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Why 12" drivers can't be musical in the 40-80hz?


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#1 of 94 OFFLINE   Jones_Rush

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Posted March 15 2001 - 11:42 PM

Why can't a 12" sub driver produce precise bass signals between 40-80hz like a 8" sub driver ?.
40-50 cycles seem to be the limit to what a 12" driver can accurately produce, I wonder why ?.

#2 of 94 OFFLINE   Jack Gilvey

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Posted March 16 2001 - 12:04 AM

This seems completely unfounded. Where is this information from?

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#3 of 94 OFFLINE   ThomasW

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Posted March 16 2001 - 12:12 AM

For higher output levels(SPL's) a 12" driver "should" actually perform better. The goal is to have the driver operate in a frequency range where it's performance is most "pistonic" = linear.

Most 8" drivers are beginning to break up or reach the limits of their performance especially around 40Hz. Where as a 12" will be just crusing along. So the info that 12" drivers will be "running out of gas" at 40-50Hz isn't true. My IB sub (using multiple 12"s) doesn't start to roll off significantly until below 15Hz.

This info is predicated on both drivers being of equal quality/performance.



#4 of 94 OFFLINE   Daniel Seuthe

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Posted March 16 2001 - 12:23 AM

This is dependent on the used drivers. In general the cone of a 12" driver weights more compared to a 8" driver. So it's possible that the cone move slower.

Daniel

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#5 of 94 OFFLINE   Jones_Rush

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Posted March 16 2001 - 12:27 AM

Taken from www.nOrh.com :

"The reason we use small woofers (8") is that a large woofer has more mass and therefore is slower than a smaller woofer. A large woofer is slow to start and slow to stop. A smaller woofer will react much faster".

nOrh is not the only one who claim this, they just described it clear enough so everyone would understand.
Below 40hz, the sub only needs to do 40 cycles the most, so a 12" driver is sufficient, but when a 12" driver is needed to run at 50-80 cycles, it's not fast enough to react precisely in comparison to a 8" driver. Is this what they call: "one note bass" ? of course it's not one note, but definitely less notes than a lighter/faster driver.
(let's get one thing clear, I'm not saying that a 12" sub can't be musical (meaning precise), it can do an excellent job below 50-40hz, it's just that in 50-80hz it losses precision and doesn't do justice for music notes).


#6 of 94 OFFLINE   Ken Cline

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Posted March 16 2001 - 01:06 AM

Quote:
A large woofer is slow to start and slow to stop. A smaller woofer will react much faster

Isn't that why a sealed sub performs better(musically) than a ported sub, i.e. better transient response.

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#7 of 94 OFFLINE   Patrick Sun

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Posted March 16 2001 - 01:08 AM

I think you're just going to have to build a woofer, and then a subwoofer to make you happy. Get a Paradigm X-30 or two and have the woofer (8" driver) do the work in the 40-90Hz range, and have the subwoofer (12" or 15" driver) do the work for the sub-40Hz range. It seems your mind is made up, so there's nothing anyone here can say that will convince you that a 12" driver is good enough (if designed well), so I suggest you go the woofer/subwoofer route to get the performance you are looking for.


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#8 of 94 OFFLINE   Jones_Rush

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Posted March 16 2001 - 01:18 AM

Patrick,
You said:
"It seems your mind is made up, so there's nothing anyone here can say that will convince you that a 12" driver is good enough (if designed well)".

If you'll look at all the posts in this thread, you will find out that no one said anything like : "a 12" driver will be as good as a 8" driver between 50-80hz", they all agree with me, or say that a 12" driver will be better below 40hz and this is more important to them.
The design you suggested above, while intriguing, is way beyond what I can afford currently. I just want to do the "right" compromise.



#9 of 94 OFFLINE   Blake Middleton

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Posted March 16 2001 - 01:31 AM

Then just compromise between the 8" and 12" and get a 10".

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#10 of 94 OFFLINE   Jones_Rush

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Posted March 16 2001 - 01:52 AM

Ok, good advice,
Can you recommend a good 10" driver ?

#11 of 94 OFFLINE   Jack Gilvey

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Posted March 16 2001 - 01:55 AM

Quote:
it's just that in 50-80hz it losses precision and doesn't do justice for music notes
This is not true. It's not surprising to find that info. on the site of a manufacturer who doesn't market a 12" sub,though.
An 8" driver has much more excursion @ 50Hz at a given SPL than a 12", leading to more distortion.

Quote:
but when a 12" driver is needed to run at 50-80 cycles, it's not fast enough to react precisely in comparison to a 8" driver.
The cone of a 12" is heavier, but so is the motor in a good design. The "speed" of a driver is a concept that throws people new to all this.
Instead of parroting a manufacturer's line, tell us your experience with building a sub with an excellent driver such as the Shiva, which maintains its linearity (it replicates the input waveform "fast enough") well above 80Hz.

Show me specifically where someone agreed with you.

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#12 of 94 OFFLINE   Jones_Rush

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Posted March 16 2001 - 02:15 AM

Here is someone who seem to agree with me:
Daniel Seuthe:
"In general the cone of a 12" driver weights more compared to a 8" driver. So it's possible that the cone move slower."

Jack,
I don't have much experience in building a sub, If I had, I guess I wouldn't have to ask for advice.
My guide lines are: as long as there is a consensus on a subject (regarding subs), it is good enough for me.
I thought that there is a consensus regarding the capabilities (or, lack of) of a 12" driver to do a precise job at 80hz. Do you say that I draw incorrect conclusions?

