Kevin Ross Posted February 19, 2009 Share Posted February 19, 2009 Yes and no if that makes sense! If you buy a pair of subs with a crossover built in then you can use just one amp. However this type of setup does waste a fair amount of power and is not generally accepted as being the best thing for larger systems (awaits correction) Option 2 is to get a pair of subs and a crossover and run the system mono i.e. the left side of the amp would run the tops and the right side would run the subs The finial and best (but also most costly!) option is to get another amp and a crossover and run the system stereo 2 way. The problem with options 1 is if the subs present the amp with say an 8ohm load then the amp is only going to push 250w into that resistance (I wish people would stop using the word ohmage!) You will get a similar problem with option 2, each set of speakers would only get 500w (250w per cab) but again depending on the show you are doing it might well be adequate. If it was my money I would look at option 2 and then you can move to option 3 by just buying another amp A concurrent post has been automatically merged from this point on. You will need an amp unless you get some active bins like the Mackie SWA1501. Remember you will also need a crossover so you send the correct frequencies to the speakers. From memory don’t the Mackies have a high pass output which could then run the tops? I’m sure the last pair I bumped into had this. In that case the OP would not need a crossover. Link to comment Share on other sites More sharing options...
lostinvegas Posted February 19, 2009 Share Posted February 19, 2009 From memory don't the Mackies have a high pass output which could then run the tops? I'm sure the last pair I bumped into had this. Your right they do it was probably a bad example but the first powered subs that came to mind. Looking at the spec of the gear running in mono (option 2 in the above post) looks like a good plan as you will get the most out of the amp. Running the tops in parrallel will present 1 side of the amp with a 4ohm load this will give you 500watts into the pair of speakers (the same as your getting running them seperatly at 8ohms). The key to this matching the resitance of your sub/subs to the other channel of your amp. You need either 1 x 4ohm speaker or 2 x 8ohm speakers running in parrallel. (You do not need 2 speakers for subs as bass is omi directional). The above will give you the maximum from your current amp. You would need a sub with a built in HPF as you really only want the frequencies above 150hz down going to it. Lots of subs have this built in but they are not expensive to buy either. Chris Link to comment Share on other sites More sharing options...
psy Posted February 19, 2009 Author Share Posted February 19, 2009 cheers guys. when I was in my local music shop looking at bins a while back the guy said they had a filter in them to split the frequencies between the tops and the bins. is that what you mean by a crossover? and is peavey stuff any good? A concurrent post has been automatically merged from this point on. From memory don't the Mackies have a high pass output which could then run the tops? I'm sure the last pair I bumped into had this. Your right they do it was probably a bad example but the first powered subs that came to mind. Looking at the spec of the gear running in mono (option 2 in the above post) looks like a good plan as you will get the most out of the amp. Running the tops in parrallel will present 1 side of the amp with a 4ohm load this will give you 500watts into the pair of speakers (the same as your getting running them seperatly at 8ohms). The key to this matching the resitance of your sub/subs to the other channel of your amp. You need either 1 x 4ohm speaker or 2 x 8ohm speakers running in parrallel. (You do not need 2 speakers for subs as bass is omi directional). The above will give you the maximum from your current amp. You would need a sub with a built in HPF as you really only want the frequencies above 150hz down going to it. Lots of subs have this built in but they are not expensive to buy either. Chris I think im almost getting you here actually. just wondering by running the tops in parrallel do you mean both speakers connected into one channel using the link on the back of the first speaker to connect the second? if so how would 2 8ohm speakers present a 4ohm load? and then if I follow you correctly I would find myself a 4ohm bin with high pass frequency and put it into the other channel which should then supply it with 500wrms is that correct? do I not need something to make it so the top only produce the highs and mids or do I just use them as is and have the bin produce a better low to go with it? if im right that thats what you mean I like this suggestion as it would be something I could afford to do pretty much immediately until I get cash built up for a better system. ps. thanks again all and I hope my noob questions arent too annoying Link to comment Share on other sites More sharing options...
