Can my MC275 power speakers with 91db sensitivity

I am looking to buy some songs faber cremona speakers with the following specs:

91 dB SPL (2,83 V/1m).

4 ohm.

I have the most recent MC275. Would my amp have enough power?
More than plenty. To me the Mac sounds more SS than tube, but they are a good amp and run cool. Don't worry about power, you'll have lots in resreve. Best of luck.
First, as a point of information, keep in mind that since 2.83 volts into 4 ohms corresponds to 2 watts, the speakers will just put out 88 db for an input of 1 watt, at 1 meter. That is particularly significant in the case of a tube amp such as the MC275, since tube amps generally cannot supply much more power into 4 ohms than into 8 ohms. (For 8 ohm speakers this is not an issue, because 2.83 volts into 8 ohms corresponds to 1 watt).

It can be calculated that 75 watts into the two speakers will result in an SPL of around 100 db at a distance of about 10 feet, neglecting room reflections and thermal compression that may occur in the speakers at high volumes. That is good enough for most listeners with most recordings.

However, if you listen to recordings having particularly wide dynamic range (the DIFFERENCE in volume between the softest and the loudest notes), such as some well engineered, minimally compressed classical symphonic recordings, you might find the amp running out of steam on occasional dynamic peaks. If your listening is mainly to recordings that are highly compressed and/or have little dynamic range, such as most rock recordings, and you don't listen at unusually high volume levels or at an unusually great distance, you won't have a problem.

Perhaps a more important concern, though, is what the amplifier will sound like when driving the speakers. If the speakers are the same version of the Cremona that John Atkinson measured here, or if they are a different version having similar impedance characteristics, I would have some concern that their impedance characteristics in some parts of the bass region might be a bit difficult for this amp to deal with gracefully. Note that the impedance magnitude is only around 3 ohms from 80 to 200 Hz (where a lot of power is often required), and as JA notes there is a very challenging phase angle just below that region. And, not surprisingly given those characteristics, I see that JA mentions that the Cremonas "seemed more sensitive than normal to amplifier choice."

Hopefully someone who has tried this particular combination will comment further. Although, again, the dynamic range of the kinds of recordings that are listened to by the particular individual, and the listening distance, are important variables.

-- Al
Wow. Thank you Al for the informative response. (I feel like I might be given a test on your post at the end of the semester). I primarily listen to blue note jazz records, female vocal records (ella, diana krall, billie holiday, etc), and classical. All on vinyl. Perhaps I should look for a less sensitive speaker? Or, could I solve this issue by adding a second amp? Please note that I could not add a second amp for long time.
I see that the amp is rated to deliver 150 watts into 2, 4, or 8 ohms in paralleled mono mode. So adding a second amp might very well be beneficial, but given the expense and the wait that would be involved, as well as some remaining uncertainty, personally I would look for a different speaker that has more benign impedance characteristics. Unless an audition of the particular combination turns out to be possible, or persuasive anecdotal indications about the particular combination turn up.

In any event, good luck as you proceed. Regards,
-- Al
Could you recommend a such a speaker?
My recommendation would be to try Tannoy, something like the Kensington, which, if you find on the used market, should be similar in price to used Cremonas, or maybe even less.

Although my Tannoy HPD 315's (12" Dual Concentric) are custom built, their drive characteristics probably aren't too different from the Kensingtons.

The point being, I am able use two quite different amps to successfully drive them in a fairly large room (16' X 34' W/cathedral ceiling). A very powerful VAC PA 35.35 push-pull EL 34 amp @35Wpc, and a SET 300B amp at 9Wpc.

Try to get out and audition some Tannoy speakers, and see what you think.
Could you recommend a such a speaker?
Some of the following may be significantly more expensive than the Cremona, and/or unlikely to be frequently available used, but fwiw most or all of the models offered by the following manufacturers would be suitable matches, and are generally well regarded:

Tannoy (as Dan recommended), Daedalus, Coincident, Audiokinesis, Audio Note, Devore, Zu Audio, Tonian, Horning.

It might also be worthwhile to search "MC275" in the Audiogon virtual systems section to see what speakers others are using with that amp.

-- Al
Dear Al,

I just saw that their updated (and better looking) speaker, the Olympica III, has a lower sensitivity:
90 dB SPL (2.83 V/1m). NOMINAL

4 ohm.

50W – 300W, without clipping.

