2 ohm stable amp recomendations please

[tarior]

I'd be a little hesitant to drive the Bryston hard into 2ohms. I wouldn't give it a second thought with the Mackie.
BTW, if you get an M-1200 or M-1400, they were built in Lynnwood, WA. Just a couple of hours north of where I live. Current production all comes from China.:tears::thumbsdn:

 

[Arkay]

I just got a Soundcraftsmen PCR-800 but I am trying to power a pair of Infinity RS-II's. This amp doesnt seem to be up to the task. It starts clipping at what I would consider to be too low of a volume. I'm not rich, so I am looking for something in the 300-400 $ range. Thank for any replies.

Patrick

You need an amp with not only a lot of watts, but one with high-current capability even into 1-2 ohm loads, and preferably one with a good damping factor and higher slew rate. Not many amps come close to coping with these demands.

To stick with Soundcraftsmen, get an MA5002. Stable into 2-ohm loads; 375 watts per channel into 8 ohms and will peak at 1,000 watts when the speakers drop to the 1-2 ohm range. This amp CAN handle these speakers. Clipping indicator to keep you safe, but your ears will start bleeding around where it clips. Very good sound, very musical and strong. Unlikely to be within your budget on eBay, but you might get one locally through CL, etc... with a bit of luck (Karma!).

Adcom GA-555 (regular or MK II; the latter is better). Clear sound, but can sound a bit dry or clinical with some pre-amps. Works best with matching Adcom preamp (GP-555). Safest to run it straight, NOT in bridged mode, with these speakers, but before learning that I ran them bridged (one amp per speaker) with RS IIs and got away with it for a while. I don't recommend it, though, as the manufacturer advises against using bridged mode into such low impedance. Also has clipping indicator. You should be able to find one within your budget, although around the high end of it. Probably the easiest and cheapest way to safely drive these speakers.

Other amps that can handle these, but which would probably would exceed your budget, would include:
Ampzilla
Carver Sunfire
Krell
Bryston
McIntosh (some models)

These speakers are worth powering right, even though to do so will usually cost more than the speakers themselves. Powered right and in the right listening space, they sound every bit as good as most speakers that cost five figures. In fact, I've heard some in the high-five-figure range that did NOT sound better, just a little different. IMO the RS IIs are one of the greatest bargains in the whole audio field today.

Don't continue running them under-powered. To do so is Russian roulette with three cylinders loaded. To crank them up when under-powered is basically Russian Roulette with all cylinders loaded; it's only a matter of a bit of trigger-squeezing time before the gun goes off.

Start off with something affordable but capable, like the Adcom 555 IIs. You can then either continue to enjoy them that way, or perhaps try different amps later on, when and as you can afford to.

Another possibility is bi-amping, but doing that well with the crossovers in the RS-II is rather complicated. I'd say leave them as-is, and stick to the few amps that can do them justice.

Congratulations on having a fine pair of speakers, and good luck getting them safely and well driven!

 

[whoaru99]

BTW, almost all pro amps are rated for operation into 2 ohms.

The QSCs I mentioned are 1,200wpc and 1,700wpc respectively, at 2 ohms.

Don't think you need this power? Think again.

 

[tubed]

I now believe having the best possible power source is beneficial for running any set of speakers. I have a pair of Polk SDA-1 that sound quite dynamic, but as volume level is increased to a still desirable "loud" level(it seemed apparent the speakers could "go louder"), my amplifier will go into protection mode. I bought a meter and checked the resistance reading and the SDA-1's measured 5.6 ohms without the interconect cable BUT only 2.9 ohms with the SDA cable connected....which seems like a highly demanding load at higher volumes.

 

[Arkay]

I just got a Soundcraftsmen PCR-800 but I am trying to power a pair of Infinity RS-II's. This amp doesnt seem to be up to the task. It starts clipping at what I would consider to be too low of a volume. I'm not rich, so I am looking for something in the 300-400 $ range. Thank for any replies.

Patrick

You need an amp with not only a lot of watts, but one with high-current capability even into 1-2 ohm loads, and preferably one with a good damping factor and higher slew rate. Not many amps come close to coping with these demands.

