QSC amp because the amp is not designed to connect to a load of only 2 Ohms when in bridged mode.

You should use the amp in stereo (two channel) mode. Each channel is then connected to a 4 Ohm load. This is within the spec of the amp.

Pete.
 
Thanks, Pete, for a superior explanation. I expect there's enough power there to blow up a cab or two in either configuration if you crank that baby, or your ears, for that matter.-Richie
 
k right now it is wired as so


Fender Jazz into Vamp guitar in. XLR out to cahn one and two of the QSC, i got the Spekon to 1/4 inch cables and connected the 4x10 to one chan and the 1x15 to the other. right now it is running in parrelel? what do you mean connected in series? also, should i be using the unbalanced outs instead of the XLR?


thanks for your help!
 
According to the Bass V-Amp Pro user manual (page 7 section 2.2 point 21) you should connect the unbalanced analog line outputs (1/4" TS jack) to your power amp because the signal presented at these outputs has not been processed by any cabinet simulation. Use 1/4" TS jack to 1/4" TS jack cables which are only as long as they need to be and of high quality to connect from the analog line outputs of the V-Amp to the unbalanced 1/4" inputs (CH1 & CH2) of the QSC.

The XLR outputs (stereo) on the Bass V-Amp Pro provide a balanced line output (with ground lift) with cabinet simulation (assuming the patch you are using has cabinet simulation). When playing live these could be connected to the PA mixing desk to feed your bass sound to the monitors and front of house speakers. For this purpose the patches should have appropriate cabinet simulations selected.

You are correct in connecting each of the speaker outputs of the QSC to each of your cabs. Use cables that are only as long as they need to be. Using cable with a 16AWG or greater conductor size is recommended for speaker cables.

The mode settings on the QSC inputs should be for stereo not parallel (switches 4 & 5) and bridge mode (switches 6 & 7) should be off. See the stereo mode diagram on the right hand side at the back of the amp for confirmation of this.

I am slightly concerned that none of this was explained to you by the person/shop you bought your rig from, although I accept that there may be a valid explanation for why not. I have no experience of the equipment you are using. All I've done is surf the web and read the manuals. I hope the info helps you.

Pete.
 
As far as blowing up the cabs goes the specs are :

QSC delivers 450 Watts per channel into 4 Ohms
Peavey 410TVX can handle 350 Watts RMS continuous, 700 Watts program
Peavey 115BVX can handle 400 Watts RMS continuous, 800 Watts program

Running the QSC flat out with pink noise could probably kill the speakers, but playing through them would probably be due to the transient nature of bass notes. However, I would not advise ever having this rig turned up to more than half volume because of the potential damage it could do to the unprotected ears of those nearby. Exposure to sounds in excess of 100dB for more than about an hour and a quarter a week could result in permanent hearing damage. A 900 Watt bass rig is really a bit OTT.

Pete.
 
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