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Old 28th March 2013, 01:58 AM   #11
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This all sounds a bit odd, as are the replies.

Most sources these days are stereo. If I were approaching this problem I'd wire the source up to the (stereo) amp and the amp to the 2 two-way midtop speakers.

If these are off-the-shelf speakers they will in all probability not suffer from having the bass routed to them, although if the amplifier has tone controls, you can turn the bass down.

If I then wanted to add a bass reinforcement, I'd get a mono amplifier, or a bridgeable stereo amplifier and use it to drive the bass bin. I'd make dual (opamp) buffer to connect to the source, so as not to load it and to keep the channels from mixing and then mix the channels after the buffers with an opamp mixer, pass the output of this to a low-pass filter and thence to the bass amp.
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Old 28th March 2013, 01:54 PM   #12
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Originally Posted by counter culture View Post
This all sounds a bit odd, as are the replies.

Most sources these days are stereo. If I were approaching this problem I'd wire the source up to the (stereo) amp and the amp to the 2 two-way midtop speakers.

If these are off-the-shelf speakers they will in all probability not suffer from having the bass routed to them, although if the amplifier has tone controls, you can turn the bass down.

If I then wanted to add a bass reinforcement, I'd get a mono amplifier, or a bridgeable stereo amplifier and use it to drive the bass bin. I'd make dual (opamp) buffer to connect to the source, so as not to load it and to keep the channels from mixing and then mix the channels after the buffers with an opamp mixer, pass the output of this to a low-pass filter and thence to the bass amp.
While not (see previous post) entirely disagreeing with your point, most public address (which is after all the origin of "PA") functions are stereo irrelevant; I've frequently used the channel split to balance different regions, or loudspeakers of differing directionality (longthrows on the left main output with a total mix, shortthrows on the right, with mainly vocals and acoustic instruments, no drums or electric bass/guitars). And until quite recently, music was mixed to be mono compatible; not for any hiphalutin' technical reason but because of the number of radios that were still mono. It's only recently with headphone-mixed mp3 intended titles that it hasn't seemed worth making it sound decent reduced to one channel.

And the reason for high passing the satellites is practical; with an eight-inch LF driver (say) in your two way, it's not going to produce much of the 40Hz and down signal. It won't burn out, but all the energy goes into heating its voice coil. Whereas, if you filter this signal (a remarkably large percentage of the total power) off before the amp, for the same result the amp runs cooler and so does the speaker, or you can get several dBs louder. And it's cheap and easy to do.

Most available sources (CD players, mixers, mp3 players…) are low enough impedance not to worry about buffering (unless you want to balance the inputs, which I firmly approve of). If you want an op amp mixer, and an active low pass filter, you need a power supply; why not build a couple of active high pass filters into the box at the same time.
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Old 31st March 2013, 11:25 AM   #13
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An example is an 8ohms capable amplifier that is properly specified as a 100W into 8r0 @ 1kHz with distortion <0.1% when ....
Firstly sorry about the late reply

Thanks for all the replies, @AndrerwT - i kinda understand the test load as a measurement to see how efficient a amp is at certain impedences. The technical side is a bit beyond me but i am really interested in how this works, thanks again.

As for the setup, i've bought a PV 2000 (i would greatly appreciate any advice/tips/warnings from anyone with any experience with this amp) its got an inbuilt 150hz crossover on each channel so the idea now is to run two 4ohm bass bins on one channel (amp can run 2ohm apparently) and then midtops on the other.

Im not sure about if the amp can run mono, it says stereo on the front of it. I think i'll have to see if i can find the little spanish guy called "manual".

Thanks again for all the replies, its been very helpful
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