PERSPEX QUASAR ver 2.0 prototype build

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Nick
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#121 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Nick »

I would argue that me buying a pair of Lowthers is in itself a bit of an odd thing.
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#122 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Dave the bass »

Ali Tait wrote: Sun Oct 25, 2020 10:26 pm Lowthers delivered by Porsche. What’s the DIY world coming to? :D
Filofax, red braces, a huge brick sized phone (with 15 minute call time) and a '1 o'clock appointment with Sebastien in accounts'....back to the 80's? :)
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#123 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Nick »

I generally enjoyed the 80's (what I can remember) so fine by me. Though that was mostly because I was in my 20's in Bradford.
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#124 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

Indeed Nick did drop off the Lowther's Saturday afternoon and (reluctantly) took back home the Lii Audio drivers. We both agreed the best for the Fast-10s drivers was to sell them and place our hope in the Lowther PM6A silver coil wound drivers.

As there was nothing worth watching on TV Sunday afternoon I decided to install the Lowther's into the Quasar cabinets. As previously posted I had made up some mounting plates to cover the larger cut-out hole required for the Chinese drivers. See below:

Image

Image

Originally I hooked the only the Lowther's direct to my 300B amp (no filters) using CD as source and started off proceedings with some simple boy and guitar music in the form of the Sun Kil Moon album Admiral Fell Promises.

Instantly I could discern an immediate difference to the better in the music to the Lii Audio's. These have tone and depth to the music the Lii's lacked. They also appear to have extended FR over the Lii Audio's. So first impressions are very promising. To give the cones and voice coil a gentler bed-in I didn't have the volume up that high and at this lower volume setting they didn't appear to exhibit the dreaded Lowther 'honk'. They do appear to be forward in their presentation but playing them louder and with some telling female vocal recordings will no doubt show this or not to be a problem. But as said these silver wound drivers do seem to be smoother than previous Lowther's I had had to endure. Time will tell. I left this set up on with continuous play for around 4-hours last night whilst I did other things in the house.

This morning I swapped amps to a Rotel Integrated I have that I'd almost forgot I had. They are presently playing some female vocal stuff on CD with a more extended FR than the previous Sun Kil Moon recording. Again initial impressions are still promising, little bass to talk about to what I am used to but cranking the volume up a little still hasn't shown up the 'honk' yet. Though I generally am not like full range speakers and Lowther's in general, these do show promise. Still only another 25-hours run-in as advised by Lowther before I try out the full speakers with the Supravox's hooked up with a series filter.

So, did I mention this set-up has promise? They are a country mile better than those rather dreadful Fast-10s drivers. But a long way to go yet.
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#125 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by IslandPink »

Nice work - promising results.
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#126 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Scottmoose »

That's sounding more promising indeed. I remember spending a while looking over the Lowther range only a week or so before Colin & Nick mentioned looking at a pricier wideband, & the PM6A with the sliver coil (it has to be the silver coil, the aluminium coil has a different response) looked about the cleanest of their current 8in offerings. I take published data with a large pinch of salt, but in fairness, Lowther publish basic FR & impedance responses for all their units, under the same conditions, so the general trends relative to each other should be representative if nothing else. I'm quite looking forward to hearing these at some point.
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#127 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

Ok so now the Lowther's have had around 10 - 12 hours with the last couple of hours playing a couple specialist CD's that Chris (Stratmangler) ripped for me a long while ago. They are labelled 'Speaker Shakedown' (unknown origin) and 'Hi-Fi Choice System Tune-up Disc.

This afternoon I started to wire up the speakers with the first trial series XO. The inductors across the Lowther's I have mounted and screwed to the inside of the front baffle. They are a pair of Monacor frame inductors of values 8.2mH and 5.6mH wired in series to give a total value of 13.8mH which is the nearest I could get to the original 15mH as used by James on the original Quasars. This arrangement allows for some simple and quick change of values by wiring out one of the inductors. The Cap across the Supravox is a Jantzen Audio Premium Elko 100uF Electrolytic, which for test purposes is more than adequate. Some photos below of the one speaker I have wired up to date.

Image

Image

Image

I'm not familiar at all wiring up series Xo'ers so hopefully I have done this correct. I'm sure one you guys will tell me if I have done it wrong.
Anyways onto the second speaker which shouldn't take too long do and then after tea I can sit down and evaluate how they sound.
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#128 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by IslandPink »

If the red wire goes up to the red terminal on the Lowther ( can't see ) then it looks correct.
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#129 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

IslandPink wrote: Wed Oct 28, 2020 5:36 pm If the red wire goes up to the red terminal on the Lowther ( can't see ) then it looks correct.
Indeed it does Mark. So that's a relief I must have it right.

