NSMT PSM (Professional Studio Monitor) SE—Acoustic Suspension/Folded Transmission Line Loudspeakers

Discussion in 'Audio Hardware' started by jupiterboy, Jul 3, 2014.

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  1. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    As a few have expressed some interest, and as I am comming to grips with the fact that I really want to keep these, here is some basic information about an odd speaker that could be easily overlooked.

    Formerly NSM, NSMT is a small loudspeaker manufacturer located in Research Triangle Park, North Carolina. The designer is Erol Ricketts. Erol notes, “The company is named after my children. The name was altered a few years ago to accommodate my last child.”

    I became aware of these speakers as I was looking around at used speakers. I noticed the good reviews on other NSM models and then started looking at the design specifications of the PSM, which seemed to check all the boxes on my list of admirable design goals. Erol is particularly proud of his simple, first-order crossovers, which use a single capacitor and a single air-core, perfect-lay inductor.

    PSM-SE Un-Smoothed Anechoic Response
    -10 dB referenced to mid band (1 kHz) response: 28 Hz

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    SPECIFICATIONS:

    Frequency Response: 35 Hz-25 kHz,+/- 3.5 dB
    -6 dB referenced to 1kHz: 30 Hz.
    Sensitivity: 92 dB 1/watt/m
    Minimum Impedance: 4 ohms
    Dimensions: 7.5 X 24 X 16 (W x H x D)
    Cabinet construction: Cross-braced 3/4 inch MDF
    Finish: Semi gloss red birch with semi gloss black front and back panels
    Shipping Weight: 45 pounds each
    Recommended amplifier: 25-200 watts

    Did I mention that these are time and phase coherent? Does it matter? Well, it does matter to me and has been a hallmark of speakers I have responded well to consistently over a long time. In looking at the Dunlavy and newer Lipinski designs, the MTM configuration piqued my interest. Erol’s apporach follows these designs, but without the customary stepped baffle. He doesn’t discuss the finer details of his work, but part of the design is using a tweeter with an acoustic center deeper into the box.

    With regard to time coherency, the speakers are time coherent. Many stepped baffle loudspeakers are not time coherent. We use only a single air core copper coil and a single capacitor (a first-order or zero-order crossover) and unlike most loudspeakers both the tweeter and woofer are wired in the same positive polarity (most designs flip the polarity of the tweeter to gain better coherence). This indicates that the drivers are acoustically matched and the cabinet matches the parameters of the drivers very well. Keep in mind complex crossovers are meant to correct aberrations in the loudspeaker response and that you cannot get a flat frequency response with a first order, positive polarity design unless the drivers are time coherent. You can see there are no major dips in the frequency response curve here (see above). The positive polarity hook-up of drivers preserves the original polarity of the recording microphones.​

    The design features two 6.4 inch custom cast magnesium frame TPX drivers, a one inch soft dome Ferro cooled tweeter, and a folded transmission line ported to the front of the box.

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    Erol doesn’t go cheap on materials, and he meticulously matches all the components that go into his speakers.

    We still match components which is why our loudspeakers image so well and are so good at rendering micro detail. We no longer talk-it-up because it tends to confuse people. But here is an explanation. The idea of stereo is based on the two speakers being identical. That is, stereophonic recordings are based on an assumption that for each pair of speakers, the two speakers are identical --the crossover parts, drivers etc. are the same exact value. In reality, a 5 micro farad capacitor may have a tolerance of plus and minus 3 percent. That means in any batch each capacitor could measure between 4.85 and 5.15 micro farads. They are all 5 micro farad capacitors. And the typical manufacturer will grab two to use in a pair of speaker. In general most of the capacitors will measure 5.0, but he/she may grab one that is 4.85 and one that is 5.5. For two speakers utilizing those two capacitors as crossovers for the tweeter, the tweeter will not crossover at exactly the same frequency and so the speakers will render a signal slightly differently. What we do is to match the 4.85 with a 4.85, a 5.0 with a 5.0, a 5.15 with a 5.15. The critical thing is not that the components vary slightly but that the matching two used in a pair of loudspeakers are exactly the same value.

    Even the binding posts, which look somewhat generic, are a point of pride.

    By the way, the PSM terminals may look generic but they are some of the finest insulated terminals available. They are made by Superior Electric Company in Connecticut.

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    In-room response for the PSM SE measures very much as my Vandersteen 1Bs, however the sound is different. The drivers are very low distortion drivers—the manufacturer is known to produce the lowest distortion drivers available. This, in my opinion, works well with the less severe slope of the first order crossovers. The result is a very well defined soundstage and very detailed imaging with layered depth and width beyond the speakers. The lowest bass, provided by the transmission line, offers a surprisingly well integrated and effective counterpoint to the clarity, transparency and detail of the drivers. The overall effect is very natural and convincing. These are not bright, splashy monitors. They provide a warm and natural presentation that is welcome over long listening sessions.

    I’ll not prattle on about various recordings, although the PSM SEs did pass a battery of tests—a perceptually balanced sweep and an IMD test that has caused some well known, popular speakers to lose composure. The front port plays very nice with my odd room and minimizes issues relating to back-wall proximity. Like Terry London, who reviewed these very speakers previously, I find no reasonable complaints, save that I am now forced to look at the quality of my pressings in a bit harder light.

    I am driving these with an Eastern Electric M88 integrated amplifier, and I find the amp and speakers to be a good match. Looking forward, I feel I have matched the value and performance of the Vandersteens, and added a much more detailed presentation of recordings without killing the musicality and enjoyment. Now that the tubes are warmed up, I think I will go spin some records and kick off the long weekend. For those interested, I have included a link to the previously mentioned Terry London review.

