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DIY Anti-Diffraction Frame on Sony SS-CS5 with Spin!

BenB

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Many months ago Erin reviewed the Sony SS CS5 speakers. I had previously developed a modification for that speaker that included a DIY anti-diffraction frame made out of PVC, and a simple resistor short. After discussions with Erin, he agreed to test the anti-diffraction frame by itself. I agreed this was a better option, because it isolated the impact of the frame. If you change 2 things at once it's impossible to know for sure the impact of either modification in isolation.

Erin soon identified an issue with the measurements that showed evidence of a resonance near 2 kHz. His prior measurement of the CS5 didn't show this resonance, so it seemed highly plausible that the frame was causing this resonance; probably vibrating against the cabinet. I mentioned that I had heard no evidence of a resonance when listening to the speaker with the frame attached, and Erin also noted no issues during listening. We figured the resonance was too narrowband to be impactful on most music selections.

It turns out that Erin attached the frame to the "2nd unit" in the pair of CS5s, while he had initially measured the "1st unit" in his review. The resonance was a feature of the 2nd unit with or without the frame. Erin discovered this by removing the frame and measuring unit 2 without it. As a result, the comparative measurements I have for the frame are on unit 2, which suffers from a resonance near 2 kHz. When viewing the graphs, the reader will simply have to take into account that the resonance behavior at 2 kHz appears to be atypical for this speaker, and should largely be ignored. Also it's not a result of the frame, and should not be attributed to the frame.

I have included a picture of the speaker with the frame attached, as well as an animated gif that switches back and forth between Spin summaries with and without the frame.

The most obvious on-axis frequency response differences made by the frame are a reduction of energy from 950 Hz to 2900 Hz (including the problematic peak at 1100 Hz), and an increase of energy below 950 Hz that gets smaller and smaller until it vanishes around 200 Hz. Both of these are welcome changes that improve the perceived balance of the speaker. We attribute the increased energy in the lower midrange to the effective widening of the baffle.

Interestingly, the DI for the speaker with frames (aka wings) shows an extremely consistent response from 500 Hz up to 10 kHz. The merits of that type of response can be argued, but it's interesting that it happened here with no specific intent to obtain that result. I'll include follow-up posts with dispersion graphs.


Sony_SS_CS5_Front_Frames.jpg

Sony_SS_CS5_2nd_Unit_Stock_vs_Frame.gif
 
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BenB

BenB

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I have created an animated gif which switches between normalized horizontal dispersion measurements taken from unit 1 without the frame, and unit 2 with the frame. There's a clear abnormality of unit 2 that shows up just under 2 kHz on these plots, which should be ignored when considering the impact of the frame.

Changes that can be attributed to the frame include a decrease in dispersion in the 500 Hz to 900 Hz region, due to the widened baffle effect. There's also a very high level of consistency shown in the 6, 9, and 12 dB contours from 500 Hz to 8 kHz (except for the 2 kHz resonance). The 3 dB contour shows some narrowing in the 4-5 kHz range that is apparent with or without the frame. Through the midrange and most of the treble (except for the top octave), this CS5 with frame should sound remarkably similar across the entire front hemisphere (-90 degrees to +90 degrees). Admittedly, the stock speaker is not bad in this regard, but the frame takes it to another level. I think the framed speaker should make for a nice center channel in a low budget home theater (if paired with a decent sub), that would provide nicely balanced audio in every seat.

One interesting observation is that the typical directivity mismatch going from a 5.25" woofer to a 1" tweeter is largely missing in the plots (with Frame). Perhaps the narrowing at the top of the woofer range is masked by the resonance. Still, there is a crossover right in the middle of that band of consistency from 500 Hz to 8 kHz. It's worth considering how this result was achieved, considering the "waveguide" on the tweeter is extremely shallow (probably more decorative than anything... sort of like that super tweeter.)

Sony_SS_CS5_1st_unit_stock_vs_2nd_unit_frame_normHorizontal.gif
 
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BenB

BenB

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I generated yet another animated gif to compare linearity. Again I am comparing unit 1 without the frame to unit 2 with the frame. Standard warnings about the 2 kHz resonance apply.

The stock unit shows exemplary response that's pretty much +/- 3 dB from 80 Hz to 16 kHz. That's pretty impressive for a speaker that goes on sale for $80 a pair (I don't know if that will happen anymore with inflation, but you get the idea... it's inexpensive.) It also achieves a score of 6.8 if used with a sub.

