Why is an XA30.5 a bad match for Revel Ultima Salon II speakers?


I actually own Revel M106 speakers right now, but some day, I intend to replace them with full range speakers like the Wilson Sophia II or Revel Salon II.

People say you need a lot of power to drive the Salons. The M106 and Salon II have almost the same sensitivity, and the XA30.5 can play the M106 louder than I prefer to listen (FYI I have a Velodyne powered sub). I guess my ears are pretty sensitive to loud volumes.

Does having all the mass of driving full range woofers into the 20hz range increase or complicate the workload on the amp significantly?

What is it about these speakers and many others that would demand a larger amp even at moderate volumes? My XA30.5 is supposed to be good for about 190W into 4 ohms, but nobody, including Pass Labs, seems to recommend an amp of that size for the Revel Salon II.

If I were to buy the Salons but had no amp budget, would I be better off trading for a more powerful but somewhat lesser quality amp than the XA30.5 such as a Parasound?
sboje
Hi sboje,
    I haven't heard these combinations, but overall, I can't imagine why your Pass would not drive either of these speakers.  The problem is that these speakers are both 4 ohm relatively low to medium sensitivity (86db) and both require an amp with very good current capabilities to drive them... that's the catch.... Most big amps have big power supplies which gives most of them the capability of the current needed to drive such speakers... but if I recall the XA30.5,  it is rated Class A to 30 watts,  but its actual power is more like 130 into 8 ohms and 190 into 4. I'm not saying that some big powered amps out there wouldn't be better, but  Unless you are a loud listener that drives em hard,
I suspect that it would drive them just fine.  I'm sure someone out there would give a more solid answer, but that's just 2 cents worth, Tim
After having a Parasound A21 amp and JC 2 BP preamp I suggest you keep the XA30.5. Once you have the Salon 2's you will know if it has enough power for your listening needs. If so, you saved some money. If not, keep the XA30.5 until you have the funds to get something of similar quality that has more power. Just my two cents!
good question! The specs for the XA30.5 are pretty good (not surprising since it's a Pass Labs product):

Description: Solid-state stereo power amplifier. Inputs: 1 pair unbalanced (RCA), 1 pair balanced (XLR). Outputs: 2 pairs binding posts. Rated power output: 30W into 8 ohms, 60W into 4 ohms (both 14.8dBW). Maximum output voltage: ±35V. Maximum output current: ±20A. Voltage gain: 26dB. Input sensitivity: 0.77V at 26dB gain. Frequency response: 1.5Hz–100kHz, –3dB at 1.5Hz, –2dB at 100kHz. Signal/noise: 150dB at full power. Distortion: 0.01% at 3W, 0.1% at 30W. Input impedance: 30k ohms balanced, 15k ohms unbalanced. Damping factor: 150 at 8 ohms. Slew rate: ±50V/µs. Power consumption: 238W.
Read more at http://www.stereophile.com/content/pass-labs-xa305-power-amplifier-specifications#pFvKLDoXoFb0JoE8.9...
with it's ability to output +/- 20A my calculations show that it should be able to double in power for each halving of the speaker load impedance (I expected nothing less from Pass who's been a major contributor to writing the book on how to make a class-A amp).

But, let's look at the Revel Ultima Salon II impedance & phase plots (Fig1 in the link below):
http://www.stereophile.com/content/revel-ultima-salon2-loudspeaker-measurements#fm6YgtoIdAOUp14u.97

