Looking forward to these drivers. Here is a simple scaling of my current 8in TL for an RS225-8 down by factor of 6.5/8 or 0.81x. This was a lazy test in Akabak to see if the Purify could even work in a TL. It’s quite smooth and flat and I wonder if people consider 41Hz F3 not low enough given all the super compact designs with very long vents.
The sound of a woofer in a tapered PMC style TL with a huge vent opening cross section is very impressive. There is no compression and the dynamic range seems to be increased. The driver can be played even louder than usual with little sign of distorting or stress. I feel like it improved the RS225’s range by 10x. It reduced distortion and increased clarity while preserving a very articulate and resolving bass.
The sound of a woofer in a tapered PMC style TL with a huge vent opening cross section is very impressive. There is no compression and the dynamic range seems to be increased. The driver can be played even louder than usual with little sign of distorting or stress. I feel like it improved the RS225’s range by 10x. It reduced distortion and increased clarity while preserving a very articulate and resolving bass.
I simply scaled this design by 0.81x (6.5/8.0). But 80% is about right. Internal TL width in simulation was 7in, so add wall thickness for two sides. If 12mm ply then total width is 8in.
Full scale plans used 3/4in BB ply, so maybe use 12mm BB plywood all around except baffle keep at 3/4in for stiffness. 80% of 40in is about 1.3m tall.
Details of that speaker build here:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
Full scale plans used 3/4in BB ply, so maybe use 12mm BB plywood all around except baffle keep at 3/4in for stiffness. 80% of 40in is about 1.3m tall.
Details of that speaker build here:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
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After some excitement with the UPS delivering the package to the wrong house, I got my drivers today! Luckily the neighbor knows me and everything worked out. After wiping the box down with bleach spray, I can access the drivers sooner than the usual quarantine period. They were cocked diagonally in the box (half the bezel was under the cardboard and other half on top). Both were like that - luckily the paper cones (rather thin and light) were not damaged. They look unique. Very different than other woofers I have seen or felt. Much more compliant soft suspension than I thought they would be.
Thank you, Norman Tracy!
I am looking forward to hearing them.
Cheers,
X
Thank you, Norman Tracy!
I am looking forward to hearing them.
Cheers,
X
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I just put my two drivers to the DATS TS parameters measurement. I used the added mass technique with 95.2g of plastic modeling clay over Blue tape to protect the cone from the oil in the clay. These are the two closest matched drivers I have ever seen - a testament to the quality control of the manufacturing. The lines basically are on top of one another and the TS parameters are very consistent.
The measured Qts is very close to the factory value, fs is very close, and sensitivity of 88.8dB at 2.83v are excellent. These are the places where values are sometimes exaggerated by manufacturers. But not this time - well done Purifi!
Driver #1:
f(s) = 32.3 Hz
Q(ts) = 0.3055
V(as) = 21.04 liters (0.7429 cubic feet)
SPL = 85.33 dB SPL 1W/1m
R(e) = 3.6 Ohms
Q(es) = 0.3212
Piston Diam. = 129.8 mm (5.11 in.)
SPL = 88.8 dB SPL 2.83 Vrms
C(ms) = 0.856 mm/N
L(e) = 0.2245 mH at 10kHz
Q(ms) = 6.249
BL = 8.034
n(0) = 0.2104 %
M(ms) = 28.37 grams
Driver #2:
f(s) = 32.3 Hz
Q(ts) = 0.307
V(as) = 21.04 liters (0.7429 cubic feet)
SPL = 85.31 dB SPL 1W/1m
R(e) = 3.57 Ohms
Q(es) = 0.3231
Piston Diam. = 129.8 mm (5.11 in.)
SPL = 88.81 dB SPL 2.83 Vrms
C(ms) = 0.856 mm/N
L(e) = 0.222 mH at 10kHz
Q(ms) = 6.154
BL = 7.976
n(0) = 0.2092 %
M(ms) = 28.37 grams
DATS 2.1.1
For easy reference, here is the factory spec:
The measured Qts is very close to the factory value, fs is very close, and sensitivity of 88.8dB at 2.83v are excellent. These are the places where values are sometimes exaggerated by manufacturers. But not this time - well done Purifi!
Driver #1:
f(s) = 32.3 Hz
Q(ts) = 0.3055
V(as) = 21.04 liters (0.7429 cubic feet)
SPL = 85.33 dB SPL 1W/1m
R(e) = 3.6 Ohms
Q(es) = 0.3212
Piston Diam. = 129.8 mm (5.11 in.)
