Hi Lars,
Much appreciate your detailed and technical replies.
With the latest 4'' NAC I wonder.. and I have to ask this question: is a wide band possible with Purifi technology? It would be wonderful if a low IMD driver can work in full range even with a bit of help of EQ and sub-bass support.
Cheers!
That would be very nice indeed. A friend of me has a 2.1 system with Eton Arcosia 4 inch drivers playing from 100Hz up to 20kHz, EQ with minidsp DSP and Dirac Live it sounds awesome in the sweetspot. Perfect for nearfield listening.
I guess Purifi has to add some magnesium to the cone to get similar FR performance.
In terms of specs maybe not, I am pretty sure Purifi could do better and therefore I am also interested in such a driver from them.
I would rather pick a different fullrange. I'd only use this with a proper tweeter and crossover. I'm not an adherent to the school of thought that likes to pick drivers with terrible response and then is so enamored with the fact they could tweak them to listenable.
Yes, sometimes it is not the right thing to do.. however sometimes it is. Properly considering which is which, due to the fact that some issues are completely fixable a person may be putting themselves at a disadvantage in ruling out drivers due to them not looking flat.
I'm really interested in the new 4", because crossing it to a Bliesma T34A would apparently allow a very nice directivity match (i.e. neither is beaming significantly around 1200-2000hz, looks like a lot of wiggle room) and they could both cross in low-distortion ranges. I was planning on doing a waveguide, but it seems like maybe not even necessary with the 4" vs. a 6.5".
I think I would cross it to a 10" CSS SDX10 around 200hz, which would give pretty low distortion across the board.
It just seems perhaps a little odd to use so little of the usable bandwidth of the purifi, and to rely on a 4" as a single midwoofer? But the xmax is such that peak SPL at 200hz would still be high enough for me. So, I'm not seeing an obvious reason not to do this. Am I nuts, or is this really just a remarkable 4"?
I think I would cross it to a 10" CSS SDX10 around 200hz, which would give pretty low distortion across the board.
It just seems perhaps a little odd to use so little of the usable bandwidth of the purifi, and to rely on a 4" as a single midwoofer? But the xmax is such that peak SPL at 200hz would still be high enough for me. So, I'm not seeing an obvious reason not to do this. Am I nuts, or is this really just a remarkable 4"?
@ErnieM thanks for the response. I used this to get an idea of SPL based on xmax - would this give an accurate number? http://www.baudline.com/erik/bass/xmaxer.html - it says ~113 at 200hz for 8.5mm x 4" cone. I am not sure what this translates to at 1m but it's probably enough either way, I've not got a large room.
I guess I could always double up on the 4"ers...
I guess I could always double up on the 4"ers...
When using that calculator gives with PTT4.0X’s effective piston diameter of
8.5cm = 3.34”
Solving for SPL max @200Hz and 8.5mm excursion gives 111dB @1m
Here’s a good graph you may have missed:
Reference:
https://www.diyaudio.com/community/...ifi-woofer-speaker-builds.352063/post-7123950
You may notice the PTT4.0X here has a max SPL of 116dB.
Cross referencing with my own values, I believe that @lrisbo uses a slightly different method of calculation- the mechanical excursion (15mm) for this graph.
They are slightly higher but both methods get you into the ballpark figures.
I prefer to use VituicCAD2 to simulate the max SPL - using both linear excursion + thermal power handling limitations; and plots an amplitude vs frequency graph based on the lower of the lowest of the 2, but then conduct real world SPL testing outdoors, when weather permits.
8.5cm = 3.34”
Solving for SPL max @200Hz and 8.5mm excursion gives 111dB @1m
Here’s a good graph you may have missed:
Reference:
https://www.diyaudio.com/community/...ifi-woofer-speaker-builds.352063/post-7123950
You may notice the PTT4.0X here has a max SPL of 116dB.
Cross referencing with my own values, I believe that @lrisbo uses a slightly different method of calculation- the mechanical excursion (15mm) for this graph.
They are slightly higher but both methods get you into the ballpark figures.
I prefer to use VituicCAD2 to simulate the max SPL - using both linear excursion + thermal power handling limitations; and plots an amplitude vs frequency graph based on the lower of the lowest of the 2, but then conduct real world SPL testing outdoors, when weather permits.
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Thanks @tktran303 - this is good confirmation and it's probably loud enough. With stereo and in-room I am sure I will rarely if ever want to touch the limits of this driver. FWIW I have read subjective reviews of PTT drivers where people hit xmech inadvertently because the driver sounds so clean even up to that limit, so I guess I'm willing to accept xmech as a genuinely relevant number here.
Now, whether I want to have a higher ceiling for the sheer purpose of "maximum overkill" is another question, one I will think about for a little while, since the driver isn't even up for purchase yet...
