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nighthawk
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Joined: 09 Jan 2003
Posts: 289
Location: Altoona
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 Posted: Thursday Aug 21, 2003 |
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| i am looking to get two new sub cabs that require 1500 watts 3000 watts peak at 4 ohms. does anyone know where i might find an amp that will handle them both or do you think i might have to run two amps. |
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Ron
Site Admin
Joined: 07 Dec 2002
Posts: 2031
Location: State College, PA
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| Posted: Thursday Aug 21, 2003 |
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Nighthawk,
If you want to run the cabs in parallel on a single bridged amp, you'll have to find either a bridgable stereo amp that is stable driving a 2 ohm load (when bridged), or a mono, single channel amp that is stable driving a 2 ohm load.
If you want to run the low-end in stereo, (not the norm, but some people do), you'll basically need twice the amplifier oomph to get the same volume level, but just about any amp would handle the 4 ohms per channel load.
When a stereo amplifier is bridged mono, each channel sees half of the total speaker impedance, so a stereo amp that is stable at 2 ohms per channel will only be stable into a 4 ohm load when bridged.
More power is always better. It is easier to fry a speaker driver from too little power than too much. Distortion is what usually kills drivers, not sheer power.
Hope this helps.
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ragztem
Active Member
Joined: 03 Feb 2003
Posts: 72
Location: Central PA
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| Posted: Friday Aug 22, 2003 |
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| just to give you the actual formulas, Ron was correct in everything he said, BUT, to figure out any ohm load of parallel or series wiring, there are formulas, and you dont just cut the load in half. if you are wiring in parallel (pos - pos and neg- neg) then 1/Rt = 1/R1 + 1/R2 +1/R3 + etc, you are wiring in series (pos - neg - pos - neg) then you just add all the loads, Rt = R1 + R2 + R3 + etc, where Rt = total ohm load that your amp will "see" from your speakers, and R1, R2, R3, etc are your speaker loads in ohms. SO in your case, if you are in parellel, 1/Rt = 1/4 + 1/4, which is 1/Rt = 1/2 cross multiply and divide, Rt = 2ohms. Just a little tip for reference! |
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nighthawk
Gold Member
Joined: 09 Jan 2003
Posts: 289
Location: Altoona
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| Posted: Friday Aug 22, 2003 |
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| so who makes an amp capable of driving both cabs. i might have to choose different cabs because of trouble finding a big enough amp that will work well. the reason i wanted these cabs is because they are designed to work best outdoors and in concrete rooms. i am compleatly illiterate when it comes to these things. i have tried and tried and tried to find an in english explanation of the difference between series and parallel wiring without success. all i know is that i am over my head. |
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ragztem
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Joined: 03 Feb 2003
Posts: 72
Location: Central PA
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onetooloud
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Joined: 11 Aug 2003
Posts: 263
Location: Johnstown
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| Posted: Tuesday Aug 26, 2003 |
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What type of cab are they, who makes them? What is the impedance of each box itself as well as power handling of each box? Maybe you have already said this but not clear if ratings are for one box or two! Different builders spec. there cabs differently, but could obtain similier ratings.
One cab could be rated 1500 watts at 1500hz and another 1500 watts at 160hz. Specs reading this way are misleading because they look the same but are not. The cab rated at 1500hz will never handle the power of the unit rated at 160hz.
Builders who make lower grade boxes will generally give little info as to what frequency the power cap. was measured at. Just check specs for a Good JBl, EV or EAW box then at specs for a generally considered lesser grade you'll soon see what I mean.
There are several amps capable of this level of performance. Crown makes several as well as QSC and I think perhaps even Carvin or Peavy. Once again you,ll find specs for the amps as well are obtained different ways.
Last how much are you willing to spend and what level of performance do you expect. Price almost always reflects performance. Your best bet is to go with a manufactures recommendation. |
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nighthawk
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Joined: 09 Jan 2003
Posts: 289
Location: Altoona
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| Posted: Tuesday Aug 26, 2003 |
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| i have two choices. 30-300hz or 30-200hz. the one that is 30-300kz requires 1000 watts 2000 watts peak at 8 ohms. the one that is 30-200hz requires 1500 watts 3000 watts peak at 4 ohms. |
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Craven Sound
Platinum Member
Joined: 06 Aug 2003
Posts: 695
Location: Cambria County, PA
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| Posted: Wednesday Aug 27, 2003 |
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| You're going to need one huge amp or 2 medium sized (one bridged into each cab). Then you're going to have to find enough AC power to run all of your amps. I would probably figure a circuit each for your sub amps, and depending on what you have for the upper range 1 or 2 more circuits. The Crown 5002VZ has a rating of 1775/ch @ 4ohms; it draws like 35 amps so it's a power hog. I'm pretty sure this thing will cost a pretty penny but is a perfect match for your speakers. |
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onetooloud
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Joined: 11 Aug 2003
Posts: 263
Location: Johnstown
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| Posted: Wednesday Aug 27, 2003 |
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I have to agree with craven that for no holds barred performance the macrotech 5000 is the granddaddy of all amps. If money is no problem go for it. Keep in mind what was said about power, also the 5000 weights about 70lbs.
