Do you think you need a subwoofer?

Now that I read the mijos  post I can see that the frequency is at 350hz ( I can't find it ). So, if it's at 350hz then the HP is desired to has down there but in the other side you are really listening at near field, even that the IMD is there and you can clean up. Maybe Genelec can help you to choose Genelec subs at your specific needs.

R.

Dear @mke246  : I think that you are living a great first hand experiences listening to those very old recordings as that of Fats Waller. Congratulations.

R.

Most collectors playing 78s are not going to hear the full potential of the records because their equipment is the equivalent of playing an LP on a Crosley. Bad stylus fit, bad EQ, suboptimal processing capabilities, or simply not playing an archival-quality copy. 78s will never sound like an LP-era recording, but you can make them sound like the best reissue CDs out there or better with the right equpment.

My 8351Bs are on stands on my large standing desk--sort of by necessity. They measure well in GLM software, and my room is treated with GIK panels. I mostly remaster on Sennheiser 800S headphones because I have a young child who’s usually sleeping when I have my ’free time’. I admit I haven’t put much thought into the concept of crossover frequency. The tuba and string bass on old jazz records sounds nice and tight, but I listen mostly to 78s probably limits my scope of reference when I listen to anything more modern. I’ll be researching subs and will probably pick up a pair when the time is right.

Genelec recommends 7370A subwoofers (around $4k each) for the 8351B but also has said in the past that 7360As (around $2.5k each) are fine if your room is on the smaller side and you listen at lower-to-moderate SPLs, which would fit my situation. Most people who implement subs with 8351Bs seem to leave the crossover frequency in the neighborhood of the default 85Hz. Still a bit on the fence--most of my music is pretty light on the sub-bass and that's a hefty investment for something I'll only get big benefits from on infrequent occasion. The 8351Bs are pretty strong at reproducing the bass on 98% of what I listen to.

@mke246 Again it is not just the added bass performance you are looking for. It is improving the performance of your 8351Bs. 85 Hz is OK, but I would go higher at 100 Hz. Just removing turntable and record rumble from the 8351Bs will make a significant improvement.

@rauliruegas I got that crossover frequency directly from Genelec's literature. 

I use Channel D's Pure Vinyl Program for RIAA correction. It also has every EQ curve known to man. My phono stage is digitized, the signal is converted to a USB channel, sent to the computer that applies the chosen EQ curve and sends it back to the Lynx Hilo on a different USB channel. I can also record it to the hard drive in the process and do a lot of fun things like apply a pop and click filter that is very effective. 

I love Fats Waller songs but I prefer to listen to Art Tatum play.