Try some different cabs
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Would 150 watts be the same loudness, same amp but thru larger speakers?
- Thread starter don21480
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Use your ears taste tone and wallet regardless of science and keep us posted
It's actually possible to rule it out with reasonable confidence if you want the two speakers to have the same curves and be competently designed. There's not a magic supply of efficiency hidden in the five parameters that govern speaker response at low frequencies.
I get everything wrong. Ask my ex wife.
Oh. And OP: never ever under any circumstances use a pedal. Except maybe a chorus. And a compressor. And a light but transparent OD. And possibly a fuzz. But no pedals ever. Bass directly into your vintage SVT.
JeezyMcNuggles
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- Feb 23, 2018
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More speakers, not the sizes for say, but more total speaker area = more sound. Not power, speaker
<The surface area of the speakers is directly proportional to the square of the cone radius.>
This does not seem correct to me.
The surface area of a loudspeaker would be the area of a cone. I don’t know how to copy the formulas into the forum, but if you google area of a cone you will find that the area of a cone is Pi times the radius [of the cone] multiplied by the radius plus the square root of the height [of the cone] squared times the radius squared. This doesn’t account for the dust cap.
Taking the square of the cone radius as you suggested is half the formula for the area of a circle, but you left out Pi. The area of a circle is Pi multiplied by the radius squared. However, the area of a circle is not the same thing as the surface area of a loudspeaker cone, because a circle is not a cone.
To determine how much air a loudspeaker will move compared to another loudspeaker, you can employ what are known as the Thiele-Small parameters.
Thiele/Small parameters - Wikipedia
Vd, which is the Peak Diaphragm Displacement Volume, is the Thiele-Small parameter that determines how much air a loudspeaker will move per sine wave cycle. Peak Displacement Volume is found by multiplying Sd, the projected area of the driver diaphragm (in square metres) [which takes into account the dust cap] by Xmax, the maximum linear peak (or sometimes peak-to-peak) excursion (in mm) of the cone. This tells you how many cubic centimeters of air the loudspeaker will move per sine wave cycle.
So when we compare, for example, the Vd of the Eminence 3015 loudspeaker with the Vd of the 3015LF loudspeaker, we find:
3015 Vd 505cc
3015LF Vd 846cc
The 3015LF moves more air because its maximum linear excursion (Xmax) is 906mm compared to the 3015 whose Xmax is 5.9mm (there is a small difference in the surface area of the two cones).
To get an idea how loud a loudspeaker might play (i.e., SPL, or sound pressure level) you can use the loudspeaker sensitivity rating, i.e., the average output across the usable frequency range when applying 1W and measuring 1m away from the loudspeaker).
It might be hard for the OP to apply these techniques unless he is able to identify just exactly what loudspeakers are in his beautiful Fender bassman cab. Some of the early MI cabs were manufactured prior to when the T/H parameters had come into common use, or before they were published.
Maybe Agedhorse will chime in on this one.
The frontal area is what matters when determining the acoustical output of a piston radiator. But it's even a little bit more subtle than that, because there is a portion of the surround that moves only partially in and out.
For this reason, it's practical to use an effective cone area, which is the area that you'd use to compute the acoustical output as if the speaker were a perfect piston radiator. This is something that can be measured along with the other T/S parameters. For instance, how the resonant frequency changes when you put the driver in different sized boxes will let you compute the frontal area.
In other words, "just gimme the numbers that I need to plug into the formula" is not far from the actual truth. You can look up the cone area parameter (Sd) for any driver that has published values.
Ok, I didn't catch that those were markbass numbers. I would still guess they simply rounded to the nearest integer for both. So the 2x6 may have been rounded up and the 2x8 rounded down. If they were more like 97.6 and 99.4 that would explain the published specs. The rest of my post is unaffected.
And volume of a cone may be slightly more accurate, but in practice, there is not a lot of variance in the depth of similarly sized speakers, and the travel of the cone (ie xmax) is more important anyway.
And volume of a cone may be slightly more accurate, but in practice, there is not a lot of variance in the depth of similarly sized speakers, and the travel of the cone (ie xmax) is more important anyway.
<The frontal area is what matters when determining the acoustical output of a piston radiator.>
Okay, I’ll bite on the hook. Frontal area or Sd, whatever tickles your fancy, is only half the story. Vd, Peak Diaphram Displacement Volume tells all.
According to Eminence, “Understanding Loudspeaker Data”, Sd is the “actual” surface area of the loudspeaker cone. This would partially include the surround. Not merely the frontal area which you are suggesting is more practical to use. Who is using it?
