Tube amps and speaker ohms

Bartockfan, FWIW, while you are doing your research factor in a couple of more issues, or at least possibilities....

1) Its not some much whether it's 4 or 8 ohms for a well made PP tube amp, its about the impedence curve and the minimum impedence. Some tube amps do quite well down into the 2ohm area and even come with 2 ohm taps. Its much more about the design of the actual tube amp than anything else generically speaking. Its also important to understand the actual output impedence curve of the amp and its synergy on the impedence (curve of the amp).

2) Be sure that the bass below 35 hz is unimportant to you by what you actually hear in your room, not just by looking at the supposed frequency response of instruments. If for example your room has a null in the 35 - 40 hz area your going to have nothing below 35hz to reinforce the bass which even starts to resemble the deep bass you would hear in a hall. Now if you room is flatish down to 35hz and you have a node at 30 hz the Towers may be more than enuf.

Perhaps its just because I don't listen to the Sig Systems at ear bleeding levels but I have no problems with tube amps with 40 to 80 watts in my medium sized room. In my room the Super Towers would not work due to room acoustics.

FWIW.

Newbee's first point on the impedance curve of the speaker is taking you to where you really need to be. I'll add in phase angle as well.

One other parameter I think that should be discussed is the crossover topology. How simple or complex the crossover is makes a tremendous impact into whether the loudspeaker presents an easy or difficult load. Tube amps like first order crossovers better than second order crossovers, and second order crossovers better than third order crossover, and on and on. On top of that, things like Zobel networks, trap circuits, and the like can turn things completely on their head. Take some famous loudspeakers, such as Thiels, with first order crossovers that so many compensation circuits - a total bear to drive.

The best generality I can offer is that you want the crossover as simple as can be. The opinions on single driver loudspeakers being a good match with a tube amp is true - because there is no crossover to suck up the power. Of course, you do give up frequency response.

Far too often, sensitivity and nominal impedance give such an incomplete picture that you simply need to walk away from what people will tell you, and give it a try. THAT is the only way you'll know...

Well, I'm trying a brand new experiment today, and for the next couple of weeks. Trying a 30wpc Leben CS600 with my 89db/6 ohm (3.5 ohm minimum) VR4 Gen III HSE loudspeakers. Theoretically, this should not be a great match even though the Leben has a 4 ohm setting. Mid week a pair of 88.5 db/8ohm (5.5 ohm minimum) Castle Howard speakers arrive. Later in the week, a 55wpc Rogue Cronus arrives.

Yes, major system changes afoot...

Trelja,

Sure glad you can read thru my lack of editing skills. For others, last words in 1) "(curve of the amp)" should read (curve of the speakers).

Glad I don't get paid for this! :-)

Hi Pauly, here's what's up with four ohms: Yes, you can use the 4 ohm tap, but at a price. On most output transformers that have a 4 ohm tap, measuring the response of the amplifier on that tap as opposed to the other taps will reveal slightly lower power and quite a bit less bandwidth (both due to increased turns ratio and distributed capacitance in the windings). Sometimes there is also additional hysteresis loss. So tubes amps can make lower distortion on higher impedance taps as well.

So, all other things being equal, most tube amps will sound better on 8 or even 16 ohms as opposed to 4.