DIY cab

spauldingrules

Senior member
Messages
720
Any good sites on this?  The woodworking seems simple enough, but is there anything complicated about hooking up the speakers, etc.?  I'd like to build something to hook up my 5w Epiphone valve junior head to.  Any good pages on the wiring/electric hookups for the jack?

Thanks!

TS
 

jimh

Senior member
Messages
1,344
Speakers are just about as simple as you can get in terms of wiring (in the electrical sense anyway)

You just need to be careful about how you wire them together if you are going for a multiple speaker setup.  Series or parallel.  It's all about impedance matching.

Depending on the output impedance that you amp expects to see:
E.g.
2 x 4ohm speakers in series = 8ohms......Therefore plug into the 8ohm socket of you amp.
2 x 16ohm spks in paraller = 8ohm......

Try this website.  It's got the basics and some useful configurations
http://professional.celestion.com/guitar/features/drdecibel/index.asp

Jim
 

spauldingrules

Senior member
Messages
720
So is the jack that the power cable from the amp connects to just a regular guita-type jack?  Or is it something different?  What other parts would I need to hook up to the speakers?
 

jimh

Senior member
Messages
1,344
Guitar Jack - Yes
Guitar cable - NNNNNNNNOOOOOOOOOOOOO

The cable feeding the speakers from the output transformer of you amp can be carrying some potentially VERY large currents.  It has to be thick cable.  If you used a guitar cable it'd probably melt (seriously).

You can go to your local HiFi store and pick up some decent, probably very expensive speaker cable and wire it to your jacks (or you can use cheapo mains electrical cable from the local hardware store which works just as well, I have).  Any decent music shop will sell you a 'proper' speaker cable, you can tell 'cos they are usually way less flexible than a guitar cable. n Whatever you do dont use the 'Bell Wire' type speaker cable that comes with crappy micro HiFi systems.  make sure you get something good and chunky.

Wire it so that the Positive terminal of the speakers goes to the 'Tip' of the jack socket, and the Negative terminal goes to the 'Sleeve' of the jack socket.
Really you should solder the connections of the speakers, but I have seen some people use push on 'Blade' style connectors.  You run the risk of the connector coming loose and falling off if you are not careful, which could result in presenting a mismatched (or no) load to the output tranny of the amp, which could be fatal (for the amp, not you).  You'd end up screwing your valves (cheap enough to replace) or worse the transformer itself which could be expensive.

Be careful and it's easy, and you'll have fun.  If you are still not sure, come back and ask questions.


 

-CB-

Senior member
Messages
5,427
Plain old switchcraft mono jack.

One thing many cabinets suffer from is lack of depth.  By making a cabinet deeper, you enhance its low end.  You might want to try duplicating a favorite cabinet in its size...

The Fender Dual Showman and Bandmaster cabinets had an angled section, that kept the two "halves" a bit separated.  It was set at a bit of an angle - maybe only 5 degrees or so.

One other thing - is try not to get into the Thiele and Small way of porting for increased low end.  Unless you have drivers (speakers) to handle it, the result is excessive cone excursion (in/out movement) to handle the increased low end - read that - trade half an octave for limited life.  Celestion warns against it.

And finally... speaker choice is critical. 
 
N

neilium

Guest
-CB- said:
One thing many cabinets suffer from is lack of depth.  By making a cabinet deeper, you enhance its low end.  You might want to try duplicating a favorite cabinet in its size...

The first measurement, though, is the size of your car's trunk. The last cab I built had to be cut down 1/2" (depth) because it wouldn't fit in the back of my car.  That being said, deeper cab + bigger front baffle makes for a richer tone IME.

...and, no, a new car wasn't an option.
 

spauldingrules

Senior member
Messages
720
I am aware of the necessity to use a speaker cable and not an instrument cable, but thanks for your concern!  I'm sure many people have ruined something by not knowing.  So if I want to to a one speaker cab, all I need is:

1) The cabinet
2) The speaker
3) The mono jack
4) Some type of jackplate?  Homemade?  Plastic or metal or wood ok?
5) ????
 

jimh

Senior member
Messages
1,344
Cool..........Sorry........just checking..........

That's about everything.  Somewhere like RadioShack (if you're in the states or Maplin here in the UK) will probably sell you a plate with the jack socket already mounted.  All you'd have to do is cut a hole big enough in your box, mount the plate, solder the connections and you're good to go.
 
N

neilium

Guest
partsexpress.com and tubesandmore.com both sell cabinet hardware.
 