I notice in their actual loudspeaker specifications Eminence uses the "projected" Sd for their Kapalite series. Are you saying Eminence calculates Vd according to the frontal area of their loudspeakers?
PS: looks like some nice HPF's your making.
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Thanks! Looking at the Kappalite 3015 datasheet (first hit on Google) Sd is given as 856 cm^2, and Xmax is given as 0.59 cm. Multiplying these gives 505 cm^3, exactly the value that they give for Vd. So the three figures are related in a simple way.
Just to clarify, I'm just using the published value of Sd, which I assume accounts for everything including the partial motion of the surround. I think the best way to use the published numbers is just to take them at face value, and plug them into the design formulas. At least, that's good enough for us DIY speaker builders.
Pro designers may be considering specs that aren't on the datasheet, or that are based on an agreement with the manufacturer.You're correct that Vd is the best predictor of the maximum acoustical output when comparing different drivers. You can turn this into the "volume acceleration" of the piston by multiplying it by the square of the frequency, and that's directly proportional to the maximum sound pressure at a given distance.
If you ignore the frustrum shape and dust cap the area is indeed proportional to r**2. Pi is the constant of proportionality.
Thanks! Looking at the Kappalite 3015 datasheet (first hit on Google) Sd is given as 856 cm^2, and Xmax is given as 0.59 cm. Multiplying these gives 505 cm^3, exactly the value that they give for Vd. So the three figures are related in a simple way.
Just to clarify, I'm just using the published value of Sd, which I assume accounts for everything including the partial motion of the surround. I think the best way to use the published numbers is just to take them at face value, and plug them into the design formulas. At least, that's good enough for us DIY speaker builders.
You're correct that Vd is the best predictor of the maximum acoustical output when comparing different drivers. You can turn this into the "volume acceleration" of the piston by multiplying it by the square of the frequency, and that's directly proportional to the maximum sound pressure at a given distance.
<You can turn this into the "volume acceleration" of the piston by multiplying it by the square of the frequency, and that's directly proportional to the maximum sound pressure at a given distance.>
Ah, ha! Didn't know that. I always wondered how to do that. Thanks.
Voicing can add perceived, but not measurable difference in loudness. I say you would notice a difference if you were to swap the combo out from a situation where you typically ride the line of the smaller combo's limitations. Maybe technically not much "louder" to the acoustical reasearcher, but perceptively heftier to the player on stage.
Okay, now I see what you mean. With respect to Sparky Mark's comments and your explanation, it went right by me when I first read Sparky's message. Its a good example of seeing something I thought I should be seeing rather than what was actually there, i.e., "directly proportional". I should have left my response on the queue and re-read everything before I put my message up on the forum.
That being said and now that I'm more or less embarrassed, instead of re-inventing the wheel, if the mere T/S parameters are employed instead of pulling something like that out of left field, everyone including me would immediately understand it.
Emphasis mine. Yup. Even Vd is not to be considered in isolation.
A driver with an unimpressive Xmax but high sensitivity, and by that I mean across the whole passband (as opposed to it being just peaky in the upper midrange) including bass if designed to be so, may well be louder than a high-excursion one even in the lows if the comparison is made with the two being fed a low-power signal; in theory, this would hold true up until the former driver runs out of excursion, but in practice the low-Xmax in question is likely to exhibit power compression and yield to the other significantly before that. Still, there may be applications (say a small tube amp -powered stack for practice and small gigs) in which the one with less Vd outperforms the one with most.
Another example: some time ago I was modelling a B&C 15" driver with high Xmax, thermal power handling and sensitivity, and a low enough resonance frequency. Holy Grail, right? Wrong: it also has a very low total Q factor, which makes it bass-shy with most boxes and tunings unless corrective EQ and a lot of power are applied. It could be made to work for bass guitar duties, but it's just poorly suited for bass as-is (whilst being an obvious candidate for a high-power PA top, or a line-array midbass element), its high Vd notwithstanding. More than one Thiele/Small parameter count, always.
With ported cabs "moved air volume" means nothing but moved air volume.
SPL is the derivatin of velocity rather than moved air volume
Xmax means nothing but Xmax
With ported cabs we can trade off low end extension with SPL thus we can "use" a large Xmax for either low end extension XOR highish SPL at low end range.
Beyond frequency range of about 100Hz the Xmax number is increasingly insignificant anyway.
SPL is the derivatin of velocity rather than moved air volume
Xmax means nothing but Xmax
With ported cabs we can trade off low end extension with SPL thus we can "use" a large Xmax for either low end extension XOR highish SPL at low end range.
Beyond frequency range of about 100Hz the Xmax number is increasingly insignificant anyway.
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