If you are on a budget like most people, you might think of a Crown CE 4000. May not have quite the output of the 5000 but its a lot cheaper and lighter 35lbs. It will still put out 1200 watts per side into 4ohms at 1000hz.
It also likes less power. I think you would do well to go with the 1000 watt RMS box with a CE4000 you will probably never notice a 500 watt differance in the boxes. I'm being consevative on power, not knowing to boxes.
Others to think about
Peavey CS 3000H 1100 watts at 4ohms per side
Peavey GPS 3500 1200 watts at 4 ohms per side
Carvin DCM 4000 can be run 2000 watts at 4ohm per side 4 channel amp, bridge two channels using the 1500 watt box. Probably lowest priced amp on the list. Remember cheaper isn't always better.
I personally run crown macros & micros. It'll all come down to how loud do you want to spend. Just some options. |
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Zerohdefects
Active Member
Joined: 08 Sep 2003
Posts: 25
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| Posted: Wednesday Nov 12, 2003 |
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| If your poweramp is drawing huge current, your tube amped guitarists will hate you if they are on the same breaker as you. |
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lonewolf
Diamond Member
Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Wednesday Nov 12, 2003 |
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I suggest that you read thru the recent post WATTS WHAAAAT?
A lot of this is covered in there.
Any time you see a peak power rating that is only 2 X the power rating, it usually means program power. Those cabs are probably 750 watts RMS. I tend to stay away from companies that rate their cabs like that.
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lonewolf
Diamond Member
Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Thursday Nov 13, 2003 |
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Peavey makes an excellent lightweight amp that will do the trick.
I don't generally recommend Peavey products, but the DPC series amps work very well and are worth a look.
The DPC1400X will put out 1400Wrms bridged into 4 ohms, but only weigh 12lbs and fit in one rack space. I think they cost a dollar a watt new, though. They are 90% efficient, so you could probably get away with putting two of these on a 20 amp circuit in most situations.
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Craven Sound
Platinum Member
Joined: 06 Aug 2003
Posts: 695
Location: Cambria County, PA
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| Posted: Thursday Nov 13, 2003 |
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| How well do power converting amps work on low end? I know that amps with switched power supplies (Carver 1.5, etc) don't do low end really well. I have some grasp on how the DPCs work: basically taking the 120V AC signal, and converting its sine wave into sound wave. (something like that.) Is this close as to how they work? |
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lonewolf
Diamond Member
Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Friday Nov 14, 2003 |
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In a linear power supply (standard amplifiers), the AC voltage is bridge rectified and then voltage regulated to maintain a constant voltage. It is always "on" and drawing current and dissipating heat.
AC voltage changes 60 times a second in a sine wave pattern. During this cycle, there are two segments where there is higher voltage and two segments where it is lower or zero voltage.
To make a long story short, on a switching power supply, the power is "sampled" only during the time that there is higher voltage present. There are a lot of other things going on as far as timing and filling in the gaps that make these supplies difficult to troubleshoot when broken. I call these "circular problems". Since the transformers are not continuously "on", they can be smaller than their linear counterparts.
Because of the "gaps" and the smaller transformers, these supplies cannot produce instantaneous peak power that the linear supplies can. Low end is where you get a lot of peaks from drums, etc. These amps perform just fine as long as you stay within their limitations and give them headroom. The DPC1400X is rated at 375Wrms at 8 ohms per channel, but only 500Wpeak at 8ohms per channel. Bridged at 4 ohms, it is rated at 1400Wrms, but I would expect they are only 1800-1900W peak.
Another thing about these amps is the when you go from an 8 to 4 to 2 ohm load, the rated rms power only goes from 375W to 500W to 700W. Many other amps' power doubles under these conditions.
The key for these amps is HEADROOM
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Ron
Site Admin
Joined: 07 Dec 2002
Posts: 2031
Location: State College, PA
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| Posted: Friday Nov 14, 2003 |
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They could overcome the instantaneous current demand problem with a large set of supply capacitors... but they're just too damn big.
I guess it goes to show that for right now, the ability to instantly source large amounts of current is still in the hands of the "heavyweight" amps. But... I'd learn to live with an amp that delivers 75% of the peak current if it only has 25% of the weight.
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lonewolf
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Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Friday Nov 14, 2003 |
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Amen to that Ron...
BTW, the DPC1000 is a better amp than the newer version DPC1400x. The only drawback is that it operates at a minimum 4ohm load in stereo and 8 ohm load bridged versus 2 and 4 ohms for the DPC1400x. The power ratings are the same for 4 and 8 ohms.
The DPC1000 has a superior fan cooling system that flows front to back. You don't have any problem stacking them in a rack. The DPC1400x depends more on top venting and can overheat if the vents are covered. It also has this crazy system where the fan accelerates as more power is used!!??? The fan sound is audible when the amp is at low volume and sounds almost like a compressor breathing.
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lonewolf
Diamond Member
Joined: 25 Sep 2003
Posts: 6249
Location: Anywhere, Earth
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| Posted: Monday Nov 24, 2003 |
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Corrections: According to the manual, the ratings for the DPC1400x in bridge mode are:
1000Wrms at 8ohms 1400Wpeak
1400Wrms at 4ohms 2000Wpeak
Not bad for 1 rack space at < 15 lbs.
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