View Full Version : Ohms, Impedence and Watts in Heads and Cabs
I have seen numerous of threads in which people have been asking question with regards to matching the Wattage & Ohm/s of the head/amp to the Wattage & Ohm/s the cab and if they can run the two ratings differ.
The following are some articles/threads should hopefully help.
http://www.talkbass.com/forum/showthread.php?t=144244
http://www.talkbass.com/ampfaq/
Update: 28 February 2006
http://www.duncanamps.com/technical/technical.html (Impedence calculator for your cab and other information relating to amps/heads)
Update: 04 April 2006
http://sound.westhost.com/impedanc.htm
(Impedance and Audio Equipment)
http://www.maxim-ic.com/appnotes.cfm/appnote_number/742 (Impedance: The scientific explaination)
muthafunkabass
02-26-2006, 06:34 AM
Cool articles. I wish you had posted them 3-4 months ago, not when i finally understand.:p
bottlerocket
02-26-2006, 01:52 PM
No problem, man...any resources and/or articles work great in here. Nice job. :thumb:
-Gav
Tryxx
02-28-2006, 01:14 PM
http://www.musicianforums.com/forums/showthread.php?t=329764
That should have some good links.
tinnitus
03-02-2006, 04:50 AM
hey, thats pretty helpful, thanks alot,
Would i be able to use a GK 1001 RB (which is 700 Watts at 4 ohms, 480W at 8 ohms) with one 4 x 10 hartke VX Cab (Power handling: 400W at 8 ohms) for the time being, I wanna save up for a better cab later on...
muthafunkabass
03-02-2006, 06:38 AM
Yeah, that would work.
Trevo
03-11-2006, 09:31 PM
I am still veery confused:confused:
Could I hook up a Behringer B Stock BX3000T Ultrabass 300W Bass Head (http://www.musiciansfriend.com/product/Bass/Amps?sku=480695V) to a Basson B15B 300W Bass Cabinet with 1x15 Speaker and Horn (http://www.musiciansfriend.com/product?sku=486200)
Plz help me
I am still veery confused:confused:
Could I hook up a Behringer B Stock BX3000T Ultrabass 300W Bass Head (http://www.musiciansfriend.com/product/Bass/Amps?sku=480695V) to a Basson B15B 300W Bass Cabinet with 1x15 Speaker and Horn (http://www.musiciansfriend.com/product?sku=486200)
Plz help me
Okay the cab you are looking at is running 300W at an impedence of 8 Ohms. The head is producing 300W at 4 Ohms.
The resistance (the impedence) of the cabinet is twice that of the head/amp, thus the head/amp will only be producing 150W at a rating of 8 Ohms.
What this basically means is that of the 300W availible to you by the cabinet, the head will only be supplying a potential 150W (just remeber that these are all guestimates as the exact number may differ slightly). I.e. You will be underpowering the cab by 150W or the cab has the ability to handle another 150W of power.
In short, Yes you can use those two items together, just do not turn the volume on the amp up too high as it will not be providing enough power to the cabinet and it may cause "clipping" of the speakers which is not very good for them.
Trevo
03-12-2006, 09:41 AM
so I shoul hook it up to a cab that haas 600 Watts through 8 ohms
i think i undeerstand
No...........you would just be making the problem worse then as the amp would still only be putting out 150W at 8 Ohms into a 600W Cab at 8 Ohms thus increasing the likelyhood of the speakers clipping.
In most cases it is the Amp/head that you need to invest the money in, in order to get one that has a decent wattage rating at various Ohm ratings.
E.g. A head/amp with a rating of 800W at 4 Ohms and a rating of 400W at 8 Ohms would be great.
What you must try and do is match the Ohm and Watt rating of the cabinet with a head of a similar rating.
EDIT: Read the links...............They explain it far better than what I can. That or email Edgebass if he has an address on his profile.
muthafunkabass
03-28-2006, 05:04 PM
Dude, nothing needs a bump in the resource section.
Trevo
04-13-2006, 08:06 AM
ebe9, would I be ok with a head with 180 watts at 8 ohms and a 150 watt cab at 8 ohms?
Killer Fridge
04-13-2006, 11:55 AM
Yes, as long as you didnt push it right to the maximum.
