watts? ohms? impedance? huh?

[ted]

Sorry, I couldn't find the answers on google for this one, so I'll ask you experts.

I know for a head to match a cab, the electronic specs should suit one another. The thing is that when I see something driving ____ watts into ____ ohms, I get confused.

What the hell does this all mean? Does it have to do with the number/size of cones in the cabinet?

Also, what do you reckon is a good size/power for gigs, i.e. club-size?

[thor666]

i'm bad at the matching thing too (always read never remember) so in short if your impedance (in ohms) of your amp and your cab is the same, you're safe.

also, as long as your wattage rating of your speaker is higher than your amp wattage, you're safe.

size wise it depends really one the size of the club, what amp you are using, and the cab. even a measly 18w fulltube marshall clone on 4x12 can sound loud enough for a small club.

if you don't understand what i'm saying, uh, then you're screwed. ;D or not really, you need someone expert to interact with real time, real life. some things cannot be explained online properly.

[Pathein.Raindrop.Moe]

try checking over at amp forums, will have those infos. I rememeber reading those thing alot at THD amp forum, harmony central amp forum, carvin amp forum etc

[ted]

thanks for your advice so far guys. so which one actually determines the loudness of the amp? the wattage or the size/number of cones, or the ohms?

i read something about frying the circuit if you connect the wrong ohms value, and that there is a difference between the RMS value and peak value.

oh yeah sorry i'm asking more in relation to bass amps actually, although i think this watt/ohm thing relates to all stacks.

*sigh* - this is the result of me growing up in the plug and play generation, cos' the only things available at jam studios are combos, and at gigs you think about asking these qns. i find that few people actually discuss such stuff, and most people are more concerned with their basses and effects rather than amps. maybe its cos' in SG the culture is not to bring your own amps to gigs.

[Pathein.Raindrop.Moe]

woahh, cheemm

the questions need a amp forum to answer liao

paiseh paiseh

[ohohjanggo]

never unplug your head from your cab while its still switched on... it will fry yer head

speakers - related to output of yr amp and the combined output of yr drivers. you don't want to match a high output amp to a low rated driver, unless you want the driver to distort. eg - 50W head matched with a 25W driver - you gonna get a lot of dirt.

If its headroom you want, then of course the reverse applies. 50W head matched with 100W driver will result in cleans. i presume you understand headroom. however, if you want to have the option to distort naturally - i.e. brown sound , then you may want to match it with a 75W driver. so you get best of both worlds. its generally clean, but increase your gain, or select a boost pedal, and you get some dirt.

ohms / impedence - the impedence that is like the magic impedence is 4 Ohms. you set your amp head to 4 Ohms and it works with most everything. i don't know why but its true. however, most people want to match their heads with their cabs. As such, the number of drivers come into play. depending on whether you wire your drivers in series or parallel, it is calculated differently.

First lets talk about load - i.e. what the head sees. generally if the load is lower - i.e. 4 Ohms, the output is greater. Every head is generally designed for a specific load. unless of course you have a head which offers you a choice - i.e. either 4 ohm or 8 Ohm. this is usually a switch which you select.

So if you have a 4 Ohm head, and match it with a 8 Ohms cabinet, you're safe. Only effect would be that you would have lower output. However, the other way, i.e. 8 Ohm head matched with a 4 ohm cabinet would fry your head.

So you have 2 X 8 Ohm speakers. You have the choice of 2 different wiring methods - parallel and series.

In parallel, you simply connect the + terminal of 1 speaker to the + terminal of the 2nd speaker. You would do the same for the - terminals.

The resultant impedence would be:-

total impedence (R) = 1/[(1/8) + (1/8)]

= 1/[2/8]
= 1/[1/4]
= 4 Ohms

in series, you would need a dual voice coiled driver, otherwise there would be distortion or back EMF. Wiring drivers in series is thus not recommended unless you understand what DVC drivers are. generally for series:-

Total impedence = I1 + I2

So for 2 X 8 Ohm drivers wired in series you would get 16 Ohms. unless you use some creative wiring ... then some variations are possible. It gets a little more complex, and a mistake would affect your head/drivers.

i would strongly suggest you wire the drivers in parallel.

selecting drivers - depending on what you want. maybe you can provide some details on your head and then the type of sound you are after. i don't have too much experience with bass sound tho - so maybe someone else in this forum can suggest more information to you.

i hope this helps

[Stunotonyas]

mind boggling......

[ted]

ohohjango > absolutely! thanks a lot, really clears up a lot of things. u is da shi-fu.

[Dodgy Conman]

that really went over my headroom.

arts student spit on physics *ppptui*

[tso]

so rocket science meh? i always thought you can always choose what ohm you want with a switch or output/input on the amp head and cab?

[Pathein.Raindrop.Moe]

just plug in, either play happy or watch/hear smoke over and water from your eyes!!!

[Monsieur Gainsbourg]

Jango lost me after the 1st line... but the doode sure knows his shit!

Okay, anyone got pictures of Fiona Xie?

[Pathein.Raindrop.Moe]

[ohohjanggo]

yes there's a switch at the back of the amp ... but really it reflects how the speaker has been wired. so you can happily select any ohm setting. but if the speakers are mismatched with yr ohm setting, then you will see smoke or even hear a mild explosion .... bye bye amp and bye bye speakers

[ohohjanggo]

fiona rawks!