Hi all,
I have been looking around for some theory to build a pair of MTM speakers but there does not seem to be a good site where design concepts are explained. On this forum, there is info but in bits an pieces.
Can anyone suggest a good website where I can start? I mean sites that explain about the driver placement on the baffle, how much spacing is needed, crossovers and related stuff. I will be grateful for any leads.
Thanks,
Vivek
I have been looking around for some theory to build a pair of MTM speakers but there does not seem to be a good site where design concepts are explained. On this forum, there is info but in bits an pieces.
Can anyone suggest a good website where I can start? I mean sites that explain about the driver placement on the baffle, how much spacing is needed, crossovers and related stuff. I will be grateful for any leads.
Thanks,
Vivek
hi
in the middle 80, the whole theory was explained in " the speaker builder" by Joseph D'Appolito
maybe you can see on "audioXpress.com" if they sell or upload these pages.
in the middle 80, the whole theory was explained in " the speaker builder" by Joseph D'Appolito
maybe you can see on "audioXpress.com" if they sell or upload these pages.
D'Appolito: "A Geometric Approach to Eliminating Lobing Error in Multiway Loudspeakers" Audio Eng. Society Preprint 2000, Convention 74, Sept. 1983.
But these books are not available in India, at least not in Bangalore. Maybe I have to study DIY projects and get ideas from them.
Vivek
Vivek
hmm....let me see..... rajiv d'souza of lithos will have these books. ask him if he can send you a copy. give im my ref. remind him i had donated my entire library of audio books to him when he was starting out. i cant find his latest contact number but maybe google can help.
Hi..getting those books is almost impossible here. why dont u become an AES member..u can buy all those papers through AES published in their journals. GOTO www.aesindia.org or www.aes.org.
Hi,
I was searching with Google and this is what I got at audioasylum.
``To calculate the center to center distance between adjacent drivers divide the speed of sound (13,503.94 inches per second) by the crossover freq. The distance you calculate is from center of each mid to center of tweeter If your spacing will not make the 1 wavelength criteria but is close then you can offset the tweeter above the midbass center line to help close the distance. Sometimes is easier to lay out the driver holes on the baffle so the drivers are tight to each other and back track using the speed of sound calculation to get the crossover freq.
13,503.94/XO freq.=1 wavelength of the crossover freq.''
Now, does one offset the tweeter arbitrarily or is there a ratio like the 1:1.618 suggested for the Ariel loudspeaker.
Calculating with the equation given above, what unit will I have to use to space out the two midbass drivers.
Vivek
I was searching with Google and this is what I got at audioasylum.
``To calculate the center to center distance between adjacent drivers divide the speed of sound (13,503.94 inches per second) by the crossover freq. The distance you calculate is from center of each mid to center of tweeter If your spacing will not make the 1 wavelength criteria but is close then you can offset the tweeter above the midbass center line to help close the distance. Sometimes is easier to lay out the driver holes on the baffle so the drivers are tight to each other and back track using the speed of sound calculation to get the crossover freq.
13,503.94/XO freq.=1 wavelength of the crossover freq.''
Now, does one offset the tweeter arbitrarily or is there a ratio like the 1:1.618 suggested for the Ariel loudspeaker.
Calculating with the equation given above, what unit will I have to use to space out the two midbass drivers.
Vivek
What you do is figure out where you want to crossover and choose the drivers accordingly. If you want to crossover at 3kHz, fo instance, the wavelength is about 4.5 inches, so don't even dream about using ten inch woofs. If you can't fit the tweeter in between the midwoofs you slide it over to one side to allow the midwoofs to go closer together, then mirror-image the two boxes. The obvious downside to the alignment is that driver sizes have to be small but the crossover still has to be fairly low. Joe favors 18 cm drivers crossed at 2.5kHz, as a for instance.
Hello Bill,
I have Vifa TC18WG49s which are 6.5 inch drivers. The tweeters are Vifa D27s and I plan to cross them over at 2.5KHz. But can the tweeter be moved to any distance sideways to fit the woofers to the required distance. If there is enough space between the two midbass drivers, can the tweeter be located centrally.
Vivek
I have Vifa TC18WG49s which are 6.5 inch drivers. The tweeters are Vifa D27s and I plan to cross them over at 2.5KHz. But can the tweeter be moved to any distance sideways to fit the woofers to the required distance. If there is enough space between the two midbass drivers, can the tweeter be located centrally.
Vivek
If you can fit the whole thing on the same vertical plane then fine, that's the preferred method. A 2.5kHz crossover would like to have the woofer to tweeter distance on center at 5.4 inches, but don't lose sleep if it ends up having to go 6, as that's what Joe did with the Thor TL MTM. If you want to slide the tweeter to one side go as little distance as possible, and again mirror-image the two boxes.
Ok, got it. Just to confirm, if I am choosing 2.5KHz, the distance from the centre of the woofer to the centre of the tweeter is nearly 5.4 inches.
Thanks a lot.
Vivek
Thanks a lot.
Vivek
Certainly. Just give me some time to get the cabinets ready. I get only one off day in a week when I can work on the speaker. I am also keen to finish the project and enjoy the fruits of my work. I will try to speed up the work a little bit.
Vivek
Vivek
took me almost 10 months to finish my last speaker and when the box was done the 8" woofers were damaged. so now I use it as a 6" 2 way till i get new 8" woofers. yet I am planning a new speaker or maybe 2.
options (1) Jordan 53/125 with 92 for surrounds, (2) Fostex FF85/SEAS CA21 with Fostex 103/107 coupled with SEAS CA11 for surround.
front channels 25 liters, rear channels 12 liters. only variation between the 2 designs is that if i include a center then the fosex design will be a WMW with 2 FW108s flanking a FE103 or 107.
a set of Jordan drivers cost over 2 times as much as fostex.
2 JX125, 2 JX 53, 3 JX 92 about $905 from creative sound
2 x FF85, 2 X SEAS CA21REX, 3 X FE103/107, 4x SEAS CA11RCY about $435 from madisound.
i can save about $110-135 by eliminating the center channel for the fostex-jordan sets.
An additional JX53 or FF85K to improve power handling might be added. This issue is being debated in my mind keeping in mind polar interference. Also in the case of the Fostex system the CA21 might be replaced with the CA18 as the CA18 will displace 50% more air.
options (1) Jordan 53/125 with 92 for surrounds, (2) Fostex FF85/SEAS CA21 with Fostex 103/107 coupled with SEAS CA11 for surround.
front channels 25 liters, rear channels 12 liters. only variation between the 2 designs is that if i include a center then the fosex design will be a WMW with 2 FW108s flanking a FE103 or 107.
a set of Jordan drivers cost over 2 times as much as fostex.
2 JX125, 2 JX 53, 3 JX 92 about $905 from creative sound
2 x FF85, 2 X SEAS CA21REX, 3 X FE103/107, 4x SEAS CA11RCY about $435 from madisound.
i can save about $110-135 by eliminating the center channel for the fostex-jordan sets.
An additional JX53 or FF85K to improve power handling might be added. This issue is being debated in my mind keeping in mind polar interference. Also in the case of the Fostex system the CA21 might be replaced with the CA18 as the CA18 will displace 50% more air.
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