    Terry London review:
    http://hometheaterreview.com/nsmt-loudspeakers-psm-super-monitor-reviewed/

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  2. Metralla

    Metralla Joined Jan 13, 2002

    Location:
    San Jose, CA
    "By the way, the PSM terminals may look generic but they are some of the finest insulated terminals available. They are made by Superior Electric Company in Connecticut."

    Very good binding posts.
     
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  3. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Your Coincident Super Eclipse have the MTM design. How do you like living with them?
     
  4. triple

    triple Forum Resident

    Location:
    Zagreb, Croatia
    I second this. I use them at my amp end, as well as the speaker end. They proved better than Cardas rhodium posts that I used previously. They can be tightened using a cheap Audioquest hex key, unlike those used by Tannoy on the Glenairs.

    These speakers look really good. Well, biwiring aside. Also, I thought that ferro fluid cooled tweeters were superceded by other designs.
     
    Last edited: Jul 4, 2014
  5. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    I may get a run of Luna for the tweeters, IDK. Tweeters are interesting. I can get along with these—some coated fabric. All the drivers are Seas, the mid-woofers being custom. I’ve listened to beryllium and other metal tweeters recently. They are one piece of the design that stays consistent between the base and SE model, so I assume they are integral to making it all work.
     
  6. triple

    triple Forum Resident

    Location:
    Zagreb, Croatia
    92 db efficiency combined with 35 Hz low frequency response is excellent for a standmount speaker. :thumbsup:
     
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  7. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Down 6 db at 30Hz, but it is a cliff after that. I am kinda thinking of them as standmount version of the 1B with the transmission line at the front and the MTM design (and better drivers, as the cost of the raw drivers alone is as much as the retail cost of the 1B). The integration of the drivers is superb, and the detail and soundstage are full on. They are kind of an oddball speaker, and I had always wanted to scale down to a monitor.
     
  8. norman_frappe

    norman_frappe Forum Resident

    What differences do you notice from the vandersteens? More detail?
     
  9. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Yes, loads. Both are two-way, first-order speakers with transmission line, so no surprise that I respond well to them. Where the Vandys use an 8" driver, and a stepped baffle; the PSMs use two smaller drivers. What I like is that the focus in more on the mids, where the music is. I think the dispersion and sweet spot on the PSMs is less specific. The Vandys have about a 6" vertical window. If you stand up, you lose all the high frequency info. The PSMs are more forgiving in this respect, and more involving for everyone in the room. The extra efficiency and the 4 ohm vs. 6.7 ohm rating makes better use of my amp. Having the transmission line fire at the front, rather than the back, also helps when you only have a wall behind one speaker.
     
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  10. Fedot L

    Fedot L Forum Resident

    Exactly. Therefore, according to the graph, the monitor’s FR linearity is very good for 40…20000 Hz (after having equalized the 40…120 Hz band to “0 dB” with a good graphic equalizer). And as in the great majority of cases, to be able to monitor the whole audible range (including infrasonic hum and/or noise, pulse signals (“p” and “b” popping etc.) etc.), the system needs a really linear subwoofer (but not any! There are on the market rare models really linear from 20…22 Hz to 100 Hz, but such ones exist).

    And the final equalization will depend on the interaction of the whole loudspeaker system (including the sub) with the acoustical reaction of the listening room. To visualize by means of a program spectrum analyzer with a measurement microphone placed in the chosen listening place.
     
  11. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    I will not be using a sub or EQ, and therefore do my best with the measurement tools I have, room treatments, and starting with a flat frequency response from my source. I hope to get a mic to work with the REW software, but am still learning about analyzing and using the information I get.
     
  12. Fedot L

    Fedot L Forum Resident

    There is no flat sound frequency response from input sources from electro-acoustical systems in a room without equalization, even in studios’ monitor rooms.
    But it’s your opinion and your choice. Good luck!
     
  13. Jim T

    Jim T Forum Resident

    Location:
    Mars
    The design of these looks very similar to many center channel home theater speakers, and like my Triangle Sextan Center channel. The Sextan is not ported, but does have 2 coated woofers. The matchng Triangle Comets bookself speakers are ported.

    I curious about the time align as the tweeter voice coil is not in line with the two mid/woofers?
     
  14. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    As far as I know he has two options, electronic and physical. I assume part of the custom mids is to bring the acoustic centers for the tweeter and mids into the same plane. What delay could be accomplished with a single cap and inductor is beyond my pay grade.

    This is the guy who started it all, but he had third-order crossovers in mind.

    http://en.wikipedia.org/wiki/Joseph_D'Appolito
     
  15. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Only refering to shaping my cartridge response so it measures flat. No doubt, the room presents it own challenges. As these speakers and my old ones measure very similarly from the listening position, I can only assume that the humps and suckouts are indeed the room. Who knows, maybe I will use an EQ at some point. No opinions, just reality and how to deal with it.
     
  16. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Any quick explanation of placement on thes modes? I don’t have a consistent room width, so various calcs don’t give me much feedback. Width varies from 20 ft to 15 ft to 40 ft.
     
  17. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Some in-room info.

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  18. Kyhl

    Kyhl formerly known

    Location:
    Savage
    You have the tools. Use your RoomEQ Wizard to play a test tone and walk around the room with the mic to find it. It can be at the floor, ceiling, corners, mid wall, quarter wall. Use the mic because it is easier to get a mic near a ceiling corner than to get an ear up there. :D
     
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  19. jupiterboy

    jupiterboy Forum Residue Thread Starter

    Location:
    Buffalo, NY
    Well, ceiling corners are where it gets the loudest. Back wall seems like the best candidate for bouncing sound back into the room and causing phase cancellation. Live and learn. Thanks for the input.
     
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