Underpowered?


Hi guys.  Newbie here asking for advice. 

I recently purchased a pair of B&W 702 Signature (8Ω, 30-300W, 90 dB) to replace my old faithful 683s (8Ω, 20-200W, 90 dB).  I am running them with a McIntosh MA252 (100W into 8Ω, 160W into 4Ω).  I purchased them thinking they would complete my end-game system.  However, my excitement turned into disappointment when I realized the lows were somewhat lacking.  For all their faults, the 683s had a great dynamic low kick (no sub) that I was looking to take one step further.  Unsurprisingly, the highs and mids on the 702s were indeed more detailed and separation was clearer, but I couldn't get over the uninspiring lows.  I found myself listening at higher volumes chasing for that bass oomph.  Neither playing with the EQ at the source nor the amp was satisfactory.  So, I did the research that perhaps I should've done before purchasing the 702s and found out they are quite power hungry despite the specs being similar to the 683s.  I emailed B&W and McIntosh and they agreed the amp is probably underpowered for the 702s.  B&W described the sound of an underpowered speaker as one lacking low response and details, which is spot on. McIntosh suggested the MA352 (200W into 8Ω, 320W into 4Ω).

Of note, I love the MA252 and really wish there was a way to make this work.  I don't need a DAC/streamer/etc so I'm happy to put all my money on better sound vs tech features.  But I also think the speakers sound amazing even when somewhat underpowered and I'm considering upgrading to a MA352, Michi X3, Hegel 390.  Another option could be to get a sub? But I feel that would defeat the purpose of having a 3way standing speaker and then I might as well get a pair of bookshelf speakers (805 D4s, LS50 metas?).

So what do you guys think? Is it normal for a speaker that's rated 30-300W to be underpowered with a 100W amp?? What would you do:

  1. Sell the 702s and look for a better match for my MA252?

  2. Upgrade the MA252 (MA352? Michi X3? NAD 33?)?

  3. Get a subwoofer?

I would really appreciate your thoughts/advice!

dridel

So I've been listening for a couple of days now, during running in.  I spent a lot of time prior to the 702's arriving listening to the 683's.  It may seem an obvious statement, however they are very different sounding speakers - the 702's are tighter, more precise and brighter, but they aren't yet as engaging as the 683's. 

But, as they loosen up they reveal more of the bowers sound.  In the same position as the 683 (cabinets exactly the same size), they give plenty of bass - but it is a lot tighter.  Rage against the machine's "wake up" sounds immense, but 'flash' by queen sounds light in the build up.  "Star 6 & 7 8 9" iby the orb is a reference track for me and it really shows the difference between the two floorstanders. 

Ultimately, as I expected, the speakers are showing the amp up.  On the bench the kandy is 137w @ 8 ohms and happy with driving at 4 ohms, but the speakers just deserve something a bit better, which I think will balance the sound too. I will line up some auditions for the michi Integrated amps.  I might have a play biamping with an heirloom. A&R SA200 power amp. 

 

The arrive on Friday (anticipation / post hi-fi buyers guilt).  Will update, but already looking at michi x3 / x5 upgrade... 

@mattuk How did your amp do with the 702s2? I'm still enjoying my setup. FWIW I ended up getting the S5SHO and it was worth it.

Old thread, I know.  But of interest to me as I've just paid for a pair of 702 s2 as an upgrade to my 683's.  I also love their sound and at £1900 for a pair of new (open box) s2's it felt too good an opportunity to miss.

 

I've bought them blind (I know, first time I haven't auditioned a piece of hifi kit) and it's part of a longer term upgrade. I've got 125w at 8 ohms / 200w at 4 ohms on my Roksan Integrated amp.

 

We'll see how it plays out, but I'm thinking of a power amp in future anyhow. 

I do not think an amp change will give you the bass you seem to desire. An amp can provide changes but not dramatic. I doubt the room will be enough either.

I hope you have tried a sub or two instead, far better bang for the buck if you want to keep those speakers. (And turning them up loud to get bass at the expense of a piercing treble doesn't count as success; like you do understand).

