What is the best way to power 4 x 8 ohm sub cabinets (front-loaded reflex cabs each loaded with an RCF LF21N451--1500 watts rms, 3000 watts program). At the time of building them modeling suggested that an amp that could provide power in the range of 120v per cabinet would be appropriate. Cost is a factor. It would be an install so weight and power needs aren't as much of an issue. 2 "smaller" amps such as PL380's run either with one 8 ohm cab per channel or each amp bridged into two cabs at 4 ohms. 1 larger amp such as a K10 or MA9000i with 2 cabs on each channel at 4 ohms. Price wise a pair of PL380's are probably a little cheaper but less power if run in the 1 cab per channel configuration. Any real reason to avoid 4 ohms bridged operation with good quality amps? Sorry for lack of paragraphs. Safari on the ipad doesnt seem to be letting me put them in. Just thinking out loud here,Loren Jones
Sub Amp? 1 large amp or 2 smaller amps.
- Thread starter Loren Jones
- Start date
Silas Pradetto
Graduate Student
Re: Sub Amp? 1 large amp or 2 smaller amps.
If you want a foolproof rig, you want foolproof limiters. Only the ITHD/MAi series amps have them. The Lab Gruppen Lake amps might have something similar, and so might the Powersoft K series with DSP, but both of those latter options cost more than the former.
A single MAi9000 or 12000 is definitely cheaper than a pair of PL380s - you can PM me for info.
If you want a foolproof rig, you want foolproof limiters. Only the ITHD/MAi series amps have them. The Lab Gruppen Lake amps might have something similar, and so might the Powersoft K series with DSP, but both of those latter options cost more than the former.
A single MAi9000 or 12000 is definitely cheaper than a pair of PL380s - you can PM me for info.
Re: Sub Amp? 1 large amp or 2 smaller amps.
How about a single Lab Gruppen PLM 10k to power everything?
Evan
How about a single Lab Gruppen PLM 10k to power everything?
Evan
Re: Sub Amp? 1 large amp or 2 smaller amps.
Well, we never run very loud. 4 of these subs properly powered in our room with the program and levels we run will not be working very hard. We don't go louder than 105 dbc max at mix position (80 ft back). So while the average and peak limiters would be very nice and bulletproof I'm not sure we absolutely have to have it. What are the big differences between itech hd amps and the MAi amps? Additional DSP in the itech hd for full processing above and beyond the good limiters in the MAi?In any case if an MA12000icosts less than a pair of pl380s I guess that would make the choice fairly easy.
Well, we never run very loud. 4 of these subs properly powered in our room with the program and levels we run will not be working very hard. We don't go louder than 105 dbc max at mix position (80 ft back). So while the average and peak limiters would be very nice and bulletproof I'm not sure we absolutely have to have it. What are the big differences between itech hd amps and the MAi amps? Additional DSP in the itech hd for full processing above and beyond the good limiters in the MAi?In any case if an MA12000icosts less than a pair of pl380s I guess that would make the choice fairly easy.
Re: Sub Amp? 1 large amp or 2 smaller amps.
Yeah that would obviously get the job done. All the processing and limiting we could need. Pretty pricey. Can they run in bridge mode for two channel rather than four channel operation?
Yeah that would obviously get the job done. All the processing and limiting we could need. Pretty pricey. Can they run in bridge mode for two channel rather than four channel operation?
Re: Sub Amp? 1 large amp or 2 smaller amps.
Sounds like you have good power in there so you would never need to split the amperage draw up, the main advantage of using two amps over one in my book. Other than that if you have amp failure (probably not with the Lab) you go from having no subs on one amp to half the subs on two amps.
Sounds like you have good power in there so you would never need to split the amperage draw up, the main advantage of using two amps over one in my book. Other than that if you have amp failure (probably not with the Lab) you go from having no subs on one amp to half the subs on two amps.
Re: Sub Amp? 1 large amp or 2 smaller amps.
I don't like bridging amps, and I don't like running amps below 4 ohms. I would avoid either of those things.
I don't like bridging amps, and I don't like running amps below 4 ohms. I would avoid either of those things.
