The criteria for loudspeaker choices.

@cbrunhaver: You raise some justified issues, and make some excellent points.

The shallow crossover filters employed in the ET LFT-8 (1st-order) are also used by Magnepan in their planar-magnetic loudspeakers (PS Audio’s Paul McGowan’s reference speaker for quite a few years was the MG3.6, which he was very happy with in spite of it’s low-order filters). When Danny Richie of GR Research measured the MG3.7, he found a lot of frequency response irregularities caused by phase cancellations between drivers, a result of the large expanses of driver overlap (inevitable with low-order filters).

The ET LFT-8 (both b and c iterations) employs a 1st-order high-pass crossover frequency of 180Hz for the LFT-8 planar-magnetic midrange driver, so phase cancellation between woofer and midrange driver is not a problem (due to the very long wavelength of 180Hz). What IS a problem is the out-of-band woofer resonance (seen at around 1800Hz in the Stereophile frequency response graph), but that may be eliminated in the LFT-8b by installing a cap onto the woofer, shunting the high end response of the woofer to ground (as detailed in a few posts in the Planar Speaker Asylum forums). That problem is eliminated in the LFT-8c, which has a different (dipole) woofer system. I eliminated the problem by using the Rythmik/GR Research OB/Dipole woofer system in place of the LFT-8b’s stock woofer (easy to do, as the 8b has separate woofer and planar-magnetic driver binding posts), which transforms the LFT-8b into a 100% OB/dipole design.

The criticism of the 1st-order high-pass and low-pass filters located at 10kHz IS quite valid. A 10kHz wavelength is only approximately 1.36" long, so small movements of the listener’s head can result in frequency response changes resulting from phase cancellations between the midrange and tweeter drivers. I’d love the hear the LFT-8 with a lower midrange-to-tweeter x/o frequency, and/or steeper filter values (perhaps 4th-order, as I believe Siegfried Linkwitz employs in his OB/Dipole designs). The phase relationship between tweeter and midrange drivers in the LFT-8 may be adjusted by small changes in loudspeaker toe-in.

I don’t know where the 77-78dB sensitivity figure came from, but it is not accurate (83-84 is more like it). The LFT-8 infact requires significantly less power that do Maggies (I have both). Steve Guttenberg found 50 watts to work pretty well with both the 8b and 8c. And if you bi-amp the speaker, the planar-magnetic driver itself presents an 11 ohm load to the amp, great for tubes

Regardless of all the above, the fact remains that the ET LFT-8 reproduces 180Hz up to 10kHz WITH A SINGLE PUSH-PULL PLANAR-MAGNETIC DRIVER (without a crossover in that frequency band!), resulting in high coherency and transparency, low coloration sound. I better wrap it up here, before I’m once again accused of shilling for Eminent Technology and Bruce Thigpen.

“The criteria for loudspeaker choices” title suggests a general criterias or what each person what they do for evaluation, but the OPs content narrowly emphasizes ET a so seems like shilling/promotion.

The criteria I use along with many/most audiophiles is to “use our ears” to choose loudspeakers.  More specifically I demoed/purchased a neutral linear full range loudspeaker running SS, and a 100db loudspeaker specifically to explore tube magic starting with the flea watt 300b amp.  Future loudspeaker purchases might include MBL omnis (always sound great) to fill in a shared room, MoFi SoucePoint 10 (huge fan of speaker guru Andrew Jones), and Devore Orangutan O/96 (maybe the most musical speaker I’ve demoed).  I’m trying to justify spending for a 3rd system the great matching Harbeth+Hegel.  

There are many good/great sounding loudspeakers, but which loudspeakers  to bring home aka spend significant money on preferences are highly subjective.  

@kennyc: The title of the thread was made in relation to what PS Audio had to say about planar-magnetic drivers, which they choose to employ as tweeters in all their loudspeaker models. In their promotional literature for their speakers, they cite all the ways in which p-m drivers meet their criteria for achieving superior quality reproduction of high frequencies (reread the op to refresh your memory if necessary).

The question I therefore asked was: If planar-magnetic drivers meet PS Audio’s criteria for superior reproduction of high frequencies, why not use a planar-magnetic driver for midrange frequencies as well? There are only a very limited number of loudspeakers employing p-m drivers to reproduce midrange frequencies, one being Eminent Technology. Another is of course Magnepan. I currently own both Magnepan and Eminent Technology models, and because everyone already knows about the former and few do about the latter, I felt compelled to once again bring the ET LFT-8 to everyone’s attention. If that now qualifies as shilling, so be it.

Everyone has their own criteria for choosing a loudspeaker, I posted this thread in response to the criteria stated by PS Audio as the reason for them choosing a p-m tweeter, not as a means of myself making the case for the superiority of planar-magnetic drivers or loudspeakers. I also own ESL’s (QUADS), but didn’t bring them into the discussion as PS Audio doesn’t use ESL drivers, nor make any claims as to their ability to reproduce music.

One listener who DID bring the subject of ESL’s into his review of the ET LFT-8b and 8c is Steve Guttenberg. In his reviews he states that he doesn’t care for the sound ESL’s make, preferring his dipole panel speakers to be of planar-magnetic design. He then goes on to say that he found the sound produced by the two ET models to be superior to that produced by every ESL he has heard, as well as all Magnepan’s he has had in his listening room.

I hope this post makes clear my motive and intent. I did my best to make it so!

I don't put much, if any stock in marketing blurb. PSA was on the cusp of releasing a floor standing speaker, but the showing at Axpona (pre covid) got so little attention that the company threw out that design and started over from scratch. The FR lie is much more of an attention getter than that previous box. This lineup looks like a legitimate investment and effort.

Well, I don’t have an axe to grind against Bruce or any of his products but was just commenting on some of the measurements from stereophile.

In fact, while they are in the same price category, I don’t think it makes sense to compare a large open baffle line array to a small stand mount.

however, i did want to target some of the technical analysis.  As you mentioned above, wavelengths are very small around 8 kHz and a lower crossover point would be beneficial.

regarding the sensitivity, John Atkinson commented that the LFT-VIII was 4.7 db lower than his LS3/5A’s 82.5 dB and to this puts the speaker around 78 db/2.83V

https://www.stereophile.com/content/eminent-technology-lft-viii-loudspeaker

Paul writes our ad copy and the website and it can be a little hyperbolic at times as we’re trying to emphasize the positive attributes of a product.  However, I think the speakers are very competitive performance wise to a lot of big names and have some unique performance attributes.  Our bookshelf speaker in particular is getting great feedback and will be on the cover of the October issue of hifi news and in an upcoming stereophile, I believe.

they men