Advice on a 15" ext.

[bass_ferret]

[quote name='xgsjx' post='421885' date='Feb 28 2009, 07:10 PM']Something I noticed from reading that manual & I've noticed it before...The 4x10 has a usable response of 31hz to 13khz & the 1x15 has a usable response of 40hz to 13khz.
Does this mean that if you was to compare each individually, the 4x10 would produce a deeper bass? I understand the frequency curve throughout would probably differ considerably as you moved up the octaves.[/quote]
That would be my interpretation. And a lot louder. I know a lot of specs are BS but when comparing the same manufacturer it should be there abouts for their products.

[bass_ferret]

[quote name='Marcus' post='421918' date='Feb 28 2009, 07:49 PM']What does he care....... he's hearing IEM's

The GK is just planted on stage to keep the deal going......, he doesn't even hear the GK tone, nore do you get it FOH as he used a Radial DI to feed his IEM's FOH and the GK Rigg !

Rock Stars eh !!![/quote]
Exactly. For a lot of players the rig is just a prop

[Sharkfinger]

[quote name='bass_ferret' post='422129' date='Mar 1 2009, 01:06 AM']Exactly. For a lot of players the rig is just a prop [/quote]
Which is why Geddy Lee is known to have fake tumble driers behind him (being a Tech 21 endorsee...)! IMO, if you're going to have a "prop", might as well make it amusing or quirky.

Sorry for the thread highjack!

Also have a relevant (probably stupid) question: if driver diameter has minimal effect on frequency generated and it's all down to cabinet tuning, why are PA subs traditionally loaded with 15" or 18" drivers, especially in higher power applications?

[stevie]

[quote name='Sharkfinger' post='423161' date='Mar 2 2009, 01:19 PM']Also have a relevant (probably stupid) question: if driver diameter has minimal effect on frequency generated and it's all down to cabinet tuning, why are PA subs traditionally loaded with 15" or 18" drivers, especially in higher power applications?[/quote]

It's a perfectly valid observation. The reason is that sound reinforcement professionals know that, given a level playing field, a larger driver is capable of producing more bass than a smaller one. Twenty-one inch drivers are quite popular now. Also, 'real' bass drivers don't need to reproduce the midrange.

[stevie]

[quote name='cheddatom' post='420966' date='Feb 27 2009, 02:53 PM']So do the same experiment with a the 15" on top and report back.[/quote]

Or better still, just compare them side by side.

[Bill Fitzmaurice]

[quote name='Sharkfinger' post='423161' date='Mar 2 2009, 08:19 AM']Also have a relevant (probably stupid) question: if driver diameter has minimal effect on frequency generated and it's all down to cabinet tuning, why are PA subs traditionally loaded with 15" or 18" drivers, especially in higher power applications?[/quote]Tens and twelves capable of the same response do exist, and with equal total Vd will give equal output. But since it would take more of them to do so it's more cost effective to use fifteens or eighteens. Customer perceptions also are just as pervasive in PA as in electric bass cabs. Most buyers assume that a cab loaded with larger drivers will go lower, so that's what the manufacturers sell. OTOH the most expensive, and best performing, pro-touring subs are folded horns, and in those twelves are the norm. Customers spending upwards of $3k per cab tend to pay more attention to how a cab works rather than what size drivers they employ.

[cheddatom]

[quote name='Bill Fitzmaurice' post='423271' date='Mar 2 2009, 02:43 PM']Vd[/quote]

lol

[stevie]

[quote name='Bill Fitzmaurice' post='423271' date='Mar 2 2009, 02:43 PM']Tens and twelves capable of the same response do exist, and with equal total Vd will give equal output.[/quote]
Bill, you must have missed my earlier post when I explained that this statement was misleading. Otherwise, I’m sure you would not have repeated it here. To clarify, Vd is no more than an expression of how much air a speaker can shift. You cannot predict output based on Vd alone. System efficiency, or how air movement is converted into sound, matters. For example, we are all familiar with how a speaker can shift lots of air outside a cabinet without producing any audible low frequencies at all.

