Originally Posted by ZAKOH View Post
Russian avtozvuk.com tested the SWR-12D4. There were two important findings. Claimed T/S parameters are very close to measured. Second, THD is very low, with subwoofer reaching 5% THD at much lower frequencies than other subwoofers from the same test (given some fixed voltage I assume).

They got 30.9Hz resonance frequency for the D4 model. The test of 10 inch model also will be online soon.

12 . Alpine SWR-12D4 - avtozvuk.com
Nice. Those findings mirror my experiences with my 12D2s. The lower distortion is quite interesting, particularly as I think the lower distortion should help with system integration, allowing greater bass output without it audibly sounding like it's coming from the rear. A lot of attention needs to be paid to the enclosure (and damping any panels prone to vibration) to take advantage of this though. I'm seriously considering taking replacing my fiberglass enclosure with a properly-reinforced MDF one for this reason.