15 inch Cabinet Design??

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MJL21193 said:



And how do you determine the correct size box without considering Cms?

why dont you take your favorite driver, model it in your favorite software and get a nice sealed box for it there.

then change CMS to make it 100 times more loose and see if the change in response is significant.

to answer your question - i don't calculate anything. i don't even bother keeping the list of those formulas. instead for a certain size driver ( for a particular SD ) you can compare it to other drivers that size which are good and see how it differs. if it has less BL^2/Re it will need a larger box(all else being equal). if it has higher MMS it will need a larger box(all else being equal). if it has lower efficiency it will need a larger box. drivers that need the least box are the ones with high BL, low MMS and resulting high efficiency.

this is the kind of driver that needs the least box volume

for the above 10" driver recommended box is 20 liters vented ...

ok im going to have to take a break from further discussion until thursday afternoon or so because i have some stuff to do ...

when im back i can explain the logic that i use to arrive at all these relationships and no, it does not come from any formulas except those found in regular physics books

see ya later ...
 
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vasyachkin said:


to answer your question - i don't calculate anything. i don't even bother keeping the list of those formulas. instead for a certain size driver ( for a particular SD ) you can compare it to other drivers that size which are good and see how it differs. if it has less BL^2/Re it will need a larger box(all else being equal). if it has higher MMS it will need a larger box(all else being equal). if it has lower efficiency it will need a larger box. drivers that need the least box are the ones with high BL, low MMS and resulting high efficiency.


It sounds like you prefer to do things the hard way.
Cms is used to determine VAS. Every software box design calculator uses Vas, Qms, Qes, Fs and SD to model the best size box for the driver.
It's not much of a hardship to input these 5 numbers and let the software do the math.
No need to keep formulas or to understand the relationship these numbers have with the driver. Someone has already done that.
 

AKN

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vasyachkin said:


i don't care about compliance because as soon as you put the driver in a box it becomes meaningless.

SD on the other hand is still there ...


Hi,

You were talking about Qts not boxes (or Qtc) in your sentence I quoted.
Now you don't care about compliance when you put speakers in a box, what does that concern Qts?
 
WOW!!

I thought this was a simple question....

I will build a 50L and port it to suit, If I'm not happy I will burn this forum down!!!
HAHAHAAAA...

I noticed that the 12inch has two voice coils of 4ohms, I don't know if the plate amp (160wrms@4ohm) will be stable at 2ohm - works fine at 4ohm.
8 would be wasting power I think.

Any way of telling if the thing is 2ohm stable?
If I hook only one coil will this mess the specs of the box/speaker?


Questions..Questions...
 
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tb46 said:
Hi Chico,
I plugged the values you gave at the beginning of this thread into Boxplot, and it looks like your 15" wants to be in a closed box, volume: 4.75 ft^3. The 12"er would work in a vented box, volume: 3 ft^3, duct: I.D.: 3" x 9" long.:)


Based on those dimensions, I guess Boxplot is completely useless.

133 litres is way too small for the 15.

84 litres is too big for the 12.

Get Unibox.
 
Hi MJL21193,

If I may, Boxplot is a very fine, easy to use design progam that has produced repeatable and verifyable results for me again and again.
My suggestions are based on the assumption that the type of 15" speaker Chicho has seems to work best in a reduced volume enclosure with a small bump in the response band, and this volume is sufficient to apply damping material (e.g.: polyfill) to tune the response; and @ 4.75ft^3 it is already quite large.
The alignment for the 12" is close to an EBS alignment, and it is a whole lot easier (at least to me) to reduce the size of a reflex box that is a little too large than to increase it; it also allows the builder to play with sealed and aperiodic tunings.
Again, don't blame Boxplot for my suggestions, and, have a nice day.
 
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4fun said:
Hi,

You were talking about Qts not boxes (or Qtc) in your sentence I quoted.
Now you don't care about compliance when you put speakers in a box, what does that concern Qts?

what good are TS parametrs if you are not putting the driver in a box ?

if drivers were designed to work in infinite baffle nobody would need TS paramters and you would simply get a response curve in the specs. the entire point of TS paramters is to model box interaction.

drivers are called components for a reason. you have to think of them as such - as a part of the system.
 
if drivers were designed to work in infinite baffle nobody would need TS paramters and you would simply get a response curve in the specs. the entire point of TS parameters is to model box interaction.
Since we don't know how all of the worlds drivers were designed, we use T/S parameters to determine how a woofer should be installed, in this case the high Qts and Vas indicate a very large sealed box or an OB/IB arrangement.
 
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marchel said:
"when im back i can explain the logic that i use to arrive at all these relationships and no, it does not come from any formulas except those found in regular physics books

see ya later ..."


No need, LOL. :devilr:

how you manage to draw satisfaction from not understanding speaker operation is beyond me.

there is nothing wrong with not understanding certain things ... but what is so funny about understanding them ?
 
If I hook only one coil will this mess the specs of the box/speaker?
yes it will mess it all up. don't even think of using just one of the two coils.

Actually this is done all of the time, since you have two 4ohm coils, you can hook one to the amp which is 4 ohm rated and the other to a resistor to tune the Q of the driver. There are several discussions on here about that. Or read this
 
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nunayafb said:
in this case the high Qts and Vas indicate a very large sealed box or an OB/IB arrangement.

yes but i dont need to know either QTS or VAS to tell you the same thing.

i just need to compare this woofer to a well designed woofer like

good 15" woofer

and notice that it has much smaller BL^2/Re and i assume MMS is not significantly lower either because MMS on Beyma is already relatively low for a 15" subwoofer.

thus the driver needs a big box ...

a speaker is a spring + mass + damping

spring comes from SD and box volume

mass is MMS

and damping is BL^2/Re

parameters like Qts and Vas are not necessary ... they are there for convenience just like Efficiency Bandwidth Product
 
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nunayafb said:



Actually this is done all of the time, since you have two 4ohm coils, you can hook one to the amp which is 4 ohm rated and the other to a resistor to tune the Q of the driver. There are several discussions on here about that. Or read this

well if you short the other VC you will restore the damping but you will not restore the output. that is you would not get more output than from a 8 ohm series connection.

i dont see the point ...
 
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MJL21193 said:




Why would you assume anything? All of the specs are published or can be measured, why not use them?

because i didnt see MMS spec and why should i bother looking for it when QTS and VAS do not contradict my assumption :)

Chicho's driver may have slightly lower MMS but not enough to offset its weak BL. i mean for it to be light enough to work with BL of 10 it would be made out of beryllium or something. and if they were too cheap to give it good BL they certainly would be too cheap to use some sort of aerospace materials on the cone.
 
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