IMO a tough impedance & phase plot - large swings in phase swinging from capacitive in the deep bass to inductive in the upper bass & lower midrange, rather low impedance (4 Ohms) in the bass. This is a hard speaker to drive for any amp. Definitely bring a high current amp to this party (which the XA30.5 seems to be).
The thing to remember is that with non-zero phase angles, the impedance is actually much lower than what is plotted. For example, at 50Hz, the phase angle is approx -20 degrees. My calculations show that the resistive part of the speaker impedance (which is the part used by the amp to create a voltage to drive the speaker cone) is actually 3.57 Ohms (not 3.8 Ohms as plotted in Fig 1). Having a reactive component to the speaker impedance exacerbates speaker impedance i.e. makes a low impedance appear lower to the amp. Thus, the amp struggles more as it has to dump current into a (further) lower impedance.
For a moment forget the brand & model of your power amp.
A 30W power amp (no matter which brand) can output 1.9A into 8 Ohms.
A 60W power amp can output 3.8A into 4 Ohms
A 120W power amp can output 7.75A into 2 Ohms.
All of the above ASSUMING the output voltage does not violate the max output voltage capability of the amp + the AC power xformer is capable of delivering this sort of current.

Next, how much power do you need to generate the SPL at your listening position?
Assume you listen at 3m (10') from the speakers.
The Ultima Salon II is 86dB/2.83V/1m from the Stereophile review.
Thus at 3m the SPL would be 86dB - 6dB - 3dB = 77dB. This includes the detrimental effects of sound absorption due to walls, furniture, drapes, etc + the positive effects of having stereo playback. Essentially these 2 effects wash out.
So, 1W gives you 77dB SPL at your 10' away listening position
10W will give you 87dB SPL at 10'
100W will give you 97dB SPL at 10'
200W will give you 100dB SPL at 10'
400W will give you 103dB SPL at 10'

103dB SPL for transients is not very loud - it's decent tho' but on the lower side. If you want your listening experience to be realistic & you want to get the feeling that the music flows effortlessly, you are going to need atleast 400W of power.
With the Ultima Salon II having an impedance in the 3 Ohms range your XA30.5 is going to operate like a 70-80W power amp. If you reference this to the above SPL table you'll see that you'll get an approx 97dB SPL max out of it. This is not going to be very loud nor realistic. It's going to feel that the amp is reigned in & that the music doesn't have that sparkle or that effortless flow.
For this speaker if one wants realistic levels of SPL for the transients then power begins to increase rapidly, as you can see. 
That's why the XA30.5 is not a suitable amp for the Revel Ultima Salon II speakers.
Hope this helps. FWIW.




Thanks for the lengthy reponse Bombaywalla!

Most of my daytime listening is around 80db to 85db according to my ratshack meter's C weighted average mode. I really have no idea what the true peaks would be. I think most music I listen to wouldn't have anything too extreme. Listening to the 1812 overture is a compromise though... I like to turn that up so that I can hear the quiet passages, but my amp is running out of steam for the canon shots.

Having realistic playback levels sounds like a worthy goal, but to give you an idea about my hearing sensitivity, I often wear musician earplugs to play my grand piano because it's too loud for me.

I feel like my system is most coherent and enjoyable at the 80ish db level. Brass and other instruments are really vibrant, and even startling at low volumes.  I'm not sure if that's primarily because the amp has an abundance of headroom at this level,  because the room gets overloaded with slap echo and wall vibration at higher volume, because humans have a different hearing response curve at different volumes, or if it's a combination of all three or other factors. I'm really pleased that my system sounds very dynamic to me even at 70db, and my fiance probably appreciates that at 2am even more than me.

Do you think the dynamics would take a turn for the worse at 80db in comparison to my current M106 speakers?

Is it harder for an amp to send a 25hz signal to a small speaker like the M106 that can't reproduce that, or a speaker that can? Does the crossover actually trim that out of the small speaker and make it easier?

here is a link to the imp & phase plots for your Revel M106 stand mounts:
http://www.stereophile.com/content/revel-performa3-m106-loudspeaker-measurements#ljf3ojqamBz1KzED.97

tough imp & phase plots once again...
And, here is a synopsis of its specs:

http://www.stereophile.com/content/revel-performa3-m106-loudspeaker-specifications#usPtaevBJxpkUyqE.97

with a -3dB at 59Hz, it's easy to see why the 1812 Overture canons are lacking. Your stand mounts just don't have the capacity to reproduce such a low freq. When we say -3dB at 59Hz the SPL/volume is half (-3dB) at 59Hz. The SPL is probably back to 100% at a much higher frequency such as 90-100Hz. So, essentially, you have very bass coming from your M106 speakers & I think you wrote that you use a Velodyne sub - I can see why. 
The XA30.5 "sees" the x-over of the M106 & this x-over is providing a high impedance to the bass frequencies so the XA30.5 is probably sending very little power to those low frequencies. IOW the XA30.5 is probably not taxed much at these low freq due to the M106 design.