Now, whether I want to have a higher ceiling for the sheer purpose of "maximum overkill" is another question, one I will think about for a little while, since the driver isn't even up for purchase yet...
Whilst you’re mulling over your design; another handy online calculator for complete speaker design is:
http://www.hometheaterengineering.com/splcalculator.html
As you will see; hitting reference (concert/film) levels of 85dB with dynamic peaks of 20dB (ie. 105dB unclipped transients ) at the listening position is no easy feat.
http://www.hometheaterengineering.com/splcalculator.html
As you will see; hitting reference (concert/film) levels of 85dB with dynamic peaks of 20dB (ie. 105dB unclipped transients ) at the listening position is no easy feat.
This calculator, I am quite familiar with... I used it to justify buying my NC500 monoblocks.
My plan is to use some Hypex FA-503s, but even so I guess the amps will be the limiting factor, or at least it will be close. Too bad these are so low sensitivity, but the other factors are so appealing... wild to think you could pump 500w into some 4"ers and still not hit xmech...??
Yes you need appropriate sensitivity matched with appropriate voltage (power) and listening distance (room size)
In this post I described a 92dB / 2.83V system-
https://www.diyaudio.com/community/...pete-with-totl-commercial.392335/post-7178271
Driven by DSP and active Hypex NC400 x built since introduction in 2012.
92dB + 23dB gain (amplifier) - 10dB (3 m listening position) = 110dB unclipped peaks.
Stunning dynamic range.
It is from this basis that my new family of speakers are designed:
https://www.diyaudio.com/community/...4a-measurements-purifi-and-scan-speak.390316/
In this post I described a 92dB / 2.83V system-
https://www.diyaudio.com/community/...pete-with-totl-commercial.392335/post-7178271
Driven by DSP and active Hypex NC400 x built since introduction in 2012.
92dB + 23dB gain (amplifier) - 10dB (3 m listening position) = 110dB unclipped peaks.
Stunning dynamic range.
It is from this basis that my new family of speakers are designed:
https://www.diyaudio.com/community/...4a-measurements-purifi-and-scan-speak.390316/
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Very cool, I was looking at your B&W build the other day. This is great inspiration for what I plan to do. I'm aiming for relatively similar performance, but with the goal of more bass extension. I don't have any space or proper tools for woodworking, plus I have an incurable DIY bug, so I plan to design and 3D print my own enclosures. I have almost no experience with electronics (read: passive crossovers), but 10y experience 3D printing and much more than that with DSP, so I am going to lean heavily in those directions. Currently I'm thinking of having a layer of sand, then a layer of concrete, inside the plastic shell, consistent with the "maximum overkill" concept. Spheroid baffle for the mid and tweeter, transitioning to a lanceloate (this is apparently the technical name for a teardrop shape) shape for the woofer and rear/amp section of the cabinet. With 3D printing you can make more or less arbitrary shapes, so why not go a little nuts?
Before this I will be using the printer to make some nice simple 1-way FR desktop cheapies, to make sure the process works, then start seriously planning / simulating the Purifi build.
In 2023 I plan to to update the large twin woofer 3-way; once appropriate sized Purifi drivers (tweeter and 12” woofers) are released.
PTT6.5M-04 already on standby to replace the FST.
A lanceloate shaped cabinet is a great for diffraction. In fact I believe a snowman shaped speakers are the best for diffraction, but a
hard to market/sell.
What seems to be most popular in past decades is the tall slim passive speaker with paper cones; although I like well-behaved metal cones very much and there is no replacement for displacement or DSP.
PTT6.5M-04 already on standby to replace the FST.
A lanceloate shaped cabinet is a great for diffraction. In fact I believe a snowman shaped speakers are the best for diffraction, but a
hard to market/sell.
What seems to be most popular in past decades is the tall slim passive speaker with paper cones; although I like well-behaved metal cones very much and there is no replacement for displacement or DSP.
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For me, Purifi really makes most sense in the midrange. Using the dedicated midrange, seems like a proper upgrade.
Anyone built anything with this ??
https://hificompass.com/en/reviews/purifi-ptt65m08-nfa-01a-65-true-midrange
My thoughts are - cross it between 2 x 8 or 10" and SB26ADC or T25B-6 in a 6" WG from Augerpro. Crossed around 3-400Hz and 1700-2000Hz.
Anyone built anything with this ??
https://hificompass.com/en/reviews/purifi-ptt65m08-nfa-01a-65-true-midrange
My thoughts are - cross it between 2 x 8 or 10" and SB26ADC or T25B-6 in a 6" WG from Augerpro. Crossed around 3-400Hz and 1700-2000Hz.