Pluperfect_Arson
10-26-2006, 04:27 AM
I just wanted to throw this link in here:
http://www.tunemybass.com/bass_amps/how_to_hook_up_heads_and_cabinets.html
It pretty much explains the same as the links in Ebe's post, but it is a bit easier to understand for those who don't quite have a grasp on the terminology.
Polyamarous
10-26-2006, 10:53 AM
So a 575watt 4ohm head to a 500watt 4 ohm cab would be mmkay if I don't really push out the volume?
So a 575watt 4ohm head to a 500watt 4 ohm cab would be mmkay if I don't really push out the volume?
Yes, that is actually ideal as he are pretty much matching.
And I do not know anyone who actually turns their gain and volume up all the way.
The thing to remember is that the rating the amp quotes is usually an RMS Wattage rating, i.e. the number of watts the amp can continuously push out with out doing any damage to itself.
Now unless you are actually running the amp at full you are not going to be using all of that power to the best of my knowledge.
Polyamarous
10-27-2006, 04:31 PM
Who wants to shoot at what progam watss or something are?
Like you see an amp thats rated 300watts RMS and 700watts programmable or something.
Who wants to shoot at what progam watss or something are?
Like you see an amp thats rated 300watts RMS and 700watts programmable or something.
Programme I think is just another name for Peak, but I am not sure.
ludwig109
11-08-2006, 07:23 PM
if a cab is 800 watts at 8 ohm and the head is 700watts at 4ohm is the cab still couted as 800watts or is it halved?
if a cab is 800 watts at 8 ohm and the head is 700watts at 4ohm is the cab still couted as 800watts or is it halved?
The cab rating is fixed and cannot be changed unless you rewire the cab.
It is the output of the Head that is the variable.
E.g. A Head that pushes 1000W at 4 Ohms will most likely only push out 500W at 8 Ohms.
The amount the Head is able to produce is dependant on the load placed on it by the cabinet.
So to answer your question the Cabinet ratings would not change.
The head however would most likely only be providing the cabinet with 350W at 8 Ohms.
Basically you would be underpowering the cabinet with that head.
You can still use the had with the cab, just do not turn up the volume too high as the cab will be trying to draw more wattage than the head can supply and you will possibly clip the drivers/speakers.
ludwig109
11-10-2006, 09:55 PM
cheers just im thinking of buying a gallien krueger rig, 1001 heaD +1 4x10 and possibly a 1x15 rbh cabs.... one is 800 and the others 400 so why did they match these together if they wont work well together, i wont need full volume/gain just wondering if theyll work decently together.. i havea 6string so id want good b string response. cheers for the info tho anyway
herrly
11-25-2006, 06:37 PM
Ok, I've read one of those links, and if I understand this correctly, I can take a head that is 320 watts at 8 ohms and hook it up with a cab that 400 watts at 8 ohms right? With no problems. Ok. But what if this head can do 480 watts at 4 ohms and I want to hook up 2 cabs that are 400 watts at 8 ohms? The totaly impedence of the 2 cabs will be what, 4 ohms? So how many watts would that be?
I hope I'm not making a fool outta myself here.
Anywhoo, the head and cabs are the GK-700 and the GK-SBX 115 and 410.
Ok, I've read one of those links, and if I understand this correctly, I can take a head that is 320 watts at 8 ohms and hook it up with a cab that 400 watts at 8 ohms right? With no problems. Ok. But what if this head can do 480 watts at 4 ohms and I want to hook up 2 cabs that are 400 watts at 8 ohms? The totaly impedence of the 2 cabs will be what, 4 ohms? So how many watts would that be?
I hope I'm not making a fool outta myself here.
Anywhoo, the head and cabs are the GK-700 and the GK-SBX 115 and 410.
Okay, the two cabs together will total 800W at 4 Ohms provided of course that they are wired in parallel.
Thus the 480W at 4 Ohms of the head will be spread evenly between the two, thus each cab will be getting 240W at 4 Ohms.