For the Ultima Salon II speaker, it's a different ball-game. The -3dB freq is 23Hz & 23Hz is in the deep bass region (unlike the M106). Now the XA30.5 will "see" the Ultima Salon II x-over & this x-over will demand lots of power into these low bass frequencies. I expect the XA30.5 to run much hotter temp wise as it tries to deliver power into these low frequencies & the XA30.5 will get taxed much more than it ever was with the M106.
So, yes, I expect the dynamics to worsen at 80dB SPL with the Ultima Salon II.

One more thing to remember (that many forget) - even if the Ultima Salon II are 23Hz capable, does not mean you will be able to reproduce 23Hz in your room. Based on your room dimensions you will be able to support a certain min frequency.
Here is a room modes calculator that will show you what the min freq your room can support:
http://amroc.andymel.eu/?l=19&w=17&h=9&ft=true&r60=0.6  
 
So in simplest terms, I can think of the impedance curve as an inverse current requirement curve? I can see that the Salon II would take a LOT more juice all the way from 600hz on down, and even more so below 50hz. I can definitely see how any music with significant content in the bass region would demand a lot more from the amp with full range speakers like the Salons.

It looks like even the "friendlier" Wilson Sophia 2 would be a significant increase in workload.

Thanks for helping me understand that!

So in simplest terms, I can think of the impedance curve as an inverse current requirement curve?
yes, in the simplest terms that is correct.

Thanks for helping me understand that!
welcome! glad I could help.
Thanks for the link, it was a nifty tool for discovering I needed to tighten up an air conditioning duct cover when my Salon 2s made it buzz at 20.1 Hz!
Get Pass 350.8 350ch plenty of power.

Had the studio 2.  You need more power.  Revel sounds great but with more power.   They sound better. 
Thanks for the link, it was a nifty tool for discovering I needed to tighten up an air conditioning duct cover when my Salon 2s made it buzz at 20.1 Hz!
welcome! good to read it was useful....
Bombaywalla,

How do you think my ARC Ref 150 SE tube amp would fare with the Ultima Salons?

My amp has 4, 8 and 16 ohm output taps.  I surmise that the 4 ohm taps would work best with the Salons given its lowish impedance in the low frequencies.  I seem to recall that the output impedance off the 4 ohm taps is about a half an ohm.  Rated power off the 4 ohm tap is well north of 150 watts if driving a 4 ohm load.

Reason for question:  I've had Salons on my radar screen for a while.
@bifwynne 
Depends how loud you like to listen. Tubes are fantastic from top to bottom until you want max spl. As you hit the upper limit of tubes the highs and mids will increase in loudness but the lows will peter out and stay consistent. That said if your normal listening level is in the upper 80/low 90db the ARC should be fine. 95db peaks should be fine but once you push 100/100+ db the lows peter out IMO.
Bombaywalla,

How do you think my ARC Ref 150 SE tube amp would fare with the Ultima Salons?

My amp has 4, 8 and 16 ohm output taps. I surmise that the 4 ohm taps would work best with the Salons given its lowish impedance in the low frequencies. I seem to recall that the output impedance off the 4 ohm taps is about a half an ohm. Rated power off the 4 ohm tap is well north of 150 watts if driving a 4 ohm load.

