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DIY Sound Group Volt-6

hardisj

Major Contributor
Reviewer
Joined
Jul 18, 2019
Messages
2,907
Likes
13,588
Location
North Alabama
Full review copy/pasted from my site here:
https://www.erinsaudiocorner.com/loudspeakers/diysg_volt6/




DIYSG Volt-6 Speaker Review
  • Tuesday, Jun 1, 2021
DSC01956.JPG

Foreword / YouTube Video Review
The review on this website is a brief overview and summary of the objective performance of this speaker. It is not intended to be a deep dive. Moreso, this is information for those who prefer “just the facts” and prefer to have the data without the filler. Due to extremely limited time, I am not providing any subjective evaluation but hope the data will be enough for designers and DIY’ers alike that they can glean useful information.



Information and Photos
The DIY Sound Group Volt-6 is a DIY design from Matt Grant which is available in kit form from DIYSG. Here are some notes from the product page:
The Volt-6 has a custom made 6.5” coaxial using the same magnet and motor assembly as the Volt-8 and Volt-10. It’s not the prettiest woofer out there but if you need a small home theater speaker capable of high output and power handling, this is a good choice. Impressive X-max with a light weight cone gives this speaker a smooth sounding midrange even when played at high levels. The Celestion CDX1-1010 compression driver (tweeter) is installed on the back and fires through a small waveguide in the center of the woofer giving you point source sound and great off axis response. The crossover was designed to give an even response that not only excels for surround sound speaker use, but also for great front speaker performance but really should be paired with subwoofers that can handle the lower bass. The Volt-6 does quite well in small ported enclosures between .3 and .5cuft when used with a subwoofer. The Atmos version is a small sealed enclosure designed to play down to 115hz, which is perfect for Atmos use. You can use the Volt-6 in your ceiling without an enclosure for Atmos use if needed. For surround sound or mains, you should build the ported models.

These speakers were loaned to me by their owner, who built them from the kit.

DSC01957.JPG





CTA-2034 (SPINORAMA) and Accompanying Data
All data collected using Klippel’s Near-Field Scanner. The Near-Field-Scanner 3D (NFS) offers a fully automated acoustic measurement of direct sound radiated from the source under test. The radiated sound is determined in any desired distance and angle in the 3D space outside the scanning surface. Directivity, sound power, SPL response and many more key figures are obtained for any kind of loudspeaker and audio system in near field applications (e.g. studio monitors, mobile devices) as well as far field applications (e.g. professional audio systems). Utilizing a minimum of measurement points, a comprehensive data set is generated containing the loudspeaker’s high resolution, free field sound radiation in the near and far field. For a detailed explanation of how the NFS works and the science behind it, please watch the below discussion with designer Christian Bellmann:

The baffle is sloped at about a 76° angle which made it a bit tricky to measure but after some reconfiguring in the Klippel software, the reference axis was at the tweeter, at the same angle of the baffle.

Measurements are provided in a format in accordance with the Standard Method of Measurement for In-Home Loudspeakers (ANSI/CTA-2034-A R-2020). For more information, please see this link.

CTA-2034 / SPINORAMA:
CEA2034%20--%20DIYSG%20Volt-6%20%28Sloped%20Baffle%29.png



Early Reflections Breakout:
Early%20Reflections.png


Estimated In-Room Response:
Estimated%20In-Room%20Response.png


Horizontal Frequency Response (0° to ±90°):
SPL%20Horizontal.png


Vertical Frequency Response (0° to ±40°):
SPL%20Vertical.png


Horizontal Contour Plot (not normalized):
DIYSG%20VOLT-6_Horizontal_Spectrogram_Full.png


Horizontal Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Horizontal.png


Vertical Contour Plot (not normalized):
DIYSG%20VOLT-6_Vertical_Spectrogram_Full.png


Vertical Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Vertical.png






Additional Measurements

Impedance Magnitude and Phase + Equivalent Peak Dissipation Resistance (EPDR)

For those who do not know what EPDR is (ahem, me until 2020), Keith Howard came up with this metric which he defined in a 2007 article for Stereophile as:
… simply the resistive load that would give rise to the same peak device dissipation as the speaker itself.​
A note from Dr. Jack Oclee-Brown of Kef (who supplied the formula for calculating EPDR):
Just a note of caution that the EPDR derivation is based on a class-B output stage so it’s valid for typical class-AB amps but certainly not for class-A and probably has only marginal relevance for class-D amps (would love to hear from a class-D expert on this topic).​
DIYSG%20VOLT-6_Impedance_0.1v.png

On-Axis Response Linearity
DIYSG%20VOLT-6%20FR_Linearity.png

“Globe” Plots
These plots are generated from exporting the Klippel data to text files. I then process that data with my own MATLAB script to provide what you see. These are not part of any software packages and are unique to my tests.

