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MartinLogan Purity Floor-standing Electrostatic Hybrid Speakers A Secrets Speaker Review |
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| Written by John E. Johnson, Jr. | |||||
| Thursday, 14 February 2008 | |||||
Page 3 of 3
On the Bench THD+N measurements were within an 80 kHz bandwidth. I set the SPL to 97 dB instead of 100 dB that I use for conventional speakers because half the sound is coming out of the rear in an ESL. I used the RCA line-level input for the measurements, rather than a power amplifier into the speaker binding posts. I did not measure the impedance/phase because the speaker binding posts are connected to the built-in power amplifier. At 1 kHz, THD+N was 1.36%.
At 10 kHz, distortion was lower, at 0.24%.
THD+N vs. Frequency showed that the Purity's have more distortion at the lower frequencies, like all speakers. The crossover is at 450 Hz, and there is a spike just above that, probably due to the crossover network. At 1 kHz and above, distortion stays generally at or below 0.5%. Undoubtedly you are surprised at the amount of distortion in the bass frequencies. We are the first consumer A/V magazine to publish graphs of THD+N vs. Frequency for speakers across the entire audible spectrum, and I believe we are going to find, as we measure more speakers, that there is more distortion than we thought there would be. I suspect also that we may be less sensitive to distortion in speakers than we imagine. We might be more sensitive to distortion in amplifiers because the negative feedback that is often used tends to increase the amount of upper harmonics, whereas in speakers, the upper harmonics tend to have a relatively low value. Upper harmonics are very irritating to the ears.
The measured Frequency Response shows why I felt there was a little too much bass. You can see a bass hump regardless of whether the microphone was at 1 foot or 1 meter (I took the measurement with the bass toggle at the zero position). In general, the FR was pretty flat out to 20 kHz. If you use these with an SSP or receiver, I would suggest setting a low frequency crossover to a nice subwoofer at around 60 Hz. In any case, a subwoofer will help with the lowest octave.
Conclusions At a price of less than $3K/pair for the MartinLogan Purity hybrid ESL/Cone speakers, you can have the kind of detail you won't usually find with conventional midrange drivers and tweeters. ESLs are not for everyone, but even if you are not the adventurous type, you should at least hear them for yourself and then make up your mind. While you're at it, listen to the full range models too.
Comments (26)
 Distortion Measurements etc.
written by EMA , February 15, 2008 I commend actual data measurements(distortion) on the speakers as of late. It would seem a double edge I was wondering if you could comment on the difference in presentation between the Usher Be-718 and the Martin Logan. Seems like the Martin Logan had higher distortion in the 500Hz to 1k region. Was this audible as smearing? Also the Margin Logan response had some anamolies between 200 to 500Hz (a big 20db dip). Was this audible? In other words, is there a correlation to the measurements? it sounds good?
written by Henry Grossbard , February 15, 2008 Without comparisons to other specific speakers, the review is just a Stereo Review type "it sounds good". A review without a reference point has very little value. ...
written by JEJ , February 15, 2008 What kind of a reference point do you want? The hundreds of other speakers I have listened to? It sounds good like many of those other speakers sounded good, not as good as some, and better than others. This is all subjective of course. That is why I do the bench tests, which are objective. These speakers gave me pleasure. That statement is also subjective. What sounds "good" to me does not necessarily sound "good" to any other particular person. ...
written by JEJ , February 15, 2008 The Usher Be-718s are also very excellent speakers, but the sound was quite different. The Ushers are more focused, because the sound is coming from a smaller area and they are monopoles, not dipoles (the sound is only coming out of the front). I didn't hear any unusual sound that I could attribute to the peak above the crossover point. If I played single sine waves at, say, 700 Hz with the two speakers, I might hear a difference, might not. Like I mentioned, I think our ears are more forgiving of speaker distortion than we have imagined. ...
