Eminent Technology 8b Speakers - Amp/wattage Recommendations

Consider a LSA Voyager 350 GaN amp. It is AMAZING and often on special for ~~ $2300. With quality preamp, and cables, it is capable of very holographic imagining. IMO, a match made in heaven

hth

@jwr159 Well... I’ve listened to my own QS Mono 120s w/KT150s powering both the 8b and 16 model speakers. It plays nicely at moderate listening levels, and then some. Your comment about Playing "fairly loud" is another question i’d defer back to EMT about if I were you -- asking them more about what levels of volume reasonable to do with these particular speakers. Once you hear them with good tube amps, this idea could change about what is the optimum and loudest listening levels.

While they can probably do it, my question is how long will the speakers last under sustained listening at loud levels. Are you talking all day parties, more then 2-3 hours of "loud"...hard to say. I see the QS Mono 120s combo with  8bs more as finesse speakers to play music, not loud noise. More so than I do true loudspeakers. Maybe that’s just me. Bi-amping, sure, okay. Yes, they need a little power/transformers behind them, bing closer to 82db sensitivity. Best of luck.

Thanks for the LSA suggestion. 

I admittadly have limited experience with class D amps, GAN or otherwise. But one benefit of Class D is their lack of weight. A home demo can be arranged w/o incurring a fortune in shipping costs. 

In general I prefer tubes. Too me, they breath life into music. If GAN changes the equation, I don't know. 

Thanks decooney. Thanks for sharing your experiences. Agreed, a call to EMT will likely result in some clarity here. 

I once measured my existing system using a sound meter in a much smaller room. I was amazed at how loud 95dB actually is. I can't imaging playing any speakers lounder than that other than a brief moment. So my use of "fairly loud" was not meant to imply rock concert levels hur after hour. My most likely use will be in the high 80dB levels for an hour or two. 

@jwr159 your update helps understand better, and 'hour or two" here and there would be fine for the M120s alone without bi-amping, I believe.  Best to ask EMT. Good fun.  👍

If it was me, I’d match them with a Cary SLP-98 preamp and a Parasound A21+ or maybe two. You'll have your tube goodness and the power you need to play loud.

@jwr159 for tube amps, you are on the right track with the M120s, if you can find them. I run a Cary SLP-98 as @russ69 mentioned, btw. If you bi-amp with say a capable tube amp for the upper section (which sounds glorious on those speakers btw) and some higher power SS amp for the lower woofer-bass-drive, you are going to need some kind output level control to balance it out. I’d start with one amp first, try it out before jumping to bi-amping. The QS Mono 120s work well with your 8bs, with those extra-large quality transformers. It’s not about the watts per se’, it’s about quality of power/current/transformers applied for those speakers.

I've heard the 8bs and 16s with a high quality (exceptional) 10wpc tube integrated before. It's possible, yet again its about the quality vs. quantity of power in this case.  

Thanks all for the feedback. 

Just to be clear, the QS amps I am considering are the newer KT monoblocks which are rated at 100W with the KT 150 tubes.  I will discuss with both Mike Sanders and Bruce T at EMT if these will work. 

The 120 monoblocks are no longer available. 

Yes, the plan is to bi-amp using probably a QSC amp with DSP to drive a pair of dipole subs I built. 

Your speakers sensitivity is 83dB at 1W.  Sitting at 4m distance is equivalent to 12dB drop, but second speaker adds 3dB and room reflections another 3dB.  In the end it it will be 77dB loud at 1W, 87dB at 10W, 97dB at 100W.  It might a bit less drop than 6dB for double distance since electrostatic panel is not a point source, but it is hybrid, so I'm not sure.  I would still assume 97dB loud at 100W to be safe.  97dB is very loud but choice depends on your normal listening levels.  Average power delivered to speakers is very low (few percent of the peak power), unless you listen to continuous sinewaves, but peaks are important.  I would go for 200W at 8ohm to be safe, but it will add only 3dB while theoretically 100W amp, on average, should be better than 200W amp costing the same.  Tough choice.  The best would be to borrow and try.  If you bi-amp with different amplifiers be sure to match gains.  If you plan to use xover filtering before the amp then how you disable crossover inside of the speakers? 

If you plan to use xover filtering before the amp then how you disable crossover inside of the speakers? 

You don't have to disable the internal crossovers, you are just doing it before the crossover sees it, no harm no fowl.

@jwr159 apologize if I misunderstood, originally I thought you planned to bi-amp the LFT8B speakers alone, like this on the rear. Using the QSC amp with separate subs should give you plenty. This is similar to how I run my setup, with custom dual Scanspeak subs. Works great, the QS amps don’t have to work so hard, and low level volume listening is more enjoyable too.