Horizontal Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Horizontal_Polar.png



Vertical Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Vertical_Polar.png



Harmonic Distortion
Harmonic Distortion at 86dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2886dB%20%40%201m%29.png


Harmonic Distortion at 96dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2896dB%20%40%201m%29.png




Dynamic Range (Instantaneous Compression Test)
The below graphic indicates just how much SPL is lost (compression) or gained (enhancement; usually due to distortion) when the speaker is played at higher output volumes instantly via a 2.7 second logarithmic sine sweep referenced to 76dB at 1 meter. The signals are played consecutively without any additional stimulus applied. Then normalized against the 76dB result.
The tests are conducted in this fashion:
  1. 76dB at 1 meter (baseline; black)
  2. 86dB at 1 meter (red)
  3. 96dB at 1 meter (blue)
  4. 102dB at 1 meter (purple)
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components) instantaneously.
DIYSG%20VOLT-6_Compression.png


Long Term Compression Tests
The below graphics indicate how much SPL is lost or gained in the long-term as a speaker plays at the same output level for 2 minutes, in intervals. Each graphic represents a different SPL: 86dB and 96dB both at 1 meter.
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components).
The tests are conducted in this fashion:
  1. “Cold” logarithmic sine sweep (no stimulus applied beforehand)
  2. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  3. Interim logarithmic sine sweep (no stimulus applied beforehand) (Red in graphic)
  4. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  5. Final logarithmic sine sweep (no stimulus applied beforehand) (Blue in graphic)
The red and blue lines represent changes in the output compared to the initial “cold” test.
DIYSG%20VOLT-6_Long_Term_86_Compression.png

DIYSG%20VOLT-6_Long_Term_96_Compression.png



Placement Consideration (Effect of On-Wall Installation)
Many people seem to be using this speaker as an on-wall speaker for surround use. Therefore, the anechoic data - data taken in free space - is not fully representative of the Volt-6’s on-wall performance. Therefore, I placed the speaker outside on the ground, facing up. I placed the microphone on a boom and positioned the microphone 1 meter above the speaker as illustrated in the photograph below.
193112666_10101282020004213_166825222651126699_n.jpg

I have provided an overlay of the SPINORAMA’s on-axis response (black) vs the “Wall Mount” measurement (blue) below. This is intended to be a caution that speakers which are not specifically designed for on-wall use will result in fairly significant comb filtering so be advised of this.
DIYSG%20Volt-6%20%28Sloped%20Baffle%29%20--%20Anechoic%20On-Axis%20vs%20Ground%20Plane%20Wall%20Mount%20Emulation.png


Parting / Random Thoughts
  • Measured sensitivity averages approximately 88.4dB @ 1m.
  • I’m really surprised at the Dynamic Range and Compression test results. There is a significant amount of distortion below 100Hz which causes enhancement (solidified by simply looking at the harmonic distortion graphic). Above 100Hz through about 1kHz there is a good bit of compression. That all said, the long-term compression testing doesn’t look as bad. Just realize that the difference in frequency response is going to be quite different as you increase volume. Using an appropriate highpass filter (I’d estimate 100Hz or greater) will help this but not solve the issues.
  • The response linearity is pretty poor. If I am being honest, this just seems like a sub-par coaxial driver with poor tweeter/mid integration. I say that because the 6kHz region shows some sort of issue where the off-axis response is even higher in SPL than the on-axis response; something I typically see in waveguides and this is way above the crossover point. There are also pretty significant combing effects above this, especially above 10kHz.
  • There is a resonance around 800Hz (evidenced by the impedance blip, the “stacking” of frequency response magnitude and the increased compression, the latter of which is typically a sign of port resonance).
  • Remember what I said about wall-mounting this speaker. Ideally, you would flush mount the speaker in the wall or in the ceiling (as the designer suggests). This would help the bass rolloff by providing an “infinite baffle”, reinforcing the lower frequencies. Though, baffle step would need to be properly accounted for.
  • Note the vertical axis measurement doesn't appear to be perfectly aligned with the acoustic center of the speaker. This isn't for a lack of trying. I re-measured the speaker a few times, adjusting the reference point each time. Judging by the contour data, each measurement was either just above or just below the dead-center vertical alignment which makes me think that one of those angles I used was correct; there is just a good deal of comb filtering going on causing the high frequency measurements >10kHz to look out of sorts. What I have provided here is the best guesstimate at what is the correct angle for the angle of the baffle.
  • The vent tuning frequency seems to be off judging by the impedance sweep.

