How best to eliminate LP warps

but they’re only for sale in Japan, and only at 100V

@drbond  They've been available in the UK for ages...

Dear jw, Your assumptions are not quite accurate. I normally do not fuss over warped LPs, as I observe them very infrequently in LPs in my collection of 2500 or more LPs, but I would not dare to guess what fraction of that total is warped. However, in the last 2-3 weeks, I observed on separate occasions that two of the LPs I selected for play on those particular days (to be clearer, one LP per listening session) were warped "severely". Especially affecting the outermost one or two tracks on each. Since I only noticed the warps when the LPs were already spinning, I was also able to observe that both LPs sounded great, were tracked well by two different high compliance cartridges (B&O MMC20CL and Ortofon MC2000 mounted in Dynavector DV505 and Triplanar, respectively), had very quiet surfaces, no ticks or pops, and great music. Because of the latter good qualities, I am loathe to discard the LPs. Normally if an LP is as warped as these two, I discard them; they usually have some other defect that justifies trashing. So I started wondering what are the latest and most cost effective methods for flattening; I would not spend the $3000 cost of the Furutech, which I already knew about, because the problem is so unusual in my personal experience. I would not make the general statement that I don’t have a problem playing warped LPs, only that these two LPs play OK.

@optimize @jw944ts 

Mistracking and wow are only part of the problem. If you want to get the most from your vinyl, you have to set all TT parameters pretty accurately. That includes stylus azimuth.

A dished LP will significantly mess up your azimuth adjustment consistently for the whole record. A warped LP will severely mess up your azimuth every 1.8 seconds.

My DIY air bearing tonearm / Koetsu setup is sensitive to small azimuth changes - 6 minutes of arc from perpendicular is clearly audible. The effect manifests itself as a loss of beauty tending towards grating coarseness. It's not better when it comes and goes.

A 1 mm dish over the 150mm from edge to spindle is 1/150 of a radian, or 23 minutes of arc. Warp similar. 

My reflex clamp reduces most imperfections to nil, which works for me. YMMV

By 'most imperfections' I meant dishes and warps.

Terry, you wrote, "My DIY air bearing tonearm / Koetsu setup is sensitive to small azimuth changes - 6 minutes of arc from perpendicular is clearly audible".  That's remarkable because it infers that your Koetsu is perfectly constructed internally.  If perfect 90 degrees of azimuth yields audibly superior results even in comparison to a few minutes of arc off 90 degrees, then that would be the case.  There is a good case to be made for setting azimuth at 90 degrees notwithstanding electrical measurements of the results, but it usually means a slight compromise in crosstalk perfection, because most cartridges are not perfectly constructed. But your general point that warps throw off azimuth as well as speed is well taken.