written by JEJ , February 15, 2008 It is difficult to say what the anomaly at 280 Hz is, because that is a frequency handled by the woofers. It could be some cancellation between the sound coming out of the front and the sound coming out of the port on the rear. It may also simply be a room mode. Even though I have treated my lab heavily with absorption panels, it certainly is not perfect. Great comeback
written by No Strings , February 15, 2008 I loved JEJ's answer to Henry. Now that's the no-nonsense approach we like about Secret's. Of course ones impressions are subjective; so many actually do not understand this. I love the presentation Martin Logan's make; but I also love many other designs. Testing is the only accurate way to find out what's going on with a loudspeaker. Keep up the terrific work. ...
written by JEJ , February 15, 2008 Yes, I think we all enjoy many different types of "sounds" that various products have. Velodyne at one time marketed their servo feedback woofers for cars. They had compensating circuits for the motion of the car. The product failed because most consumers appear to like all the distortion that big car subs have, and the Velodyne car subwoofers had so little distortion, they could not hear the music some of the time. That boom, boom sound that you can hear from a car down at the other end of the street. Probably at least 20% THD. That distortion sounds "good" to those consumers. That is why we can only really just basically say we either like the product or not. For me, the bench tests are absolutely critical, because they are totally objective and are reproducible in other labs, which is one of the foundations of the scientific process. ...
written by HG , February 16, 2008 Previous efforts by M-L at this design have always had a problem of intregrating the ESL panel with the cone cone mid/woofers. No mention that I can see in the article mentions the quality of this crossover. For those of us who are ESL fans this crossover problem has been a real weakness of this design. What is your subjective opinion? Great review....
written by Tom , February 17, 2008 I enjoyed this... Tom D'Acquisto MartinLogan Club www.martinloganowners.com ...
written by JEJ , February 17, 2008 One other possibility for the 280 Hz dip is cancellation due to that frequency arriving from the two woofers to the calibrated microphone at slightly different angles. As to the integration of the ESL panel with the woofers, it is very, very difficult to do because of the dipole nature of the panel vs. the monopole nature of the woofers. It's a totally different kind of sound coming from one vs. the other. ...
written by Jesse S , February 19, 2008 The dip at 280 is a room mode. If the speaker was deficient, the curve would be the same at 1 foot and 1 meter (which it isn't). This just illustrates how significant the room is on sound and how important acoustic treatments are. McIntosh MC 2600
written by JFP , February 24, 2008 I new to ESL speakers. Any idea how this speaker would work with a McIntosh MC 2600 power amp pushing 600 WPC? ...
written by JEJ , February 25, 2008 McIntosh power amplifiers are ideal for ESLs because (1) they have so much power, and (2) they have output transformer taps for low impedance speakers. If you get a full range ESL, these factors will become more important. competitors
written by Mark , February 27, 2008 I love your reviews, mainly because of the raw data in the benchmarks, not just a bunch of music reviews and thats it. Please keep it up! How would these compare to those Onix Strata Minis you reviewed a year ago? They seem comparable in price after you allocate the extra $1000 or so towards an amp for the Strata. The ML uses electrostatic technology while the Strata uses planar-magnetic. Great Review. A word about hearing & testing.
