JL TW3

[Daddy_]

Im thinking of getting some slim subs specifically the JL Audio TW3 12s and run them off 600RMS (300 each). JL specs recommends .80 sealed and .95 ported. Should I follow this or go bigger?

[JohnP]

Hi,

 

From my desk....

 

Going "bigger" in increasing the volume of a given enclosure with the hopes of enhancing the low frequency response or increasing the port volume size probably won't give the desired results and may result in a damaged speaker. 

 

One function of a sealed box is to provide sufficient air mass within the box such that the voice coil and former does not travel too far back within the magnet and pole pieces slamming against the rear pole piece.   

 

A ported box gets a bit more complex as the port acts as a chamber vent at certain frequencies and not at others.   A function of this action is port volume, box volume, and speaker cone volume. 

 

One way to see just what would work or not:   If you have access to box construction software ("boxware") on your device of choice you could use it to get an idea of what kind of response curves the manufacturer's boxes give versus what you might propose in  "going bigger".    One thing to look out for in a bode plot of SPL (db) versus frequency (Hz) is any large peaks or dips as such would suggest quite rapid cone acceleration that may suggest in some cases risk of mechanical failure .

 

The "engineering" is pretty much done in a manufacturer's box suggestions and they may have a motive in hedging against warranty claims being conservative with the box designs however it's not a bad point of reference if you want to experiment.   

 

 

[1point21gigawatts]

1 hour ago, JohnP said:

Hi,

 

From my desk....

 

Going "bigger" in increasing the volume of a given enclosure with the hopes of enhancing the low frequency response or increasing the port volume size probably won't give the desired results and may result in a damaged speaker. 

 

One function of a sealed box is to provide sufficient air mass within the box such that the voice coil and former does not travel too far back within the magnet and pole pieces slamming against the rear pole piece.   

 

A ported box gets a bit more complex as the port acts as a chamber vent at certain frequencies and not at others.   A function of this action is port volume, box volume, and speaker cone volume. 

 

One way to see just what would work or not:   If you have access to box construction software ("boxware") on your device of choice you could use it to get an idea of what kind of response curves the manufacturer's boxes give versus what you might propose in  "going bigger".    One thing to look out for in a bode plot of SPL (db) versus frequency (Hz) is any large peaks or dips as such would suggest quite rapid cone acceleration that may suggest in some cases risk of mechanical failure .

 

The "engineering" is pretty much done in a manufacturer's box suggestions and they may have a motive in hedging against warranty claims being conservative with the box designs however it's not a bad point of reference if you want to experiment.   

 

 

You are beginning to play the correct note now when it comes to this forum. Kudos. But he can go bigger without damaging the subwoofer as long as it’s in moderation and not like a 50% or above increase in net volume. Most enclosures over a 20% increase don’t yield good results. But if an increase is done correctly then output can be gained, low end output. Better low end output is the exact reason people that compete use larger than recommended enclosures, anywhere from 10%-20% bigger than recommended. And then the port area is figured after the net volume is figured. The basic formula to remember is 12 to 16 square inches of port area per cubic foot. Smaller and closer to 12” per yields better bandwidth and larger and closer to 16” per yields better low end output.

[1point21gigawatts]

And instead of saying “low frequency response”, say “low end output”.

[Daddy_]

Was thinking if I go sealed .90 and if I go ported 1.05 net volume

[CCole]

In the past I tend to build my enclosures 25-30% larger as a starting point. I then start adding bracing with the intent to stiffen and tweak the output to my liking. This process usually needs to be documented and measured because the gains/losses can be difficult to hear. 
To be clear I overly brace my enclosures with birch and use 2” x 4’s/6’s to take up air space. 
 

Cheers

[1point21gigawatts]

37 minutes ago, CCole said:

In the past I tend to build my enclosures 25-30% larger as a starting point. I then start adding bracing with the intent to stiffen and tweak the output to my liking. This process usually needs to be documented and measured because the gains/losses can be difficult to hear. 
To be clear I overly brace my enclosures with birch and use 2” x 4’s/6’s to take up air space. 
 

Cheers

On most subwoofers, after 20% (25% on some subwoofers) of a net volume increase, on said subwoofer enclosure, it starts to decrease the output.

[1point21gigawatts]

But now that I think about it, some subwoofer enclosures can be increased more than 25% and some subwoofer enclosures can only be increased like 10%. It all depends on the subwoofer’s VAS is relation to the subwoofer’s Q. But “most” subwoofer’s do well in an enclosure 10%-20% bigger.

[Daddy_]

This is also a shallow sub so would 10% sealed or ported be good enough?

 

Also is there any other shallow subs you'd recommend