Bigger drivers, with their lower resonant frequency and superior radiation impedance, are by nature more efficient reproducers of low frequencies. The higher resonant frequency of a smaller driver means a higher rollof in a reflex system, which reduces their efficiency at low frequencies. Big drivers are designed to produce bass - that’s what they do. You don’t build a motorway with shovels, no matter how many you’ve got. You get the bulldozers in.

[alexclaber]

From what I've learnt the radiation impedance difference between say a ten and a fifteen is fairly minimal - it becomes more significant when comparing say a six inch cone with an eighteen or a single ten with eight tens. And a bigger shift in radiation impedance happens when you reduce the space in which the driver radiates into by moving it from free space to a corner.

Although a speaker outside a cab may be able to move lots of air it only does so in the very nearfield because front output is cancelled by back output, so the effective Vd of the system drops with increasing wavelength, hence the huge Vd requirement for open baffle speakers. For a sealed or ported cab (assuming equal tuning frequencies) the Vd will be the main determinant of low frequency output.

Bigger drivers don't necessarily have lower resonant frequencies and their radiation impedance will be the same as an equal Sd array of smaller drivers.

But if a driver is to be a true sub then you might as well use the largest possible driver that will work effectively within the cab size you can, rather than having multiple smaller drivers which will end up both costing and weighing more. Or better yet, use a high Vd driver to power a horn array so you get much higher radiation impedance and thus turn more of the air movement into sound.

Alex

[josh3184]

well I personally think a 15" extension is a bit excessive, the most a girl could ever want is about 9"

[bass_ferret]

[quote name='josh3184' post='425135' date='Mar 4 2009, 02:56 PM']well I personally think a 15" extension is a bit excessive, the most a girl could ever want is about 9"[/quote]

[stevie]

[quote name='bass_ferret' post='425345' date='Mar 4 2009, 05:40 PM'] [/quote]

Hey, what’s with all the sexual innuendos? Can't you see there is some seriously nerdy nitpicking going on here?

Anyway, it’s not the size of your bass driver that counts – it’s what you do with it!!

[josh3184]

aint dat da troof!

[Bill Fitzmaurice]

[quote name='stevie' post='425094' date='Mar 4 2009, 09:16 AM']Bill, you must have missed my earlier post.[/quote] No, I just ignored it.

[quote]Bigger drivers, with their lower resonant frequency and superior radiation impedance, are by nature more efficient reproducers of low frequencies.[/quote]
Driver size and Fs are independent of each other. Radiation impedance is determined by system Sd, and the air doesn't care if said Sd is comprised of one larger driver or many smaller ones. However, system efficiency is determined by the sum total system motor strength and Sd, so the multiple motors of smaller drivers can and will allow a grouping of smaller drivers to not only exceed the total output of one larger driver via higher total Vd, they will also allow them to do so with less input power via higher sensitivity. The downside of doing so is the generally higher cost of multiple smaller drivers compared to one larger driver when they are of equal quality. However, multiple lower quality smaller drivers can deliver equal or better results than a lesser number of higher quality drivers at a lower overall cost. That fact was the basis for the development of the SVT, although it was certainly not the first example of multiple driver usage.

[stevie]

[quote name='Bill Fitzmaurice' post='425388' date='Mar 4 2009, 06:14 PM']No, I just ignored it.[/quote]
I know that. I was just being polite.

[quote name='Bill Fitzmaurice' post='425388' date='Mar 4 2009, 06:14 PM']Driver size and Fs are independent of each other.[/quote]
You keep coming up with these ridiculous statements, Bill. Everyone knows that there is a relationship between driver size and Fs. Or perhaps you could tell us how you would build a 1" woofer with a resonant freqency of 18 Hz.

Edited March 4, 2009 by stevie

[alexclaber]

[quote name='stevie' post='425408' date='Mar 4 2009, 06:39 PM']You keep coming up with these ridiculous statements, Bill. Everyone knows that there is a relationship between driver size and Fs. Or perhaps you could tell us how you would build a 1" woofer with a resonant freqency of 18 Hz.[/quote]

Resonant frequency is a function of moving mass and suspension compliance:

Fs = 1/(2*pi*sqrt(Cms*Mms))

So your answer is to use a thick heavy cone and loose suspension.

