WinISD or something else?

[zachoff]

Hey, just wondering what you DIY cab builders use for building cabs. I see WinISD come up on here a lot but I'm wondering if there's something else that's better or easier to use...

[Decker]

I use WinISD all the time. Very easy to run small changes in the box or port to get an idea of the changes in response. I haven't found anything easier. I also use Pi-Align, which you can find at the Pi speakers website. Not as easy to use, and not as easy to run minor variations, but it does give you a different approach.

[xaosbass]

Hey, just wondering what you DIY cab builders use for building cabs. I see WinISD come up on here a lot but I'm wondering if there's something else that's better or easier to use...

 

WinISD works for me everytime. allows for changes and none of the cabs I have built using the calculations from it have ever failed to work as designed!

[zachoff]

Right on, thanks guys. Another question... What kind of wood is generally used when building cabs? Birch? High Density plywood? Particle board?

[mlwarriner]

i think burdizzos pretty much always uses ISD, and generally uses high-quality plywood.

 

[rpsands]

Winisd alpha. If you use a shelf port, divide the square port length by approximately 1.5.

 

Most people recommend birch for cab building, but poplar, any AC pine plywood, and really anything is workable as long as it has one A side (or a very nice B side).

 

My recent box was built out of two 8 dollar quarter sheets of B/C that I picked through for some time.

 

That said, here are my recommendations:

1- for your first build, use 1/2" ply. I started with 3/8 and it was pretty tough.

 

2- If you're in doubt about woodworking use birch. You want at least 5 plys preverably 7. I made mine out of 3 ply and again was kinda challenging because of this.

 

 

My first choice would be 1/2" (15/32) AC (arauco or otherwise) from Lowes. Arauco is just a fancy brand name for A/C pine ply. Quality pine ply will weigh in at about 20% less than birch and is plenty tough and nice if you get to pick through it in person.

 

Second choice would be 1/2" baltic birch, third choice would be 3/8" baltic birch.

 

DO NOT USE 3/4 unless you can get poplar. it is a damn waste of weight.

[bassman1956]

I've studied numerous designs with it, but haven't built.

 

My one questions lie with cab tuning in general, not WinISD. And those are: exactly what is going on at the tuning frequency of the box, how do the speaker specs affect this, and beyond just reading corresponding numbers off the axes, what do the graphs actually show about response, why do they move with the port or size changes, etc. I have yet to see a good working explanation about tuning frequency vs air speed, port size, etc. I can graph this just fine with WinISD, I just don't grasp the entire concept of what's going on.

[zachoff]

Rad, thanks guys. I wouldn't really be doing the build. My drummer builds custom cabinets for a living, albeit kitchen cabinets. I'm sure he knows the cuts and all that stuff though and has all of the equipment. At this point, I'm trying to get my head around materials & designs. Thanks!

[rpsands]

If he knows how to build to a tight tolerance get Arauco 11/32 and a quarter sheet of baltic birch 1/2 for the baffle. It'll come out super light and very strong.

[rpsands]

 

I've studied numerous designs with it, but haven't built. My one questions lie with cab tuning in general, not WinISD. And those are: exactly what is going on at the tuning frequency of the box, how do the speaker specs affect this, and beyond just reading corresponding numbers off the axes, what do the graphs actually show about response, why do they move with the port or size changes, etc. I have yet to see a good working explanation about tuning frequency vs air speed, port size, etc. I can graph this just fine with WinISD, I just don't grasp the entire concept of what's going on.

 

 

The way the tuning frequency works in layman's terms is basically this:

 

Right around the tuning frequency you get a "bump" of gain to counteract the low end rolloff of the speaker. Typically, the lower you tune the more gentle your low end rolloff and the higher you tune the louder your cab will be on bottom but the faster it will roll off.

 

What you pay for that tuning is this:

-reduced power handling right above and below the tuning frequency

 

What this means is that your driver will have excursion peaks (that is it will have to work harder to push air) around the tuning frequency, and risk overexcursion.

 

Also, it will rapidly increase in excursion or "unload" below the tuning frequency.

 

So the danger is:

1- you tune too low, and the dip in handling above the tuning frequency screws with your ability to eq in normal lows (50-100 hz), and you lose low end sensitivity since it rolls off so early

 

2- you tune too high and the rolloff below the tuning frequency causes your driver to unload early.

 

 

For bass guitar with quality drivers (which is all you should use in custom cabs; top notch drivers are quite affordable) your tuning frequency will range from 40 to 55hz and usually not vary much from there.

 

How you choose the tuning depends on driver parameters; low QTS, low VAS drivers will usually want a higher tuning frequency and vice versa.

 

Now, the size of the box also plays a role here that I didn't discuss; a larger box generally will be accompanied by a lower tuning frequency, and vice versa. If you tune very high in a big box, the unloading under the tuning frequency will be magnified by the physics of a big box.

 

The best way to pick a tuning frequency is to use Winisd and model it.

 

1) pick your driver and allow Winisd to select your optimal alignment (usually super boom box or some such)

 

2) adjust the box size to about what you want. Winisd often inflates this to insane numbers like 15cf or so. Feel free to vary this. rule of thumb for bass drivers: at least 1cf for a 10, 2cf for a 12, and 3cf for a 15 -- will vary a lot based on driver VAS and other characteristics however.

 

3) Apply a signal equal to the thermal rating of the driver in the signal tab. Examine the SPL and Excursion charts.

 

4) Experiment with a range of tuning frequencies from 40 to 55hz and se which one makes the happiest mix of SPL to excursion.

 

Interpreting excursion graphs: The graph will look like a downward slope from left to right, with a bump right above the tuning frequency. You should aim to not be exceeding XLIM (not Xmax) above the tuning frequency or until around 40-45hz on the bottom side.

 

There are a lot of factors at play here that I've glossed over but this method will give you a ballpark idea of which tuning frequency is best.

 

Other factors

-Bass guitar does not put out a sine wave, so if you have a 500w amp chances are good you won't put out more than 250w peaks below 100hz unless you boost the hell out of your low EQ.

 

-Most amps have a built in low end shelving that affects the reality of the excursion graph below 40hz or so -- it probably isn't as bad below 40hz for most amps as Winisd makes it look.

 

-Your real aim should be to not exceed xmax, since exceeding xmax regularly can damage your driver, but comparing a sine wave equal to the thermal rating to the Xlim will approximate that, and keep you fairly safe (ballpark).

[bassman1956]

 

The way the tuning frequency works in layman's terms is basically this:*snip*

 

 

Can we get this FAQ'd?

[rpsands]

You might want to have someone go over it and clean it up and clarify, but that rough method has worked really well for me in designing and tuning my own box and reloading and tuning others.