Sorry I did not comment on this before. I checked his writeup. Here is his SPL plot taken at 1m:
In the plot you can see that the dipole peak is at about 150 Hz. Above that frequency the on axis response is falling into the first null, but off axis is not. This makes it difficult to get the tonal balance right unless the crossover point is under 150Hz. If that is OK in your design, then this is fine, and the larger the baffle the less bass loss from dipole cancellation.
In my designs I aim for a crossover point between woofer and midrange of 300Hz, so Mr Crowe's 1.2m x 1.2m baffle is too large, and is causes the dipole peak to occur too low in frequency. I need to cross over at 300Hz to limit the demand put on the midrange, which in my designs is "nude". When I keep the baffle smaller I can push the dipole peak out to about 300Hz so I can achieve a 3-way design with mid and tweeter used nude.
For example, the response of a panel measuring 0.55m x 0.55m using four 8" drivers is shown below. I was comparing a ground plane measurement (in green) and one done with the mic at 46 inches above the ground, with both at a distance of 120 inches (about 3m). A series inductance was added to flatten the response, but you can still see that dipole peak is around 300Hz. I can cross this at 300Hz, but the bass below 50Hz needs some lift/EQ, or I can cross over to a subwoofer around there and use the woofer panel to higher SPL levels.
I agree with @Arez ‘s analysis.
As SPL goes down but H3 goes up, that means in relative terms, H3 is going up.
I come with data-
Here’s a Peerless 10” SLS model 830668 in
in a 1 cu ft fibreglass filled sealed box.
Note the rise in distortion under 100Hz.
Here is the Peerless 12” XXLS model 835017 in the same box. Now please ignore the distortion at 3KHz- the high SPL at that frequency has caused clipping at the input.
But note the pattern of H2 and H3 in the bass (sub 200Hz)
There IS a gentle rise in H2 and H3.
But the frequency response is dropping below 60Hz. So in relative to the fundamental, distortion IS rising.
Now here’s the PTT10.0X
NB. Of course SPL levels are not matched.
Ive cropped it to focus on what’s relevant- the bass.
But note the similar pattern.
As SPL droops down, distortion stays about the same. But in again, relative to the fundamental, that means it goes up!
Now look at the highlighted green line.
At under 30Hz, H2 is -40dB (1%) down.
So what does it look more like?
Less like the The 10” SLS?
And more like the 12” XXLS!
If you haven’t fallen asleep yet, what I’m showing is that the 10” PTT10.0X is better than the 10” SLS. But ALSO better than a 12” XXLS at 30Hz!
My 1 line conclusion:
The PTT 10” is cleaner in the bass than the 12” XXLS.
This is likely the lowest distortion 10” (sub)woofer available to buy in 2023. Bar none.
Buy with confidence @CharlieLaub !
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For the price, though, it would be worth considering if 2x 12" XXLS in a push-pull configuration would be superior, if space allowed.
Digikey is selling what they have left: https://www.digikey.com/en/product-highlight/p/peerless-by-tymphany/xxls-xls-driver-family
Mm, well, the point still stands with Dayton Ultimax or other value-oriented sub drivers.
Note that the page says:
This product is no longer manufactured and will no longer be stocked once stock is depleted.
There are currently 36 left...
I don't think that using two larger "value oriented" drivers will be comparable or superior to the Purifi PTT10. You can certainly get more total displacement, but that will likely come at a cost of a higher distortion level. I have built plenty of subs with lots of displacement, but few that sound really clean and that is what the PTT10 seems to offer more than just about any other driver, especially in the 10" size. This is especially the case for the particular type of loudspeaker I build, so YMMV on this.
Also belongs to the discussion to mention that, THD measurements are only really valid when from the same source, measured with the same equipment and noise floor as another one. Else one does not have reliable measurements.
Not that it is any big news. There is a reason why it is TOTAL Harmonic Distortion, and it is given in %.
In the electrical world, when too much THD is generated from Rectifiers etc. A simple resistive load of sufficient size lowers it considerably, as it is measured in % of total amount.
A simple visual example:
Not that it is any big news. There is a reason why it is TOTAL Harmonic Distortion, and it is given in %.
In the electrical world, when too much THD is generated from Rectifiers etc. A simple resistive load of sufficient size lowers it considerably, as it is measured in % of total amount.
A simple visual example:
@shrub0
No. Most are for internal R&D. Nothing publicly. Sometimes I post occasional measurements for NLA drivers, lest I be accused of favouritism. Also, I am careful to ensure comparative measurements were done in the same conditions (same equipment/day etc)
@Arez correctly surmised, interpretation is important, as comparative measurements under different conditions should be taken with caution. Also important is that SPL should be matched. It’s not trivial taking measurements and interpretation is even more challenging IMHO.
My measurements shouldn’t be compared with anyone else’s, to be clear. When it arrives I’ll measure the PTT10.0X in the same 1 cu ft fibreglass filled text box.
One thing to be aware of is that the Peerless series 12” frame is only 1.5” larger than the 10”
10” OD - 269mm
12” OD - 308mm
difference = 39mm = 1.5”
The SEAS L26ROY and PTT10.0X use the same frame size as the Peerless (X)XLS. So the 12” Peerless (X)XLS really are only 1.5” larger.
