Fertin project - calling all open baffle experts

[reverendclark]

Me for a pair.

I've already been talking to Black Forest, so in fairness, I need to tell them what I'm going to do.

Peter C

[dice45]

Peter C,
§%$§$%§ !! ok let's see if and how quick i get access to Fertin.

Peter Daniel,
the vacuum tube ghost will haunt you if you buy Fertins!

[Peter Daniel]

I was musing tube amp for many years now. Maybe finally I will have a good excuse to build one.

[Brett]

Peter,

Which Fane driver do you have in your coaxes?

Cheers
Brett

[reverendclark]

Brett,

I got a pair of 15DX HEs from Adam Hall just before they stopped handing the line in the US. Originally I had Ramsa compression drivers in them, then I stepped up to the big leagues and got some TAD TD2001s.

Peter C

[bcherry]

here's the front

[bcherry]

and the other side

[bcherry]

You can see the new baffle is drastically different from the first one I posted. It's built according to the golden ratio used by Japanese audiophiles as previously linked. I knew the driver would be close to the floor, and it was with qualms I had it built, but when I actually saw it come in the door - my heart sank! The bottom is only about 23cm off the floor. I had visions of listening from the orchestra pit.

Here are the measured frequency responses in my room using the Sheffield setup and test disk:
ambient C weighted noise 60db
filtered pink noise 1/3 octave bands
25hz 70db
31.5hz 73db
40hz 75 db
50 hz 78db
63hz 81 db
80hz 85db
100hz 87db
125hz 88db
160hz 88db
200hz 87db
250hz 85db
315hz 85db
400hz 85db
500hz 82db
630hz 82db
800hz 82
1khz 81db
1K25hz 82db
1K6hz 81db
2Khz 81db
2K5hz 80db
3K15hz 79db
4Khz 79db
5Khz 81db
6K3hz 84db
8Khz 84db
10Khz 82db
12K5hz 78db
16Khz 73db
20Khz 69db

So the sound is now coming in at 40hz and saying goodbye at 16Khz (if my SPL meter is to be believed). Also there is a nice hump from 80hz to 250hz which now gives somes weight down there. Measured in position as shown in the picture.
Image height doesn't seem to have suffered. I still get sounds coming from my musical reverie painting. Low bass is pretty good. Overall tonality is much more balanced.

But why does this work? Is there really something going on with this 'golden ratio' thing? The configuration is counter to all the advice given about keeping the driver 70cm off the floor.

I'll play with positioning and interested to receive any suggestions about it.

Another issue. The former attached to the driver had started to scrape the cylinder. I don't know the proper procedure but here's what happened: The nuts attaching the suspension came loose so the driver went off centre. I loosened all three nuts so the suspension was loose, then slid a thickness of paper around the diffuser into the gap (from the front). This kept the former equidistant from the cylinder walls; tightened the 3 nuts up and it worked! No more rubbing.

OK, that's the latest installment. I think we're closer to home now.
The BEhringer could do the rest.

Brian

[bbaker6212]

Wow, 10db down from 10K to 16K. I'm having a hard time understanding how this thing cannot sound dull, rolled off, and lacking in detail. Do cymbals, high-hats, etc., sound real with these?

[Peter Daniel]

What mike are you using? Most of the mikes are OK at mid frquencies, but when it comes to both ends of spectrum they might be deceiving. You ears are the best test. If the highs seem to sound OK the mike lies.