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The birth of a 15 inch woofer
The birth of a 15 inch woofer
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Old 23rd August 2019, 04:43 AM   #1
Snickers-is is offline Snickers-is  Norway
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Default The birth of a 15 inch woofer

I have worked for a while on designing drivers now and I wanted to make something I would really love to have in my own system. After a bit of considerations, I found out that the basic requirements should be as follows:

- T/S-parameters that fits a 150 liter vented box with 24Hz tuning.
- X-max (real x-max) in the 10-12mm range.
- 15 inch paper cone and paper dustcap with F0-1000Hz operating range.
- Roll off that fits a typical room response (-3dB @ 50-60Hz and -6dB @ 30-35Hz).

So we ended up with a set of parameters that looks quite interesting. A buddy of mine tested them and commented that they gave the same sensitivity and response as the TAD TL1601b in the same box. So even though the parameters are slightly different, it will basically deliver the same frequency response as the TAD, and therefore could work as a replacement for it.

Here are the parameters for those who are interested:

Click the image to open in full size.

Note the Re of 31,7 ohms. Yes, that is in fact not a typo. This unit has a double gap and double coil design, and the two coils are connected to separate terminals. Connected in parallell, they produce just shy of 8 ohms. In series, well, you can have the coils in parallell and run 8 in parallell on a typical amp.
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Old 23rd August 2019, 05:40 AM   #2
kevinkr is offline kevinkr  United States
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The birth of a 15 inch woofer
Interesting, subscribed. Are you going to make prototypes and test?

Seems like these might also be of interest to the HE crowd for use in vented boxes and horns.
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Old 23rd August 2019, 06:02 AM   #3
Snickers-is is offline Snickers-is  Norway
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Quote:
Originally Posted by kevinkr View Post
Interesting, subscribed. Are you going to make prototypes and test?

Seems like these might also be of interest to the HE crowd for use in vented boxes and horns.
Yes, that's the plan.

Who are the HE crowd? High efficiency?

The efficiency of this is around 95dB half space in the pass band. But since the box volume and tuning is given, some might have guessed that already...
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Old 23rd August 2019, 07:43 AM   #4
JMFahey is offline JMFahey  Argentina
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Cool looking parameters.

Do you already have a physical design for it?
A blueprint to give it a name?
Already know winding length , 20-24mm longer than top plate thickness, whatever it is.

Will you manufacture it yourself or send plans to a speaker manufacturer?
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Old 23rd August 2019, 08:23 AM   #5
chris661 is offline chris661  United Kingdom
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Sounds interesting. Will it really stand 1KW long-term?
I've been thinking about aiming for more low-frequency extension for my PA system, and this looks promising.

Chris
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Old 23rd August 2019, 08:41 AM   #6
phase_accurate is online now phase_accurate
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That would indeed be a nice woofer. Especially if it wouldn't cost as much as a TAD. There are not many 15" like the TADs available anymore, compared to the eighties when there were lots of woofers like that available from Fostex and Coral etc. But do you really want to bulid a monster sub-driver with that much of x-max and Pmax when you want to design a TAD equivalent ?

Regards

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Old 23rd August 2019, 08:51 AM   #7
Zvu is offline Zvu  Serbia
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Beyma 15K200 had almost exactly parameters from first post, disregarding Re and Bl of course. Low Fs, low Qts, High Vas, High Qms and Mms around 105gr, very similar Cms. Even a little better than proposed here me thinks. I listened TAD1601 and 15K200 and there is nothing between them actually, in terms of perceived sound quality.
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Old 23rd August 2019, 11:14 AM   #8
Lojzek is offline Lojzek  Croatia
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Only the voice coil wires can easily weigh 70g. Will 40g be enough for the other moving parts?
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Old 23rd August 2019, 12:12 PM   #9
Sabbelbacke is offline Sabbelbacke  Germany
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10-12mm real xmax is not easy to find on big subwoofers - but those have far more heavy cones than your model above...

24 Hz Tuning =! Roll off -6dB 30 to 35 Hz
In 150l, you will still need a very long port to get this low tuning - it will take a lot of volumen, so you have to give it little Port area, which is counter productive. Port area of 300 gives around 25 liters...

Put your driver in hornresp, you will see what is happening.
Also, max spl is not that great, even with this much xmax (which should be hard to achieve with this light cone...).

You could check for the Monacor SPH-390TC, which has a lot of xmax, low tuning... (I even have two of these here), but also more mms (which is unavoidable, in my oppinion).

BMS manages to get the cones pretty light compared to other high-excursion woofers from b&C, 18S, etc.... So take a look at the 15n850 (which I happen to have, too...) - I suppose the 150l will be a little to much for it...

Otherwise - these type os speakers were more common many years ago - but with much less xmax than you want...
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Old 23rd August 2019, 01:36 PM   #10
Snickers-is is offline Snickers-is  Norway
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Quote:
Originally Posted by JMFahey View Post
Cool looking parameters.

Do you already have a physical design for it?
A blueprint to give it a name?
Already know winding length , 20-24mm longer than top plate thickness, whatever it is.

Will you manufacture it yourself or send plans to a speaker manufacturer?
Yes, I have a design for it. The frame, cone, dustcap etc are all picked out.

Click the image to open in full size.

I have no idea what to call it yet.

The coil will be about 28mm longer than the pole plates, and the pole plates will be relatively thin to achieve saturation. This kind of motor typically produces tons of even order harmonics, so therefore I went for a symmetrical motor.

This will be manufactured somewhere, probably in China or Italy.
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