System too bassy - Primaluna & Usher

IMO neither changing speaker cables nor biwiring would in themselves be likely to result in significant improvement, given particularly the short lengths of your speaker cables (most relevant cable parameters and most cable effects are proportional to length), and given that cabling is clearly not among the major root causes of the problem. Nevertheless, I strongly urge you try biwiring, but in a certain way. Let me explain.

What I suggest that you try is as follows:

1)Remove the jumpers on the rear of the speakers that connect the terminals of the high frequency driver to the terminals of the low frequency driver.

2)Connect the "0 ohm" output terminal of the amp (which is referred to on many other amps as either the common, -, negative, or black terminal) to the - terminal of the speaker's low frequency driver, for the corresponding channel.

3)Using the other wire in that 2-wire speaker cable pair, connect the 4 ohm output terminal of the amp to the + terminal of the speaker's low frequency driver.

4)Using another 2-wire speaker cable, or the other 2-wire pair that may be included in a bi-wire cable, connect the "0 ohm" terminal of the amp to the - terminal of the speaker's high frequency driver.

5)Using the other wire in that 2-wire pair, connect the 8 ohm (not 4 ohm) output terminal of the amp to the + terminal of the speaker's high frequency driver.

In other words, you would be driving the high frequency part of the speaker from the 8 ohm tap, and the low frequency part of the speaker from the 4 ohm tap.

A major reason that the bass heaviness is evident with the Prima Luna to a much greater extent than with your former HK amp, which I presume was solid state, is the interaction of the tube-based Prima Luna's relatively high output impedance with the speaker's impedance variation as a function of frequency (see Figure 1 here), the speaker impedance being generally high in the deep bass region, and also including a very large peak in the 50 to 90 Hz area, while reaching much lower values in parts of the upper midrange and treble regions. Using the lower output impedance of the amp's 4 ohm tap for the low frequency driver, while using the 8 ohm tap for the high frequency driver, will significantly alter that interaction in the direction you seek.

Regards,
-- Al

Those Ushers are very difficult to drive and control. They may go loud easily but to control them you need a lot of current which the Prima Luna cannot provide. Look at some nice SS amplification like Symphonic Line or Naim. They are known to be very musical amps while still controlling the drivers like mad.

Almarg-- thank you. I've read your post 3 times. It got a bit clearer but I'm still confused. I'm not clear enough to try it yet. Each speaker cable has a - & + wire. When you say to connect one of the pair of wires, do you mean both - & + ends of the same "speaker wire" into said terminal? (Or even both ends (2of4) of a biwire)

Ok I think I got it. So the only terminal that will have more then one wire would be the 0 terminal at back of amp. Correct?

Ok I think I got it. So the only terminal that will have more then one wire would be the 0 terminal at back of amp. Correct?

Yes!

To be sure it's clear, let's just consider the situation where you are NOT using cables that are specifically intended for biwiring. You would have four ordinary speaker cables, two for each channel.

On each channel, one wire of one of those two cables would connect the - (0 ohm) amp terminal to the speaker's - low frequency terminal. The other wire of that same cable would connect the 4 ohm amp terminal to the speaker's + low frequency terminal.

One wire of the other of those two cables would connect the same - amp terminal to the speaker's - high frequency terminal. The other wire of that cable would connect the 8 ohm amp terminal to the speaker's + high frequency terminal.

Alternatively, the same thing could be accomplished with biwire cables, which would provide 4 wires in the cable for each channel, but ONLY if it were the kind of biwire cable that provides 4 independent connections at both ends (rather than just providing 2 connections at the amp end, as many of them do).

BE SURE to remove the jumpers on the back of the speaker that connect the low and high frequency terminals to each other, when and if you try this. I don't think any damage would occur if you failed to do this, but the sonic results would not be as intended.

Regards,
-- Al