[bdp24]

I'm about to receive a pair of the Eminent Technology LFT-8b speakers, and am wondering if the RM-200 amp would be appropriate for driving them. The details I should include are that the speaker is a magnetic planar-cone woofer hybrid, with a symmetrical 1st-order x/o at 180Hz between the midrange panel and the cone woofer, and also between the mid-panel and the tweeter at 10K. Bruce Thigpen rates the speaker as an 8 Ohm load, with the panel alone being a 12 Ohm one. I mention that because I'm going to use the panels but not the cone woofer (they are both connected to the x/o on a barrier strip, and can be used independently), therefore the RM-200 will be seeing a mostly-resistive 12 Ohm load. In addition, the speaker is very low sensitivity, 84dB. In view of all the above, is the RM-200 a sensible amp for this speaker in a 10 X 13 X 19 room, playing a lot, but not all, acoustic instrument music (Baroque, Singer-Songwriter, Bluegrass)? I'd love to hear from Roger on this, but anyone else as well!

[jimdgoulding]

Does RM-200 stand for 200 wpc?  I guess you'll know the answer to your question soon enough tho I'm sure you'll get more definitive answers than this one in the forum.  I've heard those speakers quite recently and I'm even thinkin the chap was using that very amp.  I think his were a bit too close to the wall behind them.  I know I would experiment space permitting.  The sound, btw, was fabulous.  We were listening mostly to acoustic jazz in a large room.

[bdp24]

No, it's 100W/ch, approximately. Where did you hear the ET speakers, if I may ask?

[Roger A. Modjeski]

I'm about to receive a pair of the Eminent Technology LFT-8b speakers, and am wondering if the RM-200 amp would be appropriate for driving them. The details I should include are that the speaker is a magnetic planar-cone woofer hybrid, with a symmetrical 1st-order x/o at 180Hz between the midrange panel and the cone woofer, and also between the mid-panel and the tweeter at 10K. Bruce Thigpen rates the speaker as an 8 Ohm load, with the panel alone being a 12 Ohm one. I mention that because I'm going to use the panels but not the cone woofer (they are both connected to the x/o on a barrier strip, and can be used independently), therefore the RM-200 will be seeing a mostly-resistive 12 Ohm load. In addition, the speaker is very low sensitivity, 84dB. In view of all the above, is the RM-200 a sensible amp for this speaker in a 10 X 13 X 19 room, playing a lot, but not all, acoustic instrument music (Baroque, Singer-Songwriter, Bluegrass)? I'd love to hear from Roger on this, but anyone else as well!

Once again the most important thing is missing. How loud do you listen? I want a number at 1 meter from one speaker.

[jimdgoulding]

No, it's 100W/ch, approximately. Where did you here the ET speakers, if I may ask?

At an audio club member's house in Houston, TX in his dedicated listening room. 

[bdp24]

Well Roger and anyone interested, I'll let you know how well they work together, 'cause I went ahead and nabbed the MR-200 while the nabbin' was good, used on Audiogon. It's the original version, not the Mk.II. I'm more of a music lover than audiophile (sure, that's what they all say), so the difference between the two versions doesn't bother me. I'm sure either will have satisfied me. But out of curiosity (so much for the previous disclaimer!), how much and what kind of difference is there between the two? I mean, just in case I want to get another and run them bridged. They can be run that way, right? Say, how do I subscribe to the Music Reference thread on AudioCircle, so that I get notified of responses to my postings? Thanks all.

[bdp24]

At an audio club member's house in Houston, TX in his dedicated listening room.

I just looked at my question to you, and was horrified to see how I spelled hear. Especially as this is an Audiophile forum! I corrected it in my posting, but of course couldn't make the correction in your quotation of it. Sorry English teachers, and other literate types!

