i have drivers what can i do with them ? - Page 2 - diyAudio
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Old 24th July 2005, 08:15 PM   #11
GM is offline GM  United States
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Greets!

>i would like to use the same speakers for center and main l and r
i dont really have the budget right now so i will probably stay with the one that i have althought i know it would be optimal
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OK.
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>of course i have to use a sub what self respecting diyer hasent built a sub or two i have 2 in use now and i think i have a new angle on the 1/4 wave if you are intrested ill send you a few pics and how i did it i havent found anything like them out there
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A new 'angle', eh? Please do.
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>so if i do a tl keep the length the same and double the CSA?
is SQRT squareroot?
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Correct, right.
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>how do i supress the 3rd harmonic i havent heard of that and dont know what you are telling me to do can you lead me in the direction to do some reading about this
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Probably because it's apparently not considered a design consideration by anyone but me, and since I've never compared any of my designs with the more popular driver at top layout, it may only be in theory so just locate it either wherever you need it to be or what yields the flattest sim.
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>i just dl the mjk worksheets and havent really figured them out yet
any help would be greatly appericated

thanks a bunch
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You're welcome! Well, you haven't come back with any Qs, so I assume you've figured them out.

GM
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Old 25th July 2005, 02:17 AM   #12
lolojr1 is offline lolojr1  United States
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well lets see on the new angle on a t line ....
it might be but i will probably have someone tell me its more of a ported box

first what i did was found a 12" piece of pvc pipe about 10' so i could cut it to length and have a left over to build 2 stereo bass!!
then i got out my old cerwin vega 12" xl the ones with the red surround

i built a box that is about 40 " long by 12.5" square and slipped a pice of pipe 28" long inside it leaving one end closed and one open with a speaker mounted in the end of the pipe

so it gives me 4 small rounded triangle ports and a wavelength of the tuning frequency from the speaker to the end of the port

this gives me a verry nice sounding box tuned to arround 35-40
and if my calcs are right and 1/4 of that is the length of the box times two from the speaker to the back of the box and from the back of the box to the end of the port


well if its not right it could be that i havent really measured them in a few years and i was just starting to learn about transmission lines when i built them


i dont have a pic if you want ill take one and email it to you

and last but not least what file do i use to model a transmission line on mr kings spreadsheet ?
the mltqwtl? the closed end tl?......
im not really sure what style to go with ?
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Old 25th July 2005, 02:21 PM   #13
GM is offline GM  United States
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Greets!

Hmm, I can visualize this more than one way, so not sure what you did, but if you have a long line with a terminus whose cross sectional area (CSA) is <the pipe's, then you have a ML-TL, a cab style that I've used since the late '60s and which has gained popularity with the advent of MJK's work. I would like a sketch of the design if you don't mind so I'll know for sure what you built.

If you want to do a ML-TL (TL with vent), then use the ML-TQWT WS if bottom firing, otherwise use the PORTED WS for all other vented designs. For TL, I just use the 'offset driver in an open ended TL' WS. It doesn't calc the terminus's end correction, but the extra pipe length is inaudible and the 'SECTIONS' WS required to complete the calc is more trouble than it's worth unless you want to calc a multi-folded or flared/tapered design like he designed it for. He also has a WS for a true end loaded pipe, but few folks actually build them and anyway, his 'offset' WS creates the same plots if you input the driver's location at 0.001.

WRT what 'style' to go with, that's a personal choice based on your performance goals, the driver's specs, available space, etc..

GM
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Old 26th July 2005, 01:55 AM   #14
lolojr1 is offline lolojr1  United States
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here are some pics
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Old 26th July 2005, 01:59 AM   #15
lolojr1 is offline lolojr1  United States
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that one was with it laying down on its side usually i stand it up on a base about 4" tall this one is a close up of the port length inside the box
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Old 27th July 2005, 03:14 PM   #16
GM is offline GM  United States
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Greets!

OK, you have a pipe that has a bit more CSA than the driver 'dumping' into an acoustic 'chamber' which terminates into four long, smaller CSA vents. If we ignore the chamber, it's technically somewhere between a BR and ML-TL since its aspect ratio is too long to be a true BR, yet not long enough to have any TL properties in its tuning BW, but the chamber creates an acoustic low pass filter, so in audio parlance you built a bandpass box of 'x' BW tuned with multiple vents, AKA a muffler with multiple exhaust pipes.

For narrow BW apps such as a sub, a good performing, space efficient design actually, but then you already learned this by doing, rather than just theorizing. Since BPs literally go back to the earliest days of sound reproduction and your basic layout has been used before, no new 'angle' unfortunately. As the designer/inventer Tom Danley has opined on several occasions, "the ancients keep stealing all my inventions."

GM
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