Really looking forward to this. I have been using 2 of these in reaction cancelling mode.
Let's continue - SB23MFCL45-8. Don't forget, that's a longstroke, heavy membrane subwoofer chassis. I'm still interested how it looks up to 2-300Hz for my next project with this chassis.
The prototype housing I had on hand had a to small baffle hole - so the driver is mounted with the magnet outside! Don't take frequency response at higher frequencies to serious, there will be an influence.
While doing some wobbling to prepare the chassis I detected a liiiittle noise when swinging free air. That's not unusual, just the other dirvers are really dead silent till pretty high excursions (normally at 10Hz - so you only hear noises and higher THD).
THD is not Purify level but very good for such a heavy membrane long stroke chassis! SPL level <100Hz is 2-3dB lower as with the 10" chassis, keep them in mind when comparing THD curves - these are not level matched!
Still - THD at 30-80Hz is very good.
Volume was about 24L with sheepwool inside and magnet outside - plenty for this driver.
Looks good to me. L is changing with excursion/power at higher frequencies - High End chassis do better.
I will put 2 of these in a closed volume, on at the front, one at the back and use it as stand for my home cinema speakers to make them fullrange. Should be good for that.
The prototype housing I had on hand had a to small baffle hole - so the driver is mounted with the magnet outside! Don't take frequency response at higher frequencies to serious, there will be an influence.
While doing some wobbling to prepare the chassis I detected a liiiittle noise when swinging free air. That's not unusual, just the other dirvers are really dead silent till pretty high excursions (normally at 10Hz - so you only hear noises and higher THD).
THD is not Purify level but very good for such a heavy membrane long stroke chassis! SPL level <100Hz is 2-3dB lower as with the 10" chassis, keep them in mind when comparing THD curves - these are not level matched!
Still - THD at 30-80Hz is very good.
Volume was about 24L with sheepwool inside and magnet outside - plenty for this driver.
Looks good to me. L is changing with excursion/power at higher frequencies - High End chassis do better.
I will put 2 of these in a closed volume, on at the front, one at the back and use it as stand for my home cinema speakers to make them fullrange. Should be good for that.
I find this thread quite interesting. Thankyou @IamJF for collecting and sharing this data.
I use a pair of SB34NRX75-6's in my main active system (i.e. one per side). 70 liter closed box, with 6 dB of boost to EQ them flat down to 32 Hz. I am enthusiastic about these drivers, and as I have swapped out my midrange and tweeter several times, I have stuck with these big 12s. However, I have always preferred the sound when they run up no higher than 200 Hz. Whether the midrange is an SB17CAC35, a Satori MW16TX, or a Purifi PTT6.5M04-NFA, the best sound is when the lower crossover is about 200 Hz. If I cross at 300 Hz, there is a noticeable loss of clarity and detail in the lower midrange. Maybe the distortion profile is the reason?
j.
I use a pair of SB34NRX75-6's in my main active system (i.e. one per side). 70 liter closed box, with 6 dB of boost to EQ them flat down to 32 Hz. I am enthusiastic about these drivers, and as I have swapped out my midrange and tweeter several times, I have stuck with these big 12s. However, I have always preferred the sound when they run up no higher than 200 Hz. Whether the midrange is an SB17CAC35, a Satori MW16TX, or a Purifi PTT6.5M04-NFA, the best sound is when the lower crossover is about 200 Hz. If I cross at 300 Hz, there is a noticeable loss of clarity and detail in the lower midrange. Maybe the distortion profile is the reason?
j.
Yeah, the recess required is almost 15" diameter. But on the plus side, this generous flange means that the screw holes have a larger edge distance. It makes designing and machining the woofer hole stress free...
+1. 2x WO24-P-8 per channel net 94db. The graph looks like it is good up to around 650 Hz - 1000 Hz.
I'm working on a 4 way with the NRXL version, 2 per side critically dampened in 80l for each driver, crossed at 250 - 300 for upper drivers only and up to 80 - 90 for lower drivers. At this time considering the JBL 2261H for midbass duty. Working on a custom 3" dome made from a neo compression driver, which looks promising and a T34B on top.
I'm not that fond of the NRX75-6 used above 150 hz. It sounds too congested in that range to my ears. I suspect the motor on the NRXL is responsible for this. The soft high compliance suspension on these SB 12s is an issue in the midbass if the motor has offset BL, unless you run them in small enclosures. I believe this partially is why the NRXL sounds better in the upper midbass when in a larger enclosure.
