Changster beat me to the punch linking Erin’s latest PURIFI driver review in this thread. He uses the Klippel Near Field Scanner for these reviews so they are a subjectivists and designers dream come true. The text version of Erin’s results can be found on his site https://www.erinsaudiocorner.com/.
I find the second half of Erin’s review interesting. After reporting the state of the art results we are used to from PURIFI he discusses possible use cases. I reacted “WHAT??!!” when he says PURIFI’s 6.5” and 8” woofers should in his opinion be high pass filtered. To me the interesting part here is this illustrates how we view our tools is so dependent on the job we intend to task them with. As a hard core 2-channel high end Hi-Fi audiophile/designer I view the various PTT6.5 and PTT8.0 woofers as the ideal SOTA solution for ultra-high performance compact form factor 2-way speakers. In contrast Erin comes at this from car audio and home theater worlds where use of subwoofer(s) is a given. And where the design brief typically includes requirement for 20 Hz bass at +100 dB (please pass me the earplugs before hitting ‘play’).
I find the second half of Erin’s review interesting. After reporting the state of the art results we are used to from PURIFI he discusses possible use cases. I reacted “WHAT??!!” when he says PURIFI’s 6.5” and 8” woofers should in his opinion be high pass filtered. To me the interesting part here is this illustrates how we view our tools is so dependent on the job we intend to task them with. As a hard core 2-channel high end Hi-Fi audiophile/designer I view the various PTT6.5 and PTT8.0 woofers as the ideal SOTA solution for ultra-high performance compact form factor 2-way speakers. In contrast Erin comes at this from car audio and home theater worlds where use of subwoofer(s) is a given. And where the design brief typically includes requirement for 20 Hz bass at +100 dB (please pass me the earplugs before hitting ‘play’).
I also disliked the car audio related HPF suggestion. But I guess that the car audio scene has a much bigger audience in the US?
Anyway I was interested in the 6.5" M as a midrange and the measured sensitivity was a bit disappointing to me. Did Erin get the 8 Ohm version? I'm a mixed Audio/HT guy but I prefer quality over dB's though.
So @lrisbo: What midrange would you suggest for such a mixed HT/Stereo set? A single 4 Ohm 6.5" M in a TMWW? Or a dual 8 Ohm 6.5"M in an MTMWW? I guess that a single PTT6.5M needs to be crossed higher to be able to cope with HT dynamics (THX Dominus?)
Right. You guys have to understand that my "target audience" is VERY, VERY diverse. There are probably more car audio people looking at that 8-inch midbass than there are home audio guys. Whereas I imagine there is probably an even split on the 6.5" woofers.
I think "disliking my car audio related HPF suggestion" is poor wording. My suggestion there is dead on for the car-fi folks who use my reviews. You can say that my car-fi suggestion doesn't apply to home audio. That's more appropriate. At least, most of the time.
Home-fi DIY'rs are going to use the speakers in different applications and they will use the appropriate HPF (or none at all) in their rooms. Notably, home designs will use a proper enclosure. Nearly 100% of car audio folks using these will put them in leaky doors and there will be no compliance from an enclosure to keep the suspension in check. I assume (hope) that the DIY guys building with these understand the data enough and don't need me to explain how best to use these drivers. They'll take the data to determine if the driver fits their needs and go on about their way.
Car audio is different. I mentioned the lack of enclosure above. Car-fi guys typically think that crossing a woofer over as low as possible is the best way to go and I think that's utter nonsense. Not only do you risk damaging the speaker but the way the car acoustics play out, it makes little sense to not HP door speakers >70Hz and let the subwoofer fill in the cabin null caused by the nearside woofer.
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Thanks Erin. I watched your YT review and overlooked the 08 in the measurements graph. My bad!
Please forgive my negative bias against DIY car audio. I keep imagining all these brave women enduring extreme subwoofer SPL with their hair flopping around but I guess this is only a part of the DIY scene? Car audiophiles will want the best possible SQ and then such a refined Purifi driver will be completely justified.
