Hi Les,
I'm not saying they will sound bad on kick, just that typical Tuba freq response (at least that I have seen measured NOT on the BFM site) has a dip right at the fundamental freq of many kicks. This is one of the reasons why Mr. Fitzmaurice recommends Titans over Tubas for live music.
I have found the charts on the BFM site to be less peaky than actual measured subs at events. Look at the T48 for example which Leland brought to the recent sub shootout in Tulsa. I think Leland was somewhat surprised. The results were similar to the site but certainly more peaky. He brought a pair so I wouldn't suspect a faulty build.
In multiples peakiness will smooth out anyway, and I don't doubt at all that you can get a very good sounding kick with T36's. The top box will be a big factor too. I have some T48's, and while they are good, I have certainly heard better, abeit considerably more expensive subs. Of course I have no T36 to compare to. One big factor is that there are many options when building the T36, so that is an issue in knowing if we can really compare apples to apples.
What variation of the T36 is Josh looking at? The dual 15" version would be a bass monster, although physically huge.
I presume the T36's value is much like the T48 - a highly efficient sub that gives the end user with a modest budget the ability to get performance comparable to many of the big boys, in some cases better, albeit not the absolute top of the heap. There are minor comprimises in Bill's designs based on using stock Eminence drivers, which of course keeps costs down and makes things generally more DIY friendly. Labs had a custom driver designed, 12Pi uses that driver but adds cooling and other variations on it, Bassmax sure isn't using low power eminence drivers. Not dissing eminence, I have no issue with them, but I'm sure specs could be better with a higher output custom driver specific to the design.
I know the T48 does not perform quite as well as a Danley TH115 in terms of low extension, smoothness, and overall impact, but the difference in sound quality is nowhere near as great as the difference in price. T36 should be a similar story. I really doubt it could hang in there with something like a Bassmaxx Deuce, Lab, 12Pi etc in overall output and in lowest distortion figures but who cares when you can have a fleet of them at a fraction of the price? Most people will benefit more in the extra $$ to invest elsewhere in their rig.
BTW, nicest kick drum I ever heard was on an Adamson line array. Adamson rigs are bloody expensive but I have yet to hear someone complain about their recent stuff.
My 2c. Josh what is your intended use?
Jeff