"Hello, two above and two below the MMT, hinge the sides and mount the other four as vertical pairs on each of the hinged wings low to the ground next to the bottom two WWMMTWW woofers, you can curve the center down to angle top of the wings. This will narrow the whole system and will get you good bass"
Thanks for your input Mike - much appreciated. If you wanted to forgo the hinges, are you talking about something like this? I think it's option #347. 🙂
I like the idea of keeping the woofers close to the floor to maximize the use of the baffle extension the floor can provide.
"That makes sense if you need subwoofer frequencies well below dipole resonance."
Thanks AJ, you're right. I'm not trying to build a subwoofer here. It's kinda why "turning every other driver around" needs to be "thought thru". 🙂
Ultimately, if I decide to keep this approach, I want the Madisons to work between 80-100hz and up as high as they can reasonably go. Upper bass thru the entire midrange would be nice. I'm still experimenting, trying to find what I really like in a speaker. So far, the only thing I can say for sure is that I like high sensitivity and compression drivers in waveguides. Beyond that, it's all open ended.
Thanks for your input Mike - much appreciated. If you wanted to forgo the hinges, are you talking about something like this? I think it's option #347. 🙂
An externally hosted image should be here but it was not working when we last tested it.
I like the idea of keeping the woofers close to the floor to maximize the use of the baffle extension the floor can provide.
"That makes sense if you need subwoofer frequencies well below dipole resonance."
Thanks AJ, you're right. I'm not trying to build a subwoofer here. It's kinda why "turning every other driver around" needs to be "thought thru". 🙂
Ultimately, if I decide to keep this approach, I want the Madisons to work between 80-100hz and up as high as they can reasonably go. Upper bass thru the entire midrange would be nice. I'm still experimenting, trying to find what I really like in a speaker. So far, the only thing I can say for sure is that I like high sensitivity and compression drivers in waveguides. Beyond that, it's all open ended.
I'd aim for a pyramid-shaped configuration, with the majority of the woofers close to the floor. This maximizes coupling to the floor image (resulting in twice as many drivers and 2X amplifier power for free), and puts the mid and HF drivers at the top, where they belong for most natural image quality (at or slightly above listening height).
The bass drivers are going to have to be parametrically equalized on a per-channel basis anyway, so I wouldn't worry about room modes too much.
Turning every other driver around will have no effect on baffle shaking - sorry. All of the cones will be moving in the same direction, after all, and it's cone mass that will shake the baffle (think sandbags and struts to quiet things down). What it will do, though, is reduce 2nd, 4th, and higher-order even distortion terms by anywhere from 5 to 15 dB, due to push-pull cancellation.
This is real and worthwhile (I did it for my first subwoofer in 1979), but looks pretty awful, with half the magnets pointing at you. If you do this, only do it for the lowest-frequency drivers - the differences between front and rear emission start to matter for mid and higher frequencies, thus losing the distortion-cancellation effect.
The bass drivers are going to have to be parametrically equalized on a per-channel basis anyway, so I wouldn't worry about room modes too much.
Turning every other driver around will have no effect on baffle shaking - sorry. All of the cones will be moving in the same direction, after all, and it's cone mass that will shake the baffle (think sandbags and struts to quiet things down). What it will do, though, is reduce 2nd, 4th, and higher-order even distortion terms by anywhere from 5 to 15 dB, due to push-pull cancellation.
This is real and worthwhile (I did it for my first subwoofer in 1979), but looks pretty awful, with half the magnets pointing at you. If you do this, only do it for the lowest-frequency drivers - the differences between front and rear emission start to matter for mid and higher frequencies, thus losing the distortion-cancellation effect.
How about building 8 Ripoles, 4 per side, add a 1,30m x 0,30m open baffle for mid/high section crossed in at 150-200Hz. Will be a lot smaller and lots of bass below 30Hz.
regards, Micha
regards, Micha
AJinFLA said:
bunk...even with Madison's optimistic specs, you're intentionally lowballing just to be a nuisance. For example, the listed xmax is 6.3mm...so....where did you come up with 0.5mm? Link, please.
Based on the Sd given, it's quite obvious he's referring to the PR170 midranges.pedroskova said:
bunk...even with Madison's optimistic specs, you're intentionally lowballing just to be a nuisance. For example, the listed xmax is 6.3mm...so....where did you come up with 0.5mm? Link, please.
Brett said:
AJ, the starter of this thread, stated in the original post...
...so where does 200Hz, barn doors, and "so-called ripoles" fit in?
I know what Alan said, but you quoted AJ in FLA, so I don't know. Perhaps you should ask him.pedroskova said:
The Sd and Xmax earlier are the PR170's. and the 500Hz xover is also appropriate.
With 8x12" per side, it's going to be a barn door of an OB.
AJ said:
Nope, you're gonna want to crossover the audax 400-500 Hz so a single baffle around 15" wide - vertically from the bottom up 2 woofers, then two mids, then the treble above that two more woofers. Then two more baffles on both sides triangulated (is that a word? LOL) with two woofers mounted at the bottom of each one. A folding wall. Use piano hinges to connect it all together and MAPLE plywood if you can find it. Brace it with 2 by 2 pine - it should be killer
Brett said:
Yes, it's going to be a barn door, which takes away any xmax considerations for the PR170's @ 500Hz. Go back and read his diatribe.
