Something stirs in the Undergrowth

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chris661
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Re: Something stirs in the Undergrowth

Post by chris661 » Thu Mar 14, 2019 8:41 am

I can't comment on "dead and lifeless" with regards to the Ariels specifically, but I do wonder if the amplification used was hindering them.
I guess the only way to find out would be to bring them to Owston!

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ed
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Re: Something stirs in the Undergrowth

Post by ed » Thu Mar 14, 2019 7:36 pm

my apologies for labouring this Mark, but I've just remembered some things that might be pertinent.
To wit:
at one of the eggy outings in 2005 or 2006 I brought the Ariels along with the EL34 single ended amp. At some time in the proceedings Paul said to me something like 'I really like those Ed, they don't sound anything like mine'. The comment returned to me sometime later when Paul made a very black and white statement about how the Ariels weren't up to much. I had to remind him about his remark and how all Ariels might not be equal.

The point I'm now making is that, with reference to my previous post, they will doubtless sound different with different pieces of kit attached to them. Further, they are a diy piece and considering the build complexity, the stuffing of the tline, the parts used in the crossover...then it's a fair bet that no two ariels are guaranteed to sound the same...

so back to my previous post...please forgive me but whenever I see a black and white comment giving disservice to the ariels I'm prompted to follow it up.

Having said all this I must fess up and say they are not my best pair of speakers but I think the comments I've made are relevent, and they also apply to nearly everything that's written about loudspeakers on forums.....

it's never, or seldom, black and white.
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Re: Something stirs in the Undergrowth

Post by Greg » Thu Mar 14, 2019 8:34 pm

Ariels sounded wonderful at Eggfest when hooked up to Paul’s (build it in front of you) 212 amps.

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IslandPink
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Re: Something stirs in the Undergrowth

Post by IslandPink » Thu Mar 14, 2019 8:45 pm

Yes, (Ed) my comment was too black & white on that evening when I was enthusiastic about some other stuff that had finally worked out. ps. it's nice to have someone labouring a point on this thread for a change, it's often like the tumbleweeds are blowing through !
When Paul first built them he stuffed them way too much with heavy wadding and they did sound dead. I only put a bit of teased-out long haired wool in there in 2 places as Lynn suggested, I prefer things a bit underdamped overall.
Parts quality in crossover will make a fair difference too, I did a few swaps, particularly on capacitors.
There's a lot of variables in there and the amps used will be one of the big ones. At the end of the day I believe will be a limit to what you can do, due to the nature of the drivers. We can agree to differ on this if you like - but I'll stand up for the sweating, head-scratching & expense of the last 10 years on this point.
I did speculate this afternoon that one of the closest drivers in basic specs to the Vifas, are the FX120's ( Qms = 8 ). If you could still buy another 4 of them, it would be a very interesting swap, not too much required on the crossover other than a smaller cap & different resistor for the 'zobel' across the woofers. They are also 1 db/w more sensitive, but you could only use 20W max.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by Scottmoose » Fri Mar 15, 2019 10:13 am

I'd be a bit wary on that front to be honest. I like the FX120 very much; I've said for the thick end of 15 years it's about the best 4 1/2in driver Fostex have made, in some ways outstripping the F120a with the AlNiCo magnet & slightly different surround. However, it's also a different animal to the P13. It's about 23% down in terms of radiating surface area, and the frequency response would mean the entire low pass would have to be redesigned. The Ariel's low pass is an acoustic 4th order Gaussian created by the inherent 2nd order HF rolloff of the P13s combined with the damped 2nd order electrical. Since there is no equivalent rolloff in the FX120s, all that would then have to devolve to the crossover to maintain the voicing & avoid the phase-related 'snarl' Lynn referrs to (an effect of the MTM configuration & high crossover frequency; it would take quite a lot of work to get out of that, as he found!). The FX120 also has a short-throw underhung motor design that isn't quite as happy at higher drive levels as that of the Vifa.

All that being said, for the past couple of years I've thought on & off for my own interest about designing some kind of Ariel tribute with currently available drive units ( which would would have all the features currently favoured), while tracking a similar voicing & design balance as the original.

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Re: Something stirs in the Undergrowth

Post by IslandPink » Fri Mar 15, 2019 2:00 pm

Scottmoose wrote:
Fri Mar 15, 2019 10:13 am
I'd be a bit wary on that front to be honest. I like the FX120 very much; I've said for the thick end of 15 years it's about the best 4 1/2in driver Fostex have made.... However, it's also a different animal to the P13. It's about 23% down in terms of radiating surface area, and the frequency response would mean the entire low pass would have to be redesigned. The Ariel's low pass is an acoustic 4th order Gaussian created by the inherent 2nd order HF rolloff of the P13s combined with the damped 2nd order electrical. Since there is no equivalent rolloff in the FX120s, all that would then have to devolve to the crossover to maintain the voicing & avoid the phase-related 'snarl' Lynn referrs to (an effect of the MTM configuration & high crossover frequency; it would take quite a lot of work to get out of that, as he found!). The FX120 also has a short-throw underhung motor design that isn't quite as happy at higher drive levels as that of the Vifa.
OK, good points, I hadn't noticed the difference in SD, it's more than I thought. Also the low-pass. But I still think you could do it and it would be nice to hear. I don't know what other drivers there are. SB Acoustics didn't seem to have anything suitable when I looked yesterday.
Scottmoose wrote:
Fri Mar 15, 2019 10:13 am
All that being said, for the past couple of years I've thought on & off for my own interest about designing some kind of Ariel tribute with currently available drive units (which would have all the features currently favoured), while tracking a similar voicing & design balance as the original.
Well if you can find anything for the woofers, I have '6c' cabinets here doing nothing at present. I sold the tweeters though ! I should really sell the woofers, people are always asking for pairs without perished surrounds.
Scottmoose wrote:
Fri Mar 15, 2019 10:13 am
in some ways outstripping the F120a with the AlNiCo magnet & slightly different surround.
Romy the Cat was recommended the F120a for a small speaker project, there's a fairly long thread about it on his site. He eventually gave up & finished with a tirade of abuse about the units !
Oooh, but look.... the F120a has a Qm of 3.1 and the FX120 has a Qm of 8.4 ... :)
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Fri Mar 15, 2019 3:19 pm

