Just how much power is really needed?

[Ross6860]

RS5b
RSiiia
RSii
RSM Reference Studio Monitor

I own the RS5b and a pair of RSii are coming whenever I decide to transport. The others are just for general info...

Is a Sansui 7000 or Technics SA-5570 "big enough" to really drive these? Not sure if the Sansui is really rated for 4 ohms. The Technics is 90 wpc @ 4 ohms

Not a huge space, not real loud, but I want to hear what they are really capable of.

 

[whoaru99]

Not real loud but what they're capable of is a bit of a convolution, IMO.

 

[Ross6860]

Not real loud but what they're capable of is a bit of a convolution, IMO.

Not sure what that statement means, either?

Not real loud as in not trying to provide music for a party, just a reasonable listening experience in an otherwise quiet house. Loud enough to hear "all" of the content (or all that my upstream gear is capable of sending to the speakers, and that the speakers are capable of reproducing.

For example, my Sansui 7000 on "3 to 3.5" pushing my KLH 5's is plenty loud for a nice listening experience. Same for my AR2a's. Maybe a little less volume listening to my Klipsch Chorus ii's. Pretty sure I'm hearing what they can deliver. Not so sure with my RS5b's, and concerned about the RSii's with some of my gear.

Speakers are 9'-10' apart, 3 feet from the rear wall and 12' from the seat. Room is 14'x32'

Only asking because of the reputation of the vintage Infinities for being both hard to drive and hard on amplifiers.

What I listed are my largest receivers. I also have a 50 wpc tube integrated. I know my SS JBL amps are "big enough", but they are not really easy to place, and not very pretty.

 

[whoaru99]

Convolution inasmuch as twisted in what it really means.

On one hand, the speakers are likely most accurate with just a watt or two of power but may be more enjoyable with ten or one hundred times that.

 

[AZDean]

It's not just watts, it's current capability. RSii drop to 2 ohms at some frequencies. I would be very surprised if the Technics could play them at even a moderate volume without blowing up. Try them out, if those receivers get really hot, you need to upgrade. If you like older Japanese gear, the Onkyo M504 will work nicely. A lot of the Onkyo Integra stuff had pretty stout power supplies and current capability.

 

[tubed]

Recommend watts 35 to 250 watt amplifiers.
I agree, play at low volume and check for abnormal heat as volume level is increased.
The RS II and IIIa deserve the best you can give them.

 

[whoaru99]

It's not just watts, it's current capability.

The two are directly related. More watts = more current, more current = more watts.

But, yes, at 2 ohms a decent amp helps. My Thiel CS3.6 run about ~2.5 ohms over most of the audio range but nothing, including some really tiny amps, has ever blow up on them. OTOH, I don't expect a tiny amp to run them at concert hall levels for hours on end so that probably factors in.

 

[goodolpg]

I ran my RSM's with 90, 120, and 125 wpc receivers, they were rated for 4 ohm speakers, no problems.
The RS II's could use more power/current as they do dip quite low in impedence.


No idea on the other models listed.

 

[AZDean]

The RS IIs drop to 2 ohms between 6 and 10kz, and is around 3 ohms through much of the rest of the band. (Didn't have the review handy when I replied last night.)

As far as the current goes, it's not as simple as watts = current. Half the impedance requires twice the current to produce the same watts. So there are some high end amplifiers that do this ideally in that they produce 100 watts at 8 ohms, 200 watts at 4, and 400 at 2, but most don't and those receivers certainly don't. That Technics for example is 85 watts at 8 ohms, and I think it's 90 watts at 4 ohms. They don't have specs at 2, but its probably no more than 90 and could even be considerably less. (That's the limit of my knowledge on the subject by the way Bottom line, try it, but pay attention to two things, the heat in the receiver. If it's higher than normal, I would turn it off. And don't let the amp clip or distort. When I sold this stuff in the 80s, we had a pair of RS IIbs in the showroom. A Kenwood M2a (220 watts at 8 ohms) couldn't even play moderately loud without clipping. It would clip and blow the speaker fuses. A Hafler 500 would clip on peaks. Biamping with the Hafler 500 and a Hafler XL280 would as well (390 watts a side!) The Onkyo M504 didn't. The Onkyo was 165 watts at 8 ohms and something like 385 watts at 2. The Hafler would have been fine at home for most people though, as that was an extreme example.

The other reason though for looking for some better separates, these RSIIs are high resolution speakers and quite revealing. You'll simply get better sound. I would look for used Adcom, like a 555 or Parasound 1600a. Both are pretty good at delivering high current and are fairly easy to find at a reasonable price.

 

[whoaru99]

As far as the current goes, it's not as simple as watts = current.

Of course not, but that's not what I said.

 

[Bahamayellow]

I tried running my infinity 8.1s with a Jvc 100 watt reciever and it couldn't cut the mustard. At higher volumes it really started distorting. Luckily a friend of mine told me it didn't sound right. One forum said I need at least 300 watts to make them sound their best and the louder they go the sweeter it sounds. I went with a bi-amp mode with 500 watts a speaker. 250 split. I like my Sansui 7000 and it really cranks my vintage advents and smaller Infinitys but is no match for the larger Infinity floor standers. The tube intergrated might b your best bet. Let us know how it sounds. We love pics, show us your setup when it's ready. Sorry don't have a pic of my 8.1s but here is a pic of my Infinity K9s.



