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Yamaha AX-700 versus AX-700U with Infinity Crescendo CS3009 Speakers

Cutura's picture

Hi. First time posting. I have lurked for three months and want to thank all of you for the great education you have been giving me. You guys are truly fantastic!

I am just getting back into owning "traditional" 2 channel audio components as a recent empty nester. Prior to now I have only swum in Technics, Pioneer, Sony waters. So far, I have purchased a pristine pair of Infinity Crescendo CS3009s and a Yamaha AX-700. My intention is to keep the Crescendos long-term. The Yamaha's life span was unknown and is part of what I would like your help with.

First I would love clarification on what the Crescendos REALLY run at -- I have read 4 ohms and 6 ohms -- the manual says 8 ohms. Everyone agrees 8 is wrong. Can anyone definitively clarify the ohm rating of a Crescendo 3009?

Next, I can't find a manual for the Yamaha AX-700. So far, the AX-700U is getting all the manual love. The problem is, where HiFiEngine info represents the AX-700 as 110w at 8 ohms, I have found the 700U manual, representing the "U" at 160W/210W/280W (8/6/4ohms). What a difference!

Was that "U" that much of a tweak or is there a misprint somewhere?

And what is the 700's 6 ohm and 4 ohm rating?


Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

The U simply refers to the US variant (110V power supply/pass through AC outlets). All AX-700 models are rated identically at 110W per channel into 8 ohms/130W into 6 ohms (minimum continuous RMS power output, 20Hz-20KHz). Other stated figures are for short term, dynamic power output.

The service manual with specifications for the different variants is on the AX-700 library page.

Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Thanks JaS: That helps. So when/if (as I have come to think I believe) the Crescendo's operate at 4 ohm, how is the AX-700 responding?

And why does the 700/700U manual saw 160W at 8 ohm?

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Sorry, none of the literature I have for the AX-700 has a continuous power output rating for 4 ohms. Maybe it didn't measure well at 4 ohms so they left this out?

The other figures in the manual are the 'dynamic' power rating ie the maximum burst power for peaks with a 1kHz test tone. This says something about the overall rating of the circuit and the current reservoir, but isn't terribly useful when matching loudspeakers. Manufacturers and eBay sellers like this figure because it looks more impressive.

Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Thanks again.
(I feel my understanding inching forward)

I really wish I could learn what the Crescendos call for. They appear simply too rare to garner a solid opinion. No where can I find a straight forward "pairing thread".

I have found a couple of forum comments suggesting as low as 2 (at times), 4-6 on average, but then other comments in refute. I have not found enough collaborating commentary for a consensus. The manual says 8 ohms, but everyone disagrees with that and further claims Infinity had a reputation of mis-stating Ohm ratings.

Yeesh, I don't know who to believe nor how to figure this out!!

Is it possible to measure somehow? I can't imagine how much the machine costs nor what the skill is to produce an accurate chart.

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

The figure in the manual may or may not be correct, typos in manuals are common, as are different methods of testing.

To measure the nominal impedance (the figure manufacturers state for amplifier matching) you could use a frequency generator and an oscilloscope to plot a graph of impedance. You would then need to calculate the nominal impedance from the graph.

Alternatively you can just plug the speakers into your amplifier and see if it can drive them to the required level without getting unduly hot, or distorting? The loudspeaker specs are useful when shopping for an amplifier as they give a rough idea of what sort of power you will need to drive them hard. It's only when you hear the amplifier and speakers as a system in your room that you find out how well they really work together.

Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

The measurement method and equipment for determining the impedance myself is a whole new world to me and plenty intimidating, but I will give it some thought if no other way produces the answer.

I can say the Yamaha AX700 is IMPACTING at 12 o'clock. At least, the one time I thought to "see what it could do" at 12. After bout 30 seconds, all sound cut out, then it was back on 2-3 seconds later, as was I, on my feet turning down the dial!!
It had been at 11 o'clock for several minutes before I took it to 12. Neither 11 or 12 o'clock would have been comfortable listening for very long. It never really seemed distorted to me, the sound just shut off. Is that what is meant by clipping?

Anyway, the 700 never gets hot even throughout that trial.
In fact, even after hours of listening at robust levels, it is barely ever warm.
If it sounded better to me, I would not replace the 700 for "power".

However, imo the 700 is a little harsh in the mid and uppers and a little weak in the bass.
I believe this is also a characteristic of the Crescendos so perhaps the two together are bad blood?

Buy and try other amps would be great with unlimited budget and enough vintage units available. Neither appear to be the case to satisfy, where I have zero experience in amps to even put a target on the barn. Reading spec sheets is all I know.