As folks have pointed out it's in their design and measurements, so don't worry, add a sub or two (or four/dba) and enjoy!

agree, hegels are superb, in an absolute sense, and also for the value they represent

(no affiliation, just a happy and impressed customer/owner many times over)

Interesting thread, and seems this was resolved, but wanted to pop in because Hegel was mentioned earlier in connection with these speakers and wanted to add:

 

B&W 702 Signature is absolutely glorious powered by Hegel H20 200w amplifier. I've heard Hegel/B&W quite a few times and I think I'd stick with Hegel over McIntosh for B&W's for sure, especially for that iron low end control.

B& W is now owned a firm that knows nothing about audio or cares to .

Fews years will be another , true of all almost old name stuff .

@dridel 

I still don't understand why B&W would risk making customers (and reviewers) unhappy by rating these speakers at 8Ω / 30-300W. But what do I know...?

Because B&W cannot account for absolute pairings, given the diversity of the amplifier universe, vintage through cutting edge Class D, nor usage situations, nor user preferences.

The question to ask yourself is: are you really in a position to come to a conclusion and a "morals of a story" statement after trying a single amp that works for you?

Just to be clear, the above is meant to be helpful [read not critical]. 

Again, I'm glad and happy you've found a solution that works for you. At the end of the day, that's all that matters.

 

You guys are right and my conclusion was oversimplified and impossible to generalize. So let me try again:

Moral of the story: never dismiss a pair of speakers before feeding them at least half of their rated maximum wattage!

Also: "Details matter" - @jjss49 (and thanks for explaining why!)

I still don't understand why B&W would risk making customers (and reviewers) unhappy by rating these speakers at 8Ω / 30-300W. But what do I know...?

A few more thoughts about the MA352:
- The headphone amp is noticeably better than MA252's.  I looked into it and the MA352 has something called "Headphone Crossfeed Director (HXD®)" that the MA252 apparently doesn't.  What a nice, unexpected surprise!
- I dig the default EQ both at low and high volumes.  No urgent need to play with the 5-band EQ but it's nice to have it.
- I am happy to find that even low kbps tracks sound better.
- I know its looks are controversial, but I think it's one of the best-looking amps out there.  Yes, I even dig the fake green tube LEDs. I just wish it had the blue OLED display of the MA252 instead of the very 90s-y green one (why doesn't it??).
- I know there are better amps/speakers out there, but I'm so happy with this pair as a starting place to build upon. Maybe a DAC upgrade is next?
- I am curious to hear how much of a difference the REL S5/SHO will make in my setup, because honestly, I listen to it right now and I ask myself how much better can it get?? 

Daniel

 I learned than an amp wattage is not just how loud it can get, but that it affects the quality of the sound even at lower volumes when output wattage is waaaay below the max.

The measurement guys don't believe this but it's true.

Here is a review that answers your questions. 
 

No speaker of the 702 Signature’s size is truly a full-range speaker. It’s not physically possible. Only adding a quality, well-calibrated subwoofer or two can achieve the lowest frequencies from movies and music. But for those who can only use a stereo pair of loudspeakers due to limited space or other reasons, the 702 Signature delivers more emotion and bass impact from movies than most speakers its size. I heard decent bass energy from the 702 Signatures down into the mid-thirty hertz range, so they should be able to deliver the lowest notes of ninety-eight percent of music accurately. Unless you’re heavily into pipe organ or dubstep, these speakers are more than capable.

Although people swear by McIntosh and the  b&w pairing I think McIntosh is the wrong amp for those speakers...Having owned the 402 and 452,I'm not a fan of your amp or speakers to be honest..If keeping the speakers I'd find an amp with speed and balls..if keeping the amp I'd also find speakers with speed,accuracy and balls..if that makes sense..just my opinion

Moral of the story: make sure your amp has AT LEAST HALF of your speaker’s maximum rated wattage!

i would say this is not a general truism... the central issue here, in this case, is the nominal impedance rating given by b&w (no doubt by their marketing department...) is b-s...

see the test results of the b&w 702s2 as measured by john atkinson at stereophile...

