Ali Bastanis OB testing & results

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IslandPink
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Ali Bastanis OB testing & results

Post by IslandPink » Sat Jan 11, 2020 10:02 pm

I should have posted this a while back but it got busy before Christmas.
We had a small get-together at my place late November. I'm not sure what to call it, but of the options, 'Pink-meet' sounds the funniest.
Anyhow, amongst other things Ali demonstrated his current set-up with Bastanis 'OB' speakers and the amps he's using. I say 'OB' because there isn't much of a baffle.
The amp set-up as far as i can remember uses a Behringer digital crossover & amp combo for the bass, and a Unison SS/Valve hybrid amp with EL34's on the output for the 10" mids and tweeters.
Interestingly the mid drivers are of a fairly low Qts which gives them a rise through the mids with a high-pass effect around 200Hz - this allows the Unison to run without going through the digital filtering.

Ali said he wasn't sure about the crossover yet, and I think he had tried the bass in the other polarity. Given the differences between the valve amp path and the Behringer crossover & SS amp, it was not obvious. We tried both options, on two or three tracks, and it was not 100% clear but we slightly favoured the reverse connection to what Ali had been using.
With REW and my Behringer UMC interface, here is the result for the set up as Ali had been using it - baseline.
ALI_Nov23_start.jpg
Here is the mid only :
ALI_Nov23_Mid.jpg
Here is the bass only :
ALI_Nov23_bass.jpg
Oh, next post ... too many pics ...
Last edited by IslandPink on Sat Jan 11, 2020 10:10 pm, edited 1 time in total.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Ali Tait
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Sat Jan 11, 2020 10:08 pm

Cheers for posting Mark, just to point out the S6 isn’t a hybrid, it’s ECC83 front end into PSE EL34, three valves per channel. About 35w I think.
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Re: Ali Bastanis OB testing & results

Post by IslandPink » Sat Jan 11, 2020 10:10 pm

Ah, thanks for clarification. Very good.

Here is the full system again but with the bass polarity swapped. This is a much clearer result than we had from listening.
ALI_Nov23_ii.jpg
The compression tweeter comes in just with a 1uF cap. I thought this was too high and it does look like it's wrong as the FR trace shows a big dip from 5 to 10k. The mid driver does rather fall off a cliff above 5kHz. - maybe due to the Bastanis 'treatments'.
I had a few caps to hand ( what a surprise ! ) and added another 1.5uF so we had 2.5uF to bring the compression tweeter in earlier . We got this result :
ALI_Nov23_Final_2p5u_cap.jpg
I think we also did a small number of measurements to average room modes, and got this additional trace :
ALI_Nov23_Average.jpg
The sound was much improved with the tweeter coming in lower. There didn't seem to be any harshness associated with it being lower, it's still a fairly high high-pass even for a 3/4" or 1" driver, to my mind.

I'll try to load up the original files from the laptop next ( tomorrow ) and see if I can provide some extra resolution.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Sat Jan 11, 2020 10:17 pm

Yes indeed, a very good improvement, thanks again Mark for taking the time to do the measurements. I did enjoy the speakers but always felt they weren’t quite right, most likely due to the phase inversion on the bass- phase seems to be something I’m particularly sensitive to. Adding the caps to the tweeter was also a big plus, I now have no niggles and they sound great to me at home.
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Re: Ali Bastanis OB testing & results

Post by IslandPink » Sat Jan 11, 2020 11:26 pm

One interesting thing was, we kept finding a noticeable peak and dip around 60-70Hz. It was odd as it appeared in almost the same amplitude on the mid driver traces - was many dB lower - as the bass driver trace. SimonC explained to us that his computer analysis of my room shape & dimensions had indicated a major mode around 60 or 70Hz, so that was quite educational.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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