two possible dumb questions

[VinylSound]

Q1: What is the effect of having 8 ohm amps driving 4 ohm ML speakers? Corollary, is there a benefit to having amps reconfigured for 4 ohms?

Q2: When bi-wiring the SL3s, I seem to not need the power cord whereas not bi-wired, power cord is essential. Why? Is there a benefit to using the power cord when bi-wiring?

Many thanks to everyone in ML land

Doug
White Stone, Va

 

[captain_tinker]

VinylSound,
A really good answer to the first question would really be given by someone with an electrical engineering degree, or at least some good knowledge of electricity and how it works. I have limited knowledge on the subject, but according to what I understand, ohms is a measure of resistance. The lower the number, the less resistance I think. Also, if I understand correctly, the less resistance, the more power that can get through.

So for example, lets say an amp can put out 100 watts at 8 ohms. If you use a 4 ohm speaker, that is half the resistance, and thus technically double the watts, so 200 watts at 4 ohms. Not all amps are able to handle that higher load though, so you will want to research to see if it is ok for your specific amp to handle the load.

So I guess to answer your corollary question, an amp that is configured to be able to handle a 4 ohm load should be more stable at that load than perhaps an amp built to handle only 8 ohm loads.

I hope that this helps out so far. As for the power question, I am not sure what to tell you about that, as I am not familiar enough with the speaker in question to tell you. Though I am pretty sure that the power cords on the ML speakers are for charging up the ESL panel. So, why it would not be necessary when bi-wiring, I don't know. That doesn't make sense to me. Hopefully one of the other guys here who knows more about that will reply.

-capT

 

[Kenscollick]

The only dumb question is one that is not asked.

Q1 Most amps are rated into 8 ohms it is just the standard your amp will deliver more power into 4 ohms up to double if truly a high current design. there is not really a way to configure it to 4 ohms. Dont worry about it, enjoy the music.

Q2 The ES panel requires AC power to operate it doesnt matter if you are bi wiring or not. If you changed wires very soon after unplugging them they will stay energized for a while. most speakers will benefit sonically by bi wiring.

 

[MotorToad]

Q1: What is the effect of having 8 ohm amps driving 4 ohm ML speakers? Corollary, is there a benefit to having amps reconfigured for 4 ohms?

Q2: When bi-wiring the SL3s, I seem to not need the power cord whereas not bi-wired, power cord is essential. Why? Is there a benefit to using the power cord when bi-wiring?

Many thanks to everyone in ML land

Doug
White Stone, Va

I'm guessing here, but I'm going to say you listened to them, then bi-wired them and listened to them again unplugged. The power charges the electrostatic panels and this charge stays with the speaker for some time, so if they were powered and then unplugged they'll still sound good for a bit. There's no difference to the speaker between combined and bi-wiring. You always need power to the speaker.

An amplifier isn't "8 Ohm" or "4 Ohm," but it might have a limit to how low an impedance it can drive due to its output impedance and current capacity. It's really too broad a subject to cover here! Suffice to say, that if your amplifier isn't up to the task of ESLs, you should know it. It'll sound like crap from excessive distortion and/or you'll be blowing fuses, power supplies, or output transistors.

 

[Tj Bassi]

Is he referring to a tube amp with multiple taps on the output transformer?

Tj-

 

[amey01]

Q1: Most amps are not "configurable" between eight and four ohm loads, however all but the most basic are capable of driving a four ohm load. A four ohm load has less resistance and therefore allows more current draw. A good quality amplifier will double its power output in this scenario. A poorer quality amplifier will not be able to do this, but should still have no problems driving the four ohm load provided you use common sense.

Now, some amps are configurable to four ohm loads. From my understanding, basically this means that (in four ohm configuration) they reduce current flow so they don't blow themselves up. This reduction in current flow will result in a reduction in sound quality too, so the best advice is to use the eight ohm configuration (unless we're talking about a valve amp here). Just use common sense and don't overdrive the amp! If you can't do this (or have people around that can't be trusted then it would be safer to configure it to four ohms).

Q2: It doesn't matter about bi-wiring or single wiring - you will need the AC power.

 

[taylode]

Q1:

Now, some amps are configurable to four ohm loads. From my understanding, basically this means that (in four ohm configuration) they reduce current flow so they don't blow themselves up. This reduction in current flow will result in a reduction in sound quality too, so the best advice is to use the eight ohm configuration (unless we're talking about a valve amp here). Just use common sense and don't overdrive the amp! If you can't do this (or have people around that can't be trusted then it would be safer to configure it to four ohms).

I don't think I agree that droping from 8ohm to 4ohm reduces the sound quality. If you have multiple taps you should try the different ones to see which sound best with the speakers in question. It's not always the one you would expect. I have mine set to 4ohms and thats what I think sounds best.

 

[SteveInNC]

It's been awhile since I had to deal with any of this, but the following should be basically correct:

Resistance (R) is not quite the same as impedance (Z), which is what we're talking about with speakers and amplifier outputs.

Impedance matching is significant at high frequencies (like video) to minimize reflections or ringing in the transmission line or wire.