I'm still debating what Purifi midrange to choose for my personal in-wall HT. My actual speakers are Focal Scala Utopia for LR and Sopra Center but I dislike their audiophile footprint.
Funny enough, the folks who truly "get" car audio are some of the ones who understand audio much more completely than home audio folks, IME. That's not a knock against anyone/others. That's just the experience I've had. The acoustics around making a car audio system sound great make you have to learn and understand the topic much more than an average consumer. Take baffle step, for example. We know it in home audio. It's easy to account for. But when you put a speaker in a dash corner and everything nearby because the baffle... that requires a deeper level of understanding and applicability.
The DIY scene is much more than just the SPL crowd. I started as a DIY'r in car audio. My first set of drivers came from Madisound; Seas L18 and Vifa TG9 mids. That was about 15 years ago. Been a wild ride ever since.
I can't believe someone just said they disliked the car audio discussion in the video. It's such a snobbish thing to say. T/S parameters like QTS applies to audio everywhere, including the home. For example, what if you are going to use these Purifi drivers in an open baffle configuration and not a sealed/ported box?
Like Erin said, I also find that most people who really understand how to get a car to sound good are in general more knowledgeable than most of the home HiFi people. To put it simply, car audio people know how to get the most out of their environment by controlling every speaker actively and independently.
Most home HiFi people are still using passive crossovers. That is such a thing of the past IMO. I meet a lot of home HiFi "signal purists" as well that think "oh my god don't touch my signal or else you'll ruin the sound!" while letting their signal pass through passive components that most have tolerances of +/- 20% for average quality ones and +/- 10% for higher quality ones. It's like somehow it's ok to send the signal through these passive components but yet it's "impure" to have the signal pass through a very precise DSP. BTW it's less so on here (after it's the DIYAudio forum, with a much more open minded crowd) versus the people who buy the crazy expensive stuff displayed at the Munich Hifi Show.
Car audio people are also good at implementing crossover points and slopes by first looking at the acoustical response of every single drive unit measured from the listening position, to be able to maximize the overall acoustical response. Home Hifi people set their crossovers and they can't change them easily (passive crossovers!), so they resort to moving their speakers everywhere and start treating the room with ugly diffusers and absorption. I like Siegfried Linkwitz's approach where he says (to the effect of) if you start looking around the room then something's wrong with your speaker implementation.
Anyways, excuse the rant. I'm going to have a lot of fun with that Purifi 8" in the car. I have holes cut under the seats of my BMW for an IB midbass application currently, and it'll be fun to compare with the current driver. Also one day maybe I implement my current Linkwitz 521.4 using Purifi drivers as well.
Like Erin said, I also find that most people who really understand how to get a car to sound good are in general more knowledgeable than most of the home HiFi people. To put it simply, car audio people know how to get the most out of their environment by controlling every speaker actively and independently.
Most home HiFi people are still using passive crossovers. That is such a thing of the past IMO. I meet a lot of home HiFi "signal purists" as well that think "oh my god don't touch my signal or else you'll ruin the sound!" while letting their signal pass through passive components that most have tolerances of +/- 20% for average quality ones and +/- 10% for higher quality ones. It's like somehow it's ok to send the signal through these passive components but yet it's "impure" to have the signal pass through a very precise DSP. BTW it's less so on here (after it's the DIYAudio forum, with a much more open minded crowd) versus the people who buy the crazy expensive stuff displayed at the Munich Hifi Show.
Car audio people are also good at implementing crossover points and slopes by first looking at the acoustical response of every single drive unit measured from the listening position, to be able to maximize the overall acoustical response. Home Hifi people set their crossovers and they can't change them easily (passive crossovers!), so they resort to moving their speakers everywhere and start treating the room with ugly diffusers and absorption. I like Siegfried Linkwitz's approach where he says (to the effect of) if you start looking around the room then something's wrong with your speaker implementation.
Anyways, excuse the rant. I'm going to have a lot of fun with that Purifi 8" in the car. I have holes cut under the seats of my BMW for an IB midbass application currently, and it'll be fun to compare with the current driver. Also one day maybe I implement my current Linkwitz 521.4 using Purifi drivers as well.