-CB-

Senior member
Messages
5,427
I'll vouch for tubesandmore (Antique Electronics) as being a great company to deal with.  They have sourced and gotten things for me... when I was in a bind... just great service.
 

dbw

Senior member
Messages
4,531
I've always been curious about this... what's the difference between an instrument cable and a speaker cable?  I've got a Monster 100 speaker cable and it looks just like a regular instrument cable.  I've even played through it, and I couldn't hear any difference.  I know not to hook up an instrument cable to my cab but I don't know why not!
 

-CB-

Senior member
Messages
5,427
GOOD instrument cable is not really so terrible for small amps, low power - you have to know the wire gauge of the cable though, keep the length short.  Consider GeorgeL's which has about an 18gauge conductor up the center and a decent copper braid.  Consider too, crap cable with a center conductor about as thick as the pubic hair off a boll weevil.... not good, forget it as any sort of speaker cable.

Typically - instrument cable is smaller gauge, more flexible, totally shielded.... it has less ampacity, and higher capacitance.  Keep in mind that 16gauge wire has an ampacity of about 10amps (or even greater), and even 22gauge wire (thin stuff) has an ampacity of just over 5 amps.  So your typical 20 to 50 watt amp is not going to turn it into a fuse... but other problems persist... especially that capacitance.  You end up losing highs, and losing lows too when you use instrument cable.

Speaker cable - regular zip cord works.  You can think in terms of about 16gauge or larger (lower number).  For short runs from head to cabinet - 16 gauge is fine for even 100 watts or more.  You get into monster 300, 500, 1200 watt amps, then you gotta look at something a bit more substantial.  Speaker cable needs no shielding.  Its not a twisted pair (usually) and has very low capacitance.  A good speaker cable will tell you its wire gauge size.  You typically can make your own from lamp cord (16 gauge), or from regular power cable available from Home Depot... something like 16/2 or 14/2 cable is fine, with 12/2 or even 8/2 being good for larger amps and longer runs.
 
N

neilium

Guest
spauldingrules said:
How about one we can all enjoy - a 2 x 10 or 2 x 12 "mini 5150" - any idea on box dimensions for it? 

Here's a good place to start:
http://www.londonpower.com/books/spkr.htm

My experience has been: An open-back cabinet can be pretty much size you want. Avoid dimensions that are multiples of one another to avoid resonances. Give yourself enough room on the front baffle that you can mount the speakers without a struggle, and make sure the speaker cutouts are at least 2" (edited from 2', sheesh) away from any edge.

Sealed cabinets need a little more planning, but you can always look up Mesa's sealed cabinet dimensions. (Personally, I don't like the sound of sealed cabs for guitar, so I really haven't spent a lot of time with them.) Additional internal volume can be faked with insulation or interior wall lining.

If you want a 2 x 12 5150, Peavey made a 2 x 12 5150 cab. Look up the dimensions and copy it.

Ported cabs? What CB said. It's a lot of slide-ruling and theile-smalling for a little more bass. I know some jazz fusion guys who swear by Mesa ported 1x12 cabs loaded with EVM 12Ls. Not my thing, though.

 

DiMitriR33

Senior member
Messages
604
-CB- said:
One other thing - is try not to get into the Thiele and Small way of porting for increased low end.  Unless you have drivers (speakers) to handle it, the result is excessive cone excursion (in/out movement) to handle the increased low end - read that - trade half an octave for limited life.  Celestion warns against it.

i parially disagree here, deeper cab = more low end when the back is open that's true, and if that is the only variable with a closed back non ported, yeah that can be true but can be false, too small will give a hump in the lower mids or upper bass but will increase the roll off frequency known as f3, too large can also increase the f3 but it won't hit the full 12db per octave untill a lower frequency.

that being said a sealed, non ported cab will get more lows than an open one and the tuning isn't really too critical. but if your worried about having the corect volume in the cab it may be easier to do an open back where the math is simple deaper = bassier.

but what a disagree on is a ported cab gets more lows from the port not the speaker. the cab and port resonate and increase load on the cone, the cone moves less when it is tuned properly, this can increase the amp load and cause the speaker to get hotter and give less life but doesn't mean more cone movement.
 

-CB-

Senior member
Messages
5,427
DiMitriR33 said:
-CB- said:
One other thing - is try not to get into the Thiele and Small way of porting for increased low end.  Unless you have drivers (speakers) to handle it, the result is excessive cone excursion (in/out movement) to handle the increased low end - read that - trade half an octave for limited life.  Celestion warns against it.

i parially disagree here, deeper cab = more low end when the back is open that's true, and if that is the only variable with a closed back non ported, yeah that can be true but can be false, too small will give a hump in the lower mids or upper bass but will increase the roll off frequency known as f3, too large can also increase the f3 but it won't hit the full 12db per octave untill a lower frequency.

that being said a sealed, non ported cab will get more lows than an open one and the tuning isn't really too critical. but if your worried about having the corect volume in the cab it may be easier to do an open back where the math is simple deaper = bassier.

but what a disagree on is a ported cab gets more lows from the port not the speaker. the cab and port resonate and increase load on the cone, the cone moves less when it is tuned properly, this can increase the amp load and cause the speaker to get hotter and give less life but doesn't mean more cone movement.