Impedance matching is important for tube amps at audio frequencies because it affects the efficiency of related power transfer to the speakers. Tube output stages tend to have high impedance. A high impedance source driving a low impedance load like a speaker tends to waste energy (converted to heat) rather than transferring it to the speaker. Typically, a multi-tap transformer in the amp is used to match the output stage to the speaker impedance.

For SS amps, what's really in play is impedance bridging, which is related to the amp's damping factor: aka the ability to control the load. An SS amp's output impedance is actually very low (<0.1 ohms) compared to the speaker. Damping factor is equal to the load's impedance divided by the source's impedance (Df = Zspeaker / Zamplifier). Higher damping factors in SS amps are generally considered to be better because they control the movement of the speaker better, limiting overshoot, etc.

Speaker impedance varies with frequency. Logans are really hard loads, because at higher frequencies, their impedance can drop to less than 1 ohm. As seen in the damping factor equation above, this means that the panels are harder to control at higher frequencies (lower damping).

Now a real EE will step in and tell us how all of the above is wrong

 

[amey01]

I don't think I agree that droping from 8ohm to 4ohm reduces the sound quality. If you have multiple taps you should try the different ones to see which sound best with the speakers in question. It's not always the one you would expect. I have mine set to 4ohms and thats what I think sounds best.

You have a valve amp! I said "unless it is a valve amp". I was talking about the recievers and budget stuff that is generally switched between eight and four ohm loads.

 

[taylode]

You have a valve amp! I said "unless it is a valve amp". I was talking about the recievers and budget stuff that is generally switched between eight and four ohm loads.

Well maybe I'm confused, wouldn't be the first time. What is a valve amp? I didn't think that a SS amp could also be a valve amp.

 

[twich54]

What is a valve amp? I didn't think that a SS amp could also be a valve amp.

A 'Valve' amp is one which utilizes vacuum tubes for it's output rather than transistors. While some amps operate as 'Hybrids' (tube input / buffer stages combined with SS output stages) they are not true 'Valve' amplifiers.

 

[VinylSound]

Thanks! It's tube amp; i shulda said

Fellow Logan-ears,

Thanks for the info about the 8ohm v 4ohm issues. I can have the mfgr. reconfigure the amp o 4 ohms, just want to make sure it's going to help the sound generally.

As fate would have it, I wasn't able to turn on the speakers today, so I will try them tomorrow w/o the power cord and see if there is sound (which I believe there will be, more on that later).

Anyhow thanks again for the thoughts!

Doug

 

[Pcar928fan]

As fate would have it, I wasn't able to turn on the speakers today, so I will try them tomorrow w/o the power cord and see if there is sound (which I believe there will be, more on that later).

If there is sound out of your STAT panels (the woofers WILL make sound unless they are the new speakers w/ on board amps) and they have been unplugged for more than an hour even, you need to get something fixed. The panels work via a static charge and the ONLY way they are designed to be charged is if they are plugged into a wall and the transformer charges the panel. There is NO POWER from your amp that makes that charge, it ONLY directs the panels how to move.

 

[taylode]

A 'Valve' amp is one which utilizes vacuum tubes for it's output rather than transistors. While some amps operate as 'Hybrids' (tube input / buffer stages combined with SS output stages) they are not true 'Valve' amplifiers.

Thanks Dave! I didn't think I had a valve amp.

 

[Dreamer]

I'd agree with most of the previous posts in that it's not so much what your amp is rated for, but rather impedance matching, particularly when running amps bridged. A lot of 8-ohm amps will run hot and get a little unstable when run bridged mono into a low-ohm load like ML speakers. There are a few solutions to this situation, most of which involve spending a fair bit of money.

1) you can get an amp with REALLY high damping factor and high current, and hope that it can handle it when you run it bridged into a 4-ohm speaker.

2) you can use some sort of impedance matching gadget to put between the speaker and amp, so that the amp is fooled into thinking that that it's driving an 8[ohm load. The Speltz Autoformer is one of these such devices. Several members of this forum use this to make their ML's look like an 8-ohm load, and from all accounts they do make a difference.

I have a pair od CArver M-500t's which I bought to run bridged mono to power my Sequels, and although they do sound fantastic at low levels, they seem to get a little sloppy in the bass at high volumes, and I attribute that to the reduced damping factor when running them bridged. Although the power output is "only" 250wpc/8ohms (something like 500wpc into 4ohms) in stereo mode (as opposed to over 700wpc when bridged into a 4-ohm load) it actually sounds better running a single amp in stereo, because the damping factor is much higher, and they don't run out of steam at high volumes. I've been considering getting a pair of Autoformers so I can run them bridged, but for a little more than half the cost, I could get a 600x2 Sunfire or a pair of Silver 7t monoblocks, either of which can run my Sequels to ear-splitting volumes, and have a 4-ohm output approaching 1000wpc and are stable down to below 2-ohms.

There are a lot of other high-current amps that are happy with the ML load--Plinius, Krell, Levinson--but most of them are just out of my price range, and I'm not really a big fan of the Class-A sound.

Of course, YMMV...

--Richard