pros and cons of a downfiring sub?
Thread Starter
Junior Member
Joined: Apr 2008
Posts: 10
From: Massachussets
pros and cons of a downfiring sub?
I am thinking of building a custom box with downfiring subs. Has anyone heard of it damaging the subs, due to heat or anything else.
Any info would be a huge help.
Any info would be a huge help.
If its a sub thats designed for it, not as big a deal (home theater has many, and I have one). All will eventually sag, but the subs designed for it have that allowance for sag designed in.
Senior Member
SL Member
Joined: Jan 2006
Posts: 2,338
From: San Diego (Mira Mesa), CA
Originally Posted by elwaylite
If its a sub thats designed for it, not as big a deal (home theater has many, and I have one). All will eventually sag, but the subs designed for it have that allowance for sag designed in.
Subwoofer Qualification Formulae For Downfiring Configurations
We are often asked if a particular driver is suitable for using in a down-firing configuration. Below is a formula that takes into consideration the effects gravity will have on the "sag" of the cone structure of any woofer. You will need the Fs, Vas, Sd (surface area of the cone), and the Xmax to determine the relative long term usefulness of up or down-firing any woofer.
You can calculate the sag of a driver from:
Percentage of Sag = 24,849 / ( Xmax * Fs²)
where
- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).
The following is the same formula, including the relationship of acceleration and Pi in this case:
Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)
where
- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.
As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.
We are often asked if a particular driver is suitable for using in a down-firing configuration. Below is a formula that takes into consideration the effects gravity will have on the "sag" of the cone structure of any woofer. You will need the Fs, Vas, Sd (surface area of the cone), and the Xmax to determine the relative long term usefulness of up or down-firing any woofer.
You can calculate the sag of a driver from:
Percentage of Sag = 24,849 / ( Xmax * Fs²)
where
- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).
The following is the same formula, including the relationship of acceleration and Pi in this case:
Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)
where
- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.
As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.
HTH!
Senior Member
SL Member
Joined: Aug 2006
Posts: 1,066
From: Vegas baby!
Originally Posted by nodsetse
Originally Posted by elwaylite
If its a sub thats designed for it, not as big a deal (home theater has many, and I have one). All will eventually sag, but the subs designed for it have that allowance for sag designed in.
Subwoofer Qualification Formulae For Downfiring Configurations
We are often asked if a particular driver is suitable for using in a down-firing configuration. Below is a formula that takes into consideration the effects gravity will have on the "sag" of the cone structure of any woofer. You will need the Fs, Vas, Sd (surface area of the cone), and the Xmax to determine the relative long term usefulness of up or down-firing any woofer.
You can calculate the sag of a driver from:
Percentage of Sag = 24,849 / ( Xmax * Fs²)
where
- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).
The following is the same formula, including the relationship of acceleration and Pi in this case:
Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)
where
- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.
As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.
We are often asked if a particular driver is suitable for using in a down-firing configuration. Below is a formula that takes into consideration the effects gravity will have on the "sag" of the cone structure of any woofer. You will need the Fs, Vas, Sd (surface area of the cone), and the Xmax to determine the relative long term usefulness of up or down-firing any woofer.
You can calculate the sag of a driver from:
Percentage of Sag = 24,849 / ( Xmax * Fs²)
where
- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).
The following is the same formula, including the relationship of acceleration and Pi in this case:
Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)
where
- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.
As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.
HTH!
Thread Starter
Junior Member
Joined: Apr 2008
Posts: 10
From: Massachussets
wow now my brain hurts
I am going to be running a JLaudio 8w7 and a JLaudio 250x1 amp i am sure it will be fine.... then again it may take off
thanks to everyone who replied
Wish me luck.....
I am going to be running a JLaudio 8w7 and a JLaudio 250x1 amp i am sure it will be fine.... then again it may take off
thanks to everyone who replied
Wish me luck.....
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