Axiom 401 in a Metronome Cabinet

[Toppsy]

Well now Dave. That's an interesting concept. I had picked up on this over on DiyAudio.

I do like the new sloped side panels and trapizodal shape of those bookshelf speakers. Is this the new 'IN' shape?

[planet10]

Performance is stepped up for sure. So is build difficulty == prbably no big deal for you.

I am developing a full slate of these enclosures for A7/CHR/CHP/EL70/FF125/A10/FF165 and will likely have a go at the FF225 too. A12 was the 1st and has been around for awhile and was the 1st.

For the smaller drivers there could be as many as 3 different versions -- inspired by a conversion of Mar-Ken12T to EL70 (Bernie surprised me with a set of solid douglas fir MK12T, but no drivers to put in it. There will be WoofTs designed for each one (and will be somewhat interchangable). I should have the 4" Peerless for the uFonkenSET WoofTs tomorrow or monday.



And the FF85wk as seen above.

dave

[simon]

The new FF85wk is a decided step up from the already VERY good FF85k. Some of you may remmber the set of uFonken that Scott brought to one of the events. The new larger uFonkenSET take them a step further. No need for a super-tweeter here (response out beyond 25k), it will be intersting to hear with the WoofTs.

Really? I thought Scott's uFonkens were magnificent, time to do a little reading I think.

[planet10]

Really? I thought Scott's uFonkens were magnificent, time to do a little reading I think.

They are. I was shocked (and happy, i was worried about the new one being up to the standard set by the old one) to hear the differences we heard.

Scott will be getting a set of the new drivers, and maybe an experimental flatpak to house them (no time frame)

dave

[Cressy Snr]

Seems like the new Fostex FF range are very good then

I suspected they might be.

[simon]

Can't find anything on your website Dave, can you point me in the right direction please?

[planet10]

Can't find anything on your website Dave, can you point me in the right direction please?

Nothing on the site yet ... website has lots of stuff needs updating... some of the more current stuff is here too. http://www.diyaudio.com/forums/planet-10-hifi/

Any commentson uFonkenSET are comments (mostly almost OT) on diyA and here.

dave

[Cressy Snr]

With all the tweakery of the 6B4G amplifier that went on last week, I forgot to mention a tweak to the Metronomes that has improved their performance.

If y'all remember I had tried lowering the value of the series feed cap to the tweeter down to 2.2uF but had given up after the tweeter had become
exposed by the modifications, giving a hard edge to the sound.

After having returned the cap value to the 4uF and turning down the Lpad
I was back on familiar ground.
After a few days however I was still not convinced I had the crossover right.
The fact was that there was something amiss and no amount of trying to reason it away was going to work.
As Colin and both Chris's had hinted at, there was still something wrong with the treble that I could not pin down and it was adding a dirtying effect to the midrange somehow.

I remembered a conversation I had had with Chris (Stratmangler) as I was loading the car after Colin's bash, where he had mentioned that he'd
finished up moving his supertweeter XO point way, way up around 12HKz on his FH3s before he had been satisfied that the transition between the FR and the ST was good enough.

To cut a long story short, I decided on another try with the crossover on the Mets. Putting the 4uF and 2.2uF caps in series gave a value of 1.33uF
for the crossover cap. Auditioning the system after the cap mod, it was dull, but turning up the Lpad to -4dB restored the balance to the speaker
giving a super sound with much clearer imaging, depth and treble extension. I now had all the very top harmonics without the slight hardness.
Another bonus was that the midrange had cleaned up quite nicely.

I think, rather than leaving the caps in series I will purchase a high quality 1uF cap for the crossover to put the finishing touches to the Mets.

I can see what Chris meant. I had gone a bit higher with the 2.2uF cap, but not nearly high enough, quite surprising how high up the audio band
the supertweeter needs to be brought in, higher than I would have imagined with an 8 inch driver.

[planet10]

...a tweak to the Metronomes that has improved their performance....

You are pushing towards my approach to adding a superTweeter. I dispense with the L=Pad all together, instead using the attenuation of the 1st order XO to bring the tweeter in line with the FR. This only works with FR that hit at least 10k or so.

With am sT that is much more efficient than the FR you could be XOing VERy high (as an example T90 added to FE206eSR ends up being XOed with 0.33-0.47 uF.

C = 0.159 /(Rf) or f = 0.159/(8c)

If R = 8 then f ~ 0.02/C or nominal 42-64kHz XO point

So if we look at FF225wk FR



a good starting point is that we want to fill in above 10k -- we only need a starting point, since we will be fine tuning by ear.

Efficiency of FF225 is specced at 93 dB, FT17 at 98.5 or a 5.5 dB diff. Round up to 6 dB. So we want FT17 down 6 dB by 10k or a 20k estimated XO as a start point. With nominal 8 ohms this would be 1 uF. You can look at the actual impedance curve if you want. My measured one is limited by a 22k nyquist, here is the factory (which would indicate our 8 ohm approximation is pretty good):



So you need a cap a step smaller than what you estimated, say 0.68, and a handful of 0.1 uF caps. Start with the "big" one, listen, add a 0.1 in parallel, listen, repeat until you are getting too much top, then back it off a step. Then go get a high quality cap of that value.

dave

[Cressy Snr]

Thanks for that Dave.

At least I know I'm in the right ballpark with the XO point now

Steve

[Cressy Snr]

I have installed a 1uF Claritycap ESA to feed the HF unit after following
Dave's advice.

The LPad is still in circuit for now but is only adjusted 1dB down now instead of the 7dB it was at during the worst of the HF malarkey, as Dave said, the 1st order XO rolloffs are indeed setting the tweeter level for me.

I still like the idea of being able to adjust the treble level but the LPad is almost redundant now.

The speakers sound absolutely marvelous, with a degree of electrostatic clarity, cleanliness and neutrality that is quite startling on the right recording.

I think I'm even more glad I commissioned them

Steve

[Cressy Snr]

Thanks for the positive comments from the Owston meet chaps.
I know that sometimes I can be a bit too enthusiastic for my own good
but I really think these are special....

Which leads nicely on to the new Fostex drivers. I really do reckon these drivers are the best thing to come out of Fostex for a long while.
Gone is the shouty quality of some of the pale coned whizzered units, to be
replaced by a lovely even-handed midrange, whose even quality, in the right cabinet, extends way downwards into the low bass regions
and all without sacrificing too much efficiency, with the larger drivers at any rate.

So I think it can be safely assumed that the FF225WK is a superb candidate for a Metronome, if used with a good quality, high efficiency
horn supertweeter. They are a bit expensive at around 250 quid a pair but they are still IMO excellent value for money.

I think the FF165WK would also do well in a Metronome, but that's for somebody else to find out.

[Mike H]

Remind me where the name "Metronome" comes from, just the shape?

BTW I liked 'em as well

[Cressy Snr]

Remind me where the name "Metronome" comes from, just the shape?

BTW I liked 'em as well

Yep that's where the name came from. The fact that they looked like Metronomes.

Now if Linn made them, no doubt they'd be called the "Obelisk"
has a nice ring to it that one.

[Lee S]

Shahinian would have beaten Linn to it, Steve.... They have been making the "Obelisk" speaker for many years now (34 in fact).

http://www.shahinianacoustics.com/Obelisk.htm