[Roger A. Modjeski]

Well Roger and anyone interested, I'll let you know how well they work together, 'cause I went ahead and nabbed the MR-200 while the nabbin' was good, used on Audiogon. It's the original version, not the Mk.II. I'm more of a music lover than audiophile (sure, that's what they all say), so the difference between the two versions doesn't bother me. I'm sure either will have satisfied me. But out of curiosity (so much for the previous disclaimer!), how much and what kind of difference is there between the two? I mean, just in case I want to get another and run them bridged. They can be run that way, right? Say, how do I subscribe to the Music Reference thread on AudioCircle, so that I get notified of responses to my postings? Thanks all.

Tube amps in general cannot be bridged. That honor applies to transistor amps. However tube amps can be paralleled for mono operation but that is a tricky business. I did a very good mono switch on the RM-10. One thing about paralleling tube amps is that they need a speaker of half the impedance of the tap value to get the full power. Thus a 8 ohm paralleled amp needs a 4 ohm speaker to get the full stated power.

I still haven't heard how loud you listen???????????? We cant really have a discussion about power until I do.

If you look to the right of the reply button below you will see a "notify" button. That will send you an email when someone replies to this topic. Thanks for joining us with your RM-200. The differences are mainly in the output transformer's  high frequency response which is much better.  However the MK-I is still better than most tube amps. I have high standards about such things as noted by Stereophile reviews.

[/mp]

One thing about paralleling tube amps is that they need a speaker of half the impedance of the tap value to get the full power. Thus a 8 ohm paralleled amp needs a 4 ohm speaker to get the full stated power.

Does this technique make paralleled tube amps a viable match with ultra low impedance speakers (e.g. <1 ohm min Martin Logan products)?  I.e. Is there a minimum below which it doesn't work well?

[bdp24]

Thanks for the info Roger. I looked at the RM200 info on the Music Reference site after asking about bridging, and concluded that doing so is not an option with that amp. That's all right, I can use it with my old Quads for now if it's not enough amp for the Eminent Technologies. Yes, the RM10 is the better choice for that speaker, but I plan on getting a pair of 988's or 989's eventually as well, and I can use the 200 on them. I can get an RM10 for the 57's later. Then again, a direct drive amp would be even better on either of the ESL's. It's all good!

[bdp24]

Oops, forgot one question Roger. Do you offer an RM200 to RM200Mk.II upgrade, and if so the price? It might be more cost effective to sell the Mk.I and buy a Mk.II, ay?

[Roger A. Modjeski]

The upgrade includes new output transformers, re-tuning the amp for those transformers, upgrading some parts and circuits. It costs $1900. The transformers will be wound by me personally.

[bdp24]

And the amp will then be an RM200Mk.II-T?

[Roger A. Modjeski]

And the amp will then be an RM200Mk.II-T?

yes, except for the cap forming switch. We can make the main switch forming but then you have to turn the amp off completely through a power strip or leave it in forming mode all the time. Its only 10 watts in forming mode.

[tubegroove]

Tube amps in general cannot be bridged. That honor applies to transistor amps. However tube amps can be paralleled for mono operation but that is a tricky business. I did a very good mono switch on the RM-10. One thing about paralleling tube amps is that they need a speaker of half the impedance of the tap value to get the full power. Thus a 8 ohm paralleled amp needs a 4 ohm speaker to get the full stated power.

Besides providing the extra watts, will running the RM10 in mono mode (using a 4ohm speaker on the 8 ohm tap) further improve its performance in the low frequencies?

[Roger A. Modjeski]

Besides providing the extra watts, will running the RM10 in mono mode (using a 4ohm speaker on the 8 ohm tap) further improve its performance in the low frequencies?

Paralleling channels does not change frequency response but the extra power and lower impedance will sound different with speakers with varying impedance as the damping is increased. The way to look at it is that the voltage stays the same but the current doubles on any particular tap. That is why the 8 ohm tap is loaded at 4 ohms to get the double power. On the 8 ohm tap the power is increased by about 1.4 times.