KevinE Posted February 19, 2009 Share Posted February 19, 2009 As an aside, we once fitted out a budget disco pub with plastic Carlsbro Gamma 10's (which will look like those Prosound cabs if you ignore the badge) and we were very pleased with them. We ran them lazily with 1200W bass bins on seperate amps and a digital crossover. I EQ'ed them warm with heavy limiting and they sounded sweet. They're very well built cabinet-wise, quite heavy, the gammas had cast-basket woofers and strong grilles, speakon, top hat with included adapter and well packed. Talking of the amps, we tried the 400W Prosound ones (the early maplin ones with the oval vent) on background music duty and I was disappointed. They sound ok but the clip light flashes very 'soon' for a 400 watter. Both fans failed in under 12 months and blew the control fuses killing the audio, I fitted Papst vari-speed ones and then they were ok until 6 months later one of them popped all its output transistors. We took them out and gave the customer Crowns and now they're here, repaired and in our loan-stock. I see Maplin have changed the design (and supplier??) of the Prosound amps and I don't know anything about the later ones. This is the later version, no idea on how they are under the bonnet. http://www.soundsavers.com/catalog/images/ps200_l.jpg And the earlier version we had problems with: http://www.premier-solutions.biz/Carlsbro%20Products/Powerline500_small1.jpg Gamma 10:http://www.premier-solutions.biz/Carlsbro%20Products/Gamma10-250p.jpg Link to comment Share on other sites More sharing options...
ChazHS Posted February 19, 2009 Share Posted February 19, 2009 And the earlier version we had problems with: http://www.premier-solutions.biz/Carlsbro%20Products/Powerline500_small1.jpg That my friend is a rebadged Carlsbro amplfier. Link to comment Share on other sites More sharing options...
Sound In Gloucestershire Posted February 19, 2009 Share Posted February 19, 2009 yes thats a carlsbro powerline 300 amp local shop sold over 100 of those with very few returns Link to comment Share on other sites More sharing options...
psy Posted February 19, 2009 Author Share Posted February 19, 2009 yes thats a carlsbro powerline 300 amp local shop sold over 100 of those with very few returns looks more like a carlsbro powerline 500. could swear that pic says 500 on it. my old gear I sold before christmas included a carlsbro powerline 800 which I used for a couple of years with no issues although to be fair it wasnt used heavily Link to comment Share on other sites More sharing options...
KevinE Posted February 19, 2009 Share Posted February 19, 2009 Yes it's a Powerline 500, I used the Carlsbro pic because I couldnt find the Maplin badged one, I used it to illustrate the earlier and later shaped units. Link to comment Share on other sites More sharing options...
johndenim Posted February 20, 2009 Share Posted February 20, 2009 I see Peavey have been mentioned a few times and while their speakers are 'OK' but far from special, I must admit that I have had a PV2600 for about 8 years now and has never let me down. Despite running it at 2ohms.Similar with the Studiomaster amps. Link to comment Share on other sites More sharing options...