SPL = 88.8 dB SPL 2.83 Vrms
C(ms) = 0.856 mm/N
L(e) = 0.2245 mH at 10kHz
Q(ms) = 6.249
BL = 8.034
n(0) = 0.2104 %
M(ms) = 28.37 grams
Driver #2:
f(s) = 32.3 Hz
Q(ts) = 0.307
V(as) = 21.04 liters (0.7429 cubic feet)
SPL = 85.31 dB SPL 1W/1m
R(e) = 3.57 Ohms
Q(es) = 0.3231
Piston Diam. = 129.8 mm (5.11 in.)
SPL = 88.81 dB SPL 2.83 Vrms
C(ms) = 0.856 mm/N
L(e) = 0.222 mH at 10kHz
Q(ms) = 6.154
BL = 7.976
n(0) = 0.2092 %
M(ms) = 28.37 grams
DATS 2.1.1
For easy reference, here is the factory spec:
An externally hosted image should be here but it was not working when we last tested it.
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DaveFred, no shipments from group buy have been dispatched to Canada. Yours and another chap were the two members of the GB in Canada. You should find an email from me sent today with further shipping details so we can get your drivers on their way. The other chap had to return to Australia due to pandemic so his drivers are another issue also worked today.
lbstyling it would be awhile before I would organize another group buy. As the paragraph above illustrates I have trailing end details remaining to work out on this GB first. Also I note your union jack so I will also say the math of PURIFI transducers GBs only work when all recipients are in the same national zone. Purifi require the shipment to go to one address to get the quantity discount and going for example Denmark to USA then back across an ocean again that second shipping cost basically eats the savings the GB delivered. Part of this is because Purifi have a very favorable shipping deal with DHL, they can ship a pair of woofers for half what it costs me. Now that I have spent a week with the Purifi drivers I will testify at the full cost for a pair from Purifi they are a great deal.
Xrk971 you are most welcome, that was not the excitement I prefer Saturday while we looked for your drivers. I am curious was it you and your neighbor who surfaced the shipment or was my working with UPS customer service to return the driver part of the success? Your report on the shifting of the drivers within the Purifi boxes shows UPS certainly as rougher handlers compared to the Denmark to USA leg under DHL. I opened all 46 of the Purifi boxes as I repacked and none of them showed the shifting in your pics.
Xrk971 I await with great interest your results of both the dual PR box and transmission line. Among my designs envisioned for the PURIFI mid-woofer is a Audio Physics’ style slim petite floor stander. While loving that style one must grapple with the fact they are little wooden organ pipes and I see transmission lines as a way to deal with that organ pipe resonance issue. With the added benefit of all those dividers acting as extra bracing dividing and potentially conquering panel talk vibrations.
For those like Xrk971 considering non-Purifi passive radiators be aware Purifi point out their PR’s incorporate features like the constant area vs. displacement surrounds that address the same distortions as the woofers. Of course I have their PRs and am in the new-toy honeymoon period. Nevertheless I am equality curious to hear how others fare with less expensive PRs. It seems to me the tactic there is to oversize the PRs to help keep their excursions down thereby minimizing nonlinear behaviors. Also a datapoint to keep in mind is Purifi tune their PRs to 19 Hz with no added mass so obviously in there opinions low frequency tunings are the way to go.
lbstyling it would be awhile before I would organize another group buy. As the paragraph above illustrates I have trailing end details remaining to work out on this GB first. Also I note your union jack so I will also say the math of PURIFI transducers GBs only work when all recipients are in the same national zone. Purifi require the shipment to go to one address to get the quantity discount and going for example Denmark to USA then back across an ocean again that second shipping cost basically eats the savings the GB delivered. Part of this is because Purifi have a very favorable shipping deal with DHL, they can ship a pair of woofers for half what it costs me. Now that I have spent a week with the Purifi drivers I will testify at the full cost for a pair from Purifi they are a great deal.
Xrk971 you are most welcome, that was not the excitement I prefer Saturday while we looked for your drivers. I am curious was it you and your neighbor who surfaced the shipment or was my working with UPS customer service to return the driver part of the success? Your report on the shifting of the drivers within the Purifi boxes shows UPS certainly as rougher handlers compared to the Denmark to USA leg under DHL. I opened all 46 of the Purifi boxes as I repacked and none of them showed the shifting in your pics.
