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Midwoofers from Sony MB-150H

Sample 1

Fs  = 59.16 Hz
Re  = 7.26 ohms[dc]
Le  = 211.55 uH
L2  = 560.53 uH
R2  = 19.06 ohms
Qt  = 0.55
Qes = 0.63
Qms = 4.27
Mms = 9.30 grams
Rms = 0.809374 kg/s
Cms = 0.000778 m/N
Vas = 5.73 liters
Sd= 72.38 cm^2
Bl  = 6.330997 Tm
ETA = 0.18 %
Lp(2.83V/1m) = 85.13 dB

Sample 2

Fs  = 57.50 Hz
Re  = 7.26 ohms[dc]
Le  = 210.13 uH
L2  = 521.34 uH
R2  = 17.65 ohms
Qt  = 0.55
Qes = 0.64
Qms = 4.14
Mms = 9.92 grams
Rms = 0.865260 kg/s
Cms = 0.000772 m/N
Vas = 5.68 liters
Sd= 72.38 cm^2
Bl  = 6.396310 Tm
ETA = 0.16 %
Lp(2.83V/1m) = 84.66 dB

Added Mass Method:
Added mass = 20.00 grams
Diameter= 9.60 cm

Quick box model:

F3/6/10 in a dinky box is 61/48/40. Low Vas + medium Q (Qts is 0.55) = vented enclosure with excellent cone control. See how the excursion flat lines below tuning? If a guy wanted to, say, load a pair in a slim tower they will easily pull F3/6/10 of 51/45/40. Very flexible TS parameters. 

The two samples are reasonably close to one another. 

OK, so these have a very nice molded frame with venting below the spider. A slightly raised spider, and gobs and gobs of throw. Plus, I could not get them to bottom out by pushing - so the soft parts are doing their job. 

The cone is so-called "HOP" material, which Sony claims is an acronym for "Highly Oriented Poleofin" or some shit. Looks and feels like plastic/poly to me. Has a slight texture, is curvilinear, and the dustcap is very soft. Rubber surround with a shiny material added along the edge where it meets the cone. Tap test yields a fairly soft sound, and the lack of wrinkles above 3K in the impedance sweep indicates that the driver has minimal breakup. It appears to be a very well behaved driver, at least on response.

The motor looks bread and butter - but the measured Le is not very high at all, and the impedance swing looks fairly controlled. I suspect the driver was designed to have a lot of "bump" in a small cabinet, and run with a minimal crossover. In fact, the Sony speakers are undersized - I am guessing on the order of 0.15 cubic feet and tuned to 80 Hz. As these drivers are NOS and not pulled from a pair I found, I will never know for sure. I have listened to one pair years ago, so I am basing my estimate of that design on an old experience. 

I digress.

So we have a well built little driver with an excellent cone and an interesting motor. I suspect it is manufactured by Bravox for Sony, but that is only because the frame is similar to a bunch of those Bravox buyouts from years ago. While it ultimately does not matter where they are sourced, it is always fun to speculate. I found these for $25/pr shipped. 

Just FYI - these will be getting used in my AMT monitor rather than the MCM. They model better on the low end.

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  • Interesting - Wonder what the plate on the back is for? You going to do a small MT or the slim tower? 
  • Small Mt. The plate is a partial shielding bucket.
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  • I love how you always seem to find these hidden jems for peanuts!
  • Bought a lot of turds over the years, too lol. These look pretty legit, though. Looking at the speaker it came out of, I would not have been surprised by a 70Hz Fs, Qts around 1.0, and Dayton DS level stamped basket. Very pleasantly surprised. 

    My only concern is the impedance blip around 1200 - that might indicate a shelf in the response. 
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  • Did a further break-in:

    Loudspeaker parameters:

    Fs  = 56.06 Hz
    Re  = 7.26 ohms[dc]
    Le  = 207.04 uH
    L2  = 513.85 uH
    R2  = 17.87 ohms
    Qt  = 0.52
    Qes = 0.60
    Qms = 3.71
    Mms = 9.69 grams
    Rms = 0.919678 kg/s
    Cms = 0.000831 m/N
    Vas = 6.12 liters
    Sd= 72.38 cm^2
    Bl  = 6.407869 Tm
    ETA = 0.17 %
    Lp(2.83V/1m) = 84.87 dB

    Added Mass Method:
    Added mass = 20.00 grams
    Diameter= 9.60 cm

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  • Wow, that is a beautiful driver. Best looking cheap oe driver I’ve seen in a long time. Also a good example of how a very large manufacturer can engineer a driver to work for a particular application with good behavior, excursion control, and probably nothing more than a dinky inductor to overcome bsc as the low pass crossover. 
  • I am heading out if town tomorrow for a funeral, otherwise I was going to get these under the mic.
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  • I assume your Grandpa.  If so I'm sorry JR.
  • Thanks, Craig. 
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  • JR, my condolences to you and your family.
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  • Lookin' good, JR! Let me know what you think of that tweeter. I'm having a hell of a time keeping it from being a little too sibilant in my little NeoWaves, the ND105-4 design.
  • I used it once before, just padded her down a dB or so lower than "flat" and enjoy it.
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  • Those remind me of the old Axon woofers that Zalytron sold.
  • Zalytron... wow.  Are they still around?  I remember looking at their ads in the back of LSDC ver. 1.  Same with Old Colony Sound Labs.  I bought a box design program from them... came on a 3.5" floppy.
  • Nice looking speaker JR!

    Im pretty sure the ads in the back of LSDC is how I found PE, lol
  • PWRRYD said:
    Zalytron... wow.  Are they still around?  I remember looking at their ads in the back of LSDC ver. 1.  Same with Old Colony Sound Labs.  I bought a box design program from them... came on a 3.5" floppy.
    Zalytron is long gone - the site says it hasn't been updated since 2013 and none of the pictures are loading. I always thought it was a strange site. Very dated, even back then. But they did seem to have good prices on drivers. Did anyone else even sell raw Focal drivers?
  • squamishdrocjhollanderS7910JasonPNicholas_23
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  • Yes; PE, Solen, Meniscus, Mad (IIRC), et al all sold Focal drivers; but Zal' was probably the largest seller.
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