Reason for question: I’ve had Salons on my radar screen for a while.
Bifwynne,
good to see you are still lurking around these forums - haven’t heard much from you since you installed DEQX in your system.... :-)

well, we have discussed your ARC 150W/ch amp many times in these forums. I remember that it has a pretty stiff power supply (I seem to remember 1000+ Joules) & being a tube amp it’s going to maintain its output wattage more or less.
What does "Rated power off the 4 ohm tap is well north of 150 watts if driving a 4 ohm load" mean? Is it 200W/ch into 4 Ohms?
I believe it will be much better than the XA30.5 driving the Salons as you will have atleast 2X the output wattage.....
.....but, man, I think you’ll need an even bigger amp to make the Salons sing. I’m thinking atleast 300W/ch (which is going to get expensive!).
You’ll get average sonics from your 150W/ch & like xti16 wrote it depends on how hard you want to drive the Salons. If you settle for less & drive it to lower average SPLs then you should be good but it you want more realistic listening levels, i think you’ll find that you will want a bigger amp.
I once had a speaker that could handle 105dB SPL peaks & it was really very good sonically but on rock & blues there were times I wished it could hit higher peaks.
You might be different - you might be happy with lower peak SPL???

I’ve a friend who has the original Salon speakers & drives it with a Gamut 200W/ch s.s. mono-block amp to a really, really, really good effect. He has a smaller room & they way that speaker pressurizes that room in the bass region is simply a treat. I’ve never heard anything like that in a long time....
Now the s.s. amps of that caliber are different - their output power jumps atleast 50% into lower impedances so I bet that he has something like 300W/ch or slightly more into 4 Ohms (which is where i was going with this in the sentences above).
Hope this helps. FWIW.
Thanks XTI16 and Bombaywalla.  Kinda' figured you would come out where you did.  It makes sense.  

No Bombaywalla, ... the amp does not double down wattage at 4 ohms.  In fact, if you checked out some reviews of the Ref 150 (not SE), you will see that the amp puts out between 150 and 165 watts if the amp is hooked up to a speaker load that matches the nominal tap value.  IOW, the amp will deliver between 150 and 165 watts if it is driving a 4 ohm nominal speaker load off the 4 ohm taps; an 8 ohm nominal speaker load off the 8 ohm taps, and so forth.  

It's really a function of how the amp is configured.  Although its output impedance is "low'ish" for a tube amp, it does not produce power like a SS "Voltage Paradigm" amp.  

I still own Paradigm S8s (v3), which are pretty decent over-performing speakers.  The rated sensitivity of the S8s is 92 db, which is considerably north of the Salons.  Hence, I can cleanly drive the S8s to ear splitting levels. 

BombaywaIla, I get the practical electrical realities you explained above.  I surmise you would respond similarly if I asked your opinion about matching up the Ref 150 to the Magnepan 3.7s, which I recall have a sensitivity in the mid-80s as well.

My bottom line is that I like my current electronic set up, ... all ARC.  And I am inclined to keep the amp.  Hence, I surmise that if I was interested in switching out my speakers, I would be well advised to consider speakers that have rated sonic sensitivities closer to my S8s than the Salons or Maggies, i.e., go high 80s or low 90s.

Thanks.

Bruce

P.S. -- My DEQX is off-line.  Although it adds a lot and mitigates a lot of room problems, in the end, I'd rather suffer the time delays caused by the high order crossovers than the artifact effects of adding an electronic device to the signal path.  I'm kinda' inclined to swap out my Ref 5 SE for the new ARC Ref 6, which is attracting rave comments. Hard to believe that the ARC electronics can be that good, but hearing will be believing.  

bifwynne,

thanks for the feedback re. your amp - 150W-165W/ch if the speaker is connected to the correct tap.

Magneplanars are planar (mix of ribbon & planar) speakers which tend to have (really) low impedances much like some of the extreme cone-driver speakers (think B&W). In such cases we are back to using high-current, high wattage s.s. amps. Or, in many other cases I’ve seen people using high-wattage class-D amps successfully. Unfortunately for these sort of lower sensitivity speakers with lower impedances & tough phase angles that’s the solution that works best.
In the end one can hook-up any speaker to any amp & you will get music but you wont be getting the best out of that particular speaker you paid handsomely for & it will keep you longing for more. What’s the point?