#13 of 94 OFFLINE   Jack Gilvey

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Posted March 16 2001 - 02:31 AM

Quote:
Here is someone who seem to agree with me:
Daniel Seuthe:
"In general the cone of a 12" driver weights more compared to a 8" driver. So it's possible that the cone move slower."
Well, one person who says "in general" and "it's possible". Hardly the stuff on which to base an argument. Anyway, I addressed his point in my last post.

Quote:
I thought that there is a consensus regarding the capabilities (or, lack of) of a 12" driver to do a precise job at 80hz. Do you say that I draw incorrect conclusions?
Your original post specified the range of 40-80Hz,actually.
You may draw whatever conclusions you like. You already have. I'm just wondering where the "concensus" is, aside from that one commercial site.
When constructing a subwoofer, linear response up to 80 Hz is well within the capabilities of a good driver like the Shiva. Many people choose to cross their subs over lower, but that's mainly due to placement/localization issues.

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#14 of 94 OFFLINE   Mark Seaton

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Posted March 16 2001 - 03:03 AM

Jones-

I would have to dissagree with your statement of 40-80Hz being a problem for most 12" drivers. There are room placement issues and other effect which can make an 80Hz crossover problematic, but I have heard many system with very good blend with a 12" used to much higher than 80Hz. Retail subwoofers are a bad means to compare with as most employ limiters to save on the manufacturer's repair costs, and allow them to post better low end response numbers from a sub not capable of reaching high SPL at the bottom end. A Shiva can work quite well above 80Hz, and if you are really interested in clean higher frequency response, check out the Lambda Acoutsic drivers that Stryke Audio offers. As a further example, Lambda has a newer 15" TD series woofer which has better HF response than most 10"ers.

Either build one and see for yourself, or find someone in your area who already has one. You will likely be suprised.

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#15 of 94 OFFLINE   Hank Frankenberg

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Posted March 16 2001 - 03:46 AM

Jones, if you're truly looking for advice and open to being convinced with facts, please note that ThomasW, Jack and Mark know what they're talking about. There is, not surprisingly, lots of misinformation in the world of audio. Look at the success of the Bose little box/driver - they have convinced many people that their bass sound is top notch. Hats off to Bose marketing expertise Posted Image I used to believe the "smaller is faster" line (mainly from manufacturers who used the smaller ones to save costs in: drivers, cabinet size and shipping costs).
Reality is different. A quality 12" or 15" with good motor design can start and stop their cones as fast as an 8".
Try to do some side-by-side comparisons and make an objective assessment. That's part of the fun of this hobby.

#16 of 94 OFFLINE   ThomasW

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Posted March 16 2001 - 04:09 AM

Quote:
Taken from www.nOrh.com :
"The reason we use small woofers (8") is that a large woofer has more mass and therefore is slower than a smaller woofer. A large woofer is slow to start and slow to stop. A smaller woofer will react much faster".

The statement from nOrh is false information (aka bunk), designed to perpetuate a myth.

Any person knowledgable regarding speaker design knows that the "transient response" of a driver is it's "speed". And if 2 different size drivers have the same transient response they have the same "speed".

So people can keep their head buried in the sand and believe this "smaller is faster" nonsense or do some real world RESEARCH and discover the truth about T/S parameters of loudspeakers.



#17 of 94 OFFLINE   SteveEdwards

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Posted March 16 2001 - 06:54 AM

Is there a way to "measure" transient response using T/S parameters?
-Stretch

#18 of 94 OFFLINE   Chris Hoppe

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Posted March 16 2001 - 08:31 AM

Historically, 12" and 15" drivers have been made with essentially the same motors as companies would put on their 8" and 10" drivers.

Of course, this has led to the popular misconception about bigger woofers being "slower" or "sloppy".

This has nothing to do with the size of the cone. Sub-bass is all about moving air. If you have a strong enough motor, you can push any size cone you want accurately!

Consider the Stryke HE driver. If you've ever heard one, you know that it's tight as a drum! Big motor on that one!
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#19 of 94 OFFLINE   DanWiggins

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Posted March 16 2001 - 08:47 AM

Just wanted to say I agree completely with ThomasW, Mark, and the others about cone size and midbass accuracy. There's no relationship there.

Steve,

You cannot determine the transient response of a driver from the T/S parameters alone; you also need to know the type of enclosure and equalization used (crossovers count as EQ for these purposes). The overall SYSTEM Q is what tells you the transient response.

Chris,

You are correct about many 12" and 15" drivers using motors from 8" and 10" drivers. However, the actual size of the motor really isn't a good guide of motor "strength", or even the B field in the gap. The B field strength varies with different magnetic materials used (and also can modulate with temperature, based upon the material).

Additionally, in most drivers, you'll find that increases in magnet height past a certain size really have zero impact. Once you've reached saturation of the top plate, you're pretty much limited. More magnetic material isn't going to help.

With most drivers out there (with top plates between 5/16" and 1/2" thick and 5" in diameter or so) a good inch of 6" diameter high strength ceramic is all that's needed to reach saturation. More magnet - or a stronger magnet material - won't help.

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#20 of 94 OFFLINE   SteveEdwards

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Posted March 16 2001 - 09:17 AM

WinISD (only program I'm familiar with) doesn't show total system Q. How is this calculated?
-Stretch


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