speakers on 4 ohm vs. 8 ohm taps - what's the theory?

[troporobo]

Synergy gurus: can somebody help me understand this please? I have been reading on the 'net from time to time that some people deliberately connect their 8 ohm speakers to the 4 ohm taps, or vice versa. I have not been paying close attention, but maybe this is more prevalent with low power tube amps. What's the theory behind doing it one way or another?

I was thinking about this last night after hooking up a pair of speakers I have on trial (many thanks again to a kind pinoydiophile!). The impedance wasn't labelled and I had forgotten to check, so left my cables on the 4 ohm taps (on an 8 wpc EL34 SET amp). The speakers sounded terrible, really flabby bass, flat mids, recessed highs. Turns out the speakers are 8 ohm and only 86 or 88 dB sensitivity. So I changed to the 8 ohm taps . . . success! Bass tightened up dramatically, highs and mids were brought forward and balanced in proportion, all was right with the world.

What I want to know is, why is this? What is the speaker / amp interaction that's happening? And why would some people deliberately use a seemingly mis-matched connection?

Thanks in advance

[arnoldc]

the speaker is the "load" that the amplifier sees. in order for an amplifier to sound "right", it should see the right load.

deliberate mistmatch is when say, you have a 300B that was configured with 2.5K OPT at 4 ohms tap. at 2.5K it will give more power at the expense of higher distortion, so you can put your speakers at the 8 ohm tap which is like 5K @ 4 ohm load to the 300B, which will result in less distortion.

my mind might have not settled in yet, so i could be wrong

[Hyperion]

Some people connect their 8 ohm speakers to the 4 ohm taps because many of these so called 8 ohms speakers actually drop to 4 ohms or less in the low frequency, meaning their bass performance suffer at the 8 ohm tap and usually have better bass at the 4 ohm tap. After all, the woofer is normally more power hungry than the tweeter.

On the other hand, if your speaker is a true 8 ohm speaker; then the amplifier would not be able to transfer as much power to the speaker from the 4 ohm tap. In short, the woofer is fed less power and therefore sounds looser and less dynamic.

[dinolara]

Additional questions.

For speakers rated at 6ohms, where do you tap it?

How reliable are those impedance indications?

[arnoldc]

dino, same predicament here. my kappa is 6 ohm, when i had my push pull amp, i tried on 4 and 8, didn't sound different to me. now on my set amps, i have it tapped to 8 ohm. i think it will depend a lot on the speaker's impedance over the entire frequency range.

[Hyperion]

dino,

Normally, 6 ohms nominal speakers are speakers that are 8 ohms or more on the treble and about 4 ohms on the bass, they usually sound better on the 4 ohm tap. There are however exceptions so always try either tap and see which sounds better.

[KD]

Is "mismatching" potentially harmful to equipment?

[Hyperion]

KD,

Nope.

[arnoldc]

mismatching is harmful to the pocket, i.e., ST-70 + Sonus Faber Stradivari

[Killer Mike]

mismatching is a female monkey joketime

[Audio_Tyro]

mismatching is a female monkey

Wait a minute, let me clarify... you mean if there's Miss Matching, there should be a Mr. Matching ?

[arnoldc]

hey, you two. don't pig the thread

[marty_e]

If my amp specs indicate 50wpc @ 4 ohms and there are no other speaker taps, what am i losing/gaining by using speakers that are rated at a stable 8 ohms (+/- 1.5 ohms Epos ES-14)?

[Hyperion]

marty_e,

If your amp is rated at 50wpc @ 4 ohms and you are sure that its output tap is 4 ohms, then it probably delivers slightly less power into your 8 ohms speakers ( maybe 35-40Wpc only).

On the other hand, since your speakers are easy to drive - despite lesser power delivery, 8 ohm speakers also require less current which is not the forte of most tube amps. Meaning despite slight loss in terms of power transfer - most medium power tube amps ( less than 100Wpc) tend to sound better driving 8 ohm speakers because they require less current compared to 4 ohm speakers.

[jo2]

Try Paul Speltz zero auto transformer

http://www.otlamp.com/tweaks/ps/

and click The Zero

http://www.enjoythemusic.com/magazine/e ... former.htm

http://www.audioasylum.com/audio/tubes/ ... 08243.html

http://www.enjoythemusic.com/magazine/e ... mazero.htm

[zach]

Is "mismatching" potentially harmful to equipment?

depende rin. may mga thiel na nangsusunog ng amp na bitin.

[marty_e]

Hansen, thanks a lot. The amp manual specifies power rating at 50 wpc@4 ohms. Did not provide any other spec and I only have one pair of speaker taps. In any case, they sound great so i'll not be thinking about this anymore. Besides, I have myself busy breaking in a pair of newly restored Dynaco MK3's for a friend.

[bruno]

Some people connect their 8 ohm speakers to the 4 ohm taps because many of these so called 8 ohms speakers actually drop to 4 ohms or less in the low frequency, meaning their bass performance suffer at the 8 ohm tap and usually have better bass at the 4 ohm tap. After all, the woofer is normally more power hungry than the tweeter.

On the other hand, if your speaker is a true 8 ohm speaker; then the amplifier would not be able to transfer as much power to the speaker from the 4 ohm tap. In short, the woofer is fed less power and therefore sounds looser and less dynamic.

I followed Hyperion's advise and had better bass resolution than I had with the 8-ohm tap. My speakers are B&W 602 S3 which are known to have its impedance drop to as low as 3 ohms.

But I have to crank up the volume a little bit more now. No problem with that.

[Noel_14]

Hansen,
Does this mean that I should use the 4 Ohms tap of my amplifier instead of 8 Ohms? CJ MV52-Tino
Thanks

[Hyperion]

Noel_14,

Try it and see what happens. The Tino does not drop below 6 ohms I think so it is unlikely to benefit much from the 4 ohm tap.