Ok found a pic of my 8.1 setup.

 

[rdka]

The pure class A amps dip down and handle that drop in ohms. They are not cheap. Or a powerful tube amp--like 75 watts or so.

But it's like Arnie Nudell said getting the numbers to work is where the work starts. So an amp meeting the criteria to handle the dips--and what kind of music you play enters into the equation as well and not something to ignore. No high end store plays thrasher metal to highlight their equipment. More like soft syrupy jazz or a string quartet. Elevator music as far as dynamics go. That is a consideration for you.

Next is getting into the sound of that amp > the numbers.

 

[savatage1973]

As far as the current goes, it's not as simple as watts = current. Half the impedance requires twice the current to produce the same watts. So there are some high end amplifiers that do this ideally in that they produce 100 watts at 8 ohms, 200 watts at 4, and 400 at 2, but most don't and those receivers certainly don't.

YUP--Ohm's Law is a triangle--so as impedance drops, current demand increases in order to maintain voltage to equal watts, the amp must be much more robust. When I got my first pair of Kappa 9's, we tried them on two Carver M 4.0t amps (biamping with 450wpc amps)--promptly sent both amps into protection. Put them on a pair of Aragon 2004 amps (100wpc) and could crank the hell out of them. My current pair of Kappa 9's are running on 4 Krell KMA 160 monoblocs (160w each @ 8ohms, but double down as far as 1280w each @ 1ohm).

I would look for used Adcom, like a 555

Be aware that Adcom 555's do not have ANY speaker protection, and they are aging and prone to failure (do a little research). Yes, they can be had relatively inexpensively and are up to the task, but make sure they have been thoroughly gone through and known issues addressed. If not, you may end up with full DC rail voltage directly into your speakers.

 

[slimpikkins]

I have the RSII and RSIIb and find them easy to drive compared to my RS2.5 and Qls1. I own a kenwood M2 and drives them (rsII and IIb) easily. Any solid state amp with a robust ps should drive them nicely and if it blows up I don't want it anyway. I good amp can be found on cl for a few hundred bucks. Instead of doing a few hundred $$ of damage on that receiver find a decent used amp. You don't have to spend a fortune to make the RSII sound full bodied and balance. Of course you could but most guys fooling around with 30 year old speakers don't have a fortune. Old Infinty speakers (talking about the big ones) were not meant to be used with receivers.
Jim

 

[Ross6860]

Thanks, all. I figured the receivers may be a little shy for some of these speakers.

Looks like the JBL UREIs to drive these. 150 wpc @ 8 ohms, 300 wpc @ 4 ohms, 45 lbs each, they can be bridged or run in dual mono, so until I upgrade these will have to suffice as "big iron" for me.

 

[chef free]

McIntosh amps handle anything!

 

[whoaru99]

YUP--Ohm's Law is a triangle--so as impedance drops...

Indeed, but that is not the point I was making.

At any given impedance, more watts inherently means more current and more current inherently means more watts. You don't move the bar midstream to make apples to oranges comparison.

My Levinson and Audio Reasearch are "doubling down" sort of amps but so what? My bigger pro amps don't "double down" but put out more current at 2 ohms than either the Levinson or the AR simply because they put out more power at 2 ohms.

 

[savatage1973]

At any given impedance, more watts inherently means more current and more current inherently means more watts.

With the kind of amps you mention, then you have to be able to realize that a very robust power supply (current) is required to maintain rail voltages as impedance drops. Many (if not most) are not capable of that--that is more what I was getting at. Most amps are not stable at or capable of driving very low impedances.

 

[sberger]

With the kind of amps you mention, then you have to be able to realize that a very robust power supply (current) is required to maintain rail voltages as impedance drops. Many (if not most) are not capable of that--that is more what I was getting at. Most amps are not stable at or capable of driving very low impedances.

Pro amps are. That's why they(mostly the Crown XLS series and newer QSC amps) are well liked and recommended by many over at the Classic Speaker Pages to drive many of the AR classic line. LIke the RS line, quite difficult to drive. The pro amps that I've mentioned can be had for relatively cheap, and sound quite good, very neutral.

McIntosh amps handle anything!

I'm finding this out first hand. Of course, they ain't in the same price category as the pro amps I referenced.

 

[whoaru99]

McIntosh is a bit of a different situation though with the output transfomers/autoformers.

While they still respond similarly to other amps with swings of speaker impedance, their nominal loading is much more consistent.

Connect a 2 ohm load to the 2 ohm tap, the amp output stage runs at 3.5 ohms.

Connect a 4 ohm load to the 4 ohm tap, the amp output stage runs at 3.5 ohms.

Connect an 8 ohm load to the 8 ohm tap, the amp output stage runs at 3.5 ohms.

In that vein, I've always wanted to try a pair of the Speltz autoformers with one of my pro amps just to see how that works out. Too much $ though for a short experiment.