I have been trying to find out what Purifi drivers have the lowest distortion. There are few ressources on the web that have tested sufficient models under similar conditions that allow pairwise comparison. Hificompass has a few, but not so many pairs. There I learned that the M (midrange) versions do not seem to have lower distortion at 90 dB/m which is what I would would have expected, and that aluminum cones have significantly lower distortion than their paper brethren. This is not only true for HD2, which I would have expected, but also for HD3 which I find surprising.
I then turned to the Purifi data sheets which I hope were measured under standardized conditions. These are always for 2.83 V. So in order to compare similar SPL, it may be necessary to compare, e.g., the 8 Ohm version of a midrange to a the 4 Ohm version of an extended throw version. I will be posting overlays of such data to prove my point.
Making these overlays is cumbersome, so bear with me 🙂
I then turned to the Purifi data sheets which I hope were measured under standardized conditions. These are always for 2.83 V. So in order to compare similar SPL, it may be necessary to compare, e.g., the 8 Ohm version of a midrange to a the 4 Ohm version of an extended throw version. I will be posting overlays of such data to prove my point.
Making these overlays is cumbersome, so bear with me 🙂
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Thanks Eric,
I’d been glancing at the measurements in the data sheets measured at average 94dB@1m, and gleaned that the metal X seemed to play with the lowest distortion.
I concluded that W and M ranges were made to satisfy people using passive crossovers (wanting higher sensitivity). Metal is more “pistonic” but as one zooms in close enough, if the primary breakup changes in the off axis angles, that chaotic nature means that you can’t notch that out. So paper is better in this regard.
Looking forward to seeing your overlays.
I’d been glancing at the measurements in the data sheets measured at average 94dB@1m, and gleaned that the metal X seemed to play with the lowest distortion.
I concluded that W and M ranges were made to satisfy people using passive crossovers (wanting higher sensitivity). Metal is more “pistonic” but as one zooms in close enough, if the primary breakup changes in the off axis angles, that chaotic nature means that you can’t notch that out. So paper is better in this regard.
Looking forward to seeing your overlays.
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Here_s the first such pair as a null hypothesis - coil resistance should not matter, so let's see:
4 inch, paper, extended stroke, 8 vs. 4 Ohms
The 4 Ohm version has about 2-3 dB higher SPL for the same voltage, harmonics on average are about 4 dB higher (eyeballed). FR and harmonic structure are very similar. However, between 1 and 2 kHz, HD3 is about 10 dB higher, which is strange. This is about the most mismatched 4 / 8 R pair I have found.
4 inch, paper, extended stroke, 8 vs. 4 Ohms
The 4 Ohm version has about 2-3 dB higher SPL for the same voltage, harmonics on average are about 4 dB higher (eyeballed). FR and harmonic structure are very similar. However, between 1 and 2 kHz, HD3 is about 10 dB higher, which is strange. This is about the most mismatched 4 / 8 R pair I have found.
In terms of IMD this is totally normal amongst producers. Hard or very well damped cones will have less IMD then untreated papercones and similar provided it is used in it's intended range of course.
You pay for it in terms of breakup that needs to be filtered/notced, when the hard cone braks up it is much more 'violent' then a paper cone that does it gradually through it's range, resonance harmonics in some cases, and a driver that does not generally just roll off smootly.
In terms of THD it can vary
we have 94dB distortion plots for comparison. Also, there is a HD vs SPL plot. The 8” alu has insanely low distortion especially in the midrange. that would be my pick.
cheers
Lars/Purifi
cheers
Lars/Purifi
hi Thanh,
Our tweeter is getting close to finish. We have had to reject som off tool parts from our vendor and this holds up tooling of the faceplate. However, looks like we can move forward now. You have something to look forward to 🙂
cheers,
Lars
Our tweeter is getting close to finish. We have had to reject som off tool parts from our vendor and this holds up tooling of the faceplate. However, looks like we can move forward now. You have something to look forward to 🙂
cheers,
Lars
@tktran303 can I ask what you are designing?
I've been working on a composite baffle with integrated waveguide for use with 6.5" PTT driver & SB Satori tweeter, with an idea to make a few and sell them.
I've been working on a composite baffle with integrated waveguide for use with 6.5" PTT driver & SB Satori tweeter, with an idea to make a few and sell them.
A 2.5 way or MTM with twin PTT8.0X-08 for higher voltage sensitivity, with a HF unit with WG/baffle for constant directivity with a wider -6dB beam-width than a typical WG (eg. SB’s unit).
Aim is to watch the MW from Fc the way up to 16KHz (or beyond...)
The PTT tweeter could be used for an off-the-shelf / branded solution, but @fluid ’s prototype is using another hard-dome in his custom WG/my baffle.
Aim is to watch the MW from Fc the way up to 16KHz (or beyond...)
The PTT tweeter could be used for an off-the-shelf / branded solution, but @fluid ’s prototype is using another hard-dome in his custom WG/my baffle.
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