4 ohm head into a 8 ohm cab

[Jordy4strings]

Jordy4strings, I'd be worried about one fifteen cab going up against a loud drummer and/or guitarist. You could be fine but you probably want to have that cabinet off the ground so you can hear it better. On the ground, you may be tempted to increase the volume which may put undue stress on the speaker.

hi eriky, if i was to add another cab later on (300 watt 8ohm) will I essentially have 600 watts to play with? Thanks

 

[eriky4003]

Jordy, 2 cabs with your 500 watt amp will likely be perfect for everything. Be reasonable with the bass knob - push the lo-mid knob where the speakers will likely work better. Sometimes the bass knob just creates mud or rumble which hurts the speakers and doesn't give you much workable tone. Best of luck!

 

[wave rider]

hi eriky, if i was to add another cab later on (300 watt 8ohm) will I essentially have 600 watts to play with? Thanks

No.

You could get cabs “rated” at a 1000 watts, the amp will only put out what it can.

Cab rating in watts is often confusing and useless…

 

[bbh]

It’s ok as long as you’re not beating the daylights out of the head. If you run it hard @ 8 ohms, it will get hotter than it was meant for. Just keep an eye on it.

 

[bbh]

Ok. One more silly question. If the head is 500 watts at 8ohm and the cab is same watt and ohm, can I get 1000 watts by hooking up 2 cabs?

No but it will be louder due to more cone area. It will also be easier on the spkrs.

 

[Stranger Danger]

Will this be ok? If the head is 500 watts and the cab is 300 watts, how much output am I looking at? Will
I get 300 watt output max? Or is it impossible because its only 8ohm? Kr

Amp heads don’t have ohms. Think of the head like gasoline and the cab like a car. Gas doesn’t have mpg. The car does. If your amp says 500 watts at 4 ohms and the cab says 300 watts 8 ohms then that is a perfect match. If your cab says 300 watts at 4 ohms then it still should be fine but you need to be a lot more careful about volume and how hard you’re pushing the cab.

 

[TIMD]

Don’t overthink it. As others have stated, get a 2nd 15 exactly like what have and stack them. Don’t get crazy with the bass knob and use the mids to get punch. Listen to the sound of your speakers, if they start sounding like crap your pushing them too hard. 2x15 should be enough for any reasonable volume gig.

 

[Alessandro Cruz]

Small gigs with 200W cabinet and amp are mostly enough, unless the "small gig" is NOT a small gig.

I used to play at gigs with a drummer, keyboard and guitars on my side, using a 1x15 with 200w amp and it was perfectly fine.

And to be honest, this is far away from being ONLY power. All the surrounding ambient, equipment and mates also plays a big role there...

I've played with guitars players with 2x12 tube amps, and i could perfectly do my job, as i've played with guitar players with single speaker mosfet amps who could drive me crazy with tone and high volume.

 

[Teck_Instructor]

Hey Jordy4strings, I will try to give you the water analogy often used when starting to teach someone about electrical theory. It is not perfect, but it will give you the right idea.

Think of ohms as measuring the resistance of water going through a pipe or hose. The smaller the pipe, the greater the resistance to moving lots of water through the pipe.

Think of the amp as the pump. It is designed to work with a certain size pipe or smaller. In other words, it needs a certain amount of resistance (or more) or it will spin too fast, burn itself out and break down.

Attaching two 8 Ohm cabs in parallel would be like putting two pipes on the pump at the same time. This would be easier to move the water through than one pipe alone. The amp would see a 4 Ohm resistance, and would double the wattage output. Most amps are rated to operate at a minimum of 4 Ohms; a few at a minimum of 2 Ohms. If you were to hook up four 8 Ohm cabs, so the amp would see a 2 Ohm load, the wattage from the amp would double again. For most amps rated to operate at a minimum of 4 Ohms, running a 2 Ohm resistance full blast, this would be too much wattage and cause the amp to break. If your amp is rated for a max of 500 watts at 4 Ohms, you don't want to try to run it at 1000 watts at 2 Ohms.