Support / Donate
If you like what you see here and want to help me keep it going, please consider donating via the PayPal Contribute link below. Donations help me pay for new items to test, hardware, miscellaneous items and costs of the site’s server space and bandwidth. All of which I pay out of pocket. So, if you can help chip in a few bucks, know that it is very much appreciated and that the support means a lot to me.

https://www.erinsaudiocorner.com/contribute/
 
Last edited:

Dj7675

Major Contributor
Forum Donor
Joined
Jan 12, 2019
Messages
1,571
Likes
1,848
Full review copy/pasted from my site here:
https://www.erinsaudiocorner.com/loudspeakers/diysg_volt6/




DIYSG Volt-6 Speaker Review
  • Tuesday, Jun 1, 2021
DSC01956.JPG

Foreword / YouTube Video Review
The review on this website is a brief overview and summary of the objective performance of this speaker. It is not intended to be a deep dive. Moreso, this is information for those who prefer “just the facts” and prefer to have the data without the filler. Due to extremely limited time, I am not providing any subjective evaluation but hope the data will be enough for designers and DIY’ers alike that they can glean useful information.



Information and Photos
The DIY Sound Group Volt-6 is a DIY design from Matt Grant which is available in kit form from DIYSG. Here are some notes from the product page:
The Volt-6 has a custom made 6.5” coaxial using the same magnet and motor assembly as the Volt-8 and Volt-10. It’s not the prettiest woofer out there but if you need a small home theater speaker capable of high output and power handling, this is a good choice. Impressive X-max with a light weight cone gives this speaker a smooth sounding midrange even when played at high levels. The Celestion CDX1-1010 compression driver (tweeter) is installed on the back and fires through a small waveguide in the center of the woofer giving you point source sound and great off axis response. The crossover was designed to give an even response that not only excels for surround sound speaker use, but also for great front speaker performance but really should be paired with subwoofers that can handle the lower bass. The Volt-6 does quite well in small ported enclosures between .3 and .5cuft when used with a subwoofer. The Atmos version is a small sealed enclosure designed to play down to 115hz, which is perfect for Atmos use. You can use the Volt-6 in your ceiling without an enclosure for Atmos use if needed. For surround sound or mains, you should build the ported models.

These speakers were loaned to me by their owner, who built them from the kit.

DSC01957.JPG





CTA-2034 (SPINORAMA) and Accompanying Data
All data collected using Klippel’s Near-Field Scanner. The Near-Field-Scanner 3D (NFS) offers a fully automated acoustic measurement of direct sound radiated from the source under test. The radiated sound is determined in any desired distance and angle in the 3D space outside the scanning surface. Directivity, sound power, SPL response and many more key figures are obtained for any kind of loudspeaker and audio system in near field applications (e.g. studio monitors, mobile devices) as well as far field applications (e.g. professional audio systems). Utilizing a minimum of measurement points, a comprehensive data set is generated containing the loudspeaker’s high resolution, free field sound radiation in the near and far field. For a detailed explanation of how the NFS works and the science behind it, please watch the below discussion with designer Christian Bellmann:

The baffle is sloped at about a 76° angle which made it a bit tricky to measure but after some reconfiguring in the Klippel software, the reference axis was at the tweeter, at the same angle of the baffle.

Measurements are provided in a format in accordance with the Standard Method of Measurement for In-Home Loudspeakers (ANSI/CTA-2034-A R-2020). For more information, please see this link.

CTA-2034 / SPINORAMA:
CEA2034%20--%20DIYSG%20Volt-6%20%28Sloped%20Baffle%29.png



Early Reflections Breakout:
Early%20Reflections.png


Estimated In-Room Response:
Estimated%20In-Room%20Response.png


Horizontal Frequency Response (0° to ±90°):
SPL%20Horizontal.png


Vertical Frequency Response (0° to ±40°):
SPL%20Vertical.png


Horizontal Contour Plot (not normalized):
DIYSG%20VOLT-6_Horizontal_Spectrogram_Full.png


Horizontal Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Horizontal.png


Vertical Contour Plot (not normalized):
DIYSG%20VOLT-6_Vertical_Spectrogram_Full.png


Vertical Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Vertical.png






Additional Measurements

Impedance Magnitude and Phase + Equivalent Peak Dissipation Resistance (EPDR)

For those who do not know what EPDR is (ahem, me until 2020), Keith Howard came up with this metric which he defined in a 2007 article for Stereophile as:
… simply the resistive load that would give rise to the same peak device dissipation as the speaker itself.​
A note from Dr. Jack Oclee-Brown of Kef (who supplied the formula for calculating EPDR):
Just a note of caution that the EPDR derivation is based on a class-B output stage so it’s valid for typical class-AB amps but certainly not for class-A and probably has only marginal relevance for class-D amps (would love to hear from a class-D expert on this topic).​
DIYSG%20VOLT-6_Impedance_0.1v.png

On-Axis Response Linearity
DIYSG%20VOLT-6%20FR_Linearity.png

“Globe” Plots
These plots are generated from exporting the Klippel data to text files. I then process that data with my own MATLAB script to provide what you see. These are not part of any software packages and are unique to my tests.

