@tktran303: I know who them boyz are and where they come from. Bruno P. e.g. was already a living legend in the Low Countries before the rest of the world heard of him. Same with the Danes regarding loudspeaker design.
Boden,
I didn’t mean to give you lecture on the history of Purifi audio. If that is how it came across, then my apologies.
What I should have explained was that interview 1 year ago reveals much about the origin and genesis of the PTT transducer, and answers (and shows pictures to) your question regarding motor vs surround issue. Actually Lars does a deep dive, and takes apart the original PTT 6.5” woofer (PTT6.5 W04-01A; NLA) woofer, around halfway through the video.
If you’re a speaker nerd like me you might have watched the 2 hour “chat” between Erin and Lars. But if you’re not, I thought I would explain the context that led to the work that led to the discovery. 100 man-years of R&D to get that extra 20dB of lower distortion?
Yeah. I’d pay for that.
I didn’t mean to give you lecture on the history of Purifi audio. If that is how it came across, then my apologies.
What I should have explained was that interview 1 year ago reveals much about the origin and genesis of the PTT transducer, and answers (and shows pictures to) your question regarding motor vs surround issue. Actually Lars does a deep dive, and takes apart the original PTT 6.5” woofer (PTT6.5 W04-01A; NLA) woofer, around halfway through the video.
If you’re a speaker nerd like me you might have watched the 2 hour “chat” between Erin and Lars. But if you’re not, I thought I would explain the context that led to the work that led to the discovery. 100 man-years of R&D to get that extra 20dB of lower distortion?
Yeah. I’d pay for that.
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So the way I read this, is that when one can prevent any kind of (significant) excursion, this is not even a problem to begin with.
Which is great news, because in a system without any compromises, I don't want full-range at all. Since <150-200Hz everything is ruined by those pesky room modes anyway.
So I would much rather use a bunch of subwoofers (two is already a decent start). In that case I can even use woofers with an higher Sd. Which also results in less excursion. 8 inch can already be fitted in a relative small cabinet. (10-15 liters).
Or when it really has to be a full range system. (again, not recommended)
Mount a subwoofer(s) on the back or side of the cabinet.
That way, the whole Sd as well IMD argument is totally gone to begin with.
If we want to stay objective we have to explain the entire context of things.
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The audio mafia wants us to buy overpriced stuff that distort less than usual .
And it fits in small cabinets . But does it sound good? (better)
In physics - you always have to pay a price for something! (iron law)
Remember the Open-Baffle folks yelling hurray THAT is THE soulution!
FREE those heavenly sounds - dont put it in a tech jail 🙂
These money guys always try to rule the people and promise everything!
I dont trust them any longer ...
Mind Over Money !!!
And it fits in small cabinets . But does it sound good? (better)
In physics - you always have to pay a price for something! (iron law)
Remember the Open-Baffle folks yelling hurray THAT is THE soulution!
FREE those heavenly sounds - dont put it in a tech jail 🙂
These money guys always try to rule the people and promise everything!
I dont trust them any longer ...
Mind Over Money !!!
Well of course your 24" subwoofer that has 3mm x-max is going to out-thump the 8" Purifi with 10mm x-max between 20-100Hz.
The question is whether a 6.5" is better than the 8", or 10"? And can handle the full power rating, not just a fraction under the port/passive radiator tuning frequency, like many drivers with 4-5mm excursion do. And can go in smaller cabinet.
Do you place any value on that?
Because if you don't, by all means I could design you a speaker with a couple of 15-18" subwoofer per side, that does 40-100Hz with more authority than the 8" Purifi. But you also need a midrange. And about 200L of cabinet volume...
But for a 2-way speaker in a domestic setting, I've yet to see something smoother or cleaner.
And yes, that includes the $16K JBL 4367:
https://www.erinsaudiocorner.com/loudspeakers/jbl_4367/
For most of us, we can't design or build fast enough. That triple 8" Purifi 3-way doesn't build or design itself. :-(
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Hello All,
Here is what I can do with the noise of cooling fans.
