Something stirs in the Undergrowth

[chris661]

Mark, I was thinking you could use the 208 in a cabinet of some kind, then OB for mid-high. An 8" driver OB really won't do much bass.

Maybe the Deltalites?

Chris

[IslandPink]

Ah yes - OK, that's a bit too far from were I'm going with this currently , Chris . The OB Deltalite bass plus Basszilla 'upper' section is quite a good stopping-off point on my project, hence the interest . There's also a motivation for me in putting this together for the benefit of a few of the current OB users , to see if it's a potential step up from the Quasar-esque options with affordable drivers.

Ps. agree with your comments there, Waveguide .

Pps. A pair of 208Esigmas are on their way to me from Germany.

[IslandPink]

Ooh . More boxes ...
Got one out & playing on the floor now ( standard test #1 ) . Very good first impressions, fast, plenty of tonal colour .
More soon, with pics of what I was sweating over at the weekend , in preparation for the arrival of these .

[IslandPink]

OK, I also built one of these this week :
( One channel of Dick Olsher crossover for FE208Ez/Aurum G2Si ) . My only mod was to add a 3.3R in series to the ribbon tweet to allow knock down the greater sensitivty of (my ) G3 ribbon .

[IslandPink]

The eagle-eyed may have spotted that the input resistor to the treble crossover there was in fact a 33R instead of a 3.3R . This led to some disappointment initially with the sound of the mid/HF set-up
Here now is a pic of the ( perspex ) baffle with three drivers. Only the Fostex and the G3 are working at present .
The Fostex alone sounded great when put on the baffle. There were the expected shortcomings ( too bright, harsh on female vocals ) but the tonal colur and low-level presence are extremely good .

With Dick's Mid/HF crossover , the harshness is mostly gone, female vocals are pretty good, there's real HF detail . Most of the dynamics are still there .
The tonal colour is good but not as good as with the Fostex running 'free' . At the moment I'm running the Dyna XX-2 cartridge , whose top-end is not entirely to my liking . I'll switch back to the Denon 103R soon, and do more running-in and report back further .
It's possible I'll play around with the second channel to see if there's any chance of a lower-order crossover ( this one is 2nd down, 4th-order up ) that will preserve a bit more of the Fostex's tonal colour .

[steve s]

Wow mark looks good
looks similar to what I'm planning.
except there will be 5 drivers on my baffle and it will be wood and im thinking of doing in sections and stacking, so its more transportable
my router has gone kaput, so I've just ordered a new one, and work is on hold for a couple of days.

[Paul Barker]

It is certainly a looker.

[IslandPink]

Yes, I think the G-clamp ( holding the crossover ) and the 'Altuglas' cover film add a certain 'Je ne sais quoi' to the appearance .
At the moment I'm just trying to decide whether it's a replacement for an AER . The upper treble from the ribbon is better . The upper mids & low treble ( around the crossover - 2 to 5k ) is missing a bit of tone though .

[Paul Barker]

I fancy building a new OB. they are so easy and so seductive. Very hard to get away from. True what else you are trying to do is better. But we all have times in our lives when we can go to those extremes, and other times, which may last the rest of our lives, where we have to settle for less.

I am settling for less.

[Cressy Snr]

Nice looking project there Mark.

Baffles and SETs, are a match made in heaven

[IslandPink]

Yes indeedy .
Today, I've mounted up the other FE208 on the wooden ( braced 25mm MDF ) baffle. I've got a feeling I can get a bit more out of the two drivers than Dick did ( at least for my ears/taste ) . Listening more to the combo last night, I do feel the upper midrange suffers a bit, and the upper HF is a little 'disconnected' from its fundamentals , as a result of the slopes and phase shifts that are going on in the 2-5K region.
I've just re-designed the notch filter I'd used on the Jensen guitar speaker, for the FE208Ez , with the aim of getting a 3 or 4dB dip around 4k and so nulling the peak at that freq and some of the surrounding area .
Pics below of the circuit and the response/phase. L2 and R3 represent the speaker unit . I got a bit more notch than I wanted, so I could try 3.3R instead of 4.7R for the R1 . The phase shift through the notch is around -10deg to +20deg .

I've just sorted out the hardware and put it on the baffle and I'm listening now . My impression is that it's been quite successful . Female vocals sound quite nice, most of the midrange tone of the Fostex is still there , sounds detailed. Aside from a slight lack of fine detail at the top, it's almost good enough on its own !
So, I think this can be the basis of a lower-order crossover with the Fostex rolling off 1st-order at maybe 3 or 4K, and the ribbon coming in higher . I'll go away and check what it was Dick did with one of the Basszilla options where he used the DX4 and brought in the G2Si at a higher frequency - should be relevant .

[IslandPink]

Wow .. today has been a breakthrough .
Finally I have landed on the kind of sound I've been searching for, for over 5 years .
After checking out the effect of a notch on the Fostex, last night and this morning I roughed-out the whole crossover and made an extension board for the G3 to put on the MDF baffle .
Conveniently, my beta-tester Len Edwards came round for a listen . We played the standard Olsher crossover combo on the perspex baffle . Len was very complimentary at first, but then on female vocals and some of the guitar stuff he noticed some problems , as I had - some loss of treble tone and a slight harshness on the vocals . Then I put the MDF unit in place and we had a ( the first ) listen to the lower-order crossover . OK - bit nicer in some ways ... Then I swapped the polarity of the ribbon tweeter .. Wow ! The whole thing came into focus and the tone was much better .
Then.. after a few minutes of admiring my work, I realised the transparent protective plastic 'tape' was still over the front of the tweeter Then it sounded REALLY good !!

OK, so I've provided the LP and HP crossovers ( The Pinkzilla mod ! ) below in 'Spice' form . There will still be some tweaking to do, adjusting the exact HP point for the ribbon, and getting the level flat from 1k to 10k , but it's really close to perfect right now. It will sound even better on the perspex baffle .
This is the first time I've heard a MF/HF set-up that has tone, dynamics , crisp edges, low-level detail and NO harshness, at 95dB+ . I reckon it's better than what James has with the Quasar, now, and I am just tickled pink .

[slowmotion]

Always good to hear!

[Paul Barker]

Wow!

[IslandPink]

This evening I captured some 'wav' files of white noise using 'Audacity' . The analysis on there was a bit crap and showed a cut-off at 8kHz . I know it's going higher than that from test tones ( could hear 14kHz ) . I thought if I saved them, I could analyse using 'Audiotester' later once I'd got the license file in . However it doesn't seem that easy . Andrew is looking into it, but if anyone can advise , let me know. I just want to import this existing wav file of white noise, but there doesn't seem to be a button on the menus for that .
I would really like to try & avoid doing the measurements again as it took me a lot of sweating and rearrangement of the front room !