Lotus | MBVR for CHR-70 (1 or 2)
http://www.diyaudio.com/forums/showthread.php?s=&postid=1801575#post1801575
dave
http://www.diyaudio.com/forums/showthread.php?s=&postid=1801575#post1801575
dave
Yep, one or two. Designed for one, it just happens that two (in series) also will work as there's sufficient volume. As I mentioned in the Spawn thread, it's a compact (as they go) cab. notionally designed for smaller spaces / more modest SPLs on primarily acoustic music. However, the twin units will give better power-handling -total excursion plummets; maxes out at 0.8mm 1m / 1w shared between the two drivers. I'm building a pair myself for my CHRs.
Oh yes -line the cab. 1/2in wool felt or fiberglass, top, back & one side-wall (the opposite to the one the 2nd driver is on would be the obvious candidate...
)
Oh yes -line the cab. 1/2in wool felt or fiberglass, top, back & one side-wall (the opposite to the one the 2nd driver is on would be the obvious candidate...
)
I'm having trouble deducing the measurements of the little wedge that is located on the axis of symmetry on the back wall. Also, the internal brace is intentionally off center correct? I'd imagine that if the brace is on the left side of the center I'd put the second driver on the right side?
That's because there aren't any on the plan. 1in deep, equilateral triangle. It isn't very big. Yes, the brace is slightly offset -away from the sideways firing driver is probably best, although there's very little in it. The brace is optional anyway, as these boxes are quite slim.
Depends on the sheet size -I usually work in 4' x 8', as that's what's most often found in the UK, and unless you pull some fancy stuff (by my standards -I'm the world's worst woodworker) you can't quite do it with that. But I think it might just be doable with 5' x 5'.
1in deep, equilateral triangle. It isn't very big. Yes, the brace is slightly offset -away from the sideways firing driver is probably best, although there's very little in it. The brace is optional anyway, as these boxes are quite slim. Depends on the sheet size -I usually work in 4' x 8', as that's what's most often found in the UK, and unless you pull some fancy stuff (by my standards -I'm the world's worst woodworker) you can't quite do it with that. But I think it might just be doable with 5' x 5'.
Lotus Spawn
So, I've had my CHR70s for a few days and I've been able to crank it a few times and I think this BVR may be ideal. The depth of bass from these drivers is incredible considering their size but the quality suffers a little in the BR. But the quality should improve in the Lotus. And two drivers could just be the best inexpensive speaker available (considering the BB ply is going to cost more than the drivers.) Thank you Scott and Dave for the design.
I noticed that the driver is only 26" from the floor. What would be a recommended way to raise this? Could front baffle be recessed making the height of the cavity longer (resulting in a C-shaped side panel and leaving the vents the same dimensions)? If internal depth is reduced to 5", it would raise the driver 10.5", and 6" would raise the driver 6.25".
One thing you should be aware of, the frame lip is 6mm (~.25") and it's not solid. Recessing the driver takes a considerable chunk out of the baffle. And although the drivers include a (thin) gasket, you may want to fill the back side of the frame flange to ensure it seals or use an alternative, thicker gasket, especially if your route was not smooth. Lastly, the mounting holes are small, #4 screws only. Two more mounting holes would have been nice. You may want to use a positive mounting system, like t-nuts. Fortunately, the flange is wide and leaves a good amount of material behind it. Some kinda supra- or double-baffle might be worthwhile, or surface mount on the baffle and use a 0.25" trim panel (fortunately, it's a common material thickness for lots of different woods.)
So, I've had my CHR70s for a few days and I've been able to crank it a few times and I think this BVR may be ideal. The depth of bass from these drivers is incredible considering their size but the quality suffers a little in the BR. But the quality should improve in the Lotus. And two drivers could just be the best inexpensive speaker available (considering the BB ply is going to cost more than the drivers.) Thank you Scott and Dave for the design.
I noticed that the driver is only 26" from the floor. What would be a recommended way to raise this? Could front baffle be recessed making the height of the cavity longer (resulting in a C-shaped side panel and leaving the vents the same dimensions)? If internal depth is reduced to 5", it would raise the driver 10.5", and 6" would raise the driver 6.25".