Perhaps these would be a better match for my amp?
I couldn't find an impedance curve for the Olympica III, so I'm not sure. But given its 4 ohm nominal impedance and sensitivity that is similar to the Cremona (1 db is a trivial difference, and in this case is in the wrong direction), without further information I would not have confidence that it would be a good match.

To be sure it's clear, everything else being equal a higher sensitivity (defined as SPL as a function of input voltage) would work in your favor. Note that the negative reference to greater sensitivity in the John Atkinson statement I quoted referred to sensitivity to amplifier choice, not to SPL sensitivity.

Also, I see that the Olympica III is listed at $13.5K. There are lots of good choices in that price range which can be confidently predicted to be good matches, including models from many of the manufacturers I mentioned above.

-- Al
Remember that the 75 watt rating is conservitive on the Mac 275. It's more like 90.
I listen to type of music and the mc275 has no problem powring my Dynaudio c1 signature 85db/1watt sensitivity
Polk432, the MC275 sounds more like solid state than tube? You mean that those Binghamton NY engineers from 1960 found how to make modern SS sound with tubes, only for modern tube amp manufacturers to go back sound? And in 1970 when McIntosh moved to transistors and everyone said they sounded terrible, they just got SS wrong? Sorry, not trying to be a jerk, but (as I have posted here and elsewhere) when I read a review about the greatest new SS amp that "sounds amazingly like tubes" and the greatest new tube amp that "sounds amazingly like SS" it makes us all sound crazy. One interpretation, as others have made, is that tube amps have high amounts of harmonic distortion. And therefore, if a tube amp from 1958 sounds like SS perhaps they were well manufactured and accurate instruments. Audiophilia...
I should add, I realize that the OP has the latest model of the MC275. In which case I second what I said above - "tube amps sound like SS." Then why buy tubes when you can buy SS. By the way, I'm running a 'vintage' MC240 right now, and have had side by side an ARC SS amp, and have trouble telling the difference between the two amps. Perhaps a well engineered amplifier sounds like another well engineered amplifier.
Jimmy, are you saying that there is a noticeable difference between tube and SS, or are you saying that there is not per se a difference, because a good amp sounds like a good amp. I ask, primarily because if there is no longer an inherent difference in the sound, I will save myself a lot of trouble and go with SS (or maybe not, I love the look of my MC275).
I have no experience with the MC275, but from a technical standpoint I suspect that there is some validity to Polk432's point. The current (Mark VI) version of that amp has a specified damping factor of 22, which is unusually high for a tube amp. Correspondingly, its output impedance is unusually low for a tube amp. That suggests that its design utilizes a greater than average amount of feedback for a tube amp.

Everything else being equal, all of that will shift its sonic character in the direction of being more akin to typical solid state sonics than would otherwise be the case. In numerous ways: A reduction in effects on frequency response flatness resulting from interaction between amplifier output impedance and variation of speaker impedance as a function of frequency; reduced Total Harmonic Distortion (THD); better bass damping than would otherwise be the case; increased Transient Intermodulation Distortion (TIM); a reduction in some lower order harmonic distortion components that tend to be numerically greatest but are relatively inoffensive; and an increase in some higher order harmonic distortion components that tend to be numerically smaller but are more offensive.

Elegal, re your last question, if you want to consider going to a different amplifier you should settle on a choice of speakers first, and then choose an amplifier that will be synergistic with it. Some speakers are designed to sound best with solid state amps, some are designed to sound best with tube amps, and some will do fine either way. The Daedalus speakers I use are an example of a design that will do fine either way. Their output will reflect the intrinsic sonic character of the amplifier that is driving them, but there will be no issues relating to amplifier-speaker interactions with either type of amplifier.

-- Al
I believe the original Cremona were rated at 90dB and the Cremona M at 91dB. The article that Al linked to was for the original Cremona. I believe the M are in fact easier to drive than the original Cremona. I have the original Cremona and concur that they are picky about amplifiers. I tried many amps and ended up with a Levinson 432, which does 400 watts are 8 ohm and 800 watts at 4 ohmns.

I would be cautious of your amp with the original Cremona, but it might be OK for the Cremona M. Unfortunately, I do not believe that Atkinson ever measured the M.
Jimmy, I have owned the Mac275 and the MC7270 SS amp. Both were good amps, but the Mac sounds more SS than tube especially when compared to my Cary V12R and CAD120's amps. One thing I really liked about the 275 is that it ran so much cooler than the Carys, just didn't have the warmth.
It can but probably not optimally along the lines related by Al.