Xrk971 I await with great interest your results of both the dual PR box and transmission line. Among my designs envisioned for the PURIFI mid-woofer is a Audio Physics’ style slim petite floor stander. While loving that style one must grapple with the fact they are little wooden organ pipes and I see transmission lines as a way to deal with that organ pipe resonance issue. With the added benefit of all those dividers acting as extra bracing dividing and potentially conquering panel talk vibrations.
For those like Xrk971 considering non-Purifi passive radiators be aware Purifi point out their PR’s incorporate features like the constant area vs. displacement surrounds that address the same distortions as the woofers. Of course I have their PRs and am in the new-toy honeymoon period. Nevertheless I am equality curious to hear how others fare with less expensive PRs. It seems to me the tactic there is to oversize the PRs to help keep their excursions down thereby minimizing nonlinear behaviors. Also a datapoint to keep in mind is Purifi tune their PRs to 19 Hz with no added mass so obviously in there opinions low frequency tunings are the way to go.
I walked around my neighborhood looking for houses with a porch and saw one with a box of approximate shape as what you showed shipping. What was surprising was that it was on a different street name and house number, so the driver was way off. Usually, just by house number. I would have eventually gotten the drivers as I am friends with this particular neighbor, it just would have taken time as they let packages sit for a day or two with quarantine.
I could not resist the temptation to just connect it to my existing XO developed for the RS180P (8ohms) and the RS28F-4. I powered it with my TPA3255 Class D amp (good for maybe 300w at 4ohms) and to my surprise and delight, it sounds pretty good and balanced. Not perfect but good enough to enjoy 5 test tracks. Infected Mushroom's Pink Nightmares has a pounding bass note that doesn't bother this driver at all. The bass is there and sounds like an 8in or 10in driver. The distortion is very low - I can crank it loud and it doesn't complain. The rear PR's are really pumping air. I think the use of the Purifu PR's with special surround and same suspension will be key to keeping the non-linear distortion down. These cheap $15 Dayton's don't sound bad though and probably OK as long as SPL is not too high. Very promising start! Now I need to take some careful FRD's. But can't stop listening to them to do so!
Here are the plots corresponding to the ZMA files that I will be usning to develop the XO's:
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Received my woofers in perfect condition. Thank you, so much, Norman!
They look much better than I expected. While checking them out I noticed something interesting. They have two "cones". There is a second cone in the back that has an odd shape and elliptical holes near the spider. I wonder what this does for the design.
They look much better than I expected. While checking them out I noticed something interesting. They have two "cones". There is a second cone in the back that has an odd shape and elliptical holes near the spider. I wonder what this does for the design.
Here are the raw driver responses as measured in the box with the dual passive radiotors, and the raw response of the RS28F in a WG300 waveguide, and the predicted combined response (blue) with the measured combined response for an acoustic center offset of only 20mm. In Xsim, this refers the distance that the acoustic center of the tweeter is set back behind acoustic center of the woofer. Thanks to the waveguide and placement of the mic along the woofer axis, this helped to keep this distance very small. This data was taken at 0.5m away and with 2.00Vrms provided by my reference TPA3255 Class D amp.
Here is the setup:
Here are the raw responses (red and green) and the predicted (blue) vs measured (yellow) combined curves:
Here is the setup:
Here are the raw responses (red and green) and the predicted (blue) vs measured (yellow) combined curves:
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Here is my latest speaker made using the PTT6.5 - A transient perfect passive Harsch XO.
https://www.diyaudio.com/forums/mul...using-ptt6-5-rs28f-waveguide.html#post6211942
Simple XO Schematic:
Prototype XO Implementation:
Crossover Curves:
Step Response:
https://www.diyaudio.com/forums/mul...using-ptt6-5-rs28f-waveguide.html#post6211942
Simple XO Schematic:
Prototype XO Implementation:
Crossover Curves:
Step Response:
You can see that I am either going to need better passive radiators or make a TL. The PTT6.5 can really move a lot of air - check out the video here:
XRK Audio on Instagram: “Purifi PTT6.5 and RS28F in a WG300 waveguide in box with dual 6.5in passive radiators weighted with 26grams of added mass (each). That’s a…”
XRK Audio on Instagram: “Purifi PTT6.5 and RS28F in a WG300 waveguide in box with dual 6.5in passive radiators weighted with 26grams of added mass (each). That’s a…”
