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Examples of edge coating and response from clients having had their drivers edge coated
SBA-MR13P   SEAS EXOTIC   SEAS W12CY003

SBA SB17CRC      SBA MR16P-4/8

Copyright 2019 © Troels Gravesen

Linearising the frequency response of drivers can have a profound impact on sound as has been described in my W12CY003 file. Some drivers have a severe and consistent performance like the W12CY003 making an edge coating necessary - and some drivers don't. The variation in production may produce two identical drivers not so identical after all and the question is whether we should do edge coating or not. The thing is that we would need a large number of drivers to find out whether an edge coating is desirable or not. And what happens to a driver that doesn't have the problem - and yet gets an edge coating? At this point in time I can't tell. I need more experience. I recently did a 6" PP cone driver with only a minor problem and the edge coating did indeed linearise the frequency response, but sonically the result was dubious.
Below you'll find some examples of drivers having positive results from edge coating.

By adding a proper amount of glue with proper elasticity and resilience and in the right place on the inner side of the surround, the energy coming from the cone can better be absorbed and the result is a more linear frequency response - and hopefully, more fidelity. The deviation from linear frequency response is really not the key issue here, rather the narrow phase shift.
The source of material and application technique shall not be revealed, so please do not ask.


SBAcoustics MR13P midrange driver
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Z...../BE/SBA MR13P-8:
I installed the modified mid-range drivers after playing in for about 50 hours. It does sound significantly better, it is much smoother and clearer after the edge coating and the distortion I complained about initially is completely gone. The mid-high integration is exceptional, the highs are clear in the most natural way.


W...../DE/MR13P-4:


First impressions from hearing:
- Voice appear a little bit farther away.
- The spatial location of musicians is improved
Same good sound: very smooth & natural. This is why I like these speakers so much. BTW as you can see tweeter is the 29BACC. Great choice for 200€.

Hi Troels,
Just final feedback on the edge coating. Series coil was finally lowered by ~13% giving roughly 1dB more in the critical midrange.
Works simply perfect. Again thank you very much!
Best regards W.




 


Quite a matched pair.


B......./DE/EXOTIC-W8
The Drivers arrived today, after work I installed them and listened.
First the optic: Amazing. If I would not know where to look I would think they would be straight out of the factory.
The sound: It sounds clearer. Some distortion is gone. I expected it with voices, but it is also very clear with instruments that they sound “less recorded”, more natural. So I am very happy with the action. Before it I was almost dropping the driver and looking for something else.

 


 

 


SEAS W12CY003 midbass
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Typical result of edge coating. Red = before, green = after.


Some samples are better than others after coating.


Eight samples as-is. As can be seen quite some variation in performance.


Eight samples as above, but after edge coating.


SBAcoustics SB17CRC35-4
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SB17CRC35-4, before (red) and after (green).



SBAcoustics MR16P-8 and -4 midrange driver


MR16P-8 drivers. Right: After application of coating material.

Have had a number of MR16P drivers, both 4 Ohms and 8 Ohms and they're not too bad as-is. However, most have a noticeable swing around 1.2-1.3 kHz and I'd still say they benefit from edge-coating.





 


Above the 4 Ohms version, unit I and II, before and after edge coating.
The 4 Ohm version initially did better than the 8 Ohm version, but certainly smooth in upper-mid after edge coating.


MR16P after drying.

 

I had another pair of MR16P-4 drivers and here are the results:


Sample III and IV as-is on a 100 x 120 cm baffle. Quite some disturbance around 1-1.5 kHz.


Sample III and IV after  edger coating.


T...../DK/SBA MR16P-4 (sample I and II):

Thanks for edge-coating of my SB Acoustic Satori MR16-4 mid-range drivers. 
With edge-coating the sound stage seem a little further back with more depth of image and less attached to the speakers. Acoustic music seem  more natural, homogeneous and relaxed, some might miss a little sparkle or edge to the music, finding it some kind of interesting. Further listening will tell you this more real and  you might have been captivated and seduced by a reproduction imprinted with an unwanted artifact. The case is that we get used to distortion and  and a period of rehabilitation is required. To my experience mid-range and tweeter integration seems better by having a more seamless transition. It's like the mid-range has less sonic signature letting the drivers sound more like one. Before edge-coating female voices, when playing music loud, had a tendency to get a little annoying (I have heard worse) The tendency of being hard to the ear could sometimes be followed by the impression of  harmonics becoming detached from the keynote. With edge-coating I can´t make this phenomena to appear. I find spatial information to have improved, the sonic signature of the recording venue is easier to hear. Instruments and singers are better separated and positioning is more stable, less prone to move.
Being a DIY speakerbuilder you can spend 100 Euros in many ways, edge coating can definitely be worth the spending.
Best regards