This is a second review and detailed measurements of Purifi woofer reference design implementation by Celuaris called SPK5. The original sample had some enclosure leakage issues which have been resolved in this unit due to collaboration between our DIY expert, @Rick Sykora, and builder, @sgoldwin.
I am going to borrow the picture from the last review since nothing is changed in that regard:
The crossover is now built inside the unit rather using the external one in the previous reference design.
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.
I performed over 1000 measurement which resulted in error rate of around 1%.
Temperature was 58 degrees F at sea level. I kept the speaker indoor at 70 degrees prior to starting the measurements.
Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.
Reference axis was the tweeter center which in case of these AMT tweeters is a bit inexact.
Celuaris SPK5 Purifi Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
Compared to the first sample, bass extends lower but it starts to droop starting at 100 Hz. We have a dip around 350 Hz which is caused by port resonance:
I am disappointed in the uneven response of the tweeter which has at least one resonance which showed up in the spin graph above.
Early window is fine other than showing that the tweeter due to being narrow width-wise, is starting to "beam" (narrow its radiation angle:
We see that just the same in our predicted in-room response:
The main claim to fame of Purifi driver is low distortion -- something we did not see in the first sample I tested. Fortunately here it becomes the star with strong showing:
It is so good that it makes the tweeter really look bad.
Horizontal directivity now is much smoother:
Here is our vertical:
Finally, the impedance and phase:
Celuaris SPK5 Purifi Speaker Listening Tests
The sample speaker I have has SpeakOn connector and the only cord I had for it did not extend long enough to test the unit where I normally do. So I had to move the speaker to the right side of my room where there is no bass enhancement. Whether it was that or something else, the results were quite unsatisfying. There was not a whole lot of bass at normal playback levels. Due to low efficiency, I had to push the speaker hard to get bass out of it but then the winding would suddenly jump the gap and cause nasty static. Tracks with deep bass didn't distort the speaker but they were hardly played down low either. I played around a bit with EQ but didn't get far so gave up.
To make sure the new location or my mood was not at fault, I replace the SPK5 with Revel M106 and boy what joy there was with that speaker. Thundering and clean bass was back as was warm tonality. I could detect no more distortion there than I did in SPK5.
Conclusions
If this were a test of distortion for the Purifi driver, mission is accomplished. This is one low distortion driver. Alas, the reference design that Purifi has created is not optimal. The tweeter I feel is not the right match nor is the enclosure to get proper bass and efficiency here. I am not sure of the purpose of a fancy driver if you don't have much bass and you have low efficiency to boot. Objectively the results look better than my impression so perhaps I am being too harsh. I don't know.
As is, I can't recommend SPK5. Feel bad saying that despite the heroic efforts of its builder who went through some five (5) samples to get us to this point with transatlantic shipping issues, samples getting lost, etc.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I am going to borrow the picture from the last review since nothing is changed in that regard:
The crossover is now built inside the unit rather using the external one in the previous reference design.
Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.
I performed over 1000 measurement which resulted in error rate of around 1%.
Temperature was 58 degrees F at sea level. I kept the speaker indoor at 70 degrees prior to starting the measurements.
Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.
Reference axis was the tweeter center which in case of these AMT tweeters is a bit inexact.
Celuaris SPK5 Purifi Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:
Compared to the first sample, bass extends lower but it starts to droop starting at 100 Hz. We have a dip around 350 Hz which is caused by port resonance:
I am disappointed in the uneven response of the tweeter which has at least one resonance which showed up in the spin graph above.
Early window is fine other than showing that the tweeter due to being narrow width-wise, is starting to "beam" (narrow its radiation angle:
We see that just the same in our predicted in-room response:
The main claim to fame of Purifi driver is low distortion -- something we did not see in the first sample I tested. Fortunately here it becomes the star with strong showing:
It is so good that it makes the tweeter really look bad.
Horizontal directivity now is much smoother:
Here is our vertical:
Finally, the impedance and phase:
Celuaris SPK5 Purifi Speaker Listening Tests
The sample speaker I have has SpeakOn connector and the only cord I had for it did not extend long enough to test the unit where I normally do. So I had to move the speaker to the right side of my room where there is no bass enhancement. Whether it was that or something else, the results were quite unsatisfying. There was not a whole lot of bass at normal playback levels. Due to low efficiency, I had to push the speaker hard to get bass out of it but then the winding would suddenly jump the gap and cause nasty static. Tracks with deep bass didn't distort the speaker but they were hardly played down low either. I played around a bit with EQ but didn't get far so gave up.
To make sure the new location or my mood was not at fault, I replace the SPK5 with Revel M106 and boy what joy there was with that speaker. Thundering and clean bass was back as was warm tonality. I could detect no more distortion there than I did in SPK5.
Conclusions
If this were a test of distortion for the Purifi driver, mission is accomplished. This is one low distortion driver. Alas, the reference design that Purifi has created is not optimal. The tweeter I feel is not the right match nor is the enclosure to get proper bass and efficiency here. I am not sure of the purpose of a fancy driver if you don't have much bass and you have low efficiency to boot. Objectively the results look better than my impression so perhaps I am being too harsh. I don't know.
As is, I can't recommend SPK5. Feel bad saying that despite the heroic efforts of its builder who went through some five (5) samples to get us to this point with transatlantic shipping issues, samples getting lost, etc.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/