GuitaristD
07-01-2007, 08:11 AM
alright so as long as the cab as more ohms than the head i will be alright?
say i have a cab that handles 300watts at 16ohms
and a head that's 50watts at.. i don't know how many
but as long as the head has less ohms than 16 it won't blow up or anything right?
it's a guitar amp if you can't tell but i didn't want to start a new thread for this
alright so as long as the cab as more ohms than the head i will be alright?
say i have a cab that handles 300watts at 16ohms
and a head that's 50watts at.. i don't know how many
but as long as the head has less ohms than 16 it won't blow up or anything right?
it's a guitar amp if you can't tell but i didn't want to start a new thread for this
Ideally you want to match the Wattage and the Ohm rating of the Cab and the head.
You can run a cab that has a higher rating than the amp, and you can run an amp that has a higher rating than the cab. However you will not want to push either too much in that case.
I.e. (Assume all ratings are RMS and NOT Peak)
Ideal setup:
100 Watt 8 Ohm Amp paired with 100 Watt 8 Ohm Cab
Higher Rated Cab Setup:
50 Watt 8 Ohm Amp paired with 100 Watt 8 Ohm Cab
You will need to not try and drive the amp at full volume as you will be supplying insufficient power to the cab, and will in all likelyhood begin to clip the speakers. (Damaged speaker/s at the end of the day)
Higher Rated Amp Setup:
100 Watt 8 Ohm Amp paired with 50 Watt 8 Ohm Cab
You will once again not want to drive the amp at full power, as you will be supplying too much power to the cab and overdrive the speakers i.e. they will be working harder than they are designed for and will suffer mechanical failure ultimately (blown speaker).
If need be try and contact "edgebass" as he is very clued up with this topic.
edgebass5
07-02-2007, 10:03 AM
alright so as long as the cab as more ohms than the head i will be alright?
That would work, but you can also run a cabinet that matches the head's minimum impedance rating. This is the most common way to get the most out of a head.
This is the rule: A head (or power amp) can operate safely at or above its minimum impedance, but not below. A head with a minimum impedance of 4 ohms can operate at 4 ohms or above safely. As an example, if you ran that head with three 8 ohm cabinets (creating an impedance load of 2.67 ohms) you'd run the risk of damaging the head because its not rated to go below 4 ohms.
GuitaristD
07-02-2007, 01:46 PM
thanks fo ryou help
but i found out today that the head is switchable from 4 8 to 16 ohms
so we are deffinately good to go
but thanks fo ryou help guys i understand ohms a little more now
edgebass5
07-02-2007, 01:55 PM
thanks fo ryou help
but i found out today that the head is switchable from 4 8 to 16 ohms
so we are deffinately good to go
but thanks fo ryou help guys i understand ohms a little more now
Head's with switchable impedance should be matched to the cabinet they're using. So if the cabinet you're using is 8 ohms, make sure that the impedance switch on your head is set to 8 ohms (or you use the correct tap if there isn't a switch). That way you'll get the most out of your head.
GuitaristD
07-02-2007, 06:24 PM
right the cab is 16 ohms so i will keep the head on 16
herrly
07-28-2007, 01:18 AM
Would this combination work? And if so, could you explain how?
Gallien-Krueger 115 SBX cab
Gallien-Krueger 410 SBX cab
Gallien-Krueger 1001RB-II head
If I'm correct it would work fine right? The head is 700 watts and both cabs together would equal 800 watts right?
Would this combination work? And if so, could you explain how?
Gallien-Krueger 115 SBX cab
Gallien-Krueger 410 SBX cab
Gallien-Krueger 1001RB-II head
If I'm correct it would work fine right? The head is 700 watts and both cabs together would equal 800 watts right?
Can you provide links to the actual equipment so that we could have a look at the ohm ratings?
Thanks
edgebass5
08-06-2007, 06:51 PM
Would this combination work? And if so, could you explain how?
Gallien-Krueger 115 SBX cab
Gallien-Krueger 410 SBX cab
Gallien-Krueger 1001RB-II head
If I'm correct it would work fine right? The head is 700 watts and both cabs together would equal 800 watts right?
As I recall the 1001RB-II is only stable down to 4 ohms, so as long as both of those cabinets are the 8ohm version you'll be just fine.
Remember:
8+8=4
8+4=2.67
4+4=2
Stay at or above the head's minimum impedance load and you'll be fine.
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