@CharlieLaub
Any updates?
I find myself in a similar quest with my project, though I am looking for bass for a planar/ribbon ob. I am setting up a BG rd-50 driver along side a Magnepan 60" ribbon tweeter on an ob. I would like to use a 10" or 12" woofer from say 50-80Hz up to the rd-50 at about 350Hz, and fill in below with 4 sealed 12" subs in a distributed bass array. I have a pair of AE Dipole 18" I was thinking to use them in a pair of u frames and place them next to the mid/tweeter baffles. Not sure if that would work nor sure I want to give up all that real estate so I am looking into using the dipole 18's as part of the distributed sub system and find some suitable 10" or 12" driver for the upper bass as mentioned above. I don't want to mount them on the same baffle as the mid/tweeters and was considering putting them in a round u frame aligned with a hole in the mid/tweeter baffle. I would like to use an ob mid bass but just 1 driver per side. I am considering either the AE dipole 12 or waiting for the Purifi 10", though not sure if it will be suitable for OB. What did you end up doing? Thanks....
Any updates?
I find myself in a similar quest with my project, though I am looking for bass for a planar/ribbon ob. I am setting up a BG rd-50 driver along side a Magnepan 60" ribbon tweeter on an ob. I would like to use a 10" or 12" woofer from say 50-80Hz up to the rd-50 at about 350Hz, and fill in below with 4 sealed 12" subs in a distributed bass array. I have a pair of AE Dipole 18" I was thinking to use them in a pair of u frames and place them next to the mid/tweeter baffles. Not sure if that would work nor sure I want to give up all that real estate so I am looking into using the dipole 18's as part of the distributed sub system and find some suitable 10" or 12" driver for the upper bass as mentioned above. I don't want to mount them on the same baffle as the mid/tweeters and was considering putting them in a round u frame aligned with a hole in the mid/tweeter baffle. I would like to use an ob mid bass but just 1 driver per side. I am considering either the AE dipole 12 or waiting for the Purifi 10", though not sure if it will be suitable for OB. What did you end up doing? Thanks....
Here is an update of sorts:
I just recently finished a project that is a 3-way dipole. For the woofer section in each speaker I used four SB Acoustics Satori WO24P-8 in a 24x24" baffle that sits on the floor. The clean, low distortion bass I am getting from these drivers is amazing and bass extension is good with F3 = 36Hz. I am paralleling all four drivers and then using a 3.3uH inductor in series with that to tilt the response down above 70 Hz. This also has the added bonus of reducing 3rd order distortion products a la the Purifi tech note on that. I use the "woofer panel" up to 300Hz, where I cross over to a 7" that I am using as a midrange up to 2kHz. AMT tweeter after that.
With that system finished, I am starting to work on the next one, which is more of a test bed for some ideas. It's another dipole 3-way but using four 10" drivers per side in a slightly different configuration. For now I am building it with four ScanSpeak 26W-4534G00. These are very good drivers but I intend to eventually replace them with the Purifi 10 once they become generally available. They are just about the same size and same TS parameters except the Purifi will have about twice the Xmax and mechanical limit, plus the HD and IMD will be lower. It will use a 6" midrange and AMT tweeter as before.
I decided to wait for the Purifi 10 over the 8 because the extra total displacement (Xmax*Sd) is very helpful in these dipole systems with relatively small baffles. I've pretty much given up on large drivers for OB, and prefer instead to use multiple smaller ones. I like this approach because with really, really good drivers I can make a 3-way dipole system, or with more modest 7" or 8" home audio woofers I can make a system that is 3-way dipole plus a sealed subwoofer, crossed around 75 Hz.
I just recently finished a project that is a 3-way dipole. For the woofer section in each speaker I used four SB Acoustics Satori WO24P-8 in a 24x24" baffle that sits on the floor. The clean, low distortion bass I am getting from these drivers is amazing and bass extension is good with F3 = 36Hz. I am paralleling all four drivers and then using a 3.3uH inductor in series with that to tilt the response down above 70 Hz. This also has the added bonus of reducing 3rd order distortion products a la the Purifi tech note on that. I use the "woofer panel" up to 300Hz, where I cross over to a 7" that I am using as a midrange up to 2kHz. AMT tweeter after that.
With that system finished, I am starting to work on the next one, which is more of a test bed for some ideas. It's another dipole 3-way but using four 10" drivers per side in a slightly different configuration. For now I am building it with four ScanSpeak 26W-4534G00. These are very good drivers but I intend to eventually replace them with the Purifi 10 once they become generally available. They are just about the same size and same TS parameters except the Purifi will have about twice the Xmax and mechanical limit, plus the HD and IMD will be lower. It will use a 6" midrange and AMT tweeter as before.
I decided to wait for the Purifi 10 over the 8 because the extra total displacement (Xmax*Sd) is very helpful in these dipole systems with relatively small baffles. I've pretty much given up on large drivers for OB, and prefer instead to use multiple smaller ones. I like this approach because with really, really good drivers I can make a 3-way dipole system, or with more modest 7" or 8" home audio woofers I can make a system that is 3-way dipole plus a sealed subwoofer, crossed around 75 Hz.
Interesting stuff!
What I keep in mind is the definition of X max mechanical where the driver literally hits the limits of motion where things are damaged and X Max listed on the data sheet.
Data sheet X Max is the limit of a woofer motion where distortion hits 10%.
For a sub woofer data sheet X Max is at 20% distortion.
Thanks DT
What I keep in mind is the definition of X max mechanical where the driver literally hits the limits of motion where things are damaged and X Max listed on the data sheet.