8B:

@russ69   I would assume that this would concatenate filters affecting not only attenuation, but also the slope dB/octave, unless filters are very far off crossover points to remove, for instance, lowest frequency (high energy) from tube amp.  I suspect that this might be OP's objective.  Either way it doesn't matter if sound is to his liking.

The plan is to use:

1.  a HP filter between my preamp and the QS amp, which will driver only the mid and high frequency panels. I am not sure of the filter frequency just yet, but probably somewhere in the 50-100Hz range. If I'm not mistaken the mid panel driver plays down to 100Hz. 

2. Use the on-board Xover on the 8s to handle the crossover between the mid and high frequency drivers; and 

3. the built-in DSP/crossover functionality in the QSC to drive my subs. . 

With the above arrangement, I believe the low frequency drivers on the 8b's will be eliminated from the equation altogether.

I assume if the QS amps does not have to amplify the low frequencies, I am hoping to get more bang out of those 100 watts. This a fair assumption? 

I would think it might be good assumption, but I'm not sure about tube amps.  It would be better to ask tube amp experts like atmasphere.

@atmasphere Ralph, could you chime in?  Does limitting low end allow to play louder?  I know that with some amps, like class D  Zobel network  limits power at high frequencies anyway.

Eminent Technology says "The LFT-8b is biampable.". So just ask the designer, the best way to do that.

Hello. I’ve owned several Magnepans over the last few decades, and I’ve used dozens of different amplifiers (tube, SS, and hybrid). You’ll have to try the amp you’re considering in your system, in your own room to truly know if it will work. I know that sounds like a Non-answer, but unfortunately, it’s the truth. For what it’s worth.. I’ve been using a 60 wpc tube amp to power my MG-3.7s for almost a year now, and they’ve never sounded better. I listen in the range of 70-85 dB average spl. A sound meter is an important tool to figure out how much power an individual needs. I’ll bet the Quicksilvers will sound great. They might not like 95 dB avg spl, but they might sound so good that 95 dB isn’t necessary. Good luck

I would think it might be good assumption, but I’m not sure about tube amps. It would be better to ask tube amp experts like atmasphere.

@atmasphere Ralph, could you chime in? Does limitting low end allow to play louder? I know that with some amps, like class D Zobel network limits power at high frequencies anyway.

The ET8b is surprisingly tube friendly and if you have 100 Watts you should be good in most rooms. If bass is filtered from the HF amp then of course you can get more sound pressure, if there is also an amplifier for the bass.

IME doing this without an electronic crossover (whether active or not) in front of the amplifier is problematic. If you don’t have such a crossover, IME you’re better off just driving the speaker with the amp you have.

One of the founders of BAT, Steven Bednarski, was a customer of ours and had 8bs. He drove them with our MA-1s which at the time (1990) were 100 Watt mono OTLs. That is why I say this speaker is tube-friendly. Steven’s warranty form says that the amp was the best he had ever heard so I have to assume it worked pretty well.

So I’d just hook that QS up and play tunes! Use the 4 Ohm tap if memory serves.

Thanks everyone who posted and contributed to this thread. Very helpful and informative. Most of what I have heard is positive, and it would seem using the 100W QS will be a good match with the 8bs as I plan on using them. And yes atmashpere, I do plan on using a HP filter in front of the QS. I will contact Bruce T to discuss and confirm, but it seems like the QS monoblocks is the way to go for me.  

@jwr159: I’ve been away from home for a coupla weeks, and have been playing catch-up, just now seeing your thread. First, congratulations on your new speakers! And on your good taste ;-) . The ET LFT-8b is an outrageous bargain, imo one of the best in all of current hi-fi. Why most audiophiles continue to ignore it is a complete mystery.

Here are some facts that may help with your amp considerations:

- The 8b run full range is a pretty even 8 ohm load. However, the magnetic-planar panel itself---when used in a bi-amp manner---presents the amplifier with an almost purely resistive 11 ohm load, great for tube amps. Whereas Magneplanars (a pair of which in addition to the 8b I also own) present the amp with a 3-4 ohm load and therefore benefit from a solid state amp, the ET loves tubes. I’ll bet the Atma-Sphere M60 would sound great with the 8b (I sold mine before I got the ET’s), and I can also recommend both the Music Reference 100 watts amps: the RM-200 Mk.2 (which uses a pair of KT-88’s per channel, a real engineering feat to create 100 watts!) and the RM-9 Mk.2 (a quartet of EL34’s per channel). You can then use a solid state amp to drive the sealed woofer. As you must know by now (but some posters on this thread may not), the magnetic-planar panels and the dynamic woofer each have their own bindings posts, simplifying bi-amping.

