One more thought re: cbw's observation that his subs are sentitive to movements of 1 inch. That would be a little extreme IME, but his point is taken. Small movements of the source of deep bass can audibly affect the perceived sound, but once again I'd be inclined to attribute this to room interactions (rather than increased group delay) and note that it, too, is not unique to subwoofers.
Marty |
There's an element of "When did you stop beating your wife?" to this discussion. It starts with the presumption of guilt (for subwoofers) and asks for proof of innocence.
I can (and have) set up subs that sound somewhat overdamped - producing a lean sounding tonal balance (to my ear) despite flat on-axis measurements at/around the listening position on my RTA unit. My Rythmik subs allow for adjustable Q and I have backed off the most highly damped setting for just this reason. I have also heard many extended/full range speakers that sound underdamped, bloated and "slow".
The question of properly damped bass isn't unique to subs. As to group delay issues attendent to placement, endless screwing around with varying placement of subs relative to mains leads me to believe that it's a non-issue, but that would have to be qualified for related variables, including:
Crossover frequency and slope. IF these issues are actually audible at higher frequencies (and, as a practical matter, I have my doubts) , a lower crossover frequency and steeper slope would largely determine how audible they are in a given system. It would also allow increasingly greater separation as the crossover point drops and/or the sub's high cut slope is steepened. IOW, generalizations would be misleading.
The relative damping of the subs and mains at/near the x-over point. IME, there is a pretty good chance that the (sealed) sub is more highly damped than the main speaker (if not matched with care) and the qualitative result of this mismatch is hard to predict. Incidentally, this one is -again- not unique to subs. Many a 3 way full range speaker can exhibit problems in the lower crossover region.
and
The sensitivity of a given listener, among others.
Bottom line, it will be VERY difficult to prove inocence (or guilt) using the math cited here, but much easier using your ears.
Just MHO, as usual.
Marty |
I should note that I didn't mean to be dismissive of Bryon's initial observation which (I assume) is paraphrased as:
"If you're gonna fix the room induced FR problems by separating the source of bass from the rest of the spectrum and moving it closer to the wall (in the form of a sub), you're gonna induce time domain issues."
Assuming that this was the original point (and I apologize if I've mischaracterized it), the issue I have lies not in the general idea, but in the use of the terms "slow", "bloated", and "zero sum".
Even if you concede that gains in FR come at the expense of issue in the time domain (and those using even cheap HTRs needn't necessarily concede this as these units generally compensate electrically for the difference in physical distance), that does not mean that these issues:
A: will be perceived as slow and bloated for time domain problems
and/or
B: will audibly cancel each other out (zero sum).
Indeed, I personally find the former orders of magnitude more audibly troubling than the latter. And I also believe that any audible effects in the time domain can be largely mitigated through careful set-up. In sum, I'd say that, in a well set-up subwoofer system, the benefits in FR obliterate any costs in the time domain.
But, as noted, that is me, personally, and I understand that others may reach a different conclusion.
Marty |
My bottom line is that when I optimize my subs for smoothest FR in a co-planar arrangement it sounds no better (or worse) than when the subs are FR optimized for placement 2 1/2 feet behind the mains. It does, however, require significantly more EQ to get to the same place, so I stuck with the flush to the wall sub placement.
I'm pretty confident (can't be 100% sure, though) that no one would characterize the bass that I'm currently producing as either bloated or slow - and I do have room (via the adjustable Q on the Rythmiks) to skinny it down further if it did sound that way to someone.
So, my experience just runs counter to your theory. OTOH, while I'm extremely happy with the character, extention, and integration of the bass I'm getting from my subs, any of you folks might adjudge it differently.
The ol' YMMV.
Marty |
Bryon,
Certainly no need to apologize - particularly since there is a clean chain of logic to your theory. I've just found that, in my experience, varying the listener to sub distance doesn't produce any audible issues TO MY EAR, provided that FR is appropriately EQ'd. Of course, that last bit about MY EAR always requires the YMMV disclaimer.
It is always possible that other listeners are more sensitive to the phenomenon than I am, so my responses should be treated as a single data point in the discussion, and that is the purpose for which they were intended.
Marty |
Cbw,
Good point re: time coherence and co-planar siting, and an interesting test excersize that makes some sense. Never tried it, but - if I get the energy - I will.
I spent well over a year screwing around with my subs daily (during a long early retirement/extended unemployment stretch) which allowed for pretty much unlimited indulgement (other than wife imposed constraints) in such activities. Now that I'm working again, time constraints are a limit, but the idea is appealling and I hope to give it a go at some point. |
"Why do subs sound bloated or slow?"
I think it's hard to optimize a sub set-up by ear. That approach requires more time, work and patience than most people are willing to invest. If more people used the available tools - real time room analysis - their sub set-ups would sound a helluva lot better, on the whole. If you add room correction to the mix, I suspect that the average set-up would be awfully impressive, with little discussion of "bloated" or "slow".
Just MHO based on personal experience.
Marty |
Personally, I'd recommend an RTA unit, preferably with on-board PEq.
Adjust the PEq and phase for flat on-axis FR at and around your usual listening position. There may be some variation as you move the mic, but -in my case- there was little since my room is set up for solo listening and "window" is narrow.
Screw around a bit with the PEq bands (i.e. use them as tone controls) and/or placement - changing one variable at a time - and try to note all correlations between audible results and the shape of the RTA's FR output. If you have control of the sub's Q, adjust that to different settings as well.
Eventually, you'll figure out what the best sound "looks" like on the readout, and you'll be able to re-locate the subs and dial in a close replica of your preferred response very quickly. Tweak from there by ear.
For me, the best SQ is yielded by flat (or flat to +/- 35hz with slighly and gently rising output below) with subwoofer Q set for medium damping. This has been pretty much true, regardless of where the subs have been physically placed.
I find the SQ remarkably consistent (and remarkably good) when using my Rythmiks/NHT and Velo SMS-1 when dialed in with this technique, which basically holds on-axis FR constant. I would, however, be the first to acknowledge that, for other listeners, differences may be more audible.
Marty |
