Ali Bastanis OB testing & results

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simon
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Re: Ali Bastanis OB testing & results

Post by simon » Thu Feb 06, 2020 6:53 pm

Yes, I'm interested in the drivers being out of phase, and how that works without a lot of cancellation, but thought one step at a time.

I get the equal weight distribution/simplified centre of gravity of a pair, but supporting a single driver should be a reasonably simple structural problem, especially if using something with a high strength to relative weight ratio like metal tube.

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Re: Ali Bastanis OB testing & results

Post by JohnG » Thu Feb 06, 2020 7:35 pm

Hi Ali
Vic is using a 33mm Key Klamp Tube and Fitting System for the framing.
The fittings are locked to the tubing by a Allen Grub Screw.
If it was seen to be advantageous, the ends of the tubes can have internal fitting push in caps supplied, so they could be filled with a material of choice and sealed.
I'm glad you got the WOW!! experience, as the treat of the day.

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Ali Tait
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Thu Feb 06, 2020 8:18 pm

I don’t see that as necessary John, I checked for any energy transfer from the drivers to the frame and there wasn’t any, so I don’t think filling the tubing would yield any benefit.

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Nick
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Re: Ali Bastanis OB testing & results

Post by Nick » Thu Feb 06, 2020 9:34 pm

but supporting a single driver should be a reasonably simple structural
But doing it will a built in 5Hz low pass filter like it resting on a cable sling will be a lot harder I would have thought?
Resistance isn't futile it's V / I.

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Re: Ali Bastanis OB testing & results

Post by simon » Thu Feb 06, 2020 10:54 pm

Ah right, I'd entirely missed the suspension mechanism when I flicked through on my phone. Looking again on a computer it's far from trivial! A 3 wire cradle supported from two basket fixing holes and something around the magnet, suspended from above would probably be easiest, if there's enough sensitivity of adjustment of the cables. But that won't naturally damp oscillation forwards and back as well as Vic's solution.

Instead of bringing the cables together at a point the triangle they form could be inverted (still suspending from above of course), which would be much better at damping movement, but will start to get a bit, erm, inelegant. It would be very interesting to see a close up of how Vic suspends the PRVs.

Wonder how much difference the method of support actually makes?

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Re: Ali Bastanis OB testing & results

Post by Wolfgang » Thu Feb 06, 2020 11:46 pm

Aside form the frame construction this "bass-design" would cost:
4x $299.90 for the woofers and $550 for a Behringer NX4-6000!
This is basically about the same price as the GR open baffle dual servo subs with 2 A370 amps and servo control.
The most important difference for me is the fact that the Dayton UM18 can be coupled at a higher frequency to the mid driver which leaves a lot more options. But would it work at 450Hz in order to do a test run with the La Scala horns, only replacing the bass? That would be the upper limit considering the frequency response graph of the UM18.Is this x-over point still realistic for getting good bass results?

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Re: Ali Bastanis OB testing & results

Post by Clive » Fri Feb 07, 2020 12:00 am

simon wrote:
Thu Feb 06, 2020 10:54 pm
Ah right, I'd entirely missed the suspension mechanism when I flicked through on my phone. Looking again on a computer it's far from trivial! A 3 wire cradle supported from two basket fixing holes and something around the magnet, suspended from above would probably be easiest, if there's enough sensitivity of adjustment of the cables. But that won't naturally damp oscillation forwards and back as well as Vic's solution.

Instead of bringing the cables together at a point the triangle they form could be inverted (still suspending from above of course), which would be much better at damping movement, but will start to get a bit, erm, inelegant. It would be very interesting to see a close up of how Vic suspends the PRVs.

Wonder how much difference the method of support actually makes?
I dangle my similarly configured drivers from an inverted V. Contrary to all expectations there is no forwards /backwards movement of the drivers, just the cones move and move big time with 1 to 2kW I was putting through them tonight. I use lesser drivers than Vic but still it’s effective.

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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 7:13 am

For a single driver, I did think about two vertical lengths of cable, threaded in and out of the fixing holes on each side, cable could be tensioned to suit.

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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 7:17 am

Wolfgang wrote:
Thu Feb 06, 2020 11:46 pm
Aside form the frame construction this "bass-design" would cost:
4x $299.90 for the woofers and $550 for a Behringer NX4-6000!
This is basically about the same price as the GR open baffle dual servo subs with 2 A370 amps and servo control.
The most important difference for me is the fact that the Dayton UM18 can be coupled at a higher frequency to the mid driver which leaves a lot more options. But would it work at 450Hz in order to do a test run with the La Scala horns, only replacing the bass? That would be the upper limit considering the frequency response graph of the UM18.Is this x-over point still realistic for getting good bass results?
Well the price of the drivers is what it is, I’d say an NX 3000 could be used instead which is a good bit cheaper. How much were your Lowthers? :D

Vic commented that he’d tried a lot of bass drivers, it was these particular ones that give these very good results.

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Ray P
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Re: Ali Bastanis OB testing & results

Post by Ray P » Fri Feb 07, 2020 7:45 am

Ali Tait wrote:
Fri Feb 07, 2020 7:17 am
...which is a good bit cheaper.
Not sure expense was where Wolfgang was coming from Ali, just commenting that the price point is similar to the servo-equipped bass he's been looking at folllowing the SLOB bass loading discussion.

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Ray P
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Re: Ali Bastanis OB testing & results

Post by Ray P » Fri Feb 07, 2020 7:50 am

Do the cables serve a purpose other than to locate the drive units - maybe they're some sort of compliant arrangement? If not, for a single speaker mounting arrangement you could use spacers, like those connecting the bass units in the pictures, to mount the unit to the frame?

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Re: Ali Bastanis OB testing & results

Post by simon » Fri Feb 07, 2020 8:35 am

It's a good question Ray. My gut feel was/is they would decouple the drivers from their supports - rigid supports will couple the drivers to whatever support arrangement more. Whether this is significant is another matter, but Vic's and Clive's experience perhaps suggests the lack of rigid coupling is a positive thing.

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Ali Tait
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 9:00 am

Yes it seems that way, I was struck by how little energy was being transmitted into the frame whilst playing some low stuff.

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Ali Tait
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Re: Ali Bastanis OB testing & results

Post by Ali Tait » Fri Feb 07, 2020 9:03 am

Ray P wrote:
Fri Feb 07, 2020 7:45 am
Ali Tait wrote:
Fri Feb 07, 2020 7:17 am
...which is a good bit cheaper.
Not sure expense was where Wolfgang was coming from Ali, just commenting that the price point is similar to the servo-equipped bass he's been looking at folllowing the SLOB bass loading discussion.
It would be interesting to compare Ray. It's an unknown though, and I already know how well this method works. :D

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Re: Ali Bastanis OB testing & results

Post by Johnj » Fri Feb 07, 2020 9:26 am

The UM18 is the best bass drivers I heard in Vic system without a shadow of a doubt. If you are a bass head they are certainly the way to go with this design. However other bass drivers will work in this configuration. I use the lesser Selenium Neos in an isobaric design and its perfect for my taste in music.
What I found out with the approach was that even using open baffles were adding a certain colouration and going Baffle-less seems to eliminate.
It is a radical approach but a lot of experimentation went into this approach.
I think for most people the limiting factor is the industrial looks and also getting their head around that this approach actually works

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