Is building a bass cabinet really this easy?

[sean79]

Very simply, do you just have three parts?
1. The box (probably closed back)
2. The speaker(s)
3. An input jack

Are there any other parts needed?

I know it has to be more complicated/confusing. Let's say, for example, I want to build a 2x10 bass cabinet. If I get two 10 inch speakers rated 150 watts RMS at 8 ohms and wire them into a 2x10 cabinet, does that mean the cab can handle 300 watts RMS?

And... can't one wire the two speakers in various ways to get different ohm ratings... down to four or up to ?????? Can they be wired to different input jacks to give a person options (based on the amp)?

And... I've seen the charts and tables that discuss porting and sizing of cabinets, but I can't make heads or tails of that confusing stuff. For a simple first build, do I need to worry about porting a 2x10 bass cabinet?

As always, any advice, input, and/or suggestions appreciated.

[winny pooh]

Originally Posted by sean79

Very simply, do you just have three parts?
1. The box (probably closed back)
2. The speaker(s)
3. An input jack

Are there any other parts needed?

I know it has to be more complicated/confusing. Let's say, for example, I want to build a 2x10 bass cabinet. If I get two 10 inch speakers rated 150 watts RMS at 8 ohms and wire them into a 2x10 cabinet, does that mean the cab can handle 300 watts RMS?

And... can't one wire the two speakers in various ways to get different ohm ratings... down to four or up to ?????? Can they be wired to different input jacks to give a person options (based on the amp)?

And... I've seen the charts and tables that discuss porting and sizing of cabinets, but I can't make heads or tails of that confusing stuff. For a simple first build, do I need to worry about porting a 2x10 bass cabinet?

As always, any advice, input, and/or suggestions appreciated.

The easiest is to take an existing cab and duplicate the measurements, the porting stuff also drove me insane but i forgot about it as its ot as necessary as it is for your bass cab.

The hardware costs are normally higher than you may think but still cheap, I made a 2x12 cab for my plexi and bought metal corners, a handle, rubber feet and grill cloth(the priciest), plus an input jack and wiring for the speakers.
I also had to get a pot of glue and a couple of sheets of tolex/vinyl to cover with. If you are careful and take care when and where to cut the covering is simple, i did in in my garage with a rolling pin. Great thing is that you can choose your cosmetics.

You will also have to cut the baffle board and find the threads that you need
to install the speakers with, but you could just use sturdy screws into the baffle.
You will of course need a router to round off all the edges and some sanding before the glueing part.

And yes if you have two speakers at value 150W then you have a 300w cab, how you then wire the speakers will determine the ohms, this is important to decide before you get the speakers. See what your amp puts out first.
As for the wiring, there are plenty of good articles on the net than can clarify for you.

Good luck

[Telenator]

The right dimensions are critical. Building the cabinet to the wrong dimensions can cause "phase cancellation" inside the cabinet before the sound ever gets out.

As suggested above, copy the dimensions of a cabinet that you really like. It will make a HUGE difference in the sound.

[sean79]

Thanks winny and Telenator. I don't have access to any 2x10 bass cabs around here to know if I like them or not (I'm about 2 hours from the closest real music store). Maybe I'll check online and see what I can find.

Is the porting just a hole in the front baffle - or is there more to it than that?

Appreciate the replies.

[marshman]

It seems to me that the internal dimensions of most bass cabs are dictated, according to manufacturers, by "thieil-small" parameters and such. Porting is also a serious 'science', and to properly utilize the speakers, which all have slightly different parameters, cabs and ports have to be constructed to suit the speakers.

That said, I've always kinda figured that the long, front ports were a 'cheat' to the porting issue, and padding the interior would negate a few 'phase cancellations' issues, so in all likelihood, you could probably copy a favorite 2x10 with favorable results.

And yeah, if you have two 8 ohm, 150 watt speakers, you should be able to wire it as 4 ohm -OR- 16 ohm, but it should be capable of 300 watts either way. Someone smarter than I should be able to tell you if you can rig it to run 4 ohm or 16 ohm from a single jack plate with 2 jacks. It might be possible to do one jack and a switch.

