displacement as a function of cabinet preferences

[dhsierra1]

Originally Posted by ThisBass

Your link:
http://en.wikipedia.org/wiki/Mechanical_impedance

At resonance frequencies, the mechanical impedance will be lower, meaning less force is needed to cause a structure to move at a given velocity. The simplest example of this is when a child pushes another on a swing. For the greatest swing amplitude, the frequency of the pushes must be near the resonant frequency of the system.

That's applied physics

So please tell me what you like to point out?

that's not my link or reference.

This is my reference, a well worn copy from my grad school days:

http://www.amazon.com/Viscoelastic-P.../dp/0471048941

Much of which is valid also for non-polymeric materials.

Nor is my point about resonance, I'm well aware of what it is.

I'm not here to get into an argument with you and this will be my last post in this thread, peace.

[makohund]

Originally Posted by ThisBass

That's true for swinging notes (or appro average) but not peaks.
Similar like clipped portion of peaks at power amps you can't notice.

Yes. But that relationship between Xmax, Xlim, peaks, and average signal is going to hold true no matter what Xmax and Xlim are in question. (Though in cases where Xlim isn't much beyond Xmax, pushing average all the way up to Xmax may be a bit risky.)

So that brings us back to the beginning... if not going into distortion, Xmax is as far as you would want to push your average signal, whatever the driver/cab choice. So that's still the limit for the Sd vs Xmax ratio within Vd question, and the Sd vs Vd question.

Or assuming one likes the distortion, Xlim is still as far as you can go, and the same questions can be asked for it.

So... is there a reason to opt for higher Sd at the expense of excursion?
Case 1: Excursion limit = Xmax (for clean SPL)
Case 2: Excursion limit = Xlim (for dirt lovers)

And if a different answer between the two, why? (Or does it change, depending on difference between Xmax and Xlim values?)

[iualum]

Originally Posted by makohund

Given a choice between higher surface area but low excursion, or smaller surface area but higher excursion, which would you choose, and why?

Or would one consider the question irrelevant, as there is not enough information? (Of course there isn't, so lets at least assume they both "sound great", while of course different.)

Some scenarios:

1. Resulting Vd of the smaller surface area cab is much larger.
2. Resulting Vd of both cabs about the same.

I think I know my choice, but am genuinely curious about others.

I want the cab with the greater displacement as long as I have the watts to take advantage of it (as with super Xmax drivers), the bucks to buy it, & it fits in my car. If it's a relatively close Vd call & the price difference is significant, though, I'd do the lower displacement box & not worry about it.

[Codger]

Originally Posted by makohund

So... is there a reason to opt for higher Sd at the expense of excursion?

Near field response? I've seen the comment more than once that people like the playing in front of an 8x10 rather than a single 15. An argument could be made that the far field response is the same, by assuming similar tone profiles and sound intensity for example. Near field?

[barryaudio]

Originally Posted by ThisBass

No problem anyway but:
mechanical compliance [Meters/Newton] which is the inverse of D [Newton/Meter] equals electrical capacitance [Farad].
Both are independent of frequency.

Hate to beat a dead horse, but there is such a thing as complex capacitance (frequency dependent), which is inversely related to the complex impedance. This is at the core of polarization behavior in dielectrics.

[barryaudio]

Originally Posted by makohund

It was "Getting displacement via more surface area, vs getting displacement via more Xmax." So... surface area vs Xmax. Though you are right... if one came out ahead for some reason, that would make the next question "X vs displacement".

I don't the "barryaudio is focusing on driver size" thing at all, I don't see him writing anything of the sort anywhere. So I'm confused at that, too. (I thought the reverse, at least for a little while, when it was said that the comparison required different driver sizes, which it does not.) He's a Greenboy/BFM builder, hardly the sort one expects to find dealing in driver size mythologies.

Thanks That's what I was thinking, rather than a comparison of box sizes or tone. Again, different approaches and let's leave it at that. That's why people post to forums--to get different views!

Anyway, this discussion gets to a core issue that I find challenging in explaining to folks who have mainly bought large-scale production cabs in the past. Why does cab "x" cost more than cab "y" but cab "x" has less speakers? Well, cab "x" can get louder than "y" and this is "why".

[iualum]

Originally Posted by Codger

Near field response? I've seen the comment more than once that people like the playing in front of an 8x10 rather than a single 15. An argument could be made that the far field response is the same, by assuming similar tone profiles and sound intensity for example. Near field?

Very unlikely. Maybe a 215 depending on the 215's drivers.

One of the plusses of an 810, though, is that the speakers are closer to the bassist's ears. Of course, the 215 (or any box) can be elevated.

[makohund]

Originally Posted by iualum

I want the cab with the greater displacement as long as I have the watts to take advantage of it (as with super Xmax drivers), the bucks to buy it, & it fits in my car. If it's a relatively close Vd call & the price difference is significant, though, I'd do the lower displacement box & not worry about it.

That sounds entirely sensible.

[ThisBass]

Originally Posted by barryaudio

Hate to beat a dead horse, but there is such a thing as complex capacitance (frequency dependent), which is inversely related to the complex impedance. This is at the core of polarization behavior in dielectrics.

But we are talking about low band frequencies.

By the other hand if then both, electrical C and mechanical compliance, is very dependent on f,
so that means prediction of crossovers and cab modelings would be all wrong.

[KJung]

Originally Posted by barryaudio

Thanks That's what I was thinking, rather than a comparison of box sizes or tone. Again, different approaches and let's leave it at that. That's why people post to forums--to get different views!

Anyway, this discussion gets to a core issue that I find challenging in explaining to folks who have mainly bought large-scale production cabs in the past. Why does cab "x" cost more than cab "y" but cab "x" has less speakers? Well, cab "x" can get louder than "y" and this is "why".

+1 Fun discussion. I always learn a bit when I dip into the more technical side of things. Lots of ways to look at the issue, it seems

[jungleheat]

As much as people on here like to deny it, there are at the very least "trends"in speaker specs that relate to size. So yes, while there may be some very capable 10s that outperform some 15s, on average, 15s will outperform 12s will outperform 10s, etc... in all/most of the important ways (power handling, xmax, low frequency response, etc...).

But on the other hand, 10s and 12s aren't really that much cheaper than 15s in most cases. On a higher performing pair of 15s, you might spend what, $500? To get the same kind of displacement from 10s, you might spend closer to $600 or 800. But while you're displacement is close to the same, you will probably have a higher breakpoint for low end frequency response, and lower sensitivity (meaning now you need more watts too, which costs more money usually). AND the 2x15 will probably come out lighter and smaller than the equivalent 4x10.

Considering these days it's possible to have a 50 lb 2x15 with great performance that would have been unheard of 20+ years ago, there's not much advantage of going with smaller speakers IF overall volume and performance is your goal and you care about cost. If your performance needs are more modest, you could get away with a single 10 or 12, and put somewhat more money into it than you would into each speaker of a dual 15 cab to get back some of those performance losses.