Pioneer VSX 520 - safe to use 4 ohm impedance in 3.1 configuration?


Active Member
I've been running a set of Eclipse TD508 ii single driver speakers with an active subwoofer in a 2.1 configuration, with good results for both music/movie playback.

Recently found a good deal on a used AV receiver so decided upgrade and add a centre channel (rears are out of the question due to room lay out). I have a pair of smaller TD307 ii speakers so have used one of them as the center channel. They aren't much smaller than the TD508s but I am not liking what I hear so far...

Sound is boxy and it's odd hearing majority of film's soundtrack coming through a single centrally located speaker rather than a the "phantom" center channel normally generated by the L/Rs in a stereo down mix. In this setup, the 510s aren't doing the heavy lifting and are more for background use / action sequences.

Before I switch back to 2.1, I'd like the try adding the second 307 as centre channel also. My thinking is, most dedicated centre speakers are 2 mids anyway, so maybe it will add some fullness to the sound?

My predicament is, do I choose serial or parallel? The amplifier specs state 6-16ohm only.

TD307 Specs are:

bass reflex design
100Hz-25kHz (+/-10dB)
80dB sensitivity
8ohms impedance

They are small drivers and produce next to no bass output, so hardly a taxing load. Maybe I can get away with a 4 ohm load in this instance?


Distinguished Member
Not recommended

Resistance varies on frequency.. Nothing to do with how low or how much bass speakers play.

Have you tried setting the centre to 'small' and setting the sub crossover higher.

Having two of the same speakers won't add a fuller sound or more bass.

100hz at whopping - 10db gives you an idea there is hard any mid bass. If you have the subwoofer crossover set at somewhere 80 to 120hz then there is a big dip at the crossover point as the 307 doesn't play very low.
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