Pass XA30.5 enough power for Wilson Sophia 2?

It will certainly work, but IMHO, way under powered for those speakers in a large room.

I have a very large room and I'm not going to tell anybody the dimensions! And certainly not in cubic feet. Nor am I going to state in decibels the SPL I normally listen at. Nope, I'm just not going to tell anybody that info.

Nickt...I suspect the XA30.5 will do fine driving the Sophia 2s. They are 88db sensitivity and 4ohm nominal rated speaker. The Sophia's do dip down to 3.26ohms at 220Hz but the phase angle is low at that frequency so that shouldn't be too hard to drive. Brian Damkroger of Stereophile reviewed the XA30.5s and drove Sophia 2s with them. The one thing he did point out is a slight lack of macro dynamics with this combo. So I don't think you will have a tough time driving the speakers but they will probably not get the last ounce of macro dynamics from the Sophia 2s, which are very dynamic speakers when properly powered. Here is the Stereophile review of the XA30.5: http://www.stereophile.com/solidpoweramps/pass_labs_xa305_power_amplifier/

My speakers are Focal Electra 1037BE. They are more efficient than Sophia at 93dB/W/m. I often turn up the music to +90dB in 15 x 20 room without any problem. The needle that indicates bias current rarely moves past 12 o'clock position.

Good one 61!

Ditto! Couldn't have said it better, 61!

I have a Pass Labs XA30.5 currently driving a pair of B&W 802Ds and it drives them OK. I could use a little more power but the 802Ds have a very steep impedance curve. However the midrange and highs are glorious and the bass is very deep and tight. It just not play as loud I would like at times. It can get a little loose on some passages. The Wilsons are much easier to drive than the 802Ds and the impedance curve is not near as steep. The XA 30.5 is the finest amp I have owned sonically speaking. I am barrowing the 802Ds until get my my Apogee Divas redone by Rich Murry at True Soundworks. I will be selling the XA30.5 and purchasing a set of Pass Labs XA100.5 monoblocks within the next month or two.

In many rooms and depending on typical listening levels I suspect it is enough power, but there will be times in some settings, with some music, when it might make you wish you had the XA-60s. When it comes to the Pass line, I would by the amp with the fewest watts that are sifficient, I just think the lower the wattage the better the sound, IF, it is enough to drive your speakers. The XA30s are borderline and I can understand it being a difficult decision which, unfortuantely, you can only find the answer by trying them in your home with the music and volume levels you enjpoy.

Pass may rate it at 30 wpc (its pure class A rating), but looking at Stereophiles measurements, it puts out 130 watts into 8 ohms and 195 into 4. It's transitioned to A/B but more important, it's not clipping. So on paper you might not think it's enough power but under the hood it's more than you think. Still might not be enough for "you", we don't know how much spl you like.

According to this list of specifications at the Wilson site the Sophia 2 has a sensitivity of 86db/W/m, rather than the 88 mentioned above. Based on the assumptions of 195W max amp power into its 4 ohm nominal impedance, a 4-meter (13 foot) listening distance, a 6db reduction in spl for each doubling of distance, and adding 3db to reflect the presence of 2 speakers, I calculate that maximum spl at the listening position will be 100db.

That is certainly good enough for most music at reasonable listening volumes. But ime it is roughly 5db too low to adequately handle music that has very wide dynamic range, such as a lot of classical symphonic music, if the recording is well engineered and minimally compressed.

Best regards,
-- Al

According to this list of specifications at the Wilson site the Sophia 2 has a sensitivity of 86db/W/m, rather than the 88 mentioned above.

Al...I got the 88dB sensitivity from John Atkinson's measurements of the Sophia 2 in the Stereophle review. Speaker manufacturer specs often are swayed by marketing considerations (although in this case, his measured sensitivity actually shows the speaker to be more sensitive than their stated specs), so I usually like to refer to measured performance in Stereophile, Hifi Critic, etc...Here is the link to Stereophile measurements section of the Sophia 2 review: http://www.stereophile.com/floorloudspeakers/619/index6.html.

Hello Al,

Wouldn't that be a 6 db gain when you add the presence of the second speaker as well as doubling the power when adding the other channel..

regards,

----------------------------

06-08-10: Almarg
According to this list of specifications at the Wilson site the Sophia 2 has a sensitivity of 86db/W/m, rather than the 88 mentioned above. Based on the assumptions of 195W max amp power into its 4 ohm nominal impedance, a 4-meter (13 foot) listening distance, a 6db reduction in spl for each doubling of distance, and adding 3db to reflect the presence of 2 speakers, I calculate that maximum spl at the listening position will be 100db.

That is certainly good enough for most music at reasonable listening volumes. But ime it is roughly 5db too low to adequately handle music that has very wide dynamic range, such as a lot of classical symphonic music, if the recording is well engineered and minimally compressed.

Best regards,
-- Al

CMalak -- Thanks. The Stereophile site appears to be down right now. Are you sure, though, that those measurements are for the Sophia 2 and not for the Sophia? I had looked for JA measurements of the Sophia 2 before I posted, but I was only able to find measurements for the Sophia.

