Eminent Technology 8b Speakers - Amp/wattage Recommendations

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.