2 Identical subs but each ported at different frequency?

[drew.haynes]

I have a friend with 2 10" Type R subs. Currently they are in a crappy prefab box. My Type R 12 single sounds better in my homemade box.

The weird question I have is... could you technically port each 10" sub at a different port frequency? Maybe port one to 31hz and one to 34hz?

What would that do?

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[skydeaner 10+ year member]

This would cause differences in group delays betweeen the two woofers causing cancellation to some extent. Can it be done? Yeah... but it's not ideal. Maybe look into 6th order bandpass with the woofers in the same airspace, but i assume even with 10"ers it would be a huge enclosure.

 

[audioholic 5,000+ posts]

This would cause differences in group delays betweeen the two woofers causing cancellation to some extent. Can it be done? Yeah... but it's not ideal. Maybe look into 6th order bandpass with the woofers in the same airspace, but i assume even with 10"ers it would be a huge enclosure.

It would mean differing group delays between the ports, that is true. But no more so than a 6th order bandpass offers. And less than the group delay between the port and speaker cone that the ported enclosure will have anyway.

IMO the larger issue is the freq response. Generally speaking, you'd have a double peak in output, much like a 6th order bp offers. But beyond that, I think you'd find over all freq response to be more erratic and less predictable than you would in a system with identical tuning points. Heavy processing could make up for that, for the most part, but I really dont see the point of going through all that trouble just to get a double peak in output, when the point is suppose to be a flat response.

 

[michaellane 5,000+ posts]

just build a nice box for them

 

[drew.haynes]

Thanks guys.. that all makes perfect sense. I personally have a Type R 12. I built the Alpine "Optimum Sealed Box" for it: like a .75cu box. It was okay. Then I built a 2.35cu vented box @ 33hz. WORLDS better. That got me thinking... my friend has had two Type R 10s in a ported box for years... and the box is prefab... wonder how much better it could be in a new box. He's out of state right now, but when he is back I am at least gonna measure his box and see what tuning and volume we're looking at to see HOW MUCH it *****.