Weseixas: Wouldn't that be a 6 db gain when you add the presence of the second speaker as well as doubling the power when adding the other channel

Doubling of power, whether acoustical or electrical, corresponds to a 3db increase. The fact that the additional 195W from the second channel of the amp is applied to a second speaker, as opposed to 390W being applied to a hypothetical single speaker, makes no difference for purposes of this calculation.

You might be thinking of doubling of a voltage, which would be a 6db increase.

Best regards,
-- Al

FWIW I'm driving a pair of Dynaudio Sapphires, a similiar but not exact technical match for Sophia, with this amp.

The room is not "large" but as others have posted, the amplifier has plenty of guts and should drive your Wilsons fine albeit not to paint peeling SPL.

I also drive the Sapphires with a pair of Bel Canto Ref1000M (1000WPC into 4 ohms) and at moderate SPL they provide no better bottom end control than the Pass XA30.5.

YMMV

Dealer disclaimer

Addendum to my previous post:

The Stereophile site is up again, and it looks like I was correct that JA's measurements were for the Sophia, and not the Sophia 2. Also, his 88.3db measurement was not based on 1 watt and 1 meter, it was based on 2.83 volts and 1 meter (2.83 volts corresponding to 1 watt into 8 ohms).

2.83 volts into the nominally 4 ohm speaker impedance corresponds to 2 watts. So the 88.3db sensitivity JA indicated for the Sophia would be only 85.3db based on 1 watt into its nominally 4 ohm impedance, fairly close to the Sophia 2's specified 86db/1W/1m.

And I note also that the Sophia's spec is indicated in the Stereophile review as being 89db/2.83V/1m, which corresponds to 86db/1W/1m for its 4 ohm impedance, which is the same as the spec for the Sophia 2 that I used in my earlier calculations.

Best regards,
-- Al

Al...I stand corrected. Thanks for clearing that up.

As Bill said, "the amplifier has plenty of guts and should drive your Wilsons fine albeit not to paint peeling SPL." That sounds right and good an answer as I think you can get without trying it in your room.

Expanding a bit on a point I mentioned earlier, the most important factor that determines how much power is required is the dynamic range of the music being listened to. Meaning the difference in volume between the loudest notes and the softest notes. Or perhaps more relevantly for some music, the difference in volume between the loudest notes and the average note.

It seems clear, based on several comments that have been made and on my calculations, that the amp should have no problem playing highly compressed, narrow dynamic range material, such as most rock recordings, at levels approaching 95db at the listening position. I doubt that any of us would want to listen that loud.

However, a symphonic work having wide dynamic range, if well recorded and minimally compressed, and if played with an average volume of say 70 to 75db, can be expected to at least occasionally have brief musical peaks that exceed the 100db maximum spl at the listening position that the amp/speaker combination is capable of.

Best regards,
-- Al

While the XA30.5 may convey a loud enough sound with your speakers, I would be apprehensive if you listen to complex music and if your room is large. Power and class A gives a sense of effortlessness, unrestrictedness, and control. Sure, the XA30.5 has some class AB headroom, but the amp is really about the class A portion up-front.

My opinion is the XA60.5 at a minimum, but the 100.5 or 160.5 may be even more appropriate. The Wilson/Pass combination is not uncommon, so you may call some dealers and check-out the systems page.

i agree wtih Rtn1---the whole point of this amp is Class A 30 watts. the A/B headroom is pointless imo

Why is the A/B headroom pointless if it keeps you from clipping in this small moments where you need the headroom? 99% of the time you'll be using 2-4 watts (Class A), no?

Pubul57 raises a good question. The XA30.5 is specified to "leave Class A at 60 peak watts." I'm not sure how that should be interpreted, as to whether the 60W is peak, rather than the usual rms definition, and as to whether or not that number applies to a 4 ohm load.

But if we make a very worst case assumption that it leaves Class A at 30 watts into 4 ohms, that is 8db less than 195W. Which means per my previous calculations that the amp would be operating Class A up to an spl of 92db at the listening position, which is quite loud.

-- Al

Al,
With regards to your latest post, indeed 92dB is quite loud. The staff on the Pass meter indicates bias not power output. It does not move until the amp begins to leave Class A.

I've pushed the XA30.5/Sapphires, with demanding source material, to fairly loud SPL and the staff doesn't move. Now, in all fairness it would be easy to make that baby jump but it would be too loud (at least to these ears) for an extended period.

Been there, done that.

Nickt, at this point, do you think the XA30.5 will do it for you? What are you thinking based on the comments you have heard so far?

I don't know about Nickt, but after reading this great discussion, _ I'm_ thinking about trying an XA30.5 with my Dunlavys. Thanks guys.

fwiw, using the xa60.5s on my WP6s in a room 15*11*8 (ie small), i am seldom able to get the meters to move (ie leaving class A), but it happens sometimes.

easy to play music 90db for extended sessions if distortion is low enough.

I have just switched from Pass XA100.5's to a Bat VK-600SE with my Sophia2's as the Pass\Wison combo didn't satisfy in terms of bass control (on the sloppy side with Pass).

