Power amp to Cabs

[Burny]

Hi guys I’m new to talkbass. So I’m a Gigging musician and My rig I usually play is a dark glass alpha omega 900 watt head And 2 orange sp212 cabs. Both together is 1200 watts at 4 ohms It sounds good. So I recently purchased a Orange little bass thing and it’s 500 watts at 4 ohms. I figure it won’t probably power my two orange cabs at 4ohms. So my question is what cab wattage should I shoot for with a 500 watt head at 4ohms. Say I’m going to power a single 4ohm cab. What’s the Maximum wattage it will drive and still sound good? Thanks in information would be great

 

[Wasnex]

Hi guys I’m new to talkbass. So I’m a Gigging musician and My rig I usually play is a dark glass alpha omega 900 watt head And 2 orange sp212 cabs. Both together is 1200 watts at 4 ohms It sounds good. So I recently purchased a Orange little bass thing and it’s 500 watts at 4 ohms. I figure it won’t probably power my two orange cabs at 4ohms. So my question is what cab wattage should I shoot for with a 500 watt head at 4ohms. Say I’m going to power a single 4ohm cab. What’s the Maximum wattage it will drive and still sound good? Thanks in information would be great

You need to consider more than the power level to figure out how loud your speakers will play. The spec you need to look for is called Sensitivity.

Sensitivity is usually expressed as how many dB the speaker will produce when fed 1 watt with the sound measured at a distance of 1 meter. I would be written something like this. 98dB 1W/1m

Sometimes you will see Sensitivity ratings giving at 2.89V. This works out to 1W at 8 ohms and 2W at 4 ohms. I believe the reason this is done is because 4 ohm speakers are often slightly less efficient than the same model in 8 ohms. To convert the 4 ohm 2.89V sensitivity rating to the 1W rating, just subtract 3dB. For example if you see something like 100dB 2.89V/1m at 4 ohms...it's the same as 97dB 1W/1m. If you see 98dB 2.89V/1m at 8ohms, it's the same thing as 98dB 1W/1m.

After you know the Sensitivity rating you just need to know that for every doubling of power you get +3dB. Then you can count how many times the power doubles, multiply by 3, and finally add to the sensitivity rating.

For example: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024. If you have 1,000W amp you double the power approximately 10 times (count the bolded numbers). Multiply by 3. You do this because you get +3dB every time you double the power. 10x3=30dB. Add this figure to your sensitivity rating. Let assume 98dB. 98+30=128dB. 128dB is how approximately how low a set of speakers rated a 98dB 1W/1m sensitivity rating will play with 1000W.

If your amp made 800 you would count 9 complete doubling. 9x3=27dB. Add the number to the sensitivity rating of 98dB 1W/1m. 98+27=125dB. Now 800 is significantly more than 512 but it's not enough for the 10th doubling, so you need to estimate a number between 1 and 3. 800 is a bit closer to 1024 than 512 so I would estimate another 2dB. 125+2=127dB.

The Alpha Omega 900 is rated for 900W at 4 ohms. If you get an amp that is rated for 500W, the SPL will drop by about 3dB. Using an online calculator the actual results are 2.55dB.

Unfortunately I don't believe Orange posted a Sensitivity rating for the SP212. Based on the Isobarik design is probably a bit lower than most 212s; most likely <95dB 1W/1m for one cab or <98dB 1W/1m for both.

Since your SP212 cabs have an impedance of 8 ohms, both of them in parallel will be 4 ohms. You Little Bass think is 500W at 4 ohms. Try running both of the SP212s.

 

[Roland GR 88]

Keep your cabs. Your 500w head will put out approx half it’s power to one cab and drive both cabs well at full power. Any single 4ohm cab rated at 500w or more will be fine with the head if you want a smaller rig. I have a 40w head and a 500w head that both sound great with a 750w cab with no issues at all.

And welcome to T.B.

 

[agedhorse]

It will be fine driving one or two of your current cabinets. By the time you find a different cabinet, if the sensitivity is lower you may end up with no net gain in volume compared with a single 8 ohm cabinet.

 

[JimChjones]

What’s the Maximum wattage it will drive and still sound good? Thanks in information would be great

A cab power rating is only the maximum safe power. There's no issue about putting a hundred watt amp into a thousand watt cabinet.

 

[basscooker]

I'm seeing a few things in the OP that twist my brain up a bit. The cabs dont make the amp louder; where is that 1200 watt number coming from? Are your cabs 4 ohms each or 4 ohms total?

Also keep in mind settings are the real determining factor of what a cab can handle. If you do much boosting down low, their power handling is more likely half or even lower than half of the published rating. Mechanical limits of bass cabs are usually not anywhere near as sexy of a number as thermal ratings. Thermal ratings are often calculated at frequencies like 1k, or a narrow band of frequencies that represent only the mid and upper mid part of the spectrum. Real world, useable bass tones turn cabs into fart-sound generators at way less power than they are typically rated to be able to handle.

 

[Burny]

Keep your cabs. Your 500w head will put out approx half it’s power to one cab and drive both cabs well at full power. Any single 4ohm cab rated at 500w or more will be fine with the head if you want a smaller rig. I have a 40w head and a 500w head that both sound great with a 750w cab with no issues at all.

And welcome to T.B.

Sweet thanks for the info!

 

[Burny]

Keep your cabs. Your 500w head will put out approx half it’s power to one cab and drive both cabs well at full power. Any single 4ohm cab rated at 500w or more will be fine with the head if you want a smaller rig. I have a 40w head and a 500w head that both sound great with a 750w cab with no issues at all.

And welcome to T.B.

I'm seeing a few things in the OP that twist my brain up a bit. The cabs dont make the amp louder; where is that 1200 watt number coming from? Are your cabs 4 ohms each or 4 ohms total?

Also keep in mind settings are the real determining factor of what a cab can handle. If you do much boosting down low, their power handling is more likely half or even lower than half of the published rating. Mechanical limits of bass cabs are usually not anywhere near as sexy of a number as thermal ratings. Thermal ratings are often calculated at frequencies like 1k, or a narrow band of frequencies that represent only the mid and upper mid part of the spectrum. Real world, useable bass tones turn cabs into fart-sound generators at way less power than they are typically rated to be able to handle.

The Cabs are 600watt at 8 Ohms. I use two of them so that’s where the 1200 watt was coming from so 1200watts at 4 ohms with both of them.

 

[Burny]

I’ll try my other sp212 this Sunday but so far I have a sound I really like. I also have a ton of Sustain with my pedal in front of it.