| Author | Message | ||
| lovemetal629
New Username: lovemetal629 Post Number: 1 Registered: 4-2012 |
Hi guys and girls. I am new to this site, and new to some things in the guitar world (i.e. speaker cabs, wiring, all that stuff). I have 2 questions. I'm going to build a 4x10 cab in the future, and I want the end result to be a 4 ohm cab. I would use four 16 ohm speakers wired in parallel correct? and the 2nd question. I've seen 2 inputs on the back of most 4xn (n = whatever size of speakers), what is the second input for? Is it to have 2 amps going to the same cab, or is it to daisy chain it to another cab? Thanks for any help in advanced! =D | ||
| elwoodblue
Senior Member Username: elwoodblue Post Number: 1368 Registered: 6-2002 |
welcome, your math is right on the cab wiring, here's a neat calculator I use alot: http://colomar.com/Shavano/impedance_proc.php Usually the second jack is for daisy chaining cabs ( parallel inputs)...the newer marshall cabs have a mono/stereo option...that's something else completely (they even have a little circuit board behind the jacks). What amp are you using ? | ||
| byoung
Senior Member Username: byoung Post Number: 1352 Registered: 12-2004 |
I don't know how set you are on 4x10, but consider the fEarful: http://greenboy.us/fEARful/ They are truly amazing. | ||
| lovemetal629
New Username: lovemetal629 Post Number: 2 Registered: 4-2012 |
Thank you elwoodblue, really saved me a lot of time. At the moment, I'd be using a Crate GX-15 practice amp, which does have an output to go to a PA system or a cab. (And I'm able to get a killer sound out of it). And then the speaker in that is a 4 ohm. That's of course temporary though, as I'm still trying to also save up for an amp head, not sure which one I want though. @byoung - I'll look into those a little more. But right now, the cab I'll be building soon will be for 6-7 string electric guitar. Thanks anyways young. Thank you again elwood, really helped me out! =D | ||
| elwoodblue
Senior Member Username: elwoodblue Post Number: 1370 Registered: 6-2002 |
Good to hear, Let us know how it sounds, I'm sure your new cab will sound better and bigger than the speaker in the amp...and you'll have a cab already when you go for a more powerful amp (which might be soon , you might find that you'll want more overhead (extra power in reserve) with a 7 string) . Don't forget to use ONLY "Speaker" cable when connecting cabs ( not "Instrument" cable )...in case you weren't aware. I have a little 5 watt solid state practice amp that drives a `12 monitor really well, hopefully your crate will be friendly and stay relatively cool with the new set-up. With Solid state amps it's fairly safe to use total speaker impedance that is higher than the rated output (4 ohms on your Crate) , but you don't want to go lower. I've had one go up in smoke before I knew better. And just FYI,Tube amps are opposite ; a lower impedance from what the output is rated at is friendlier on the components than using a higher total impedance. | ||
| sonicus
Senior Member Username: sonicus Post Number: 2426 Registered: 5-2009 |
As far as tube amps it all depends on the OUTPUT transformer rating. 2 or 4 OHMS could kill it if it is not within it's rating such as 8 or 16. McIntosh 2300 amps that are solid state used an autoformer design that could go down to .5 ohms YES 1/2 of an OHM ! There are too many variables to take a general approach , therefore know your amps specs to avoid damage . | ||
| dfung60
Senior Member Username: dfung60 Post Number: 549 Registered: 5-2002 |
A couple of clarifications on this discussion... If you wire four 16-ohm speakers in parallel, you'll have a 4 ohm total impedance. This is the same as half of an SVT cabinet and is a good way to go. The second jack on most speaker cabs is usually wired in parallel so you can add another extension cabinet. But this will lower the overall impedance seen by the amplifier to z1+z2/2, where z1=1st cabinet's impedance, z2=second cab's impedance. If the cabinets have different impedance, they will also draw different amounts of power when wired this way, so they may have different loudness as well. The Marshalls with a splitting switch let you split the cabinet into two 2x12 channels in the same box. If you run a stereo effects rig, then you only have to carry one cabinet which is nice, although there's not much separation for things like stereo flanging. Solid state amps can drive variable impedances and produce different amounts of power depending on the impedance it sees. The math is fairly simple Output Power(in watts) = Volts (AC) * Current For solid state amps, the voltage largely stays the same independently of impedance. The current varies in inverse proportion to the impedance. So if you double the speaker impedance from 4 ohms to 8 ohms, the current will be halved and you'll get half the number of watts out. Similarly, if you halve the impedance from 8 ohms to 4 ohms you'll double the current and get twice the power out. If you connected two of those 4 ohm cabinets to this same amp in parallel using those cabinet jacks, you'll halve it again to 2 ohms and double the power output again. Yes, the same amp that produces 100 watts at 8 ohms will produce 400 watts at 2 ohms. But for this to really work, the amplifier has to be designed for this much power. When the power transistors are cranking it at 2 ohms, a lot of current is flowing and they will get very hot, so there needs to be sufficient heatsinks and airflow otherwise the transistors will literally burn up. This is often the difference between true pro gear and weekend warrior stuff and accounts for some of the big difference in price. With most solid state gear, 4 ohms is not a problem and 2 ohms will be dicey. 8 or 16 ohms is no problem, and your amp will run cooler, but it will be less loud. Now, remember, your ears have logarithmic response, so 2x the power is only a 3dB increase in sound level which is only a little bit louder. For something to sound twice as loud, it will need a +10dB increase which will require 10x the power. So don't fry your amp for a small increase! Tube amps require a matching transformer between the output tubes and the speakers. With tube amps you always want an exact match of speaker impedance to the appropriate output. A Marshall has an impedance selector switch which reconfigures the output transformer. If you set the switch wrong, you can easily cook the output transformer if you play loud. You probably never will want to connect a tube amp to a 2 ohm speaker. David Fung | ||