I'm just going from the Celestion website.  They say dont do it.  I "think" SICA (the new Jensen) says it too on theirs.
 

DiMitriR33

Senior member
Messages
604
no problem, i'm not advocating a ported box just clearing it up. those boxes are for speakers with a rigid cone, the paper cone guitar speakers just aren't designed for the presure. a more sutable speaker for a ported cab wont reach the required frequencies to sound good.

i don't like ported cabs anyway. they sound sloppy, not tight or precise. and too small a port will cause some funky noises at high volumes.

an open back cab is what they call a dipole enclosure, the back puts out sound out of phase from the front and it will roll off at a frequency with a wave length equal to the shortest side of the enclosure. this is why deaper = more bass. a round baffle is concidered bad, i can't give a real answer why so i wont try. a more irregular shape is suposed to give a better sound. dipoles don't have any forces or loading or resonance from the enclosure, they are concidered to have the most natural sound. all the colloration is in the speaker.

a sealed box is known as an infinite baffle. there is no phase cancellation because the sound is completely seperated from each side of the speaker. a very large box can give a natual sound as it won't load the speaker. there is a point where the displacement of the box is just right and the air acts as a spring and the box is a part of the resonant system and can slightly extend the bass. if the box is too small it raises the resonant frequency and also the roll off, so it is safer to go too large than too small. the proper size can be calculated with theile small parameters but involves alot of math. google diy speaker enclosures and find a spreadsheet if your interested in this. and the math is even worse for a ported cab

neilium said:
spauldingrules said:
How about one we can all enjoy - a 2 x 10 or 2 x 12 "mini 5150" - any idea on box dimensions for it? 

My experience has been: An open-back cabinet can be pretty much size you want. Avoid dimensions that are multiples of one another to avoid resonances. Give yourself enough room on the front baffle that you can mount the speakers without a struggle, and make sure the speaker cutouts are at least 2" (edited from 2', sheesh) away from any edge.

what neilium said, avoid regular dimension and multiples, for a 2x10 or 2x12 you can use the golden ratio, i don't remember the real name for this but it's aprox. 1.618 / 1 / 0.618 this is the prefered ratio of sides for a rectangular box but even better than this is angles, no parallel sides mean no standing waves. but this complicates construction so it depends on your wood working skills.
 

-CB-

Senior member
Messages
5,427
I dunno on the sealed enclosure and less low end.

For instance, Fender used a small coupling cap - MUCH smaller - on piggyback amps that had sealed cabinets.  The Bandmaster, the Tremolux and Showman all had coupling caps that limited the low end into the phase inverter stage.  When I put my 64 Tremolux into a combo cabiner (2x10) it sounded really bad, tinny, weak.  I plugged it into my Bandmaster cabinet (again) and it sounded great - full.  That got me thinking... must be the speakers in the combo cabinet.  So I hooked up my tweed Champ clone to those speakers and it sounded just fine.  That got me REALLY thinking.  The Tremolux is the exact same circuit - transformers, everything... as the Vibrolux, except for the coupling cap, and except that the Tremolux was piggyback, and the Vibrolux was combo.  From memory, the Tremo uses a .0005 and the Vibro uses .01.  Replaced the cap in the Tremolux... voila, sounds like it ought to.

Back in the day....  there were "deep cabinet" designs, sealed that is.. that were sold by 3rd parties for the Showman and Dual showman.  Traynor was one of the makers.  They offered a sort of "Fender looking" (minus the logo of course) cabinet that was a 2x15, loaded with JBLs or some other speaker, and the cabinet was about 3 inches deeper than the big Dual Showman cabinet.  They offered it for better low end.  I had that cabinet, but never at a time when I could compare it with the Fender.

So... I hear what you're saying, but I'm gonna stick to my guns that closed cabinets have better low end.
 

rahimiiii

Senior member
Messages
311
Guitar cables are shielded and speaker cable is not. So if you put a speaker cable from your guitar to amp it will sound buzzy due to lack of shielding, and guitar cables are not designed for the huge speaker currents that amps put out. Just get some speaker cable and wire it to a 1/4 inch jack... In Taiwan I hadn't found any pre-made speaker cables so I made my own with hi-fi cables and 1/4 inch jacks. Actually they do sell speaker cables but its all monster brand which is super expensive.
 
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