F3 - what's it mean

[unknownuser]

What does F3 stand for? I know that means that's what the box is tuned to, but I don't fully understand it. Does that mean the speaker won't play below that? Can someone explain this in layman's terms? Thanks


(Originally posted by: Rob Walters)

[killa]

> What does F3 stand for? I know that means
> that's what the box is tuned to, but I don't
> fully understand it. Does that mean the
> speaker won't play below that? Can someone
> explain this in layman's terms? Thanks
This is the the point that your frequency response starts to trail off.F3 would be the point at wich frequency response drops 3 decibles.

[rudyjakubin]

> What does F3 stand for? I know that means
> that's what the box is tuned to, but I don't
> fully understand it. Does that mean the
> speaker won't play below that? Can someone
> explain this in layman's terms? Thanks

F3 is where the woofer starts dropping in SPL by 3db.
Say the woofer has an F3 of 38 hz and F10 of 25 hz.
This would be an ideal slope because room gain factors in. Room gain implies what it means. The room starts adding/lifting the bass response.
Of course this is depenended on how big the room is!
For some reason I like an F3 of 45 hz or there abouts.
For Home Theatre - build or design a sub for an F3 of 15hz...
Like bogie's Dundgeon....

[unknownuser]

Thanks. So, a rhetorical sub in a sealed box that has an F3of 56 hz would start dropping off 3 db at 56hz, and the same sub in a vented box with an F3 of 37hz drops off 3db @ 37hz. Therefore, for better bass extension I would want to go with the vented cab, right? Thanks for taking the time to explain. It seems so simple :-)

> F3 is where the woofer starts dropping in
> SPL by 3db.
> Say the woofer has an F3 of 38 hz and F10 of
> 25 hz.
> This would be an ideal slope because room
> gain factors in. Room gain implies what it
> means. The room starts adding/lifting the
> bass response.
> Of course this is depenended on how big the
> room is!
> For some reason I like an F3 of 45 hz or
> there abouts.
> For Home Theatre - build or design a sub for
> an F3 of 15hz...
> Like bogie's Dundgeon....



(Originally posted by: Rob Walters)

[Paul K.]

It's not quite that simplistic. The response of the driver in the sealed box will continue to roll off at only 12 dB/octave, whereas the driver in the vented box will roll off at 24 dB/octave. The vented box will output more SPL for a while compared to the sealed box, as frequency decreases, but at some point their two outputs will be equal and below that frequency, the sealed box will have more output, especially with room gain coming into play. Additionally, in a vented box, the driver will "unload" and have somewhat wild movements at a frequency below the tuned output of the vent. Whether a driver is in a sealed or vented box, F3 denotes the frequency at which the driver's output is 3 dB below its "flat" response.
Paul K.

> Thanks. So, a rhetorical sub in a sealed box
> that has an F3of 56 hz would start dropping
> off 3 db at 56hz, and the same sub in a
> vented box with an F3 of 37hz drops off 3db
> @ 37hz. Therefore, for better bass extension
> I would want to go with the vented cab,
> right? Thanks for taking the time to
> explain. It seems so simple :-)

[unknownuser]

Provided Link: http://www.partsexpress.com/pdf/295-490spec.pdf


Thanks. Can we use a real example? Here's a sub that would be used for music only. DAYTON SD315-88 12" SHIELDED DVC SUBWOOFER (Part Number 295-490) I am looking for a clean response, at fair volume, down to about 35hz.

Here's the specs: Specifications: *Power Handling: 120 watts RMS/180 watts max *VCdia: 2" *Le: 1.4 mH *Impedance: 8 ohms per coil *Re: 3.05 ohms *Frequency range: 30-1,000 Hz *Fs: 25 Hz *SPL: 94.0 dB 2.83V/1m *Vas: 5.20 cu. ft. *Qms: 4.00 *Qes: .38 *Qts: .35 *Xmax: 7 mm

My understanding is a sealed cab gives a cleaner playback of music. The recommended sealed box for this has an F3 of 56.62hz. How would this fair for music playback? Would I be better off venting? F3 vented is 37.22hz.

