Magico QSub-18 and QSub-15 Subwoofers Preview

Pyrrho

Pyrrho

Audioholic Ninja
About that claim of 136 dB SPL at 20 Hz...

Beranek's Acoustics in equation 4.17 gives a formula for the acoustic pressure of radiation from a piston on an infinite baffle into half-space. This formula can be expressed in a form such that it gives the on-axis RMS acoustic pressure as a function of frequency, surface area of the piston, peak displacement and distance. That formula can be expressed as:

p[SUB]RMS[/SUB] = sqrt(2) * pi * f[SUP]2[/SUP] * rho * S[SUB]D[/SUB] * x[SUB]p[/SUB] / r

where:
p[SUB]RMS[/SUB] = RMS acoustic pressure in Pascals
f = frequency in Hz (= 20 Hz in this case)
rho = density of air (= 1.2041 kg / m[SUP]2[/SUP] at 20 deg C)
S[SUB]D[/SUB] = surface area of driver in m[SUP]2[/SUP] (= 0.32835 m[SUP]2[/SUP] total for two 18" drivers)
x[SUB]p[/SUB] = peak displacement in meters (= .034 per Magico's 34mm claim)
r = distance in meters (assumed to be 1 meter)

To compute SPL, you calculate:

SPL = 20 * log[SUB]10[/SUB](p[SUB]RMS[/SUB] / p[SUB]REF[/SUB])

where:

p[SUB]REF[/SUB] = 2 * 10[SUP]-5[/SUP] Pascals

Plugging in the numbers above, you get SPL = 121.5 dB. That's 14.5 dB short of their 136 dB claim, which is equivalent to needing the radiating surface area S[SUB]D[/SUB] to be 5.3 times larger. Stated another way, and rounding to an integer number of drivers, it would require 11 18" drivers with 34mm x[SUB]max[/SUB] to get there.
Assuming you have the details right, that fits with most ultra-high end gear. Usually, the claims are the purest BS.

It also seems appropriate for a company calling itself "Magico."

If they are for real, they should submit one of their subwoofers to independent reviewers for proper measurement. If they don't, that is pretty much an admission that they are just liars. Liars don't want their claims to be proven as lies, and so they often try to avoid such situations.
 
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Pyrrho

Pyrrho

Audioholic Ninja
I never heard that brand and will not commend any regarding their actuall products, but WOW - their website is probably have a great chance of winning the web site design award in the category of most useless web site on the internet
If someone is selling "magic," as one might suppose from a company calling itself "Magico," one should expect something useless.
 
Pyrrho

Pyrrho

Audioholic Ninja
I'd love to see actual measurements for either of those subs. 550 is a lot of weight to have to move. I wouldn't want to try that. I'm not even that old yet.
Judging from andy_c's post, I think you never will see actual measurements. Also, the ultra high end isn't generally about actual performance, but about parting rich people from their money. I remember reading about some very expensive power amplifiers that measured like crap, but would cost you 6 figures to buy. You could do far better for $2k, if accurate performance is the goal (and with greater power output). At the ultra high end, you very often get less than if you paid a sane amount of money. You do, however, get to brag about how expensive it is, and can say that very few people have what you have. And for some people, that is the goal.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Not to defend Magico, per se, because I can't say that I'm a fan of their products, one thing to keep in mind is that if the QSub-18 could indeed do 121db at 1 meter at 20Hz it would outperform the SVS PB-13 Ultra, tuned to 20Hz, by over 10db, and the more pedestrian Funk Audio 18.0 or the Velodyne DD18 Plus by about 17db. I really don't care one way or another, because I wouldn't keep such a beast if someone gave me a QSub-18 for free, but, assuming it really could do only 121db at 20Hz, it would be far and away the best commercial subwoofer Ricci has ever tested.
 