Why amps don't all have 6 or 4 ohm ratings published is annoying. As I understand it, not all go to 4, or even 6, right?
So where I don't see it, does that mean it can't do it or that is just doesn't say it.
Conversely, some amps rate the same wattage across all impedance levels (unlike the 700, who's wattage increases as the impedance drops). So, again, unless the amp says what it is, it seems to me I can't count on it.

All the listening experience I have so far is this:
A McIntosh 2505/B&W pairing I recently auditioned didn't let "the sound out of the speaker", compared to my Infinity/Yamaha pairing. I supposed that is what is called "rounding" by so many. I might more simply say it needed volume even after the knob had run out.
A Classe Audio Ten/B&W pairing sounded more open like the Yamaha in the high/mids AND had more bass.

Does that mean I can bring it home to my Inifinity's and like it?

The Classe Audio Ten is 100W @ 8 ohm and I have no idea what at 6 or 4 ohm.

Thanks again (and in advance) to any who may have information or an opinion to help direct me in the best way to buy and try (from the right sandbox).

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Let me see if I can add something.

Infinity does have a history of not being totally up front about the impedance of their speakers. Very often some frequency ranges in the speaker are well below the stated "nominal" impedance. That makes them a more difficult load to drive, since the amplifier has to deliver considerably more current to the speaker.

As to the amp, the AX-700 and AX-700U have the same internal components; but differ in the power transformer's primary side. So, they should behave exactly the same.

Power ratings: This is more complicated. There are continuous power ratings, and there are dynamic power ratings. Back in 1973, there were all sorts of misleading advertised power ratings, so the Federal Trade Commission (FTC) stepped in and mandated how power could be rated and advertised. Power was to be measured with both channels driven into a resistive load after a 1 hour preconditioning at 1/3 rated power. This is a severe test and resulted in many companies derating existing amps, and in many cases, 4 ohm ratings disappeared. Your AX-700 is rated this way, and it's why there are only figures for 8 & 6 ohm loads. It's really a measure of the amplifier's thermal capability.

The Dynamic Power Rating can be stated in Watts or as Dynamic Headroom in dB above the continuous ratings. Some companies (NAD for one) give both figures. These are quite valid figures and tells you how the amplifier reacts to musical inputs, which are transient in nature and of short duration. Basically, the dynamic power rating is based on the idea that the amp can generate more than its continuous rating for short periods (like 200 milli-seconds) by using energy stored in the filter capacitors. And that's the rating you found of 160/2??/280 Watts at 8/4/2 ohms.

Clipping is when the input to the amp drives the amp to the point where it can't supply enough voltage, and the output shows flat tops on the output wave forms. The tops of the waves are "clipped" off. Severe clipping is audible as an added layer of high frequencies. Dynamic Power is an indication of the amp's resistance to clipping.

When you set the volume to 12 o'clock and the amp shut off, that was not clipping; but the amp's protection circuits shutting it down based on some rules Yamaha built into the amp. It's a combination of the amp's capability and the characteristics of the load.

More on the volume control. Contrary to popular belief, with most normal input levels, amps reach full power somewhere around 12-2 o'clock. The rest of the rotation is there for unusually weak input signals. So it's a good bet that at 12 o'clock you were very near full power. Not good for the amp or the speakers.

If the amp sounds good over most of its range and is a little weak in the bass, add a little bass boost - that's what the bass control is for, after all.

Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

@Gerald... It was getting to be about 120 degrees in here and you just opened the window -- THANKS, for the fresh air!
(I really appreciate your very thoughtful reply)

So between us, we don't, yet, know exactly what the Infinity's impedance is, on average, BUT "WE" sure do know now what the amp is doing!

Thank you Yamaha for printing both ratings to teach me about amps in the first integrated amp I stumble upon to start.

To clarify then, given the AX-700's continuous power ratings are 110W@8 and 130W@6 (with 4 DOA), what does that say about the match to my Crescendos?

Should the Infinity speakers be operating in the 6-4 ohm area, on a regular basis, even going to 2, at times, perhaps I am asking the AX-700 to perform in an ohm space Yamaha concluded it could only reach on a dynamic basis?
(by IHF Dynamic Headroom measuring method 160W@8; 210W@6; 280W@4: no rating@2)

Might this be why I describe my listening experience as music with an edge to it? Mostly, open and detailed, but a little harsh at times and lacking bass (where those 2 ohms would mostly live)?

If it is the case that I am really asking this amp to do more than it should, pushing the bass more seems like the wrong fix.

I am going to take a chance and go one question further on the presumption that I need more power... disagree with that if it is the wrong answer.