This is a IMD plot at 50hZ and 425hZ, for the 6 1/2 inch 8R purify mid-bass driver in a 0.55 cubic foot sealed enclosure.
Not unlike the datasheet.
This is very nice for a mini 2.1-way that will sit on my bench top.
Very much worth the time and money.
By the way I do have a system with 15 inch woofers 10 inch mids and constant coverage CD's + waveguides in the same room. 10 Watts will have the police knocking at the door. I will post measurements another time and place.
Thanks DT
Thanks Dr. Lars for pushing the envelope.
Here is what I can do with the noise of cooling fans.
This is a IMD plot at 50hZ and 425hZ, for the 6 1/2 inch 8R purify mid-bass driver in a 0.55 cubic foot sealed enclosure.
Not unlike the datasheet.
This is very nice for a mini 2.1-way that will sit on my bench top.
Very much worth the time and money.
By the way I do have a system with 15 inch woofers 10 inch mids and constant coverage CD's + waveguides in the same room. 10 Watts will have the police knocking at the door. I will post measurements another time and place.
Thanks DT
Thanks Dr. Lars for pushing the envelope.
Who is talking about those (weird) extremes???
Of course I value a place on that, that's the whole point of even giving the whole example of a 8 inch.
(guess you missed that?)
Look at Voice Coil Testbench, or any other 3rd party place were they measure loudspeakers.
Any decent 8-10 subwoofer will do equally well, but often do an order of magnitude better than the best 6" woofers (incl Purifi) out there. The Wavecor SW223BD02 is an excellent example.
Not only that, but you will also get a lot more max SPL with that as well.
In the end there is only so much you can do with a smaller speaker.
See it a bit like the best performing 10W amplifier.
It might give you the best and most clean 10W available, but it's just not enough power in all home situates.
Speaking of which, I don't find the low end of Purifi that mind blowing.
There are other 6 inch woofers (Misco, Dayton to name a few) that do equally well or are so extremely close that you either won't notice the difference (keep in mind that for low frequency our hearing is extremely forgiving) or for less money you can get two, which lowers the distortion by 6dB (or half in percentage!)
I am talking as a subwoofer or a woofer in FAST system, NOT full-range.
There are also plenty of 6 inch woofers that will do equally well for just mid-range (> 100Hz)
Many decent well made 8 inch woofers will perform MUCH better for just mid-range.
Giving you even less IMD by definition.
So the only niche there is is the combination of low-end plus mid-range. (full range)
Which is a compromise on so many levels:
- Compromise in room modes
- You probably need a BR design to get the lower end, or will have very limited maxSPL in closed box (active EQ'ed)
- which leads to port non-linearities, which are an order of magnitude worse
- a port also leads to port resonances, which are also an order of magnitude worse (if not more!)
- trickier cabinet design with standing waves and what not, plus position of the port on the back
- a port also leads to a less predictable design
btw, offtopic, but you most certainly don't need 200 liters for 15-18 inch at all.
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That's not the iron law, but the law of conservation of misery.
Every solutions always has a bunch of compromises by default.
If we than also take money in the equation (some seem to have an abundance of that here?), than there are definitely more ways to peel an orange. (I don't like skinning cats, cats are cute 🙁 )
btw, I am NOT saying that these drivers are bad.
Because objectively speaking on raw performance they are one of the best out there.
(although I was disappointing by the performance of the 5 inch in the last VoiceCoil magazine)
But within context, I am saying that there are other ways as well.
The whole professional production (costs) side of things, is a totally different story.
I can write about that for hours and pages.
But most people don't seem to acknowledge that anyway, so I can't be bothered.
Forget about the cost equation, for a moment, in a decade these type of woofers will cost a fraction of the cost. Like the TacT Millenium amplifier in the late 1990s cost USD$10K. Within a decade later it was in Panasonic AVRs and now it's everywhere.
Scan-Speak had to make the SD motor before Usher and Dayton Audio or Wavecor followed decades later right?
I'm not going to debate with you b_force, if you don't want to use the aluminium Purifi woofers.
Have a good day.