Steve81

Steve81

Audioholics Five-0
Not to defend Magico, per se, because I can't say that I'm a fan of their products, one thing to keep in mind is that if the QSub-18 could indeed do 121db at 1 meter at 20Hz it would outperform the SVS PB-13 Ultra, tuned to 20Hz, by over 10db, and the more pedestrian Funk Audio 18.0 or the Velodyne DD18 Plus by about 17db.
Not quite; don't forget, Josh's numbers are reported @ 2m, RMS; reporting at 1m peak would add 9dB to his figures.
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Not quite; don't forget, Josh's numbers are reported @ 2m, RMS; reporting at 1m peak would add 9dB to his figures.
You're saying that you'd still bet on the PB-13 Ultra? That's difficult to believe.
 
Steve81

Steve81

Audioholics Five-0
You're saying that you'd still bet on the PB-13 Ultra? That's difficult to believe.
I'd suspect the PB13U's output would be awfully close at 20Hz, though it wouldn't fare well at other frequencies. Keep in mind that the PB13U has slightly more clean output than 2 Velodyne DD18+s/Funk 18.0s at 20Hz (110.6dB vs 103.6dB @ 2m, one to one, +6dB for duals).
 
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Irvrobinson

Irvrobinson

Audioholic Spartan
+6dB for distance, +3dB for peak level instead of RMS.
andy_c's calculation, where I got the 121db/1m figure from, is RMS, though I still feel sort of silly for the 1m/2m oversight. The Magico spec of 136db at 20Hz is undefined, though at 1% distortion it makes you wonder what universe they reside in, where the laws of physics must be different.

This is all a moot discussion anyway, because I think the chance of us seeing Josh review this monster is close to nil. Too bad, it would be great subwoofer porn, even though none of us would ever buy the silly thing.
 
Steve81

Steve81

Audioholics Five-0
andy_c's calculation, where I got the 121db/1m figure from, is RMS
My mistake:eek:. One thing I would note from his calc as well is that it's assuming an Sd of 1641.75 cm^2, i.e. full 18" diameter. The driver AFAIK is an Aurasound 18" model with an actual Sd of 1164cm^2, which will bring the figure down ~3dB anyway :D


The Magico spec of 136db at 20Hz is undefined, though at 1% distortion it makes you wonder what universe they reside in, where the laws of physics must be different.

This is all a moot discussion anyway, because I think the chance of us seeing Josh review this monster is close to nil. Too bad, it would be great subwoofer porn, even though none of us would ever buy the silly thing.
Agreed.
 
A

andy_c

Audioholic
My mistake:eek:. One thing I would note from his calc as well is that it's assuming an Sd of 1641.75 cm^2, i.e. full 18" diameter. The driver AFAIK is an Aurasound 18" model with an actual Sd of 1164cm^2, which will bring the figure down ~3dB anyway :D
At the time I did the calculations, I didn't know what drivers they were using, so I was giving them the benefit of the doubt. That change of S[SUB]D[/SUB] means it would require 15 such drivers to reach that SPL instead of 11. But also, their claim is for 136 dB SPL at 1 percent distortion. I'm quite sure even the most state-of-the-art driver will have more than 1 percent distortion with a peak cone excursion of 34 mm.

From a power perspective, they claim 90 dB sensitivity, though they don't say whether this is referenced to 1 Watt or 2.83 Volts RMS (2 Watts into 4 Ohms). Giving them the benefit of the doubt again and assuming it's 1 Watt, and even more generously assuming that the 90 dB sensitivity spec applies at 20 Hz, that would require an amplifier of 39,811 Watts (or 79,622 Watts if it's a 2.83 Volt RMS sensitivity spec). :D

The claims are just preposterous.
 
BrettMendes

BrettMendes

Audioholic Intern
I can't comment on their claims but I got to hear the Qsub-18 yesterday. It was, without question, the most powerful, tightly controlled, and cleanest bass I've ever heard.
 
M

MikoDee

Audiophyte
For $36 or $22K I could buy a lot of SVS Subs and achieve even higher levels of performance. These over priced subs are farcical to the majority of your readership.
 
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