MCM Aluminum Cone Woofer for TL ? - diyAudio
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Old 23rd November 2007, 07:50 AM   #1
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Default MCM Aluminum Cone Woofer for TL ?

Good Evening, and Happy Thanksgiving to all.

Recently my brother ordered a quantity of these MCM Electronics http://www.mcminone.com (order # 55-1862) a fully shielded, aluminum cone 6-1/2" High-Excursion MCM drivers with rubber surrounds for a decent, dirt cheap quantity price, and they looked interesting, so I agreed to purchase 3 from him, in anticipation of building a voice timbre matched triad for Home Theater use. They also resemble a similiar product sold through Parts Express in thier Dayton line, but in a 7" non-shielded version. He also agreed to furnish to me, free of charge, 3 spare Audax AWO1OE1 3/8 shielded Polymer Dome tweeters he has, to my avail for the asking.


Since I first heard Transmission Line Designs, whether home-built DIY, commercial offerings, such a Vandersteen, KEF as well as others I instantly fell in love with the sound. I began studying on the subject, and became interested in labyrinths, stuffed pipes, Voigt pipes and the like. A few years ago I assisted my brother (an audiophile, as well and an autosound/ car electronics retailer) in building a simple, low-cost, tall, narrow, column tower modeled around a cheap, Pioneer 6-1/2" poly woofer and simple crossover network with a Motorola Radiant Piezo Tweeter. (One feature I did not care for) I liked the tall, narrow, modern contemporary appearance. We decided to try this project in anticipation, based on the promise of unusual bass response from a small 6-1/2" woofer. This design he decided to copy verbatim to stay in keeping with the low cost project's budget and was primarily duplicated for experimental reasons, as we were both curious to see what it would do. It exceeded our expectations. My brother uses these in his home. It can be seen in the publication, "The Great Stereo Sound Speaker Manual with Projects," by David Weems. Another variation of this speaker in a similiar design can be seen at the following link

http://members.tripod.com/oakleyspeakers/MAIN.html

My understanding is, though, that these designs are dated, TL design in the past was more accidental luck, with no clearly defined parameters, and I have recently been informed of recent breakthroughs regarding accurate data for calculated modeling design with absolutes by a person named Martin J King.

Based on various information abound, (both past and present)regarding TL theory, as well as opinions of TL advocates who make powerful claims and arguments regarding the natural, uncolored sound, spatial depth and ability for a woofer to achieve bass down to it's free air frequency. Most feel the sound is less cramped, goes down lower, natural, deeper and they value the purity of the bass, particularly in the upper and middle bass frequencies. I believe this, not only based on thier claims, but on my own experience, which is limited.

I would really like to build a main pair and matching center channel around these magnetically shielded drivers, for home theater use, in a simple, 2-way design similiar to the above mentioned projects. I also have plans to incorporate a "Glass-over" (using ordinary, Dyna-Glass used for fiberglass automotive body repair) into the build any design I am able to come up with to give the sculpted, rounded, aesthetic appearance similiar to the "Rosinante" cabinets sold by Zalytron for a small fortune. This is probably taxing work, but I am far more capable of building any cabinets this elaborate than I am at designing and modeling. (Especially Transmission Lines.) The extent of my DIY experience is calculating Thiele/Small parameters to achieve box volumes to obtain a desired Q for ordinary Acoustic Suspension sealed boxes. (I have always preferred Q's of about 0.6-0.7.)

If anyone out there has any suggestions, or even a proven build design modeled around this woofer, I'd be extremely interested in hearing about it. I would like to build something better than a simple, small sealed or ported bass reflex design. I'd like to build something similiar, in a proven design, in resemblance to the towers I've mentioned here that maximizes the woofer's potential.

I greatly admire those of you with expertise and value your experience and opinions tremendously. Any guidance, direction or designs you might be able to provide would be greatly appreciated.
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Old 23rd November 2007, 11:27 AM   #2
sreten is offline sreten  United Kingdom
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http://www.mcminone.com/content/Prod...ts/55-1862.pdf

Hi,

I'd suggest the 88dB/W sensitivity figure is pure BS.
You will need two for decent sensitivity albeit at 4 ohms.
If you use one driver sensitivity will be very low, but good bass.
Low Vas also suggests 2 drivers for a floorstander.

See http://www.zaphaudio.com/6.5test/
for info on similar Dayton and MCM drivers.

3/8" poly domes are a complete non-starter.

See http://www.zaphaudio.com/BAMTM.html
for how to use the Dayton drivers.

TBH you could do a lot worse than using this as your starting point.