I have never built or used a sub before. I've built some D3's and a few other designs, so woodworkng skills are okay. I'm just having a hard time understanding subs. My intention is to start out cheap and then move up to something more expensive, if neccesary. But, I don't want to waste time and money on a sub that doesn't do what I need.

Thanks

> It's not quite that simplistic. The response
> of the driver in the sealed box will
> continue to roll off at only 12 dB/octave,
> whereas the driver in the vented box will
> roll off at 24 dB/octave. The vented box
> will output more SPL for a while compared to
> the sealed box, as frequency decreases, but
> at some point their two outputs will be
> equal and below that frequency, the sealed
> box will have more output, especially with
> room gain coming into play. Additionally, in
> a vented box, the driver will
> "unload" and have somewhat wild
> movements at a frequency below the tuned
> output of the vent. Whether a driver is in a
> sealed or vented box, F3 denotes the
> frequency at which the driver's output is 3
> dB below its "flat" response.
> Paul K.



(Originally posted by: Rob Walters)

[Chris Roemer]

> Thanks. Can we use a real example? Here's a
> sub that would be used for music only.
> DAYTON SD315-88 12" SHIELDED DVC
> SUBWOOFER (Part Number 295-490) I am looking
> for a clean response, at fair volume, down
> to about 35hz.

This is a pretty great sub, and it's on sale for a month yet at $33! To go with it you want the 100w plate amp, also on sale for $75. That's $108 for a 100w 12" sub. Put it in a 19" cube with about a 4"d PVC port tube, 11" long.

> Here's the specs: Specifications: *Power
> Handling: 120 watts RMS/180 watts max
> *VCdia: 2" *Le: 1.4 mH *Impedance: 8
> ohms per coil *Re: 3.05 ohms *Frequency
> range: 30-1,000 Hz *Fs: 25 Hz *SPL: 94.0 dB
> 2.83V/1m *Vas: 5.20 cu. ft. *Qms: 4.00 *Qes:
> .38 *Qts: .35 *Xmax: 7 mm

> My understanding is a sealed cab gives a
> cleaner playback of music. The recommended
> sealed box for this has an F3 of 56.62hz.
> How would this fair for music playback?
> Would I be better off venting? F3 vented is
> 37.22hz.

Vented this works well for music AND HT. You can get WinISD (beta) at <A HREF="http://www.linearteam.org">www.linearteam.org</A> and model boxes yourself. BTW, the frequency the box is tuned to is known as its Fb (Frequency of box). The speaker's F3 may be slightly higher, lower, or equal to the box's Fb depending on the driver's Qts.

> I have never built or used a sub before.
> I've built some D3's and a few other
> designs, so woodworkng skills are okay. I'm
> just having a hard time understanding subs.
> My intention is to start out cheap and then
> move up to something more expensive, if
> neccesary. But, I don't want to waste time
> and money on a sub that doesn't do what I
> need.

> Thanks

19" cube made from 3/4" PB or MDF. 4" port. 12" driver. 100w amp. No stuffing, grill, or spikes (although you might want to run a pair of 7/8" dowels behind the woofer in an "X" to tie the sides together. Be amazed. Have fun.

[unknownuser]

Thanks, I think I'll do just that :-)

> This is a pretty great sub, and it's on sale
> for a month yet at $33! To go with it you
> want the 100w plate amp, also on sale for
> $75. That's $108 for a 100w 12" sub.
> Put it in a 19" cube with about a
> 4"d PVC port tube, 11" long.

> Vented this works well for music AND HT. You
> can get WinISD (beta) at <A HREF="http://www.linearteam.org">www.linearteam.org</A>
> and model boxes yourself. BTW, the
> frequency the box is tuned to is known as
> its Fb (Frequency of box). The speaker's F3
> may be slightly higher, lower, or equal to
> the box's Fb depending on the driver's Qts.

> 19" cube made from 3/4" PB or MDF.
> 4" port. 12" driver. 100w amp. No
> stuffing, grill, or spikes (although you
> might want to run a pair of 7/8" dowels
> behind the woofer in an "X" to tie
> the sides together. Be amazed. Have fun.



(Originally posted by: Rob Walters)