Re: Sub Amp? 1 large amp or 2 smaller amps.
In that case with 8 ohm cabinets it would seem to make sense to use a larger amp with two cabinets per channel since using two amps with one cabinet per channel would be leaving some capability on the table as far as output capability goes. Thanks.
In that case with 8 ohm cabinets it would seem to make sense to use a larger amp with two cabinets per channel since using two amps with one cabinet per channel would be leaving some capability on the table as far as output capability goes. Thanks.
Silas Pradetto
Graduate Student
Re: Sub Amp? 1 large amp or 2 smaller amps.
It sounds like 12,000 watts into four 21" subwoofers might be overkill then?
It sounds like 12,000 watts into four 21" subwoofers might be overkill then?
Re: Sub Amp? 1 large amp or 2 smaller amps.
We call that "headroom." Either thermal or electrical, running an amp balls to the walls on a continuous basis is typically asking for trouble.
I also agree with Bennett, under 4 ohm or bridged are places I don't want to be.
YMMV, etc.
Tim Mc
We call that "headroom." Either thermal or electrical, running an amp balls to the walls on a continuous basis is typically asking for trouble.
I also agree with Bennett, under 4 ohm or bridged are places I don't want to be.
YMMV, etc.
Tim Mc
Re: Sub Amp? 1 large amp or 2 smaller amps.
That would be a safe bet, but I think two of those subs in a room that can seat up to 1200 would be pushed fairly hard even at our relatively tame levels.
That would be a safe bet, but I think two of those subs in a room that can seat up to 1200 would be pushed fairly hard even at our relatively tame levels.
Re: Sub Amp? 1 large amp or 2 smaller amps.
It's amazing when a PL380 is considered the 'smaller' amp of choice. Yowza.
Having 2 smaller amps versus 1 bigger amp would give you emergency backup in the event of an amp failure, but in reality, amps that aren't beaten tend to be amazingly reliable, especially in the caliber we are talking.
It's amazing when a PL380 is considered the 'smaller' amp of choice. Yowza.
Having 2 smaller amps versus 1 bigger amp would give you emergency backup in the event of an amp failure, but in reality, amps that aren't beaten tend to be amazingly reliable, especially in the caliber we are talking.
Re: Sub Amp? 1 large amp or 2 smaller amps.
Loren,
Glad to see you built two more
At Xmax for the driver in this cabinet:
(160V_peak/1.414)^2/8 = Any amp that will do 1600W into 8ohms (or 3200 into 4) will work. While bridging amps is no big deal, one box per channel of a PL380 looks good to me, just buy two of them. Or you could buy 4x RMX2450 and bridge them. No need for all the fancy limiter gizmos in the iTech if you're not beating up on them all the time.
Forum regular, and all around good guy, Jeff Knorr has some PL380s for sale in the marketplace here right now. Buy two, turn on the clip limiters, set the processing from the spreadsheet and forget worrying about blowing them up.~:-D~:grin:
Loren,
Glad to see you built two more
At Xmax for the driver in this cabinet:
(160V_peak/1.414)^2/8 = Any amp that will do 1600W into 8ohms (or 3200 into 4) will work. While bridging amps is no big deal, one box per channel of a PL380 looks good to me, just buy two of them. Or you could buy 4x RMX2450 and bridge them. No need for all the fancy limiter gizmos in the iTech if you're not beating up on them all the time.
Forum regular, and all around good guy, Jeff Knorr has some PL380s for sale in the marketplace here right now. Buy two, turn on the clip limiters, set the processing from the spreadsheet and forget worrying about blowing them up.
~:-D~:grin:Re: Sub Amp? 1 large amp or 2 smaller amps.
Phil,
I didn't build them yet. I was trying to get a realistic idea of amplification cost to pitch the idea to the pastors. I have used two of them in our service once and it seemed like they were getting fairly close to capacity that's why I was thinking 4 would be safer. Newbie volunteer operators like me are much less likely to hurt anything if it is designed with some extra capability / headroom. I think I'm gonna try them again this weekend. I will probably power each off a bridged MA2400 (which we already have 3 of on our current subs) and see how that is.
