Eminent Technology LFT-8c Robert Greene review

It’s such a shame that so few people venture away from the far-better known Magnepans, ignoring the Eminent Technology LFT-8b/c (your choice), the best value(s) in a dipole/planar loudspeaker for over 35 years! While both are planar-magnetic designs, they sound quite different from one another. While I’m sure I could be happy with a pair of MG3.7i’s (with the Danny Richie-designed GR Research mod), I couldn’t with a pair of 1.7i’s, the LFT-8b’s competition.

Just curious how far away you guys are listening? I am having trouble with the center image. Kind of fuzzy and not very realistic. Side walls are treated with absorption and rear wall (behind speakers) have diffusors. Still experimenting with toe in.

@bdp24 

As I mentioned above, I've made a point to listen to the Maggies in recent audio shows for just this very reason (owning LFTs).  I visit and revisit the rooms..they just sound thin and anemic to me. 

I did notice/hear the Altec Lansing Ribbonacci Reference at Axpona. Wonderful sounding speaker (at about $90K). They are a planar magnetic using a push-pull design. I suppose somewhat similar to the LFTs. If Bruce had any patents on the early LFT models, they've run out by now. I think(?) even Maggie(?) uses a push-pull design on the upper models.(can't remember where I read that). Last month when I was in FL and ordered the 8c upgrade, I asked Bruce if he would be attending the Tampa Audio Show (he's in Tallahassee..not that far away..) and he said..nope, too busy working on stuff. 

@ledoux1238 

For 230cm between speakers on center and at 300cm to listening position, the results are:

On Axis to your head 21 degrees (0.366 rad)

Context (narrower layout)

Compared to your other rooms:

• Speakers are closer together relative to distance
• So:
  • Less toe-in required
  • Slightly less sensitive to lobing shifts
  • More inherently stable imaging

Axes crossing behind your head

Reduce toe-in slightly:

Practical range:

👉 18.5°–20°
👉 0.32–0.35 rad

Axes crossing in front of your head

Increase toe-in beyond 21.0°:

Optimal range:

👉 22.5°–25°
👉 0.39–0.44 rad

OK..with the several recalculations for ledoux1238, I figured there has to be a way to generalize the setup for all room speaker and listening position placements..in essence, as known in my former life, a generalized calibration curve. A benefit to the repeated room calculations (and necessary condition) is they offer the base-data to generate an empirically-derived predictive model.  Not surprisingly, there was a way to do this and it's pretty basic. What was surprising, was that it took ChatGPT about 15-20 seconds to churn it out.  The usual response time is instantaneous or a second or two. While I'm new to the A-i thing, there's some amount of satisfaction in asking a question that takes that long to answer.  The whole curve thing, in hindsight naturally, is quite simple.  Also in hindsight, there's no way I'd have ever taken the time to work this out manually, though it's do-able, as it would have taken (me) waaay to much time. This is a case where humans(supposedly the "smart" ones) ask questions and machines answer them. 

(Forgive my continued flogging of this (setup) dead horse. This is my idea of fun..and something useful to do while listening to music)

First we need to define a Space  Ratio (R) 

R = (on-center speaker spacing) / (listening distance)

R = (spacing) divided by (listening distance)

The chart below can be used to self-check on whether you're using the calibration curve correctly. (locate your unique ratio R on the x axis, go vertically the dotted line, then travel horizontally to the y axis to read your toe-in angle)

Quick mental shortcut (no math) — Behind-head version

You can estimate toe-in instantly:

• Speakers narrower than the listening distance
  → ~18–20°
• About equal spacing and distance
  → ~23–25°
• Speakers wider than listening distance
  → ~25–28°

What the calibration curve really means:

As R increases (wider speakers or closer listening):

• Toe-in increases
• Lobe steering becomes more critical
• Sweet spot gets narrower

As R decreases:

• Toe-in decreases
• System becomes more forgiving
• Imaging stabilizes naturally

I'm having way too much fun with this..