To stick with Soundcraftsmen, get an MA5002. Stable into 2-ohm loads; 375 watts per channel into 8 ohms and will peak at 1,000 watts when the speakers drop to the 1-2 ohm range. This amp CAN handle these speakers. Clipping indicator to keep you safe, but your ears will start bleeding around where it clips. Very good sound, very musical and strong. Unlikely to be within your budget on eBay, but you might get one locally through CL, etc... with a bit of luck (Karma!).

Adcom GA-555 (regular or MK II; the latter is better). Clear sound, but can sound a bit dry or clinical with some pre-amps. Works best with matching Adcom preamp (GP-555). Safest to run it straight, NOT in bridged mode, with these speakers, but before learning that I ran them bridged (one amp per speaker) with RS IIs and got away with it for a while. I don't recommend it, though, as the manufacturer advises against using bridged mode into such low impedance. Also has clipping indicator. You should be able to find one within your budget, although around the high end of it. Probably the easiest and cheapest way to safely drive these speakers.

Other amps that can handle these, but which would probably would exceed your budget, would include:
Ampzilla
Carver Sunfire
Krell
Bryston
McIntosh (some models)

These speakers are worth powering right, even though to do so will usually cost more than the speakers themselves. Powered right and in the right listening space, they sound every bit as good as most speakers that cost five figures. In fact, I've heard some in the high-five-figure range that did NOT sound better, just a little different. IMO the RS IIs are one of the greatest bargains in the whole audio field today.

Don't continue running them under-powered. To do so is Russian roulette with three cylinders loaded. To crank them up when under-powered is basically Russian Roulette with all cylinders loaded; it's only a matter of a bit of trigger-squeezing time before the gun goes off.

Start off with something affordable but capable, like the Adcom 555 IIs. You can then either continue to enjoy them that way, or perhaps try different amps later on, when and as you can afford to.

Another possibility is bi-amping, but doing that well with the crossovers in the RS-II is rather complicated. I'd say leave them as-is, and stick to the few amps that can do them justice.

Congratulations on having a fine pair of speakers, and good luck getting them safely and well driven!

 

[jstang]

I was just about to say an MA5002 or MA5002A..... I have the MA5002 that I picked up for 320$....Very nice sounding.

To stick with Soundcraftsmen, get an MA5002. Stable into 2-ohm loads; 375 watts per channel into 8 ohms and will peak at 1,000 watts when the speakers drop to the 1-2 ohm range. This amp CAN handle these speakers. Clipping indicator to keep you safe, but your ears will start bleeding around where it clips. Very good sound, very musical and strong. Unlikely to be within your budget on eBay, but you might get one locally through CL, etc... with a bit of luck (Karma!).

 

[whoaru99]

An amplifer capable of producing more watts is also capable of producing more current.

Amplifier A produces 250wpc, amplifer B produces 500wpc. Amplifier B is more "high current" than amplifer A because it is capable of producing more watts.

If one wants more current buy more watts.

 

[SoCal Sam]

Ya, I was going to say a Mac until I noticed the $300 - $400 price limit. I like the PC2002M suggestion, but am pretty sure it isn't rated to 2 ohm. I'm going to go with what whoaru99 said, and guess that you are just running out of gas -- in which case the Yamaha would be a great amp to get. Better yet, get two, and bridge 'em (aren't they around 600 - 700W bridged?).

Figure 3 on page 5 of the PC2002M manual shows power peaks at 2 ohm. I'm over the attachment limit so if you would like to see the graph, shoot me a PM with your email and I'll send it over.

 

[SoCal Sam]

An amplifer capable of producing more watts is also capable of producing more current.

Amplifier A produces 250wpc, amplifer B produces 500wpc. Amplifier B is more "high current" than amplifer A because it is capable of producing more watts.

If one wants more current buy more watts.

At a given load, true. However, can the amp deliver more power when the load dips? The best double from 8 to 4 ohm and then double again from 4 to 2.

 

[whoaru99]

That's why you have to look at or know the power ratings. My assumption was that the amps are being compared at the same impedance.

If amp B produces more current at "X" impedance than amp A does, amp B is your higher current amp.

If amp A somehow reverses those positions at lower impedance, then amp A is your hiigher current amp at lower impedances.