Scan-Speak had to make the SD motor before Usher and Dayton Audio or Wavecor followed decades later right?
I'm not going to debate with you b_force, if you don't want to use the aluminium Purifi woofers.
Have a good day.
Where do you draw that conclusion from?
I am more than happy (or advice) to use Purifi drivers, if it suits the project.
I even said that they are excellent speakers?
I am happy to use any brand, price, size or whatever, it just totally depends on the projects, its constraints and needs.
Apologies perhaps I misunderstood you.
I must have mis-understood your comment about "So the way I read this, is that when one can prevent any kind of (significant) excursion, this is not even a problem to begin with."
I took this to mean- we can prevent excursion by using a much much bigger driver... because you started talking about multiple subwoofers.
Yeah I agree, I don't think the 6.5" or 8" Purifi is an ideal subwoofer. Or an ideal midrange.
It's a excellent mid-woofer in a 2 way. That's how I'm using it.
My main system has a pair of 12” per side in 120L cabinet.
It’s not unusual to put a pair of 15” or 18” woofers into 6” cu ft-7” cu ft. You don’t need to, it depends on the driver.
When Purifi releases the 12" I'm expecting it to be better than the Peerless XXLS-830845
When Purifi releases the 15" I'm expecting it to be better than the TC Sounds LMS-R 15"
When Purifi releases the 18" I'm expecting it to be better than LMS-Ultra 18 and Eminence NSW6021-6
Let’s compare like with like.
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It means we can prevent it by either using a bigger speaker OR not even letting the regular speaker doing the lower frequencies (aka having no or minimum amount of cone excursion).
Even better is a combination of those two -> using a 8 inch as midwoofer for example
(which practically isn't that much bigger than 6 inch).
The point is, this context is EXTREMELY important!
That was also the reason why I responded, because this story seems to be skipped over entirely.
There are multiple solutions for the same problem!
I like to compare anything, whatever suits the project.
In case of Purifi, budget is most definitely compromised, we can't objectivity deny that.
They are excellent speakers, very well engineered, but they are far from cheap.
There is absolutely nothing wrong with that, but that money can also be used for something else in the audio chain.
Probably room acoustics in many cases for example.
But even multiple mid-woofers is also even a solution.
For the same given SPL they will already provide 6dB less distortion (half in percentage).
You need 4 times less amplifier power!
There are quite some benefits for going for a MTM instead.
Or just using one of the woofers on the back etc etc (just giving some ideas)
Yes indeed - the driver is mass-controlled above resonance, so there may be some HD due to the air suspension at bass frequencies, but this won't cause IMD up the frequency range - so is largely unimportant.
@shrub0
Very hard to read Excel sheet.
Also how were the measurements being done, under what conditions, test setup etc etc?
At what frequency was the SPL determined? At IMD tones, at 1kHz, at Fs ?
Looking at the 90dB I also don't follow your conclusions.
Secondary, I miss a row with price per unit.
Because in some cases the results might look "better", that completely changes when I can lower the overall distortion (of any kind) by taking simply more speakers.
The same goes for total maxSPL, maxPower etc.
Referring back to my amplifier power analogy.
I am also missing quite some other decent speakers in here as well.
But again, this excel sheet is ALL about IMDB with a full-range design.
I already said that there are many ways of splitting those up as well in a low section (subwoofer) and mid section.
Because I already agreed that Purifi does very well in a mid-woofer design.
Ignoring all the other big disadvantages I mentioned before.
At those lower frequencies it's EXTREMELY important to see what the important harmonics are in the total IMD.
It's extremely difficult to hear the difference with especially 2nd order harmonics at these lower frequencies.
In some cases practically almost impossible, especially in music.
Last, this Excel sheet shows us something else as well, that some speakers that are 1/2-1/3 cheaper perform very similar to Purifi.
Very hard to read Excel sheet.
Also how were the measurements being done, under what conditions, test setup etc etc?
At what frequency was the SPL determined? At IMD tones, at 1kHz, at Fs ?
Looking at the 90dB I also don't follow your conclusions.
Secondary, I miss a row with price per unit.