For speakers running 6-4 ohms, with "dynamic power" needed down to 2 ohms, where the listener (me) is more attracted to words like BIG soundstage, quick dynamics, open and detail (versus warm, rounded, etc) what is the power amp for me (and my Crescendos)?

Some amps currently on CL around me are:
McCormack DNA-1: RMS 185W@8; 370W@4; 600W@2 :: No dynamic information. (THD none given)
Yamaha B-2x: RMS 170W@8; 200W@6; 240W@4 :: No dynamic information. (THD .02%@8)
Musical Fidelity A3cr: RMS 120W@8; 210@4 :: No dynamic information. (THD .005% @1kHz 'A' weighted)
Bryston 4B: (the original) RMS (I think) 250W@8; 400W@4 :: No dynamic information.
Classe Audio TEN (DR10): RMS 100W@8; 200W@4 :: No dynamic information. (THD none given)
(integrated) Luxman L-430: RMS 105W@8 :: No dynamic information. (Can be pre-amp only -- no 6-4-2 RMS rating!!)

There are also McIntosh Amp, however the one I have listened to suggested to me it was too laid back. Just my impression, of course. It felt to me like the sound needed to be let loose out of the speaker.

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

I tried replying to your last post, and somehow it didn't "take". So, I'll try again.

First, I think you have enough power for normal listening, especially since you commented turning the volume to 11 or 12 o'clock was still too loud.

Your amp shutting down was not clipping; but the amp's protection circuits doing what they were programmed to do.

A common misconception exists about volume controls. With most amps, and a normal input signal, maximum output power occurs somewhere between 12 & 2 o'clock. The rest of the rotation is there for lower than normal signal levels.

Second, on this site, I looked at the service manual for your amp. It's a pretty straight forward design with a husky power supply. The manual gives dynamic power ratings for 8/6/4/2/1 ohms with 2 & 1 being 350 and 400 respectively.

Thirdly, I believe Infinity does have a reputation for both low impedances, and a bright top end. Your amp should be OK for the low impedances. As far as the brightness, try turning down the midrange and tweeter controls on the speaker (if they have them). If not there's the treble control.

Fourth, speaker placement is critical. Proximity to walls or large furniture has a lot to do with the bass power. So lets say your speakers are well out from the wall. Moving the speaker closer to the wall behind it will increase the bass output without using any more amp power. This affects the region below about 200 Hz. Moving the speaker closer to a corner will increase the bass still more. The distance between the speakers affects the lower midrange, and you can fine tune the range below 250 Hz by changing the spacing between them. For example, mine are about 8' apart measured to the center of the woofers. They are on a 12' wall in my condo's den and about 8" from the back wall and about 24" from the side walls. I have them toed in about 15 degrees each. Perception of the bass is also affected by where you sit. The closer to the opposite wall from the speakers, the stronger the bass will sound. The sound waves reach a pressure maximum when they hit a barrier, like a wall.



Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Jerry, I find a LOT of traction in your posts.
Thank you again. AND for trying even a second time.

Thus far, no tone adjustments have been made at the speaker or the amp.
The speakers have no crossover (tone) controls.
My source is CD, currently, and the Yamaha pre affords a CD Direct, which I have engaged.

My personal goal is twofold:
1. Start with content as close to the producer's mastering as affordable, which I understand to be HRA files.
2. Listen to those files through a system that faithfully transports, but does not touch, the content.

Tone controls would be for minor "seasonings to taste" from recording to recording, not system fixes.
Maybe knowing this helps the conversation. If not, it likely has bored everyone to death.

I believe I found the source of the power ratings you reference, not in the manual, but in a catalog, on this site.
I had missed those initially, though they are dynamic ratings. To quote you:

"'dynamic' power rating ie the maximum burst power for peaks with a 1kHz test tone. This says something about the overall rating of the circuit and the current reservoir, but isn't terribly useful when matching loudspeakers."

The AX-700U manual, the only one I find on this site, expresses 8 and 6 ohm rms output only.

While becoming more comfortable with the idea that the AX-700's power may be "adequate" (this morning's listening level was plenty at 8 o'clock), surely the amp protectively shutting down at 12 is not a good thing!
Symptoms suggest it may be adequate, but working near it's limits at 20Hz-20kHz, no?

I am going to move forward with speaker placement now. I had actually just started experimenting with that today. The Crescendos do not have controls, but they do have a passive port and they have ben far from 3-4' from all walls.

Thanks again,

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...


Thought I'd answer one more time. Specifically about tone controls, and system response.

