New XO works well. Predicted is black and actual measured is orange:
The measured harmonic distortion is also much better. The big cluster of distortion at 1kHz is now gone:
Predicted Impedance is also easy to drive nominally at 6ohms and dip to 3ohm
Minimum:
This is what the XO looks like:
You can listen to it in mono here:
The measured harmonic distortion is also much better. The big cluster of distortion at 1kHz is now gone:
Predicted Impedance is also easy to drive nominally at 6ohms and dip to 3ohm
Minimum:
This is what the XO looks like:
You can listen to it in mono here:
If you had no wings, but a bigger front baffle, you'd have no need to add foam there.
Review what I said about those wings and this being a partial 're-closing' and the effects of cabinets (here part of it) acting as passive radiator and hence affecting the sound negatively.
EDIT: you do seem to have a special arrangement of the speakers here though. I expected them to be oriented differently for more front sound pressure. Maybe that does a play a part as well.
On the bench last night was a more permanent soldered point to point XO board for the new SLOB dipole with the PRV midrange. 13 components on a 3 way crossover is not too bad. I got one channel built and will make another one tonight. It seems soldered connections sound better than spring clip Wago connectors. No surprise there (resolution on mids mostly).
X, does the buffer add any gain?
Do you have plans to make boards for it available? You should
I think that is exactly right. If DIY does cannibalise sales of a commercial product it will only be to a negligible extent IMHO
Gave you thought about using the TPL 150 or 200 up top instead Of the planar + mid bass?
On the bench late last night was the second channel of the crossover. Now listening in stereo with fully soldered P2P crossovers.
I had to use a small 0.22R resistor to add DCR to one of the coils I used because I only had 20ga version left and other channel has 18ga. Other than that they are identical. I’m probably going to replace the bipolar electrolytic and MKP box cap on the woofer with a big MKP cap that’s on order. That will eliminate all electrolytics in the signal path.
Still need a midbass. The TPL only goes down to 1500Hz really before distortion sets in. To get the proper low distortion mids - really need a dynamic high efficiency PA cone. Or maybe a big dome but they are not dipole capable.
Re the SLOB arrangement, I was expecting to see all the woofers firing into the slot, but on one side you have the woofers facing out. Are you able to tell us more about the pros and cons of that arrangement?
Also, I see each pair of woofers has its own segregated slot rather than them all firing into one large slot. Again, are you able to comment on that?
Also, I see each pair of woofers has its own segregated slot rather than them all firing into one large slot. Again, are you able to comment on that?
The arrangement of the woofers with one magnet inside the chamber serves a couple of things: (1) it reduces the chamber volume to increase the upper bandwidth, and (2) it allows one cone to push in the positive direction while the other one pushes in the negative direction - this requires flipping polarity of driver facing out. Why would we want one to go in +ve direction while other goes -ve? This will help cancel out suspension induced distortion (mostly even order) due to asymmetric suspension non linearities. The drivers always “squeeze” air out of the chamber in amplifier +ve signal input. If you look at the distortion plot, the distortion is quite low compared to many speakers which typically have more of a rise as the bass frequency goes deeper. As you can see, the second harmonic distortion is reduced mostly and this is consistent with the theory due to asymmetric cancellation of the woofer arrangement. The higher third order distortion that remains will give the bass a bit more bite and snap. It’s still low, but this is intrinsic characteristic of the SLOB bass “sound” and why dynamics are crisp and clear. I would imagine this can be significantly improved even further with higher quality cast frame woofers, with low distortion motors, longer Xmax, etc.
I think a version of this using 6x RS225-8 8 ohm woofers would be probably the ultimate bass unit. Low distortion motor, 7mm Xmax, cast basket, shorting rings, stiffer cone, wide smooth bandwidth, 28Hz Fs. It would go to 30Hz is my guess. You could also do this with 8x RS180-8 as well but that might cost more and not go as deep. It would probably drop the distortion another 6-10dB in the bass department vs these stamped steel basket plain old woofers. With 8in woofers the crossover would need to be redone at 350Hz but the PRV is still good there.
One could go hog wild crazy money no object and use 6x to 8x Purifi 6.5in woofers. With 20mm Xmax and ultra low distortion motors, who knows what the bass could do? But We are talking serious cash here.
Why each chamber is separate? To keep the volume small to increase the upper bandwidth. Also the separator ribs provide structural support to withstand the massive pressure generated by the drivers pushing in and out. Making it one big chamber also introduces long resonance modes along the height of the 4 drivers. There is no advantage to making it one big chamber.
I think a version of this using 6x RS225-8 8 ohm woofers would be probably the ultimate bass unit. Low distortion motor, 7mm Xmax, cast basket, shorting rings, stiffer cone, wide smooth bandwidth, 28Hz Fs. It would go to 30Hz is my guess. You could also do this with 8x RS180-8 as well but that might cost more and not go as deep. It would probably drop the distortion another 6-10dB in the bass department vs these stamped steel basket plain old woofers. With 8in woofers the crossover would need to be redone at 350Hz but the PRV is still good there.
One could go hog wild crazy money no object and use 6x to 8x Purifi 6.5in woofers. With 20mm Xmax and ultra low distortion motors, who knows what the bass could do? But We are talking serious cash here.
Why each chamber is separate? To keep the volume small to increase the upper bandwidth. Also the separator ribs provide structural support to withstand the massive pressure generated by the drivers pushing in and out. Making it one big chamber also introduces long resonance modes along the height of the 4 drivers. There is no advantage to making it one big chamber.
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