Three Way, Anyone?

[tinmanchris217 10+ year member]

So I have a fairly large SPL box (4.5 cf for 2-10's), and I want to gut it and do something unique. (i've heard of port plugs, but nothing that was designed from the ground up to be a multi-banger)

Basic idea is to strengthen the baffle, and create a hot-swappable port setup.

3 Tunings = fun for any occasion! //content.invisioncic.com/y282845/emoticons/partytime.gif.c93957d22b3fb208098e423485fd0404.gif

1) Go Deep: f3 = 19 Hz //content.invisioncic.com/y282845/emoticons/eyebrow.gif.fe2c18d8720fe8c7eaed347b21ea05a5.gif, using a low tuning (22 Hz)... port area will be kinda small, but according to BassBox, it'll grind out the lows.

2) Go Flat: perfectly flat response out to ~35 Hz, using Fb = 30 Hz and 1.5 cf IV.

3) Go Loud: test-n-tune with multiple port nubs, ~100 sq. in. of port area. Designed to peak around cabin gain, keep a low-ish impedance.

Reason for posting: I need advice on making the ports easy to swap, reliable, and strong.

Thinking T-nuts and thumbscrews, or maybe a track for them to slide into and lock down.

Suggestions?

Click to read more...

 

[Supergumby5000 5,000+ posts]

search, this has been done many many times. I know of two local guys with boxes like that.

 

[tinmanchris217 10+ year member]

I'll spend some more time searching, but can you point me towards an example?

 

[tinmanchris217 10+ year member]

So apparently back in February, DMan attempted it, but I never found results. Terra has done it, and most others were "meh" over the idea, as if it were nothing special.

2 methods that seem to recur:

- T-nuts/Threaded inserts for swapping without stripping.

- Aeroports with various tuned pipe, duct taped in place.

Both seem valid, but I have yet to see any pics, besides this guy at SSA Linky

 

[tinmanchris217 10+ year member]

So it may not be original or special... but it's new to me, and any wisdom from the gurus would be welcomed.

Here's a pic of the response curves for the 3 tunings.

Low = 1.6 @ 22 (yellow)

Flat = 1.6 @ 30 (red)

Loud = 3.0 @ 48 (orange)

 

[dappa5 10+ year member]

make ports any size and shape but attach like this

 

[tinmanchris217 10+ year member]

Many thanks, my good man.

So using threaded inserts, over a predefined area... simply bolt it in, with a layer of foam tape (gasket). That's exactly what I needed to know.

Is there a recommended overlap distance for the edges on Mr. Adjust-o-port? I'm betting 3/4 to an inch is plenty for the normal tunings, and more for the SPL ports.

Looks like it's time to "do work".

 

[dappa5 10+ year member]

yes you can do two rows of threaded inserts and just use inner set for daily and use both for boom boom i'd do @ least 2-3" for the spl port

 

[ciaonzo 5,000+ posts]

So it may not be original or special... but it's new to me, and any wisdom from the gurus would be welcomed.
Here's a pic of the response curves for the 3 tunings.

Low = 1.6 @ 22 (yellow)

Flat = 1.6 @ 30 (red)

Loud = 3.0 @ 48 (orange)

Keep in mind these curves represent a model for the home atmosphere. Enable the in-car response to give you a better idea of flat and so forth.

 

[tinmanchris217 10+ year member]

Cause I'm a nerd, and enjoy Google Sketchup:

note: port is not to length, but area is appropriate.

 

[tinmanchris217 10+ year member]

Keep in mind these curves represent a model for the home atmosphere. Enable the in-car response to give you a better idea of flat and so forth.

You are most correct.

What is an appropriate setting for in-car response? I remember hearing somewhere a rule of thumb, +6 db/oct rise cornering at 50-55 Hz... but that's most likely wrong.

What is a rough estimate of cabin gain?

 

[ciaonzo 5,000+ posts]

You are most correct.
What is an appropriate setting for in-car response? I remember hearing somewhere a rule of thumb, +6 db/oct rise cornering at 50-55 Hz... but that's most likely wrong.

What is a rough estimate of cabin gain?

The standard for that program (BBP6) is 12dB beginning @ 50hz but you can import your actual transfer function if you have the file. It's pretty helpful for the most part with the default in-car setting.

 

[tinmanchris217 10+ year member]

So here's another configuration for the hot-swap port idea. This is the SPL configuration, with 100 sq in of port area, and ~3 cf internal volume... for my 2-10's.

Should be easy to adjust the port length, by pulling the port, and cutting the 3 sides down, a 1/2" at a time.

 

[spltuscon 10+ year member]

This is my version...keep in mind I'm an SPL guy and external is louder for me.

You could do the same thing except with the port internal. Its two layers thick, the inner layer is cut 2.5" smaller than the outer one and the box has a matching hole so that it sits flush (on the inside) when installed. Its done with a jasper jig so that its totally accurate and easy to repeat for multiple ports. I had 3 for this box too, 32hz (daily but I hated it), 46 hz (streat beat), and 50hz (burp).

I'm not suggesting you do the Octoport like me (thats mine //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif) but rather the mounting plate portion.

I just used screws when I did mine (just to test the concept) but if I build another one it would use t-nuts (glued in).

Good luck, it's definitely a cool idea that you don't see very often.

 

[tinmanchris217 10+ year member]

HOLY CRAP! I love it! //content.invisioncic.com/y282845/emoticons/bowdown.gif.b85b23b82970bd22fb6b549c3392f016.gif

:fyi:You can't be an SPL guy, you rounded your corners, and have no visible screw holes. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

I'll analyze this when I get home, and see what I can SketchUp, for an external port setups.

Philosophical thought of the day: "Quality designs should never be stolen, but quality ideas can live forever in the masterpieces of the future." That is all.

Thanks again for the pic and explanation.