Home Theater Forum and Systems banner

1 - 20 of 20 Posts

·
Banned
Joined
·
1,074 Posts
Discussion Starter #1
What are the pros/cons of simply using the default plot WinISD gives for a particular driver in a particular alignment. Please, for now, ignore room gain as well as room peaks and nodes
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter #3
I see more volume was given to the lower box... I know usually the volume is limited by available space, but if space was unlimited, do you take suggested space into consideration?



like it appears going sealed WinISD suggests 10 cubes per sub, and going vented 20 cubes per sub...meaningless?
 

·
Registered
Joined
·
117 Posts
I am sure that when the software was written, they simply decided on generic default settings that would be a good starting point. But thinking the program would come up with the best alignment for any driver is probably wishful thinking.
 

·
Registered
Joined
·
438 Posts
I am sure that when the software was written, they simply decided on generic default settings that would be a good starting point. But thinking the program would come up with the best alignment for any driver is probably wishful thinking.
The "generic default settings" are calculations that were based on certain design criteria, like minimum group delay, or certain roll-off characteristics. These formulas were derived before computer aided models existed and correlate extremely well to the real world.

If you choose a formula that matches your design intent, then there is no reason that formula won't result in a "best alignment" for the driver.

I personally use the models and predictions as a means to get close to what I want and if I seriously want to tweak things out, only then will I build a few prototypes and make the real world do what I want. There is always some discrepancy between the model and the real world because the models don't take into account every real world behavior.
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter #7
The "generic default settings" are calculations that were based on certain design criteria, like minimum group delay, or certain roll-off characteristics. These formulas were derived before computer aided models existed and correlate extremely well to the real world.
so room modes, nodes, nulls, and voids..peaks and dips asside... could a person simply build the default and be happy with its results as is? Room gain adding a little more being just a bonus per se?
 

·
Registered
Joined
·
16 Posts
I don't see any reason why not if you're happy with the extension the "default" design gives you. They'll default works well for home subs but not car(in general).
 

·
Registered
Joined
·
438 Posts
so room modes, nodes, nulls, and voids..peaks and dips asside... could a person simply build the default and be happy with its results as is? Room gain adding a little more being just a bonus per se?
Yep, I know quite a few people that just build from the formulas. Their stuff sounds good too.

That's not to imply anything magical about these alignments, but you could argue that they each have their own signature sound.
 

·
Registered
Joined
·
16 Posts
how would you change it for in car?
With most of the popular subs used for home subs there would be too much low end in a car because there is so much cabin gain. You'd want the sub to rolll off much sooner. As an example my JL 8W7 is in a 1 cu ft enclosure tuned to 34 Hz...in my house it was flat to ~30Hz...in my car it's flat to ~20Hz. This is in a convertible with a soft top so it's kind of lossy compared to other cars types which would provide even more cabin gain.
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter #12
With most of the popular subs used for home subs there would be too much low end in a car because there is so much cabin gain. You'd want the sub to rolll off much sooner. As an example my JL 8W7 is in a 1 cu ft enclosure tuned to 34 Hz...in my house it was flat to ~30Hz...in my car it's flat to ~20Hz. This is in a convertible with a soft top so it's kind of lossy compared to other cars types which would provide even more cabin gain.
If you tune to 34Hz in-car, cabin gain keeps output flat to 20Hz... what happenes when the driver is actually playing from 20Hz-34Hz?
 

·
Registered
Joined
·
16 Posts
If you tune to 34Hz in-car, cabin gain keeps output flat to 20Hz... what happenes when the driver is actually playing from 20Hz-34Hz?
It was relatively flat in that area but I had a hump ~50-60Hz I ended up eq'ing out. I've been wanting to stuff the port which should help it play a little deeper and lower the hump by itself but I don't know what to use to stuff a slot port. That and I'm lazy.
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter #14
Where should the SSF be set with a 34Hz tuning...29Hz? So the driver unloads below 34Hz and the port becomes a hole in the box... I giant leak... but, the driver still has more output than the port has cancellation, and, cabin gain makes more out of this decreased output..keeping things flat?
 

