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Author Topic: Pls can someone help me with my PA Amplifier  (Read 1955 times)

Ace

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Pls can someone help me with my PA Amplifier
« on: October 16, 2007, 11:44:40 am »

Hi everybody,

I'm new to this forum and i came here because there seems to be alot of experts here who could possibly answer my question.

I have a Numark Dimension 4 1.9kw PA Amp and currently im running two 8ohm Wharfedale Pro 800w speakers on it.

At the moment everything runs fine but I feel like getting a subwoofer to beef it up a bit for parties etc.

The amp has a bridge output on the back and as far as i can understand you can have two stereo speakers with a subwoofer bridged between them on the bridge connecters of the amp.

The problem is I was told this by a friend and im not sure if it ok. I've looked on sites and they explain about mono bridging and stereo bridging but they never explain with the channels being used. Only a mono bridge from a stereo amp setup is explained.

If it is possible to do this, i'm also concerned about impedence and keeping the load balanced. Ive seen a nice 2ohm sub quite cheap and wonder if that would cook due to the impedence difference or perhaps my two 8ohms would just under perform.

The amp has speakon and screw fitting and im using the speakons at  the mo. There are three speakon jacks A B & BRIDGE. On the screw jacks strangly the bridge is between the two positives.

If someone could clear this whole thing up I would greatly appreciate it.

Thanks for taking the time to read this. Wink
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Brad Weber

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Re: Pls can someone help me with my PA Amplifier
« Reply #1 on: October 16, 2007, 01:17:36 pm »

Ace wrote on Tue, 16 October 2007 11:44

Hi everybody,

I'm new to this forum and i came here because there seems to be alot of experts here who could possibly answer my question.

Probably, although the Pro AV forum may not be the best place for your question since it is not AV related.

Quote:

I have a Numark Dimension 4 1.9kw PA Amp and currently im running two 8ohm Wharfedale Pro 800w speakers on it.

I don't know if the speakers are 800W continuous, program or peak, but the amp is around 400W per channel driving them full range, nowhere near 1.9kW.

Quote:

At the moment everything runs fine but I feel like getting a subwoofer to beef it up a bit for parties etc.

A common upgrade.

Quote:

The amp has a bridge output on the back and as far as i can understand you can have two stereo speakers with a subwoofer bridged between them on the bridge connecters of the amp.

No, you can't, it's one or the other.

Quote:

The problem is I was told this by a friend and im not sure if it ok. I've looked on sites and they explain about mono bridging and stereo bridging but they never explain with the channels being used. Only a mono bridge from a stereo amp setup is explained.

That's because the amp can be stereo or bridge mono, bridging effectively turns a stereo (2 channel) amp into a more powerful mono (single channel amp).  So an amp is stereo or bridge mono, not stereo and bridged.

Quote:

If it is possible to do this, i'm also concerned about impedence and keeping the load balanced. Ive seen a nice 2ohm sub quite cheap and wonder if that would cook due to the impedence difference or perhaps my two 8ohms would just under perform.

That amp is not rated for bridge mono into a 2 Ohm load, running it that way might cook the amp.

Quote:

The amp has speakon and screw fitting and im using the speakons at  the mo. There are three speakon jacks A B & BRIDGE. On the screw jacks strangly the bridge is between the two positives.

That is not at all strange, bridge mode uses both sides of the amp to provide a greater output capability, so in bridge mode you wire between the two positives.

Quote:

If someone could clear this whole thing up I would greatly appreciate it.

I don't know if this clears it up, but there are two common ways to add a sub to a system like yours.  The simplest is to find a sub or two subs that incorporate a output for the mains.  These subwoofers incorporate circuitry to pass only the higher frequencies on to the mains, a high pass output, so you wire from the stereo amp to the sub and then from there to your Wharfedales.

The other approach is to use an active crossover in front of your amplifier which splits the frequencies going to your mains and the subs.  You wire from your mixer to the crossover and then from there to your existing amp for the mains, as well as to an additional subwoofer amp or a powered subwoofer(s).  Just be aware that you should have some idea of how to set a crossover or you could damage the speakers and/or amps.  The advantage to this approach is that it gives you more control over the system.

If you look at the bottom of Page 2 in this, http://www.wharfedalepro.com/download.aspx?file=~/upload/fil es/EVP-X_Series__Manual.pdf, it shows how you are currently running your system and these two approaches to add a subwoofer.  The graphics may be clearer than my explanation.

It may not be what you wanted to hear, but I hope this helps.
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Brad Weber
muse Audio Video

Mac Kerr

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« Reply #2 on: October 16, 2007, 03:04:09 pm »

Ace, please go to your profile and change your alias to your real full name as required by the posting rules clearly displayed at the top of the page.

Mac
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