AMP BRIDGING HELP!!

Hi,

I totaly agree with John here. This is being made much more complicated than it needs to be.

The easyest and probably cheapest option is also the best.

From your description the it sounds like you have 4 W bins, each containing two, 8 ohm speakers cones. Typically these would be wired to make one 4ohm load, this is called parallel wiring.




If this is the case then each speaker cab from the amps point of view is a single speaker that is 1200W and 4ohms.

If you have 4 of these cabs the best solution is 2 amps that can output at least 1200w per channel at 4ohms.

You then run 1 speaker cab off of each channel of each amp.


This is a great set up,
1) It's easy.
2) The amps are running into there optimum load.
3) There are lots of amps that can run at this power level for reasonable money.
4) If you ever have a fault with one amp you don't lose all your bass.
5) An amp with a total output power of 2400w is easy to power from standard 13amp power socket.


I hope this helps.

Sol

cheers for the help mate, bare with em here... so from crossover low signals go off to bass amps, into BASS amp number 1 ( out to the 2 bass bins 1 on each channell?) then into the back of the 2nd amp (again 2 bins 1 on each channell?) only question i have is how to connect the 2 amps? bridging them will take a channell away meaning i will again need 4 amps unless i daisy chain 2 cabs? on the back of my amp i have an input and an outpout, bridging takes away 1 output yes? so how will i get the signal from one output from the crossovver too 2 amps powering the bins.

cheers again mate

Forget about bridging!

It's useful in specific situations (usually where you need a LOT of power into a single load and you can't afford to buy a "proper" amp to do this in stereo) only.

Most amps have the following connections on the back:

INPUT (XLR): Connect this to your crossover - this is the signal you want to amplify.
OUTPUT/LINK (XLR/JACK): This is used to send the same INPUT to another amp. Connect this to the 2nd amp's INPUT.
SPEAKER OUTPUTS (SPEAKON/BINDING POSTS): This is where you connect your speakers.

Note that the speaker outputs are NOT for connecting to another amp!!
Only connect the "line" or "signal" "output/link" to the next amp!

If your amps don't have the "link out" connector then you can use a "Y" cable. This takes one output from the crossover and splits it to two separate cables, one for each amp. These aren't ideal in terms of ultimate sound quality, but I wont confuse things by going into that at this point. The bottom line is that they will work and for most applications there will not be any noticeable issue with the sound at all.

What amps do you have at the moment? It might be easier to give advice if I know what you have to start with.

Cheers,
John

Re: Linking amps.

Most amps have a "link" or "Thru" That can be used to link from one amp to the next. If you are using good quality balanced connection you can do this loads of times without degrading the single.

See the input section the left side of this picture.



Some amps can also be put into Parallel or Mono mode, where input on channel A, drives both channels, if you amp has this switch check the manual for correct operation. (be aware that the old Crown Macrotech amps have a different sort of parallel mode).

In this case you can use one x-over output to drive both amp channels.



Another less desirable option is a Y cable, these can lead to issues, but it's good to have a couple in your cable bag, they have got me out of trouble once or twice.


A 4th option is to buy a DSP (Also known as a LMS) with lots of output channels, you can then have 4 independent output channels.

If you are currently using an analogue crossover you may consider investing in a DSP, this will be very handy if you are running a horn loaded system as it will give you delay and EQ on each channel as well as fully independent X-overs.

Just to be clear,

The "link" - "thru" option is the best.


I was talking about DSP or LMS in general.

cheers all that has helped a lot! seem to have everything but the knowlage at the moment, the knowlage will come in time tho im sure!!! peece

Bridging gives you 4X the power of the normal output.

I would not drive a load lower than 2 ohms, you are risking an amp then!

Bridging takes one channel and feeds it out of phase (180 degrees) to the second channel. The output is then taken from the two positive terminals of the outputs.

If the amp has bridging selection, and it is using 4 way Speakon connectors, then the positive outputs will be present on at least one of the connectors, so a special bridge mode Speakon cable can be made where 1+ and 2+ connect to 1- and 1+ on the other end.

I do this regularly, you get MUCH more punch this way.

Keep your speaker cables short! Cuts down on the damping factor.

jgeissin wrote: Bridging gives you 4X the power of the normal output.

No. It doesn't.
Bridge mode allows you to RECONFIGURE YOUR LOAD to better match the amplifier's specifications. It's not black magic. The amp can deliver the exact same amount of power in either mode.
Example: You have two 4 ohm loads 1000w each and an amp that can deliver 2x 1000w at 4 ohm in stereo or 1x 2000w at 8 ohm in bridge mono.
You could connect the drivers, one per channel and get 1000w each, 2000w total.
You could connect the drivers (in series) in bridge mode and get 1000w each, 2000w total.

The only difference is that in bridge you can use less cable! (and double power into double impedance = same cable loss)

Bridge mode is most popular for driving single large drivers using a small amp that's not powerful enough to handle one per channel. Example: Cheap 2x 600w (4 ohms) amp and a 1000w 8 ohm driver. You would have no hope driving that in stereo mode, but put the amp in bridge and it can supply it's full rated power at 4 ohms per channel = 1200w - plenty for the 1000w 8 ohm driver!

jgeissin wrote: I would not drive a load lower than 2 ohms, you are risking an amp then!

Again, no.
"I would not drive a load lower than THE LOWEST RATED IMPEDANCE PER CHANNEL OF THAT AMP".
Some amps can drive no lower than 4 ohms. Some no lower than 2 ohms. Some no lower than 1 ohms. etc. etc.

jgeissin wrote: Keep your speaker cables short! Cuts down on the damping factor.

Always agreed! Shortest cables possible for many reasons:

• Better damping factor
• Less cable loss
• Less trip-hazzard (H&S)
• Tidy rigging
• Less cable to clean skank off later!
• Lighter to carry

Think of amp configurations (stereo and bridge) as simply ways to arrange two separate power suppliers for your speakers.
If it makes it easier, think of the amp channels as batteries. You can use one battery to light a small lamp, or you can combine both of the batteries to get more power to drive a bigger lamp.

Hope this is of some use to someone!
John