“Real” bass vs. “Boom” — how do you know which?

"As you might know the same speakers driven by a different amp can affect the bass like you wouldn't believe."

Yes indeed. for the larger OHMs in particular, that increasingly means a higher current, higher efficiency amp that mostly doubles rated power output from 8 to 4 and even 2 ohms.

So in summary, here is the recipe for the larger OHMs in order of importance IMHO:

1) speaks fit/tuned to room
2) high current amp
3) good quality source and pre-amp

Wow,

Great stash of suggestions, folks. I'm on it. Actually I'm out sick today with a stomach flu (blech) so maybe I'll have a little time to mess with this today (if I can stand up, that is....)
Thanks!

Two possibilities -- listen or measure.

Listen; you must already have recordings with reasonable bass information (<200 Hz). Select a few with what you believe to be the cleanest bass (electric or acoustic bass, low end piano or organ, synthesizer, etc.) and listen at a high/average level. Pay attention to how well different instruments are defined and whether or not there is a dominant tone, regardless of instrument. The "boom" that some have mentioned will often occur around 60 Hz and jump out at you. I'm not a fan of using drum recordings since the bass drum will have one note pitch so will not offer the differentiation I look for.

Measure; while the RS meter may not be a precision instrument, you are looking for differences, not absolute values, so it should work fine. Mount the meter on a tri-pod at your listening position and make notes of the values shown for a test disc such as the bass response segment from one of the Stereophile discs. First set loudness to your normal listening level, then note the dB for the 1K tone. Next write down the dB level for each frequency from 40 to 200 Hz. Any peak tones will be obvious. The goal is to achieve the smoothest bass response possible - the least total dB variation from the 1K baseline when adding up all base frequency measurements. I've used this method to fine tune speaker position with good success.

All these suggestions and no one has yet pointed out the only true way you can know - you must be intimately familiar with the real thing (i.e. acoustic instruments in a real space). This takes some time and effort. You should attend some classical and unamplified jazz concerts and listen to the low end - how it blooms into the recording space, its natural timbres, etc. Once you have done this enough, you can more easily tell what is "boom" and what is natural. Taking studio recordings and other test discs and/or making measurements simply cannot determine this. Sorry, this is not the easy answer you may be looking for but it IS the only real way to accomplish this(and it applies to the entire frequency spectrum too, not just the bass).

I'm not a fan of using drum recordings since the bass drum will have one note pitch so will not offer the differentiation I look for.

Good point (although drum sounds are much more complex in their sound compared to typical instruments that follow harmonic rules). Drums do let you check the "transient" response - as this can be just as much of a problem in the bass as frequency response (although the two are tightly related because a high Q resonance of an underdamped speaker will create a broad frequency response hump as well as additional cycles of the woofer after the music has stopped, and although this broad hump can look mild when viewed with the eye it is actually very easily audible)

The key with drums is to listen for their own timbre (after the hit) and then the room echo (from the recording location) as well as your own listening room. If you can't hear this clearly (you don't hear the space around the drums) then you may have masking from an underdamped bass response... either from your speaklers or ringing from room modes.

Masking works upwards: Basically low frequencies wipe out your ability to hear higher frequencies - so if they last too long (resonance) or if they are overly loud then you'll miss stuff off the recording - simply put you won't hear it.

This is why warm resonant sound can pretty much fix a bad recording...it just lathers everything in resonance and hides imperfections that you might normally notice.