Your BQ500 is rated for 4 Ohms or more. (Great value per watt for a bass amp, by-the-way.) I know a little about it because I own a BH550. I have seen tech support state the amp can be run down to 2.67 Ohms. In addition, a quote from their website about the BQ500, "Amplifier protected against short circuits, thermal overload and low speaker impedance for enhanced reliability". If you run the amp at too low a resistance (aka, impedance) (Ohms), it will shut down your speaker output until it cools down/resets. The DI is still supposed to function, even when it is in overload mode. I am glad this is built into my amp as well, but I wouldn't recommend testing it on purpose.

For all you techno geeks out there. Yes, I know the math formulas for figuring Ohm loads, wattage, etc. I have used the word resistance, where it should read impedance. Cutting the resistance (impedance) in half , increases wattage output by 67% in most amps, it doesn't double. We could talk about A/C current and sign waves. Just trying to keep it simple. The OP doesn't need the rocket science PHD level of understanding to deal with matching his amp with a cab(s).

Jordy4strings, hope that helps. Enjoy your rig, whatever you decide to do.

 

[MDBass]

It’s ok as long as you’re not beating the daylights out of the head. If you run it hard @ 8 ohms, it will get hotter than it was meant for. Just keep an eye on it.

8ohm operation is actually the easiest on an amp: the lower the resistance the more heat is created, which is why a lot of amps aren’t rated to be stable under 4ohms.

 

[Teck_Instructor]

8ohm operation is actually the easiest on an amp: the lower the resistance the more heat is created, which is why a lot of amps aren’t rated to be stable under 4ohms.

Amen!

 

[bbh]

8ohm operation is actually the easiest on an amp: the lower the resistance the more heat is created, which is why a lot of amps aren’t rated to be stable under 4ohms.

Typo, should have said 4 ohms. Thanks.

 

[Rip Van Dan]

If the amp is working now at 8ohms will that decrease its output from 500 to 250 watt? Or can I still get the full 300 watt from the cab? Cheers

That 300-watt rating on your cab is how many watts it can handle safely. It can't generate watts on its own - your amp generates the watts. I have a cab that will handle 700-watts and I often run it at our rehearsal studio with an amp that is only putting out 125-watts into it. I can't get anymore power than that 125-watts out of it even though my cab will handle 5½ times that amount because the amp is generating the watts and the cab is just handling what the amp is sending to it.

However, the impedance of your cab does allow more power or restrict the amount of power coming out of your amp. If your amp is rated 500-watts at 4 ohms, then either a single 4 ohm cabinet or two 8 ohm cabs that are hooked up in parallel connections (industry standard) will allow you to get all 500-watts out of your amp because they put a 4 ohm load on your amp. A single cab at 8 ohms will restrict the amount of power you get out to somewhere around half, say 250 to ~300-watts or so. Reason for that is that the pathway going out of the amp is bigger than the pathway into the cab.

Using a single 8 ohm cab is sort of like when a 4-lane road (the amp) goes down to 2 lanes. Everything slows down because there's not enough room for all the power. A 4-lane power supply into a single 4-lane cab will give you the most you can get out of that amp. If you have an 8 ohm cab (2-lane road) and add a second 8 ohm cab (another 2-lane road) to it, then you are only putting a 4 ohm load (4 lane road) on the amp and allowing it to deliver its best power, just like you did with the 4 ohm cab on its own

Another way to look at it is as a water hose. The larger the diameter of the hose, the more water it can carry. The smaller the hose, the less water it can carry. A 1" hose carries more water than a 1/2" hose can. With impedance, the higher the ohms number, the more restricted the connection from amp to cab is. The lower the ohms number, the more open the connection is. But if you go too low - for instance place a 2 ohm load on an amp that has a 4 ohm minimum load, then you can melt things. So don't go below the minimum ohms rating.

 

[Rip Van Dan]

Hi, is 300 watts enough to play small gigs with a guitarist and drummer? Its quite a loud rock band. Thanks

Yes, in most cases you should be able to. If you can't, they need to turn down or you all need to run through an FOH system where a sound tech can balance and reinforce your sound accordingly.

