Tiny 12 litre subwoofer making 15Hz and 600ccm? - Page 3 - diyAudio
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Old 5th January 2004, 09:30 PM   #21
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Hi catapult!
THX for this clarification.
The proposed circuitry seems to be reasonable for me. In fact I "wasted"
one OP amp more to get such a transfer function.....


Cheers
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Old 8th June 2004, 10:16 PM   #22
Pafi is offline Pafi  Hungary
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Hi, ChocoHolic!

I made a similar subwoofer, but a very low cost version. Second hand Magnat 8 coll 150W speaker with 2 coils, 7 l box (resonance about 100 Hz), driven by a 100W amp. Obviously the SPL was not enough unless I stand it into the corner.

I like your design very much! But I think you have too much money! :-)

You inspired me to build it with 7 pieces 6" Sony speaker with 1,5" coils. Xmax is about 6 mm. The amplifier is allready built, matter of fact there is even too much of Class D amp in my... (damn, I dont know the word...)

2 kW @ 2-2,66 ohm bridged, with MOSFETs:
http://www.hszk.bme.hu/~sp215/PWM_2kW/27.jpg

500W @ 4 ohm full bandwidth, 1000W low bandwidth, SE, with IGBTs:
http://www.hszk.bme.hu/~sp215/PWM_500W/311.jpg
http://www.hszk.bme.hu/~sp215/PWM_500W/316.jpg

Both have undestroyable overcurrent protection.

I saw You want to build one. Those Semicron MOSFET modules seems to be too large. If you use XXL MOSFETS, the conducting losses decreased, but switching losses and EMI increased, therefor I think you should compromisem, if you want an optimal solution! Could you write me a link to the datasheet of these MOSFETS? I would compare it to others! Where would you buy them? In hungary It's allmost impossible to buy any special parts.

I think doubled FDP2552 would be perfect to your bridged amp too! Best driver (IMHO): IR2010, best modulation method: DB (3-level PWM).

P.S.: I am chocoholic too! What is your daily dose? :-)
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Old 8th June 2004, 10:31 PM   #23
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I've heard that someone has a patent on subwoofers operating entirely at frequencies below their (unusually high) system resonant frequency. If true, this proves once again that you can patent anything. When did you first design your system? I wonder if it constitutes prior art.

[Added a couple of minutes later] I did a quick google and came up with this: http://ldsg.snippets.org/boxes.php3

It says Bag End makes such a sub. Whether or not they claim patent rights, I do not know. All I know is what I read on the net.
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Old 8th June 2004, 11:28 PM   #24
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http://sunfire.com/TrueSubwooferEQSigPR.htm#featured

http://sound.westhost.com/linkwitz-transform.htm
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Old 9th June 2004, 06:44 AM   #25
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Quote:
It says Bag End makes such a sub. Whether or not they claim patent rights, I do not know. All I know is what I read on the net.
They don't own the ELF patent, they are a licencee. The patent of the ELF belongs to Long and Wickersham (one of them is the owner of Alembic).
It is perfectly possible to make low-end EQs that don't have the restrictions of LT (not possible to make dynamically tuneable) and ELF (intrinsic LPF).

BTW: The thing about "not introducing phase errors" with the ELF is nonsense. The ELF circuit does of course not introduce phase-inversion (like stated in their docu) but two times 90 degrees phase DELAY. Being a 2nd order closed box system it is still one of the better solutions regarding transient behaviour however.

Regards

Charles
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Old 9th June 2004, 07:32 AM   #26
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phase_accurate mentioned:

Quote:
It is perfectly possible to make low-end EQs that don't have the restrictions of LT (not possible to make dynamically tuneable) and ELF (intrinsic LPF).
Does anyone have experience with Dr. Leach's method described in a JAES paper from the late 80's/ early 90's? I have a copy somewhere around here, but it's faded and barely readable.

A friend of mine built one for a car system back then with excellent results . His only comment was "It was a mathematical nightmare..."


Tim
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Old 9th June 2004, 08:02 AM   #27
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What is its working principle ?

Edit: Is it like the first circuit on this page ? :

http://members.hometown.aol.com/_ht_...b/mini-sub.htm

Regards

Charles
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Old 9th June 2004, 08:14 AM   #28
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Since group delay is defined as the negative derivative of the phase, a constant zero or nonzero phase over a range of frequencies results in zero group delay over that range.
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Old 9th June 2004, 08:34 AM   #29
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O.K,. but the manufacturer lets one believe that the circuit only generates phase-inversion, which is not correct. Furthermore the driver & ELF combination is a 4th order lowpass. It's transient behaviour is the same as a closed box with a 2nd order lowpass as x-over, neither better nor worse.

Regards

Charles
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Old 9th June 2004, 08:39 AM   #30
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hello all!
I only want to say - 80 Hz is maximum for plunger mode for driver.
it's a big difference these modes of operation. don't mix it. overvise you'll get distortion.
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