Purifi SPK5 Speaker Review (Prototype)

[Chromatischism]

I would measure even closer to eliminate room effects. Point the mic at the center of the driver at a distance of 0.25-0.50", measure at a much lower SPL, and use the appropriate mic calibration file (0°).

 

[andreasmaaan]

I think Manufacturer overstates it, but yes I put together and try to sell these copies of the SPK5 specification.

Here is an overlay of the SPL for individual woofer and tweeter. Mic at 1m aimed at centre spot between woofer and tweeter. No smoothing, Very short gating to try and capture direct sound. Scaling done to same limits as in Purifi App Note.

View attachment 99253

Same chart, but limited to 200-20kHz
View attachment 99255

That's getting better. Could you please re-post the first graph you posted in post #192, but with the more standard scale (200Hz-20kHz, 45dB-95dB)?

 

[sgoldwin]

Good graph interpolation @ctrl. However the tweeter rising response is still puzzling, up 10 dB. Even accounting for a non-calibrated mic, 10 is too much... I presume the xo is correctly made as it is made by Purifi (at least it was on the units that Amir tested). Let's see what happens.

not a good assumption. The crossover is a kit I purchase from Purifi, consisting of the PCB and the components. I then stuff and solder the PCB, providing plenty of opportunity to screw it up.

 

[sgoldwin]

That's getting better. Could you please re-post the first graph you posted in post #192, but with the more standard scale (200Hz-20kHz, 45dB-95dB)?

Here you go. Weirdly, brown is normal, green is reversed tweeter polarity.

 

[Yevhen]

So, here is a comparison of the measurements from the manufacturer and @sgoldwin.

This looks quite good. The crossover of the woofer is definitely set up correctly.
The tweeter curve looks a bit strange, but I think @sgoldwin said somewhere that his measurement microphone is not calibrated, which would explain the strong high frequency sound pressure increase.

According to this data, I would say that almost everything is connected correctly.
Only it should be so that if all chassis are connected with the correct polarity, then the green curve shown in post#192 should be measured and if the polarity is reversed for one chassis, the brown curve.

It is very important that it is done identically for both speakers so that the speakers do not radiate sound in opposing phase.

View attachment 99257

Guys, I'm also trying to measure my 8ohm version with Dayton mic (more or less flat response) and see the same steep rise at 5-20kHz when mic is really on axis of the tweeter. Is it normal? It doesn't sound nice to me. I love the smooth sound of the woofer alone, but not with this tweeter/crossover.

 

[Yevhen]

Here you go. Weirdly, brown is normal, green is reversed tweeter polarity.

View attachment 99294

Can you hear that rise at 5-20kHz when listen to the music? Which crossover connection sounds more pleasant or neutral to you?

 

[Yevhen]

I want to contact HiFiCompass to get my 8ohm Purifi-based speaker working properly. Maybe even with a different tweeter. Would anyone like to join?

 

[ctrl]

Guys, I'm also trying to measure my 8ohm version with Dayton mic (more or less flat response) and see the same steep rise at 5-20kHz when mic is really on axis of the tweeter. Is it normal? It doesn't sound nice to me. I love the smooth sound of the woofer alone, but not with this tweeter/crossover.

To get to the bottom of the matter, please perform the frequency response measurement halfway between the tweeter and woofer. Perhaps the speaker was developed on the basis of this axis.

Also make a measurement with a polarity reversed chassis to see if the phase alignment improves with this measurement axis.

Sorry @Yevhen, completely scrued you up with @sgoldwin

 

[sgoldwin]

Well, I am old and my HF hearing is kaput, but I don't particularly hear that rise or experience the SPK5 as bright or fatiguing. Nor do I hear much of a difference when the tweeter polarity is reversed, although measurement indicates it should be a faire bit smoother when reversed.

I'm inclined to go with @ctrl in #198 and say that the crossover is working, and get the speaker off to @amirm for another go in the Klippel to see how it really measures.

