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Old 25th February 2011, 02:52 PM   #21
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Quote:
Originally Posted by Scottmoose View Post
I'm afraid not. Mass affects efficiency, but it does not impact on transient response. Transient response is inherently linked to bandwidth covered & the acceleration of the powertrain is proportional only to the amount of current in the voicecoil. The equation B*L*i / Mms clearly demonstrates this, where B = magnetic strength in the Vc gap, L = length of the VC in the VC gap, i = current in the VC, and Mms = moving mass of the powertrain (all in SI units, naturally). Dan Wiggins's did a short writeup on the subject a few years ago: http://www.adireaudio.com/Files/WooferSpeed.pdf
Well, sort of. I got hammered the last time this subject came up, but I remain unrepentant. If you do the dimensional analysis, BLi/Mms has the units of 1/s^2, which is close to accereation. Acceleration, of course, is m/s^2. The problem with the quoted discussion is that it assumes BL/Mms is constant. That s fine for any given driver, but not applicable as a comparison fo different drivers, which is the relevant point of the original discussion -- comparing drivers of different sizes. Different drivers will have different BL and Mms. Therefore, either BLi/Ms or BL/Mms should be an index of a drivers "speed", sort of.

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Old 25th February 2011, 04:48 PM   #22
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Originally Posted by planet10 View Post
You can get pretty low (and with finesse) with some of the FRs in this size (the CSS EL70 is a real stunner in this department), but they just can;t move the air needed for lots of impact. Besides, freeing the FR of low bass, gives big imprvements in mirange & HF finese.

dave

True. It can play bass well, but as Dave says it can't move enough air to get the right impact. But i guess no 4" will do that unless it has 2km excursion
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Old 25th February 2011, 05:17 PM   #23
hm is offline hm  Europe
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Default bass by 4"

"but as Dave says it can't move enough air to get the right impact. But i guess no 4" will do"

hello,
thats not true by the right enclosure, look the double horn KORNETT
with two 4-5" driver 34 Hz with unbelievable "impact", translate the feedback
all write "unbelievable bass for the driver size"
kornett FB göö-- translate helps
Click the image to open in full size.
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Old 25th February 2011, 05:28 PM   #24
el`Ol is offline el`Ol  Germany
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Originally Posted by Bob Brines View Post
Therefore, either BLi/Ms or BL/Mms should be an index of a drivers "speed", sort of.
It's Bl/(Sqrt(Re)*Mms), since what you feed the driver with is voltage, not current. Otherwise you would overestimate the suitability for horns of a 16 Ohm driver and underestimate it for a 4 Ohm driver in comparison with 8 Ohm drivers.
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Old 25th February 2011, 05:31 PM   #25
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Quote:
Originally Posted by Bob Brines View Post
Well, sort of. I got hammered the last time this subject came up, but I remain unrepentant. If you do the dimensional analysis, BLi/Mms has the units of 1/s^2, which is close to accereation. Acceleration, of course, is m/s^2. The problem with the quoted discussion is that it assumes BL/Mms is constant. That s fine for any given driver, but not applicable as a comparison fo different drivers, which is the relevant point of the original discussion -- comparing drivers of different sizes. Different drivers will have different BL and Mms. Therefore, either BLi/Ms or BL/Mms should be an index of a drivers "speed", sort of.
I'm going to disagree with you on this one Bob (no offense). Thing is, I don't really know what this speed thing is supposed to be.

I agree it's an interesting exercise, & providing SI units are used, you can establish a nominal acceleration factor for a drive unit in meters per second per second per ampere. But from my POV, it doesn't tell you a great deal. It can serve as a guide to relative efficiency, but for most uses, the SPL figure is just as useful. As a guide to transient response, it's of questionable value at best. In the case of a 'normal' driver, e.g. a midbass, it gives a rough indication of the pistonic BW of the powertrain, but VC inductance may roll it off before that, so it will need a lower XO point / higher order XO slope to a supporting HF unit to maintain a decent transient respojnse. In the case of drive units which use (more or less) controlled breakup to extend their HF BW, transient response becomes pretty much a non-issue, problems with response linearity aside.
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Old 25th February 2011, 05:44 PM   #26
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Quote:
Originally Posted by hm View Post
"but as Dace says it can't move enough air to get the right impact. But i guess no 4" will do"

hello,
thats not true by the right enclosure, look the double horn KORNETT
with two 4-5" driver 34 Hz with unbelievable "impact", translate the feedback
all write "unbelievable bass for the driver size"
kornett FB göö-- translate helps
Click the image to open in full size.

I was not only talking about the volumes. With impact i mean you feel the bass in your chest. I've heard the speakers you can see here: Lindell Audio and they had lots of impact. I was actually one of the very first in the world to hear them. Incredible sound and the bass was really really good, and with loads of "punch" so you felt it in your chest.
I played Mustasch - Double Nature on them and it felt like live but sounded much better. Yes, i've heard the song live aswell. I think the woofers in those speakers are 6.5" or something, the voice-coil was 5" or so i think :P
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Old 25th February 2011, 05:51 PM   #27
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I am a new member here, but a non scientific diy'er, I don't measure and work but rather, trust my ears, so to say I feel that by competing 2x4" with 1x8 incher and keeping all other params constant,
you could say that the 2x4" will react faster than a 1x8" also I feel the throw of 2x4" is shorter than that of 1x8", but I have a question here ..
If you combine the power of magnetic flux density of both the 4" wouldn't that be double of the single 8" ?
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Old 25th February 2011, 05:54 PM   #28
hm is offline hm  Europe
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Default Rullknufs

if you want more take the double horn for example
SAXOPHON and RDH20
Click the image to open in full size.
suck out depents on measurement distance and room, look measuremet on 3 m, it is gone
Click the image to open in full size.
compair the impedance below 50 Hz with every other bass solution!!
What will your amp like more, a normal IMP or this, what does that mean for the bass performance!?
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Last edited by hm; 25th February 2011 at 05:58 PM.
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Old 25th February 2011, 06:08 PM   #29
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Quote:
Originally Posted by hm View Post
if you want more take the double horn for example
SAXOPHON and RDH20
Click the image to open in full size.
suck out depents on measurement distance and room, look measuremet on 3 m, it is gone
Click the image to open in full size.
compair the impedance below 50 Hz with every other bass solution!!
What will your amp like more, a normal IMP or this, what does that mean for the bass performance!?
Not a clue. Those graphs tells me nothing lol :P As far as i can see it's only about volume and not impact. Aren't those different things?
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Old 25th February 2011, 06:32 PM   #30
hm is offline hm  Europe
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Hello,
what an impact will you get by 8" FR´s by ~98 dB1W1m, i think enough,
if you compair the SPL to other speaker.
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