| lovemetal629
New Username: lovemetal629 Post Number: 3 Registered: 4-2012 |
Wow david, thanks for that info. When building my cab (whenever that me be, lol), I'll have to print off that info, and do the same thing when getting an amp head. | ||
| sonicus
Senior Member Username: sonicus Post Number: 2427 Registered: 5-2009 |
Here you go, sink your teeth in to this _____http://www.sengpielaudio.com/calculator-ohm.htm http://en.wikipedia.org/wiki/Ohm's_law http://www.prestonelectronics.com/audio/Impedance.htm | ||
| terryc
Senior Member Username: terryc Post Number: 1824 Registered: 11-2004 |
Good information that warrants a save to favourites. Whenever I built cabs I swore by the Celestion Enclosure Build Manual, I still have my copy which is over 20 years old and explains it all. Just to diverse, I built a folded enclosure with a single 10" driver with 100W rating, it took a lot of complicated wood work, cutting, sealing and I was sceptical about is sound(the graph in the manual showed really good bass response), when I used it I was astounded by the deep bass tone it produced so it's not all about how big or loud the speakers can be but the cabinet design itself is extremely important. The down side was it weighed a ton! I'll dig it out, scan and post some pdf's if anyone is interested. | ||
| fmm
Advanced Member Username: fmm Post Number: 338 Registered: 6-2002 |
The formula for resistors in parallel is actually (R1 x R2) / (R1 + R2). For more than 2 you can use the following: 1/R_Total = (1/R1) + (1/R2) + (1/R3) + ... + (1/Rn) | ||
| sonicus
Senior Member Username: sonicus Post Number: 2428 Registered: 5-2009 |
Terryc . I have a pair of older Mesa/Boogie 2x10 Road Ready cabs loaded with a pair of 16 ohm EV's each in parallel ( 8 ohm cabs) . They are quite heavy but sound great. I would be interested in your cabinet plans. I could put my table saw to work. It would be interesting to have a pair of your design for playing stereo with a Series I/II instrument. | ||
| lovemetal629
New Username: lovemetal629 Post Number: 4 Registered: 4-2012 |
So while it's on my mind, I do have a quick question regarding watts. Basically, my question is this: My temporary amp head is 15 watts and 4 ohms. If the ending wattage of the cabinet is 200 watts and 4 ohms; Will I still be able to use my 15 watt 4 ohm "head" safely? I know that if the ohms are the same, I'm good on that. It's the watts that have got me confused. | ||
| lovemetal629
New Username: lovemetal629 Post Number: 5 Registered: 4-2012 |
You guys can just forget that last question, I can figure it out (shouldn't have put it in this particular topic/thread). Anyways, I can't find any 16 ohm speakers for a good price, and that sound good to my ears. I found a speaker that I like (eminence v128), but it's an 8 ohm speaker. How would I use x4, 8ohm speakers and wire it to 4 ohms? (here's a "diagram") 8ohm speaker + 8ohm speaker + 8ohm speaker + 8ohm speaker How would I get 4 of them to be 4 ohms in the end? | ||
| davehouck
Moderator Username: davehouck Post Number: 10655 Registered: 5-2002 |
A couple of notes, though I don't have the expertise that others in this thread have. I haven't read the entire thread, so I might have missed something, but at the top you said you were building a 4x10 cab. I'm thinking that the Eminence V128 is a 12" speaker, and that it's not going to fit a 4x10 cab. To get a 4 ohm load with 4 speakers, the speakers can all be 16 ohm or all 4 ohm. In regards to the wattage ratings of your head and cab, I think the generalization is that your head should be rated the same or higher than the cab. So for instance a head rated at 700 watts into 4 ohms would be a good match for 4 ohm cabs rated at 700 or 500 watts; but you wouldn't want to try to drive a 700 watt cab with a 200 watt amp. But then I'm used to solid state power amps driving bass cabs so it might be different for all tube power amps driving guitar cabs. | ||
| lovemetal629
New Username: lovemetal629 Post Number: 6 Registered: 4-2012 |
I do realize that the v128 is a 12 inch speaker, not a 10 inch. But I couldn't find a good 16 ohm, 10 inch speaker that I liked the sound of, the price, and people said it wasn't suited too well for metal anyways. The amp "head" (that little practice amp I have), is a solid state, not a tube. Anyways, about the size of the speaker. It doesn't matter to me if it's a 4x12, as long as it sounds good. I do still need someones help for the wiring problem. How do I get four 8ohm speakers wired to be 4 ohms as the total in the end? | ||
| adriaan
Moderator Username: adriaan Post Number: 2926 Registered: 6-2002 |
You can't wire four 8 ohm speakers to make 4 ohms. Like Dave says, you need 4 ohm (in series-parallel) or 16 ohm (in parallel) units. | ||
| terryc
Senior Member Username: terryc Post Number: 1834 Registered: 11-2004 |
These images are from my Celestion handbook on cabinet construction. Hope it helps   |