[tubegroove]

Paralleling channels does not change frequency response but the extra power and lower impedance will sound different with speakers with varying impedance as the damping is increased. The way to look at it is that the voltage stays the same but the current doubles on any particular tap. That is why the 8 ohm tap is loaded at 4 ohms to get the double power. On the 8 ohm tap the power is increased by about 1.4 times.

Thanks
The origin of my question stemmed from a recent opportunity to listen to the RM200MkII side by side my RM10MkII
Two aspects of the sound from the RM200 consistently stood out – better low frequency presence/ definition and overall it sounded louder, I guess maybe due to wider bandwidth, more watts and more current.  The playing louder is not that important to me
Having said that, I must say I preferred the overall tone of my RM10!  It’s a fine amp no doubt but if I could extract more LF that would be an added bonus.

I now understand that the frequency response of the RM10 does not change in mono mode.  The question in my mind is – Is it logical to think that using a pair of RM10s in mono mode might help to bridge the gap in the LF performance between the two models (for the reasons Roger articulated)? I say bridge the gap since I assume the wider bandwidth of the RM200 transformers will always give it an edge.
Or does that not make engineering sense and I am getting greedy and perhaps should just drop it and enjoy the RM10 as is – which is great, just so no one misunderstands.
-   I listen around 75-80db (measured 1m from one of the speakers), maybe once in a while 85dB
-   Speakers are bookshelf @ 4ohms which are supposed to have benign impedance and phase curves across ~80Hz-8kHz.  Currently speakers are connected to the 4ohm tap of the RM10
Thoughts/suggestions appreciated

[Roger A. Modjeski]

Thanks
The origin of my question stemmed from a recent opportunity to listen to the RM200MkII side by side my RM10MkII
Two aspects of the sound from the RM200 consistently stood out – better low frequency presence/ definition and overall it sounded louder, I guess maybe due to wider bandwidth, more watts and more current.  The playing louder is not that important to me
Having said that, I must say I preferred the overall tone of my RM10!  It’s a fine amp no doubt but if I could extract more LF that would be an added bonus.

I now understand that the frequency response of the RM10 does not change in mono mode.  The question in my mind is – Is it logical to think that using a pair of RM10s in mono mode might help to bridge the gap in the LF performance between the two models (for the reasons Roger articulated)? I say bridge the gap since I assume the wider bandwidth of the RM200 transformers will always give it an edge.
Or does that not make engineering sense and I am getting greedy and perhaps should just drop it and enjoy the RM10 as is – which is great, just so no one misunderstands.
-   I listen around 75-80db (measured 1m from one of the speakers), maybe once in a while 85dB
-   Speakers are bookshelf @ 4ohms which are supposed to have benign impedance and phase curves across ~80Hz-8kHz.  Currently speakers are connected to the 4ohm tap of the RM10
Thoughts/suggestions appreciated

I am surprised you hear much of a bass difference with at speaker that only goes down to 80 Hz as both amps go lower than that. However the Rm-200 has a bit more damping and more current. I would always advise an RM-200 over a pair of RM-10s. It's more power and versatility for about the same money and fewer tubes to maintain.

If you want better bass, why not get a sub? You cant expect an amplifier to coax bass out of a speaker that has none.

We make a very very good sub. I bought a pair of the Pioneer BS-22 speakers which are great, except for the lack of bass. With my woofer I can enjoy them almost as much as my Electrostats.  I put them in the same system run by the RM-10. Crossover is 24 dB/octave, 100 Hz, woofers run by 200 watt SS amp. These are my air-resistance loaded, below resonance very fast woofers. They are discussed in my ESL (sticky) speaker post.

[tubegroove]

Ok, I will read up on your sub, thanks for the tip
Btw, my speaker goes down to 45Hz not 80.  I should have clarified that 8-80hz is the part of the freq curve where the impedance and phase is almost flat.