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Old 17th August 2010, 05:00 AM   #61
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Cool, and congratulations!

Very impressive sensitivity for one box @ 2PI and 2,83 V, actually it is the best I have aver seen from a single box of moderate size, my hat is off.

My own TH's messure 500x550x680mm WxHxD and they aim for roughly the same response and are loaded with B&C's 15TBX100, what are the external dims on these and what driver are you using ?

again, really good work, and thanks for sharing / martinsson
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Old 17th August 2010, 11:12 AM   #62
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Default Reverse engineering artistic cabinets.

JB and other "Artists", to reverse engineer your on the fly or tweaked boxes:
Do the foam trick but in reverse. HD or Lowes pick up 3/8 insulating foam in a 4x8 sheet foiled both sides. Draw the cab profile out with a marker and cut out the pieces.
Then simply lay them out in a straight line and measure them. That should give you really close numbers to throw into hornresp. Perhaps DJK or someone could suggest the best cut points/angles in the corners.
I lay out my boxes that way to start with so I can see what will fit without redrawing it over and over.
Hornresp to straight foam layout, test fit/cut foam to fit profile, tweak reflectors etc, build throwaway with screws and nashua aluminum duct repair tape, tweak away, finalize or actually glue together prototype. If I'm going to build a bunch I might leave the prototype with one side (armacell) openable as a reference.
I have done 100w tests with cabinets built this way along with weatherstrip foam or armacell 1/8 tape. Works best on 3/4" plywood cabs. I often tape up the outside as well.

You can also stick the cut pieces into the box to figure out where things like S2 really wound up in the build. You'll probably find it drifted due to the angles...
Use the heavier Nashua tape as it's easier to remove and it can be used to cover both sides of a screw hole when tweaking. The thinner stuff is a pain to pull off but works almost as well.
I've tested a few boxes at full blast screwed and taped...no glue. Might be tricky with 1/2 inch wood.

Last edited by screamersusa; 17th August 2010 at 11:19 AM. Reason: S2
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Old 17th August 2010, 06:42 PM   #63
tb46 is offline tb46  United States
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Default Drawing for simulation in Post #57

Hi jbell,

This is the sketch derived from your dimensions from which I build the simulation in Post #57. As you can see it is not a finished drawing, and some of the dimension just don't quite meet (in the upper left hand corner they are quite a bit of, but that depends on where you start.)

Anyhow, for what it's worth:

Regards,
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File Type: pdf singlesheet_2_2010_Aug15_dwg.pdf (23.6 KB, 430 views)
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Old 17th August 2010, 09:27 PM   #64
jbell is offline jbell  United States
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Oliver:

Thanks for working on this. Post 56, you can see how I lapped the boards. Here's from memory on my build some notes that will make things line up a little better.
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Old 17th August 2010, 09:57 PM   #65
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I still have only one cube built, so I will switch to this design when I can. About a week ago I fell and broke some ribs. What a bad time to have a vacation scheduled. Hurts to even take a breath!
Jim, what will the cut sheet look like for this one?

Thanks Mike
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Old 17th August 2010, 10:26 PM   #66
jbell is offline jbell  United States
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Mike:
Cut sheet is in post #39, sorry to hear about your ribs. BTW, for your next cabinet, put it on an iron diet.... I only use just enough screws to hold things together till the glue dries, usually 2-4 per panel. Then I remove them and fill holes with PL wood filler.

It was raining ALL DAY today, but I finally braved the rain with a tarp, and went outside for a couple minutes testing @ 28v.

replace all those beautiful 105's with 103's.... (sigh) which is in line with what hornresp says I should be getting. Still 123db@28v1M is nothing to sneeze at.

Cabinet felt relatively solid -- much to my surprise. However with a loss of 2db from 2.83v to 28v, tells me something is vibrating and losses are happening. It's possible that I didn't measure well in the rain... and 105 is for real, but I have much more faith in a 103db number....
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Old 18th August 2010, 01:21 AM   #67
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Looking good JBell! Keep up the good work!
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Old 18th August 2010, 09:44 PM   #68
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Jim:

LOL, I did go a little crazy with the cabinet screws. I use bondo after I remove the screws to fill the holes. I have never seen the PL wood filler. Gonna have to check it out. Hate to mention that I used my air stapler on that cab also. Do you think it was a little over kill? If one screw will hold, 10 will hold better. lol I will cut back the iron.

Mike
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Old 19th August 2010, 07:24 AM   #69
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Jbell, how high can this new design go? do you have plots for 2 / 4 of them.. just out of curiosity have you simmed any other drivers in this? would try my self but Im on a mac so can't run hornsresp

sorry for the all the questions.
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Old 19th August 2010, 02:03 PM   #70
jbell is offline jbell  United States
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Quote:
Originally Posted by CuttaBoi View Post
Jbell, how high can this new design go? do you have plots for 2 / 4 of them.. just out of curiosity have you simmed any other drivers in this? would try my self but Im on a mac so can't run hornsresp

sorry for the all the questions.
I think olivers hornresp is pretty close -- however I always measure lower than what I think I'm building. I read some place on designing FLH, that you need to take into consideration the 'horn bubble' in front of the mouth. Wonder if there is something to that, and that's why my TH's always measure a little lower than I think. For that reason, I've come to design just short of 40hz in hornresp, so that what I build is closer to what I really want.

In terms of how high? I've personally measured/listened up through 200hz in 1hz increments. Other than the 170hz dip (that hornresp predicts, but predicts a much wider in frequency dip) It's smooth up through 200. I'm guessing about 250 is as far as it could be pushed before something starts sounding iffy...

Also, word to the wise... trying to measure over soggy ground over grass in the rain is NOT 2pi space... My driveway measurements at 28v look much closer to my original 2.83v... so I'm not nearly as concerned about panel flex as I was.

I attached a 2.83v 1 and 4 cabinet hornresp response. I think it's pretty close to the numbers I measured. You can see how hornresp predicts 4 cabinets should get you flat to 40. I actually think 2 cabinets will get you there.

It only costs you a sheet of ply and tube of glue to find out if this cabinet is a good one or not, have fun.
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