Members Jeff Cooperman Posted May 14, 2005 Members Share Posted May 14, 2005 Hi, I recently found a neat little 15" cabinet that I really like because it's light weight and small. It had a crappy speaker in it, so I replaced it with an 8 ohm 300 watt rms Eminence Legend CB 15, and now it sounds great. I consulted with someone at US Speaker and they found that to be a great speaker for that size cabinet (I was looking for a Neo but this spec'd out better). They also told me it was important to not underpower it or I will fry the coil. They recommended I have at least 250 watts at 8 ohms. I was powering it temporarily with my P.A. system's powered mixer, but was planning to shop for a new bass head. I checked all the catologs and e-bay and was suprised that most of what I consider to be typical mid priced amps dont have that much power. It seemed I'd have to pay well over $500 closer to $1,000 to find that much power. So I decided to buy a Samson Studio Servo Amp. It can be bridged mono for 550 watts at 8 ohms and only cost $250. I also found a cheap used Rocktron pre amp for $65. I added my sonic maximizer for extra clarity and was in business. It sounds great, but I now realize with all this rack mounted gear I'm very far from my original intent of having a light weight portable rig. I thought about returning the power amp and going with somthing like the Ampeg port a bass head but I can't get my self to spend that much. What confuses me is that I see set ups with 4-10's and 15's all powered by less powerfull amps. How can this be done with out damaging the speakers and can you really get enough clean punch and bottom with an amp that say delivers 300 watts at 4 ohms into a 300 watt 8 ohm cabinet? Or if I add another cabinet and drop my resistance to 4 ohms can I then get away with using an amp that puts out 300 watt at 4 ohms or would I then need 600 watts to drive the two cabinets? Thanks for listening I'd love to hear your thoughts, I have another 15 days to decide if I want to return the power amp. Unless I hear any better ideas I'll probably keep it because it has a lot of power for the money. Jeff Link to comment Share on other sites More sharing options...
Members rovito Posted May 14, 2005 Members Share Posted May 14, 2005 The only way to damage a speaker with less than its rated power is to push the amp into clipping. Any amp in any power range will safely push your speaker. just dont make it distort. The distortion(square waves) are what kills speakers. On the other hand most good speakers are rated for double their RMS rating in a peak. This is why you can push more power than the speaker is rated for without blowing the voice coil in a speaker. More powerful amps will have better damping factors( how far the cone of the speaker moves in and out) to help keep a speaker safe but the bottom line is if you dont abuse the speaker it wont blow. Also use the lowest gauge speaker wire you can find. It will help. Link to comment Share on other sites More sharing options...
Members Jeff Cooperman Posted May 17, 2005 Author Members Share Posted May 17, 2005 Hey rovito, thanks a lot. Your simple and clear explanation was just what I needed. Armed with that info, I felt safe to try powering the speaker with a 120 watt amp and then 180 watts. While they both produced nice clean sound with plenty of volume, it was kind of thin and whimpy. When I hooked up the 550 watt power amp it made a huge difference. It sounded like a much heavier more solid cabinet and you could really feel the thump in your chest. I'm keeping the power amp and I'll just deal with the portability issues. Thanks again. Jeff Link to comment Share on other sites More sharing options...
Moderators Kindness Posted May 17, 2005 Moderators Share Posted May 17, 2005 Good explanation, but I'll add a couple points for clarity... Originally posted by rovito The only way to damage a speaker with less than its rated power is to push the amp into clipping. Which causes the amp to put out more than it's rated power (sometimes double its rated output). Any amp in any power range will safely push your speaker. just dont make it distort. The distortion(square waves) are what kills speakers. If it causes the amp to put out more power than your speaker can handle. On the other hand, a 5 watt amp can clip all day into a cabinet rated for 500 watts and not cause any damage. (It will likely sound like crap.) On the other hand most good speakers are rated for double their RMS rating in a peak. This is why you can push more power than the speaker is rated for without blowing the voice coil in a speaker. More powerful amps will have better damping factors( how far the cone of the speaker moves in and out) to help keep a speaker safe but the bottom line is if you dont abuse the speaker it wont blow. Also use the lowest gauge speaker wire you can find. It will help. You will find many people using amp rated for twice the power (or more) than their speakers are rated for because (1) power is relatively cheap, (2) well constructed amps can often control the speaker movement better causing a more pleasing sound - see rovito's explanation of damping factor - and (3) you just might need that extra power at an unexpected time. When using a more powerful amp, simply listen to your speaker. If it sounds like it is getting too much power, it is. Link to comment Share on other sites More sharing options...
Members Jeff Cooperman Posted May 17, 2005 Author Members Share Posted May 17, 2005 Thanks kindness, that dampening factor is what has me amazed. For years I hauled around 2 heavy 15' cabinets and powered them with a GK-400b. I thought I was getting a pretty strong sound with a heavy thump. Now I find I can get a similar sound in a much lighter cabinet by using a more powerful amp. Awesome! Link to comment Share on other sites More sharing options...
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