Both speakers are now wired up and ready to be hooked up to my Longdog P6 amps. Thought I'd use these as it would be like a worst case scenario amp wise for a pair of Lowther's. If they sound good with these theory suggests they should be even better with the 300B SET's. Shall be doing this after me tea.
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#130 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by chris661 »

What's the verdict, Colin?
Interested to hear if they play heavy or complex music as well as a more conventional 2- or 3-way design.

Chris
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#131 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Toppsy »

chris661 wrote: Fri Oct 30, 2020 6:04 pm What's the verdict, Colin?
Interested to hear if they play heavy or complex music as well as a more conventional 2- or 3-way design.

Chris
To a large degree YES. That was the biggest surprise about these Lowther's. They don't sound like any other 'honking' Lowther's I have heard before. In stand alone mode on the baffles (no filters) they did a really reasonable job of playing the Bob Marley reggae track we tried on the Lii Audio. Other more complicated/challenging recordings were tried to similar surprising results. No real bass to talk of, but you'd expect that being bolted to a OB. I'd like to hear these in a properly designed back loaded horn which should augment the lower frequencies to an acceptable level. I don't think your die-hard traditional Lowther buyer would like these as they do not suffer the rising response with the associated 'air' to the girl and guitar type music one generally likens to Lowther's and any other similar type 'full'range' driver. But then one has to suffer the Lowther honk with the associated in-yer-face presentation that likely is the appeal to these die-hards.

Yesterday I listened to the speakers as 2-ways with the series XO. Before sitting down for a listen I left them running for a couple hours to help bed-in the new inductors. Initial impressions suggested the Lowther's were dominating the sound with muted lower midrange / bass. After some head scratching I decided to remove the 5.6mH inductor and wire the Lowther's with just the 8.2mH across the binding posts. This redressed the issue and now they were playing a more balanced musical presentation. They are not fazed by more challenging music genres generally associated with high efficiency paper coned 'full range' drivers. Towards the end of the day I wired in my Fostex T90A super tweeters wired with a 2.0uF inline cap and -7dB attenuation dialled in on the adjustable L-pads. Again as with the full value inductors on the Lowther's I found this over balanced the sound in favour of the higher frequencies. This arrangement should give a 1st order XO of just under 10kHz and 98dB sensitivity. Having discussed this with Scott he suggested I change the 2.0uF cap to a 1.5uF to push up the XO frequency. As I don't have any 1.5uF caps Scott has promised to post some to me, so for now I am listening to the speakers without the super tweeters.

So results to date are very encouraging. I'm sure the current series XO arrangement with a 100uF cap and 8.2mH inductor are not fully optimised to the design but until Nick, Scott and perhaps Chris can get together my place to take some actual measures there is little else I can do with these speakers but enjoy them in the current state. Then there is also the play with the super tweeters when the 1.5uF caps arrive.
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#132 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by IslandPink »

I think the AER has Qts around 0.4, the PM6A 0.34 ; also the AER slightly lower Fs ( 40-ish ) the PM6A given as 44.
Altogether that means the AER would roll off lower on OB when unfiltered, than the PM6A.
Hence it makes sense you could get a better result with 8.2mH and 100uF, the crossover is then somewhat higher, which would match the roll off of the PM6A better.
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#133 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by JamesD »

Also the AER Re is 14ohms and the Lowther Re is 6ohms suggesting a better match at around 7mH for the inductor than the 15mH that suits the AER.

Really nice to hear that these are working better in the Quasars - these are affordable!!!

EDIT! A quick fag packet calculation suggests that a 39uF capacitor in place of the 100uF one would work better with the 8.2mH inductor and 6R Re lowthers... any value from 33uF to 56uF should work better ... and smaller would be better than larger... A quick check might be to series connect both 100uF caps on one speaker and listen to that on its own...

ciao

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#134 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Cressy Snr »

Once you’ve got them going.I suggest playing “I Can’t Let Go” by The Hollies at a robust level. It’s one of the best speaker test tracks out there and will tell you a lot. Yeeeeeeeeeeeeeeeeeee! :D
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#135 Re: PERSPEX QUASAR ver 2.0 prototype build

Post by Ray P »

These look interesting and seem to be well regarded...
Aurel Bryan FR units.jpg
Aurel Bryan FR units.jpg (3.46 KiB) Viewed 4234 times
Sorry, I couldn't resist!
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