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Driver size vs xmax Question..

Porkchop2

Porkchop2

Aug 20, 2015
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Milwaukee
#1
Just a question.. So, as cone size goes up, could xmax go down to produce a given low frequency at a given volume? Its about displacement right?

Say, we have… just hypothetical…

Dia. Xmax
12" 6mm
15" 4mm
18" 2.5mm

Could they produce the same (for example) 50Hz at 100db at 50 watts… ? I’m just wondering if a larger speaker would need less xmax, since it’s a larger surface moving. Also in that sense, a smaller speaker would need more xmas to compete with a larger speaker, etc..? So for a given frequency at a given volume/SPL its about total displacement?

Just wondering.
 
#2
Porkchop2 said:
Just a question.. So, as cone size goes up, could xmax go down to produce a given low frequency at a given volume? Its about displacement right?

Say, we have… just hypothetical…

Dia. Xmax
12" 6mm
15" 4mm
18" 2.5mm

Could they produce the same (for example) 50Hz at 100db at 50 watts… ? I’m just wondering if a larger speaker would need less xmax, since it’s a larger surface moving. Also in that sense, a smaller speaker would need more xmas to compete with a larger speaker, etc..? So for a given frequency at a given volume/SPL its about total displacement?

Just wondering.
Click to expand...

Makes sense to me but I don't really know.
 
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#3
More or less, assuming equivalent tunings, but sensitivity will generally decrease with increasing Xmax (of course other factors apply as well) so you have to be very careful when making such claims as LF SPL might be the same but the power level required might be much different.
 
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#4
agedhorse said:
More or less, assuming equivalent tunings, but sensitivity will generally decrease with increasing Xmax (of course other factors apply as well) so you have to be very careful when making such claims as LF SPL might be the same but the power level required might be much different.
Click to expand...
Haha, so a smaller high xmax driver may need more power to get the LF SPLs vs a large driver with small xmax?
 
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#5
Porkchop2 said:
Haha, so a smaller high xmax driver may need more power to get the LF SPLs vs a large driver with small xmax?
Click to expand...
No, a smaller Xmax will (generally) get louder for a given power up until the point that you use up all of that Xmax. This is why you generally don't want to use high Xmax drivers in applications where that Xmax can never be used because you (generally) trade off valuable sensitivity.

Wait a minute, I think I mis-read your comment... yes for the example you gave that is correct.
 
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#6
agedhorse said:
No, a smaller Xmax will (generally) get louder for a given power up until the point that you use up all of that Xmax. This is why you generally don't want to use high Xmax drivers in applications where that Xmax can never be used because you (generally) trade off valuable sensitivity.

Wait a minute, I think I mis-read your comment... yes for the example you gave that is correct.
Click to expand...
OK, I think I got it now, and then at a given motor (magnet/coil/etc) adding cone size/diameter/ adds surface thus more displacement this more spl?
 
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#7
Yes, except that for a larger cone displacing a higher air mass, there will be some tradeoff in efficiency unless the motor is made stronger.

There are a lot of variables that interact, nothing happens without affecting something else. That's what makes designing really high performance speaker systems such a challenge.
 
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#13
We're talking about Xmax before Thanksgiving?! Halloween was just last week! The earlier the Xmax discussions, the more sensitive I get, which can lead to high SPLs. ;)

Ok - agedhorse chimed in a couple times, and you heard it straight from the horse's mouth, so some Accountant hobby bassist isn't going to add anything much but agree: in a very general sense, you take driver size and xmax into consideration, along with other variables. But yes, a 10" speaker likely needs more xmax than a 15" speaker to hit a certain low frequency at a certain decible, but might also require more wattage to do so.

That said, its all in the speaker design too. I've owned some 15" guitar speakers that had absolutely zero bass response to them. And I have a cabinet full of 8" speakers that can go real deep - but again, the 8" speakers had larger magnets than the 15's and with a whole lot more xmax!

Besides speakers, you also have to look at the cabinet design/interior volume and port (or shelf or sealed) tuning. There's just so many variables - and that's before you get in to interior lining, cone doping, acoustic coupling, flux capacitors, and line arrays.

:D
 
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#20
Of course the obligatory date for Xmax would be June 2.

Behold, on this day in 1875, a speaker was born in a mangey lab, to Alaxander Graham Bell and his assistant Thomas Watson. While it would take years for the baby reed speaker to develop, he would eventually be visted by three wisemen, Thiel, Small, and @agedhorse who would some hundred years later bring the baby speaker gifts of specification, application, murr, and perhaps most importantly, amplification! What the heck is murr anyway? Baby speaker does not need to, nor want to be worshiped; it only wants to be enjoyed... and offers peace on TB and goodwill towards Bassists. Merry Xmax to all, and to all a loud night!
 
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