·
Registered
Joined
·
16 Posts
Where should the SSF be set with a 34Hz tuning...29Hz? So the driver unloads below 34Hz and the port becomes a hole in the box... I giant leak... but, the driver still has more output than the port has cancellation, and, cabin gain makes more out of this decreased output..keeping things flat?
I have no SSF on it, but generally you want it very close to tuning freq, you could use WINISD to see how SSF's effect excursion. Below tuning there is output but it rolls off ~24dB/octave which is a steep slope but coupled with the cabin gain it worked out to be relatively flat.
 

·
Registered
Joined
·
438 Posts
With most of the popular subs used for home subs there would be too much low end in a car because there is so much cabin gain. You'd want the sub to rolll off much sooner.
Why throw away acoustic efficiency to make the rolloff match the gain of the car? If you alreay have EQ upstream then I would recommend putting the cut before the amplifier so that the amp and speaker don't have to work as hard.
Posted via Mobile Device
 

·
Registered
Joined
·
16 Posts
Why throw away acoustic efficiency to make the rolloff match the gain of the car? If you alreay have EQ upstream then I would recommend putting the cut before the amplifier so that the amp and speaker don't have to work as hard.
Posted via Mobile Device
I'm not sure I follow.
 

·
Registered
Joined
·
438 Posts
Let's say a bigger box gives you an F3 of 25Hz and that your cabin gain starts at 50Hz. The output at 25Hz is going to be 12dB louder than at 50Hz (assuming a full 12dB/octave of gain). If you make the cabinet smaller so that its F3 is at 50Hz, then you are giving up 12dB of efficiency down low and will need over 10x the power for the same SPL. If you put cut before the amplifier, then you need 10x less power for the same SPL. The overall MaxSPL shouldn't be affected unless the extra power handling required to achieve max excursion exceeds the power handling for the driver.

If you want to think of it another way, a smaller rear volume makes it harder for the driver to move, which in turn requires more power for the same excursion. Since the SPL inside the car is a function of the displacement of air, then what matters is the amount of power required to achieve the same excursion. With a bigger box, you can EQ the amplifier so that the excursion matches that of the driver in a smaller box.

Clear as mud?
 

·
Registered
Joined
·
16 Posts
Let's say a bigger box gives you an F3 of 25Hz and that your cabin gain starts at 50Hz. The output at 25Hz is going to be 12dB louder than at 50Hz (assuming a full 12dB/octave of gain). If you make the cabinet smaller so that its F3 is at 50Hz, then you are giving up 12dB of efficiency down low and will need over 10x the power for the same SPL. If you put cut before the amplifier, then you need 10x less power for the same SPL. The overall MaxSPL shouldn't be affected unless the extra power handling required to achieve max excursion exceeds the power handling for the driver.

If you want to think of it another way, a smaller rear volume makes it harder for the driver to move, which in turn requires more power for the same excursion. Since the SPL inside the car is a function of the displacement of air, then what matters is the amount of power required to achieve the same excursion. With a bigger box, you can EQ the amplifier so that the excursion matches that of the driver in a smaller box.

Clear as mud?
I figured that's what you were getting at but wan't sure cause I thought it a bit unrealistic to fit an enclosure to go that deep in my trunk. I guess it makes sense acoustically but practically...a lot of people would rather have trunk space. As for me I have a tiny trunk already and don't have that flexible an EQ.
 

·
Registered
Joined
·
2,431 Posts
I figured that's what you were getting at but wan't sure cause I thought it a bit unrealistic to fit an enclosure to go that deep in my trunk. I guess it makes sense acoustically but practically...a lot of people would rather have trunk space. As for me I have a tiny trunk already and don't have that flexible an EQ.
Exactly why I only do sealed subwoofers in car. Keep the box as small as possible and the cabin gain usually compliments the subwoofer response nicely. Resonant enclosures always end up larger and/or with a very peaky, boomy response. If you design the enclosure to match the cabin gain of the vehicle for an even response you end up with something resembling a sealed roll off anyway, so what's the point is my thinking.
 
1 - 20 of 20 Posts
Top