A nice sensitive midrange with a smooth on and off-axis response, so that it blends beautifully with a waveguide around 2-2,2kHz
How close is too close? I'm about to do the cut-offs in a 15L Lenovo pack tweaking a Directiva R1 with Purifi PRs and stuff the bottom reducing volume to 12~13L. The cabinet is not too deep, certainly less deep than Evgenyi's Puriwave. Side mounted PRs will be closer to the drive than other designs and that might raise the issue of midrange leakage.
I assume rear mount will also get a share of the (more directional) midrange. The drawing is almost to scale, to convey the ratios. What is the recommendation in this case, side or rear PRs ?
Thanks for the patience
@lrisbo:
Hi Lars,
I've noticed, that, in the list of driver characteristics on your homepage you mention 'Low Magnetic Hysteresis Distortion' for every driver, except the PTT6.5M models, which has 'Ultra Low Magnetic Hysteresis Distortion'.
Is this due to the motor construction (magnet size / voice coil size) in general or just due to the fact that this driver will not reach the same excursion levels like the W and X models (which of cause is also a result of the construction).
Or in other words: Does the hysteresis distortion keeps 'ultra low' as well, as long as you use the W and X models only with limited excursion, e.g. as a midrange or is the hysteresis distortion with low excursion also higher than in the M model ?
Or again in other words: Does the hysteresis distortion directly correlate with the excursion?
Hi Lars,
I've noticed, that, in the list of driver characteristics on your homepage you mention 'Low Magnetic Hysteresis Distortion' for every driver, except the PTT6.5M models, which has 'Ultra Low Magnetic Hysteresis Distortion'.
Is this due to the motor construction (magnet size / voice coil size) in general or just due to the fact that this driver will not reach the same excursion levels like the W and X models (which of cause is also a result of the construction).
Or in other words: Does the hysteresis distortion keeps 'ultra low' as well, as long as you use the W and X models only with limited excursion, e.g. as a midrange or is the hysteresis distortion with low excursion also higher than in the M model ?
Or again in other words: Does the hysteresis distortion directly correlate with the excursion?
hi @Matty
Thanks for noticing the language. The lack of últra'must be a mistake. We judge the hysteresis distortion from the distortion of the current. Hysteresis typically dominates the 3rd harmonic above 2-300Hz so 1kHz is a good data point to look at. Comparing the 1kHz on Fig 6 and 7 shows that the M version is pretty much on par or possibly having a slightly elevated level compared with the X stroke (the M version coil packs more windings into the gap). If we normalise to the same SPL then the M version would probably come out best due to its higher sensitivity (less voltage/current needed for the same SPL). So yes, there probably is a small difference to the favor of the W and M versions.
Thanks for noticing the language. The lack of últra'must be a mistake. We judge the hysteresis distortion from the distortion of the current. Hysteresis typically dominates the 3rd harmonic above 2-300Hz so 1kHz is a good data point to look at. Comparing the 1kHz on Fig 6 and 7 shows that the M version is pretty much on par or possibly having a slightly elevated level compared with the X stroke (the M version coil packs more windings into the gap). If we normalise to the same SPL then the M version would probably come out best due to its higher sensitivity (less voltage/current needed for the same SPL). So yes, there probably is a small difference to the favor of the W and M versions.
Commerical offering the BePure 2 by Salk Signature Sound
https://www.audiocircle.com/index.php?topic=182516.0
https://www.salksound.com/model.php?model=BePure+2
https://www.audiocircle.com/index.php?topic=182516.0
https://www.salksound.com/model.php?model=BePure+2
Hi Lars,
I wondered if you had any info regarding where you would consider the acoustic centre of your 8" driver (or any of your drivers for that matter) is in relation to the mounting face, I am not sure if this varies with frequency but an approximate distance at useable crossover frequencies would be useful to builders.
