Why do subs sound bloated or slow?

It is much cheaper to make a subwoofer that plays bloated and slow - so that is mostly what you find.

It is extremely expensive to make a subwoofer with low distortion, significant SPL output below 30 Hz and a good transient response (low group delay). It requires a very large sealed box with a very expensive high quality large woofer.

Transient response is not irrelevant. Many subs have group delays of up to or more than 1 cycle. Of course this is audible. The other factor intrinsically tied to transient response is the resonance.

An underdamped design will keep oscillating after the signal has stopped - this is adding sound after the sound has in fact stopped. Most subs are designed that way. No wonder it sounds bloated.

A good design will be overdamped or critically damped. These will not sound bloated.

Spatial issues are not that important in the LF as we are talking only a few milliseconds with waveforms that are 50 milliseconds long at 20 Hz. A PEQ will delay only a few milliseconds also so no big deal.

Group delay can be a lot more than a few milliseconds and can be a problem as it can add delays that are equivalent to moving your sub 30 feet....

Transient response is important but spatial positioning of a sub is not the big deal you make it out to be - as long as sub and speakers are within a few feet of being the same distance to the listener then no big deal. Of course this argument only holds for very low frequencies and a mere 2 milliseconds can be important at 1 KHz

Cbw723,

You need to investigate further. If you can hear the difference caused by a time delay of 1 inch (roughly 0.1 msec) in a subwoofer then there is something seriously wrong. 1 inch is less than the distance between your ears - it is of the order of a very slight movement of your head.

Do you have a tool to ensure your head is within 1 inch of teh optimal positioning while listening?

Quite simply the highest frequencies of a subwoofer are normally around 100 Hz (max) before there is a steep roll off and this corresponds to a wavelength of around 10 feet.

Your observation suggests that your subwoofer is putting out significant sound at above 1 KHz - for example at 3 Khz a 1 inch movement can make a large difference on a pure tone (although it would very unlikely to be audible with music).

Scientists seem to agree that 1 to 2 milliseconds is the threshold of hearing a delay in sound - and this will occur at upper midrange frequencies and not at subwoofer frequencies which are omnidirectional to the ear/brain.

In essence, what you report suggests something else is going on.

Certainly group delay and frequency response are intertwined.

I suspect that "masking" is what makes the effects audible. What I mean is that you can't perceive accurately what is happening to the bass response except by what it "masks" in the higher frequencies.

If a 20 Hz signal suffers a group delay of say 30 msecs - what happens to the harmonic distortion associated with that sound...are they also delayed by 30 msecs?

If the harmonic distortion is significant and delayed by 30 msecs then you may have a very audible 80 Hz harmonic that is audibly delayed by 30 feet. I cannot help but suspect that this harmonic will make the bass sound "slow", "bloated" or "muddy" by masking higher frequencies.

In essence, just consider the entire harmonic distortion from low frequencies (below 50 Hz) all delayed by the group delay - this smears out the bass response and masks transients to the ear.

I agree that a hump in the frequency response will ALSO cause masking by emphasizing certain frequencies by as much as 5 dB more than they should be and making the balance of sound such that you do not properly hear the higher frequencies (sound of the high frequency hit from the stick hitting the drum head).

Sound Engineers know that they can change the "speed" or attack of bass notes by altering the higher frequencies - emphasis is added for greater attack and de-emphasis to make the sound more laid back - in my opinion they are playing with teh amount of bass "masking" when they do this