Was trying to get an SRV tone today. Dialed up a Vibroverb, set Speaker Impedance to 2.0, etc. Selected on the 1x15 Vibroverb IRs. Wasn't doing it for me. Turned the smoothing up to around 7.5 IIRC and there it was. Mixed in another IR also w/ smoothing at 7.5 and had a blast.