I used DRA Labs’ MLSSA system and a calibrated DPA 4006 microphone to measure 7the Bowers & Wilkins 702 S2’s frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. My estimate of the B&W’s sensitivity was a high 90.2dB(B)/2.83V/m, confirming the specified 90dB. The 702 S2’s nominal impedance is specified as 8 ohms, with a minimum value of 3.1 ohms. My measurement of the impedance magnitude (fig.1, solid trace) reveals that while the impedance does lie at and above 8 ohms in the low treble and in two regions in the bass, it actually drops below 6 ohms through much the audioband, with a minimum value of 3 ohms in the upper bass. There is also a current-hungry combination of 4 ohms and a –48° electrical phase angle at 88Hz. Although technically this is an 8 ohm design, I think it should be used with amplifiers that are comfortable with 4 ohm loads.

this is why the smaller mac amp had so much trouble with the speaker in the bass region, when you see a solid state amp unable to double 8 ohm rated power into a 4 ohm load, it shows the amp has shortcuts inside, limits current capability into low impedance reactive loads ... so details matter, specifics matter... generalities are meaningless

@mozartfan ...*friendly back pat*  No, no, no....

If you intended to or not, to hijack a forum one needs either a subtle yet devious approach,,,;)

Otherwise, one's left with just the 'in your face kamikaze dog waste paintball splatter'.

Crude, yes.  Might get jerked off the forum by the Brain Police.
They email a nice note to 'not do that '.
They deserve that....having to actually 'police' all the forums fomented by all of us has to have some form of retaliation.

Class dismissed.  Be sure to scan Chapter 6.66, the 'Trollish Entertainment? Or Sociopathic Pseudo-Ironic 'Civility'.

There always a pop-quiz....everyday....😏

Probably has more to do with the impedance than anything. 
 

I use a power conditioner. The only thing it helps is my JL subs… because they are junk and super noisy with what appears to be zero AC filtering. Everything else it did not help or made it worse. Just have to play with it. 

Hmm... I must be highly immoral. The 3 watts of my amps are (at max power) 7.5% of maximum recommended power (40 watts), for my speakers. Or 15% of half power (20 watts).

Moral of the story: make sure your amp has AT LEAST HALF of your speaker’s maximum rated wattage!

 

Your story. Your morals. : )

Happy you’ve found a pairing to your liking and are enjoying it!!!

After a long weekend enjoying my dealer's MA 352, I went to return it today.  I also asked them to check my MA252 for problems, since many people here felt it should be able to drive the 702s. They confirmed the issue is just that the 702s need more power.  I wanted to audition the Michi X3, but they didn't have one in stock and they were very confident the MA352 is the superior amp.  So, I pulled the trigger and took the MA352 home.  I also bought a Panamax MR4300 even though I'm not 100% sure how much effect the power conditioner had on my setup.

The MA352 + 702 Signatures combo gets me very close to the best setups I have heard at dealers for much less money and before even playing with speaker positioning and room treatment. Let alone upgrading my DAC, cables, etc. I know I shouldn't say this, but I really think this is it for me.

Moral of the story: make sure your amp has AT LEAST HALF of your speaker's maximum rated wattage!

So I am powering the B&W 702 Signatures with a 20 year old McIntosh MC 202 (200 watt) solid state amp with a MC C41 solid state pre-amp and the B&W's just come alive every time I power them up.  The sound stage and clarity are stunning when fed a good recording. I'm glad you resolved your issues.  IMHO, McIntosh power is well suited to running the B&W 702 Signatures. 

Your speakers may still need some more time to break in and the woofers to open up, but in my opinion, it’s the MA252. I’m a McIntosh fan, but I am not a fan of the MA252 or MA352 tube integrated amps. They are direct coupled amps and do not use the McIntosh autoformers. I say this as a previous MA352 owner: the bass is sloppy, the mids shouty, the highs brash. I honestly don’t think you’d get the sound you want moving from the 252 to the 352. If you want to stick with McIntosh and an integrated amp (vs separates) consider a Mac SS integrated that uses autoformers. It’s a noticeable difference.

 

EDIT: Just saw your update re: the 352.  Glad you're happy with it.  I would still suggest, if you have the option and a willing dealer, borrow one of their SS Mac amps with autoformers to try and see if you hear a difference.  Use your MA352 as the pre so you're keeping everything else the same and just comparing the sound of the 352's direct coupled amp with an autoformer amp.

Does that MS252 have a variety of transformer tap impedance posts?
And was it using the 8 ohm tap?

