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For christmas my mom wants a new set of in-walls to replace their current old ones (6" poly cone, 1" fabric dome). Don't have a specific budget, but probably $500ish for the pair would be the expected range.
The plan is to use the largest DIY in-wall kit, in order to allow for the largest woofers possible. The plan is to simply increase the current hole size from the existing pair, and drop these in. They listen to about 98% of their music from the current in-walls so a top quality replacement would be a huge upgrade. They are driven off of an older Kenwood AVR in the basement HT room, as "B" speakers, and have a local transformer-type volume dial.
For woofers, I've been looking around a lot for 8-inchers that look okay for IB use. Where they are installed isn't really a massive airspace, but a step in the corner of a slanted ceiling. There's a picture below, I'm modelling with a very large sealed box rather than as true IB. I've been looking for woofers with as low a resonant frequency as possible, and a Qts of 0.4-0.5, if I should be looking for something else someone please say so. My current choice is the HiVI M8a, with an fs of 30Hz and Qts of 0.43. Anyone know of a better 8" woofer for IB use? I've used the M8N in another project before and loved the sound, coincidentally the M8a looks to have good specs for IB use.
I'm not as sure on a choice for the tweeter. Definately will need the best off-axis response as possible, so should I just be looking at domes? Right now I'm considering the Dayton RS28a for it's low crossover capability.
Another thing I'm worried about really is the off-axis response, since the speaker locations are by the ceiling, maybe 10ft+ high. The room is pretty large, maybe 30-35' x 10-12'.
I'm also thinking about painting the speaker baffles to match the paint in the room, since I'm concerned about the grills not clearing the woofer surrounds completely. So a tweet with a removable baffle would be nice so I could paint that, too. Another reason the RS28a is looking so tempting.
Due to location restraints, putting together a sealed in-wall enclosure is out of the question. Where a sealed Qtc .707 box would handle 20W (for the M8a), the IB config would only handle 20W with a 2nd order HPF at fs, and that loses a solid 1dB for most of the bass range compared to the Qtc .707. The only problem is, as I mentioned before, I'm not sure that I could fab an in-wall enclosure for these. So the best suited 8" driver for IB may be the best bet. With no HPF they will handle close to 10W, which I think will be plenty considering they don't turn up the volume loud often (if ever) and mostly listen to classical and jazz.
The cut-out locations:
So far I think I have a design pegged. Modelled using raw .frd info from the drivers, the HiVi M8a and the Dayton RS28a. Both are aluminum and should match voices nicely, I'm thinking.
I worked up an xover based on the actual physical layout, and an off-axis listening location @ 4m away and 2m down. Kinda taking advantage of the fact that the sitting/listening area and the location of the speakers is pretty well set in stone.
physical layout for modelling:
The model achieves 2nd-order roll-off for the LPF at 1300Hz (actual filter is below 1kHz or so), 4th order roll-off in the HPF at 1300Hz, series L-pad resistance of 2 ohms, and includes a series LCR notch at the woofer's breakup mode (2khz). Impedance stays above 6 ohms, which is desirable. This comes to about 10 components per crossover and puts the total price under $400.
Theoretical response is within +/-2dB and I'm not sure much could be done to improve it? Further off-axis response and power response look pretty great also. Actual on-axis response is strong in the high end and less flat, but I don't see anyone climbing on a ladder to listen to these at that level. Phase on the model does wrap like crazy but I'm not too concerned about that.
Does anyone see any problems with this design or approach? I feel pretty satisfied with it and am ready to order parts any day now. Since I've heard the Bagby software is pretty accurate, I'm kinda banking on that for designing around off-axis response.
Any comments or suggestions would be highly appreciated.
The plan is to use the largest DIY in-wall kit, in order to allow for the largest woofers possible. The plan is to simply increase the current hole size from the existing pair, and drop these in. They listen to about 98% of their music from the current in-walls so a top quality replacement would be a huge upgrade. They are driven off of an older Kenwood AVR in the basement HT room, as "B" speakers, and have a local transformer-type volume dial.
For woofers, I've been looking around a lot for 8-inchers that look okay for IB use. Where they are installed isn't really a massive airspace, but a step in the corner of a slanted ceiling. There's a picture below, I'm modelling with a very large sealed box rather than as true IB. I've been looking for woofers with as low a resonant frequency as possible, and a Qts of 0.4-0.5, if I should be looking for something else someone please say so. My current choice is the HiVI M8a, with an fs of 30Hz and Qts of 0.43. Anyone know of a better 8" woofer for IB use? I've used the M8N in another project before and loved the sound, coincidentally the M8a looks to have good specs for IB use.
I'm not as sure on a choice for the tweeter. Definately will need the best off-axis response as possible, so should I just be looking at domes? Right now I'm considering the Dayton RS28a for it's low crossover capability.
Another thing I'm worried about really is the off-axis response, since the speaker locations are by the ceiling, maybe 10ft+ high. The room is pretty large, maybe 30-35' x 10-12'.
I'm also thinking about painting the speaker baffles to match the paint in the room, since I'm concerned about the grills not clearing the woofer surrounds completely. So a tweet with a removable baffle would be nice so I could paint that, too. Another reason the RS28a is looking so tempting.
Due to location restraints, putting together a sealed in-wall enclosure is out of the question. Where a sealed Qtc .707 box would handle 20W (for the M8a), the IB config would only handle 20W with a 2nd order HPF at fs, and that loses a solid 1dB for most of the bass range compared to the Qtc .707. The only problem is, as I mentioned before, I'm not sure that I could fab an in-wall enclosure for these. So the best suited 8" driver for IB may be the best bet. With no HPF they will handle close to 10W, which I think will be plenty considering they don't turn up the volume loud often (if ever) and mostly listen to classical and jazz.
The cut-out locations:
So far I think I have a design pegged. Modelled using raw .frd info from the drivers, the HiVi M8a and the Dayton RS28a. Both are aluminum and should match voices nicely, I'm thinking.
I worked up an xover based on the actual physical layout, and an off-axis listening location @ 4m away and 2m down. Kinda taking advantage of the fact that the sitting/listening area and the location of the speakers is pretty well set in stone.
physical layout for modelling:
The model achieves 2nd-order roll-off for the LPF at 1300Hz (actual filter is below 1kHz or so), 4th order roll-off in the HPF at 1300Hz, series L-pad resistance of 2 ohms, and includes a series LCR notch at the woofer's breakup mode (2khz). Impedance stays above 6 ohms, which is desirable. This comes to about 10 components per crossover and puts the total price under $400.
Theoretical response is within +/-2dB and I'm not sure much could be done to improve it? Further off-axis response and power response look pretty great also. Actual on-axis response is strong in the high end and less flat, but I don't see anyone climbing on a ladder to listen to these at that level. Phase on the model does wrap like crazy but I'm not too concerned about that.
Does anyone see any problems with this design or approach? I feel pretty satisfied with it and am ready to order parts any day now. Since I've heard the Bagby software is pretty accurate, I'm kinda banking on that for designing around off-axis response.
Any comments or suggestions would be highly appreciated.
Buying parts and will start construction in the next few days.
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