That's not to say it won't sound good or meet your needs/expectations, only that you have a good chance of doing better in terms of both volume sans clipping and balanced and clean bass response and lower distortion otherwise as well perhaps to the extent that matters if you become so inclined.

So you can look at these things from the perspective of ideal technical matches that maximize performance, ie the perspective of intelligent "audiophiles" for the most part, or from the perspective of does it sound "good" or "good enough". Improving usually comes at some cost.

So its very much the oft cited "your mileage may vary" type scenario.

If that bothers you, then probably better to seek out different speakers that are more efficient and tube amp friendly in general.

Al's speaker recommendations are good ones. I might toss in Triangle and many Focal/JM Lab speaker models as possibilities.

Even Magneplanars could work very well with a tube amp like that, especially if very high volumes are not a concern.

OHM is another line that is perhaps not as tube amp friendly as some, but offers good value and decent performance with a higher power tube amp.

Adding a powered sub or two and offloading the low bass to that opens up a lot of additional popular speakers choices. That's a popular option for many OHM owners that use tube amps in some cases (some might go sans sub)and also for most any good quality speaker, including SOnus Faber.

Also, most any good quality horn loaded high efficiency speaker (mid 90s db efficient or higher) would be very good technical matches for that amp. There are many very good makers of high efficiency horn loaded speakers out there these days. Take a look at Cathedral speakers out of Virginai for an example of good sounding horns I have heard that can be had for very modest cost.

Electrostatic speakers are another good option to consider if that kind of thing might float your boat.

So basically, there are ways to make that amp work very well indeed with most anything if done right.

Hope that helps.
Elegal, ... Al, Ralph (Atmasphere) and I have been around the block on amp/speaker compatibility issues so many times, like the proverbial tiger who chased his tail and turned into butter, I feel like I'm about to turn into a stick of butter too.

As a threshold matter, let me say that Al's advice is spot on. Let me amplify what he said with a real experience. I've use ARC tube amps to drive my Paradigm 8 V3 speakers.

Although the S8s are pretty sensitive, 92dbs, they have impedance and phase angle curves that are so rocky they would make a mountain climber dizzy. To add insult to injury, the impedance curve in the bass through midrange spectrum is 4 ohms and the phase angle dips to a negative 60 degrees at one point. In short, the S8s were designed to be driven by a high current/high power SS amp. Ooopps.

Why the long tale? For some reason, my old amp, an ARC VS--115, was able to drive the S8s. Why? Here's my guess. The VS-115's rated power output is 120 wpc. Plus, its output impedance is "low'ish" for a tube amp. So the amp performed "SS-like" as a "constant'ish" voltage source.

But here's an interesting twist. I switched out my VS-115 for an ARC Ref 150. Now my speakers really sing. Why? Here's my guesses.

First, the Ref 150 has more head room by way of rated power than the VS-115: 150 wpc versus the VS 115's 120 wpc.

Second and possibly the most important. The capacitive power supply in the Ref 150 is 3 times larger than the VS-115: 1040 joules versus 334 joules, respectively. That's a lot. What this means in plain English is that when the Ref 150 is driving my S8s in the rocky road region, it can push some serious juice with its beefed up power supply.

Your take-aways.

(1) More power will not hurt, even with so called sensitive speakers. If in doubt, and your wallet can afford it, opt for more amp power. Even if a "marginally" powered amp seems ok, an amp that can handle the peaks and valleys of power demands, either relating to dynamic swings from the input source material or rough impedance and phase angle curves, I suspect your system with sound even better with more power.

(2) As Al said, first pick your speakers and then your amp. I was lucky because I did it half-arsed backwards.

(3) Read the many threads on A'gon which speak to speaker/amp electrical compatibility. Focus on Ralph's White Paper which discusses so called Voltage Paradigm versus Power Paradigm amps. Try to get your arms around the notion of how speaker impedance (which varies as a function of frequency response) can affect the sonic presentation if the speaker is driven by a tube amp with "high'ish" output impedance.

And, as I came to better understand, not all tube amps are "pure" Power Paradigm amp. If a tube amp uses NF, which as Al said will lower output impedance, the amp will perform "SS-like." Kinda like a hybrid.

(4) The use of excessive NF in either a tube or SS amp to achieve certain operating objectives (e.g., lower distortion, extended bandwidth, higher DF) does not come without sonic costs.

That's it.
I'm on board with Al/Atmasphere/Bifwynne and others regarding how impedance and phase angle are key factors to consider when choosing an amp to get best performance out of speakers.

