I have had some interest in the crossover PCB's I built for the XSD. I am more than happy to do a group buy, but we'd need at least a few people to make it viable. I checked JLCPCB recently and shipped to me, 10x boards, on 2mm PCB, 2oz copper, ENIG finish, it was $16.99/board, there would be shipping costs to you the end buyer as well. As with any order at JLCPCB, the more we order the cheaper things will get.
Let me know if there is interest and we can hopefully get some builders PCB's for their XSD's.
Let me know if there is interest and we can hopefully get some builders PCB's for their XSD's.
I am interested as I have a number of good parts in storage I will have to look through to see if any correct values and I have 8" woofers so some will be different anyway or I am going to bi amp them. (I am considering fully active as well or going back to the smaller woofers....so many projects going on, other speakers as well in the idea stage at least since not sure these will work out in our RV...)
If it looks like you get enough interest I will likely go ahead and get a pair.
If it looks like you get enough interest I will likely go ahead and get a pair.
FWIW, I made a spreadsheet of multiple drivers comparing VD (cm^3, SD and XMAS) values to play what-if questions for sizing the SLOB array.
I have a few SLOB related questions.
After reading the thread, there are the 6.5" and 8" HF quarter wavelength cutoffs and 20-40% aggregate SD slot area concerns.
The GRS 8SW-4 8" has 3.1X the VD of the GRS 6PR-8 6.5". Some more expensive drivers (not listed, e.g. Peerless SLS 8" with 8.4 XMAS and 4.3X VD) have higher relative ND ratios via longer throw XMAS.
Are there any concerns about over-driving a SLOB slot with higher VD values ( chuffing, peaks, etc.) ?
Are there any drawbacks for using "subwoofer" drivers with higher ND values ?
Thanks much.
I have a few SLOB related questions.
After reading the thread, there are the 6.5" and 8" HF quarter wavelength cutoffs and 20-40% aggregate SD slot area concerns.
The GRS 8SW-4 8" has 3.1X the VD of the GRS 6PR-8 6.5". Some more expensive drivers (not listed, e.g. Peerless SLS 8" with 8.4 XMAS and 4.3X VD) have higher relative ND ratios via longer throw XMAS.
Are there any concerns about over-driving a SLOB slot with higher VD values ( chuffing, peaks, etc.) ?
Are there any drawbacks for using "subwoofer" drivers with higher ND values ?
Thanks much.
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Another potential 8" driver with 3.6X the VD (149.7 cm^3) is the Dayton Audio RS225-8.
It has a lower FS (28.3 vs 69) and supposedly low distortion, but with a higher price tag.
4 of these DA drivers should approximate @ 14 of the GRS 6.5" drivers with respect to aggregate VD.
It appears @xrk971 has already used the DA RS225 in other builds.
Love the looks of this 4 bass driver build.
It has a lower FS (28.3 vs 69) and supposedly low distortion, but with a higher price tag.
4 of these DA drivers should approximate @ 14 of the GRS 6.5" drivers with respect to aggregate VD.
It appears @xrk971 has already used the DA RS225 in other builds.
Love the looks of this 4 bass driver build.
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It is @Earplay2020's build starting with post #12.
I like the way he recessed the bass stack into the relief in the back of the front facade panel.
It looks like he made additional reliefs for the front edges of the speaker bezels to keep the slot length as short as possible.
I like the way he recessed the bass stack into the relief in the back of the front facade panel.
It looks like he made additional reliefs for the front edges of the speaker bezels to keep the slot length as short as possible.
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I believe that standing wave issues related to the depth of the slot are what limit the upper frequency at which the bass array can be practically used. However, by making the top and bottom of each chamber flared towards the opening, one could likely increase the upper frequency substantially. I have guy cutting some panels out for me per the attached sketch using 6 Dayton DS215-8 8" Designer Series Woofers per side....Will post back once completed. I only plan to use them up to 80-100Hz but will measure higher to confirm the theory...
RS225-8 can work well. Series parallel 4 gives nominal 8ohms. It has low Qts so magnet is more powerful and can drive the air more authoritatively down to its Fs. The slot depth is deeper though so XO will need to be about 370Hz vs 470Hz. The biggest drawback is that the driver is very flat response well above this range so it’s a shame to only be using it up to 370Hz.
@cab - the 1/4-wave equation is what sets the upper bandwidth. Your slot depth above is about 10.5in plus baffle thickness 0.75in for 11.25in. 11.25in x 0.0254m/in = 0.286m. Since this 1/4 wave full wave is 4x0.286m=1.14m. Speed of sound is 342m/sec so frequency is 342m/sec / 1.14m = 300Hz. This will be a -12dB/octave falloff. Place a -12dB/oct electrical low pass at same spot and you get a -24dB/oct (4th order) filter for the price of a second order.
@cab - the 1/4-wave equation is what sets the upper bandwidth. Your slot depth above is about 10.5in plus baffle thickness 0.75in for 11.25in. 11.25in x 0.0254m/in = 0.286m. Since this 1/4 wave full wave is 4x0.286m=1.14m. Speed of sound is 342m/sec so frequency is 342m/sec / 1.14m = 300Hz. This will be a -12dB/octave falloff. Place a -12dB/oct electrical low pass at same spot and you get a -24dB/oct (4th order) filter for the price of a second order.
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@xrk971 ,
Thanks for the confirmation on the RS225-8. Do you have any guess on what the noise level improvement would be over the GRS ?
You have documented -50dB to -55dB down @ 50Hz for the GRS.
370Hz should be fine for my application but the option of higher is a nice to have.
I am also looking for lower clean bass extension.
Thanks for the confirmation on the RS225-8. Do you have any guess on what the noise level improvement would be over the GRS ?
You have documented -50dB to -55dB down @ 50Hz for the GRS.
370Hz should be fine for my application but the option of higher is a nice to have.
I am also looking for lower clean bass extension.
The MCM 3231 only has an xmax of 3.5 mm, so not much more than the 6.5" and 8" GRS woofers, which are both 3 mm. It does, however, have a much lower Fs so I'm wondering how much lower the extension on this design was? Earplay indicates, "it's not the last word in bass", but what is? Could we see an F3 of 35 Hz? 30 Hz with DSP perhaps? Thinking about 6 of them per channel on a separate amp with DSP to drive the nominal 6 ohm load for 2P3S wiring.
The issue I see with this layout is that a significant portion of each cone's movement will be trying to blow past the edges of the front panel. The air impingement on that panel could cause the cone to be loaded unevenly and cause distortion. I would want more free air behind the drivers.