4 versus 8 ohms

I have an ST-120 and love it. Right now I'm using Ascend Sierra 2 speakers, which are 8 ohm. I just ordered a pair of Magnepan LRS, which are 4 ohm. If I like the LRS then I am planning on keeping both models.

The ST-120 transformer can be connected to the speaker terminal with either a 4 ohm or 8 ohm tap. I'm using the 8 ohm. I asked Bob Latino about the effects of a mismatch and he said it may sound different using the 8 ohm with 4 ohm speakers (such as less bass or some other change) but there is no mechanical or electrical harm to anything. Basically he said to try both and see which one sounds better. That makes sense and I'm planning on doing that.

However, I thought I'd post here to see if anyone would like to share their experience/views of matching up the 4 or 8 ohm taps with their own speakers and how much of a difference it made.

monkuboy wrote:I have an ST-120 and love it. Right now I'm using Ascend Sierra 2 speakers, which are 8 ohm. I just ordered a pair of Magnepan LRS, which are 4 ohm. If I like the LRS then I am planning on keeping both models.

The ST-120 transformer can be connected to the speaker terminal with either a 4 ohm or 8 ohm tap. I'm using the 8 ohm. I asked Bob Latino about the effects of a mismatch and he said it may sound different using the 8 ohm with 4 ohm speakers (such as less bass or some other change) but there is no mechanical or electrical harm to anything. Basically he said to try both and see which one sounds better. That makes sense and I'm planning on doing that.

However, I thought I'd post here to see if anyone would like to share their experience/views of matching up the 4 or 8 ohm taps with their own speakers and how much of a difference it made.

My only comments besides bob's is "Dont change tap with power on"

peterh wrote:

monkuboy wrote:I have an ST-120 and love it. Right now I'm using Ascend Sierra 2 speakers, which are 8 ohm. I just ordered a pair of Magnepan LRS, which are 4 ohm. If I like the LRS then I am planning on keeping both models.

The ST-120 transformer can be connected to the speaker terminal with either a 4 ohm or 8 ohm tap. I'm using the 8 ohm. I asked Bob Latino about the effects of a mismatch and he said it may sound different using the 8 ohm with 4 ohm speakers (such as less bass or some other change) but there is no mechanical or electrical harm to anything. Basically he said to try both and see which one sounds better. That makes sense and I'm planning on doing that.

However, I thought I'd post here to see if anyone would like to share their experience/views of matching up the 4 or 8 ohm taps with their own speakers and how much of a difference it made.

My only comments besides bob's is "Dont change tap with power on"

Whew, thanks for reminding me!

As most speakers have different impedance at different frequencies, the stated impedance of a speaker is usually an "average" impedance.  And because some speakers have a VERY wide range of impedance (some box/horn speakers, electrostatics, etc.), tube amp speaker taps can act as a tone control -- connect it where it SOUNDS the best.

I have a pair of Magneplanar MMG's, and like the LRS, they are a resistive, almost constant load of 4 ohms -- so therefore the different taps do not act like a tone control.  Normally people would just connect these to the 4 ohm taps and walk away.  However, I found that the 8 ohm tap will go louder (and it should, as it will swing more voltage), and in a large room, the Maggies need this power.

I do wonder though if the 8-ohm tap would stress output tubes or transformers too much if used long-term.

I don't worry about it though as the above was just a trial.  I normally use the ST-120 connected to Quad ESL's, and the Maggies are in another room connected to a sand amp (~150 WPC).

You use speakers with very little sensitivity.
I prefer boxes with a sensitivity of around 100dB.

monkuboy wrote:I thought I'd post here to see if anyone would like to share their experience/views of matching up the 4 or 8 ohm taps with their own speakers and how much of a difference it made.

I have a pair of Klipsch KLF10's rated at 8ohm impedance. When I switched them from the 8ohm taps to the 4 ohm taps on my Dynaco ST-70 series II, the bass just exploded! Before then, I had resolved myself to the idea that these large speakers just didn't have that much bass. They have amazing bass, full, complex and resolving.

I read that switching from 8 to 4 ohm narrows your soundstage, well when I switched back to 8 ohm just to check, I noticed no increase in soundstage, just a thinning of the bass.

Technically, the 4 ohm tap should offer the least amount of distortion since it has the least windings, but I'm sure that depends on how the amp was designed.

I'm staying on 4 ohms.

it fully depends on the speakers. All have different impedance characteristics, which change over frequency.
Most of the differences will show up in the lower ranges (say up to 200Hz) but then some speakers will also have some impedance changes in the very high ranges.
So the deal is, try it both ways, and see which sounds better for your particular speakers and amps (and your ears).
Glad that you figured out that on your system, the 4 ohm setting works best with your speakers even thought they may be rated at 6 or 8 ohms.

Well I found out that the VTA-70 and 120 amps now come with three speaker posts per channel as standard, and I was able to buy a pair of those to replace my double posts on the ST-120. I wired the 4 ohm tap to one of the positive posts and the 8 ohm to the other and then played a couple of tracks I normally use for evaluation purposes to compare. Maybe it is my old ears but no differences stood out to me. I thought maybe the 8 ohm sounded better but I'm not sure and it wasn't something that was consistent. I think I'd have to listen some more, but I'm just glad to have that 3-post solution to make the 4 and 8 ohm taps readily available. It wasn't a lengthy comparison (just played a couple of tracks 3 times each) and I didn't play them really loud, just at normal levels.

The comparison was done with my Ascend Sierra 2 speakers, which are 8 ohm. The 4 ohm Maggie LRS are still on order, probably won't arrive until October.

A lot depends on the complex impedance curves of the particular speakers as pointed out previously, but in general, the speakers will be louder on the 8 Ohm tap, and the bass will be more controlled on the 4 Ohm tap. (Controlled means it sounds like it is tighter and purposeful rather than a bit sloppy if that helps) I use the 8 Ohm because I need the volume on some of my speakers, and to me the bass sounds great even on the 8 Ohm tap feeding 6 Ohm nominal speakers (Dynaudio S40). If you can't hear a difference stay with the 8 Ohm and enjoy the additional power out.