Horizontal Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Horizontal_Polar.png



Vertical Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Vertical_Polar.png



Harmonic Distortion
Harmonic Distortion at 86dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2886dB%20%40%201m%29.png


Harmonic Distortion at 96dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2896dB%20%40%201m%29.png




Dynamic Range (Instantaneous Compression Test)
The below graphic indicates just how much SPL is lost (compression) or gained (enhancement; usually due to distortion) when the speaker is played at higher output volumes instantly via a 2.7 second logarithmic sine sweep referenced to 76dB at 1 meter. The signals are played consecutively without any additional stimulus applied. Then normalized against the 76dB result.
The tests are conducted in this fashion:
  1. 76dB at 1 meter (baseline; black)
  2. 86dB at 1 meter (red)
  3. 96dB at 1 meter (blue)
  4. 102dB at 1 meter (purple)
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components) instantaneously.
DIYSG%20VOLT-6_Compression.png


Long Term Compression Tests
The below graphics indicate how much SPL is lost or gained in the long-term as a speaker plays at the same output level for 2 minutes, in intervals. Each graphic represents a different SPL: 86dB and 96dB both at 1 meter.
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components).
The tests are conducted in this fashion:
  1. “Cold” logarithmic sine sweep (no stimulus applied beforehand)
  2. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  3. Interim logarithmic sine sweep (no stimulus applied beforehand) (Red in graphic)
  4. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  5. Final logarithmic sine sweep (no stimulus applied beforehand) (Blue in graphic)
The red and blue lines represent changes in the output compared to the initial “cold” test.
DIYSG%20VOLT-6_Long_Term_86_Compression.png

DIYSG%20VOLT-6_Long_Term_96_Compression.png



Placement Consideration (Effect of On-Wall Installation)
Many people seem to be using this speaker as an on-wall speaker for surround use. Therefore, the anechoic data - data taken in free space - is not fully representative of the Volt-6’s on-wall performance. Therefore, I placed the speaker outside on the ground, facing up. I placed the microphone on a boom and positioned the microphone 1 meter above the speaker as illustrated in the photograph below.
193112666_10101282020004213_166825222651126699_n.jpg

I have provided an overlay of the SPINORAMA’s on-axis response (black) vs the “Wall Mount” measurement (blue) below. This is intended to be a caution that speakers which are not specifically designed for on-wall use will result in fairly significant comb filtering so be advised of this.
DIYSG%20Volt-6%20%28Sloped%20Baffle%29%20--%20Anechoic%20On-Axis%20vs%20Ground%20Plane%20Wall%20Mount%20Emulation.png


Parting / Random Thoughts
  • Measured sensitivity averages approximately 88.4dB @ 1m.
  • I’m really surprised at the Dynamic Range and Compression test results. There is a significant amount of distortion below 100Hz which causes enhancement (solidified by simply looking at the harmonic distortion graphic). Above 100Hz through about 1kHz there is a good bit of compression. That all said, the long-term compression testing doesn’t look as bad. Just realize that the difference in frequency response is going to be quite different as you increase volume. Using an appropriate highpass filter (I’d estimate 100Hz or greater) will help this but not solve the issues.
  • The response linearity is pretty poor. If I am being honest, this just seems like a sub-par coaxial driver with poor tweeter/mid integration. I say that because the 6kHz region shows some sort of issue where the off-axis response is even higher in SPL than the on-axis response; something I typically see in waveguides and this is way above the crossover point. There are also pretty significant combing effects above this, especially above 10kHz.
  • There is a resonance around 800Hz (evidenced by the impedance blip, the “stacking” of frequency response magnitude and the increased compression, the latter of which is typically a sign of port resonance).
  • Remember what I said about wall-mounting this speaker. Ideally, you would flush mount the speaker in the wall or in the ceiling (as the designer suggests). This would help the bass rolloff by providing an “infinite baffle”, reinforcing the lower frequencies. Though, baffle step would need to be properly accounted for.
  • Note the vertical axis measurement doesn’t appear to be perfectly aligned with the acoustic center of the speaker. This isn’t for a lack of trying. I re-measured the speaker a few times, adjusting the reference point each time. However, given the angled nature of the baffle, it’s a little tricky and this is as close to “perfect” as I could get.
  • The vent tuning frequency seems to be off judging by the impedance sweep.

