M-130 Driver Review (with 1/24 oct. graphs)

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Ashun

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M-130 Driver Review (with 1/24 oct. graphs)
« on: 12 Nov 2004, 07:37 am »
Actually, this'll be a review of a two-way speaker, which uses the M-130 driver, and a subwoofer; both of which were cobbled together in such a manner that I am grateful that I don't have a camera, which would oblige me to provide pictures.

Included are 1/24 octave frequency response measurements from SmaartLive, recorded with a Behringer ECM 8000 microphone and brought to line-level with an M-Audio AudioBuddy pre-amp.

I'll get straight to the components.


The monitors are a two-way, ported design, using the M-130 driver and a Vifa TC20TD05-06 3/4" tweeter, enclosed in a 15.6 liter box, and crossed at 3kHz with a fourth-order Linkwitz-Riley crossover.  I also purchased a GR-T1 tweeter, but I couldn't hear a difference between it and the Vifa, and the latter was more attractive.

A 200 liter box contains the 15" Dayton Quatro subwoofer, a Parts Express 250 watt plate amp, and a port so small, it might as well be Pluto orbiting the Sunwoofer.

Both are driven by a Pioneer VSX-305, with the computer as the main source.

And the test results?

Left Speaker
http://home.comcast.net/~ashun/leftspeaker.jpg">

Right Speaker
http://home.comcast.net/~ashun/rightspeaker.jpg">

Subwoofer
http://home.comcast.net/~ashun/subwoofer.jpg">

The monitors are better than I imagined.  Much, much better.  The subwoofer is appreciated, and in fact, the response looks pretty much like the measurement provided by the manufacturer (I had a different idea of how it would turn out), but it has problems that are mostly my fault.

The desire to build my own speakers hinged completely on the ability to find a suitable mid-range driver.  All I had read indicated that the mid-range was of huge importance and predicated the final sound of the speaker.  Could I not find a reasonably priced, accurate driver, I would have abandoned the project and looked into more expensive options like active studio monitors.  I completed an exhaustive search and found contenders like Vifa and Scan-Speak to be too inefficient or too expensive.

I no longer remember how I came across the GR-Research Web site, but it was very fortunate that I did.  The A/V-1 kit seemed to be very well respected, and specifically, the M-130 driver looked fantastic.  I ordered just one; I had little idea at this point how to build speakers or use power tools, so I was conservative.  I received it promptly and set off to build one disastrous speaker box after the next.  After a few weeks, I had something that had six sides and four corners, which satisfied me thoroughly.  I ordered another M-130.

The Vifa tweeter was chosen because of an exceptionally flat frequency response and very good off-axis response, good price, and attractive faceplate.

The combination of drivers, plus a little help from WinISD, produces a speaker that sounds better than any I have heard.  Two small peaks and one depression are the only things that mar the amazingly flat frequency response.  I'm uncertain how to measure distortion, but at my listening position, I'm less than a meter away from each speaker, so I don't push the volume.  I spilled water on one of the M-130s, which despite dissolving something on the surface of the driver, doesn't seem to have affected the sound.  The performance of the tweeter is just as advertised.  I am extremely pleased with the speakers, especially considering the money I didn't spend on name brands.

If someone as incompetent as myself can manage such good sound, one can image what someone who knew what he was doing could do.  There's nothing fancy about these speakers; I used a circular saw to cut the MDF and a jig saw for driver cutouts and sanded the resulting disaster until everything I own was covered in MDF dust.  I used the cheapest Radio Shack capacitors and inductors, and I never actually got around to soldering the crossover components together!  They're just twisted!

All the above holds true for the subwoofer as well, but in this instance I wasn't able to come away unscathed.  The first mistake I made was making a 200 liter box with no bracing at all!  That's 31.5" wide x 24" high x 20.5" deep, completely unbraced!  So when the panels are vibrating out of control, the plate amp on the back has little choice but to join in and rattle at certain frequencies.  The second is the microscopic port I mentioned earlier.  The air velocity is so high during loud passages, I'm afraid the subwoofer will take off.  Also, because I could fit myself comfortably inside it, placement options are limited in my small room.

I'm not entirely dissatisfied with it, though.  Because it's enormous, it looks very imposing in a 10' x 11' room.  And it does play loud and deep enough to blend well with the monitors.  The annoyances I listed above are minor, and usually display themselves only when I turn the volume dial to 'stupid loud,' which isn't often.  I'll know better next time!

So what about my listening position?

Satellites and Subwoofer
http://home.comcast.net/~ashun/listeningposition.jpg">

Here things start to get a little tumultuous, and the bass looks alarmingly out of proportion.  I didn't expect a perfectly flat frequency response at the listening position, but it still sounds terrific.  I have each speaker thirty degrees from the center, which creates an amazing phantom image.  Pans are seamless.  I purposely elevated the subwoofer level in an attempt to provide the tactile experience that wasn't there with the subwoofer level in parity with the rest of the spectrum.

I haven't noticed the sound change since I've had the speakers (I didn't have measurement equipment when I first received the drivers), nor have I noticed a difference between the two M-130 drivers, one of which endured a few weeks of use before the other was ordered; the current measurements seem to confirm this.

My next project is to acquire some decent tools, perhaps a table saw and router, and develop some woodworking ability.  Then, maybe, I might look into veneer.  Conceivably I'll also solder my crossover components!

For now, though, I'm enjoying the sound I've got.