I know you really like your all-ARC system but ARC does make bigger i.e. higher wattage amps. What about spending the money on the next level up power amp rather than the latest preamp. A bigger amp will open your doors to many other speakers that are on your list but you can’t get because they might be substandard sonically due to your present amp’s output wattage.

Or, find another speaker with a more benign impedance & phase plot that will be in the sweet-spot of your present amp. I’m sure such a speaker exists....

So, the DEQX is sidelined due your philosophy of minimizing the signal chain? nothing wrong with DEQX - just that you are a minimalist w.r.t. audio gear, right?

[good thing you didn't spend anymore on it.... ;-)]

@bombaywalla , you wrote " [s]o, the DEQX is sidelined due your philosophy of minimizing the signal chain? nothing wrong with DEQX - just that you are a minimalist w.r.t. audio gear, right?"  

Yes, ... correct.  The DEQX solves many problems. That said, in my case, and IMO, ARC gear is very synergistic when used with other ARC components.  IOW, the whole is greater than the sum of the parts, ... if I got that right.  The DEQX detracts from the considerable ARC component synergistic effect, ... IMO.  

Btw, I checked the specs on the Revel Studio II.  Unlike its bigger brother, its sensitivity is close to 89 db.  See here: http://www.stereophile.com/content/revel-ultima-studio2-loudspeaker-measurements#xX3PQVeOHrCwDxHS.97

Notably, I used to own Paradigm S8s (version 2) which also had a rated sensitivity of 89 db.  My amp drove the S8s (version 2) to ear splitting levels.  And btw, the S8s (v2 and v3) have pretty wicked capacitive phase angles and low impedance plots in the bass region.  

Perhaps, I could get a similar loudness result with the Studios???  More importantly, I wonder if the Studios even sound better than my S8s.  So much hype and brand snobbery in our hobby.  Also, the Studios tip the scales at 140 pounds each.  The S8s are a slimmer 100 pounds each. Ouch!

You also suggested getting the next ARC amp model up the food chain. That would be the Ref 250 SE.  Too expensive; too much heat; not enough space.  

Thanks again.
I had Revel Studio 2s, and originally drove them in a fairly large room
with a ARC VSI60 and on most material, it sounded fine......but
when dynamics showed themselves, it ran out of gas quickly.......
so I can emphatically say 60 watts of tubes aren't enough into that
4ohm load, with mediocre efficiency......I then went to Pass X350.5
and never had an issue..........but I eventually swapped the Studios
for Magnepan 3.7s, which are also 4 ohm with mediocre efficiency,
and they wanted even more than the X350.5, so I went to Bryston 7BSST2s with great results 900W into 4ohm......I now still have those speakers with Bryston 28BSST2's, nearly 2KW into 4 ohm and the Maggies just sing........I would never consider Revel again against these speakers, but I liked them while I had them........
Stewart,what do you do for bass?

I have Revel Ultima Studios and the more quality power I feed into them the better they sound. So I imagine it would be even more so for the Salon's

I'm using Vincent SP998 Mono Blocks and they sound sublime.  300W into 8 ohms, 50W Class A. 600W into 4 ohms. They have the best grip on bass I have ever heard. Beautifuly musical sounding they make the Revel's come alive. They just cruise effortlessly. You would have to spend truckloads more to get this performance.


thanks stewart0722, initforthemusic - you guys just consolidated the point I was making. 
My amp drove the S8s (version 2) to ear splitting levels.
thanks again for the feedback bifwynne.
As you well know it’s the not ear-splitting levels we are trying to achieve. You could get that with a lesser amp too than your present ARC. What we want is loud without distortion - as you turn up the volume it should get louder but not distort. This is much harder to achieve than perceived....
sorry to read that the ARC 250W/ch is not in your cards....
seriously - you should look for a time-coherent speaker. Your quest for another speaker will end. Don’t waste your time with these wicked phase angle, crazy impedance curve speakers. They’ll leave you wanting for better sonics....FWIW.
My bass desires are very well served by the 3.7s alone.........

