I've been testing 3M's AB-5100HF and SHF EMI/RFI absorbing sheets. There is some science behind this product as 3M is not a hifi company.
It's available in different sizes, but I've used the 1mm-thick A4 sheets. Quite pricey at around £40-50 per sheet.
The SHF variant has slightly better overall performance, especially below 1Ghz, but the HF does better above 2Ghz and is slightly cheaper.
In the tests below, I didn't notice any difference between HF and SHF, so would just go for the cheaper one, but probably best (and double the price) is to join the two together.
I originally bought some to line the inside of my NUC server (as some audiophiles have recommended in the past), but didn't notice much difference (hard to do A/B tests so can't be certain). I then tried putting a sheet onto DAVE and HMS, and on top of my cable spaghetti, again without noticing much difference.
But then I put some at the back of DAVE and HMS on top of the connectors - and that did seem to give a subtle improvement, with a slightly smoother, less edgy sound.
With a bit more experimentation, and driven by my OCD nature, I felt the following did give subtle improvements (this with HMS placed 2 thick wooden shelves below DAVE on my hifi rack):
* A full A4 sheet under DAVE, a surprisingly tidy fit, with the excess sheet underneath the rear connectors. Note, this may impact the vibration control if you use hard footers.
* Cut sections to cover the connectors of every component.
* Cut sections to cover all of DAVE's top ventilation holes. Safety warning here, although it only marginally increased my DAVE's temperature in my environment. Note that I have an HRS DPX damper plate that already covers the holes on DAVE's LHS, so I only needed a small curved piece for the holes behind the display. The damper plate sounded better than the sheet, and putting the sheet over the damper plate made no difference. Note I always put DAVE into standby overnight, so no risk of overheating when I'm not looking.
* Cut sections across the front controls of HMS. This had the additional benefit of blocking the bright lights when I'm listening in near-darkness.
* A section to loosely cover the top and sides of my fanless NUC server. I would only risk this because my NUC is very cool running. Do not do this on any hot-running component.
When changes are this subtle, I'm fully aware that results can be impacted by Imagination and Expectation Bias.
Nevertheless, every time I tried to remove one of the above, usually from the top of DAVE's ventilation holes or HMS front controls (as these are the most aesthetically impactful), then the OCD part of my brain would force me to put them back again, because the sound got just that tiny bit thinner and edgier.
Sometimes removing one of the sheets seemed to make the sound a bit clearer and more dynamic, so maybe one can overdo this sort of thing, and maybe it's just imagination. Life can be tough being a dedicated audiophile
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