I was thinking more about distortion than using up all the Xmax for that driver on a large baffle.pedroskova said:
Hi Mike
"Nope, you're gonna want to crossover the audax 400-500 Hz so a single baffle around 15" wide - vertically from the bottom up 2 woofers, then two mids, then the treble above that two more woofers. Then two more baffles on both sides triangulated (is that a word? LOL) with two woofers mounted at the bottom of each one. A folding wall. Use piano hinges to connect it all together and MAPLE plywood if you can find it. Brace it with 2 by 2 pine - it should be killer"
Agree on the 500Hz to the Audax. I reread your post and I think this is what you're talking about, except that the two lower outside woofers would be on the hinged panels:
Angling the tops of the wings to meet the center baffle would somewhat produce a pyramid shape. Am I on the right track?
The sketches are true to scale and I've got the WG pegged at 38 inches from the bottom of the baffle - I don't want to mess with that too much. I'm listening to them right now at 41 inches and I'd prefer 36 inches. I can't really do a true TMM with two woofers below them without moving the WG center to 44+ inches. The only way to keep the WG height is to do the side-by-side thing with the mids.
I've got a bunch of 11-ply Birch that should work well for the baffles. I'm serious about a double wall with a 3/4 inch cavity between them filled with kitty litter. The drivers are so tightly packed, I'm not sure if that's doable, but a minimum of 2 layers of 3/4 ply isn't gonna hurt I suspect.
"Nope, you're gonna want to crossover the audax 400-500 Hz so a single baffle around 15" wide - vertically from the bottom up 2 woofers, then two mids, then the treble above that two more woofers. Then two more baffles on both sides triangulated (is that a word? LOL) with two woofers mounted at the bottom of each one. A folding wall. Use piano hinges to connect it all together and MAPLE plywood if you can find it. Brace it with 2 by 2 pine - it should be killer"
Agree on the 500Hz to the Audax. I reread your post and I think this is what you're talking about, except that the two lower outside woofers would be on the hinged panels:
An externally hosted image should be here but it was not working when we last tested it.
Angling the tops of the wings to meet the center baffle would somewhat produce a pyramid shape. Am I on the right track?
The sketches are true to scale and I've got the WG pegged at 38 inches from the bottom of the baffle - I don't want to mess with that too much. I'm listening to them right now at 41 inches and I'd prefer 36 inches. I can't really do a true TMM with two woofers below them without moving the WG center to 44+ inches. The only way to keep the WG height is to do the side-by-side thing with the mids.
I've got a bunch of 11-ply Birch that should work well for the baffles. I'm serious about a double wall with a 3/4 inch cavity between them filled with kitty litter. The drivers are so tightly packed, I'm not sure if that's doable, but a minimum of 2 layers of 3/4 ply isn't gonna hurt I suspect.
Remove the 12 in the top row middle. Put the PR170's vertically in that space to get the listening height correct. WG vertically above. Place the rest of the 12's lowish on the baffle wherever they fit (beside PR+WG)
AJ said:
AJ,
What Paul was suggesting was a W baffle with the drivers facing each other for force cancellation. You need a flat baffle, but can still reverse half the motors for even order distortion reduction.
It is also advisable to keep the mid baffle narrower than the barn door, nicely explained here by JohnK. Since you have already made the decision on drivers and (barn door🙂) baffle, my suggestion would be a configuration like this
An externally hosted image should be here but it was not working when we last tested it.
(a bit tough to explain in words yesterday, so I did a quick n' nasty sketch for ya). Slots (2") around the mid panel and reversed woofer motors to the outside should allow 4 in a row on a 48" baffle, because it allows some overlap of the frames/rear holes. I would also suggest lowering the mid XO to around 400hz. The motors of the (reversed) woofers should not affect the response too much above this and they would not have become too directional.
Measurements will tell the story.
Best of luck.
cheers,
AJ
p.s. at least we know what to get pedroskova for christmas now. Won't help the comprehension part, but at least he might be able to read what I wrote in my response to Paul 😉
Thanks AJinFla, Lynn & Mike - there seems to be some consensus here on the baffle width for the mids/highs so I'll keep that one. Plus, the "barn door" isn't cast in stone; I just drew it in for a reference to keep me focused on how much room I really have to work with. If I can cut down the size and weight, it won't hurt my feelings one bit. 🙂
My intuition makes me want to keep all 8 woofers close to the floor so I'll keep that suggestion as well. Mike's idea of the hinged baffle will go into the mix tool, so I'll have all 8 near the floor with the outer 4 on hinges.
This has some more appeal for future trials too - if I can make the woofer section modular, I only need to recut baffles for the mids/highs. I want to look at Mike's suggestion for a horn-loaded mid and it'll be alot easier to to swap everything out if I can leave the woofers out of the picture.