It's a matter of placement......I go a little closer to the side walls and
about 18" from the front wall and the room is loaded very nicely
in the mid 30s hz range......

If I want more bass, I just need 20.7s.  Subwoofers do NOT integrate
with Magnepans, people just say they do to make themselves feel better about going down that road......I don't think that even Magnepan's own bass panels really integrate that well with the 3.7s at least by my standards....., that's based on me trying two of them I bought for an office system.......

Having said that, if you compared 3.7s with the Magnepan's of old in the lower regions, all of your concerns instantly disappear.......


@bombaywalla , you said I "should look for a time-coherent speaker. [My] quest for another speaker will end. Don’t waste [my] time with these wicked phase angle, crazy impedance curve speakers. They’ll leave [me] wanting for better sonics....FWIW."

Gotcha.  I am aware of only 3 speaker brands that are purportedly time coherent; namely:  Vandies; Green Mountain Audio; and Thiels.  Am I missing something?   What brand did you have in mind? 
@bombaywalla , your calculations make perfect sense. I was just wondering if there will be any improvement if the OP uses 2 x XA30.5 in a biamp configuration ? I am not talking about bridging the amps to use as monoblocks but actually using proper biamping, whats your take ? Will the amps perform better, with more headroom ?
Gotcha. I am aware of only 3 speaker brands that are purportedly time coherent; namely: Vandies; Green Mountain Audio; and Thiels. Am I missing something? What brand did you have in mind?
you're right - the 3 you cited are time-coherent.
additionally, older Quads, Sanders Sound Systems ESL Model 10 & Model  11, some older Martin Logans such as the CLX or CLZ or CLS (I'm forgetting the exact model number), Eminent Technology LFT-8 (I think this is the model number), Tannoy DMT xxx Mk2 series (I've the DMT10 Mk2 which is a flat 8 Ohms across the entire audio band & is being driven aplomb by my 1977 vintage Yamaha integrated amp. They don't have great WAF but they sound fantastic). 

@bombaywalla , your calculations make perfect sense. I was just wondering if there will be any improvement if the OP uses 2 x XA30.5 in a biamp configuration ? I am not talking about bridging the amps to use as monoblocks but actually using proper biamping, whats your take ? Will the amps perform better, with more headroom ?
Hi Pani,
nah, biamping will still not do it for him. It does relieve the stress on the amp in that instead of 1 amp providing bass to 2 speakers, 1 amp provides bass to 1 speaker only. 
But, this is a class-A amp - it always runs 100% bias & it's well-known that class-A amps have zero headroom. That's just the physics of class-A topology. 
His XA30.5 will still be a 70-80W/ch into the low impedance with a little more current. It will still limit the peak SPLs. It will surely give him music but not what the Ultima Salon 2's are capable of....
For what it's worth, I have the Salon In and the Parasound A31 with an integra dtr50.7 receiver.  The system is beautiful and would not change a thing.
I own the Revel Salon 2s and drive them with an Ayre V5xe amp. The amp is rated at 150 into 8ohms (300 into 4ohms). The Salons are rated with a nominal impedance of 6ohms. The nominal impedance doesn't tell you much - especially if (like me) you listen to lots of music with a wide dynamic range such as classical or jazz. With classical or jazz played from an Aurender source, I can turn the volume control on my Ayre preamp up to about 35 to 40 out of 60 gradations before I get blown out of my big living/dining room with 9’8" ceilings. At those relatively uncomfortable volumes there is zero distortions that I can detect. With rock, those volumes become quite uncomfortable - Sympathy For the Devil or The Immigrants Song at 25 is incredibly loud.i have never triggered the protection circuitry.