Why do subs sound bloated or slow?

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

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

Marty, I don't think the effect I described can be reduced to room interaction because, as I said in my earlier post, I can achieve the same result by adjusting the delay of the mains relative to the subs without physically moving anything.

Stringreen, sub level is certainly important for proper integration, but turning down the level on a misaligned sub won't solve the problem, it will just make it less noticeable (along with the bass).

Shadorne, I disagree "that you can't perceive accurately what is happening to the bass response except by what it 'masks' in the higher frequencies." If you consider a single frequency around the crossover frequency (say, 80 Hz), it is being played by both the mains and the sub(s). Those outputs will either sum properly, or not, and you can easily hear very small changes in delay. (As an experiment, try playing a constant tone and turning the phase knob on a properly-aligned sub while watching an SPL meter.)

But real signals are the sum of a wide range of frequencies, and the overlap between subs and mains is also across a range of frequencies. Properly aligned, the waveforms will sum together properly, but when misaligned they will smear out the low-frequency information. The effect is plainly audible, and can't be attributed solely to masking.

01-25-11: Martykl
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.

Hi Marty - I regret the title that I chose for this thread for a variety of reasons, including the one you mention. It is was not my intention to imply that subs ALWAYS sound bloated or slow, as I mentioned in a post the same day I started the thread:

In the OP, I wasn't trying to suggest that all subs sound bloated or slow. I was trying to identify some reasons, WHEN subs do sound bloated or slow, WHY that is the case.

The principal reason I identified in the OP is a conclusion that I arrived at after extensive experimentation in my system and others, namely that optimizing frequency response often comes at the expense of optimizing transient response, since efforts to optimize frequency response usually include non-coplanar placement or EQ, both of which disturb the sub's time alignment with the mains, and hence the transient response of the system.

The use of the of the terms "bloated" and "slow" were not intended to be derisive, but rather descriptive. It seems to me that room modes often result in non-flat frequency response that can be described as "bloated," and that time misaligned subs often sound out of sync with the mains, which can be described as "slow." Having said that, I quite agree that bloated or slow bass is not a problem unique to systems with subs.

But what IS unique to systems with subs, IMO, is the "zero sum game" that results from scenarios in which efforts to optimize the system's frequency response disturb the system's transient response, and vice versa. The reason this is unique to systems with subs is that, for systems without subs, the time alignment of the system is determined almost entirely by the manufacturer, not the end user, for the simple reason that the woofers are physically attached to the same cabinet as the other drivers. For systems with subs, frequency response and transient response (for bass) are independently controllable parameters. Hence systems with subs have unique challenges, including, IME, the challenge of optimizing both frequency response and transient response. That was the central idea in the OP, and the idea I've been advancing throughout the thread.

Part of the confusion here might have been avoided if A'gon didn't limit my initial post to a little over 100 words. I have no idea why that is done, and I have seen many other threads in which the OP was far more than 100 words.

FWIW, I use a sub in my 2 channel system, and it sounds neither "bloated" nor "slow." But it took me literally years of periodic experimentation to arrive at that point. The reason, I believe, is the "zero sum game" I've been trying to describe.

Bryon