Acme B-112 vs Barefaced Big Baby

#61
Doner Designs said:
I always like seeing posts and pics where others have a dozen basses or amps....makes me feel a bit less gluttonous. :)

I was more thinking about putting the 30 and 40hz in (using the low end EQ to offset cab rolloff), but wiser fellows seem to be telling me that that is the wrong goal. :)
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Prolly sounds cool if your cabs can handle it. It's kryptonite for mine :-)
 
#62
Can anyone explain the point of these cabs which have 18 inch main drivers but are only rated down to 62 and 46hz, respectively?

Is this just an example of the fact you cant really compare cab specs across brands? Seems like the drawbacks of using an 18 would outweigh the benefits unless you are targeting the 30's for low end.

Thunderchild 118

Hathor 1855
 
#67
Doner Designs said:
Can anyone explain the point of these cabs which have 18 inch main drivers but are only rated down to 62 and 46hz, respectively?

Is this just an example of the fact you cant really compare cab specs across brands? Seems like the drawbacks of using an 18 would outweigh the benefits unless you are targeting the 30's for low end.

Thunderchild 118

Hathor 1855
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Driver size only tells you the size of the driver. Every driver is different, and every cab will (intentionally or not) emphasize/cut various frequencies. It's old school thought that bigger divers push bigger lows. You can't tell me how your bass sounds by just telling me what strings you have.
 
#68
monsterthompson said:
Driver size only tells you the size of the driver. Every driver is different, and every cab will (intentionally or not) emphasize/cut various frequencies. It's old school thought that bigger divers push bigger lows. You can't tell me how your bass sounds by just telling me what strings you have.
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Right but I think it's safe to say it's going to take much less power to get that low end from a big cab with big drivers, than a smaller cab with smaller drivers. With limited wattage (say the average tube amp) a bigger, higher sensitivity driver in a big cab seems a better option (for me anyway) than a smaller cab that takes a billion watts to get the same level of output.

Anyway, I think I'm contributing to the derailment of this thread so I'll stop...
 
#69
BassOnTheSide said:
Right but I think it's safe to say it's going to take much less power to get that low end from a big cab with big drivers, than a smaller cab with smaller drivers. With limited wattage (say the average tube amp) a bigger, higher sensitivity driver in a big cab seems a better option (for me anyway) than a smaller cab that takes a billion watts to get the same level of output.

Anyway, I think I'm contributing to the derailment of this thread so I'll stop...
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Not a terrible derail. All else equal, the wattage required to produce low frequencies is greater than the wattage required to get higher frequencies at the same volume level, hence why Acme cabs are "inefficient." They produce big lows at the expense of getting loud. The size of the driver also tells you zero about the excursion it is capable, giving you only an "area" vs. providing a "displacement volume" which is what really matters. It is why comparing the BB2 12" driver to other 12" drivers doesn't give you a complete picture. The 12" Barefaced uses has a higher excursion, making it capable of greater displacement than many other 12" woofers.

Bigger woofers also get into questions of the mass and inertia involved in making the coil work, which gets into issues of transients and attack feel. It is a can of worms for the average punter, and makes a "driver size" comparison difficult to do knowing only the cone diameter. We haven't even gotten into the off-axis performance of various driver sizes/shapes/colors/flavors :)
 
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#70
Doner Designs said:
Can anyone explain the point of these cabs which have 18 inch main drivers but are only rated down to 62 and 46hz, respectively?

Is this just an example of the fact you cant really compare cab specs across brands? Seems like the drawbacks of using an 18 would outweigh the benefits unless you are targeting the 30's for low end.

Thunderchild 118

Hathor 1855
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It's just a matter of what yardstick I chose to measure with.

Imo the Thunderchild 118 works quite well with low-B-tuning, so I tell you how far down it is at the 62 Hz first overtone of low-B. It's not bad with low F# either, but we might start getting into excursion issues at high power, so I don't really recommend it for low F#.

Imo the Hathor 1855 works well with low-F# tuning, so I tell you how far down it is at the 46 Hz first overtone of low F#.

I could have claimed much deeper extension for both cabs if I had wanted to make them look impressive "on paper", especially since both have user-adjustable port tuning frequencies. Neither of my 18's have as big a bottom end as I would expect from the Acme 112 - that thing's a beast.

