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

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

I was looking at some speaker cables that were " bi-wired". They were one set of cable with one end having the normal - & + ends and the other being bi-wired, having the 4 ends. This would not be utilizing the advantages of what you're suggesting (as far as I'm understanding).

Correct. As I mentioned earlier, you need 4 independent connections at each end.

I am already using the 4ohm in my current setup. Does that mean it won't help the bass issue? Or will it still help because the low impedence power will be more focused on the lower frequency instead of shared with the highs? Also, will this put more stress on my amp, making it put out power from both? Anything to be concerned about?

Given the impedance characteristics of your particular speakers, changing from having both sections of the speaker driven from the 4 ohm tap to having its low frequency section driven from the 4 ohm tap and its high frequency section driven from the 8 ohm tap will alter the overall frequency balance in the direction you want.

Obviously there are no guarantees as to how much of a difference it will make, considering the other factors that are contributing, and there are no guarantees that it won't have some unpredictable sonic downsides. But it seems to me to be well worth trying.

You won't overstress the amp by doing this, or cause any other problems I can foresee. As I'm sure you realize everything should be turned off when connections are being worked with, and obviously you should make sure that any connections to adjacent terminals are not in contact with each other. Also, a tube amp should not be operated without a speaker being connected to it.

Please let me know how I can put two wires in the 0 ohm terminal. Only thing I can think of is if I take out the banana plug and twist the other wire into it and then put back the banana plug.

You can probably judge that better than I can, based on the physical dimensions that are involved. But a good approach that would appear certain to work would be to use a banana plug such as this one, which can accept up to an 8 gauge (VERY thick) wire into its rear opening, and up to a 12 gauge wire into its side opening (or perhaps vice versa; it looks like the description may have an error). (Keep in mind that the lower the gauge number, the thicker the wire).

You would want to have a wire stripper to be able to strip off the insulation cleanly, something like this.

Some of the other listings here might provide additional possibilities.

Good luck! Regards,
-- Al

Deetothevee, the link in your last post requires a Dropbox signin. It apparently needs to be done differently for the pix to be visible to the general public.

Regards,
-- Al

Glad I was able to help. One more thing to try, if you haven't already, would be running the amp in triode mode, rather than ultralinear mode (which according to the manual the amp automatically defaults to when turned on). I don't know if with your particular speakers and setup triode mode would produce results that are better, worse, or just different than ultralinear (although I'd certainly expect the results to be different), but it's something that's easy enough to try. The manual indicates that the mode can be switched via the remote control.

When you do that, keep in mind that the power capability of the amp in triode mode is just 18 watts, compared to 36 watts in ultralinear mode (although that is just a 3 db difference; not a large amount subjectively). So on material containing high volume peaks, especially in the bass region, be careful not to turn the volume control up beyond the point where distortion starts to become obvious. That would signify the onset of clipping (i.e., the point where the amp is being asked to deliver more power than it is capable of). Severely clipped waveforms, which will sound very distorted, can damage speakers.

Also, although the manual doesn't say this, IMO it would be prudent to not change between the two modes while music is playing.

Regards,
-- Al

11-10-13: Newbee
Al, FWI you can change modes on the fly without risk so A/B comparisons are easy.

Thanks, Newbee. Since the design of your amp has a lot of commonality with the design of the OP's, I'll defer to your comment.

Best regards,
-- Al

11-10-13: Deetothevee
But I do know that the changes from biwiring were immediate and impressive ....

To be sure it's clear to others who may read this, as I see it the improvement was almost certainly due mainly to the use of different amplifier taps for the low and high frequency sections of the speaker (which in turn was made possible by biwiring), not to biwiring in itself.

One thing that I toyed with before the biwiring was my itunes equalizer. It definitely reduced bloatness in the bass. I'm no expert, but it doesn't feel right to have all this effort and money in a hifi setup and only to lower frequency responses on an EQ which alters an artists intentions. As I heard "less bass" it was satisfying at first but then I realize that I've, in some cases, eliminated sounds of a piece so that it could be appropriate to my rig and environment. Is my thinking correct? Or is this what I'm essentially doing when I make tweaks to achieve my current goals? I think this gets into the philosophy of it all so would love your opinions on EQ.

Good question. Unfortunately I don't think that there is a general purpose answer, as there are many variables involved. Including differences in the quality of the equalization function, and the fact that on many and perhaps most recordings the artist's intent is already compromised by less than optimal mic'ing, mixing, overprocessing, and generally poor engineering. And there usually tends to be a tradeoff between making the (sonically) best recordings sound their best, and making average recordings sound as good as possible.

Also, IMO/IME introducing equalization into the signal path, if it is not implemented to a very high standard, can easily have downsides (such as loss of clarity and definition) that outweigh the benefits.

FWIW, my own philosophy is that in general the less processing that is introduced into the signal path the better. And if that means that mediocre recordings are reproduced "warts and all," or that acoustic anomalies in the room or system can't be addressed in a convenient and inexpensive manner, so be it. Although I have an open (and intrigued) mind with respect to some of the relatively recent developments in DSP (digital signal processing)-based room correction products, such as the DSPeaker Anti-Mode 2.0 Dual Core (around $1100), and (at vastly higher price points) the Trinnov products.

IMO.

Best regards,
-- Al