As far as the doubling down amp thing, I think much of that is achived by specsmanship/sandbagging the higher impedance power ratings. Don't get me wrong, they're good amps, just the higher impedance power ratings are lilely listed under spec to give the appearance of doubling down.

 

[M Jarve]

I'm surprised no one has mentioned the original "cheap, bullet-proof" amp, the Peavey CS-800. The older versions weigh about 1-metric ton and will play into a #2 philips screwdriver all day, if you like. Does not sound half-bad at that, though it is not, perhaps, the last word in high-fidelity. I did like it better than the QSC PLX-2402 I had. The QSC, despite its incredible power, seemed to lack "spirit", lets say.

Both the PLX-2402 and the CS-800 (old versions) are available in the $300-$400 range or less.

 

[Elliot Thompson]

The dc offset is around 25mV per side
The fan doesnt kick into high speed from what I have seen. I took the cover off of the amp and blew a fan right onto the fins to see if that would help. It may have helped but I dont think it was running hot anyway.
I have not tried it with other drivers, yet. I will do that on Monday when I am done with my weekend work shift.
The clip indicators begin to faintly illuminate at a lower moderate volume level. If I push it further (only did this once) it distorts and blew one of the tweeter fuses. I wont do that again

Your speakers were designed to sound good, not loud and good. Blowing the fuse means it is getting too much power and, I am certain going for more power will definitely destroy those speakers.

It took me a while to find those speakers. Once I did, they look inefficient. Driving a Soundcraftsmen @ 2 ohms per channel yields 900 watts total @ "true clip." If you are not getting enough volume, your speakers are at fault, not the amplifier.

When the Soundcraftsmen throttles back (Current limit itself), it will do so by reducing its output by 50% momentary. Long enough for you to hear the difference. Your experience is not that but driving inefficient speakers in which, you are clipping the amplifier and, blowing your speakers fuses during the process.

As far as the manual states, you should feed these speakers 75 (minimum) – 300 (maximum) watts @ 4 ohms. The Soundcraftsmen delivers 300 watts per channel @ 4 ohms per channel from 20- 20,000 kHz with no more than 0.05% THD

At clip, it is much higher which is why you blew the speakers fuse. You will need to either accept that these speakers will never play loud, or use higher efficient speakers.

Here is the manual btw http://www.davidsaudio.com/rs2a-b-manual.pdf

Best Regards,

 

[Tedrick]

Your speakers were designed to sound good, not loud and good. Blowing the fuse means it is getting too much power and, I am certain going for more power will definitely destroy those speakers.

This is not entirely true. Power will not destroy these speakers, clipping caused by using an amp that is either UNDER-powered or just not up to the task of giving the current these speakers need will. If you feed them with an amp that has the necessary cahones, they will play plenty load. I have RS-IIb's, the next generation of this speaker, and I know this to be the case.

 

[Elliot Thompson]

This is not entirely true. Power will not destroy these speakers, clipping caused by using an amp that is either UNDER-powered or just not up to the task of giving the current these speakers need will. If you feed them with an amp that has the necessary cahones, they will play plenty load. I have RS-IIb's, the next generation of this speaker, and I know this to be the case.

Did you read the Infinity Manual in which they state 75 - 300 watts? The Soundcraftsmen falls within Infinity's optimum recommendation to power these speakers.

Can you guarantee Patrick will not lose his speakers once he exceeds the recommended wattage from Infinity?

Based on the wattage figures they more than likely follow these measures;

75 watts RMS

150 watts Program

300 watts Peak

The Soundcraftsmen delivers 300 watts per channel @ 4 ohms from 20 - 20,000 kHz with no more than 0.05% THD.

Where are these speakers being underpowered?

Could it be that your interpretation of loud and Patrick's interpretation of loud is two different things?