      Just to be clear, The McIntosh MA252 amp is solid state with a tube preamp.

My first post. I pretty much had the same problem you have. A few months back I decided surround sound isn’t making it with me with stereo recordings. So pulled out my vintage 1985 Kenwood Basic M1 power amp and Kenwood Bacis C1 Preamp. I also kept my Klipsch KG4’s. Due to some of my hearing loss I use a Yamaha equalizer to suit my lost frequency in hearing. The KG4’s have good highs and pretty good lows. But missing a lot of mid range. My fix was to add another  M1 power amp and bi-amp to a pair of Klipsch RB3 bookshelf speakers. For me it made the the mid range much better. I also added two 12” subs to finish off the bass I also needed. For now I am done.

 

Vandersteen 2CE Signature III:

Recommended Amplification

40-160 Watts Into 8 Ohms

Frequency Response

29Hz – 29kHz +/- 3dB

32Hz - 21kHz +/-1.5dB

Sensitivity

86 dB, 1 meter with 2.83 volt input

Impedance

7 ohms nominal 4 ohms minimum

 

B&W 702 S2:

Power Range 30-300 
Frequency Response 46-28k Hz 
Sensitivity 90 dB 
Impedance (Ohms)

 

As I pointed out earlier the 46 Hz versus 29 Hz is reflected in the low freq trailing off in the link. So one would expect the 2C versions to play with more authority at the lower frequencies.

However the 86 versus 90 dB sensitivity, would favour the 702S2.

The “fact” that that same amplifier works nicely on the 2C can make us wonder if it is all in the more extended low frequency? Or if there is some load complexity that is also at play?

Does that MS252 have a variety of transformer tap impedance posts?
And was it using the 8 ohm tap?

Glad you got it sorted but I would have never guess it was power. I have only used the Big Macs though and my MC462 seems to plow through anything hooked up to it. Maybe the lower powered Mac can’t handle the impedance curve. 

@dridel,

Bravo!! Glad you are happy now with the sound of the B&W 702's.😊This article came to mind on bi-amping speakers. Thought you might like it. In my experience I always found bi-amping to sound better then a single amp.

Mike

 

OP. Thanks for the report back. I would not have thought that was the problem. While more power helps solidify bass, etc. That big a difference is surprising to me. But, really glad you solved the problem. 
 

For power conditioners, they improve most folks systems, but occasionally they don’t… put yourself into the lucky category.

Update:

It was the amp.  After checking all connections and trying unsuccessfully to play with positioning and with the amp's EQ, I gave my local dealer a call and they graciously allowed me to borrow their MA352.  They also made me borrow a power conditioner promising it would make a difference.  Coincidentally, they had a pair of 702 S2 driven by a 120W Rotel amp, so I got to audition the speakers there, and they sounded glorious.  So this is what I did when I got back home:

  1. Added the power conditioner to the MA252+702s: sound was still anemic at low volumes, fatiguing at higher ones. Dare I say no difference at all.
  2. Hooked up the MA352 with power conditioner (PC+MA352+702s): massive, immediately noticeable difference.  Speakers came to life and all my issues with them resolved completely.  Sound is big even at lower volumes, tones have texture throughout the spectrum, no instrument is left behind, bass is very present, fast, impactful, on your face but not boomy or overrepresented.  Sound is natural and emotionally engaging, exciting.  This is exactly what I was hoping to achieve with the speaker upgrade.  Big smile on my face again. I already know I've hit home and this is likely my end-game system. And this before even playing with EQ, biwiring, room treatment, positioning, etc. Heaven!

3.  Removed the power conditioner from the chain: this one was trickier.  Multiple back and forths and testing multiple songs.  If there is an improvement, it is subtle and barely noticed on A/B comparisons. Next step is blind tests which I will do later today.
4.  Finally, and just out of curiosity, I tried the 683s with the MA352: this was a hard comparison as it had been at least a day since I last listened to the 683s, but wow they sound great.  Yes, the 702s are better at everything, but if I couldn't afford them, the 683s would definitely do. Does the MA352 drive them better than the 252? Possibly, but if it does, it's not by a lot.

