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Help a new guy with a DIY bass cab please.

B

Beady_Eyed_Bob

Jul 23, 2020
14
13
65
Memphis +/-
#1
I'm a very young old guy who started playing guitar 5 years ago when I retired. About a year ago my older brother gave me a Fender SK100b bass head. I thought I might make it into a guitar amp project..........

So anyway, since that bass head was still sitting around un-molested, I thought I'd buy a bass guitar and give it a try. Yesterday I bought a Ibanez ASB140 bass from Guitar Center. Should be at my local GC in a few days.

THE QUESTION!: I thought I could just pop a 12" bass speaker into an empty 1x12 cab I have, so I bought a Peavy Darkmatter DM112 Plus (Invalid Link Removed) directly from Peavey. Mostly I picked that speaker to ohm match the head and because of its wide freq. range of 45Hz-5kHz. Am I wasting my time/money here? Should I just abandon the Fender SK100b, return the speaker to Peavey and use the refund to purchase the Peavey Max 208 or something in their MAX line?
I'm never going to be playing anywhere other than a 10x12 bedroom, unless I get good enought to play in the living room! If I can get a decent "Another One Bites The Dust" from that speaker I bought, I'll settle for that.
 
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#2
The answer is yes, but hold on tight for just a bit, because this thread will get a lot of comments worth reading. Including from me. ;)

To get started, what are the interior dimensions of the cab, and if it has a port, what are its interior dimensions? It might be possible to make some educated guesses about how this rig will behave.
 
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#5
Welcome to TB!
If your empty cab was made for guitar it probably won't be good for bass, especially if it's open back.
Dropping a random speaker into a random box is an almost guarantee of disappointing results. Bass cabinets are designed to work with a specific speaker's Thiele-Small parameters, those goofy things that clutter up a data sheet.
If you're not into learning cabinet design, you might want to check the Bill Fitzmaurice Simplexx 112 plans, and ask Bill if this speaker would work in that cabinet.
Simplexx
BillFitzmaurice.info - Index page

There's also a great thread by Duke that uses a prefab cabinet from Parts Express. I can't seem to locate it right now, but it would be worthwhile asking if your Peavey speaker would be compatible.
 
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#7
Yeah, like @fdeck said. Shortest answer is Yes. it's just a speaker in just a box. Longer answers are all about the differences in open back guitar cabinets and structural flak and sealed or ported bass cabinets and all thins other errata that will roll your eyes permanently.
Since you have a bass amp you're on the right track. I don't think you have anything to worry about. Since it's your bedroom, not the living room, you'll be just fine.
 
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#8
Here's what I get for a sealed box. This will not have a super lot of low end, but will have what I would call a "classic" sound, probably not unlike the speakers in use when those amps were in their heyday. Definitely seal it up in back. Adding a port wouldn't hurt, but could be done at a later date, and would increase both the low end response and the overall power handling.

On the other hand, there is something to be said for a new commercial amp that comes with a warranty and that you can try before buy. I can't help you with that dilemma. ;)

This is a link to the speaker analysis program that I wrote. It has many disclaimers, including the fact that no qualified engineer has ever reviewed it.

http://personalpages.tds.net/~fdeck/bass/speakerjs/speaker.html?Dname=Peavey DM 112 Plus&Fs=44.7&Re=3.3&Qes=0.69&Qms=11.51&Vas=109&Sd=522&Xmax=6.2&Le=0.35&Znom=4&Pe=225&Bname=40 liter ported box&V_liters=55&Ndrivers=1&Fport=0&Aport=4&Bport=4&nPorts=1&endCorrect=0.732&PinExc=100&

upload_2020-7-24_21-50-30.png
 
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#9
The amp might not be the flashest but far more important is the cabinet. If you can make a good job of dealing the guitar cab it might sound quite ok. Otherwise it will wheeze and whistle.

A well proven project like the coffeehouse 10 is another option.
 
#11
Thank you fdeck.
I could easily cut a hole, add a port if diameter/length were to be suggested:). Heck, I'd even line it with pillow feathers if anyone thinks that would help!

Edit: I just want to add that I did download WinISD Pro Alpha and entered the speaker parameters before I stopped in. I was able to produce a line chart, but the numbers on the left side of chart (-5 to 35 maybe) were meaningless to me, and all I could do for the box was enter area. I have no idea how to use the software to calculate a size/length of a port.
 
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#13
The driver you use and the cabinet need to be designed to work together to work well for bass guitar - much more so than for regular guitar. Popping a random driver into a random cabinet will give you unpredictable results. There's a free program called WinISD that, if you know some audio basics, you can use to design a cabinet/speaker combo. If you can't understand the curves it gives you, then building your own cabinets is a crapshoot, and very likely a waste of time and money.
 
#15
Heh, see edit I added to post #11. The driver wasn't exactly random. Initally I was looking at an Eminence DELTA-12LFC, but a bit of looking around here clued me in that a lot of cabs also have a tweeter/crossover. Since I was thinking in the alternative, I selected a driver with a wide range frequency 45Hz to 5kHz and a large enough Qts, .66, that it would not REQUIRE a vented cab. But you are right, it could be a waste of $80.
 

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