Because in some cases the results might look "better", that completely changes when I can lower the overall distortion (of any kind) by taking simply more speakers.
The same goes for total maxSPL, maxPower etc.
Referring back to my amplifier power analogy.
I am also missing quite some other decent speakers in here as well.
But again, this excel sheet is ALL about IMDB with a full-range design.
I already said that there are many ways of splitting those up as well in a low section (subwoofer) and mid section.
Because I already agreed that Purifi does very well in a mid-woofer design.
Ignoring all the other big disadvantages I mentioned before.
At those lower frequencies it's EXTREMELY important to see what the important harmonics are in the total IMD.
It's extremely difficult to hear the difference with especially 2nd order harmonics at these lower frequencies.
In some cases practically almost impossible, especially in music.
Last, this Excel sheet shows us something else as well, that some speakers that are 1/2-1/3 cheaper perform very similar to Purifi.
Great spreadsheet. Saved.
I find it very easy to read, but then I’m a numbers man. I’m a glancer and a big picture person. But my spouse is a careful details person.
When we go out for dinner she will read each and everything at the restaurant menu before ordering.
OTOH. I like Steve Pinker’s Enlightenment Now but she’s thinks it’s too wordy and prefers Hans Rosling’s Factfulness which I feel is essentially the same book, but not as hard-data driven (and less detail)
This is a spreadsheet comparing a dozen or so 6.5” to 10” woofers and subwoofer, testing that’s internally valid, because it’s by the same person done in the same way under the same conditions.
The PTT6.5X-NFC; from 70dB to 85dB is a clear leader; even outcompeting 8” and 10” woofers including venerable XXLS and L26Roy that’s quite a feat. Moves down the chart ranking at higher SPL, but still in the top third of the pack: even outcompeting many 8”.
Honourable mention must go to the Dayton Audio RS225-8; which was a fantastic midwoofer, ground breaking Scan-Speak beater when it was released around 2005. It took a Revelator to de-throne it. Still competitive today as a very good midwoofer despite the price creep. A give-away in advanced economies like US when it was released at $35, but it was made in Taiwan, where one could buy an entire speaker for less.
Thanks again Mark, for taking the time to compile that spreadsheet, and share it with us.
I find it very easy to read, but then I’m a numbers man. I’m a glancer and a big picture person. But my spouse is a careful details person.
When we go out for dinner she will read each and everything at the restaurant menu before ordering.
OTOH. I like Steve Pinker’s Enlightenment Now but she’s thinks it’s too wordy and prefers Hans Rosling’s Factfulness which I feel is essentially the same book, but not as hard-data driven (and less detail)
This is a spreadsheet comparing a dozen or so 6.5” to 10” woofers and subwoofer, testing that’s internally valid, because it’s by the same person done in the same way under the same conditions.
The PTT6.5X-NFC; from 70dB to 85dB is a clear leader; even outcompeting 8” and 10” woofers including venerable XXLS and L26Roy that’s quite a feat. Moves down the chart ranking at higher SPL, but still in the top third of the pack: even outcompeting many 8”.
Honourable mention must go to the Dayton Audio RS225-8; which was a fantastic midwoofer, ground breaking Scan-Speak beater when it was released around 2005. It took a Revelator to de-throne it. Still competitive today as a very good midwoofer despite the price creep. A give-away in advanced economies like US when it was released at $35, but it was made in Taiwan, where one could buy an entire speaker for less.
Thanks again Mark, for taking the time to compile that spreadsheet, and share it with us.
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Overall I believe that you are correct. If you get into the fine details there is more to know. I do not think that the influence of suspension turns off like a switch at resonance nor does the mass become suddenly in charge at resonance either. Resonance is just a fuzzy division between the two.
Also the air volume of the sealed enclosure is also responsible for the increase of the resonance frequency and Q of the driver when it is installed in the sealed enclosure.
The resonance frequency of the bare driver is 34hZ and increases to 50hZ when it is installed in a 0.55 cubic foot sealed enclosure. If you look at the IMD plot of 2 tones, 50 hZ and 425hZ that I previously posted you see all the evidence of a IMD skirt on either side of the 425hZ tone, which is well above the 50 hZ resonance frequency.