I'd be leery of using a 30.5 unless I listened very quietly.

Madfloyd, how does the two (Pass vs. Bat) compare other than bass?

The Pass is warmer in the midbass and midrange and slightly smoother in the top end. It's a beautiful amp in almost every way, the only issue I had is it didn't have a firm grip on the woofers of the Sophia 2.

With the Bat, the bass is tighter and not as bloomy (or muddy), so the end result (at least in my room) is that the soundstage is more open, I hear more air, etc.

I am often surprised how bloomy (muddy?) acoustic bass sounds at live jazz venues (for that matter, how much more metallic trumpets sounds, and how much more dynamic drum kits sound....). The Pass versus BAT on the bass issue may be a matter of preference, not necessarily accuracy to the source. The Pass is definitely warmer, which proabably is why I like them, being a tube amp user.

Perhaps paired with some preamps and sources it might sound bloomy or muddy, but the Pass XA.5 series that I've heard and experienced definitely don't have these shortcomings.

Same experience as Tvad and Vinw with the XA.5s, but I use Merlin VSMs so I did not want to make to much of a cliam as it relates to deep bass. The XA30.5 (with the Aleph J not too far behind) is the best SS I have ever heard (still prefer tubes with speakers that are tube-friendly).

Pass and BAT are both great SS options. If Madfloyd changed only the amp, and hears what he hears, then it is hard to find fault.

I concur that in my system, the Pass provides phenomenal bass, at least when there is sufficient power. It is not a 'fast' bass, which I personally do not think is accurate. The Pass most definitely takes firm control of the woofers. It would be interesting to compare the BAT to the XA160.5, but there would be an obvious price differential against the Pass.

Tvad- then if he got the BAT and the bass issue was resolved, how was the muddy bass not from the amp? Just curious as I don't understand your comment---on your speakers in your room, things are obviously different. Perhaps he has a huge room, i don't know.

I've owned the speakers, but neither amp so was trying to refrain from comment. Personally, I've never liked Wilsons with SS, with rare exception. BAT 75SE was superb on my Sophia Is. So do VTL 450s.

I personally think the 30.5 will be dynamically challenged on that speaker. on the SS-side, I had a Bryston 4BSST and didn't think it was that powerful sounding on that speaker.

KeithR

I am not surprised by Madfloyd's observation, I own BAT tube amps and even their tube amps have stellar bass response. BAT solid state amps have more caps than most amps in the power supply as the designer believes in more storage energy the better theory.

I am more interested in the midrange and up comparison. I have only heard Pass X350.5 vs. Spectron Musician 2 and found Pass maybe overly warm in midrange, even more than some tube amps from my impression. Accurate or not, I can't comment and I am sure most prefer warm midrange than lean midrange. Also interested to hear if BAT reproduces the micro dynamic, inner detail/texture, depth, and other critical parameters (to a tube guy) as well or better than Pass.

Semi,
Those are all good questions. Could you start a different thread? This one is about Pass XA30.5 and Sophia 2 speakers. Thanks.

Reno Hifi has a home demo program on Pass Labs, and is a real asset for those looking to form their own opinion. I feel that the restock fee and terms are quite reasonable.

Always be aware that even used amps need a few days to warm-up when boxed. If you were to evaluate for a short time, I would suggest leaving the amps on the entire time.

Input impedance is low in the Pass XA.5 amps. That could be a factor.

A lot of (most perhaps) preamps have output impedance that is too high for the Pass.

A lot of (most perhaps) preamps have output impedance that is too high for the Pass.

Some tube preamps =may= be too high, but I'd be surprised if any solid state units are. I think your statement is a distortion.

That is quite a line-up of great preamps. I did once use the Audible Illusions 3A with the Aleph 3, which I think was 10kohm input impedance, and the AI3 was realtively high outut impedance, and I did not notice any problem driving the load. I would say that 95% of preamps should be OK with the Pass, it is an issue, but is not likely a problem with most, if not all, preamps - certainly not ideal for those seeking a passive path to preamplication.

My understanding is that a 600 ohms preamp impedance output (like the Ref 3) requires an amp with 60k input impedance.

Tvad is correct.

The point to using a ratio that approaches 100:1, or that is much larger than 10:1, would apply to the situation where the only output impedance specification that is available is a nominal rating, that presumably applies to mid-frequencies. In which case using a high ratio would allow for the rise in output impedance that commonly occurs at very low frequencies, especially in tube preamps, due to the output coupling capacitor.

In this case, worst case output impedance data for the Ref3 across the entire frequency range is available in JA's Stereophile measurements. The worst case, which as can be expected occurs at 20Hz, is 1437 ohms in balanced mode. That is well under one-tenth of the input impedance of the Pass .5 amps, and therefore should not be a problem.

Also, in situations where this issue may be a problem I would expect the symptom to be attenuation of the deepest bass, not muddy bass.

Regards,
-- Al

Can you match the Pass amp with a tube amp? Yes. And I highly recommend it. It will give you the best of both worlds.

Do I ever wish for a tube amp with this combination? Absolutely not.