Why do bigger subwoofers sound different?

[574stereo]

I think you will find +20dB at 20hz to be out of the ordinary.

GD in small sealed subwoofers can be kept at inaudible levels even with a HPF.

Discussions of the audibility of phase shift are a grey area still with inconclusive conclusions from the studies that have been carried out so far. Anecdotally and subjectively it's very audible in my experience.

Regardless of the audibility of phase shift in itself, the group delay from a HPF can still be having an affect around the crossover point making it hard to integrate around the crossover point.

 

[sigbergaudio]

Discussions of the audibility of phase shift are a grey area still with inconclusive conclusions from the studies that have been carried out so far. Anecdotally and subjectively it's very audible in my experience.

Regardless of the audibility of phase shift in itself, the group delay from a HPF can still be having an affect around the crossover point making it hard to integrate around the crossover point.

Phase shift say between a midrange and a tweeter can be audible. Phase shift below 100hz I think you will find is not a very grey area, and I would be interested to see you blind test that on a subwoofer where the actual frequency response is even.

But let me not just claim things, here's a measurement of the group delay of our 10D: Below 20ms from 30hz and above, and below 40ms even at 20hz. This is not audible or problematic in any way.

 

[ppataki]

Regardless of the audibility of phase shift in itself, the group delay from a HPF can still be having an affect around the crossover point making it hard to integrate around the crossover point.

You could also use linear phase HPF (and LPF) - that will have zero impact on the phase and on the GD
That's what I am doing - see some measurements here showing the benefits

 

[Blockader]

No this is incorrect, sorry! Go build and measure some subwoofers and you'll see this to be the case. Corrective EQ to extend FR at the low end is not minimum phase...

Why would that be the case? It's true that for in-room responses, some room modes are irreversible, hence non-minimum phase. However, I can't see why equalizing the on-axis response of a subwoofer would show non-minimum phase behavior.

Applying equalization to a subwoofer with a minimum phase filter at low frequencies enhance its group delay. However, the characteristics of a room may prevent this improvement in group delay from being realized. The interaction between the subwoofer's performance and the room's acoustics introduces a separate variable to consider.

 

[574stereo]

Agreed on that front, some rooms can somewhat negate worrying about group delay in a speaker's performance if the low frequencies are especially out of kilter...

 

[574stereo]

You could also use linear phase HPF (and LPF) - that will have zero impact on the phase and on the GD
That's what I am doing - see some measurements here showing the benefits

Linear phase filters have their own set of difficulties... latency, pre-ring... A subwoofer has to be in time with your mains...

 

[ppataki]

Linear phase filters have their own set of difficulties... latency, pre-ring... A subwoofer has to be in time with your mains...

That's a non-issue, you can time align them anyway
Pre-echo is not audible if the filter is implemented properly

 

[Waxx]

There is a very basic explenation for that, a bigger woofer needs less movement of the cone as a smaller one to move the same ammount of air (and so the same frequency and volume). So it's much less stressed with less distortion as result.

The different rooms, amps and other factors will off course also play a role, but this is surely an important one, and one that is known. It's not that a small woofer can do low bass, but the volume possible will be lower, and the distortion will be higher than with a bigger driver in general, that's just basic physics.

 

[Blockader]

There is a very basic explenation for that, a bigger woofer needs less movement of the cone as a smaller one to move the same ammount of air (and so the same frequency and volume). So it's much less stressed with less distortion as result.

The different rooms, amps and other factors will off course also play a role, but this is surely an important one, and one that is known. It's not that a small woofer can do low bass, but the volume possible will be lower, and the distortion will be higher than with a bigger driver in general, that's just basic physics.

Hearing distortion in bass frequencies is incredibly difficult. In typical music, the bass is louder than both the mids and treble.(usually +30db compared to high treble)
The Fletcher-Munson curves, which map out how we perceive loudness at different frequencies, explain why bass fundamentals are so effective at hiding distortion. Basically loud bass fundamentals can mask their low order distortion products very well. (look: Auditory Masking) Toole touches this topic somewhere in his book.

People can barely hear %3 sub bass distortion around 85db. Besides that, high order distortion has all the reasons to make a sub bass fundamental sound more impactful than it really are.

 

[thewas]

No this is incorrect, sorry! Go build and measure some subwoofers and you'll see this to be the case. Corrective EQ to extend FR at the low end is not minimum phase...

Why shouldn't such an IIR filter be mininum phase?

 

[dasdoing]

Linear phase filters have their own set of difficulties... latency, pre-ring... A subwoofer has to be in time with your mains...

in a linear phase crossover the pre-rining will cancel out.
that works perfectly in the (time aligned) sweet spot but outside it will become audible the greater the time difference. A simple solution to this is not to use brick wall filters. the useable roll-offs are still much steeper than in a traditional crossover