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minimum or max Thiele/Small parameters

L

leosep

Guest
Sep 12, 2012
71
0
#1
Hi, how are you all?

I want to know the minimum or maximum requirements for a speaker/woofer to be useful at least for a cheap practice cab, for a 12" 10" and 8" woofers. For example: An usable speaker/woofer must have a Xmax of this and that , or no more that this or that.

I know that you all have a personal taste of what sounds good. But i just want to know the general requirements for a usable speaker for a bass cab. I'm just a little confused because of all the info that i read on the internet about the ideal bass driver.
 
#2
leosep said:
Hi, how are you all?

I want to know the minimum or maximum requirements for a speaker/woofer to be useful at least for a cheap practice cab, for a 12" 10" and 8" woofers. For example: An usable speaker/woofer must have a Xmax of this and that , or no more that this or that.

I know that you all have a personal taste of what sounds good. But i just want to know the general requirements for a usable speaker for a bass cab. I'm just a little confused because of all the info that i read on the internet about the ideal bass driver.
Click to expand...

That isnt really how those parameters work. You have to have a cab design in mind to see what the net pairing will get you.
 
#3
So if i pick any driver, will work if i design a good cab for it?

For example:

FS 30.27
Qms 6.11
Vas 1.353
Xmax mm 15
Xmech mm 22.5
Qes 0.47
Re 7.22
Znom 8
BL 25.7
Qts 0.44
SPL 85.4
V.C. Size (in.) 2.5
V.C. Imp DVC 4
Cut-out 11.25?
Depth 6.875
 
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#4
leosep said:
So if i pick any driver, will work if i design a good cab for it?
Click to expand...

You can pick a driver, and balance the tradeoffs of cab design around it. How good it sounds to you, will depend on those trade offs.

What this all really means is you can pick a great driver, and build a crappy cab around it, and have crappy results. You can also pick a budget driver, and build a smart cab around it, and get decent results. Until you start putting specifics in place, and make some design decisions, there is a lot of unknow.
 
#5
I'm asking just because sometimes i see people saying that the driver must have at least a Xmax of #? for this or that. Cant remember right now. Or must be full range. Or the freq response must be like this or that.
 
#8
I would read upon how to design a cab first.
Here's a popular resource:
http://www.parts-express.com/loudspeaker-design-cookbook-7th-edition-book--500-035

Loudspeaker_Design_Cookbook_(7th_edition_-_book_cover).jpg


I believe there are e-versions and PDFs available as well.
 
#11
leosep said:
Hi thanks for the responses, for example i see that people say that car woofers arent good for a bass guitar cab. But now i see that it depends.
Click to expand...

It does depend. The reason why car audio drivers are not practical, is you would need a bajillion of them to be effectively loud enough for a bass rig. So you would have to design around that need. That isnt to say that they wouldnt make sound, but it may not be what you are really looking for in a bass cab.
 
#14
leosep said:
Because of the SPL? So that is what im asking, for example for something practical i need a least a SPL of 95db? Not less that 90?
Click to expand...

Do you mean max SPL? Such as "I need cab that will crank out 120dB"

The drivers' published sensitivity figures are useful when selecting candidates to work together like woofers and mid drivers. Sensitivity is also used to predict response. Something like 'the cab will have flat response, and be down just 3dB at 55Hz'.
 
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#15
Yes. Well i guess there is no rule of thumb when choosing a practical speaker for bass cabs. Because sometimes we dont have the budget to buy a good speaker, but if i want to buy a super cheap one, i want to know if its practical/usable for a bass cab use.
 
#16
Building a cab and designing a cab are two different things. If you just want to build one, I suggest a fEARful build. Plans are posted on-line with a forum for support.

If you want to design, then build, I strongly suggest getting some footing in speaker building such as the book I linked.
 
#17
leosep said:
Yes. Well i guess there is no rule of thumb when choosing a practical speaker for bass cabs. Because sometimes we dont have the budget to buy a good speaker, but if i want to buy a super cheap one, i want to know if its practical/usable for a bass cab use.
Click to expand...

I would tell you that if your budget is so low, that you are better off shopping for a used cab that is already built.
 
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#20
leosep said:
For example:

FS 30.27
Qms 6.11
Vas 1.353
Xmax mm 15
Xmech mm 22.5
Qes 0.47
Re 7.22
Znom 8
BL 25.7
Qts 0.44
SPL 85.4
V.C. Size (in.) 2.5
V.C. Imp DVC 4
Cut-out 11.25?
Depth 6.875
Click to expand...

That looks to me like a subwoofer with a pretty hefty motor.

The T/S parameters will predict response below about 200 Hz or so, but you need to see the measured response curve north of 400 Hz or so (or have some good reason to believe that it's suitable for electric bass). Between 200-400 Hz both the response curve and T/S parameters come into play.

Based on the above parameters being subwoofer-class, I think it's unlikely that woofer would work well for electric bass, either as a stand-alone, or as part of a two- or three-way system, unless it's used in multiples or for low volume (the 2.5" voice coil tells me the thermal power handling will probably be in the 250-350 watt ballpark when used for prosound, and the 85 dB efficiency tells me that just one probably won't keep up with a drummer).

The Loudspeaker Design Cookbook is where I got my start, six editions ago.
 
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