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-   -   Speaker Wattage rating question (http://www.talkbass.com/forum/f15/speaker-wattage-rating-question-1010155/)

 siksniper1996 08-25-2013 03:45 PM

Speaker Wattage rating question

Now I know if you have two speakers @ 8 ohms the impedance turns into 4 ohms. But lets say you have 2 speakers rated at 300 watts rms @ 8 ohms, does that mean the speakers would also be rated at 600 watts @ 4 ohms?

 Bass_Pounder 08-25-2013 03:48 PM

Yes............

Two 300w 8 ohm speakers together presents a 4 ohm load to the amp, and is thermally rated for 600w

 /\/\3phist0 08-25-2013 03:50 PM

http://speakerimpedance.co.uk

 B-string 08-25-2013 03:56 PM

Yes and yes. Just remember with two or more speakers or cabs take the lowest rated and multiply by the number of units. Like a 300 watt cab plus a 800 watt cab limits you to 2 X 300 or 600 watts. 4 units one 600 watt and three 200 watt 4 X 200= 800 watts.

 siksniper1996 08-25-2013 06:20 PM

Quote:
 Originally Posted by B-string (Post 14779736) Yes and yes. Just remember with two or more speakers or cabs take the lowest rated and multiply by the number of units. Like a 300 watt cab plus a 800 watt cab limits you to 2 X 300 or 600 watts. 4 units one 600 watt and three 200 watt 4 X 200= 800 watts.
So if I have this correct that would mean if I had a speaker rated at 500 watts @ 8 ohms and another speaker 300 watts @ 8 ohms, then I would want a amp that delivers 600 watts @ 4 ohms ?/

 B-string 08-25-2013 06:25 PM

You can run any wattage amp you want. Expect that two cabs will max out at 600 watts combined. You could run them from a 100 watt amp or a 1500 watt amp (if you are careful).

 two fingers 08-25-2013 06:29 PM

Quote:
 Originally Posted by B-string (Post 14780269) You can run any wattage amp you want. Expect that two cabs will max out at 600 watts combined. You could run them from a 100 watt amp or a 1500 watt amp (if you are careful).
B-string is wise. Heed his words.

Ratings virtually don't matter at all. They are mostly useless numbers used for marketing. Don't go below the minimum ohm rating of your amp. If you have questions about that, come back. Buy matching speaker cabs. If you don't do anything silly, you won't blow speakers no matter what the numbers say. Use your ears, not your calculator.

 siksniper1996 08-25-2013 06:44 PM

I'm sorry, I'm still confused wouldn't a 100 watt amp be underpowering it and cause clipping, and a 1500 watt amp be way too much?

 SactoBass 08-25-2013 06:54 PM

Quote:
 Originally Posted by siksniper1996 (Post 14780333) I'm sorry, I'm still confused wouldn't a 100 watt amp be underpowering it and cause clipping, and a 1500 watt amp be way too much?
If you overdrive the 100 watt amp, then yes, you could cause clipping. If the amp is solid state, then that distortion would probably sound bad to your ears. If the amp is all-tube, then you might actually like the sound of that distortion. Either way, you would not be harming your speakers.

The 1500 watt amp would work fine as long as you don't crank too much wattage into the speakers (i.e., be sensitive with the volume and bass controls).

Also, speaker manfacturers love to use the thermal rating spec (instead of the mechanical rating spec) because the thermal rating spec is so much higher. A 300 watt speaker is it's thermal rating. The mechanical limit is probably around half of that.

 SactoBass 08-25-2013 06:56 PM

Quote:
 Originally Posted by siksniper1996 (Post 14779706) Now I know if you have two speakers @ 8 ohms the impedance turns into 4 ohms. But lets say you have 2 speakers rated at 300 watts rms @ 8 ohms, does that mean the speakers would also be rated at 600 watts @ 4 ohms?
Btw, you are correct.

Regarding impedance, 8 goes to 4 (with two speakers) provided you wire them in parallel, which is the most common way of connecting speakers. Wired in series, the 8 would go to 16.

 GKon 08-25-2013 07:00 PM

Quote:
 Originally Posted by /\/\3phist0 (Post 14779722) http://speakerimpedance.co.uk
THANKS!

 B-string 08-25-2013 07:05 PM

You are under-powering your speakers when not playing them!? Clipping means you don't have enough available power and you have to exceed the amp's rating in the attempt to meet your volume needs. If you can meet your volume needs without cranking the amp and causing distortion the speakers will be VERY happy with 100 clean watts. With the 1500 watt amp you have to be listening for speaker help cries if you start pushing the amp head. A 1500 watt amp outputs the same power as the 100 watt amp with no signal, 0 watts. 100 watts from a 100 watt rated amp is the same as 100 watts from a 1500 watt rated amp. Amplifiers are not light bulbs, the output rating is the maximum clean wattage the amp is designed to deliver. It is up to you how much you use or need of that rating.
Clipping from an amplifier is an attempt to exceed it's designed rating.

 siksniper1996 08-25-2013 07:17 PM

Then how would you avoid clipping?

 B-string 08-25-2013 07:22 PM

If you get loud enough while turning the master volume up and it sounds clean with no unwanted distrotion you have avoided clipping. ;)

 siksniper1996 08-25-2013 07:29 PM

2 questions:

1. so it's possible to have a 100 watt amplifier powering like two 400 watt speakers, as long as the impedance is correct and clipping is avoided?

2. Isn't distortion controlling clipping? How does that clipping not cause speakers to blow?

 B-string 08-25-2013 07:46 PM

1) Yes it is, speakers are rated for maximum INPUT power from an amplifier.
2) Clipping CAUSES distortion, before the power amp section of an amp it is signal level only. Overdriving the power amp section of an amp head is different and makes the power amp exceed designed ratings (more power than it is rated for).

A distortion pedal between your bass and the amp does not cause clipping in the amps poweramp, distortion/clipping can only happen there by running the amp at a higher output then rated for. An overdriven 100 watt amp can output 300 watts. Take that to a 600 watt amp and distorted (clipped) output from that power section can exceed 1,200 watts easy. If you have cabs rated at 600 watts they will not be happy for long.

Run your distortion pedal without overdriving the 100 watt amp's power section and 400 watt rated cabs will be happy. The trouble then is being able to tell the difference between the two types of distortion.

 siksniper1996 08-25-2013 07:52 PM

One more quick question.

If I add more speakers in parallel, the ohms of the amp decrease and the wattage output of the amp increases, but do speakers wattage rating change if the impedance is change like is a 400 watt speaker at 8 ohms still rated for 400 watts at 4 ohms or does it now change?

 Turnaround 08-25-2013 07:56 PM

Quote:
 Originally Posted by two fingers (Post 14780281) Ratings virtually don't matter at all. Don't go below the minimum ohm rating of your amp.
Oh - so ratings do matter...

 B-string 08-25-2013 07:59 PM

Wattage from an amp only increases "generally" with SS amps or those without output transformers when the number in ohms goes down (because the load on the amp increases). Some SS amps actually de-rate (put out less power) at 2 ohms then they do at 4 ohms.

The impedance of a speaker is designed by the voice coil winding or how multiple speakers get wired together. The input power rating is completely separate from the designed impedance.

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