written by CWNYC , February 28, 2008 Great review as always. Your reviews always provide a good balance between objective data and personal subjective impressions. Too many "audiophile" equipment reviews out there tend to indulge in poetic yet capricious descriptions of equipment performance, such as "the tweeter sounds like butter..." What does that even mean??? Or even more ridiculous, many reviewers claim to have super human hearing ability, such as reporting that they can detect increased distortion levels at 20khz... I know one such person, who owns many expensive pieces of high end audio gear, visited an audiologist as a request from his ENT physician due to a sinus condition, only to find out that he cannot even hear anything above 12khz... Besides, how sound is produced interacts a lot with the listening environment before the pressure wave reach one's ears, and then there is the element of psychoacoustic, and finally, acoustic memory. Subjective descriptions may ellicit poetic imagination in the readers, but that is just it, imagination and not real word objective performance... I do have one suggestion for your reviews. I see that you informed another reader in another review that you do not perform these measurement tests under anechoic conditions, and with good reasons unless one is well funded by a research lab... However, it would be helpful to see more closed mike response measurements taken off axis from the tweeter, both horizontally and vertically. Furthermore, the response measurements taken 1 meter from the speaker would be more meaningful if there are test graphs showing the room mode/modal pressure variations and speaker boundry interferences. Better yet, if the testing room is constant (hopefully it is), all response graphs taken 1 meter away from the speakers can be adjusted with the known notches and bumps present in the testing environment (which I suspect you may already have done as I do not seen to see any floor relction notch)... The above mentioned additional information would be appreciated, as the extra pieces of objective findings can further help your readers to come to a closer prediction of a tested speaker's actual sound signature. In any case, great reviews! Strata Mini Comparison
written by Chris , March 01, 2008 I too would love to hear a comparison to the Strata Mini. The Mini, and the Martin Logan Source (Purity is out of my price range I think) are the two speakers I'd love to listen to and pick up now, and I heard the Mini once at an AV123 GTG last summer, but would like to hear how the two brands compare from someone that has listened to both extensively. ...
written by JEJ , March 01, 2008 My test lab is not constant, unfortunately, because there is a continuous flow of new equipment coming in and going out. There are various components sitting in different spots on any one occasion. Although I do put the speakers in the same spot when measuring, they are of different height and some of the tweeters are at a slanted angle. So, I could not trust a standard room filter. I wish I could. I will probably add a 2 meter measurement to go with the 1 foot and 1 meter graphs in future reviews though. ...
written by JEJ , March 01, 2008 The Strata Mini's have a slightly brighter high end, and deeper bass because of the large powered woofer. ESL DIY'er
written by Roy , April 08, 2008 I've been a big fan of and builder of esl's for many years... For me, the ML-Purity's are a blessing and way overdue. I hope to see more "evolutions" to esl speakers... Were the speakers broken in?
written by Xavierwalls , April 17, 2008 According to ML those Purity's have to be broken in for 72hours. Would this impact or change your benchmark results? ...
written by JEJ , April 17, 2008 The Purity's were already broken in when I got them, but I always let speakers play for a few days with white noise at about 80 dB before I do the critical listening and bench tests. ESL and Size
written by IP , May 01, 2008 "because they had to be very big in order to produce sound at all frequencies." True to some extent. How would you compare the general performance of Quad's ESL to ML while the size is significantly different? With small size it still covers more frequencies. Cheers puritys internal amps
written by Tastech , May 10, 2008 HI Maybe i missed it but did you comment on the how the internal amps sounded on the ML purity's. I recently heard a demo of the puritys powered by 200w Class A xindacs, they certainly sounded special. But i was being told that the internal amps were up to it. Purity vs Source
written by Bob F , September 27, 2008 Thanks for the review and comments. I understand the internal power and woofer differences between the Source and Purity, can you help me with the difference in sound. I intend on using in a 5.1 set up with a sub woofer and the Matinee center. Possibly Definitive Technology surrounds. Are the Purities worth the extra $? If I choose the Purity can I save on the amp/pre amp set up? ...
written by JEJ , September 27, 2008 The bigger the ESL panel, the louder it will be able to play. Hybrids have cone woofers and the larger ESLs will have larger woofers. Transparency and detail are the same regardless of the ESL size, but smaller ESls cannot play as loud. The membrane only can move a small distance. If you have ESLs in the front, using cone-type speakers in the rear will produce a change in tonality between the front and rear. Better to use ESLs all the way around. Put larger ones in the front and smaller ones in the rear. source
written by alberto , November 08, 2008 i'm still not sure i understand the advantage of having a built in amplifier...does that mean that i can hook it up directly to my yamaha receiver and not worry about driving the speakers? thanks Write comment
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