[Telenator]

If my thinking is correct, you can get a 300 watt rating by wiring the speakers in series, but it would still be 150 watts if they're wired in parallel.

[chriscrob]

And yeah, if you have two 8 ohm, 150 watt speakers, you should be able to wire it as 4 ohm -OR- 16 ohm, but it should be capable of 300 watts either way. Someone smarter than I should be able to tell you if you can rig it to run 4 ohm or 16 ohm from a single jack plate with 2 jacks. It might be possible to do one jack and a switch.

It IS possible, but I'm not sure where you get a switch suitable for that...I would worry about using just any switch.

[sean79]

Originally Posted by Telenator

If my thinking is correct, you can get a 300 watt rating by wiring the speakers in series, but it would still be 150 watts if they're wired in parallel.

So, what would that do to my impedance (I think that the "ohms" word)... series at 300 watts or parallel at 150 watts?

Thanks again to all who have given me suggestions.

[chriscrob]

Quote:
Originally Posted by Telenator View Post
If my thinking is correct, you can get a 300 watt rating by wiring the speakers in series, but it would still be 150 watts if they're wired in parallel.
So, what would that do to my impedance (I think that the "ohms" word)... series at 300 watts or parallel at 150 watts?

Thanks again to all who have given me suggestions.

I don't think this is accurate. The sound will run through all the speakers either way and as such the maximum wattage for the cab will be the the sum of the individual speakers maximum; in series or parallel 300 watts.

The impedance is different; this is a measure of resistance. The cabs impedance must match the output from the amp or you risk burning up your amp. The power handling isn't as important; if your amp puts out more than the cabinet is handling you will get speaker distortion and eventually blow your speakers. For bass you will probably not want speaker distortion so you will ideally use this 300 watt cab on something rated at (or preferably below) 300 watts.

This will help you understand series and parallel wiring.

http://colomar.com/Shavano/spkr_wiring.html

[Ben Harmless]

Originally Posted by chriscrob

I don't think this is accurate. The sound will run through all the speakers either way and as such the maximum wattage for the cab will be the the sum of the individual speakers maximum; in series or parallel 300 watts.

+1. The electrical resistance is shared by the two (in the case of a dual driver cab) resistors/speakers.

I'd also like to point out that there are indeed some legit concerns about the size and shape of bass cabs, but the phase cancellations you're most likely to encounter in a reasonable sized cabinet probably won't instantly make it complete crap. They're more likely to simply weaken the response in specific frequency bands. Yeah, you can bone yourself, but that doesn't mean it takes an advanced degree to build a decent cab. IIRC, the popular Genz Benz 2x12 guitar cabs were engineered carefully, but there were also a whole heck of a lot of prototypes build while the company was actually tuning the ports by ear rather than by calculator.

[Mark Davis]

Back in the mid 70's we made our own cabinets from some plans we got from JBL. They turned out fantastic. You might look around on the web see if you can find those JBL speaker box plans.

[sean79]

Originally Posted by Ben Harmless

I'd also like to point out that there are indeed some legit concerns about the size and shape of bass cabs, but the phase cancellations you're most likely to encounter in a reasonable sized cabinet probably won't instantly make it complete crap. Yeah, you can bone yourself, but that doesn't mean it takes an advanced degree to build a decent cab. IIRC, the popular Genz Benz 2x12 guitar cabs were engineered carefully, but there were also a whole heck of a lot of prototypes build while the company was actually tuning the ports by ear rather than by calculator.

Genz Benz NEOX-210T 2x10" Bass Speaker Cabinets Specifications:

* Impedance: 4 ohms
* Crossover point: 4kHz
* 21-1/4"W x 25"H x 16-1/2"D

So... if I make a box to these dimensions and mount and wire my speakers properly, it shouldn't sound like ass??? I know they have the porting stuff figured out, and I don't. But I don't expect to build a super-great cabinet the first time out. However it turns out, I don't really have anything to compare it to... so it would probably have to be real bad for me to notice it was bad.

What's that 4kHz crossover point on the Genz Benz cabinet? Is that something else I have to worry about?