lostinvegas Posted February 20, 2009 Share Posted February 20, 2009 if so how would 2 8ohm speakers present a 4ohm load? The general rule is if you run 2 speakers in parallel you halve the resistance between them so 2 x 8ohms presents the amp with a total load of 4ohms. If you run the speakers in series you double the resistance so 2 x 8 ohm speakers present the amp with a load of 16ohms here is a diagram and some info on ohms law to help you understand what I am talking about: http://www.caraudiohelp.com/ohms_law/ohms_law.htm If the speaker cabs have 2 sockets in the back these will be parallel inputs so you can go in one and out the other to link to the other speaker in parallel. and then if I follow you correctly I would find myself a 4ohm bin with high pass frequency and put it into the other channel which should then supply it with 500wrms is that correct? Yes correct. do I not need something to make it so the top only produce the highs and mids or do I just use them as is and have the bin produce a better low to go with it? The tops are full range but you will probably find they roll off around 100hz because they are not designed as a sub. So the answer is yes. Right this is going to confuse you even more BUT: If you buy 2 x 8ohm bass bins which have built in passive crossover (which sends the low frequencies to the bins and the mids and highs up to your tops) you can run in stereo again. Run a bin and top on each channel. As long as the bin and top are in parallel (and both 8ohms resistance) you will present each channel on the amp with a 4ohm load. I expect if the bins have a passive crossover and and in and out socket this will do the job for you. The first PA I built was like this and ran from 1x C-Audio RA3001 amp. It was not spectacular but served my covers band well over a number of years doing pubs and WMC's. cheers guys. when I was in my local music shop looking at bins a while back the guy said they had a filter in them to split the frequencies between the tops and the bins. is that what you mean by a crossover? and is peavey stuff any good? Peavey stuff is ok, if you want an example of a nice sounding Peavey rig the Robin2 in Bilston is all Peavey PA and is surprisingly good. The older cheap Peavey gear can be a bit hit and miss, I have some Peavey PA and have replaced all the Peavey drivers over time with Eminence or Beyma units which I think sound better. I also have some studiospares auditorium cabs which are a pain because they weigh a ton but they have lasted better than the Peavey stuff and in general are on a par sound wise. Just be careful about buying cheap and it being a false economy. The C Audio RA3001 I bought almost 15 years ago still sits in my monitor rack and is used a couple of times a week. It was a fortune when I bought it but I have had almost 15 years use from it and its still going strong. Once again I hope this helps, let us know how you get on. Chris Link to comment Share on other sites More sharing options...
smalljoshua Posted February 20, 2009 Share Posted February 20, 2009 As long as the bin and top are in parallel (and both 8ohms resistance) you will present each channel on the amp with a 4ohm load.Not always. Have a look on here for info why. To sum it up though. If the crossover is properly designed, there will be an 8ohm overall impedance. Josh Link to comment Share on other sites More sharing options...
Kevin Ross Posted February 20, 2009 Share Posted February 20, 2009 If it is properly designed then the amp will see an 8ohm load and here is crudely why. Let’s say you have a 60hz sine wave playing, the crossover would send all of that to the sub and present an 8ohm load. Let us now swap that 60hz tone for an 800hz tone, the crossover would now send all of that to the top cab and present an 8ohm load During the crossover point it will send some to the tops and some to the subs but would still roughly be 8ohm Remember that the impedance of a cab changes with frequency hence why we really should say to nominal impedance of a cab is 8ohms Lots more science behind it and I’m sure one or two of our more technically minded members will be along shortly to go into further detail, listen to them they know what they are talking about! Link to comment Share on other sites More sharing options...
lostinvegas Posted February 20, 2009 Share Posted February 20, 2009 Yes reading back I have got myself into a muddle and your quite correct it would only be 4ohm load each side without a crossover. The best option in this case would be to run 2 amps bridged at 8ohms each. Chris Link to comment Share on other sites More sharing options...
psy Posted February 20, 2009 Author Share Posted February 20, 2009 baffled again :( Link to comment Share on other sites More sharing options...
KevinE Posted February 20, 2009 Share Posted February 20, 2009 We're treading ground already covered here! Connecting an 8ohm bin and 8ohm top in parallel will give you 4 ohms. It doesnt matter what the frequency range is. Some 8-ohm (or 4) bass bins have 2-way crossovers which have a 'high' output for 8 ohm (or 4) top cabs, but to preserve the 8 ohm (or 4) overall impedance for the amp, you must use the dedicated output of the bin to power the tops. The method of doing this varies from make to make, it's either a dedicated speakon 'high' out (usually on pair 1) or else it's the speakon pair 2 usually on both speakons on the bin. Do check with your manufacturer's instructions to avoid overrunning your amplifier. Depending on the make, you may also need a dedicated 'link lead' from bass to tops which must also be connected the right way round since the tops will almost always have their input on pair 1. Going into the bin on pair one and out on high-pass pair 2 is NOT running the speakers in parallel. This is a confusing issue to the uninitiated and has led to many amplifiers (in my experience) being falsely accused of being underpowered or easily overloaded and overheated. Link to comment Share on other sites More sharing options...
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