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Dxvideo 30th August 2005 07:20 AM

Linkwitz transform circuit?
Hi all,

I plan to build an active 2.1 speaker for my computer. It would be 30+30+50W with 3 x TDA1514A. For the subwoofer, first I think to use iso barik mounted two 16cm drivers in parallel. And the box size would be about 25liters. As I calculated the F3 would be around 28Hz. But last week I found that:

It is a good idea to reduce the box size. And I can use only one
driver and a better result. But I have some questions about application.

Does anybody use that circuit? And does it work really? Finally does it suit for 50W range? (and of course for a 16 or 20cm driver)

Thanks in advance for anybodys help..

nafunga 30th August 2005 07:42 AM

I built the circuit a while ago and use it with a 100w amp. in a 35x35/35 box with two 8" drivers in isobaric configuration. results are excellent. I use it for hi-fi . My listening room is only 5x4m and with my current SE valve amp. provides exceptional sound quality. I use a pair of Royd mini - monitors. Generally I listen at fairly low levels but it is capable of suprisingly high volume. In my view it compares very favourably with rather expensive models that I have owned. Before going to the present set up I was always a fan of TL speakers but needed to 'downsize'. Well worth building.



Dxvideo 30th August 2005 08:09 AM

Thanks a lot David,

But I still have questions. I afraid that it may cause distortions in high levels! Because for middle frequency (about 20Hz) that circuit gets about 12dB gain. Do you think does make problems? And do you think I still apply a iso-barik mounting? Doesn't only one driver enough?

Thank you very much.


nafunga 30th August 2005 08:21 AM

Don't forget that you can set the gain and 'roll off' independently. Iv'e had no problem in that respect but carefull initial setting pays off. As to isobaric or not - it allows you to use a smaller sealed box than otherwise. Try it both ways perhaps but I think an 8" driver is probably minimum for low bass.

Kind regards,


Dxvideo 30th August 2005 11:07 AM

Yes I can set gain and roll-of frequency independent. But when I set gain a lower value the upper frequency (50Hz and up) response will be reduced same time, and that means a poor curve! If I want to reduce only middle frequency gain what will I do?

And thanks a lot for your helps again..



nafunga 30th August 2005 02:20 PM

I don't see that you will have a problem because the response of the driver will fall off at 12db below resonance which (if the driver and box are correct will be raised to 60 - 70Hz (ish). You may need to filter the LF response of your main speakers to ensure a good crossover - it works well. The last edition of 'Hi-Fi News (UK magazine) actually had an article on subwoofers and recommended a small sub (rather than a large one) in order to reduce box colouration - it also advised a LF roll off to the main speakers.

Kind regards,


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