- If you are going to not only bi-amp, but use your own subs in place of the 8b’s woofer (in pojnt number 3 in your above post you refer to "my subs") , know that the crossover between the woofer and the m-p drivers is at 180Hz, a simple 1st-order (6dB/octave) symmetrical filter. Very few subwoofers will play up to 180Hz (and above: remember, the x/o is 1st order), so don’t expect to be able to use any ol’ sub. Bruce Thigpen worked very hard to come up with a woofer that blends well with his LFT driver. As with all dipole loudspeakers, the ultimate woofer to use with the 8b is an open baffle design (why that is so requires more explanation than may be appropriate in this thread). If employing outboard woofers, you may simply leave the binding posts on the 8b woofer enclosure disconnected.

bdp24 thanks for the reply. 

Your are correct, I built my own dipole subs. They are capable of playing up to 200Hz. So I think they will mate well with the 8bs. 

As for the amps, I would consider Music Reference but they are hard to come by. I will be in Sacramento next week and plan on taking a drive down to Quicksilver and having a listen of the KT mono amps. Should be interesting/fun. 

I’ll probably get yelled at for this, but I had the LFT-8b in a small room (10’x20’) a few years ago. It was powered by a Luxman MQ-70, a rare 35x2 EL-34 tube amp influenced by Tim de Paravicini. Well, it rocked without clipping and distorting, easily into the 90db’s, maybe even 100db peaks. This was also considering sitting about 7-8’ away. One thing to consider is the added gain from a preamp, which is likely 8-14db, and room gain. Once you add all that up, it boils down to the quality of the current and of each watt.

Given the OP’s room size, a more powerful amp might be needed, but perhaps not necessarily.

or...Consider the Bob Carver tube mono blocks. They put out 350 wpc tube power!

I am using them, and they are great! I also have the JL Audio CR-1 crossover that sends the low lows to my 4 JL F-113 subs.

ozzy

The Carver monos at $9500 is beyond what I wish to spend. 

Although I have not heard the Quicksilvers yet, I like everything else about them.  The utilitiarn look, no hype, no money wasted on marketing, a stellar name behind the brand, great customer service, and tons of positive reviews from real users. Cost is reasonable as well. 

I am glad I posted here on the forum. Many of the responses have removed my concerns. Thanks.  

@jwr159 I've heard your 8bs and the smaller LFT-16s on QS amps more than ten times in a slightly larger room than yours. Always a treat.  Also, heard the smaller 16s with my same Mono 120s with KT150s too, very nice.  The new version monos should do it nicely for ya.   

@jrw159: One thing to know about open baffle woofers is that because of their inherent dipole cancellation characteristic (the front and rear waves meeting on either side of the open baffle frame, the opposite polarity waves causing a drop off in the very low frequencies), a dipole cancellation compensation network is necessary. Brian Ding installs just such a circuit into the A370 plate amp that is included in the Rythmik Audio OB/Dipole Subwoofer kit.

bdp24 thanks for the pointers on the Rymthmik plate amp. My subs, although dipoles, are different. Maybe a dozen years ago, there was a speaker company called Surreal Sound that made a speaker called Fifth Row. They never made it commercially. A few months back I managed to purchase on the cheap the modules needed to build their subs from the designer. Here is a link that shows the subs. The plan is to drive the subs with a QSC amp and the 8bs with probably the Quicksilvers. 

I have been listening to 8b’s for three years now. My room is 9 x 28, so quite a bit smaller than @jwr159. I am running a 20w Mactone-MH 300b tube amp, 300b in push- pull. I prefer this to the other 100w Von Gaylord Nirvana tube amp I own. 95db is easily achievable. Sorry no experience with the QS. But I can confirm that tubes are a great fit, and not as challenging a load as Maggies.

This is a total aside, but Bruce has come up with a 8c woofer upgrade. It’s a drop in replacement for the existing woofer units, but with a built-in plate amps, DSP room correction, a new crossover for the panels...etc. Any comments? I’ll take it to another thread, if the OP does not want the distraction. 

No worries at all ledoux1238 about discussing the 8c woofer upgrade in the context of this thread.

Unfortunately in my case, the 8c woofer upgrade was released by ET well after I invested money and a whole lot of labor into building my subs. So the 8c upgrade is a bit late for me. That said, if the 8bs have a weak link, it was the bass. I can only assume Bruce has addressed this issue with the 8c upgrade.   

There is a new listing on USAM for a Music Reference RM-200 MK.2, asking price $3,000. The amp has been Michael Fremer's "reasonably-priced" reference tube amp for about 20 years. Roger Modjeski's engineering brilliance allowed him to produce 100 watts out of a pair of KT88 tubes, and without sacrificing tube life. The amp has Classic written all over it. 

