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Old 14th October 2005, 03:45 PM   #111
Byrd is offline Byrd  South Africa
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Of course that is true, not many people here would be able to afford to build the Thor's.

I guess I am one of those "privileged" white South Africans that I am sure you have all heard / seen reported in the press all these years. I am in fact so overadvantaged that the goverment has seen fit to disallow me ( as a "white" citizen ) from being a part of incentivised investment programs. As a stand against this I have disinvested from South Africa and as a result had a bit of spare cash to fund this project.

I'll test the various configurations that have been suggested though I am not sure that I will be able to measure anything effectivley for you. I will need to be getting some measuring equipment soon. I have heard a Behringer mike being recommended here. Thoughts on this?
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Old 14th October 2005, 07:24 PM   #112
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Quote:
So = 2.5 Sd (just under actually: 13.5"x7.5"). This will make for a cabinet that's around 3.25" shallower than the FatThor overall, which is useful, though it's never going to be a small cab!

<...>
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Scott
Planet10, would you adjust your drawings? BTW - what do you use? AutoCAD? Thanks for metric measurements!

Scott, did you change anything in crossover when you generated response chart?

Another questions related to the drivers' position - after moving vent down, and leaving drivers in the same location, sound (air pressure, *shrug* - I'm not professional here, so sorry for the terms) inside the cabinet don't pass through whole stuffing when it goes towards the vent. How does this affect final result?

As well, Scott, does your calculation take such details? as I understand you are writting thesis about those calculations...?

Finally - keep doing good job, guys.. I'm tracking this thread and I'm very curious to see the final result. Never know, maybe I'll build them one day...
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Old 14th October 2005, 08:41 PM   #113
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Quote:
Originally posted by Scottmoose
Line length, geometry and driver positions remain as per the FatThor CAD drawing above.

So = 2.5 Sd (just under actually: 13.5"x7.5"). This will make for a cabinet that's around 3.25" shallower than the FatThor overall, which is useful, though it's never going to be a small cab!
beta 1 attached. To keep the bend consistent, the partition is a bit longer & the box a bit shorter (18mm & 18mm). Once up on pedistals it is going to be even more imposing...

dave
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Old 14th October 2005, 09:01 PM   #114
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Carpentry becomes a bit tricker, but to improve the visual impact... no pedistal required.

3.5 degrees makes them good for 8-12' optimal distance. 6-16' a tad less optimal

dave
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Old 14th October 2005, 09:07 PM   #115
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perhaps instead of "Fat Thor" it could be renamed "Falstaff" -- the fat, jolly knighted companion in Henry IV, Pt 1 -- it is apparently going to be a project of good cheer.
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Old 14th October 2005, 09:56 PM   #116
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Quote:
Originally posted by jackinnj
it could be renamed "Falstaff"
A better name would be a good thing, especially if someone is going to build one.

dave
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Old 14th October 2005, 11:02 PM   #117
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Quote:
Originally posted by tamosius


Scott, did you change anything in crossover when you generated response chart?

Another questions related to the drivers' position - after moving vent down, and leaving drivers in the same location, sound (air pressure, *shrug* - I'm not professional here, so sorry for the terms) inside the cabinet don't pass through whole stuffing when it goes towards the vent. How does this affect final result?

As well, Scott, does your calculation take such details? as I understand you are writting thesis about those calculations...?
My thesis is actually on 20th century naval history, and acoustics used -sonar, range-finding and direction finding etc. You'd be surprised how relevant much of it is to speaker design (no kidding). When it's completed, I'll stick it up on the web if the University lets me.

Crossover is assumed to be the same -it doesn't affect the MathCad response anyway as it only kicks in above the 1Khz limit of these charts. Above that, it's only the drivers that are contributing, the cabinet shouldn't be doing anything other than providing them with a rigid home.

The stuffing is another issue however, and a fair point. It's only really there to damp the higher harmonics -forget that nonsense about fibres moving and affecting the speed of sound etc, so the positioning isn't particularly critical in this respect. It's the driver position / distance from So that's more important. Ultimately, the quarter-waves generated in the cabinet should pass through all the stuffing anyway, so no worries there.

I said the above was my last -well, OK, I couldn't resist. Sorry Dave! Final thoughts: a straight pipe is at last possibly on. So & Sm = 3.5Sd. 45" pipe length. Tweeter centred at 0.35% pipe length from top. Vent is circular and 3"x6" (WxL). Close to a BR box, but not quite -it's still a TL. Stuffing density 0.5lbs to the cubic foot. Stuff from the top to the half-way mark, or just beyond.

The response is rising slightly below 100Hz -that isn't going to be too much of a problem however, and I doubt boom will be an issue, bacause we'll loose that rise through baffle-step loss. It should be pretty flat overall. And, it's a simple build. I prefer the response of the FatThor variations above frankly (love those drawings Dave, especially that last one!), but this isn't that bad either.

Best
Scott
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Old 14th October 2005, 11:24 PM   #118
SCD is offline SCD  Canada
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Default Design comments

Hello Folks:
I though I would offer a few thoughts regarding the construction of these cabinets. The size of the baffles has me a little concerned. I think a significant amount of bracing should be included in the design. I recommend 1/2 in thick plywood that has been drilled out significantly to be mostly holes. I woould put this at the mid point across the front baffle for the top half of the cabinet then repeat it on the bottom half for the front section.
This brace could be easily cut out for the drivers to act as a driver brace as well.
I think Dave knows what I am suggesting, it worked very well on a set of WR125 bipoles I made. Perhaps Dave can comment.

Bracing is really going to be needed the more the better!

I also recommend 1.5 in or so legs off of a slightly oversized base if the bottom vent design is chosen.

I have built with a slight lay back angle, it is a little tricky but definitely worth the effort.

Hope this helps
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Old 15th October 2005, 01:57 AM   #119
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bacause we'll loose that rise through baffle-step loss.
The original crossover is already compensating for the baffle step as long as you keep the baffle width the same. The Seas anechoic measurement is remarkably flat above 200 Hz and Bjorn's close-mic'd measurement clearly shows the baffle-step compensation. The bass is the only thing that needs to be fixed.
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Old 15th October 2005, 04:46 AM   #120
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Default Re: Design comments

Quote:
Originally posted by SCD
1/2 in thick plywood that has been drilled out significantly to be mostly holes. I woould put this at the mid point across the front baffle
Not in the middle!! It needs to be offset enuff that the 1st bending mode is killed instead of enhanced.

I wouldn't have built the thors without adding bracing. This box is bigger.

dave
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