And... the "porting" on that Genz Benz cabinet looks different than some of the others I've seen in pictures. Do the round ports have some kind of tube in them? Are they just "vents" for air and/or pressure to escape?

I looked around the web a little for some JBL plans... didn't find any, but I may keep looking.

Thanks again.

[Ben Harmless]

Well, I was referring more to the 2x12 Genz Benz guitar cabinets that are praised for their low end.

Many ported cabinets are built with port inserts that reach several inches into the cabinet, so unless you've got the same hardware, it may turn out at least slightly differently. That, plus the cabinet was designed with specific drivers in mind.

Off the top of my head, I'm assuming that the 4k crossover point is where the passive crossover between the low end drivers and the horn is fixed.

Hehe. And you won't find me guaranteeing that anything won't sound like ass - ever. There are too many variables to promise that.

My point wasn't really that Genz Benz has an unbeatable design, but that sometimes just listening can play as much of a part in turning a bass enclosure as mathematics. Unfortunately, the average TDPRIer doesn't have the resources for extensive prototyping...

[ibobunot]

Bill's Best Little Bass Speaker Cabinet

[sean79]

Originally Posted by Ben Harmless

Off the top of my head, I'm assuming that the 4k crossover point is where the passive crossover between the low end drivers and the horn is fixed.

Okay... this is where I prove my stupidity:
I have no idea what that means... passive crossover between the low end drivers and the horn??? Seriously, no clue.

I had seen the site with Bill's little bass cabinet, but it's not a 2x10. A lot of these guys sure do make it look easy though. Thanks again.

[Ben Harmless]

Originally Posted by sean79

Okay... this is where I prove my stupidity:
I have no idea what that means... passive crossover between the low end drivers and the horn??? Seriously, no clue.

I had seen the site with Bill's little bass cabinet, but it's not a 2x10. A lot of these guys sure do make it look easy though. Thanks again.

The horn is the smaller driver (aka tweeter) that's mounted in the cab along with the two 10-inchers. The crossover is a little component that mounts inside the box which separates the speaker-level signal (from the amp) by frequency. Everything over 4k is sent to the horn and everything below is sent to the 10-inchers. The reasoning here is that the two different driver types can handle those respective frequency ranges much more efficiently than either one can handle the full range. Lots of bass cabs are built with horns, and some have controls for adjusting the amount of the highs that the horn actually puts out, (including zero) so that you can somewhat set the brightness to taste. Many other bass cabs are built without horns at all - such as the classic Ampeg 8x10 "fridge" cab.

Overall, the horn is just an attempt to offer greater high-end definition. It's not always necessary, and I don't personally feel like I need one in a bass cabinet.

[sean79]

Thanks Ben. I thought the "crossover" might be something like that, but I didn't think that Genz Benz cabinet I was looking at had anything in it other than the two 10 inch speakers. As long as it's something I don't have to worry about, I'm sure I can handle it. Appreciate the explanation.

[Dacious]

Firstly: speakers' power handling is cumulative, provided they are all the same impedance. If they are all the same efficiency you will get similar ouput. So whether you connect series, or parallel, or series-parallel you will get 100w power handling out of 4 x 25 w speakers.

Secondly - if you are going to copy a cabinet, there are a number of parameters you should check if you are going to use a different make/model of speaker to what the cabinet has installed stock ensure they are compatible. As well as choosing your cabinet resonance, a number of other parameters like the resonant frequency of the speaker. With guitar speakers where we don't dislike distortion we might not care if the resulting cabinet compresses or supresses certain bandwidth.

With bass or PA cabs, you do. You probably want as flat a response as possible. The speaker driver has parameters like volume, the way it behaves electrically and mechanically, resonant frequency, its' upper and lower usable freqs and even things like the internal bracing of the cabinet are a factor. Just putting in a different speaker or putting it in a changed cabinet dimensionally may alter want you want. If the enclosure is oversize for the power of the amp and driver, you will lose response in the bottom.

There are programs on the web which will help design a cabinet. You need a bass reflex design preferrably for bass, rather than a sub-type which is optimised for very low freqs.

If you are a slapper, you probably need to design in a horn with a crossover- otherwise you can cook very expensive bass speakers with the short, hi-freq repetitive motions.