See the attached plots:
Thanks DT
b_force,
I welcome criticism so please tell how I can make the spreadsheet more clear?
The spl is determined at each frequency so for the 40 and 96hz tones at 70hz, the 40 hz is at 70db and the 96hz is also at 70db. This is a good way to do it because some other measurements you can find online do not level match these tones so the a driver with low .QTS and high FS has an advantage.
As far as looking better, In the individual posts here you can look at the spectrograms 6-7" test: https://www.diyaudio.com/community/...ootout-purifi-anarchy-plus-maybe-more.371979/
the 8": https://www.diyaudio.com/community/...ation-distortion-testing.387690/#post-7060011
and 10": https://www.diyaudio.com/community/threads/10-woofer-subwoofer-imd-comparison.391184/
Yes, there are many speakers missing, which ones do you think would do well? I have also done a roundup of 10-12" drivers.
I agree with you that it can be advantageous to have a separate subwoofer to lower the total system IMD.
One thing to look at though is the lowest test 40 and 96hz would fall completely in the subwoofer passband even with an 80hz crossover 96hz will still be quite loud.
Yes some drivers have similar performance to the Purifi like the Epique, it presents low deep bass IMD but it's upper bass and midrange IMD performance is not as good as the Purifi. I'm always trying to find a diamond in the rough but so far I've found you get what you pay for in IMD performance. In general you do get a little more for your money with the drivers produced in Asia like with the Dayton RS225-8. Also some drivers showed more compression than others after level matching everything at 80db by the time I got to 90db the upper tone was down 2db or so. I accounted for this by increasing the level of the upper tone, but I imagine this would have some effect when listening to music.
At the end of the day speaker building is just a hobby for me and I originally started taking measurements for my own use, but being very careful to match measuring conditions each time for each driver I feel like I now have some valuable data to share and I hope to measure a few more drivers. I am happy to share what I've learned from measurements because when I started this hobby 25 years ago there was so little info out there just a couple of books I could check out from the library.
I welcome criticism so please tell how I can make the spreadsheet more clear?
The spl is determined at each frequency so for the 40 and 96hz tones at 70hz, the 40 hz is at 70db and the 96hz is also at 70db. This is a good way to do it because some other measurements you can find online do not level match these tones so the a driver with low .QTS and high FS has an advantage.
As far as looking better, In the individual posts here you can look at the spectrograms 6-7" test: https://www.diyaudio.com/community/...ootout-purifi-anarchy-plus-maybe-more.371979/
the 8": https://www.diyaudio.com/community/...ation-distortion-testing.387690/#post-7060011
and 10": https://www.diyaudio.com/community/threads/10-woofer-subwoofer-imd-comparison.391184/
Yes, there are many speakers missing, which ones do you think would do well? I have also done a roundup of 10-12" drivers.
I agree with you that it can be advantageous to have a separate subwoofer to lower the total system IMD.
One thing to look at though is the lowest test 40 and 96hz would fall completely in the subwoofer passband even with an 80hz crossover 96hz will still be quite loud.
Yes some drivers have similar performance to the Purifi like the Epique, it presents low deep bass IMD but it's upper bass and midrange IMD performance is not as good as the Purifi. I'm always trying to find a diamond in the rough but so far I've found you get what you pay for in IMD performance. In general you do get a little more for your money with the drivers produced in Asia like with the Dayton RS225-8. Also some drivers showed more compression than others after level matching everything at 80db by the time I got to 90db the upper tone was down 2db or so. I accounted for this by increasing the level of the upper tone, but I imagine this would have some effect when listening to music.
At the end of the day speaker building is just a hobby for me and I originally started taking measurements for my own use, but being very careful to match measuring conditions each time for each driver I feel like I now have some valuable data to share and I hope to measure a few more drivers. I am happy to share what I've learned from measurements because when I started this hobby 25 years ago there was so little info out there just a couple of books I could check out from the library.
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