Hello everyone, I’m pretty new to the diy world and have only done a few projects. My current one is a pair of mtm based off of Jeff bagbys design. I’d love to have a mt version for my surrounds but I have no idea how to change the xover to make that work. Any help would be amazing. Wife said she’d buy me the parts for Xmas if I can figure out what I need. Thanks
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Nice looking build!
Well, It's pretty complicated. I'd hesitate to even suggest something other than as a starting point.
You could replace one of the two mids with a resistor, but that wont behave like the missing driver and could mess up what the series CL is trying to do; make a resonant shunt at the speaker Fs?
Then the tweeter will be too loud, as it's expecting to match up with two mids. So you'll need to drop the level. You could simply increase the 3 Ohm (and add another resistor from the cap connection node to [-] ) such that their parallel combination is still 3 Ohm - but they also provide the needed attenuation; 6 db?
A beginning of what you have to go through, in taking an existing design and think "I'll just pop out one of the woofers" for a little bit smaller cabinet or whatever - as if there's a rule surrounds have to be smaller than mains. Easier to manufacture and ship a complete surround system that way, which is probably the genesis of that paradigm.
No doubt it can be done - with a complete resdesign of the crossovers. Or you can experiment with resistors within the existing design and - hopefully - arrive at a sound you like.
Well, It's pretty complicated. I'd hesitate to even suggest something other than as a starting point.
You could replace one of the two mids with a resistor, but that wont behave like the missing driver and could mess up what the series CL is trying to do; make a resonant shunt at the speaker Fs?
Then the tweeter will be too loud, as it's expecting to match up with two mids. So you'll need to drop the level. You could simply increase the 3 Ohm (and add another resistor from the cap connection node to [-] ) such that their parallel combination is still 3 Ohm - but they also provide the needed attenuation; 6 db?
A beginning of what you have to go through, in taking an existing design and think "I'll just pop out one of the woofers" for a little bit smaller cabinet or whatever - as if there's a rule surrounds have to be smaller than mains. Easier to manufacture and ship a complete surround system that way, which is probably the genesis of that paradigm.
No doubt it can be done - with a complete resdesign of the crossovers. Or you can experiment with resistors within the existing design and - hopefully - arrive at a sound you like.
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Thanks for the reply, I guess I should just scrap that idea and pick something that at least uses the same tweeter. From what I understand that’s the most important then when match speakers correct ?
Gee, I cant confirm that one either. The woofers carry quite a few octaves of information also, if they are substantially different units, you'll hear it.
Then again, unsure what the surrounds even do these days, outside of "ambience". Do they plays sounds unique to their location, i.e. apparently behind you? If so, I'd think a good match to what you have in front would be best.
If it's just all echos and room reflections of some simulated space, then perhaps you could get away with something that sounds different than your mains, because real echos and room reflections actually sound different than the direct line of sound. I dont know who can tell "that recorded echo off the wall the sound engineer is trying to portray as back there" doesnt sound quite right, compared to the front speakers sound.
I quit multichannel in the 70's as an "if you cant say it with two" impractical extravagance. I had a Marantz Quadradial 4 receiver back then...dreamt of getting a 2nd pair of large Advents for it.
Then again, unsure what the surrounds even do these days, outside of "ambience". Do they plays sounds unique to their location, i.e. apparently behind you? If so, I'd think a good match to what you have in front would be best.
If it's just all echos and room reflections of some simulated space, then perhaps you could get away with something that sounds different than your mains, because real echos and room reflections actually sound different than the direct line of sound. I dont know who can tell "that recorded echo off the wall the sound engineer is trying to portray as back there" doesnt sound quite right, compared to the front speakers sound.
I quit multichannel in the 70's as an "if you cant say it with two" impractical extravagance. I had a Marantz Quadradial 4 receiver back then...dreamt of getting a 2nd pair of large Advents for it.
my pocket calculator says: for the woofer part of the crossover, double the value for the coil in series, the cap in parallell should be half the value, and the parallell coil should be double
the tweeter crossover is a lot trickier, almost all components needs to be changed, but minimum, you can try to increase the series resistor to 12-15 ohm and the first cap to 3.3uf for a 6db lower output and still have a similar phase response
the tweeter crossover is a lot trickier, almost all components needs to be changed, but minimum, you can try to increase the series resistor to 12-15 ohm and the first cap to 3.3uf for a 6db lower output and still have a similar phase response
oh i saw now that my calculator missed the parallel coil in the tweeter crossover which of course needs to double its value
Man I wish I could understand all this stuff like you guys can. I appreciate the help, do you think it’s worth it to try and do this or just find an already proven plan for a similar speaker ? I’m very new at this, I can build speakers and make the xovers but other then that I’m kinda useless lol
celef is technically correct for the woofer but a little off for the tweeter.