I've been hanging out on-line at the Audio Asylum in the Vintage Forum. I've been a hi-fi nut since 1953, so I've seen a lot of stuff come and go, and big changes in the technology. I'm a graduate engineer, now retired, and until about 1967, I thought I understood audio. In '67, I went to a co-worker's house, and he had this great sounding stereo system. The speakers were KLH 17's and he was driving them with a DIY Fisher tube amp he built from a kit. That was a Friday and the next morning I showed up at the store where he bought the stuff. They had the usual "speaker wall" and I tried a lot of them; but kept coming back to the 17's. The salesman asked if I needed any gear besides the speakers, and I admitted that I had a stereo preamp and one power amp and one speaker, and a dual turntable with a mono cartridge. So he suggested the KLH Model 20 Compact System might be a good idea as it used the same speakers and had the electronics and turntable built into a single unit. Anyhow he gave me a bunch of literature on the Model 20. In the packet was a review of the Model 20, and the author described it and talked about the sound and the fact that they had tried other speakers with the electronics, and the speakers with other electronics, and nothing sounded as good as the Model 20. He then explained it was because the speakers and electronics were engineered together as a complementary package. Poof!!! The light bulb came on over my head.

It isn't about component quality; but about matching. Aha! I thought, I'm an engineer, and I understand the principles of Systems Engineering, so if I put more $$$ into the system, I should be able to do even better than the KLH Model 20. (bear with me, this IS going someplace) That began an Odyssey of many years, as I had a lot of learning to do; and I put together a lot of systems as I was learning.

OK, the point here is that time spent learning and in matching is more important than money. The matching process usually starts with the speakers and works its way back up the chain to the source. You also have to consider the room as part of the system. It also turns out that in putting components together, the errors at the interface between components are often larger than the errors in the components - and that's the province of Systems Engineering.

In your speakers, there are no midrange and tweeter adjustments. Yet the room they are in and often the necessities of living in the room and the effect on placement, means they will sound different in different rooms. So I disagree a bit with your not wanting to use the tone controls for system balancing. By the way, unless you use a very sophisticated digital room compensation system, you cannot equalize a room. You can, however, equalize your speakers and electronics. The biggest thing being the absorption of the room and it's furnishings in the upper frequencies. Most treble controls are pretty good for that. In the speakers I'm currently using, which I built, I used a rotary control (an L-pad) on the tweeter so I can balance the sound in different rooms and with different electronics. Then, I can run the electronics flat as you intend to do. Well, almost. With one set of electronics, the speakers need the bass control at between 1 & 2 o'clock. At that setting the bass sounds right, and the system measures very, very well. With another set of electronics, the bass is OK and the system measures very, very well. A system should measure AND sound well if it's to be used for a wide variety of music.

I guess what I'm saying is that without controls on the speaker, what else do you have to balance the system with? Placement will mostly affect lower frequencies. I realize that modern speakers tend not to provide controls. So the bass and treble controls are your solution. I do have to admit I'd rather have the tone controls set flat or bypassed, as it means I got the speakers right. But it also means I'd be starting over if I move the speakers to a different room.

If I can be of help; please contact me.



Cutura's picture

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...

Thanks Again, Jerry

I'll be playing around much more this weekend, but moving the speakers to about 6" from the back wall about quadrupled the bass and really mellowed the speakers. I also have come to realize the "loudness" control on this amp doesn't "loud" audio, it "unlouds" the highs and lows. I will be playing with that some too, and the treble, to take the Crescendo's emits down a notch.

My absolute biggest concern, right now is what I think is clipping. "crackling" -- what one's saliva does in one's mouth or the crumpling of paper -- at a kind of "hurt your ear high level" is what I hear from my speakers when I push just a little (9 o'clock). When the vocal dynamic peaks comes the crackle. It hurts for a nano sec.

I believe I have answered my own question on this one. Just thought I'd let you know about the bass improvement.

Re: Yamaha AX-700 versus AX-700U with Infinity Crescendo ...


The crackling sounds like the audible evidence of clipping. At that low level, that's not good. Turn the Loudness control all the way down and just use the volume control.

Normally "loudness" is just a single push button that turns it ON or OFF. It's supposed to compensate for your ear's lower sensitivity to bass and treble at low listening levels. But if it's just a button, it's pure coincidence if it happens to match your speakers in your room. Yamaha did it better with a second rotary control that can match the amount of compensation to the volume you're playing at. But you are still working with what Yamaha's gurus thought was the right shape to the compensation. Usually the best part of Loudness is the control that turns it off.

From your comments, placement seems to have solved the bass issue. Good!

Things do seem to be improving, although the crackling is a worry.