Something similar to :

http://www.seas.no/images/stories/di...t/thor_cab.pdf

Should work OK using info from :

http://www.quarter-wave.com/Theory/Alignment_Tables.pdf

/sreten.


http://www.rjbaudio.com/Audiofiles/FRDtools.html
http://www.geocities.com/woove99/Spkrbldg/

http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm
http://www.humblehomemadehifi.com/
http://www.rjbaudio.com/projects.html
http://www.zaphaudio.com/
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Old 24th November 2007, 04:50 PM   #3
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Hi. Thanks for your reply. I have already seen the info on Zaphaudio.com regarding this woofer. I also was in quarter-wave.com and found it confusing. Supposedly, there's a worksheet that you use by entering a woofer's given specifications, that calculates a box volume and length for a long, tapered line, a short fat box, etc. I had a friend, whjo is more familiar with the website run a model of this woofer, and he seems to think there are better choices for a woofer. He modeled the MCM woofer in different configurations, using MathCad, the program of Martin J King, and did not seem to think it looked promising. Although, he also modeled the very similiar Dayton 7" aluminum cone woofer, which he seemed to really like the results.

I am considering the possibility of purchasing 2 of the Dayton drivers, which he feels match a profile for a more promising candidate for a TL driver. Then, using the 3 remaining MCM drivers for a timbre voice matched acoustic suspension center channel and surround pair.

Any thoughts or opinions ? Thank You.
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Old 24th November 2007, 11:54 PM   #4
peter_m is offline peter_m  Canada
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the MCM driver can't be a "high excursion" at 3mm ???
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Old 25th November 2007, 05:25 AM   #5
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these woofers are cheap, but need to be crossed over low, they require expensive tweeters and crossovers. IMO not worth it.
you can try to use full range drivers if you have limited budget.
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Old 25th November 2007, 07:57 PM   #6
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Default Which Drivers?- The MCM or the Dayton ones?

Which drivers are we suggesting are cheap, too in low Xmax to be utilized in a TL application? The MCM 6.5" shielded units, or the Dayton 7" woofers? The woofers I am currently working with, are the Dayton DA 175-8. My friend, who is working the MathCad program seems to think these drivers are very promising in a mass loaded TL design he is working on. Here are the specs for this driver:

Voice coil diameter: 1-3/8" Le: 1.15mH

Impedance: Re 5.9 ohms Freq Range: 35Hz-10KHz

Fs: 36Hz SPL: 85dB Vas: 0.75 cu ft

Qms: 2.15 Qes: 0.53 Qts: 0.42 Xmax: 4.25mm

We recently had a discussion, and arrived at the decision to try the Dayton driver, which he felt modeled well with MathCad, So I decided to purchase a pair of those to build a main pair to match the MCM drivers, which I will use for both a center channel and pair of surrounds.

Opinions ? Other input on this project ? Please tell me what you think.

Thank You, Eric
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Old 25th November 2007, 09:41 PM   #7
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both, mcm and da175 are cheap, they don't play loud, begin distort too early. it's just my opinion(I have da175's), maybe you'll like these drivers. I liked them at first
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Old 25th November 2007, 11:01 PM   #8
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Default Cheap Drivers ???

Do we mean "Cheap," as in inexpensive, or "cheap," as in poor quality. I know zaphaudio says otherwise. http://www.zaphaudio.com
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Old 25th November 2007, 11:14 PM   #9
peter_m is offline peter_m  Canada
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Zaph uses them in a MTM where you have two of them to help with the DA-175's limitations. But I'm pretty confident that it's better then the MCM.
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Old 26th November 2007, 01:25 AM   #10
TerryO is offline TerryO  United States
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Default Re: Cheap Drivers ???

Quote:
Originally posted by NepaEric
Do we mean "Cheap," as in inexpensive, or "cheap," as in poor quality. I know zaphaudio says otherwise. http://www.zaphaudio.com
Cheap as in inexpensive. MCM has been selling tons of these Aluminum drivers for more than a decade. I don't know too many experienced speaker builders that haven't done a speaker design using them sometime in the past. They aren't the ultimate driver, but they look nice and are fairly forgiving for metal cone drivers. In the real world their power handling ability is fine for most home environments. Remember, that for most people, including me, they're a good driver start out with and can give very satisfactory results.

Usually, expensive drivers use exotic materials, have excellent power handling ability, cast baskets, greater x-max, blah, blah blah....

The question is, do they sound better? That tends to be a sticky question, as it really depends on what you're looking for. There are many "cheap" drivers that sound just fine within their design limits, and in fact may sound just as good or better than the exotics, if used in a "normal" situation. Lots of experienced designers like paper cones, for instance, and cost has absolutely nothing to do with that preference.

My advice is to just use them and enjoy the results, this is supposed to be fun, not a form of self inflicted neurosis.

Best Regards,
TerryO
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