For the woofer, celef's values need to be tweeked just a touch to help line up the phase again. For the tweeter, everything can remain the same except for the series resistor. Bumping that up to 9ohm should do the trick to compensate for the 6dB of loss in sensitivity between 1 woofer and 2.
The XSim pic is below. The grey curve is the summed response from the MTM and is the target you should be trying to match. The sim for the TM is on a 9" x 13" baffle. For the MTM, on a 9" x 21" baffle. Something close to 9" x 13" for the TM will be fine.
For the woofer, celef's values need to be tweeked just a touch to help line up the phase again. For the tweeter, everything can remain the same except for the series resistor. Bumping that up to 9ohm should do the trick to compensate for the 6dB of loss in sensitivity between 1 woofer and 2.
The XSim pic is below. The grey curve is the summed response from the MTM and is the target you should be trying to match. The sim for the TM is on a 9" x 13" baffle. For the MTM, on a 9" x 21" baffle. Something close to 9" x 13" for the TM will be fine.
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Absolutely. The sims look spot on for these drivers which is not always the case.
It should sound pretty much exactly like the MTM's, just not be able to play quite as loud. (Only 1 woofer instead of 2)
It should sound pretty much exactly like the MTM's, just not be able to play quite as loud. (Only 1 woofer instead of 2)
That’s amazing, I can’t thank you enough. Here’s is where I got the plans for the mtm’s I built. I don’t know if this will help confirm everything. Yet Another RS180 MTM -
Techtalk Speaker Building, Audio, Video Discussion Forum
Yes, I'm familiar with Jeff Bagby's original MTM but I hadn't seen Don Radick's version. Good to know it was also done by someone who knows what they are doing.
When you want to change a design in this manner, the original version doesn't really matter so much. Once I do a sim for that version, that summed response in the simulation becomes the new target curve and as long as the new xo for the TM matches that curve and phase alignment, it should be good to go.
Don't know if it will help in terms of understanding but attached below is the sim of the MTM this time followed by the sim of the new TM version again. You can perhaps better compare how the two matchup to each other.
When you want to change a design in this manner, the original version doesn't really matter so much. Once I do a sim for that version, that summed response in the simulation becomes the new target curve and as long as the new xo for the TM matches that curve and phase alignment, it should be good to go.
Don't know if it will help in terms of understanding but attached below is the sim of the MTM this time followed by the sim of the new TM version again. You can perhaps better compare how the two matchup to each other.
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Thank you so much, I’m so glad I found this forum. Now I’ll be able to get a parts list for my wife lol. You mentioned before this is based off a 9x13 baffle, do I have to stick with that size or am I able to change it a bit ?
Not much really, just wondering if it could be a little shorter (make the wife a lil happier) lol Would it be possible to make a mmtmm center channel version of these ? I don’t know why but I’ve always loved the look of klipsch’s huge center
If you use 3/4" material, it looks to me like it's pretty hard to get the TM cab any smaller than 8.75" x 12.6" without having the tweeter and woofer faceplates overlap.
I'm not too sure about the CC. But generally an MTM design for a CC is not considered as good as a W(T/M)W configuration (T/M=tweeter above a mid). Here's a good one that uses the RS180's - Zaph|Audio - ZDT3.5. The CC is towards the bottom of the page.
I'm not too sure about the CC. But generally an MTM design for a CC is not considered as good as a W(T/M)W configuration (T/M=tweeter above a mid). Here's a good one that uses the RS180's - Zaph|Audio - ZDT3.5. The CC is towards the bottom of the page.
Ya you’re right, I went an measured and i don’t know what I was thinking lol.
I’ve seen that design before and it seems great just not quite what I’m looking for. You’re right I meant to say wmtmw. But for now I’ll focus on the mt’s. I can’t thank you enough for helping me. No matter how many videos I watch I just can’t get how you guys do this with xovers lol. I’m jealous of your skills.
I’ve seen that design before and it seems great just not quite what I’m looking for. You’re right I meant to say wmtmw. But for now I’ll focus on the mt’s. I can’t thank you enough for helping me. No matter how many videos I watch I just can’t get how you guys do this with xovers lol. I’m jealous of your skills.