Low end power requirements as it relates to cabinet design

[basss]

As for how much power you're driving with at 30-50 Hz, a lot less than you think, on average 20dB less than at 80-100 Hz.

I came across this old post by speaker designer Bill Fitzmaurice. I'm assuming it's accurate but wondering what your take is. I'm asking because I've been tinkering around with speaker box designs and noticing that a lot of commercial cabs seem to be tuned pretty high which would give them a nice fat sound in the low mids but reduce power handling and the very low end.

 

[agedhorse]

No, the answer is very much “it depends”.

With a HPF, this is generally more accurate than without, but it also depends on the bass, pickup location, tuning, playing style, etc.

 

[basss]

Can we assume that with a 4-string bass standard tuning no giant bass boost or pedals that this is generally correct? As a commercial cab designer you probably have to design for every possible scenario but I'm wondering for my needs as a guy who just plays a regular old four string if this would hold?

 

[agedhorse]

Can we assume that with a 4-string bass standard tuning no giant bass boost or pedals that this is generally correct? As a commercial cab designer you probably have to design for every possible scenario but I'm wondering for my needs as a guy who just plays a regular old four string if this would hold?

A 4 string w/ standard tuning has plenty of subharmonic content, especially on the neck pickup.

What Bill may have been trying to describe is the ratio of fundamental to harmonics, in which case he is reasonably accurate. Again, a neck pickup will have more of the low fundamentals.

These are reasons why a well chosen HPF within an amp’s design can be so useful.

 

[basss]

Thanks I appreciate you letting me pick your brain. Wouldn't the ratio of fundamental to harmonics dictate how much you are turning up your amp to hear yourself as most of the volume we hear is coming from mids or at least frequencies above 60 hertz or so? So you wouldn't be cranking the amp enough to put a lot of power into the lowest frequencies. again assuming you're not going for massive sub low end sound or obnoxious volumes.

 

[Beatnicht]

I think a better way to look at this is that, by using a HPF to cut out the lowest frequencies, you can crank your amp a lot louder before the speaker farts out or the cone creases. If you need 100db at 800hz to hear yourself well, that super low content could blow apart your rig before you get there.

I'd be curious of the ratio of power required to generate, say, 80db of 30hz vs 80db of 60hz vs 80db of 120hz.

 

[agedhorse]

Thanks I appreciate you letting me pick your brain. Wouldn't the ratio of fundamental to harmonics dictate how much you are turning up your amp to hear yourself as most of the volume we hear is coming from mids or at least frequencies above 60 hertz or so? So you wouldn't be cranking the amp enough to put a lot of power into the lowest frequencies. again assuming you're not going for massive sub low end sound or obnoxious volumes.

The ratio of fundamental to harmonics remains constant regardless of the volume, but as you turn the amp up, all of the signal increases and eventually will run into the low frequecy power handling limit since there are more low frequecies PLUS the power handling of a cabinet decreases as the frequency decreases (below the cabinet's -6dB LF point)

I think a better way to look at this is that, by using a HPF to cut out the lowest frequencies, you can crank your amp a lot louder before the speaker farts out or the cone creases. If you need 100db at 800hz to hear yourself well, that super low content could blow apart your rig before you get there.

I'd be curious of the ratio of power required to generate, say, 80db of 30hz vs 80db of 60hz vs 80db of 120hz.

It depends on the cabinet sensitivity versus frequency, but with most cabinets 30Hz is going to be about 10dB down compared with 60Hz so it would take about 10x the power at 30Hz to generate the same SPL as at 60Hz.

 

[Hoochie Coochie Man]

You could try to contact Mr Fitzmaurice to ask him to clarify what he said. Be prepared to be ignored or insulted in response.