8ohm speakers on 4ohm tap
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Renslipevol
Active Member
From what I know, you can overdrive your outputs. 8 Ohm is twice the load of 4 ohm speakers. I have hooked them up before, you just have to be very careful of your volume. Easy listening level only. I wouldn't crank it to listen to some pounding rock tunes.
Elliot Thompson
Well-Known Member
Based on my experience, nothing.
The most will happen is having a more sterile sound. Now if you try to operate two 4-ohm speakers on a 4-ohm tap there will be some overheating issues.
Best Regards,
The most will happen is having a more sterile sound. Now if you try to operate two 4-ohm speakers on a 4-ohm tap there will be some overheating issues.
Best Regards,
If you put an 8 ohm load on the 4 ohm tap, you will have double the intended load resistance on the output tubes. If they were designed to run with an 8K load, they would get 16K.
Running a higher effective load than designed typically results in decreased maximum output power and decreased distortion. It will also affect the perceived gain of the amplifier, making it quieter for the same position of the volume knob.
I would not expect it to damage either the amp or the speakers.
Running a higher effective load than designed typically results in decreased maximum output power and decreased distortion. It will also affect the perceived gain of the amplifier, making it quieter for the same position of the volume knob.
I would not expect it to damage either the amp or the speakers.
kvflyer
Super Member
I think that 4 ohms is actually double the load. What will happen is that you just are not transferring the power from the amplifier to the speakers as efficiently as you can. But it is no big deal. As mentioned, your volume may be reduced. But it certainly won't be a show stopper.
Where you get into problems is when you connect a lower impedance to the output. That will "load" it down. For instance, connecting 2 ohm speakers to a 16 ohm output is not a good thing to do...
mhardy6647
Lunatic Member
100% mismatch in impedance is no cause for concern. The frequency response may be a bit tilted (although you might like it better than the 'right' tap).
Elliot Thompson
Well-Known Member
Bear in mind that the lowest denominator output tap signifies the minimum load the amplifier can handle.
For tube amplifiers offering 4-ohm taps you can use any of the following:
One 8-ohm Speaker connected on a 4-ohm tap
Two 8-ohm Speakers connected in parallel on a 4-ohm tap = 4 ohms
Four 16-ohm Speakers connected parallel on a 4-ohm tap = 4 ohms
Four 8-ohm Speakers connected series/parallel on a 4-ohm tap = 4 ohms
Eight 16-ohm Speakers connected series/parallel on a 4-ohm tap = 4 ohms
One 4-ohm Speaker connected on a 4-ohm tap
Best Regards,
For tube amplifiers offering 4-ohm taps you can use any of the following:
One 8-ohm Speaker connected on a 4-ohm tap
Two 8-ohm Speakers connected in parallel on a 4-ohm tap = 4 ohms
Four 16-ohm Speakers connected parallel on a 4-ohm tap = 4 ohms
Four 8-ohm Speakers connected series/parallel on a 4-ohm tap = 4 ohms
Eight 16-ohm Speakers connected series/parallel on a 4-ohm tap = 4 ohms
One 4-ohm Speaker connected on a 4-ohm tap
Best Regards,
As has already been implied and stated outright, no harm will come to your amp or speakers if you connect 8 ohm loads to the 4 ohm taps. Although you don't obtain max power you do get usually get higher damping factor due to generally lower source impedance. Some speakers may sound better in this situation, others may not esp low freqs. Too, due to the way most tapped OPTs are wound and how global feedback (if used) is taken from the OPT secondaries, highest frequencies may also be affected in an unpredictable manner.
Bottom line from my perspective: Try it, you might like it.
Bottom line from my perspective: Try it, you might like it.
I have been playing with the 4 ohm to 8 ohm option on my Primaluna running the Soliloquy 6.5 speakers. The 6.5s are rated as 8 ohm speakers. With the posts bridged they measure 5.6 ohms DC.
Subjective listening comparison with PS Audio Xstream bi-wire speaker cable.
At the 8 ohm attachment the high and low frequencies are extended and tighter. Sound stage is crisp, high frequencies are a little forward, mid range much further back, and bass in the middle. High frequencies on the edge of being harsh perhaps a little fatiguing.
At the 4 ohm attachment high frequencies are down a few db and mid range is very dominating. Low frequencies may be less extended but mostly a bit looser. Overall sound is not as tight, perhaps not as technically accurate, but is very easy to listen to for long periods of time. The mid range sound stage is very enjoyable and way forward of the high and low frequencies.
Somewhere in the middle of these two comparisons would probably be ideal for my expectations. Further tuning with tubes and cables would probably make either the 4 ohm or the 8 ohm closer to this ideal sound as compared to the setup I have now.
Subjective listening comparison with PS Audio Xstream bi-wire speaker cable.
At the 8 ohm attachment the high and low frequencies are extended and tighter. Sound stage is crisp, high frequencies are a little forward, mid range much further back, and bass in the middle. High frequencies on the edge of being harsh perhaps a little fatiguing.
At the 4 ohm attachment high frequencies are down a few db and mid range is very dominating. Low frequencies may be less extended but mostly a bit looser. Overall sound is not as tight, perhaps not as technically accurate, but is very easy to listen to for long periods of time. The mid range sound stage is very enjoyable and way forward of the high and low frequencies.
Somewhere in the middle of these two comparisons would probably be ideal for my expectations. Further tuning with tubes and cables would probably make either the 4 ohm or the 8 ohm closer to this ideal sound as compared to the setup I have now.
mhardy6647
Lunatic Member
Please don't confuse DC resistance with AC impedance. Impedance is a complex (mathematically speaking) parameter which is frequency-dependent and consists of resistive, capacitive, and inductive components. The "nominal" impedance of a speaker is usually measured in the 'valley' above Fs. The following link discusses T-S parameters for a speaker driver, but the concepts are fundamentally the same for a loudspeaker system.
http://sound.westhost.com/tsp.htm
THe nominal impedance of the above-illustrated driver would be measured, e.g., in the region of 100 to 200 Hz.
http://sound.westhost.com/tsp.htm
THe nominal impedance of the above-illustrated driver would be measured, e.g., in the region of 100 to 200 Hz.
Of course not and my speaker DC measurements were insignificant to the issue discussed.
mhardy6647
Lunatic Member
So why did you mention it?
Good question. As I was chasing problems with open drivers I was keeping an eye on being able to measure this between the speakers.
More significant is these measurements for the Soliloquy 6.5 from Soundstage:
