Ported my cab

[Twincam]

Totally unscientific although I did take a kinda, sorta not very educated guess. I had a 1x15 cab that was sealed, didn't take measurements but it's bigger than say a micro 1x15 actually it's a te commando combo cab. I upgraded the speaker 250w celestion don't know the specs, but it was still weak sounding not much bass. And with my Aguilar ag500sc which is mid forward I thought the tone was not great, with the previous abm 500 it wasn't bad actually at lower volume but that's different amps for you.

So I thought I would add some ports I was going to go with a single 4 inch port however it seemed to really suck in air and out and I know that isn't a ports job and from putting my hand over ports of various amps in the past it didn't feel right. The cab did sound better. So I put in another 4 inch hole. Which really helped, cab is louder and the bass is a lot deeper. However it is a little more boomy not bad though it's very useable now.

I was going to ask for help and get all the cab measurements and speaker specs together but thought since it's only a little experiment that cost me nothing I would wing it.

[3below]

Next construct plywood port cover (e.g. 5" x 5" square), and screw this down so that it can be rotated to cover the port varying amounts. Try different port blocking until you find the optimum tuning that removes the booming. At that point screw the port cover down.

[JapanAxe]

Alex? Bill?

[Beer of the Bass]

Without knowing what the volume of the cab is, it's impossible to say what tuning frequency you've ended up with, but at a guess, two 4" ports 18mm long would come out much higher than any tuning used in a bass cab. I had a quick play around in WinISD, and it comes out as anywhere from 80Hz upwards depending on the box volume.
Such a high tuning is likely to give you a large bump in the midbass (the boominess you're hearing), but will also massively decrease the power handling below the tuning frequency, risking blowing your driver. The port tuning could be lowered by putting tubes in the holes, so it might be worth doing some research to figure out what would work with your box and driver.

Edited May 1, 2016 by Beer of the Bass

[Twincam]

[quote name='3below' timestamp='1462134233' post='3040572']
Next construct plywood port cover (e.g. 5" x 5" square), and screw this down so that it can be rotated to cover the port varying amounts. Try different port blocking until you find the optimum tuning that removes the booming. At that point screw the port cover down.
[/quote]

Yes might be a good idea.

[Twincam]

[quote name='Beer of the Bass' timestamp='1462135481' post='3040587']
Without knowing what the volume of the cab is, it's impossible to say what tuning frequency you've ended up with, but at a guess, two 4" ports 18mm long would come out much higher than any tuning used in a bass cab. I had a quick play around in WinISD, and it comes out as anywhere from 80Hz upwards depending on the box volume.
Such a high tuning is likely to give you a large bump in the midbass (the boominess you're hearing), but will also massively decrease the power handling below the tuning frequency, risking blowing your driver. The port tuning could be lowered by putting tubes in the holes, so it might be worth doing some research to figure out what would work with your box and driver.
[/quote]

What about a tube within a tube I could vary the length of it and go by ear. This is just a little project I'm not wanting to go to mad on it. Although the boominess isn't that bad I've heard much worse cabs but it would be nice to do a bit better.

Edited May 1, 2016 by Twincam

[Phil Starr]

It would make more sense to just work out the internal dimensions of the cab and tell us, then someone will work out the best port length and you won't end up with a damaged driver. You've now got two convenient holes to put your tape measure through

At the moment you've got it tuned too high with the problems you've been told about.

[Twincam]

[quote name='Phil Starr' timestamp='1462178526' post='3040755']
It would make more sense to just work out the internal dimensions of the cab and tell us, then someone will work out the best port length and you won't end up with a damaged driver. You've now got two convenient holes to put your tape measure through

At the moment you've got it tuned too high with the problems you've been told about.
[/quote]

There would be no fun in that. But of course you are correct I shall get the internal measurements.

[3below]

[quote name='Twincam' timestamp='1462135484' post='3040589']
Yes might be a good idea.
[/quote]

Then again it might be better to ignore my advice and take advantage of Phil Starr's rather more scientific offer

[Twincam]

[quote name='3below' timestamp='1462194916' post='3040957']


Then again it might be better to ignore my advice and take advantage of Phil Starr's rather more scientific offer
[/quote]

Well it's just a bit of fun this but in the spirit of not blowing the driver then best do it correctly as possible without going mad.

