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Built-in Amps


Standard Member
I've read about a few sub-woofers that have built-in internal amps such as the Wharfedale SW250 (250W), Wharfedale SW150 (150W) and Acoustic Energy Aego T 5.1 (200W). Most of the amps/receivers I've been looking at are 75 - 100W per channel. This is probably going to sound like a really stupid question but ........ if the sub-woofer has it's own built-in amp does that mean it's OK with a main amp that isn't anywhere near its own power output?

Some centre speakers have a power output greater than 100 without having a built-in amp. Does that mean a 100W main amp wouldn't cut it?

Etienne A

Active Member
Heh - there's no easy way to answer! I can see by your (if you don't mind me saying) confusion that you're new to this.

So just to cover a few basics: all speakers need an amplifer to generate sound. Without going into much detail, you can normally assume that speakers which are not sub-woofers need to be powered by an external amplifer, and are in-fact connected to amplified outputs on your amp.

Subwoofers on the other hand are (mostly) active - i.e. they have an internal amplifer which takes a non-amplified signal from your main amp.

So - to answer a bit more directly your queries:

Yes - it's ok that your main amp is nowhere close to the built in sub's amp. As i see it the "bare" minimun sub amp should be double (ideally more!) a single channel on your amp - so a 100wpc amp would at least require a 200w sub. Note that this is absolutely not a rule, as subs designs differ widely, and usually one is better off with 3(4) times more power than 1 ch on your amp!

A centre speaker (or any speaker) says it's 100w without having a built in amp - this means nothing - you know how tires have a speed rating? Does it mean you'll always travel at that speed ... or cannot exceed it? That's there as an indication of what amplifiation one's expected to drive the speaker with!


Standard Member
That's right, not a clue.

Would a sub-woofer with its own internal amp need to be connected to the external one via a pre-out?

Etienne A

Active Member
In most cases YES - if you're using a surround amp then it's normally connected to the .1/lfe/sub out (labels may vary on the amp).

On a stereo amp you may use a stereo pre-out if it's available. BUT most ppl using a sub for stereo will still connect the self-amplified sub to the speaker outs (in parallel). This thou' requires a sub which is able to handle a "high-level-input".

Since you mentioned a centre speaker in your message - I'm assuming we're talking about a surround system - so I would suggest you just ignore the high-level-input mentioned above (sorry about that - I might be just confusing you more!).

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