Need help from the Port guru's (Dayton III)

[dawg1161]

Hello to all it has been awhile, I am in the process of building my second set of these speakers. I built the bookshelf version the first go around. Now i am building these as towers. My question is in the original design the port is 8" long 3" inside diameter for what i believe would make it 38-20000hz. Using these as my mains and my receiver set so these speakers are small (using a sonosub for bass) if i use a 3" i.d port 5 1/2" long what will that make these speakers.

[joecarrow]

Sorry, I think the Dayton III is a popular old design using Dayton Classic drivers, but I don't have a link immediately available.

We can help, but we still need to know
1) Internal volume of the cabinet
2) The woofer model

We specifically need the woofer's Thiel Small parameters in order to predict response.

If I had to give you a rough answer, though, I'd say that your port tuning would increase, you would get less bass extension and I would venture to guess there would be a bump at the tuning frequency. Unless your woofers are running out of excursion, it doesn't seem necessary or desirable to alter the existing design.

[ThomasW]

If you're setting the speaker to 'small' why would you bother porting it?

[dawg1161]

Hello Thomas, I was trying to stick to the design but why wouldn't it matter when you have them set to small ? Will that change anything else ? I have my first set hooked up now (bookshelf) i guess i could just stuff the port to see if there is any difference.
My receiver is a Yamaha and i belive the sub out is crossed at 90hz i'll check on that also. Again thanks for helping.

[ThomasW]

but why wouldn't it matter when you have them set to small ?

It wouldn't matter because there wouldn't be any port output at 38Hz with the use of a 90Hz crossover point.

[engr_dave]

Dawg,
I built a pair of D3s as ported towers for my dad. He's running them without a sub and was thrilled with their sound.

I wouldn't change Wayne's design - especially if you are building them as towers. IMO the only reason to go sealed or raise the tuning is if you want smaller "bookshelf" boxes. As Thomas points out, you won't be using the last octave of their capability if you set them up as "small" but that's OK. It's a good thing to have the speaker F3 well away from the sub crossover frequency (unless you are deliberately matching a shallower-slope high pass with the natural speaker rolloff).

[dawg1161]

Thank you guys , i was trying to find out what the F3 would be with a 5 1/2" port instead of an 8" port. I will just build them as they were designed to be built. I was just wondering how much higher the tuning would be? These speakers do sound awesome, I wish now that i would have built them as towers instead of being anal and following the cabinet design when all i had to do was keep the 1.17cft volume.

[dawg1161]

Quick question, if the cabinet calls for 1.17cft and i made a mistake and its 1.13 will that make a big difference? i can't fix my mistake.....inside demensions are to be
8"W x 21"H x 12"D and i made mine 8x20.5x12 i have also adjusted the speaker layout on the baffle moving everything 1/4" up from where they were suppose to be. Baffle looks great ?

[Sefferdog]

Don't sweat the minuscule difference in size.

[engr_dave]

Yup. No worries on the size snafu. They will work fine. Here's what my dad's ended up looking like...

[dawg1161]

Thanks for the words of encouragement