microflex

[somakmaitra]

hi,
i wish to build the speaker design published in the electronics world 1995 by jeff macaulay . The crossover design seems to have some errors . has any one build the system ?
it is very compact and the concept is interesting !(6th order alignment called microflex)
help required!!!

[phase_accurate]

That one was in the "Bass Issue" of Electronics World, wasn't it ?
If yes, I can try to undig the article to see what might be wrong.

I haven't built this one so far but I have built some other form of deliberately misaligned reflex box with EQ.

Regards

Charles

[somakmaitra]

That one was in the "Bass Issue" of Electronics World, wasn't it ?
If yes, I can try to undig the article to see what might be wrong.

I haven't built this one so far but I have built some other form of deliberately misaligned reflex box with EQ.

Regards

Charles

thank you charles for your reply .
it appeared in the june 1995 issue . there is a problem with the resistance code and value mismatch .
since you have done such 6th order aligned speakers what is the bass response of these speakers ?
i stay in india and space is a constraint so i have to go for compact designs and this one had a side firing woofer which appealed to me very much ,though to the purist it may not be the best .
i have another question
if i did not understand the phase correction circuit in the project .is it possible to delete the phase compensation circuit ?since there is a great deal of controvercy regarding this .
can i use a linkwitz 24db crossover here instead of the one given ?

regards ,
somak

[phase_accurate]

Hi Somak

I will try to find the mag and have a look.

Regards

Charles

[somakmaitra]

thanks a lot charles,
if you require i can mail it to you . what was your response with these deliberately aligned speakers ?
do you have the latest designs of jeff?

regards ,
somak

[phase_accurate]

Hi Somak

Unfortunately I couldn't find the June '95 issue. Back then I bought the magazine only every now and then at the newsagent. But I found the February '94 issue this morrning (The "Bass" issue) and that's exactly where I remember the name "Microflex" from.
On page 107 there was an article by Jeff Macaulay titeled: "BIG BASS Small box".

It was in fact this article that woke my interest in delibelately misaligned reflex boxes. One design I built was using a JBL 2206 P.A. driver. In a proper B4 alignment this driver would achieve a cutoff frequency of 60 Hz approx. I deliberately took a box a little larger than optimal and tuned it to 45 Hz. It needs a simple lag filter in front of the amp to compensate for the early, but reasonably flat, rolloff. Using this "EQ" it is theoretically flat down to 40 Hz (-3 dB). Because I used it close to a wall, this corretion wasn't even needed to achieve a (subjectively) balanced response.

While planning my Manger box I was playing with tunings on the PC. A box sized for a Butterworth response (if it were a closed one), and then tuned as reflex at half the frequency the cloded box fb would be, gave responses that gave a 6 dB gain compared to an ordinary closed box (both in terms of excursion and SPL) in the range between the two aforementioned frequencies. Below the reflex tuning frequency the response starts to drop like an ordinary reflex box (i.e. at 24 dB/octave). I dropped the idea in favour of a "real" closed box with a high xmax driver. But it might be a good compromise for small boxes.

If you can mail me the article from June '95 then maybe I can answer your questions.

Regards

Charles