I can't vouch for the other larger SB woofers except for the Satori WO24 which sounds very similar to the old Scanspeak M26WR-09-08 but not quite as clean in a sealed enclosure running up tp 300 hz. The Aeriel 10T used this driver.
No, never had that size here. I decided it's not enough upgrade to the ScanSpeak 20cm I used before. But looks like a nice speaker, esp the TX Version could be an interesting 2way with a waveguide tweeter and deep crossover.
Last chapter - it's late over here.
I did some TSP measurements. Small signal, very little exursion of the membrane. Added weight, 40g of blutack. I forgott to measure DC resistance per hand and not let the programm estimate it - so I redid all the measurements ...
The 10" brothers. left 6R, right 8R.
That's pretty different as the datasheets. Looks like pretty the same speaker just with different coils resistance. As I guessed after looking at the measurements. Q is very often higer when you measure as manufacturers tell us - also the reason I have higher Q in the subwoofer housing. But nothing dramatic her.
SB Acoustics wants to tells us Mms of 78g and 59g for these drivers. When someone bets for a few hunderd bucks I get out the knife and measure
but I would say these are pretty similar and not 20g different.
The 8" long stroke:
This fits nicely to the datasheet! Just with less Vas. Looks pretty good for such a long stroke chassis. Qms is pretty high.
A bunch of these should make a very nice bass array for normal people. The crazy guys take the 12", I settled with 6x SB29NRX75-6.
I did some TSP measurements. Small signal, very little exursion of the membrane. Added weight, 40g of blutack. I forgott to measure DC resistance per hand and not let the programm estimate it - so I redid all the measurements ...
The 10" brothers. left 6R, right 8R.
That's pretty different as the datasheets. Looks like pretty the same speaker just with different coils resistance. As I guessed after looking at the measurements. Q is very often higer when you measure as manufacturers tell us - also the reason I have higher Q in the subwoofer housing. But nothing dramatic her.
SB Acoustics wants to tells us Mms of 78g and 59g for these drivers. When someone bets for a few hunderd bucks I get out the knife and measure
but I would say these are pretty similar and not 20g different.
The 8" long stroke:
This fits nicely to the datasheet! Just with less Vas. Looks pretty good for such a long stroke chassis. Qms is pretty high.
A bunch of these should make a very nice bass array for normal people. The crazy guys take the 12", I settled with 6x SB29NRX75-6.
This is exciting (for me). I use these as a sub-woofer stand for a compact 4-way. The SB23MFCL45-8 are connected electrically in-phase in reaction cancelling configuration. This is the so-called bi-pole configuration. In my system they handle 20Hz-80Hz, The crossover at 80Hz is LR48. I like what they achieve. No complaints whatsoever.
Pretty much my configuration but in a mainly music system.
https://www.diyaudio.com/community/...ction-cancelling-woofers.402645/#post-7438801
If you connect them back-to-back like this, in-phase electrically, the radiation pattern will be bipole, so they will have an acoustical null on the driver axis and be acoustically in-phase at 90 degrees. So your sub box will need to be rotated 90 degrees to project the main lobe forward. planet10 explained this is the attached graphic. I connect the 2 drivers through the mounting holes with tensioned threaded steel rods. The reduction in transmitted vibration is spectacular.
I know that quite a few people question the bipole effect. It would be a great contribution if you could do some measurements of the polar response of the bipole configuration of 2 of these back-to-back. Or at least compare the FR on the driver axis, with the FR at 90 degrees off-axis.
I think you would have to try and get as close to free field as possible, since the radiation will be the same magnitude forwards and backwards and the room boundary reflections will potentially interfere with obtaining a clean signal. The measuring distance might also be an issue.
Would love to see some measurement data.
Attachments
Someone would need to send me one (Europe) ... not used in any project in the next future.
@Bon You use motion cancelation when I understood right? So both membranes move outwards at the same time?
Then you have 2 omni sources in phase - you get perfect omnidirectional radiation. For 100% sure.
What you describe would only happen at higer frequencies when runtime around the cabinet makes a difference! Then you get phase shifts and some funny patterns. But that's way out of the working range of these drivers.
