pro's and con's of a 4 ohm speaker?

Is there any benefit of using lower impedance speakers with tube amps?

Hi Kijanki,

Not as far as I am aware. As you may have seen, Atmasphere (Ralph) has commented a number of times that the sonic performance of pretty much any amplifier, tube or solid state, will be better when it is working into a higher impedance. And Audiokinesis (Duke) made essentially the same observation earlier in this thread, while rightly adding that that may very often be outweighed by performance differences between the speakers themselves.

As I understand it combined plate impedance gets divided by speaker impedance to get transformer turn ratio.

Actually, as with any transformer the impedance looking into one side of the transformer equals the impedance that is connected to the other side factored by the SQUARE of the turns ratio. For an output transformer, typically the number of turns on the secondary side for the 4 ohm tap is 0.707 times the number of turns for the 8 ohm tap. That results in the output impedance of the 4 ohm tap being half of what it is on the 8 ohm tap, as you indicated, as well as resulting in a maximum power rating that is approximately the same when a 4 ohm speaker is connected to the 4 ohm tap compared to when an 8 ohm speaker is connected to the 8 ohm tap. As well as resulting in the output tubes seeing approximately the same load in both cases.

Best regards,
-- Al

Al, I always forget about tube amps since the last one I had was EL34 100W guitar amp I built about 40 years ago.

As I understand it combined plate impedance gets divided by speaker impedance to get transformer turn ratio. If plate impedance is 1k then transformer ratio for 4 ohm speaker will be 250. There might be negative feedback involved but it will lower impedance in the same ratio thus 4 ohm tab impedance will be always half of 8 ohm tab impedance.

Is there any benefit of using lower impedance speakers with tube amps? I remember 16 ohm speakers and heard of 32 ohm designs. Didn't low impedance in speakers come with SS amps?

8 ohm speaker will also double your damping factor

Although that will not be true in the case of a tube amp, assuming the 8 ohm speaker would be connected to the 8 ohm tap, and the 4 ohm speaker would be connected to the 4 ohm tap. In those cases damping factor would be the same.

Not that it matters in many cases. Damping factor is mainly significant when either:

1)A tube amp (or other amp with high output impedance/low damping factor) is used with speakers whose impedance varies widely with frequency. In which case higher damping factor may or may not be better, depending on the particular speaker. Or,

2)Woofer damping and control is particularly important to the particular speaker, and the damping factors of the amps being compared are not especially high.

Best regards,
-- Al

Cwaz - Power will be inversely proportional to load (assuming good power supply) while perceived loudness goes in (1/3.5) power of the amplifier output power ratios.

In you case: Loudness = (8/4)^(1/3.5)= 1.22 (22% louder with 4 ohm speaker)

8 ohm speaker will also double your damping factor (damping of the speaker).

In general, amplifiers are happier into a high impedance load, as long as they aren't driven into clipping. So assuming all else is equal (which of course it never is), I'd suggest 8 ohms if there is no danger of clipping and 4 ohms if there is.

Now all else is never equal, and apparently you've already found speakers you really like, and unless their impedance curve is really funky they'll work fine with both your amps. Having "speakers you really like" outweighs any theoretical/speculative "amps are happier with higher impedance unless blah blah". So go for it!

Again, it all depends on the interaction between the speaker and amp, the impedance , IN ITSELF, does not make the speaker sound better or worse. If your amp can handle the load fine, if not update your fire insurance.

Thanks for the answers ,yes i was wrong 8.1en is the 8 ohm . But it seems like sound wise ,,there is really not that big of a difference between 8 or 4 ohm , thats is what i am getting out of this .Correct?

The TEKTON 8.1en are 8 ohm speakers. The 8.1t are 4 ohms. 35 watts is more than enough to drive them. Your tube amp won't have a problem driving either of them. If you can use a floor stander you may want to consider the Tekton Lore. I just got a pair yesterday to go with my fully restored Scott LK72-B and they sound very good. At $850 plus shipping they are a true bargain.

My speakers are rated for 8 ohms nominal impedance, but have a low impedance of about 3.9 ohms. My old receiver wasn't rated to be 4 ohm stable and my new one is. I know there are other factors (i.e. also jumped from 90 watts to 135 watts per channel), but there is no comparison in sound. I don't know if 4 ohm speakers have as much variance as many 8 ohm speakers do.

If you find an 8 ohm speaker that you like I don't think I've ever heard anyone claim to like the sound of all 4 ohm spekaer more than all 8ohm speakers, but the 4 ohm speakers can be more difficult to find quality amplification for.

The main thing is to get speakers you like and that your amps will drive. With tubes it will not make a lot of difference as they have the output transformer to smooth out impedance. With SS it is a little more complicated, a good SS amp will double its power every time the impedance is halved, so it will have twice the power at 4 ohms as 8. Sounds good but remember that "4 ohm" speakers may go to 2 or 3 ohms in parts of the frequency range, the amp may try to increase its power output there and not have a good enough power supply to do so. So although 4 ohms gives more output 8 is a safer load for most SS amps. The only way to know for sure is to look at the impedance curve for your individual speakers and the power output curve for your amp. See, simple isn't it? LOL.

I my opinion, the best way to go; is to buy amps for speakers, not speakers for amps.