Support / Donate
If you like what you see here and want to help me keep it going, please consider donating via the PayPal Contribute link below. Donations help me pay for new items to test, hardware, miscellaneous items and costs of the site’s server space and bandwidth. All of which I pay out of pocket. So, if you can help chip in a few bucks, know that it is very much appreciated and that the support means a lot to me.

https://www.erinsaudiocorner.com/contribute/
Thanks for testing the DIYSG speakers. I had the volt 6 As well as the 893 speakers for the front LCR. I have since moved on to Revel. Very interesting seeing them tested.
 
OP
hardisj

hardisj

Major Contributor
Reviewer
Joined
Jul 18, 2019
Messages
2,907
Likes
13,588
Location
North Alabama
Thanks for testing the DIYSG speakers. I had the volt 6 As well as the 893 speakers for the front LCR. I have since moved on to Revel. Very interesting seeing them tested.

Yea, unfortunately, the results don't indicate the kind of performance I was hoping for. But I also honestly wasn't sure what to expect thanks to the coaxial driver being used (most are pretty bad).
 

Maiky76

Senior Member
Joined
May 28, 2020
Messages
340
Likes
2,588
Location
French, leaving in China
Full review copy/pasted from my site here:
https://www.erinsaudiocorner.com/loudspeakers/diysg_volt6/




DIYSG Volt-6 Speaker Review
  • Tuesday, Jun 1, 2021
DSC01956.JPG

Foreword / YouTube Video Review
The review on this website is a brief overview and summary of the objective performance of this speaker. It is not intended to be a deep dive. Moreso, this is information for those who prefer “just the facts” and prefer to have the data without the filler. Due to extremely limited time, I am not providing any subjective evaluation but hope the data will be enough for designers and DIY’ers alike that they can glean useful information.



Information and Photos
The DIY Sound Group Volt-6 is a DIY design from Matt Grant which is available in kit form from DIYSG. Here are some notes from the product page:
The Volt-6 has a custom made 6.5” coaxial using the same magnet and motor assembly as the Volt-8 and Volt-10. It’s not the prettiest woofer out there but if you need a small home theater speaker capable of high output and power handling, this is a good choice. Impressive X-max with a light weight cone gives this speaker a smooth sounding midrange even when played at high levels. The Celestion CDX1-1010 compression driver (tweeter) is installed on the back and fires through a small waveguide in the center of the woofer giving you point source sound and great off axis response. The crossover was designed to give an even response that not only excels for surround sound speaker use, but also for great front speaker performance but really should be paired with subwoofers that can handle the lower bass. The Volt-6 does quite well in small ported enclosures between .3 and .5cuft when used with a subwoofer. The Atmos version is a small sealed enclosure designed to play down to 115hz, which is perfect for Atmos use. You can use the Volt-6 in your ceiling without an enclosure for Atmos use if needed. For surround sound or mains, you should build the ported models.

These speakers were loaned to me by their owner, who built them from the kit.

DSC01957.JPG





CTA-2034 (SPINORAMA) and Accompanying Data
All data collected using Klippel’s Near-Field Scanner. The Near-Field-Scanner 3D (NFS) offers a fully automated acoustic measurement of direct sound radiated from the source under test. The radiated sound is determined in any desired distance and angle in the 3D space outside the scanning surface. Directivity, sound power, SPL response and many more key figures are obtained for any kind of loudspeaker and audio system in near field applications (e.g. studio monitors, mobile devices) as well as far field applications (e.g. professional audio systems). Utilizing a minimum of measurement points, a comprehensive data set is generated containing the loudspeaker’s high resolution, free field sound radiation in the near and far field. For a detailed explanation of how the NFS works and the science behind it, please watch the below discussion with designer Christian Bellmann:

The baffle is sloped at about a 76° angle which made it a bit tricky to measure but after some reconfiguring in the Klippel software, the reference axis was at the tweeter, at the same angle of the baffle.

Measurements are provided in a format in accordance with the Standard Method of Measurement for In-Home Loudspeakers (ANSI/CTA-2034-A R-2020). For more information, please see this link.

