2 Woofers = 2 x Volume = What Port?

[sdclc126]

Hi,

If this has been answered before (maybe in Subwoofers) I apologize, but I couldn't think of good keywords to search with...

I know that if you use two woofers, either midwoofers or for "dedicated" bass, you should double cabinet volume to achieve the same tuning as for a single woofer. But what then happens with port size calculation? Does that also double? Or?

Thanks.

[richie00boy]

Everything doubles. You simply use two of the ports that you specced for the single size box. Or one port of the same cross sectional area.

[sdclc126]

Thanks Richie,

It's nice that it's that simple and straightforward - makes for a short thread though.

[Dave Bullet]

I don't think it is simply 2 ports at the same length as a single port (unless the spreadsheet I am using is wrong). I don't have the formula handy. To maintain the cross sectional area by adding another port - don't you have to almost double the length of both ports for the same tuning frequency?

[richie00boy]

No it's simply a double up on everything, port length remains as per a single woofer box. Think of it as two single boxes joined siamese style.

Your last sentence does not make sense by the way, but I know what you are trying to say.

[Jay_WJ]

Originally posted by Dave Bullet
To maintain the cross sectional area by adding another port - don't you have to almost double the length of both ports for the same tuning frequency?

Dave, what you said is correct only when the box volume stays the same. If the box volume is doubled, you can achieve the same port tuning frequency by adding a port of the same length.

[Svante]

Yes, two drivers, double volume, two ports of the same length is correct. However, the port needs to be slightly shorter if a single port is used due to that the end correction becomes larger for a larger diameter port. Actually, if the two ports are placed close to one another, there will be an effect in this direction too since the ports share co-oscillating air.

[sdclc126]

Originally posted by sdclc126
It's nice that it's that simple and straightforward - makes for a short thread though.

Maybe I spoke too soon.

[Dave Bullet]

Ooops - yeah that was a bit dumb of me - cheers guys.

[augerpro]

Originally posted by Svante
Yes, two drivers, double volume, two ports of the same length is correct. However, the port needs to be slightly shorter if a single port is used due to that the end correction becomes larger for a larger diameter port. Actually, if the two ports are placed close to one another, there will be an effect in this direction too since the ports share co-oscillating air.

Could you elaborate on end correction please?