Data sheet X Max is the limit of a woofer motion where distortion hits 10%.
For a sub woofer data sheet X Max is at 20% distortion.
Thanks DT
@CharlieLaub: Very interesting and the success of your woofer panel augers well for my forthcoming dipole bass solution which will use 4 x AE Dipole 12 woofers per side.
I see those Satori woofers have a Qts of 0.38, which just goes to show that high Qts is not essential for OB.
Very much looking forward to hearing how the Purifi 10“ perform! They’re going to cost you deep in the purse as Sandy Denny once sang but I suspect they will be sensational.
I see those Satori woofers have a Qts of 0.38, which just goes to show that high Qts is not essential for OB.
Very much looking forward to hearing how the Purifi 10“ perform! They’re going to cost you deep in the purse as Sandy Denny once sang but I suspect they will be sensational.
On the subject of compactness, there may be merit in considering use of the "spaced tandem" configuration for pairs of woofers. This emulates an H or U open baffle without any woodwork (or cavity resonances), by maintaining a wodge of air in between the cones as the cones move.
Performance in practice seems to be about equal to the more conventional side-by-side positioning of the drivers.
An example is described in this thread:
https://www.diyaudio.com/community/...m-open-baffleless-full-range-speakers.374043/
Performance in practice seems to be about equal to the more conventional side-by-side positioning of the drivers.
An example is described in this thread:
https://www.diyaudio.com/community/...m-open-baffleless-full-range-speakers.374043/
@Studley Yes, as long as there are at least a few inches separating the two drivers it's liek two separate dipoles in terms of SPL. When they are very close or touching (assuming magnets out, driver mounting frame facing each other) then the effect goes away and they act just like a single driver in terms of frequency response and SPL.
Did you have a look into SB34NRXL75-8? It's one of the gems in SB Acoustics lineup, THD is compareable to these ScanSpeaks (which are the best I measured). And sensitivity is pretty good, I use it up to 500hz.
But when money is no question ... these 10" Purify look exceptional.
But when money is no question ... these 10" Purify look exceptional.
Have you considered an adaptation of this for bass:
https://www.diyaudio.com/community/posts/7414921/
Give the youtube clips a listen....
https://www.diyaudio.com/community/posts/7414921/
Give the youtube clips a listen....
Have a look here:
https://hificompass.com/en/speakers/measurements/sbacoustics/sb-acoustics-sb34nrxl75-8
https://hificompass.com/en/speakers/measurements/scan-speak/scanspeak-32w/4878t01
THD of the SB is on par when not even a little better. It has a longer voice coil. Even less membrane weight. Very good venting, these drivers can take power.
LF performance of the 20cm SB Acoustics is not on par with ScanSpeak, but this one ...
You can also have a look into their 10" lineup. These have the same 3" coil and similar motor as the 12" and a HUGE venting hole. Pretty cool for a HiFi chassis.
There is also a 16R 12" with high Qts - but the motor is different to the NRXL, not sure if t performs compareable.
@CharlieLaub: In Troy’s recent video about his design study for a bass cab using 2 x 10” Purifi woofers (drool) he mentions that Lars told him that the distortion levels of their 10” woofer is so low that their test equipment can’t measure it. If you read this Lars perhaps you’ll tell us more ?
Purifi already published data on the PTT10, so obviously the distortion level can be measured.
What I find interesting about the HD levels is that they do not climb below 100Hz like most drivers. Instead they stay relatively flat down to IIRC 30Hz or so. This might due to the Purifi surround design, which helps to keep Sd constant as the cone undergoes greater amounts of excursion. For a driver with a normal half-roll surround, Sd modulation is causing some distortion to occur.
In any case, take a look at the driver info listed on the Purifi web site and judge for yourself. IMHO this driver represents a leap forward in driver technology compared to all that have come before it.
What I find interesting about the HD levels is that they do not climb below 100Hz like most drivers. Instead they stay relatively flat down to IIRC 30Hz or so. This might due to the Purifi surround design, which helps to keep Sd constant as the cone undergoes greater amounts of excursion. For a driver with a normal half-roll surround, Sd modulation is causing some distortion to occur.
In any case, take a look at the driver info listed on the Purifi web site and judge for yourself. IMHO this driver represents a leap forward in driver technology compared to all that have come before it.
This is not unique to Purifi, and already at 95db the measurements in the bottom end start rising as normal.
Just as with any other woofer.
You will find the same behavior in some other well designed woofers, i don't know of any other 10's though.
Linked a few 15" examples below.
All 3 drivers have different surrounding designs, soft parts, cone materials, and very different motor structures / tech.
So the Purifi surround is not the likely decisive solution.
Attachments
Measurement microphones have a lot of noise, esp 1/4" ones. So THD at lower levels is probably masked from that. But as you raise level you are able to do proper measurements again.
Our Purifi surround is only part of the solution. The rest cones from the innovations in the motor design and suspension. Measurements: distortion at this low level is definitely measurable but but challenging since the noise floor of the mics are close. We measure at 40cm distance rather than 1m which increases the SNR.
The 10” has the advance of both higher Sd and lower fs compared to its smaller siblings. This pushes the corner where the LF distortion rises further down. This corner involves the transition from compliance controlled motion to mass controlled.
The 8” has actually a little lower 3rd harmonic in the upper band compared to the 10” but gets beaten at LF
The 10” has the advance of both higher Sd and lower fs compared to its smaller siblings. This pushes the corner where the LF distortion rises further down. This corner involves the transition from compliance controlled motion to mass controlled.
The 8” has actually a little lower 3rd harmonic in the upper band compared to the 10” but gets beaten at LF