Best Regards,

 

[Patrick620]

I was hoping that someone would chime in on the "loudness" issue, thanks, guys.
Here is what I have to say about this. These RS-II's....I couldnt be happier with these speakers' sound quality. They are probably the best sounding speakers that I have ever owned, but I could be happier with the volume. So, is it the amp or the speakers? Well, I have not swapped out these pieces of equipment with other pieces to determine that, yet. This PCR-800 amp (sticking with the forum topic) powers them in a way that is not bad. What I mean by that is the experience that I get when using this combo is unlike any that I have had. The volume may not be "in your face" but it seems that the volume level is nearly the same if I leave the room and listen from a whole other room. The sound really seems to carry. I think the amp has some power to it. Maybe not enough, but a fair amount. I know that the overhead lights dim just a bit with the beat of the music so this indicates that its USING a good amount of power (newer home on a regular 15A circuit). It's probably not the most efficient amp ever made, but it's probably not the worst either. Having said all of that, I think the overall sound from this combo is not bad, it is more unique than bad. Not what I am used to. I have a Proton AM-455 hooked up to a pair of Klipsch KG-2's for my bedroom setup that really cranks it out. Granted the speakers are pretty efficient and the room is smaller, too. My gut tells me that these speakers would handle more power. I think a more powerful amp would be safer for the speakers, too. I'm considering a Crown (not sure which model), an Adcom 555 MKII, or even possibly and old boat anchor Peavy CS800. I am in no huge hurry to get a new amp, but I will be getting one sooner rather than later. In the meantime I have decided to restore the speakers and continue researching what I will use to power them. I also want to thank everyone for informing me and educating me. I am learning a lot and am enjoying the whole process a great deal. :thmbsp:

Patrick

 

[Patrick620]

Could it be that your interpretation of loud and Patrick's interpretation of loud is two different things?

LOL, I think that the rest of my household would go along with that statement. BTW, Elliot, I can really appreciate your comments and concerns. I do not want to overpower these speakers. I guess my goal would be to find the maximum safe level.

 

[whoaru99]

...My gut tells me that these speakers would handle more power. I think a more powerful amp would be safer for the speakers, too. I'm considering a Crown (not sure which model), an Adcom 555 MKII, or even possibly and old boat anchor Peavy CS800. I am in no huge hurry to get a new amp, but I will be getting one sooner rather than later. In the meantime I have decided to restore the speakers and continue researching what I will use to power them. I also want to thank everyone for informing me and educating me. I am learning a lot and am enjoying the whole process a great deal. :thmbsp:

Patrick

Bear in mind that it generally takes 2-3dB increase in level to make a noticeable (to most people) increase in overall volume. A 3dB increase means twice as much power.

While I'm sure all the amps mentioned above are good amps, they are of similar power to what you already have. 20 or 30 watts one way or the other is pretty inconsequential at this level.

This is why I recommended something like the QSC PLX 3402 because it's in a clearly different power class. It has lots of power and good sound and reasonably affordable (have to act quick though because they usually sell fast). You don't have to use all the power, but it's there to cover dynamics/peaks which require tons of it when using low senstivity speakers.

Also, you may want to consider a dedicated electrical circuit. Doesn't sound good that lights are dimming with the PCR800.

If I were closer, I'd bring over one of the QSCs and check it out.

Something you can do is check for sound equipment rentals aournd your area and see what kind of amps they have. Usually it's cheap enough to rent one even two (big gun and little brother, perhaps??) of these pro amps for a weekend.

 

[Jon_Logan]

Too little power and you will clip the amp at high levels. Too much power and the woofer is in danger. For really really loud, you are walking a knife edge.

I think the Infinity's may be enjoyed 'loud', but not 'loouud'. You are pointing yourself in the direction PA speakers with compression driver mids and tweets.

A couple things that you can try are:

1. Get closer to your speakers.
2. Make your listening room less absorbent.
3. Get another pair of the Infinty's (with amps etc) and double your system.

If that doesn't do it, your looking at a speaker system where the woofers have sensitivities of 92dBspl/meter driven with 2.82Vrms, or better.

 

[totem]

Still running the eq. on your system?

 

[Patrick620]

I tried it with and without. It seems to make no difference as to when it wants to clip. The gain is turned to about half on the EQ. I like the sound better with the EQ. There is a Crown CE-1000 here on CL that I am thinking about but I am going to do more research before buying. I'm gathering that adding an EQ to the mix can cause problems? I really like to have more control over the sound than what standard bass and treble controls can offer.