CTA-2034 / SPINORAMA:
CEA2034%20--%20DIYSG%20Volt-6%20%28Sloped%20Baffle%29.png



Early Reflections Breakout:
Early%20Reflections.png


Estimated In-Room Response:
Estimated%20In-Room%20Response.png


Horizontal Frequency Response (0° to ±90°):
SPL%20Horizontal.png


Vertical Frequency Response (0° to ±40°):
SPL%20Vertical.png


Horizontal Contour Plot (not normalized):
DIYSG%20VOLT-6_Horizontal_Spectrogram_Full.png


Horizontal Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Horizontal.png


Vertical Contour Plot (not normalized):
DIYSG%20VOLT-6_Vertical_Spectrogram_Full.png


Vertical Contour Plot (normalized):
DIYSG%20VOLT-6%20Beamwidth_Vertical.png






Additional Measurements

Impedance Magnitude and Phase + Equivalent Peak Dissipation Resistance (EPDR)

For those who do not know what EPDR is (ahem, me until 2020), Keith Howard came up with this metric which he defined in a 2007 article for Stereophile as:
… simply the resistive load that would give rise to the same peak device dissipation as the speaker itself.​
A note from Dr. Jack Oclee-Brown of Kef (who supplied the formula for calculating EPDR):
Just a note of caution that the EPDR derivation is based on a class-B output stage so it’s valid for typical class-AB amps but certainly not for class-A and probably has only marginal relevance for class-D amps (would love to hear from a class-D expert on this topic).​
DIYSG%20VOLT-6_Impedance_0.1v.png

On-Axis Response Linearity
DIYSG%20VOLT-6%20FR_Linearity.png

“Globe” Plots
These plots are generated from exporting the Klippel data to text files. I then process that data with my own MATLAB script to provide what you see. These are not part of any software packages and are unique to my tests.

Horizontal Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Horizontal_Polar.png



Vertical Polar (Globe) Plot:
This represents the sound field at 2 meters - above 200Hz - per the legend in the upper left.
DIYSG%20VOLT-6_360_Vertical_Polar.png



Harmonic Distortion
Harmonic Distortion at 86dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2886dB%20%40%201m%29.png


Harmonic Distortion at 96dB @ 1m:
DIYSG%20Volt-6%20Hamonic%20Distortion%20%2896dB%20%40%201m%29.png




Dynamic Range (Instantaneous Compression Test)
The below graphic indicates just how much SPL is lost (compression) or gained (enhancement; usually due to distortion) when the speaker is played at higher output volumes instantly via a 2.7 second logarithmic sine sweep referenced to 76dB at 1 meter. The signals are played consecutively without any additional stimulus applied. Then normalized against the 76dB result.
The tests are conducted in this fashion:
  1. 76dB at 1 meter (baseline; black)
  2. 86dB at 1 meter (red)
  3. 96dB at 1 meter (blue)
  4. 102dB at 1 meter (purple)
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components) instantaneously.
DIYSG%20VOLT-6_Compression.png


Long Term Compression Tests
The below graphics indicate how much SPL is lost or gained in the long-term as a speaker plays at the same output level for 2 minutes, in intervals. Each graphic represents a different SPL: 86dB and 96dB both at 1 meter.
The purpose of this test is to illustrate how much (if at all) the output changes as a speaker’s components temperature increases (i.e., voice coils, crossover components).
The tests are conducted in this fashion:
  1. “Cold” logarithmic sine sweep (no stimulus applied beforehand)
  2. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  3. Interim logarithmic sine sweep (no stimulus applied beforehand) (Red in graphic)
  4. Multitone stimulus played at desired SPL/distance for 2 minutes; intended to represent music signal
  5. Final logarithmic sine sweep (no stimulus applied beforehand) (Blue in graphic)
The red and blue lines represent changes in the output compared to the initial “cold” test.
DIYSG%20VOLT-6_Long_Term_86_Compression.png

DIYSG%20VOLT-6_Long_Term_96_Compression.png



Placement Consideration (Effect of On-Wall Installation)
Many people seem to be using this speaker as an on-wall speaker for surround use. Therefore, the anechoic data - data taken in free space - is not fully representative of the Volt-6’s on-wall performance. Therefore, I placed the speaker outside on the ground, facing up. I placed the microphone on a boom and positioned the microphone 1 meter above the speaker as illustrated in the photograph below.
193112666_10101282020004213_166825222651126699_n.jpg

I have provided an overlay of the SPINORAMA’s on-axis response (black) vs the “Wall Mount” measurement (blue) below. This is intended to be a caution that speakers which are not specifically designed for on-wall use will result in fairly significant comb filtering so be advised of this.
DIYSG%20Volt-6%20%28Sloped%20Baffle%29%20--%20Anechoic%20On-Axis%20vs%20Ground%20Plane%20Wall%20Mount%20Emulation.png


