Need help calculating port length with new box

[justafifteen 10+ year member]

I'm designing a new box that's pretty close to my old box. The new one is 2" narrower, but 1.5" deeper, so I don't know how to adjust the port. Here's some pictures:

Old box:

New box:

Do I just reduce that little 3" turn to 1.5" to achieve the same tuning of 38hz?

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[THATpurpleKUSH 5,000+ posts]

The tuning on your old box is 35hz before sub displacement, and when you drop the cu/ft down a little to compensate for sub displacement it only raises to about 36. Your new box is just a hair smaller, so cutting 1.5 off that last 3inch piece puts you within .05hz of where you were at before with the old box. So you should not use the last small piece and might have to shorten the main inner port wall to get to 38hz.

This should help you: RE Enclosure Calculator

 

[justafifteen 10+ year member]

Well, I say 38hz because DJ from Audioque emailed me the instructions to build that box, and he mentioned that it was 38hz -- but whatever the box is actually tuned at, I want.

So to achieve the same tuning, I just need to shorten the port by 1.5" to compensate for the 1.5" depth addition?

p.s - I know of the RE tuner but I also know it's usually off by 1-2hz -- plus it doesn't put a 45* piece in the port, so it's registering the port as longer & dropping the "tuning"