The problem with a 1" woofer with an 18Hz Fs (assuming huge Xmax to get sufficient Vd) would indeed be related to radiation impedance but that is an extreme example.

Alex

[josh3184]

I shouldn't have wandered into this thread again, I feel completely stupid now after reading that post!

[EBS_freak]

I loves it. Physics arguments reign supreme!

For what it's worth... I would guess the majority of bass players don't care. I wonder how many bass players consider all this when plugging in...? Just a thought like...

...continue!

[Bill Fitzmaurice]

[quote name='EBS_freak' post='425690' date='Mar 4 2009, 08:09 PM']For what it's worth... I would guess the majority of bass players don't care.[/quote]
They should. He who knows how things work can see past the phony baloney claims of the marketeers. He who who does not is at their mercy.

[EBS_freak]

[quote name='Bill Fitzmaurice' post='425693' date='Mar 5 2009, 01:14 AM']They should. He who knows how things work can see past the phony baloney claims of the marketeers. He who who does not is at their mercy.[/quote]

But she already knows. Result? Women rule the bass world.

[Sharkfinger]

[quote name='EBS_freak' post='425699' date='Mar 5 2009, 01:24 AM']But she already knows. Result? Women rule the bass world.[/quote]
They certainly do in my house!

So what I'm getting from this, right or wrong, is that by a rule of thumb the more cone surface area the more LF is produced, whether that be a single large driver (bass bin) or multiple smaller ones (8x10" 'fridge'). Or is my horribly over-simplifying matters making you speaker aficionados tut and shake your heads in exhasperation?

[stevie]

[quote name='josh3184' post='425683' date='Mar 5 2009, 12:58 AM']I shouldn't have wandered into this thread again, I feel completely stupid now after reading that post![/quote]
I thought it was a most welcome diversion, although not quite as hilarious as some of the other posts in this thread.

[stevie]

[quote name='Sharkfinger' post='426154' date='Mar 5 2009, 01:51 PM']So what I'm getting from this, right or wrong, is that by a rule of thumb the more cone surface area the more LF is produced, whether that be a single large driver (bass bin) or multiple smaller ones (8x10" 'fridge'). Or is my horribly over-simplifying matters making you speaker aficionados tut and shake your heads in exhasperation? [/quote]
There are other factors involved, but yes, it's a reasonable way of looking at it.

[Bill Fitzmaurice]

[quote name='Sharkfinger' post='426154' date='Mar 5 2009, 08:51 AM']So what I'm getting from this, right or wrong, is that by a rule of thumb the more cone surface area the more LF is produced,[/quote]
Surface area is only half of a two part equation. What counts is surface area (Sd) multiplied by excursion (Xmax), the result being displacement (Vd). However. as your assumption is shared by the vast masses, it's one capitalized on by the marketeers, who want you to think that you must go larger to go lower, and in so doing hopefully expanding the contents of their coffers. The other side of that coin is that even amongst manufacturers that do possess a social conscience none are going to refuse to build anything that isn't justifiable so long as there's demand for it.

[stevie]

[quote name='alexclaber' post='425679' date='Mar 5 2009, 12:52 AM']Resonant frequency is a function of moving mass and suspension compliance:
Fs = 1/(2*pi*sqrt(Cms*Mms))[/quote]
Exactly. This shows that there is a relationship between a speaker’s resonant frequency and its moving mass. And because there is a direct relationship between moving mass and cone size (double a cone’s area and you double its mass), there is also a relationship between driver size and Fs. Blindingly obvious really. Thanks for that.
[quote name='alexclaber' post='425679' date='Mar 5 2009, 12:52 AM']So your answer is to use a thick heavy cone and loose suspension.[/quote]
In theory, yes, but there are physical limits to what is possible. Still, if fs and driver size were truly independent, you would be able to produce such a driver. The fact that you can’t shows they are not independent.
[quote name='alexclaber' post='425679' date='Mar 5 2009, 12:52 AM']The problem with a 1" woofer with an 18Hz Fs (assuming huge Xmax to get sufficient Vd) would indeed be related to radiation impedance but that is an extreme example.[/quote]
Indeed, but in simple terms, the driver would have to have a cone made out of lead and a suspension made out of Durex. It would in fact cease to be a loudspeaker at all.