As far as targeting the 30's for low end, I once designed and built a prototype cab that was -3 dB at 34 Hz. It had a single very expensive 18" woofer with an x-max (one-way linear excursion) of 22 mm(!), net internal volume of 5.7 cubic feet, and 94 dB efficiency. The laws of physics dictate ballpark 5.7 cubic feet internal volume for a 94 dB vented box that is -3 dB at 34 Hz. Acme, Mike Arnopol, Greenboy, and Roger Baer measure with the same conservative yardstick that I use. That doesn't make our cabs any better or any worse than others who use a different yardstick. I think Ampeg uses the conservative yardstick as well.

Note that the limited top-end extension and beaming of an 18" woofer can be side-stepped by adding a midrange. And note that there are high-end 18" woofers available today that have very powerful motors, and so they have much better impact than yesteryear's 18's.
 
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#77
monsterthompson said:
Sensitivity is measured by driving a speaker with one watt and measuring the loudness in decibels at one meter. The only requirement is that a speaker size be greater than zero, otherwise it wouldn't generate sound.
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Please make a choice of the weopon you try to use, the materials the weopon can be build off means nothing to punch of the finished "weapon". What cab paramters would you choose?
I have no interest to fight versus brilliant specs without meaning, allthough I could easily win the game in this field
 
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#78
All else being equal, broadband woofer efficiency goes up as cone area increases.

All else being equal, broadband woofer efficiency goes down as cone weight increases (which tends to happen as cone area increases).

All else being equal, broadband woofer efficiency goes up as the motor strength increases, but the low-end -3 dB point moves higher, and the low end sounds "leaner".

All else being equal, broadband efficiency goes up as the woofer's free-air resonant frequency goes up, but again we lose low-end extension.

So, like everything else in speaker design, efficiency is a juggling of tradeoffs. And the rear-world picture is more far complicated than I've portrayed it here; for starters, changing one parameter inevitably changes others, so "all else" is never equal.
 
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#79
DukeLeJeune said:
All else being equal, broadband woofer efficiency goes up as cone area increases.

All else being equal, broadband woofer efficiency goes down as cone weight increases (which tends to happen as cone area increases).

All else being equal, broadband woofer efficiency goes up as the motor strength increases, but the low-end -3 dB point moves higher, and the low end sounds "leaner".

All else being equal, low end efficiency goes up as the woofer's free-air resonant frequency goes up, but again we lose low-end extension.

So, like everything else in speaker design, efficiency is a juggling of tradeoffs. And the rear-world picture is more far complicated than I've portrayed it here; for starters, changing one parameter inevitably changes others, so "all else" is never equal.
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This is what I was "driving" at. The unit of measurement for sensitivity has three components:
1 - Watts
2 - Decibels
3 - Distance (of the measurement point from the sound source, not of anything else)

Efficiency is related to sensitivity, as more efficient drivers will translate the same watt into more decibels. The leap of tying driver size to efficiency (and thus sensitivity) has some relationships, as you pointed out, but they are generalizations and require assumptions like "all else equal" which can't be considered as constants in the real world. Hence my willingness to concede "loosely related" but still leaning toward unrelated, as an argument for a driver size/sensitivity relationship has too many other considerations and variables to create a formula or rule. You can't tell me how fast a car will be based on only the tire size.
 
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#80
monsterthompson said:
This is what I was "driving" at. The unit of measurement for sensitivity has three components:
1 - Watts
2 - Decibels
3 - Distance (of the measurement point from the sound source, not of anything else)

Efficiency is related to sensitivity, as more efficient drivers will translate the same watt into more decibels. The leap of tying driver size to efficiency (and thus sensitivity) has some relationships, as you pointed out, but they are generalizations and require assumptions like "all else equal" which can't be considered as constants in the real world. Hence my willingness to concede "loosely related" but still leaning toward unrelated, as an argument for a driver size/sensitivity relationship has too many other considerations and variables to create a formula or rule. You can't tell me how fast a car will be based on only the tire size.
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SPL of driver loaded at infinite baffle is often meaured at 1kHz
It's also possibble to state an "sweep" average of 100..1kHz to provide an more meaningful SPL, cause the application meant is totally unknown by the manufacurer.
It all means nothing as long as the application (the cab the driver is loaded) is unknown.
It's not possible to compare a "nude" driver to a cab!

IME the reference efficience expressed as % number helps to roughly estimate "loudness" of a given driver but hey, TB discussions look very diffrent in this regard.
 
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