Quick question about the power ratings

[valencia0919]

Hi, I've never had a decent head and cab before, and I'm looking for some light rig.
The one combination I'm looking at is GK 700rb-ii and GK Neo cabs.
Now.. I think Neo210 is little bit more than what I need, so I want to get Neo112. However, I noticed that Neo112's power rating is 300W. Is it gonna break the cab if I use 700rb and 112?

Specs: 700rb-ii: LF 480W at 4ohms and 320W at 8ohms (I don't know what HF means, but it says HF 50W at 8ohms)
Neo210: 8ohms, 400W
Noe112: 8ohms, 300W

More generally, if the power from the head is bigger than the cab's power ratings, is it going to screw up the cab?
P.S. I would love to see some suggestions (1x12 and head about 500W)

[will33]

No, it won't hurt it, just don't crank it way up. If the speaker starts to sound distorted, back off. A 112 isn't going to get super loud. If it isn't enough, get a second 112 instead of trying to crank more power into the one.

Speakers ratings aren't much of an indicator as to what they can handle. That 300 watts is the point at which the voice coil will melt/short out. It's a thermal limit/measurement of heat. The excursion limit, which is almost never published is how far it can move back and forth. This limit is usually around 1/2, sometimes even 1/3 of the "wattage rating". The good news is, most people aren't consistently sending the speaker as much power as they think they are, even from their big amps.

Just listen to the speaker, if it distorts, turn down or add another speaker.

[cchorney]

Yea what Will33 said. Trust your ears - if you hear farting noises, turn it down. If you need to go louder and want to avoid farting noises, cut your lower frequencies. I have a 300 watt 210 combo and it can keep up with an unmic'd drummer in a smaller space, but if I needed to go louder I would need to either get a second cab or plug into the PA.

The HF and LF numbers is because the 700rb-ii has 2 amps, one for low frequencies (like a 15) and one for high frequencies (like a horn). You would likely just be running thru the LF, unless you got a biamp cab from GK to go with it.

I would listen to both but if you liked the tone of both cabs equally, I would probably go with the 210, as more speaker generally equals more perceived sound pressure.

[will33]

HF = High Frequency

It's the little 50 watt amp to drive tweeters. It works if you have a GK cab with a tweeter wired for use with the GK amps. It uses a 4 conductor cable. Most people just set the amp to full range and plug into the LF (Low Frequency) outputs.

Main point is just listen to it. Don't make the mistake of thinking if you've got a 300 watt amp and a 400 watt speaker, you can crank everything up to 10 and run trouble-free, doesn't work that way.

[valencia0919]

Thanks guys!! I really appreciate your answers and advice.

[Joe Louvar]

Originally Posted by valencia0919

More generally, if the power from the head is bigger than the cab's power ratings, is it going to screw up the cab?

I just posted this in another thread - but it applies here too.

This is what Eminence say’s about it ~

Power handling
This specification is very important to transducer selection. Obviously, you need to choose a loudspeaker that is capable of handling the input power you are going to provide. <snip> The ideal situation is to choose a loudspeaker that has the capability of handling more power than you can provide lending some headroom and insurance against thermal failure. <snip>

Generally speaking, the number one contributor to a transducer’s power rating is its ability to release thermal energy. This is affected by several design choices, but most notably voice coil size, magnet size, venting, and the adhesives used in voice coil construction. Larger coil and magnet sizes provide more area for heat to dissipate, while venting allows thermal energy to escape and cooler air to enter the motor structure. Equally important is the ability of the voice coil to handle thermal energy. Eminence is renowned for its use of proprietary adhesives and components that maximize the voice coil’s ability to handle extreme temperatures. Mechanical factors must also be considered when determining power handling. A transducer might be able to handle 1,000W from a thermal perspective, but would fail long before that level was reached from a mechanical issue such as the coil hitting the back plate, the coil coming out of the gap, the cone buckling from too much outward movement, or the spider bottoming on the top plate. The most common cause of such a failure would be asking the speaker to produce more low frequencies than it could mechanically produce at the rated power. Be sure to consider the suggested usable frequency range and the Xlim parameter in conjunction with the power rating to avoid such failures. <snip> Understanding Loudspeaker Data | Eminence Speaker

[makohund]

...and if you understand how it all really works in the context of bass instrument amplification, you'll know that following will33's advice is the way to go, and is perfectly consistent with what Eminence is saying.

A high powered amplifier run judiciously will not automatically be blasting out sustained power beyond what a lower rated cab can handle. If you turn it up too high (or boost the bass too much) and are in danger of giving it more than it can handle, you will reach the mechanical limits long before the thermal limits, and the cab will warn you by farting and/or sounding like crap.

[Joe Louvar]

Yeah, just don’t turn up the volume too high!!!

[will33]

That eminence writeup is good info, they just should've given a laymen's description of thermal power compression. The heat builds up in the voice coil over time. So you're cranking out your set and a few songs in, your rig doesn't sound as loud and clear as it did in the begining. Part of this is your ears constricting, protecting themselves from the volume, the other part is power compression. The voice coil is wire, when wire gets hot it's resistance increases. It's "resisting" more of the power you're sending it thus playing quieter. The player hears this and turns up to compensate sending the coil even more power forcing it to dissipate even more heat starting a downward spiral that results in burned out voice coils without exceeding any mechanical limits.

You avoid it by using more speakers/more coils to dissipate the heat. Even the best speakers are very inefficient machines. Between maybe 1-4% of the power you send it ends up as sound, the rest is burned away as heat in the voice coil.

[Downunderwonder]

Eminence are dropping the ball.

Most of the time what matters for bass is how far the speaker moves, which is far more dependent on your EQ than how much power the amp may have available. A 200W amp can blow a 300W speaker quite easily. Like they said already, use your ears, a flapping speaker is failing to make more bass and will self destruct.

Taking out the really low frequencies lets the speaker put a lot of power into the 100+Hz range making you sound louder before it gets stressed.

I don't know of any 500W single 12" cabs. If there are any they will be expensive and the 500W figure is a nonsense since a 300W amp can blow them with too much low end.