[Beer of the Bass]

If you're attached to the idea of winging it without looking into things too deeply, you could just measure the internal volume of your box, then use this calculator to figure out what length ports would give you what tuning. The open holes you have at the moment will behave like a port with the length the thickness of the wood.
[url="http://www.linearteam.dk/default.aspx?pageid=ventcalculator"]http://www.linearteam.dk/default.aspx?pageid=ventcalculator[/url]

Most bass cabs are tuned anywhere from 40Hz to 55Hz, so if you shoot for somewhere in that range it'll be an improvement on what you've got at the moment even if it's not completely optimal.

[Twincam]

[quote name='Beer of the Bass' timestamp='1462195886' post='3040973']
If you're attached to the idea of winging it without looking into things too deeply, you could just measure the internal volume of your box, then use this calculator to figure out what length ports would give you what tuning. The open holes you have at the moment will behave like a port with the length the thickness of the wood.
[url="http://www.linearteam.dk/default.aspx?pageid=ventcalculator"]http://www.linearteam.dk/default.aspx?pageid=ventcalculator[/url]

Most bass cabs are tuned anywhere from 40Hz to 55Hz, so if you shoot for somewhere in that range it'll be an improvement on what you've got at the moment even if it's not completely optimal.
[/quote]

Why didn't I know about this simple program before. Indeed not optimal as you say but will do in this case. Thanks

[Twincam]

Hmmm ports have to be deeper than my cab to get to 55hz

[Painy]

[quote name='Twincam' timestamp='1462199007' post='3041008']
Hmmm ports have to be deeper than my cab to get to 55hz
[/quote]

You'll have to make more holes in the back for them to stick out of then

[Twincam]

Ok have another issue apparently to prevent port whistling I can only tune down to about 66hz.

[Maude]

I'm no expert but I think the port can can have bends in it, if the cab isn't deep enough for the needed port length it can have a right angle bend in it and go up, down or sideways, whichever is most convenient.
Hopefully someone can confirm that .

[Phil Starr]

[quote name='Twincam' timestamp='1462199007' post='3041008']
Hmmm ports have to be deeper than my cab to get to 55hz
[/quote] Go to a single port re-run the program and block off the other port

Edited May 2, 2016 by Phil Starr

[JapanAxe]

[quote name='Phil Starr' timestamp='1462220055' post='3041268']
Go to a single port re-run the program and block off the other port
[/quote]

Any port in a storm.

*fetches coat*

[RandomBass]

[quote name='JapanAxe' timestamp='1462221180' post='3041291']


Any port in a storm.

*fetches coat*
[/quote]
Ferry ferry funny, that.

[Twincam]

Decided to run to long ports they stick out the back, looks a bit errm homemade. But good thing I'm in a punk thing it will fit right in.

Also as an experiment I'm running two port lengths one tuned 16.5hz lower which is a fair bit longer than the other. Bit late to test it now or is it. My gf is asleep on the couch so I best not unless I want to get instadumped.

Edited May 2, 2016 by Twincam

[Roland Rock]

Twin exhausts! Pics please!

[Twincam]

Pics no way! It looks ridiculous think of an old tatty green Trace Elliot combo with the head removed, a celestion sidewinder and two huge 4 inch white ports sticking out the back, one being significantly longer than the other.
I really should of angled the tubing inside. I am trapped thinking it looks totally stupid and half of me thinks it looks pretty mean. Be a nightmare to transport!!!

Edited May 2, 2016 by Twincam

[Twincam]

Still up reading about cab port theory. Very interesting and it's one of those things I seem to understand to a degree which is odd as there is a fair bit of mathematics involved but I get the basics I now have enough knowledge to be.... stupid haha.

Anyhow my different sized ports will be inefficient if my understanding is correct and when the higher tuned port goes under its tuned frequency then the lower tuned port will hardly work at all, again if my limited understanding is correct. Up until then the higher tuned port will dominate the lower tuned one neither will be as loud as they should if using two ports of equal size and tuning. I'm guess you can have two very very slightly tuned port lengths but it would be only a very small amount and not worth the trouble.

So I will give the cab a trial tomorrow but going to cut and extend the ports, this time inside the cab so they are equal and don't stick out the back stupidly.

[Maude]

I'm confused.
Are your ports now going straight through the cab now if they stick out the back? If so then you cab is now sealed again just with a smaller internal area surely, unless I've misunderstood you, which is quite likely .

[CamdenRob]

Could you extend the ports, bend them over the top, then flare them out a bit so it looks like a giant double trumpeted gramophone?

Edited May 3, 2016 by CamdenRob