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Multi-Way Conventional loudspeakers with crossovers

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Old 16th March 2007, 12:47 PM   #11
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This is interesting Scotmoose.
Do you have a design that we can look at?
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Old 16th March 2007, 01:53 PM   #12
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Which -Short Thor?

As drawn by Dave:
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Old 16th March 2007, 04:18 PM   #13
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Dublin,
My reason for asking earlier about cabinet volume is because I read (somewhere...can't remember exactly where now) that 5%or less cabinet volume would not affect the way the drivers perform, as they are probably out of spec (with each other) by that amount or more. The speaker design is not sealed or bass reflex and I have kept the baffle cross-section area and size the same. I have kept the volume (as best as I could) to within 5% or less of the specs provided by Mr. Moose. The crossovers will be build to stock specs but with HI-End components, better than the parts used on the upgraded Xovers offered by Madisound / PE. In the end I hope they sound better than the original design by Joe D'Appolito.

Mr. Moose....
I hold you personally responsible for my intrest in the "Thor" project....well, you and Dave.
Your efforts are appreciated, especially by those of us who have taken on the construction of these wonderful speakers.
I have modified the cabinet to resemble the Volent floor standers as they have been approved by the highest power in the house....WAF.
Cabinet volume was recovered by extending the rear of the cabinet 3/4" and not including some of the bracing in your original drawings of the "Small Thor". Hence my earlier photos of "Swiss Cheese". Bracing is accomplished by 5 ribs horizontally and 3 verticle "spines", the front baffle will aid in stablizing (sp?) the front between the ribs, the main spine contacts the rear wall as well as the rear of the front baffle, I will post picts.
If you see something I'm doing wrong please speak up.

Thank everyone for their intrest and input.
Ron
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Old 16th March 2007, 04:31 PM   #14
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Volent:
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Old 16th March 2007, 05:04 PM   #15
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Sounds good -let us know how you get on & if we can help with anything.
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Old 16th March 2007, 07:10 PM   #16
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Thanks Scottmoose
Please can you explain how the MLTLs or MLQWRs work (the theory)?
This design looks like a bass reflex to the uneducated (me).
Does this design cure the Thor's LF problems that you spoke of.
Best wishes.
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Old 16th March 2007, 08:26 PM   #17
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Oh yes. LF will not be a problem Seriosuly though, extension, but no boom -I shaped the FR to roll off in step with average room gain. Expect grunt to the low 20Hz region from Short Thor providing the room supports frequencies that low. Re the difference between MLTLs and BRs, I've covered this a few times in other threads, but briefly:

An MLTL (or MLQWR to be more accurate) is a straight QWR. By restricting the area of the terminus by means of a port, you create an air-mass which resistively loads the quarter-wavelength resonances generated by the line. This does several things, the most significant of these being a) it lowers the fundamental resonance of the cabinet, and b) reduces ripple in the passband. There's more to it than that of course: for a full-dose of theory, go to my friend Martin King's site: www.quarter-wave.com and have a read of his white papers and projects. You'll find the documentation of his Project 2 ML TQWT particularly useful. Also, Bob Brines has some useful articles on his site: http://www.geocities.com/rbrines1/

Hope that helps
Scott
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Old 16th March 2007, 10:14 PM   #18
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Quote:
Originally posted by dublin78
[B]Hello
You can change the shape of the cabinets as much as you like (baffles may need correction), but at the end of the day the cross-sectional area of the line needs to increase/decrease along the line according to the designers specification.
And that is the problem with original Thor... the cab was designed using Augspurger's (scanty) alignment tables and then the cross-section was arbitrarily reduced by a 3rd which ended up giving a (properly) measured response only down to ~100 Hz.

dave
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Old 18th March 2007, 05:23 PM   #19
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Default Another layer Another step closer

I purchased 1/8" bendy ply for the last layer as a base to adhere the cherry veneer. While scrounging around the mess I call my garage I came upon a roll of 1/16" bitumen, which in the trades we call Bitchathane. If you have ever tried working with this stuff in hot weather you know how it got it's name. This particular version is sticky on one side only (some are both), so I tested a section to see how it would react to contact cement. I applied a thin layer to the non-sticky side and a thin layer to a scrap piece of wood I had just layin' around. After they both dried completely I clamped them together on my workbench. I came back and tested the adheasion about 15 minuites later. Oops. I should have put paper underneath the Bitchathane. I tore a layer of wood off the Bitchathane seperating the two and then spent the next 5 minuites with acetone removing the sticky tar mess that was stuck to my workbench! Well, at least I have a good seal.
It was 81* here yesterday, so I let the speakers sit in the sun after applying the Bitchathane and then gave them a good rub down with a scrap wooden block to ensure complete contact with the previous 2 layers of 3/8ths plywood. Man...that's some nasty stuff. I applied a healthy layer of contact cement on both the Bitchathane and the backside of the 1/8th bendy ply and let them dry. With the help of my neighbor we attached the smooth bendy ply over the Bitchathane and again pressed it down with a scrap block of wood to ensure reliable contact over the entire surface. At one point I (foolishly) attempted to remove the ply, only to crack it about 6" up, it was stuck back down with no problems again. OK, I guess everyone has to learn this lesson.......once.
I strapped the cabinets just for good measure and shot the 1/8 bendy with 5/8 pin nails just cause thats how I am. Overkill is my friend.
I have attached a couple of pics just to show progress. I must say that for only a 1/16th layer of Bitchathane the cabinets sound has changed to a thwump instead of a knock when struck with knuckles, I am impressed with the difference. Baffle width is now Exactly 9".
Ron
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Old 18th March 2007, 05:26 PM   #20
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Default another picture

Just had to post this one. With speakers from Denmark, Plywood from Italy & The States, these speakers should be able to sing in any language equally well.
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