@jwr159 I have tried to get a pair of OB dipole subs' from Danny Richie; however, there have been shortages of one items or another for the past year and a half.

An integrated woofer solution such as the 8c seems to fit my situation. However, there are comments from  another forum regarding the DSP room correction software and the introduction of A/D and D/ A signal conversions. Apparently, Martin Logan uses similar DSP in their woofers albeit in maybe a higher quality plate amp? It is  this DSP stuff that I would appreciate comments on. 

Your subwoofer design is all analog, I presume?

There are many ways to integrate your subs.  None of them, however are ideal. 

I am not a fan of using a L & R of mini DSP units as active cross overs between the subs and the mid LFTs. As you indicate, that requires A/D and D/A conversions. 

I will probably do a mix of analog and digital. My preamp has RCA and balanced outputs. The RCA outs will be fed through an analog HP filter and then to my main amp. The balanced outputs will go to a QSC amp with DSP and LP filter. A plate amp can be used as well. Although I have not tried it yet, my understanding is the A/D and D/A conversions really do not matter at the lower frequencies. 

I will probably call Bruce T tomorrow.  Besides discussing amps, I would like to learn more on how he implements the 8c subs, crossover frequencies, etc. 

Now that the 8c is available, I would be inclined to use Bruce's solution over the GR Research subs, assuming you can bi-amp and avoid the A/D and D/A conversions for the mid and high LFT drivers. 

ledoux1238 can you talk a bit more about your experiences of using a 20 watt amp with the 8bs?

Are you bi-amping. Is the Mactone driving only the mid & high LFTs or also the sub drivers as well? 

Are you hearing any noise or distortion of the amp at 95 dB?

Are their any compromises in your view of using a lower watt amp with these speakers?

Do the 100 watt amps do some things better? 

I don’t yet know anything about the new ET woofer system for the LFT-8, but unless it’s a dipole design I can’t see how it will be as good a mate as is any dipole sub (including the Rythmik Audio/GR research OB).

Magnepan is working on a "concept" model which will include dynamic (cone) woofers of OB/dipole design to augment their well-known magnetic-planar midrange/ribbon tweeter panels. Their MG30.7 model uses very large panels to reproduce bass frequencies, those panels sharing with OB/Dipole subs the same acoustic properties.

I own a pair of the Magneplanar Tympani T-IVa loudspeakers, which is basically a 30-year old version of the MG30.7. The Rythmik Audio/GR Research OB/Dipole Sub comes closest to equaling the outstanding sound of the T-IVa bass panels as I have yet to hear. Remember when Harry Pearson created his own "Super Speaker" by using the Tympani bass panels with the midrange/tweeter panels of Infinity?

OB/dipole woofers share with dipole planar loudspeakers the same drop off in SPL output as speaker-to-listening position distance changes. Omnipole subs (sealed and ported boxes) do NOT, so the sub/speaker balance is "correct" at only one speaker-to-listening position distance. That is imo a major flaw, one inherent in the mating of dipole loudspeakers with omnipole subs. Dipole subs also load the room the same way dipole loudspeakers do, very differently than boxed loudspeakers and subs. Mating omnipole subs with dipole loudspeakers is doomed to failure: it can’t be done, at least not to perfectionist standards.

@jwr159 I am going to change amps this weekend, give a more considered A/B and report back next week regarding 100w vs 20w amps' SQ on the 8b.

@bdp24 New 8C upgrade consists of dipole woofers, front firing 8" and back firing 6", but in a closed box, not OB+ DSP / plate amp.

One thing to consider is the added gain from a preamp...

The power amp drives the loudspeakers, the preamp drives the amp, there is no additional gain to the loudspeakers from the preamp. As long as the preamp provides enough voltage to drive the amp to full power that is all that happens. Maybe I'm missing what you are saying? 

Here is a link to the ET website describing the 8c update. For $1500, it is probably well worth it. 

http://www.eminent-tech.com/LFT-8cwooferupdate.html

VERY interesting. Thanks @jwr159.

bdp24, my understanding is your are using the GR Research OB subs in place of the sealed subs on the 8bs. May I ask the details on how you are implementing the bi-amping.  Are you using a high pass filter of some kind between your main amp and the LFT mid and high freq panels? 

BTW, I called ET yesterday and mentioned adding dipole subs with the 8bs. They suggested running the dipole subs in parallel with the sealed subs on the 8bs. The supposed advantage is that with 4 subs in the room, room modes will be mitigated. Probably worth experimenting, but I am not sure it will be easy to get the sealed and dipole subs to integrate well together.