 

[Rip Van Dan]

I let others talk about the wattage, but the news is you won't overwork the rig, potentially damaging it. The bad news is the rig will sound dull, which will tempt you to start turning knobs to a risky level.

You know that totally depends on how the cab was designed. At low levels - bedroom practice - the Munson curve comes into effect. The human ear hears mid frequencies at lower levels better than either bass frequencies or treble frequencies. So a boost in bass and treble EQ at those low levels can make a big difference. However, at gig levels even in a small club, that's going to be enough volume to eliminate the Munson curve problem.

It totally depends on how the cab was designed and how much power it requires to make any sound. I have a DNS-410 cab that is very sensitive (takes very little power to bring to gig level). It can handle 1400-watts rms and I have played it at what I would consider very soft volumes in some small venues. It's still every bit as clear as when I pump a lot of watts into it. Of course, it's the clearest, most articulate, and loudest cab I've ever played through.

The 8 ohm version of his cab would only be 3db quieter than the 4 ohm version of it at all levels of his power. That shouldn't automatically make it sound dull. To make a blanket statement that 8 ohm cabs (which mine is) will sound dull is perhaps a bit of an overstatement.

 

[JeezyMcNuggles]

Will this be ok? If the head is 500 watts and the cab is 300 watts, how much output am I looking at? Will
I get 300 watt output max? Or is it impossible because its only 8ohm? Kr

500w @ 4 into 300w @ 8, sounds pretty stinking perfect to me.

 

[And I]

If the amp is working now at 8ohms will that decrease its output from 500 to 250 watt? Or can I still get the full 300 watt from the cab? Cheers

Cabs don't produce watts. Amps do. Cabs are rated for the max number of watts you can safely run through them. The amp usually says on the back wattage it will produce @8 and @4 ohms. The number of speakers in your cab says a lot more about how loud your rig will be than the number of watts stamped on the back of the amp or the cab.

Will it be loud enough? We don't know how loud your drummer is. You won't know until you try it with your band. Best bet is try one 8 ohm cab, see if it's loud enough. If not, get a second 8 ohm cab. Only reason to worry about watts at this stage in your game is to make sure you don't run a 1000w amp into a 250w cab...

 

[dkelley]

Just always remember that point about speaker cabs:

- the wattage listed on a speaker cab is how many watts it can handle, more or less.
- The amp's speaker output rating in Watts describes how many watts it can supply to the speaker
- The speaker will probably be approximately either 8 ohms or 4 ohms, with rare exceptions. Most amps also show the speaker output, in Watts, into a speaker cab that is either 4 ohms or 8 ohms, and typically the 4 ohm output will result in higher Wattage.

So..... find out what your amp's output is, in watts, when driving a speaker cab that is 4 ohms, and find out the same information for your amp when driving a speaker cab that is 8 ohms.

Make sure that wahtever that Wattage is, from the amp, into the impedance (in Ohms) that your particular cab runs at, is not higher than your cab's power handling rating (which is also in Watts). Lower watts from amp than speaker can handle is fine. Higher watts from amp than speaker can handle could be a problem if you crank it a lot.

Hard to describe, but that is what folks do when they try to match a cab and an amp, at least the basic fundamentals of it to start with.

 

[Tim Skaggs]

I let others talk about the wattage, but the news is you won't overwork the rig, potentially damaging it. The bad news is the rig will sound dull, which will tempt you to start turning knobs to a risky level.

What info has been provided indicating the rig will sound dull? For all we know so far it could be overly bright, depending on the cabinet, amp, & instrument, none of which has been revealed yet. I’ll read on....

 

[JohnnyBottom]

imho If you are in need of volume the sensitivity of that Warwick speaker is pretty low. 97db.
If I got this right means, I would take 2x the power to get to 100db.
Finding a more sensitive cab closer to 100db would get you much more volume with your limited wattage.
... I think.