Parting / Random Thoughts
  • Measured sensitivity averages approximately 88.4dB @ 1m.
  • I’m really surprised at the Dynamic Range and Compression test results. There is a significant amount of distortion below 100Hz which causes enhancement (solidified by simply looking at the harmonic distortion graphic). Above 100Hz through about 1kHz there is a good bit of compression. That all said, the long-term compression testing doesn’t look as bad. Just realize that the difference in frequency response is going to be quite different as you increase volume. Using an appropriate highpass filter (I’d estimate 100Hz or greater) will help this but not solve the issues.
  • The response linearity is pretty poor. If I am being honest, this just seems like a sub-par coaxial driver with poor tweeter/mid integration. I say that because the 6kHz region shows some sort of issue where the off-axis response is even higher in SPL than the on-axis response; something I typically see in waveguides and this is way above the crossover point. There are also pretty significant combing effects above this, especially above 10kHz.
  • There is a resonance around 800Hz (evidenced by the impedance blip, the “stacking” of frequency response magnitude and the increased compression, the latter of which is typically a sign of port resonance).
  • Remember what I said about wall-mounting this speaker. Ideally, you would flush mount the speaker in the wall or in the ceiling (as the designer suggests). This would help the bass rolloff by providing an “infinite baffle”, reinforcing the lower frequencies. Though, baffle step would need to be properly accounted for.
  • Note the vertical axis measurement doesn't appear to be perfectly aligned with the acoustic center of the speaker. This isn't for a lack of trying. I re-measured the speaker a few times, adjusting the reference point each time. Judging by the contour data, each measurement was either just above or just below the dead-center vertical alignment which makes me think that one of those angles I used was correct; there is just a good deal of comb filtering going on causing the high frequency measurements >10kHz to look out of sorts. What I have provided here is the best guesstimate at what is the correct angle for the angle of the baffle.
  • The vent tuning frequency seems to be off judging by the impedance sweep.

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Hi,

Here is my take on the EQ.

The raw data with corrected ER and PIR:

Score no EQ: 0.3
With Sub: 4.0

Spinorama with no EQ:
  • Satellite for HT?
DIYSG VOLT-6 No EQ Spinorama.png

Directivity:
Quite bad...
 2D surface Directivity Contour Only Data.png

DIYSG VOLT-6 LW Better data.png


EQ design:
I have generated two EQs. The APO config files are attached.
  • The first one, labelled, LW is targeted at making the LW flat
  • The second, labelled Score, starts with the first one and adds the score as an optimization variable.
  • The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose although this is very unlikely no one would do that with this speaker...
Score EQ LW: 1.8
with sub: 5.3

Score EQ Score: 2.8
with sub: 6.1

Code:
DIYSG VOLT-6 APO EQ LW 96000Hz
June022021-114145

Preamp: -3.5 dB

Filter 1: ON HPQ Fc 90.2 Hz Gain 0 dB Q 1.23
Filter 2: ON PK Fc 178.3 Hz Gain -1.78 dB Q 1.58
Filter 3: ON PK Fc 643 Hz Gain -1.17 dB Q 2.6
Filter 4: ON PK Fc 1776 Hz Gain -4.35 dB Q 2.13
Filter 5: ON PK Fc 2719 Hz Gain 4.44 dB Q 2.94
Filter 6: ON PK Fc 9958 Hz Gain -1.57 dB Q 4

DIYSG VOLT-6 APO EQ Score 96000Hz
June022021-113644

Preamp: -2.6 dB

Filter 1: ON HPQ Fc 90.8 Hz Gain 0 dB Q 1.25
Filter 2: ON PK Fc 175.5 Hz Gain -1.78 dB Q 1.5
Filter 3: ON PK Fc 655 Hz Gain -1.62 dB Q 2.13
Filter 4: ON PK Fc 1816 Hz Gain -4.65 dB Q 1.67
Filter 5: ON PK Fc 2663 Hz Gain 4.4 dB Q 3.93
Filter 6: ON PK Fc 6065 Hz Gain -2.82 dB Q 3.56
Filter 7: ON PK Fc 9417 Hz Gain -3.32 dB Q 2.95

DIYSG VOLT-6 EQ Design.png


Spinorama EQ LW
DIYSG VOLT-6 LW EQ Spinorama.png


Spinorama EQ Score
DIYSG VOLT-6 Score EQ Spinorama.png


Zoom PIR-LW-ON
DIYSG VOLT-6 Zoom.png


Regression - Tonal
DIYSG VOLT-6 Regression - Tonal.png


Radar no EQ vs EQ score
DIYSG VOLT-6 Radar.png


The rest of the plots is attached.
 

