PERSPEX QUASAR ver 2.0 prototype build

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Ali Tait
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#61 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Ali Tait »

Not sure I’ve heard silver ones, do they still have the Lowther shout?
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#62 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by JamesD »

Crickey!!! I hope it doesn't sound like it measures!!!

That recessed mid-range looks horrible its 5db down from the average level each side of it and right in the middle of the voice critical frequencies - how do you correct that without a rotating phase shift and corresponding variable group delay???

The bottom end dies well before the motor hits resonance so its difficult to equalise the LF and that means the bottom end helper has to run higher in frequency range than the Quasar normally supports - the distance between the two drivers may become noticeable - let alone matching the tone between the drivers in the critical voice band...

Not saying its impossible to make work but it needs more thought and work than a 'normal' job would.

If the Lii Audio has sufficient detail and tone from say 200Hz to 8KHz then I would stick with it and add a super tweeter at the top end.. The Lowther needs this too...

At the price of the Lowthers why not reach for the AERs???
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#63 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by steve s »

I have a pair of pm6c's along with other lowthers, they sound very well. Ed was impressed when he heard them as I remember..
I'm sure the lii's will sound ok once run in
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Nick
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#64 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Nick »

At the price of the Lowthers why not reach for the AERs???
The Lowthers are £550 each
The AER BD1 £2060 each
The Lii are on sale at £398 each + shipping and customs.
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#65 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by IslandPink »

Exactly .
The other ones I looked at were the Enviee 8" by Joachim Gerhardt, but I don't really think they are available any more, big shame, they looked excellent.
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#66 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by JamesD »

Sorry I thought the silver wired PM6a were a lot more than the standard PM6a...

Wrong again James :oops:
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#67 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by chris661 »

Nick wrote: Fri Jun 12, 2020 6:08 pm Another option for the full range driver was suggested by Scott, Lowther pm6a wilver would. What does the panel think?

https://lowtherloudspeakers.com/wp-cont ... f/pm6a.pdf
If I was looking for something to cover a couple of hundred Hz upwards, I'd be looking seriously at small-ish PA coaxials.

They've got the efficiency to match the esoteric full-range drivers, but will:

1 - Actually make it to 20kHz
2 - Hold up better when you throw some power in there
3 - Be flatter through the midrange

The expense would be making it a true 3-way system, with the compromises that would entail.

I think it's an avenue worth exploring (otherwise I wouldn't mention it), and I think the Faital 8HX230 is a good starting point.

I've done quite a lot of work with the 10" version - graph below of a measurement I did fairly recently. The phase curve fits within a 135-degree window from 200Hz up to 15kHz, which is decent, and the frequency response is streets ahead of the published (read: approved by the marketing department) curve for the Lowther driver.

Chris
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#68 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

If I may be so bold, that if we are talking about small-ish PA coaxials may I suggest the Monacor SP308CX and/or SP310CX? These have the efficiencies to match to the Supravox but don't have the same 'signature' sound of the high efficiency light weight paper coned 'full range' drivers of the likes of the Lii Fast-10s that draws folk to this type sound. But then they do not suffer the whizzer issues that most (if not all) these type drivers generally suffer. Just a thought.

Still I am hoping to arrange some measuring of these Lii Audio drivers done, lockdown conditions allowing, so we have some more accurate info to work with other than the suspect official published data and FR plot. So quite a way to go first with the Fast-10s before Nick considers a mid-high replacement driver, if at all.
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#69 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by chris661 »

Comparing datasheets (I know, not the full story) but the Faital 8HX230 has demodulating rings (lowers motor-borne distortion and lowers VC inductance) while the Monacor's HF driver has a fairly large dip 7-9kHz.

The Faital unit is one of their latest and greatest, and is priced accordingly, but still cheap compared to the Lowthers and AERs that are also being discussed.

I've only worked directly with the 10HX230, and would be willing to demo those as lockdown measures ease.

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#70 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Paul Barker »

I’ll come
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#71 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Nick »

Chris and Colin have been doing some measurement. Normal conditions, in room, etc etc. This is just the Li Audio driver on its own, no crossover.
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#72 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by ed »

I know I'm being picky..but:

what was the software
what was the reference voltage
what was the distance
what was the mic

I only ask cos in all the time I've been measuring I've never seen plots like that...if all the measurements were taken with no changes to the room setup...
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#73 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

Ed,
Chris is presently driving back home to Sheffield but I have spoken to him regards your queries and he has promised to answer them all when he is back and settled at home.

I personally don't have the answers for you other than it was Chris who did all the measuring with an omnidirectional mic and his software and the drivers installed in the test OB Quasar baffles and that all the attached FR plots were measured at 1m distance. We did some measures at 3m, but I don't think Chris emailed those to Nick. Both the Lii Audio drivers at Im distance measured near on identical.

In comparison here is a copy the manufacturers published FR plot and measurements for the Fast-10:
Image

Looking at that and the results we got either we have made a big cockup with our measuring or the official published data is not to be believed. Let's await and see what Chris has to say first, hey.
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#74 Re: PERSPEX QUASAR ver 2.0 prototype build

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ed wrote: Wed Aug 26, 2020 4:53 pm I know I'm being picky..but:

what was the software
what was the reference voltage
what was the distance
what was the mic

I only ask cos in all the time I've been measuring I've never seen plots like that...if all the measurements were taken with no changes to the room setup...
Hi Ed,

Your questions are fair to ask, and I'm happy to answer them.

In order:
- REW
- Not sure, but likely less than 1V. The absolute SPL is not accurate, but the speaker level was well above ambient but definitely not close to being pushed hard.
- A couple of different measurement distances were used. Mostly around 3', and a couple were taken at about 7', but the room is a much bigger factor at the larger distances so there's a lot more "fuzz" on those. I didn't have a tape measure to hand, but those are the rough distances.
- Beyerdynamic MM1, pointing directly at the speaker. Beyer's calibration sheet suggests it's about 1.5dB up at 20kHz when used on-axis, which is the result of a smooth rise starting at 10kHz.

The soundcard was a Behringer UMC202HD, which is adequate - they're a couple of dB down at 5Hz and 50kHz.


I must also note that the speakers did sound like that curve. You could almost get away with it on small-scale acoustic stuff, but Bob Marley was switched off before the first chorus, and I'm not even kidding.

The other Fast-10 measured very similar to the first, so at least they're consistent. Looking at the impedance curve, there's a bunch of little peaks in the 8-10kHz region, suggesting a series of resonances around there which culminate in that rather hideous mid-treble.

Bringing in the Supravox driver with the series crossover brought up the lower-mids and bass (as expected), but there's no getting around that kHz range. Given that the measurement taken from the rear of the driver looks much more palatable, I'd suggest that some modifications to the whizzer may be worthwhile. Something like polyester stuffing between the whizzer and main cone may dampen some resonances

Happy to answer any further questions.

Chris
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#75 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by IslandPink »

Yes, those curves are pretty disappointing. Hmmm..
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