My active build is coming along slowly, 24db LR crossover and four way Purifi amps are ready, the spherical bass cabs part done (45l volume will be reduce with a smaller sphere offset internally so I can play around with final volume and reduce standing waves)
My Viawave tweeters will be mounted in a close coupled pod and hopefully set back to align the acoustic centres.
The final crossover frequency will probably be 2k2 but will depend on the 8 ohm driver specs (any update available?)
Cheers Steve
I wondered if you had any info regarding where you would consider the acoustic centre of your 8" driver (or any of your drivers for that matter) is in relation to the mounting face, I am not sure if this varies with frequency but an approximate distance at useable crossover frequencies would be useful to builders.
My active build is coming along slowly, 24db LR crossover and four way Purifi amps are ready, the spherical bass cabs part done (45l volume will be reduce with a smaller sphere offset internally so I can play around with final volume and reduce standing waves)
My Viawave tweeters will be mounted in a close coupled pod and hopefully set back to align the acoustic centres.
The final crossover frequency will probably be 2k2 but will depend on the 8 ohm driver specs (any update available?)
Cheers Steve
spresto9 adding my complements to the Birchply spheres. Birchply is my longtime favorite material for woodworking and resulting speaker boxes with exposed layers a preferred look. That is taken to its perhaps ultimate expression in such spheres. Brovo.
I would consider just how powerful the motors are in Purifi drivers and interior box pressures that result. I suggest sealing your spheres with epoxy or something similar based on my experiences with much simpler butt joints.
PTT6.5W04 and the evil twins PTT6.5PR want to explode your speaker box
https://www.diyaudio.com/community/...er-speaker-builds.352063/page-24#post-6383932
Thank you for the compliments, I'm several months from finished yet, the sphere construction came from the web and the initial accuracy of the triangles came from the cnc shop, me cutting them in my workshop would have led to too many accumulated errors!
Steve
my friend I have the exact same Drivers please can you share the Crossover design
regards
anand
Hi Lars,
Personally I hope there will be a Alu version of 5.25, same magnet but with 2 layer voice coil?
Probably loses 30% BL with a lighter cone, but that would made the lowest midrange distortion small midwoofer. Needs larger box for reflex, but will make a super slim floorstander friendly. Or, for us DSP speaker builders it didn't matter at all..
Even better, that hyperthetical driver would make a 7L sealed "LS3/5A" killer, with 40hz -6db (I assume 20g mms and 5.4 N/A) and 95db max SPL >50hz thanks to its long stroke.
Best,
Hello Steve,
you won't reduce standing waves with spherical cabinet. You can't reduce standing waves with geometry.
You only shift frequencies depending on geometry.
You will always have standing waves no matter the geometry.
https://www.acculution.com/single-post/037-misconceptions-in-acoustics
Nice built though!
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Anyone looking for aluminum baffles? I'm working out a process for making custom baffles and the first go was to make one for the six inch Purifi with waveguide. The main tweaks I'm planning are some minor changes to the rear panel seal geometry and some faster machining strategies. Dialing in the anodize procedure is the other main objective. Note the exaggerated mounting holes; on the rear side they have a deep well chamfer and the idea is to have custom chamfered nuts with a rubber gasket seal. So the mounting bolts don't contact the baffle, and because the driver is essentially free floating the chamfered nut geometry actually handles the centering problem. Dunno whether it's a good or bad design feature, but making tweaks on the overall design is a fairly negligible fix.
I'm thinking I can do em from about 400-1200$ per pair depending of the level of finish. Also working on the flush mount bolts specific to Purifi, as can be seen in one of the mounting holes. So I was thinking to do a baffle plus hardware package for convenience. This was just a proof of concept so if there is any need for this sort of work give me a shout.
I'm thinking I can do em from about 400-1200$ per pair depending of the level of finish. Also working on the flush mount bolts specific to Purifi, as can be seen in one of the mounting holes. So I was thinking to do a baffle plus hardware package for convenience. This was just a proof of concept so if there is any need for this sort of work give me a shout.