Thank you all for useful advice and insight.

 

[Yevhen]

To get to the bottom of the matter, please perform the frequency response measurement halfway between the tweeter and woofer. Perhaps the speaker was developed on the basis of this axis.

Also make a measurement with a polarity reversed chassis to see if the phase alignment improves with this measurement axis.

Can't anymore. Disassembled the setup and packed the speakers to send them back in 1-2 days if HiFiCompass will not reply. I saw around 3-5dB difference between inphase/antiphase connection, but very sensitive to vertical position, even 15deg

 

[Rick Sykora]

I have one of Seth's SPK5s for a couple of days now. Have confirmed his measurements and found the root cause of the polarity issue. The polarity silk screening for the tweeter input is incorrect.

This probably is not an issue using the speakon connection, but will be if you wire the crossover for internal use and wire directly to the board.

Mystery solved!

 

[Rick Sykora]

Checked and the Speakon connection is ok.

Explains why it slipped by Purifi. I have notified them and they confirmed the error.

 

[sgoldwin]

I just got an email from Purifi about it. Thanks Rick!

 

[Yevhen]

I have one of Seth's SPK5s for a couple of days now. Have confirmed his measurements and found the root cause of the polarity issue. The polarity silk screening for the tweeter input is incorrect.

This probably is not an issue using the speakon connection, but will be if you wire the crossover for internal use and wire directly to the board.

Mystery solved!

Hi Rick,

Do you like the sound of the speakers with proper polarity?
I heard several times that those Mundorfs are not good below 5kHz.
I'll be doing new project with Viawave's ribbons.

 

[Rick Sykora]

Hi Rick,

Do you like the sound of the speakers with proper polarity?
I heard several times that those Mundorfs are not good below 5kHz.
I'll be doing new project with Viawave's ribbons.

Will let you know. Am still rebuilding these. They have been partially restored after shipping damage. Right now I only have one and it is operating without the brace and a 3 inch cardboard tube in place of the fancy duct. It is still pretty leaky by my measurements.

 

[Yevhen]

Will let you know. Am still rebuilding these. They have been partially restored after shipping damage. Right now I only have one and it is operating without the brace and a 3 inch cardboard tube in place of the fancy duct. It is still pretty leaky by my measurements.

Thanks! What I noticed in my setup is that the woofer connected directly to PA produces incredibly fast and tight bass. Please try if you have time. But then the crossover ruins that magic. I wonder if the ferrite-based 1.5mH coil with a lower DC resistance could be a better choice. You maybe sacrifice a bit of THD but get at least 3x higher damping factor for the woofer...

 

[jhaider]

The backside is butchered up by me opening it back together (screws were very stiff resulting in me stripping a bunch ).

View attachment 95358

Philips screwdriver/bit?

 

[Massimo]

I just got an email from Purifi about it. Thanks Rick!

Was Purifi aware, prior to your inquiry, that the polarity of the Mundorf tweeters was reversed? If not, they may not have designed the SPK5 with optimal crossover point.

 

[Yevhen]

Was Purifi aware, prior to your inquiry, that the polarity of the Mundorf tweeters was reversed? If not, they may not have designed the SPK5 with optimal crossover point.

I talked to them a month ago. They checked and after a few days confirmed all was correct. As I understand, the schematic is fine, just a silkscreen error on PCB. So probably, Purifi had proper polarity in their setup.

 

[Rick Sykora]

Was Purifi aware, prior to your inquiry, that the polarity of the Mundorf tweeters was reversed? If not, they may not have designed the SPK5 with optimal crossover point.

As mentioned earlier, the polarity on the speakon connector input is correct. Once wired properly, the speaker measures flattish and sounds like a good quality speaker. Have not analyzed the crossover design further, but @ctrl did earlier and he is really good at it. The crossover is around 3k and may seem a bit high, but that tweeter is not designed to go much lower either.

Will know better once Amir gets a more pristine one to measure.