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January 11, 2009 / consort3

W6-1139 & TM1A compact 3 way design

callipThe Tangband W6-1139 interested me as it has a very good Xmax (excursion) figure and was available for a reasonable price (till the pound went down) from Lautsprecher shop.  Since it is basically designed as a sub-woofer it has a limited high frequency response.  Thus a driver was required to fill in the middle frequencies. The idea being to use it with the Hi-Vi TM1A available   from IPL. Its price too has gone up unfortunately.  Two  tweeters,  a large and small dome are combined on the same plate.  By turning this through 90 degrees a very compact 3 way design is possible. Initially  I was going to do an active design but I have started to get in to passive crossover design,  so tried a passive design.  Of course things were not straightforward. I found  the TM1A large dome had a 6dB dip in the response at 3.5KHz. I had been going to make the second crossover frequency about 5.5Khz but used the natural roll off of the large dome to make the frequency 3.5kHz.

I also used the natural roll-off of the woofer so the lower crossover frequency is 1.5Khz. Thus the mid only has to handle 1 octave. There appears to be virtually no designs on the internet using the TM1A.  The nearest I got was the Bellaria from this site http://www.rob-elder.com/LouC/speakers/sm3way/SM3.htm which used a variety of the TM1A mid-range. Since the bass driver is insensitive, the speaker needs a reasonably powerful amplifier to drive it to it full capability. As Richard Small points out; there is a trade-off between sensitivity, bass extension and box volume and here we have traded the last two for the first. This is commonly referred to as Hoffmans iron law. The enclosure is 216wX321hX265d (all miilimetres) As well as turning the TM1A through 90 degrees I had to cut material off the flange to fit it.  The crossover looks expensive but by using Rapid electronics UK as a supplier of components  it is a reasonable price.

In the above schematic LS1 is the W6-1139 Ls2 is the the TM1A mid and LS3 is the TM1A tweeter. The diagram is not too clear, R1,R3and R4 are 10ohm and L2 is 0.5mH. The bass tuning is more or less as Roman Bednarek’s project here (except that I use a 2in port tube):

http://www.rjbaudio.com/Cerberus/cerberus.html

Note that the w6-1139 driver used is the SH variant which has two 4ohm voice coils (in series in this design) which is yet another variant because it is not mentioned in Roman’s write-up. The port tube would be about 40cm long. How to fit it in? Literally by thinking outside the box.  So the speaker stand is hollow and doubles as an external port tube. A ferrite version of the 1139 is avaliable :

http://www.tb-speaker.com/detail/0624_11/w6-1139sif.htm

The earlier TM1 had chambers, they have taken the chambers off the back now, a backward step in my view.

Update:  I see from the Partsexpress forum that Wolf is going to do a design using the TM1A It will be interesting to see what he comes up with.

http://techtalk.parts-express.com/showthread.php?t=210877

More explanation on the blog here:

http://techtalk.parts-express.com/blog.php?b=168

I found that the mid had the ‘closed in’ sound originally noted by Wolf but I have not tried the LCR notch filter to notch out its resonance. The other thing would be to take the back off and make a bigger chamber.

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2 Comments

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  1. Michael Hofmann / Nov 2 2009 9:24 pm

    This is almost everything.

    • Peter / Sep 28 2014 11:56 am

      Hello, I just finished yesterday my 3way speaker design with the TM1A. Unexpected really good result for ~250$ per box. Closed design, 35l, Scanspeak 26W4534G00 used as woofer. Crossover 800/4500 Hz. I will try to publish a complete set of all design data including measurements on the web. Contact me If you need some details in advance.

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