Also that there are many shades of grey in between the extremes in regards to amp technology and design, and that as a result, it can be very hard to predict how good or not any particular combo really sounds, but it is not as hard to predict which combos have the best chances of working out optimally together from a technical perspective.

Also I believe that is is important for things to work out well from a technical perspective, however, that alone does not ensure enjoyment. Enjoyment is what it is all about in the end. Good technical execution can usually only help, but alone does not guarantee the desired outcome, which might be had many different ways.
You have received a lot of good advice from almarg and other which I would take to heart. Another way to look at thing is what amps do the vendors use to drive their speakers at demos and shows. The Sonus Faber Olympica series were in several rooms at RMAF and were all driven by solid state amplification...
I agree with the whole discussion of the difficulty of driving the original Cremona speakers and the problems of difficult phase angles. But, before reaching a lot more conclusions, I think it is important to understand if the speakers are original Cremona or Cremona M. They are quite different speakers.
Elegal, I am saying that they sound very much alike, in my experience. Which, you could argue supports Polk432's assertion that the Macs sound like SS (or, my SS amp sounds a lot like tubes !). My point, and I was not trying to beat up Polk432, and it was laced with a small measure of sarcasm, is that people talk about great differences between electronics but ultimately if they are well engineered they should not sound that different, aside from differences in power (power requirements of the associated speakers and room) and other inter-component electrical characteristics. My secondary point is that if components do sound very different from each other, then perhaps one or more of them is flawed in some way (from some reference), perhaps built for a specific purpose, compatibility, and/or sound, which if used outside of those parameters might sound horrendous.
Speakers sound a lot different from each other, however, in my experience. I would consider the room, then match the speaker, then match the amp, then the rest...
So, to be completely open kimono here, my experience that I refer to above is based on the following experiment. I would submit that this A/B test surpasses many in terms of relevance. That is, I speculate that many audiophiles compare memories of sounds of systems or components and in different rooms, dealerships, or other places. To be true, you have to minimize the variables and time between auditions down to minutes or seconds, NOT days or weeks. As an example, I read various audiogon members saying a certain CD player sounds better than another. I would place more trust in their assertions if they had both CD players attached to one preamp, simultaneously, with the same cables, with the same CD queued up and playing in time, to the same speakers, in the same room. I have done this experiment, many times, and I can tell you it is very hard to tell the difference. Otherwise, we are relying on memory, biases, and corrupted senses.
So, back to the discussion. I had my MC240 and C22 vintage equipment, which has been maintained, connected to a pair of B&W 804 diamond loudspeakers, source Oppo BDP95 from the RCA outputs. I had the same SACD/CD player connected simultaneously via the balanced outputs to a Bel Canto Pre2 preamp feeding an ARC 100.2 amplifier into the same speakers. To do the A/B, I would simply disconnect the banana plugs from one amp into the speakers to that of the other amp and play the same music from the CD player. Music from the CD player was in 15-30 second samples. So, the brain only had to remember sound from about 30 seconds ago, in the same room, with the same speakers, with only different electronics. Room was about 14x24x8 feet, perfect rectangle with only one open hallway (3 feet wide), system on the long wall, with basic treatment (curtains and no-name echo busters).
The differences were miniscule, with the only ones being mostly attributable to power - that is, at higher volumes the 100 w/ch amp could do better. Otherwise, both sounded very good and very similar. The only noticeable difference was that the ARC had better bass control over the B&W's than the MC240. The Bel Canto was also more transparent than the C22. The Mac combo vs the SS combo was just as good in the highs (treble).
So, this is but one example/experiment in terms of two different sets of electronics - obviously there are countless other components that one could purchase and do a similar experiment. The results I observed are but a small percentage of the possible outcomes.
Lastly, I would apologize for 'hijacking' this thread to get on the above soap box. But I think it is still relevant, in terms of when it is asked "can X amplifier power Y speakers", one notes that the room dimensions and characteristics of the components (efficiency of speakers, power of amplifier, etc,), type of music, and other associated audiophile pitfalls that I am trying to address here.
Jimmy, rather than composing what would be a lengthy and somewhat off topic response to your posts just above (with which I partially agree and partially disagree), I just want to make one point. Your test methodology was potentially harmful to the MC240, as it can be harmful to operate a tube amp having an output transformer without having a speaker (or, alternatively, a suitable load resistor) connected to it. Especially when a signal is being sent into the amp, as was the case here.