I can see why @john k... declined my offer to send him 12 XXLS for a NaO redesign- it really doesn’t offer much more, particularly in dipole/OB/baffleless arrangements.
The same with the late Sigfried Linkwitz Orions or LX521. It would have been an easy parts seller for SEAS if SL requested a 12” version. Tooling up might cost 4 figures, but not 5 figures. But it makes the whole cabinet at least 1.5” wider, and offering a tiny 1.5dB or less SPL.
We all know that slim is in…
@CharlieLaub
Most of the 12” or larger woofers with long excursions, don’t seem as clean in the upper bass, despite have more SPL capability down low.
No. Most are for internal R&D. Nothing publicly. Sometimes I post occasional measurements for NLA drivers, lest I be accused of favouritism. Also, I am careful to ensure comparative measurements were done in the same conditions (same equipment/day etc)
@Arez correctly surmised, interpretation is important, as comparative measurements under different conditions should be taken with caution. Also important is that SPL should be matched. It’s not trivial taking measurements and interpretation is even more challenging IMHO.
My measurements shouldn’t be compared with anyone else’s, to be clear. When it arrives I’ll measure the PTT10.0X in the same 1 cu ft fibreglass filled text box.
One thing to be aware of is that the Peerless series 12” frame is only 1.5” larger than the 10”
10” OD - 269mm
12” OD - 308mm
difference = 39mm = 1.5”
The SEAS L26ROY and PTT10.0X use the same frame size as the Peerless (X)XLS. So the 12” Peerless (X)XLS really are only 1.5” larger.
I can see why @john k... declined my offer to send him 12 XXLS for a NaO redesign- it really doesn’t offer much more, particularly in dipole/OB/baffleless arrangements.
The same with the late Sigfried Linkwitz Orions or LX521. It would have been an easy parts seller for SEAS if SL requested a 12” version. Tooling up might cost 4 figures, but not 5 figures. But it makes the whole cabinet at least 1.5” wider, and offering a tiny 1.5dB or less SPL.
We all know that slim is in…
@CharlieLaub
Most of the 12” or larger woofers with long excursions, don’t seem as clean in the upper bass, despite have more SPL capability down low.
These seem to be some of the best.. open baffle, with servo and amps.
https://www.rythmikaudio.com/GRci_OB.html
complete kits
https://gr-research.com/product-category/sub-series/
I was reading about matching woofers to Maggies and these are very hightly thought off.... servos are fast ( I got sealed Entec SW-5s but I'm thinking about open baffle dipoles..). the Purify woofers do not incorporate servo feedback.
https://www.rythmikaudio.com/GRci_OB.html
complete kits
https://gr-research.com/product-category/sub-series/
I was reading about matching woofers to Maggies and these are very hightly thought off.... servos are fast ( I got sealed Entec SW-5s but I'm thinking about open baffle dipoles..). the Purify woofers do not incorporate servo feedback.
Sure, the Rythmik and GR servo subwoofer product is good, if that is what you want or need.
The Purifi 10" driver will be a better match for the type of dipole project that I am building, where the woofer passband extends up to 300Hz. This is why larger and "subwoofer" type drivers don't work for me.
The Purifi 10" driver will be a better match for the type of dipole project that I am building, where the woofer passband extends up to 300Hz. This is why larger and "subwoofer" type drivers don't work for me.
I take it you’ve considered the RS315HF and RS390HF?
JonMarsh over at HTGuide used the RS315HFA-8 and confirms it does 300+Hz ok.
I don’t have experience with this driver series (my large goto was the TC Sounds LMS R or Ultra, now NLA) so I don’t know anything about vent/cone noises and/or reliability.
Since you might publish your design for others to build- supply seems to be reliable…
JonMarsh over at HTGuide used the RS315HFA-8 and confirms it does 300+Hz ok.
I don’t have experience with this driver series (my large goto was the TC Sounds LMS R or Ultra, now NLA) so I don’t know anything about vent/cone noises and/or reliability.
Since you might publish your design for others to build- supply seems to be reliable…
I have 4 sealed 12" Rythmik subs (DIY enclosure) with a MiniDSP 4x10HD and Multisub Optimizer and I'm very happy with the results. I wouldn't use them past 80 or 90Hz though.
Rythmik used to have a dual 8" servo sub...F8 I think, that was said to be very good to 200-250Hz. I remember an experienced person using dual 12" to 50Hz, F8 50-200Hz, and JBL M2 above. Unfortunately Rythmik discontinued the F8, I believe.
My midbass is open baffle (also mid and tweet) and I also have an eye on PTT10, but can't convince myself it's worth using it if 4x 12" sealed subs will tackle sub 60 or 70Hz. AE LO15 or LO12 might be better choices.
Yes, I'm gonna hold off for two more years to see if Magnepan comes out with their subwoofer.
Using the MiniDSP seems to work well for (sub)woofers.
Using the MiniDSP seems to work well for (sub)woofers.