Fostex plus Heil

[v-bro]

Nice one, but I made several pre-made filters in different slopes and frequencies. By this experimenting I now know exactly how to tune a "tailor-made" circuit.

The marchand xm-46-type filter I use doesn't need a supply, it's passive:
http://www.marchandelec.com/ftp/xm46man.pdf

That's why I want to add a buffer stage like this:
http://www.autocostruire.com/catalog...7082838e0019ee

[planet10]

Originally posted by v-bro
Use a DIY-ed version of Marchand xm-46 at the moment

Where did you get your chokes? Or did you make them? More than once i've done a bit of research on diying similar but get stumped by the chokes.

dave

[v-bro]

I built them myself, by using an LCR-meter (really AM glad to have one...).
I'm testing a few different ones I made at the moment, with different core's...

[planet10]

Originally posted by v-bro
with different core's...

What kind of cores? Can you show & describe some examples?

dave

[planet10]

On subject:

I know how muc potential this kind of combo can have... chris has the bipolar Fostex FW227/Heils set up at the moment.

What is the story on the Rythems? I'd love to see some detail pictures (insides too)

dave

[badman]

I'll take a few more exterior pictures, but the interior may not really be appropo. The Rethms are a commercial product, they sell just the cabinets sometimes (some dealers put other fullrangers in besides the lowther). A fortuitous set of circumstances brought this (and another) pair of cabs into my posession.

Their construction is a hybrid horn/acoustic labyrinth. There's a large plastic piece that mounts onto the back of the magnet (looks somewhat like a giant tapered phallus) that gives it an expanding 'ring shaped' cross section, which is in many ways something like a conical horn. This somewhat damps larger cone excursion and prevents backwave reflections from hitting the diaphragm. After this, it's a textbook acoustic labyrinth, from what I know, IE, an unstuffed TL.

There are 2 circular openings/terminii of different diameter on the sides, which vent both ways (left and right), I'm not sure if there's an increase in final taper before these (another horn-like element).

The Fostex drivers are ones I found to be the best compromise for me, as I am not fond of the lowther top end. These FF225ks are very smooth in terms of response, and have an incredibly powerful motor, and seem well-damped in general. Pretty impressive dispersion for a non-whizzer 8, too. The sacrifice is, 14k is the ABSOLUTE limit of their top end, beyond that, it's an extremely steep rolloff. I prefer wideband mids to true 'fullrangers', as a general rule, taking the frequency extension over the 'ultimate' in coherence.

I'll post some more pics as time goes on, I'm going to try to keep the blog pretty well updated, Baddy's Blog
but will post here when I have some more pics of different angles.

[v-bro]

I will make some pictures of the coils, but have to borrow a camera from a friend...can take some time...

I used wire from an old but unused transformer and wound it on a small ferrite core from a tannoy speaker filter, in my place you literally trip on the filterboards laying around. So sourcing some ferrite core is no problem I guess, still wonder if I can better use air-cores?

My guess is that ferrite based cores are better in this field...

Still experimenting though, have to borrow a friend to do some A-B testing..

To Planet 10:
Is there some problem I don't know of that you can tell me about on making chokes?

[v-bro]

here's a picture of the chokes, one is with ferricore and halves of a piece of steel tube. The other is a ferrocore carrier with a plastic carrier inside, I removed the original wire with wire from a transformer. The ends of the wire is soldered to a thicker coated copperwire to give it more strength.

These are for a lowpass filter at aprox. 200 hz, the one I previously made I already sold....

But maybe I'm just lucky with all my old stock...I'm quite a collector, and everybody knows, I get a lot of old stuff from them....

I'm still not sure what makes the better coil, I can only make sure the measured value is allright, the rest is still unexplored territory for me...

[v-bro]

ehm... pardon me, but the one with the steel halves is ferrocore and the other ferri(te)core....
I just looked it up..

[planet10]

thanx for posting the pic. I know what to go looking for now.

dave