Thanks for bringing some intimate knowledge and math reality to the table. If the pastors ended up buying off on it we could just pick up one more MA2400 and run one bridged into each sub. That would give us similar power to one box per side of a PL380 or one per a bridged RMX2450. That would save a ton on amp costs. We'll see if they will go for it.
The question was partly theoretical just to see if there is a reason to prefer one large amp with two 8 ohm cabs per channel vs 2 slightly smaller amps with one cab per channel or even one bridged amp per cab. I guess there is no theoretical advantage for one over the other. 1 big amp is less weight and rack space if you are moving things, but the options with more than one amp give flexibility and redundancy at the cost of weight, space. I was just overthinking.
Phil,
I didn't build them yet. I was trying to get a realistic idea of amplification cost to pitch the idea to the pastors. I have used two of them in our service once and it seemed like they were getting fairly close to capacity that's why I was thinking 4 would be safer. Newbie volunteer operators like me are much less likely to hurt anything if it is designed with some extra capability / headroom. I think I'm gonna try them again this weekend. I will probably power each off a bridged MA2400 (which we already have 3 of on our current subs) and see how that is.
Thanks for bringing some intimate knowledge and math reality to the table. If the pastors ended up buying off on it we could just pick up one more MA2400 and run one bridged into each sub. That would give us similar power to one box per side of a PL380 or one per a bridged RMX2450. That would save a ton on amp costs. We'll see if they will go for it.
The question was partly theoretical just to see if there is a reason to prefer one large amp with two 8 ohm cabs per channel vs 2 slightly smaller amps with one cab per channel or even one bridged amp per cab. I guess there is no theoretical advantage for one over the other. 1 big amp is less weight and rack space if you are moving things, but the options with more than one amp give flexibility and redundancy at the cost of weight, space. I was just overthinking.
Loren,
Glad to see you built two more
At Xmax for the driver in this cabinet:
(160V_peak/1.414)^2/8 = Any amp that will do 1600W into 8ohms (or 3200 into 4) will work. While bridging amps is no big deal, one box per channel of a PL380 looks good to me, just buy two of them. Or you could buy 4x RMX2450 and bridge them. No need for all the fancy limiter gizmos in the iTech if you're not beating up on them all the time.
Forum regular, and all around good guy, Jeff Knorr has some PL380s for sale in the marketplace here right now. Buy two, turn on the clip limiters, set the processing from the spreadsheet and forget worrying about blowing them up.
Re: Sub Amp? 1 large amp or 2 smaller amps.
A fourth bridged MA2400 would do the trick, indeed, and at a low price. No reason to worry about amplifier weight or number of RU if you have the room in your install racks.
You're not going to hurt these drivers with a bridged MA2400 unless someone does something colossally stupid like pure sine wave tones through them for extended time.
A fourth bridged MA2400 would do the trick, indeed, and at a low price. No reason to worry about amplifier weight or number of RU if you have the room in your install racks.
You're not going to hurt these drivers with a bridged MA2400 unless someone does something colossally stupid like pure sine wave tones through them for extended time.
Last edited:
Re: Sub Amp? 1 large amp or 2 smaller amps.
+1... Just because you can run an amp down to 2 ohms doesn't mean you should...
JR
+1... Just because you can run an amp down to 2 ohms doesn't mean you should...
JR
Re: Sub Amp? 1 large amp or 2 smaller amps.
There are a number of problems that can stop both sides of an amp from working, with only one amp, it not working means no subs.
With two amps capable of two ohm operation, one can fail and all four subs still can be used.
The redundancy aspect is quite compelling.
There are a number of problems that can stop both sides of an amp from working, with only one amp, it not working means no subs.
With two amps capable of two ohm operation, one can fail and all four subs still can be used.
Re: Sub Amp? 1 large amp or 2 smaller amps.
As long as you have newbies and volunteers who grasp the concept of headroom and don't appear to only understand getting as loud as possible. It's like it doesn't matter how much 'safety factor' you try to build into the system, those are the people people likely to push it to the edge, and sometimes over, anyways.