One thing you should be aware of, the frame lip is 6mm (~.25") and it's not solid. Recessing the driver takes a considerable chunk out of the baffle. And although the drivers include a (thin) gasket, you may want to fill the back side of the frame flange to ensure it seals or use an alternative, thicker gasket, especially if your route was not smooth. Lastly, the mounting holes are small, #4 screws only. Two more mounting holes would have been nice. You may want to use a positive mounting system, like t-nuts. Fortunately, the flange is wide and leaves a good amount of material behind it. Some kinda supra- or double-baffle might be worthwhile, or surface mount on the baffle and use a 0.25" trim panel (fortunately, it's a common material thickness for lots of different woods.)
Scottmoose said:That's because there aren't any on the plan.
Depends on the sheet size -I usually work in 4' x 8', as that's what's most often found in the UK, and unless you pull some fancy stuff (by my standards -I'm the world's worst woodworker) you can't quite do it with that. But I think it might just be doable with 5' x 5'. ['/b]
not quite - actually with driver braces, etc, you'll be closer to 1 1/2 sheets at 5x5 ft
Scottmoose said:That's because there aren't any on the plan.
Yeah, I didn't think these would really need a brace but I was prepared to use one if you thought it was needed.
When you say 1" deep do you mean 1" from the base wall to the tip pointed at the rear of the driver?
Re: Lotus Spawn
In practise this is not really a hardship. Listening a bit off-axis is often a good thing to avoid the beaming inherent in most FRs. And if you wanted the driver firing right at your head, it wouldn't take nuch of a lift of the front of the speaker to do so.
Further, discuaaiona with Chris on driver placement for a dual-driver version (Scott comment please), we will probably move the front driver up a half basket width, and the side driver down a half driver width so as to maintain Zd, keep the drivers close together, yet decrease the reflective surfaces of the back of the drivers away from the other.
When you consider the base we'll add + that change, driver height becomes 31".
The diagram assumes that a minimum stabilization base has been added.
dave
HareBrained said:
In practise this is not really a hardship. Listening a bit off-axis is often a good thing to avoid the beaming inherent in most FRs. And if you wanted the driver firing right at your head, it wouldn't take nuch of a lift of the front of the speaker to do so.
Further, discuaaiona with Chris on driver placement for a dual-driver version (Scott comment please), we will probably move the front driver up a half basket width, and the side driver down a half driver width so as to maintain Zd, keep the drivers close together, yet decrease the reflective surfaces of the back of the drivers away from the other.
When you consider the base we'll add + that change, driver height becomes 31".
The diagram assumes that a minimum stabilization base has been added.
dave
Attachments
chrisb said:
To yield from a single 4x8 sheet, you'll need to splice one of the back panels - I'd suggest behind the triangular deflector.
Regarding driver height, Dave will probably be revisiting driver placement and bracing configuration when using a side mounted second driver (a la Calhoun) .
edit: I note that while I was planning the cut sheets for the 2 material sizes, he did just that.
and yes, even with substantial ballast in the lower void, these will be very tippy, and some type of extended width plinth would be required.
Re: Re: Lotus Spawn
Thanks for the responses. I should have realized a base would be needed (of course, I would have after building them.
) I rarely just sit and listen. I'm always moving around, but the "beaming" from the CHR70 isn't bad. You have to be a good angle off-axis to notice a drop in response. Certainly outside the "cone" illustrated by Dave. It'd be good to see some polar response charts for this driver.
Scottmoose said:Ah well. Can't have everything, right?
Re height, angle it backward. 3 - 4 degrees would be sufficient in most cases. You can't recess the baffle etc., or alter the shape of the driver chamber in any way without a total redesign.
planet10 said:
Scottmoose said:
Thanks for the responses. I should have realized a base would be needed (of course, I would have after building them.
) I rarely just sit and listen. I'm always moving around, but the "beaming" from the CHR70 isn't bad. You have to be a good angle off-axis to notice a drop in response. Certainly outside the "cone" illustrated by Dave. It'd be good to see some polar response charts for this driver.- Status
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