The reason is that "inductive kickback" occurs in that situation, which can result in damage to the output transformer and/or the output tubes. Google that term for more info.

-- Al
I owned both and I still say if you want good SS get a Mac275...
Al, I have a quick question about "kickback inductance." On rare occasion, I switch back and forth the hot speaker wire between the 4 and 8 ohm outputs taps. The time interval of a "no-load" condition is less than a second. When doing the switch, I mute my linestage to ensure a signal is not being sent to the amp. Could a short interval open circuit of that magnitude damage my amp?

The reason I don't turn the amp off before switching the taps around is because I am reluctant to subject the amp to frequent off and on recycling.
Hi Bruce,

I can't envision any way in which that might cause a problem. Inductive kickback occurs because the voltage across an inductance (in this case, inductance in the transformer) is proportional to the amount of inductance multiplied by the rate of change of current. A very abrupt change in the amount of current flowing through an inductance can result in a VERY large voltage spike, albeit a brief one, if the energy has nowhere to go. If that spike occurs in the transformer secondary, it can result in an even larger spike in the primary, due to multiplication by the turns ratio of the two windings. But without a signal being present, none of that would happen.

The one exception I can think of to that (which doesn't apply to your situation) might be if the amp were turned on or turned off without a load being present. In that situation an internally generated turn-on or turn-off transient might conceivably be large enough and fast enough to constitute a potentially damaging (or long-term reliability degrading) "signal." But even that would seem to be unlikely in most (but not all) cases. One situation I can envision in which it MIGHT be a problem is if the amp has a B+ relay which abruptly turns on plate voltages to the output tubes some seconds after turn-on. That would result in an abrupt change in the amount of DC current flowing in the transformer primary.

Best regards,
-- Al
Dear Al and company,

First, let me thank al of you for sharing your time, knowledge and insight with me. Now, let me explain how I arrived at this question. I was at a stereo store not even looking for speakers, and I heard the new Sonus Faber Olympica's and I was blown away. The best description I can give is "very warm." I felt like I was swimming in the music...I wanted to grab the first (decent looking) woman I saw and dance with her. I then listened to three other sets of speakers just to make sure it wasn't the effect of their listening room, and the others speakers did not come close to the SF Olympica's. I can't really afford the Olympica's right now, so I was hoping the Cremona M's would be close to the Olympica's.

Now, if I could say a few words about my listening. I love music, and listening to music is one of my favorite activities. However, I am not as concerned with the technical aspects of music reproduction as some are. What I mean is that I recognize that many people are fascinated by the never-ending technical pursuit of brilliant engineers who endeavor to design and created better equipment. And I have witnessed golden-eared experts listen to equipment, and they sometimes listen to music, critically, in a way that seems to prevent them from enjoying the music. Missing the for the forest for the trees. While that is important, I just want to hear the music, and I want it to sound good. For example, there used to be these "magic-eye" poster that initially looked like a bunch of dots, but if you relaxed a certain muscle in your eyes, an image would appear. I just want equipment good enough to allow the image to appear, in other words, for me to melt away into the music.
All this being said, I do believe good equipment makes a big difference in enjoyment. For example, when I upgraded to a clearaudio performance turntable, it was like switching from normal TV to HD. Everything sounded a lot better. And I remember when I went form my old Klipsch Heresy's to the Genesis G7's (which I no longer have), certain songs sounded completely different (and better). I.e. Copland's fanfare for the common man became so music more dramatic and powerful (and I actually liked it now). So I am far from a ludite regarding equipment. My only point is that the finer intricacies like phase angle drop off, etc.;-- the more technical aspects of a amp's or speaker's performance--might be very recognizable to guru's like Almarg, but might not be noticed by me.

Perhaps this will modify your speaker recommendations. Thanks again for everyone's help.
So it is Cremona M that you are considering. Much easier to drive than the original Cremona, which is what Al originally discussed.

Here is a thread with a guy who successfully used MC275 with Cremona M.

Cremona M with MC275
Thanks Al, I guess I won't be doing that anymore ! Elegal, regarding your last post, your description of what you are looking for is very well said, and coincidentally mirrors my own. I have only heard SF speakers in the stores (never at home), and they always sounded great. But also I would highly recommend you check out Harbeth SHL5 with your amplifier, as well, before you pull the trigger. Highly engaging, musically. Best of luck.
Thank you Jimmy615, and thank you Al, who has sent me on the new research task of trying to fully understand his answers...definitely the most informative answers I have received and very helpful.