The car audio market is a BIG market where enthusiasts are willing to pay top dollar, for the SQ or SPL performance. In fact, little birdy told me Samsung bought Harman to leverage their existing portfolio in the expanding car audio market, not their deep and historied expertise in the professional and legacy audio stuff. Yeah JBL Everest speaker is great in the few who have the room for it, but let's face it in the days of thin TV, it's a tiny market.
Watch this space- the future car that your sons and daughters drive will be EV, and silent , thus sound systems are going to be whole lot better in the next 10 years. Don't forget that an OEM now has a predictable interior space/cabin, which makes designing a sound system a lot easier and has greater potential for excellent sound. As a home audio designer my speaker might be fantastic for a "standard room", but what on earth is that?
Do I tune it for my room?
Erin's room?
A single PTT 6.5M-04 should be able to read 105dB/1m at listening position given the 93dB/2.83V depending on your high pass filter and slope. What holds you back is your woofers- the THX or Dolby Atmos spec they will need to an extra 10dB down to 32Hz at the listening position. So in my 3-way design I use twin twelves per speaker, to hit 112dB anechoic @1m. Dynamic range for days...
Watch this space- the future car that your sons and daughters drive will be EV, and silent , thus sound systems are going to be whole lot better in the next 10 years. Don't forget that an OEM now has a predictable interior space/cabin, which makes designing a sound system a lot easier and has greater potential for excellent sound. As a home audio designer my speaker might be fantastic for a "standard room", but what on earth is that?
Do I tune it for my room?
Erin's room?
A single PTT 6.5M-04 should be able to read 105dB/1m at listening position given the 93dB/2.83V depending on your high pass filter and slope. What holds you back is your woofers- the THX or Dolby Atmos spec they will need to an extra 10dB down to 32Hz at the listening position. So in my 3-way design I use twin twelves per speaker, to hit 112dB anechoic @1m. Dynamic range for days...
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My apologies. I should have written "didn't get" as I thought that most new cars don't have din slot anymore like in the 70's, 80's and 90's but offer a fully integrated multimedia system built deep into the dashboard. Back in the 90's I also had a DIY dual 12" sub @30Hz in the boot and it sounded great. But when I married my wife demanded full loading capacity so this sub had to go. The next car already had such an intgrated audio system so I didn't even bother. The actual car is the first one that made me think about an upgrade as it's Burmester system sounds a bit thin on bass.
Thanks for PTT 6.5M-04 recommendation for my LCR project. I'm planning to use it from 200Hz to 1500Hz. Above 1500Hz I'm thinking about the Bliesma T34A or T34B and under 200Hz I'll use 2x 15" PHL 6201 (already bought) in a sealed enclosure with a QTC=0.7The car audio market is a BIG market where enthusiasts are willing to pay top dollar, for the SQ or SPL performance. In fact, little birdy told me Samsung bought Harman to leverage their existing portfolio in the expanding car audio market, not their deep and historied expertise in the professional and legacy audio stuff. Yeah JBL Everest speaker is great in the few who have the room for it, but let's face it in the days of thin TV, it's a tiny market.
Watch this space- the future car that your sons and daughters drive will be EV, and silent , thus sound systems are going to be whole lot better in the next 10 years. Don't forget that an OEM now has a predictable interior space/cabin, which makes designing a sound system a lot easier and has greater potential for excellent sound. As a home audio designer my speaker might be fantastic for a "standard room", but what on earth is that?
Do I tune it for my room?
Erin's room?
A single PTT 6.5M-04 should be able to read 105dB/1m at listening position given the 93dB/2.83V depending on your high pass filter and slope. What holds you back is your woofers- the THX or Dolby Atmos spec they will need to an extra 10dB down to 32Hz at the listening position. So in my 3-way design I use twin twelves per speaker, to hit 112dB anechoic @1m. Dynamic range for days...
I'll probably use the Hypex FA253 or FA503 with active filtering. One disadvantage of active filtering though is that I'm the only one in my family with the knowledge how to repair/reprogram these units when things go wrong. I still remember the USB issues that I had with the PSC2.700...
