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Post by keith1962 on Mar 24, 2016 20:31:04 GMT
Looking at the Perspex and in light of John's comments about isolating the drivers within the baffles, has anyone experience of using Panzerholz to make the baffle? It would be expensive and extremely difficult to cut neatly with regard to circular holes but as an isolating sub structure there is not much better out there. I re-plinthed my Notts Analogue Mentir Ref in 25 mm and 12.5mm Panzerholz and it was a definite improvement but working with the 25mm was very difficult indeed!
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Post by pre65 on Mar 24, 2016 21:03:24 GMT
I can't be the only one never to have heard of Panzerholz (can I ?) so here is a link. 
www.ltlewis.co.uk/b15.htm
It says the material is "easy to work". 
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Post by Greg on Mar 24, 2016 21:11:18 GMT
Sorry, I can't really answer the questions posed with any knowledge because personally I have never gone down the Open Baffle way. My listening room isn't big enough and the Mrs wouldn't accept them. I have enough problems in that respect as it is!
My understanding is that Perspex does have sonic benefits over wood or MDF, and certainly the Quasars sounded very transparent and revealing of micro detail compared to other baffles to my ears, but that is an extremely subjective observation as none of the baffles I've listened to have been built with the same drivers. James Doddington who designed the Quasars was a design engineer in the industry and certainly knows his trade, albeit he has for several years now diversified in to other work.
Sorry, I really can't help further although if you were to join Audio-Talk and pose questions there, I'm sure you'd get a much more satisfactory response.
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Post by keith1962 on Mar 24, 2016 23:21:12 GMT
Well what they say and what is reality is quite different as far as easy to work is concerned!! Trying to cut a straight line in the 25mm sheet I have with metal blades in my jigsaw proved very difficult and I gave up in the end. I had to use a diamond blade for cutting metal in a circular saw, and wouldn't even attempt a curved line!
Has great isolating properties though due to the resin impregnation and heat and compression treatment.
Keith.
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Post by keith1962 on Mar 24, 2016 23:25:52 GMT
No worries Greg, tons of interesting info there! That wiring to the rear of the drivers certainly looks interesting, can't beat a few croc clip connections!! At least it's not mains voltage!
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Post by Sovereign on Mar 25, 2016 3:48:35 GMT
Well what they say and what is reality is quite different as far as easy to work is concerned!! Trying to cut a straight line in the 25mm sheet I have with metal blades in my jigsaw proved very difficult and I gave up in the end. I had to use a diamond blade for cutting metal in a circular saw, and wouldn't even attempt a curved line! Has great isolating properties though due to the resin impregnation and heat and compression treatment. Keith. Just as a pointer, to cut 25mm of anything with a jig saw would be difficult to get lines correct. I would say a router would be the only way to cut anything accurately like this. |
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Post by Eduardo Wobblechops on Mar 25, 2016 5:05:09 GMT
From what Mark has said the perspex removes a slight thickening in the upper bass and he preferred it over birch ply. I'd go for birch ply over MDF personally, but acrylic over both.
I run active OB's made with ply, however I've bought some acrylic to make some new versions with some other drivers I have. When I can get the time to get round to it..
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Post by pre65 on Mar 25, 2016 8:53:32 GMT
I've got a full sheet of BBP (Baltic Birch Ply) in the hallway waiting for me to rebuild my OB speakers.
One day it will get done.
A friend of mine used Trespa for smaller projects, his employer had stocks in their "chippy" workshop.
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Post by keith1962 on Mar 25, 2016 9:17:27 GMT
Those Perspex ones do look very nice! High WAF imho. Is there any benefit to be had sound wise from front mounting the drivers, front mounting with the driver in a rebate or rear mounting? Keith. So any views on how best to mount the drivers or is it mainly aesthetics? Keith. |
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Post by Sovereign on Mar 25, 2016 10:50:21 GMT
As you can see my baffle is made from two sheets of baltic Birch ply laminated together. The mid driver is mounted 12 mm off the baffle and the tweeter is 6mm as per the designers spec. This speaker was designed with a passive xover in mind, although in time I plan to go active.  |
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Post by keith1962 on Mar 25, 2016 15:26:14 GMT
They look very nice, love the rounded edges. So those baffles are 2 x 18mm bonded together with additional 6mm or 12mm under the drivers? How did you do the edges and the bonding? I suppose the designer did that for time alignment purposes which is not such an issue for me as I will be able to do that actively. My intention is to build something like those but with a 2ftx2ftx2ft open backed box at the bottom for the 18" bass driver. John's comment about isolating drivers from each other has made me rethink my intention to have one baffle front with the mid and tweeter in an extension of the front face of the U frame. I am now thinking the baffle for the mid and treble will be a separate free standing structure that will be fixed by screws to the top of the bass unit, with baffles in alignment, and 5mm sheet of sorbothane sandwiched between. Will also look at making some sorbothane gaskets for each driver with all drivers surface mounted like yours Sov.
Keith.
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Post by Sovereign on Mar 25, 2016 15:38:32 GMT
Hi Meith
Yes the two sheets of Baltic Ply are glued and clamped together, all cutlets were with a router, a router will give you an exact finish and will cut any shape you require, you just need a jig for it.
You can't see it from the pictures but my bass driver , Eminance Alpha 15, is at the bottom of the baffle with a large open open backed box on it.
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Post by Eduardo Wobblechops on Mar 25, 2016 16:21:34 GMT
Pic of mine. Simple two way run actively with a miniDSP. Twin Eminence Alpha 15" bass helpers, Visaton B200 wide range driver. Added Tannoy supertweeters which give some added sparkle to the top end-  |
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Post by keith1962 on Mar 25, 2016 16:38:30 GMT
Sov, that sounds spot on. Which glue did you use and have you braced and used wadding inside the back bass box? Is the bass box double skinned like the baffle?
Keith.
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Post by keith1962 on Mar 25, 2016 16:40:51 GMT
Ed, that looks very nice. What really gets me is the simplicity, and the ones that I have heard sound so good (small sample of two admittedly!).
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Post by Eduardo Wobblechops on Mar 25, 2016 16:43:10 GMT
Yes, easy to build, and the sound quality for the outlay is unbeatable IMHO.
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Post by John on Mar 25, 2016 20:58:34 GMT
Agree this is where OB really win you have to pay a lot of money to equal them with traditional speakers
Keith isolating helps but its not essential but agree with Darrell of Hawthorne that it makes a difference
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Post by canetoad on Mar 25, 2016 23:26:38 GMT
I've heard Ali's speakers several times and they sound great. Rock solid soundstage and the speakers actually do disappear. At some point I want to build a pair myself.
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Post by Eduardo Wobblechops on Mar 26, 2016 22:23:55 GMT
Cheers Bernie, yeah I like what they do, though I have a new pair in mind.
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Post by keith1962 on Mar 27, 2016 9:36:45 GMT
Are there any guidlines for the size of the open backed box behind my 18" driver and I presume it should be braced and lined with wadding of some sort?
Keith.
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