Hi Folks, question about wood thickness and/or bracing for the Carmody Amiga speakers. I have built a couple pair of Overnight Sensations MTM, and really like them, and look forward to a set of the Amigas. But I have a question based on my habit of trying to repurpose old tabletops as speaker cabinets. The typical thickness is maybe 1/2", and cherry. so...not quite the recommended 3/4 MDF or such.
I would really rather not laminate up to 3/4, and instead use more bracing. Is this a bad idea, and if not, what about adding 4 additional braces (in-between existing braces), and making up the difference in volume with a slight tweak to length? I could use 3/4" ply for all the bracing.
Thanks!
I would really rather not laminate up to 3/4, and instead use more bracing. Is this a bad idea, and if not, what about adding 4 additional braces (in-between existing braces), and making up the difference in volume with a slight tweak to length? I could use 3/4" ply for all the bracing.
Thanks!
I don't see why you could not make it work. Cherry, even thinner is pretty stout stuff. I think the three internal braces are more than adequate, so long as cuts are accurate and gluing is well executed. I would think a good treatment with some sort of sound deadening mat adhered to the walls between the braces would prevent higher frequency resonances from those areas. I'm too cheap to use the very expensive products made for this- I would think rubber floor mat of the right thickness and give would work pretty well.
If it is not made in the US, ¾” is more likely 18mm
I’d use plywood for the entire thing. But if you know how to build with solid, go for it.
A short ML-TL (likely forced), i’d likely have it built with 15mm, but with proper bracing… as shown not very good. Solid would need thickness appropriate to the material used.
dave
Thanks Dave, makes sense.
However...I had a slight change in direction, given that I have a pair of OSD MTMs, and thought maybe it best to go the fast/cheap route - and build the Bungelo Ed's OS MTM MLTL. I was mainly inspired to do this because I had Ed's modeled response curves, and I could revisit SpicyTL to use these as an this opportunity to understand better the theory behind the MLTL prior to building.
Clearly there is a lot of dust in that corner of my brain, because I have been struggling to get anything close to the curves generated by Ed, though. Granted, I am modeling each driver independently, but I am seeing crazy responses in the upper speaker (in the virtual world). Ed modeled as a combined speaker.
This got me thinking about changing the TL to independent channels, which got me thinking about cross-sectional area and the relationship with Sd, and now I am hellaciously confused again. It would seem to me that the two factors defining cross sectional area is cutoff wavelength for internal reflection (~1/8 wavelength?), and the internal maximum air velocity? Is see how Sd plays a factor, but intended SPL surely plays a part as well.
And don't get me started on stuffing. But my brain is telling me that foam works fundamentally differently than fiber.
This is not to say the either of the speakers need my review, of course! But I am building to try to understand, mainly, and clearly there is still a big gap!
However...I had a slight change in direction, given that I have a pair of OSD MTMs, and thought maybe it best to go the fast/cheap route - and build the Bungelo Ed's OS MTM MLTL. I was mainly inspired to do this because I had Ed's modeled response curves, and I could revisit SpicyTL to use these as an this opportunity to understand better the theory behind the MLTL prior to building.
Clearly there is a lot of dust in that corner of my brain, because I have been struggling to get anything close to the curves generated by Ed, though. Granted, I am modeling each driver independently, but I am seeing crazy responses in the upper speaker (in the virtual world). Ed modeled as a combined speaker.
This got me thinking about changing the TL to independent channels, which got me thinking about cross-sectional area and the relationship with Sd, and now I am hellaciously confused again. It would seem to me that the two factors defining cross sectional area is cutoff wavelength for internal reflection (~1/8 wavelength?), and the internal maximum air velocity? Is see how Sd plays a factor, but intended SPL surely plays a part as well.
And don't get me started on stuffing. But my brain is telling me that foam works fundamentally differently than fiber.
This is not to say the either of the speakers need my review, of course! But I am building to try to understand, mainly, and clearly there is still a big gap!
Pretty simple: there is no relationship. We don’t care about Sd except that it relates towhoe big the baffle is to mount the driver.
⅛ wavelength?
dave
Ok, no now I am even more confused. Please note, I am not a professional.
I thought that around the dimension of about 1/8 wavelength is where the cutoff was for additive wall reflection and so increased damping above that. Which is pretty much all the base notes, or pretty much all frequencies not impacted by baffle? And maybe then some?
I thought that the impedance of the transmission lines were directly affected by minimum cross sectional dimensions. Thus the impact of tapered lines. So doesn't this mean that Sd is directly related?
I am a long way off from dusting off my brain enough to look at the math....but I keep trying to mentally picture what is going on, and what I see in my brain is certainly not represented in the simplified electronic circuit. Not that it needs to be and clearly models like spicytl work very well when operating within a range of frequencies and dimensions.
So I hear what you are saying, and you have built a heck of a lot more speakers than I, so I am trying to make sense of these two things. In a practical sense, I don't think I am ready to play with rolling or modifying my own tline just yet. And I don't think it is warranted with the current drivers of the OS.
I thought that around the dimension of about 1/8 wavelength is where the cutoff was for additive wall reflection and so increased damping above that. Which is pretty much all the base notes, or pretty much all frequencies not impacted by baffle? And maybe then some?
I thought that the impedance of the transmission lines were directly affected by minimum cross sectional dimensions. Thus the impact of tapered lines. So doesn't this mean that Sd is directly related?
I am a long way off from dusting off my brain enough to look at the math....but I keep trying to mentally picture what is going on, and what I see in my brain is certainly not represented in the simplified electronic circuit. Not that it needs to be and clearly models like spicytl work very well when operating within a range of frequencies and dimensions.
So I hear what you are saying, and you have built a heck of a lot more speakers than I, so I am trying to make sense of these two things. In a practical sense, I don't think I am ready to play with rolling or modifying my own tline just yet. And I don't think it is warranted with the current drivers of the OS.