The modified unit shows further improvements to the response linearity, which are very nearly +/- 1.5 dB from 80 Hz to 16 kHz! There's a minor dip in the 2.8 kHz region, but from my measurements, the resistor short actually fills that in, so if someone recreates the total modification I developed, that deviation likely goes away. The score with sub also rises to 7.1, which is an increase of 0.3 thanks to the frame.

There is a bigger difference in the scores without the sub, but that appears to be related to a difference in bass extension that favors unit 2. The frame does nothing to increase bass response, and that should not be attributed to the frame.

Overall I think this has been a very interesting experiment that offers some good insight into the dispersion benefits of very large round-overs. It also highlights the importance of compensating for baffle step correctly. The latter can mostly be done using EQ after the fact, while the former can't.

I'd like to send a special thanks to Erin for agreeing to spend his time to take multiple Spin measurements to make this high resolution comparison possible. Thanks, Erin!

Sony_SS_CS5_1st_unit_stock_vs_2nd_unit_frame_Linearity.gif
 

cavedriver

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Hi Ben, nice work! Did your home speakers inspire this experiment? News flash- wide baffle speakers work great! :)
 

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I generated yet another animated gif to compare linearity. Again I am comparing unit 1 without the frame to unit 2 with the frame. Standard warnings about the 2 kHz resonance apply.

The stock unit shows exemplary response that's pretty much +/- 3 dB from 80 Hz to 16 kHz. That's pretty impressive for a speaker that goes on sale for $80 a pair (I don't know if that will happen anymore with inflation, but you get the idea... it's inexpensive.) It also achieves a score of 6.8 if used with a sub.

The modified unit shows further improvements to the response linearity, which are very nearly +/- 1.5 dB from 80 Hz to 16 kHz! There's a minor dip in the 2.8 kHz region, but from my measurements, the resistor short actually fills that in, so if someone recreates the total modification I developed, that deviation likely goes away. The score with sub also rises to 7.1, which is an increase of 0.3 thanks to the frame.

There is a bigger difference in the scores without the sub, but that appears to be related to a difference in bass extension that favors unit 2. The frame does nothing to increase bass response, and that should not be attributed to the frame.

Overall I think this has been a very interesting experiment that offers some good insight into the dispersion benefits of very large round-overs. It also highlights the importance of compensating for baffle step correctly. The latter can mostly be done using EQ after the fact, while the former can't.

I'd like to send a special thanks to Erin for agreeing to spend his time to take multiple Spin measurements to make this high resolution comparison possible. Thanks, Erin!

View attachment 221169
Ben you shared the speakers in your profile picture on PETT, correct? I seem to remember being impressed by your creative use of arrays.
 
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BenB

BenB

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Ben you shared the speakers in your profile picture on PETT, correct? I seem to remember being impressed by your creative use of arrays.
I think someone else created a thread about them on PETT, and I responded a couple of times but received a lot of negativity so I abandoned the thread. Thanks for your kind words.
 
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BenB

BenB

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Hi Ben, nice work! Did your home speakers inspire this experiment? News flash- wide baffle speakers work great! :)
Yes, the large roundovers on my home speakers inspired me to see if they could bring a sonic advantage to a more traditional speaker. I had no way of knowing how perfectly they would address the issues with the CS5s.
 

cavedriver

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I think someone else created a thread about them on PETT, and I responded a couple of times but received a lot of negativity so I abandoned the thread. Thanks for your kind words.
Your speakers sound amazing, you have nothing to be concerned about from PETT, the internet is full of aholes that simply relish the chance to tell another person they are wrong in some way
 

valerianf

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Hi Ben, interesting modification.
Is the PVC anti diffraction frame just an additional enclosure mounted above the speaker existing one?
Do you have a close looking picture of it?
 
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BenB

BenB

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Hi Ben, interesting modification.
Is the PVC anti diffraction frame just an additional enclosure mounted above the speaker existing one?
Do you have a close looking picture of it?
Pretty much everything there is to know about the project (minus Erin's spins) is in this thread:
I think there's pretty good correlation between Erin's measurements and my own... obviously Erin gets way more resolution.
 

valerianf

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@BenB Thank you for the link.
How the idea of placing 2x half pipes on the side of the enclosure came to you?
Anyway, congratulation.
It is conforting my idea to avoid (when possible) buying speakers with 90° angle on the vertical edge of the front facia.
 
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