1x15 Cab Re-Build

That is some seriously good work. Tell us about the sound when you get to use it.

 

Very nice project. The finished cab is so much nicer looking and lighter too. Did you use anything for damping inside the box?

 

You need to ensure that not only do you duplicate the cabs internal volume, but it's porting as well.

Anything less is nothing more then a crapshoot.

 

normally you're right, but it looks like this cabinet was sealed, and it sounds like they made it to imitate the old cab's internal volume. On the whole I really dig the vibe coming from that cab!

 

This line in the OP sounds like it had a shelf port, could be wrong though.

 

Ahh, good eye, I just took a quick look at the photograph, the first one is from the old combo, and didn't really see it, but on a second look, you're right - and he also mentions the shelf port too. That should definitely be copied into the new cabinet.

 

I have used un-backed fiberglas insulation, it works but a lot of people prefer other things that don't cause you to itch after handling. There are many ways to go about this and I'm not an expert. If you are interested I suggest the search key as there is a multitude of discussion on the subject.

 

Most often the bracing in a cabinet has nothing to do with the strength of the cabinet, but is there to keep the panels from vibrating, causing uneven response in the cab's performance. So you might want to consider some internal bracing.

Also, the ports were there to control the resonant frequency of the system, so you won't get the same frequency response without them. That's not to say that you won't like it without a port, but it's behaviour will be different. I used to design and build custom speaker systems, so I do know about these things.

 

Nice cab! Love the new finish and the fact that it's lightweight. Please report back after live performance, I'm intrigued.

 

First I would be concerned about the back panel. I would consider a diagonal brace, much like your old cab. The sides may not need any bracing. Pound them with your fist and see if you get a boomy drum effect. If so, you probably need to brace them too.

You can use multiple holes rather than one slot for the port, as long as the holes aren't too small, and as long as they add up to the correct area. One-inch holes are too small - they are likely to whistle, and won't work as well as larger ones. But it's not clear from the photos if the old cab had a sort of shelf at the port - that's important as it is a component in the tuning of the cabinet. All the dimensions are critical - the volume of the cabinet, and the volume contained in the port section. Together with the resonant frequency of the speaker they determine the low-end frequency response of the system.

 

yeah, it would be easiest just to make the 2" shelf port IMO - the length of the port is a part of its design. Have you ever held a bottle to your mouth, and blew across the opening of the bottle and heard a tone? The back end of the speaker (inside of the cabinet), is doing a similar thing to that port as you are to the bottle, except the port is tuned to a specific frequency. This helps to improve its low end capabilities.

Changing the length, location, and format of the port can change the performance in unpredictable ways if you don't know what you're doing. I'm not saying it's impossible to tune some round ports to the same frequency, or that it would sound different or bad, it's just a lot simpler to mimic the exact shelf that they're using than to try to reinvent the wheel. Of course, logic seems to dictate that the same port area with the same port length would lead to at least a similar tuning in a different format/shape, but I really don't know that one.

If you can, use a router to get a bit of a radius onto the outside edge of the shelf port on the baffle, this would help reduce chuffing a bit, if it ever was a problem.