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mikee55 13th January 2007 09:38 AM

My Linkwitz Transform wants to violently rip my driver to bits
Hi all, now that my LT works, I'm a bit concerned that it seems quite a potent little circuit. I guess my cheapo driver isn't any good?

Mikee55 :D :scared: :scratch2:

cocolino 13th January 2007 11:37 AM

Theoretically You could force a 25mm dome tweeter to do 15Hz but it`s obvious that this is not a good way of implementing the LR-Transform.

The LR Transform Circuit is excellent to extend low frequency response of a closed box driver combination when moderately designed.

The mechanical abilities of the drivers always determine to which limit You can push them with the LR-Transform.

If You encounter distortion with Your LR-Transform, You`d want a higher linear Xmax. or bigger cone area driver (or both, or more drivers) or to apply a more moderate target function.

You could also experiment with a HP-filter before the LR-Transform.
Not only can this limit low-frequency excursion of the driver to reasonable limits it also can prevent the LR-Transform circuit itself from possible clipping due to very high-gain conditions at low frequencies, depending of Your desired target function.

AndrewT 13th January 2007 11:54 AM

I thought the LR transform already had a 2pole High Pass filter built into it.


is it the 4pole alignment that has the HP filter and something completely different?

please explain.

cocolino 13th January 2007 12:24 PM


I thought the LR transform already had a 2pole High Pass filter built into it.
Hi Andrew,
it`s not exactly "built into".
The LR-transform - together - with the driver in the box result in an acoustical II-order High-Pass filter.
The LR-Transform, as the name implies, only transforms the II-order High-Pass driver (+box) parameters into new ones.
It doesn`t create an additional HP-filter.

consort_ee_um 13th January 2007 03:42 PM

Could you explain what enclosure you are using. You would get better results using a sixth order alignment ie a second order HP filter with a vented box. This cuts down the excursion at low frequencies.

mikee55 13th January 2007 04:58 PM

Here ya go
2 Attachment(s)
Now I have to say Big Thanks to richie000boy for his help with measuring the loudspeaker T/S parameters and the other math involved. Also, I can only produce basic hand drawn PCB's, so as far as Audiophile and quality go, I'm limited in what I can achieve, with what I have to hand. The box was my cousin's and got a bit damp. The driver is a cheapy car job and the case for the electronics is a Mini ATX psu case. The amp is a Technics SU-V2, which is dead on one channel. Its running off of my PC soundcard at the mo. I have a hum I cant shift yet. I'm just pleased its running.


mikee55 13th January 2007 05:15 PM

Closer on electronics
2 Attachment(s)
Hi all, here's a close up of the electronics.The op-amp you see is a TLO72. I didn't have a TLO71 to hand, so I had to hang the TLO72 off the board and use one half of it. The hum's getting anoying now. Any suggestions?

richie000boy has already said the powersupply is a bit too close to the first board,(the Input mixer/Phase switch). Maybe a new case with a different layout might help? :)

Cheers Mike

mikee55 13th January 2007 08:30 PM

Hi all,

I've finaly got my Linkwitz Transform to work all be it with "HUM!!!!":devilr: :bawling: :mad: "hum!!!!". I can't eliminate this F ing Hum.

Sounds like mains.

:angel: Cheers Mike

phase_accurate 13th January 2007 08:34 PM

Maybe you should use a less demanding EQing. You seem to EQ one and a half octaves out of your setup. Maybe youd better try with one octave only !?

What is actually your original tuning and what is the target tuning after LTF ?



mikee55 13th January 2007 08:54 PM

If I can remember
Hi Charles, I lost a partition on my harddrive that contained all my data. I think I've gone from 58hz and I'm pushing for 30hz. It seems to reach low. I just got this horrible hum when there's no signal. Just been watching/listening to a Harry Potter film and Its good. Normaly I'd get a room full of bass which reached up to vocals, now it only makes a noise when its supposed to. In some dance music instead of bass fading away lower down, it seems to stay level!

Its just this hum!:mad:

Cheers Mike

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