Unrelated, just checked Troels site for updates - these look very interesting :
http://www.troelsgravesen.dk/SBA-761.htm
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by Scottmoose » Fri Mar 15, 2019 6:06 pm

There's no direct drop-in equivalents for the P13, although I imagine Audio Technology could produce a semi-custom unit that would be close, albeit with more advanced cone, motor etc. And a serious price tag. ;)

The closest standard units I can think of would be the Seas U16 and Scan's snappily named 15w/8434G00. Not direct equivalents -the low-pass would still need some work, but they're along similar lines, with poly or coated fibreglass cones & more advanced motor designs than the old Vifa.

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Re: Something stirs in the Undergrowth

Post by IslandPink » Sat Mar 16, 2019 11:36 am

Hmmm..
Better go up a size - Supravox 165GMF :)
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Mon Mar 25, 2019 7:56 pm

Bjorn Kolbrek on DIY Audio :
"..and if all goes well, there will be a book about horn speakers published sometime at the end of this year "
:D
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Wed Mar 27, 2019 7:14 pm

Back to the Quasar thing.
This speaker is really educational . Really really educational :confused3:
If anyone had been travelling home in the car with me this evening they would have heard light-bulbs going off in my head.
So, first things first, I reckon the zobel across the two FX120's ( see above ) did help. I just tried the calculated 0.33u and ~18R , as I could see that putting a lower R in there ( it's a pot ) would just be like applying a low-pass filter on there - which I can get from the amp anyway. Maybe I'll try that though - the R in there is actually a 100R pot. So, I think with that and the low pass from amp we can get an acceptable result from those drivers.

Now, meanwhile, listening in stereo the bass seems over-done lower down and not that tight. Not like how I remember James's.
So then I thought about the crossover as I've worked-out for the twin FX120's.
Quasar_FX120_cross.jpg
Due to the low efficiency of the two FX120's, the padding resistor is on the bass driver, not the AER mid as on James's. To offer excuses, the various suggestions James has given for crossovers have just used a series resistor on one driver or the other.
However I realised today that the 3.3R on mine is going to raise the effective Qes of the bass driver. Also the sharp impedance peak at the resonance (around 45 to 50Hz) will now be 'exposed' by the 3.3R and become audible.
285GMFZ.gif
285GMFZ.gif (9.4 KiB) Viewed 354 times
I can work out the effective Qts for the 285GMF in this case - 6.5 Re gets 3.3R added to it, plus about 2R from the amp, plus about 0.2R from the choke - hence 0.39 Qes becomes 0.73 . Qts that was 0.38 becomes 0.67. Hence what James had (there is some effect from the U-baffle) which was approx a transient-perfect ( Qtc = 0.5 ) damping is now somewhat looser than critically damped. 'course people describe 0.5 as critically damped too, which confuses the issue. Anyway ...

So there seem to be two solutions to this -
I. Buy some really expensive 8" FR drivers that are more or less as efficient as the Supravoxes.
ii. Us an L-pad approach to attenuating the Supravox, with a resistor in series, and one across the driver. I think ... think ... that the normal driver Qes is preserved here, because the driver sees the amp+series R in parallel with the resistor across its terminals, but I haven't found definitive back-up for this on links so far ( just lots of twaddle that drifts off the original question ) .
....but hopefully anyway, can be -in any case- tried fairly easily.

Phew ! glad I got that off my chest.
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by simon » Wed Mar 27, 2019 9:31 pm

Well, as we talked about before Christmas I found getting rid of the crossover by biamping was a really great way of solving that complexity. It's a different set of compromises though. But it sounded obviously better.

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Re: Something stirs in the Undergrowth

Post by pre65 » Wed Mar 27, 2019 9:44 pm

Mark, not 8" and not expensive, but I have a pair of these if you want to try them ?

http://www.bluearan.co.uk/index.php?id=BMA10AGN
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Re: Something stirs in the Undergrowth

Post by IslandPink » Wed Mar 27, 2019 10:25 pm

Sorry Phil, Qts way higher than AER's - 1.2, Rms 2.4 - need something less than 0.7 ideally .
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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Re: Something stirs in the Undergrowth

Post by IslandPink » Wed Mar 27, 2019 10:29 pm

simon wrote:
Wed Mar 27, 2019 9:31 pm
Well, as we talked about before Christmas I found getting rid of the crossover by bi-amping was a really great way of solving that complexity. It's a different set of compromises though. But it sounded obviously better.
Yes, you have more disjoint with the FE208's - .. bi-amping there makes sense ..but would be tri-amping in my case.
Current situation is '.. not bad - it's just genetically mean" so I think the L-pad thing may work.

The combination James put together here, it's just so integrated and finely balanced - so clever :D
"The bass is the king of the instruments - it has no known natural predator" (Wobble)

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