Attachments

  • DIYSG VOLT-6 APO EQ LW 96000Hz.txt
    347 bytes · Views: 37
  • DIYSG VOLT-6 APO EQ Score 96000Hz.txt
    400 bytes · Views: 49
  • DIYSG VOLT-6 Vertical 3D Directivity data.png
    DIYSG VOLT-6 Vertical 3D Directivity data.png
    595.1 KB · Views: 29
  • DIYSG VOLT-6 Horizontal 3D Directivity data.png
    DIYSG VOLT-6 Horizontal 3D Directivity data.png
    594 KB · Views: 29
  • DIYSG VOLT-6 Normalized Directivity data.png
    DIYSG VOLT-6 Normalized Directivity data.png
    492.6 KB · Views: 27
  • DIYSG VOLT-6 Raw Directivity data.png
    DIYSG VOLT-6 Raw Directivity data.png
    834.2 KB · Views: 25
  • DIYSG VOLT-6 Reflexion data.png
    DIYSG VOLT-6 Reflexion data.png
    273.4 KB · Views: 34
  • DIYSG VOLT-6 LW data.png
    DIYSG VOLT-6 LW data.png
    290.9 KB · Views: 43
  •  2D surface Directivity Contour Data.png
    2D surface Directivity Contour Data.png
    264.4 KB · Views: 32
  •  3D surface Vertical Directivity Data.png
    3D surface Vertical Directivity Data.png
    438.7 KB · Views: 36
  •  3D surface Horizontal Directivity Data.png
    3D surface Horizontal Directivity Data.png
    442.7 KB · Views: 27
Last edited:

Rick Sykora

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Thanks Erin, but while it is great to have more DIY speakers tested, this one is a nonstarter out the gate. Whether your time or Amir’s, would not waste any more when the impedance plot is this bad. This one is comparable to the first Purifi SPK5 that @amirm tested. Suggest the following test protocol for DIY speakers (but applies in any case)…
  1. Check for designer’s impedance measurements before someone ships a speaker to you. If there is none, see if the builder has. If none exist, you risk that the build does not match the design and probably should be aborted at this point. Otherwise, any further results will be suspect.
  2. Plot the impedance next. If it does not look ”normal”, would abort the review. At this point, the question is whether you want to attempt a fix or not. If the plot appears reasonable…
  3. Unless it is sealed design, check the box tuning frequency. If it is not close to the supplied one, probably another fix or abort case.
  4. If the impedance plot is showing major resonance blips, may be that the build is bad. This another judgement call situation. Would consider plotting the frequency response to see if it indicates the resonances are audible.
May be obvious, but a simple resistance check before hooking into your system is advisable too. Wiring coming loose in shipping may be open or shorted and may not want to expose more sensitive test equipment to extreme conditions. :cool:
 
Last edited:
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hardisj

hardisj

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This one is comparable to the first Purifi SPK5 that @amirm tested

Yea, I remember that... was that your build? I seem to remember you guys having an issue with one you sent in... something to do with the ports not being seated fully?

At any rate, yes, good advice. I always perform a basic impedance sweep first along with a gated response just to make sure things make sense. Then I kick off the full scan. In this case, while the impedance looked weird in the tuning area, I was mostly concerned with what the coaxial's response looked like. Hardly anyone produces a good coax and these particular drive units are widely used in this design type.
 

Rick Sykora

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Yea, I remember that... was that your build? I seem to remember you guys having an issue with one you sent in... something to do with the ports not being seated fully?

At any rate, yes, good advice. I always perform a basic impedance sweep first along with a gated response just to make sure things make sense. Then I kick off the full scan. In this case, while the impedance looked weird in the tuning area, I was mostly concerned with what the coaxial's response looked like. Hardly anyone produces a good coax and these particular drive units are widely used in this design type.

No, the SPK5 was not mine, but did help fix it for Amir's final test...

As I have mentioned to others that may want to DIY, you are your own QA. In this case, an impedance plot not only reveals whether the box is tuned correctly, it is also a great indicator of whether the crossover is wired properly. Know you put in extra effort (really like simulated wall test for this), but unless the design is validated, the results are not representative. Thanks for the effort!
 

Matias

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I don't understand why the designers finish their speaker projects, and we only find out its spin after going through a 100k usd Klippel NFS measurement.

The designer could also measure his projects anechoically with quite high resolution using a 80 usd UMIK-1 and free software (brilliant tutorial by @napilopez here), even if it takes a learning curve and some hours to measure each iteration. At least the designer could test prototypes and improve until the limits of his measurements, and only then finish the project, publish the spin, and use Amir/Erin's NFS as a high resolution validation only. Makes a lot more sense to me.
 

Ericglo

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Seriously, the LF rolloff is quite high before the sine wave FR. I guess these would be an option for those with close surrounds to the listening position.


One thing I noticed on your outside measurement is the mic placement. Since these are angled, would it have made a difference to angle the mic back towards the driver?
 
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hardisj

hardisj

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One thing I noticed on your outside measurement is the mic placement. Since these are angled, would it have made a difference to angle the mic back towards the driver?

I mentioned this in the review; at least wrt to the NFS measurements. But angling the mic itself would be of little consequence. The main thing is to put it at the correct plane. Which is what took me some time to get as correct as I could.
 
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