I will use a little different setup. The main idea is a similar setup to Genelec W371A in it's basic mode. So you have 2 pretty different positions in the room for the drivers and SBIR/lambda/4 should be different and hopefully the dips are less pronounced. But you loose motion cancelation ... will do some tests with different positions of the drivers in the cabinet. (oh boy, this will be some work ... will not happen in the next few weeks)
https://www.genelec.com/w371a
@Bon You use motion cancelation when I understood right? So both membranes move outwards at the same time?
Then you have 2 omni sources in phase - you get perfect omnidirectional radiation. For 100% sure.
What you describe would only happen at higer frequencies when runtime around the cabinet makes a difference! Then you get phase shifts and some funny patterns. But that's way out of the working range of these drivers.
I will use a little different setup. The main idea is a similar setup to Genelec W371A in it's basic mode. So you have 2 pretty different positions in the room for the drivers and SBIR/lambda/4 should be different and hopefully the dips are less pronounced. But you loose motion cancelation ... will do some tests with different positions of the drivers in the cabinet. (oh boy, this will be some work ... will not happen in the next few weeks)
https://www.genelec.com/w371a
One TSP is missing. I can't unscrew the actual SB34NRXL75-8 cause I need it for my experiments. But I quickly measured a brand new out of the box one - better as nothing.
All these drivers seem pretty similar. Qts is lower with this one - as expected. Mms a little heavier, Vas smaller. SB Acoustics seem to measure different as I do . Bl is a lot higher with this driver! Btw they are pretty conservative with their Sd - I would have measured more with the "half surround rule", esp. with the 8" but I used a value similar to the original datasheet, they probably know better?
All these drivers seem pretty similar. Qts is lower with this one - as expected. Mms a little heavier, Vas smaller. SB Acoustics seem to measure different as I do
. Bl is a lot higher with this driver! Btw they are pretty conservative with their Sd - I would have measured more with the "half surround rule", esp. with the 8" but I used a value similar to the original datasheet, they probably know better?
Btw - now doing some break in at 10Hz. These drivers ... I "measured" +-11,5mm exursion with my simple setup - and there are NO NOISES at all!
There is a little wind noise in the video cause the big venthole is not working perfect cause the chassis is sitting on Isobond for decoupling, this is gone when you lift it and ventilation works normal. Also no THD to hear. Incredible.
The noise background comes from the fan of my AudioPrecision measurement system ... these are way to loud.
There is a little wind noise in the video cause the big venthole is not working perfect cause the chassis is sitting on Isobond for decoupling, this is gone when you lift it and ventilation works normal. Also no THD to hear. Incredible.
The noise background comes from the fan of my AudioPrecision measurement system ... these are way to loud.
I doubt you'll find a better 12" hifi woofer for the money which can do so much so well. I went through dozens of 12s until I ended up with the SB34NRXL75-8.
Your measured free air TSPs are close. SB measures with higher voltages. Fs and Qts will continue to drop over time. Be aware this driver will suffer cone sag over time if stored or installed horizontally.
Your measured free air TSPs are close. SB measures with higher voltages. Fs and Qts will continue to drop over time. Be aware this driver will suffer cone sag over time if stored or installed horizontally.
I never tested the Daytons. They are for sure good but I don't think they compete on this level.
Not all of the SB drivers are so good! I also measured their 20cm driver and they can't compete with ScanSpeaks. But also are cheaper.
At low frequencies all of the tested drivers have pretty good THD and a bigger asymmetration of BL should pop up there. I think the smaller drivers suffer more from this.
p.s.: just found measurements from 20cm SB Acoustics (paper or alu membrane, I think alu). These should be 2 in parallel - don't remember the detailed measurement conditions, was just a project consulted.
THD in lower midrange looks great - at low frequencies it's pretty high. That could be the Bl(x) influence. Didn't see that in the bigger drivers.
Not all of the SB drivers are so good! I also measured their 20cm driver and they can't compete with ScanSpeaks. But also are cheaper.
At low frequencies all of the tested drivers have pretty good THD and a bigger asymmetration of BL should pop up there. I think the smaller drivers suffer more from this.
p.s.: just found measurements from 20cm SB Acoustics (paper or alu membrane, I think alu). These should be 2 in parallel - don't remember the detailed measurement conditions, was just a project consulted.
THD in lower midrange looks great - at low frequencies it's pretty high. That could be the Bl(x) influence. Didn't see that in the bigger drivers.