Critical question
Finally received the long waited 2x Purifi passive radiators to pair with a PTT 6.5. I have a 15L enclosure as per the Directiva r1 design from ASR including the DXT tweeter. I haven't figured out how to mount the radiators - opposite to the woofer in the back panel or opposite to each other in the side panels ? The listening room is long and high, speakers will sit in a corner, about 50 cm from the walls. Driving the speakers through active XO. Didn't find a simulation tool that I can model the radiators in the enclosure, will appreciate opinions.
Finally received the long waited 2x Purifi passive radiators to pair with a PTT 6.5. I have a 15L enclosure as per the Directiva r1 design from ASR including the DXT tweeter. I haven't figured out how to mount the radiators - opposite to the woofer in the back panel or opposite to each other in the side panels ? The listening room is long and high, speakers will sit in a corner, about 50 cm from the walls. Driving the speakers through active XO. Didn't find a simulation tool that I can model the radiators in the enclosure, will appreciate opinions.
PRs opposite of each other eg. on the sides will provide cancellation of Newtonian forces. If it’s the PTT6.5X then you may go down to say 10-12L for the flattest bass response. you can model it in eg VituixCad. We have promised an app note for a long time so thanks for the reminder
Julbo has the good fortune to be on the cusp of upping his PUFIFI game. You are really going to enjoy adding the PTT6.5PRs. After a couple years into this here are some suggestions to consider.
I have built PTT6.5W + 2ea PR systems with (in this order) 16, 25, 14, and 12 liters of volume per enclosure. Like you I started with the 15 to 16 liters the PURIFI application note for vented designs yields which also sims well enough in CAD with PTT6.5PRs in place of vent. Alerted by a previous post in this diyAudio thread by Lars/Irisbo to look into smaller volumes I used blocks of wood placed in the enclosure to convert my Fi16 design from 16 to 14 liters. My listening buddies concurred with me this was a step in the right direction with ‘snappier’ more lively bass. So I designed and built a prototype pair of Fi12 using 12 liter enclosures. The Fi12 is a stop designing and building and just enjoy the music solution.
Lars while authoring that overdue application note I would appreciate it if you would discuss the trade-offs of a range of volumes. From the viewpoint of how simulations in CAD translate into the listening experience. In my simulations using PTT6.5W + 2 ea. PTT6.5PRs I find the 12 liter solution gives max-flat response while the larger 14 or 16 liter alignments bass droops a dB or two with a slower rolloff and more area under the curve 20-40 Hz. Sometimes referred to as EBS, extended bass shelf alignments. Thus its tempting to say for the larger boxes let room gain and/or baffle step correction make up the 40 to 500 Hz droop and go for the extra deep bass. Many hours of CNC and sawdust later its 12 liters for me. Is the result in the listening room superior for 12l due to something like the max-flat alignment having better group delay &/or critically damped transient response?
Now back to julbo’s question “how to mount the radiators - opposite to the woofer in the back panel or opposite to each other in the side panels”. In my Fi16/14 and Fi12 designs I have done both. In my experience the 50 cm distance to back wall is not the deciding factor. I use similar distances with rear PRs and excellent results. Certainly the cancellation of Newtonian forces cited by Lar’s is an advantage for side mount. I find the action/reaction Newtonian forces of his hyper-woofer to be a larger issue, but I’ll take help with the PRs’. The aspect I suggest looking at in the trade-off’s matrix of a design is panel space. Do a scaled sketch or CAD and look at how much rear panel space a pair of PTT6.5PRs occupy. In my Fi16 the width x height is 8.5 x 15 inches or 21.6 x 38 cm. From the front that is a nice typical proportion with room for PTT6.5W and tweeter. On the back a pair of PTT6.5PRs fill the area. I have just enough space to fit a Speakon connector in a lower corner, no area for a binding post plate. For a proper set of audiophile style binding posts I would need to mount them one in each corner. Next if we start lowering the enclosure volume 16 to 12 or 10 liters with baffle/back panel minimum size to fit two PRs at ~22 x 38 cm the depth gets unusually small. Clever industrial design can work with that but given the initial reaction to out of the ordinary proportions is ‘that’s odd’ something to consider. At this fork in the design road the simple answer is small stiff box with PRs on opposite sides. The other route I see is a properly proportioned larger box with PRs on the rear and excess internal volume burned off by extensive internal martix style bracing.
