bonzodog99 Posted November 4, 2009 Share Posted November 4, 2009 Hope you can help.I have been using a pair of EV SX300's (Passive 12" 300W 8ohm) for a while for live music and wanted some bass bins. I got a great deal on a pair of EV Sub 122 (Passive 12" 350W 8ohm), but I need advice on my amp.To power my SX300's I was using a crwon XS700 which puts out (according to manual) 450w at 8ohm per channel, so is perfect for my SX300's.However the shop I bought these subs from reckons, my amp will be fine to power both the tops and subs. The crown will put out 750W per side in 4 ohms.I did not think this was adequate, and would need a seperate amp, but he seems to think the crown will be fine.This is obviosuly great if its right, as cash is tight, but do not want to run the risk of damaging speakers or amp. I always though you needed the amp to be 1.5 times higher in watts each side tahn the speakers, but I know this all depends on the type of speakers and db Any thoughts would be welcome. He also said I would not need any crossover. Just a speakon straight of the amp into the sub and then a speakon into the top. Thanks in avdvance. Link to comment Share on other sites More sharing options...
johndenim Posted November 4, 2009 Share Posted November 4, 2009 Just because you connect 2 speakers that are 8 ohm does not mean that they will be 4.It depends on a few things. The general rule of thumb is that your power amp is twice the rms of the speakers.This gives you headroom, keeps your amp nice and cool, and reduces the risk of clipping.Personally I don't think you would be doing your rig any justice with the amp you have. Link to comment Share on other sites More sharing options...
paulears Posted November 4, 2009 Share Posted November 4, 2009 With these speakers, I tend to think the shop is right. I've always looked at this a little differently. The sub could be looked at as just another speaker driver in a single piece speaker - if you linked two of the EV300s together and ran them from one amp channel, then it's quite likely an amp with a bit more power would have been handy, but your sub will be handling just a small part of the full range, so with these, you may not run out of 'oomf' - as they're not gut wrenching diaphragm wobbling beasts in the first place. The thing will be the type of music you play through them. If it were me, I'd try them with your existing amp, run the volume up and see what they sound like when they are approaching the limits. If you start to detect distortion from the amp before it reaches the level you're after, then another amp would be a good move - but if you can get the level you want without hearing problems, or seeing the amp warnings flashing at you, I'd not worry. I quite like the EV sound, and although the subs are a little 'light' the combination pleases my ear - UNTIL you start to overdrive things and then with a big amp, the speakers sound sort of 'mushy', and when it's a too small amp problem, the horns really let you hear distortion, which is so nasty you'd notice it straight away. Link to comment Share on other sites More sharing options...
johndenim Posted November 4, 2009 Share Posted November 4, 2009 I quite like the sx300's, but the 12" sub may not keep up even with a larger amp? That said, it will add more low end.What kind of material do you do OP, and by what media?Minidisc, mp3, cd? Link to comment Share on other sites More sharing options...
Rob_Beech Posted November 4, 2009 Share Posted November 4, 2009 Between 1.5 and 2 times the rms at the given impedance is a general rule of thumb, but it depends on what you do with it, sometimes 1 x rms is fine. As John rightly mentions, the internal crossover within the sub may or may not be designed to keep the impedance seen on its input the same as on each of its output. So you may see the impedance of the sub at low frequencies, and the impedance of the mid top at the higher frequencies, and then another impedance (that varies) according crossover design around its fixed crossover point. SO you may therefore only ever be giving the entire system your 8ohm output level of 450watts. This could be fine if you never need to push the system, but you may find the amp running out of steam for louder passages and/or in larger venues. You have the amp, the subs should match well, so give it a go. If it appears that it isn't quite enough you'll have to look at other options. Your main options are, replace that amp with a larger one, Buy a second (larger) amp and a processor and run the system from 2 amps, or try a different sub with a different crossover design. The second would be the most flexible answer, but potentially the most expensive aswell, as is usually the case. Link to comment Share on other sites More sharing options...
bonzodog99 Posted November 4, 2009 Author Share Posted November 4, 2009 Thanks for the great advice guys.My music is a mixture of middle of road 50-90's, played via mini disc with vocals. Like you all say, best bet is to try it with my amp at various size venues, then if it is pushing the limit, I will invest in a second amp. Link to comment Share on other sites More sharing options...
johndenim Posted November 4, 2009 Share Posted November 4, 2009 Thomanns own ta2400 has had some pretty good reviews on here, for just over £260, it's not too expensive either. It's always a good idea anyway to have a spare, especially with ( Ahem ) Christmas coming up, you don't want your amp to go down and loose several gigs.Although that said, Crown's are pretty bullet proof. Link to comment Share on other sites More sharing options...
bonzodog99 Posted November 5, 2009 Author Share Posted November 5, 2009 Thomanns own ta2400 has had some pretty good reviews on here, for just over £260, it's not too expensive either. It's always a good idea anyway to have a spare, especially with ( Ahem ) Christmas coming up, you don't want your amp to go down and loose several gigs.Although that said, Crown's are pretty bullet proof. Thanks for that. I will look into it. I do have an old LEM powered mixer, which only kicks out 300w per side, but I have some smaller carlsbro speakers that go with it. I use this as my 'spare rig', but not much use if its at home and your amp goes down at a gig 200 miles away!!! Link to comment Share on other sites More sharing options...
bonzodog99 Posted November 9, 2009 Author Share Posted November 9, 2009 Thomanns own ta2400 has had some pretty good reviews on here, for just over £260, it's not too expensive either. It's always a good idea anyway to have a spare, especially with ( Ahem ) Christmas coming up, you don't want your amp to go down and loose several gigs.Although that said, Crown's are pretty bullet proof. I did a gig on Saturday just using my cronw to power both sx300's and sub122's but as the room was quite small did not get chance to turn th egain up too much. I was very impressed with the bass that the subs kicked out though. I am still planning on getting another amp to power the subs though, and like you say its best to have a spare. How do I link it all up though? 2 XLRs coming out of my mixer, but I will obvioulsy have a pair of XLR inputs for each amp? Does this mean I would have to buy a crossover as well? A concurrent post has been automatically merged from this point on. Think I have just answered my own questions as I have just noticed the crown has XLR outputs as well to daisy chain another amp. Link to comment Share on other sites More sharing options...
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