Cool guys; thanks for your help. I'll post some pics and measurements when it's all done if anyone's interested.
My intuition makes me want to keep all 8 woofers close to the floor so I'll keep that suggestion as well. Mike's idea of the hinged baffle will go into the mix tool, so I'll have all 8 near the floor with the outer 4 on hinges.
This has some more appeal for future trials too - if I can make the woofer section modular, I only need to recut baffles for the mids/highs. I want to look at Mike's suggestion for a horn-loaded mid and it'll be alot easier to to swap everything out if I can leave the woofers out of the picture.
Cool guys; thanks for your help. I'll post some pics and measurements when it's all done if anyone's interested.
Brett - I didn't want to leave you out. Thanks for the suggestions. I hear what you're saying about removing the center woofer, but what am I gonna do with that last woofer? If I put 7 on the bottom, that lone woofer is gonna feel left out. If I go with 5 on the bottom, then I still have three to fit in. Symmetry is elusive here. 🙂
I guess I still need to think about this a bit.
I guess I still need to think about this a bit.
One more question
I know I'm not the only one that's wondered about this - exactly how does a WG work in an MTM situation? AJinFla drew his sketch with the WG in the middle and that leaves about 18 inches c2c between the mids. Does the waveguide allow more lattitude with combing effects or is it maybe just not audible???
I know I'm not the only one that's wondered about this - exactly how does a WG work in an MTM situation? AJinFla drew his sketch with the WG in the middle and that leaves about 18 inches c2c between the mids. Does the waveguide allow more lattitude with combing effects or is it maybe just not audible???
Put two on the sides and the last one centre top above the HF.AJ said:
How wide can you go with this baffle and still have it fit in your room?
I've shelved the 2x2 15" idea for my room because a 3" wide baffle with even modest side wings just takes up too much room; they'd almost need to be in the corners. I'll play with horns again, and keed the drivers for when I move home and have that big open room again. I'm also going to build a push-pull manifold midbass design a la djk's idea in another thread to remove the KHorn midbass issues, even though I'll probably LPF them at 200Hz.
Al, I like AJ in FLA's idea of the slottong around the MF/HF array. If that worked, you could also completely seperate them on a sub baffle, mounted on a stand from behind a la Linkwitz Pheonix, but with the stand deeper to clear all the 12's. Even if the slots don't work, a similar arrangement but with say 3/8" clearance to the main baffle and some felt around the edges of the sub-baffle as a 'gasket'. Seems to me this would isolate the vibration from all those 12's getting to the MF/HF.
Also, I think I'd rather have the centre 4 12's having their cones facing the room and the outer 4 reversed.
Last thought: if all this works, I'd be very tempted to build 16 LM3886's with a big common PSU and vary the LP xover freq's and output Z's to suit different drivers on the baffle. EG, cross all the 'reversed' drivers at 200, where the forward ones range up to 400.
Re: One more question
I don't see why it would work any differently to a normal MTM in terms of C-C distances. Maybe try the XT120 flare to start with as the PR170's can run high. If it works, you can turn up a small flare similar to the DDS on your lathe.AJ said:
Brett,
"How wide can you go with this baffle and still have it fit in your room?"
Since WAF isn't an issue, I can go 60 inches if need be. here's a 60 inch width, one lone woofer on top, and a narrow baffle (sorta) for the mids and highs. Of course there's still variations beyond this but this is where the direction seems to be going. Time to think about 7 drivers on the baffle and one in a transmission line behind everything for sub-100hz duty. 😀
I definitely want to see about using separate baffles for the woofers and upper range stuff. I really don't want to be cutting entire baffles over and over again until I get this right. I don't want to initially reverse any of the drivers, mostly because the thought of listening to lower midrange (and probably higher) from the back of a driver just plain bugs me. 🙂
"Maybe try the XT120 flare to start with as the PR170's can run high. If it works, you can turn up a small flare similar to the DDS on your lathe."
The waveguides are down the road a bit. I need to get a feel for this bass thing first so I'm just gonna go with what I have on hand WRT mids and highs. One step at a time. 🙂
"How wide can you go with this baffle and still have it fit in your room?"
Since WAF isn't an issue, I can go 60 inches if need be. here's a 60 inch width, one lone woofer on top, and a narrow baffle (sorta) for the mids and highs. Of course there's still variations beyond this but this is where the direction seems to be going. Time to think about 7 drivers on the baffle and one in a transmission line behind everything for sub-100hz duty. 😀
An externally hosted image should be here but it was not working when we last tested it.
I definitely want to see about using separate baffles for the woofers and upper range stuff. I really don't want to be cutting entire baffles over and over again until I get this right. I don't want to initially reverse any of the drivers, mostly because the thought of listening to lower midrange (and probably higher) from the back of a driver just plain bugs me. 🙂
"Maybe try the XT120 flare to start with as the PR170's can run high. If it works, you can turn up a small flare similar to the DDS on your lathe."
The waveguides are down the road a bit. I need to get a feel for this bass thing first so I'm just gonna go with what I have on hand WRT mids and highs. One step at a time. 🙂
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