I have built PTT6.5W + 2ea PR systems with (in this order) 16, 25, 14, and 12 liters of volume per enclosure. Like you I started with the 15 to 16 liters the PURIFI application note for vented designs yields which also sims well enough in CAD with PTT6.5PRs in place of vent. Alerted by a previous post in this diyAudio thread by Lars/Irisbo to look into smaller volumes I used blocks of wood placed in the enclosure to convert my Fi16 design from 16 to 14 liters. My listening buddies concurred with me this was a step in the right direction with ‘snappier’ more lively bass. So I designed and built a prototype pair of Fi12 using 12 liter enclosures. The Fi12 is a stop designing and building and just enjoy the music solution.
Lars while authoring that overdue application note I would appreciate it if you would discuss the trade-offs of a range of volumes. From the viewpoint of how simulations in CAD translate into the listening experience. In my simulations using PTT6.5W + 2 ea. PTT6.5PRs I find the 12 liter solution gives max-flat response while the larger 14 or 16 liter alignments bass droops a dB or two with a slower rolloff and more area under the curve 20-40 Hz. Sometimes referred to as EBS, extended bass shelf alignments. Thus its tempting to say for the larger boxes let room gain and/or baffle step correction make up the 40 to 500 Hz droop and go for the extra deep bass. Many hours of CNC and sawdust later its 12 liters for me. Is the result in the listening room superior for 12l due to something like the max-flat alignment having better group delay &/or critically damped transient response?
Now back to julbo’s question “how to mount the radiators - opposite to the woofer in the back panel or opposite to each other in the side panels”. In my Fi16/14 and Fi12 designs I have done both. In my experience the 50 cm distance to back wall is not the deciding factor. I use similar distances with rear PRs and excellent results. Certainly the cancellation of Newtonian forces cited by Lar’s is an advantage for side mount. I find the action/reaction Newtonian forces of his hyper-woofer to be a larger issue, but I’ll take help with the PRs’. The aspect I suggest looking at in the trade-off’s matrix of a design is panel space. Do a scaled sketch or CAD and look at how much rear panel space a pair of PTT6.5PRs occupy. In my Fi16 the width x height is 8.5 x 15 inches or 21.6 x 38 cm. From the front that is a nice typical proportion with room for PTT6.5W and tweeter. On the back a pair of PTT6.5PRs fill the area. I have just enough space to fit a Speakon connector in a lower corner, no area for a binding post plate. For a proper set of audiophile style binding posts I would need to mount them one in each corner. Next if we start lowering the enclosure volume 16 to 12 or 10 liters with baffle/back panel minimum size to fit two PRs at ~22 x 38 cm the depth gets unusually small. Clever industrial design can work with that but given the initial reaction to out of the ordinary proportions is ‘that’s odd’ something to consider. At this fork in the design road the simple answer is small stiff box with PRs on opposite sides. The other route I see is a properly proportioned larger box with PRs on the rear and excess internal volume burned off by extensive internal martix style bracing.
Thanks Lars & Norman - yes it is a PTT6.5X04-NFA01. This is going to be my second enclosure, the first was a 15L Denovo cabinet with a SB 15"x8" oval passive radiator rear mounted. I can go with a CAD adventure and order CNC'ed parts, I'm more of an engineer than a carpenter and the sawdust doesn't bode well with the WAF.
I've done the Vituix exercise and was convinced that 2x Purifi PRs will perform better than the SB radiator. After completing the build I've quickly found out that the SB PR was simply overwhelmed by the Purifi to the point that a HPF would be needed in the woofer's DSP pipeline in order to get away from the radiator's Fs. I think I understand that the perceived loss of transient response might be mitigated with a smaller enclosure, I was about to accept this as the main downside for going PR and not going ported.
