audio-talk

This version of the Quasar OB speakers was originally designed and penned by James way back in November 2002 and is something NickG our host has been contemplating for a number of years. I got involved in building some test mules for Nick just before the lockdown and it wasn't until the beginning of this week that I managed to place an order for CNC bandsaw cutting a couple sheets of 18mm chipboard to start the build. James' design calls for 20mm acrylic but our test bed purposes 18mm chipboard is perfectly suited. For those interested in the design I have posted aa copy of James original sketch below:



It should be noted there are a few dimensional errors on this sketch that James is aware so he may update the drawing. In the meantime the upper rear dim of 65cm should read 75mm, the from upper slope directly above AER driver should read 30cm not 20cm as shown. The other couple of errors are the driver cut-outs are shown as radius dims whereas these are actual diameter cut-out sizes. I have a CAD file I'm prepared to share with anyone interested.

It should be noted that Nick's driver choice is: Supervox 285 GMF+ Lii Audio Fast-10s. I had to slightly alter the position of the Fast-10s driver on the front baffle since it is larger than the penned design AER Mk1. Our own Scottmoose has designed a conventional XO for the above drivers and also a series XO to mimic the conventional parallel one. Should make for interesting comparisons.

Anyone contemplating building a non-Perspex pair these OB's will need to have access to a table saw with angle cut capability, or source someone with a 5-position CNC router. If a straight cutting (i.e. 90-deg cutting head) CNC router is available it would certainly make life easier having the side panels machined. One can quite easily see that the design shape lends it perfectly for Acrylic.

Here is a photo of the final set of cut panels for a single speaker:





I took the second photo of the driver front baffle to prove the holes are actual circular and not elliptical as seen in the first photo!

And in good old Blue Peter fashion, here is one I completed earlier:







So onwards now to complete the second mule. More to follow.

what is the tailplane and fin for Colin?

That was added for additional stability when performing a Immelmann - whilst doing the inverted half turn off the top of the half loop without the tailplane and fin excessive yaw could tip the speaker into an unrecoverable flat spin....

Great to see those plans again an to see a Quasar being built - rally keen to hear what the Lii Audio driver can do!!!

JamesD wrote: ↑Sat May 30, 2020 5:35 pm

Great to see those plans again an to see a Quasar being built - rally keen to hear what the Lii Audio driver can do!!!

I'll second that James.. they look good Colin..

JamesD wrote: ↑Sat May 30, 2020 5:35 pm That was added for additional stability when performing a Immelmann - whilst doing the inverted half turn off the top of the half loop without the tailplane and fin excessive yaw could tip the speaker into an unrecoverable flat spin....

Great to see those plans again an to see a Quasar being built - rally keen to hear what the Lii Audio driver can do!!!

without the tailplane and fin excessive yaw would be the last of my worries......

tip the speaker into an unrecoverable flat spin

no worries about this anymore..I've discovered vectored thrust....magic unless you're deadstick.

ed wrote: ↑Sat May 30, 2020 5:03 pm what is the tailplane and fin for Colin?

Ed,
The tail plane is for a RC conversion of a 1930 free flight design "Jasco Flamingo".
I had started this build, oh some 12-years ago, perhaps longer. It's been up in my loft collecting dust all these years so with lockdown and a renewed interest in RC modelling I have resurrected the build. I had built the basic fuselage and tail plane as per plan and covered these in vintage solartex. However, over time the tail plane warped so I uncovered it and added the extra cross bracing from my structural engineering college study times in the 1970's to engineer out the induced warp. Just need to recover it now.

Some basic info:
Design originally published in the 1938 Jasco yearbook.
Designed by Roger Hammer
Tail plane length 80cm
Tail Plane root chord 30cm
Wingspan 226cm (89")
Wing root cord 38cm
Fuselage length 145cm (57")
Proposed power plant, Saito 45s 4-stoke
3-channel RC (rudder, elevator, throttle)

I shall be starting a new thread on the build elsewhere. Wasn't sure of any interest on here?

The Quasar development is great - I've been waiting to see what Nick was going to do with the Lii drive units - mine are still sitting in their boxes.

Looking good Colin.

Interesting about the plane too.

phwarr

Very good indeed. Are the final ones going to be all-Perspex ?

JamesD wrote: ↑Sat May 30, 2020 5:35 pm That was added for additional stability when performing a Immelmann - whilst doing the inverted half turn off the top of the half loop without the tailplane and fin excessive yaw could tip the speaker into an unrecoverable flat spin....

Ha! Sounds similar to...erm.....are you familiar with the Captain Lockheed and the Starfighters album per chance James?

IslandPink wrote: ↑Sat May 30, 2020 7:45 pm Very good indeed. Are the final ones going to be all-Perspex ?

Well now I believe that is Nick's intentions. It all depends on how these test mules perform. Plenty of experimentation for us to play with once I've finished the build. Hence the cheap and cheerful 18mm chipboard. Which sonically is better than MDF for similar cost.

Bob Calvert!!!

"The right stuff baby, the right stuff!!!"

DTB shoots and scores again...

You know that I'm going to have to get that out from the store and play it again...

awww forgive me...

the last time I heard that was 1973 or 4, stuck in a caravan in Wells next the sea when it rained for a whole weekend. One of the chums insisted on playing it over and over and over and.......one of the other chums insisted on playing tales from topographic oceans......I haven't listened to either since....on reflection one chum passed last year and the other two years ago.....c'est la vie, or not...

edit will that saito be big enough Colin?

ed wrote: ↑Sat May 30, 2020 9:11 pm
edit will that saito be big enough Colin?

YES it should be. Projected all up weight is 5.5lbs to 6lbs and at that with a Saito 56 (3-channel RC conversion) the plane is reported to take off in a few feet and fly around on just over tick-over revs. If not I have a Saito 50 and also a Saito 65.
As said to avoid further off topic posting on this speaker thread I'll start a new thread in the morning in general section.

OK chaps back on topic this morning I mounted the drivers to the finished speaker. Not yet hooked them up to an amp but I might just hook up the Fast-10s to one my Longdog P6 amps just to help bed it in and make sure it is OK. Later I'll do the same with the Supravox. Here aresome photos of the mounted drivers:









Right I'm now logging off to start gluing up the second speaker.

Edit:
I have to say I am a little disappointed in the finish and look of these Lii Audio drivers. The surrounds are translucent and so the frame shows through in the light. They also have the appearance they have been languishing in some warehouse for a few number of years giving a faded and dirty appearance to the paper cones. Perhaps this is the intention of the makers to make them look as vintage Coral drivers? I don't know but doesn't work for me. Lets hope they sound a lot better than a lot of true vintage FR drivers I have heard in the past and wondered what all the fuss was about.