A smaller enclosure is very appealing, worth the trial
PRs on the side panel can free up valuable space for an active (DIY) plate amp/DSP combo.
The question bothering me on PR positioning, apart of the Newtonian forces and connectivity, is there a meaningful difference in the acoustic rendering and room interaction? From Norman's reply it seems little difference
Also, side firing PRs seem to experience a different acoustic path in the enclosure rather than a direct wave. I reckon that the frequencies relevant for a PR are low enough that "time of flight" differences to the main driver are negligible.
Norman: "Many hours of CNC and sawdust later its 12 liters for me. Is the result in the listening room superior for 12l due to something like the max-flat alignment having better group delay &/or critically damped transient response?"
And the answer is .. yes ? Would you say that a sub is recommended here ?
I've done the Vituix exercise and was convinced that 2x Purifi PRs will perform better than the SB radiator. After completing the build I've quickly found out that the SB PR was simply overwhelmed by the Purifi to the point that a HPF would be needed in the woofer's DSP pipeline in order to get away from the radiator's Fs. I think I understand that the perceived loss of transient response might be mitigated with a smaller enclosure, I was about to accept this as the main downside for going PR and not going ported.
A smaller enclosure is very appealing, worth the trial
PRs on the side panel can free up valuable space for an active (DIY) plate amp/DSP combo.
The question bothering me on PR positioning, apart of the Newtonian forces and connectivity, is there a meaningful difference in the acoustic rendering and room interaction? From Norman's reply it seems little difference
Also, side firing PRs seem to experience a different acoustic path in the enclosure rather than a direct wave. I reckon that the frequencies relevant for a PR are low enough that "time of flight" differences to the main driver are negligible.
Norman: "Many hours of CNC and sawdust later its 12 liters for me. Is the result in the listening room superior for 12l due to something like the max-flat alignment having better group delay &/or critically damped transient response?"
And the answer is .. yes ? Would you say that a sub is recommended here ?
You guys are obsessing over the bass alignment. The right bass depends on your speaker’s interaction with your room, your bass level preference and the musical tastes. There’s no perfect. Only perfect for you.
I just got back from Ministry Of Sound Classical concert last night. MOS is a big brand these days and you can say what you want about their DJ roster, commercialisation of dance music, but the original club in London was famous because of its state of the art sound system. unlike most clubs that was about places to see, who to rub shoulders with; MOS was for the punters, the state of the sound system was first and foremost the priority; the visual effects second and everything else a distant third.
As a speaker nerd I measured what I got from my boring VIP seated position that my spouse wanted to stay at. The line arrays gave 100+ dynamic peaks at 50m away.
i come back to my living room the next day and my quad 12 woofers aren’t enough…
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That's almost an oxymoron...
I actually hunt out concerts with as little sound re-inforcement as possible. Hard to find these days in larger venues. But clearly a good audience for this stuff, which is great.
PRs opposite of each other eg. on the sides will provide cancellation of Newtonian forces. If it’s the PTT6.5X then you may go down to say 10-12L for the flattest bass response. you can model it in eg VituixCad. We have promised an app note for a long time so thanks for the reminder
Perhaps a stupid question but still learning: I get the cancellation of Newtonian forces for the PRs if they're opposite to each other. But with PRs in rear, won't there be some cancellation PRs vs woofer?
Not a stupid question at all. Recall in bass systems using vents or PRs the woofer(s) provide most of the output, until the tuning frequency. At that frequency where the box is tuned the ports or PRs take over and provide the sonic output. At the exact tuning frequency the pressure of the air in resonance holds the woofer almost still while the PRs (or air in vent tube) experience maximum excursion. The graph below is the Stereophile measurements of the GoldenEar BRX also a woofer + PRs system. The blue trace is the woofer output, red trace the PRs outputs. Notice just below 50 Hz woofer output drops while PR outputs peak. Black trace is where they sum to yield the combined system output.
Thus with woofer on front and PRs rear configuration they are not acting in anti-phase therefore minimal cancellation of Newtonian forces.