I am still getting a sub (used REL S5/SHO), so I will report back on how much it contributes, but I can tell you, now with the MA352 I feel no need for a sub.  Maybe that will change when I try one, but if not, the REL will be a great addition to my secondary system/home theater.

I just don't understand why B&W would rate this speaker 30-300W when even 100W were not enough to drive it properly, and when they recommend themselves using at least half of the maximum power.  I learned than an amp wattage is not just how loud it can get, but that it affects the quality of the sound even at lower volumes when output wattage is waaaay below the max.

I'm so grateful for everyone's input, and special kudos to @erik_squires @ditusa @samac @mofojo @jpconer @styleman @sandthemall @dinov @steve59 for getting it right.

For anyone who's interested, here are a few songs I thought were useful during all my tests (particularly the first 30-60 seconds of each).
- Lithium (Nirvana) for thar punchy drum kick that comes in with the highhat
- Better living through chemistry (QOTSA) for the realism of the initial percussion followed by the broad, bass rich distorted guitar that fills the whole room
- Gagging Order (Radiohead) good mids and highs from a clean, sweet acoustic guitar
- In the cold, cold night (White Stripes) for separation and balance of instruments and the soul shaking, precise bass line
- Acid Rain (Liquid Tension Experiment): for a busy, distorded, very stereo, complex analog metal song with challenging separation
- Twentysomething (Jamie Cullum): nice acoustics that allows you to listen to piano and vocals before introducing punchy drums and bass

Thanks to everyone who contributed.  I hope others also find this thread helpful as I'm sure I wasn't the only one unknowingly underpowering my speakers.

Daniel

The warmth is from the amp in that case. The 2C is highly detailed, but never harsh unless said amp is harsh. Many love he Mac because it makes most systems sound nice. I like that amp with many speakers if heard it with. It’s a flavor thing,

I have auditioned your amp driving Vandersteen 2Ce Signature III as pointed out by @ctsooner.  MA seems to drive Vandersteen 2Ce reasonably well with full bottom end but the pairing sound a bit warmer to my liking.  But that is a matter of personal preference.

The speaker and amp need to be considered as one. Get this right. 

wise words

Sensitivity 90 dB  ~~~~~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~~~~~~~~ Sensitivity = Efficiency. Same deal Below 90db, = INEFFICIENT. 92db+ = High efficiency = more EFFECTIVE, = More functual = More musical. Ideal db sens is 93-95. Above 95 too high = too forward, too loud, sound attacks. Yeah yeah I know horn folks love their 100 db speakers,, a SPL blast I could not deal with for longer than 1 hour. THe ideal, if not perfect speaker design are the Full range single driver, invented wayyyy back in the late 1920’s in Berlin and Chicago.

IMHO these speakers are the most musical,  most practical, most enjoyable. ...of any speaker design.

btw I just recently discovered, FR work best in open baffel. 

These  complex horn boxes which are very expensive, I

'm not going for.

Yeah yeah I know they do this horn thing for added bass.

Just add a  W6 FR, there  ya got padded bass.

@dridel   Posts on how to 'fix' something, despite their validity and effectiveness, nearly always shine a spotlight on a fundamentally broken pairing.

The speaker and amp need to be considered as one. Get this right. 

 

I honestly don't think you are underpowered. What size room are you in and do you have an app to see how many decibels you are hearing?  

Please keep in mind that your speakers only go down to 46 hz or so.  That's not low at all.  From what I remember of the speaker (S2 version), the bass is very tight, but not 'full' like you'd expect a floor stander this size to have.  

Did a quick comp spec wise (not listening, just to show the difference in bass and efficiency).  the 702 sells for $6K/pr. The Vandersteen sells for $3,600/pr including the stands. That's nearly twice the cost.  

 

Vandersteen 2CE Signature III:

Recommended Amplification

40-160 Watts Into 8 Ohms

Frequency Response

29Hz – 29kHz +/- 3dB

32Hz - 21kHz +/-1.5dB

Sensitivity

86 dB, 1 meter with 2.83 volt input

Impedance

7 ohms nominal 4 ohms minimum

 

B&W 702 S2:

Power Range 30-300 
Frequency Response 46-28k Hz 
Sensitivity 90 dB 
Impedance (Ohms)


 

I don’t know anything about your Mac amp but could you buy another of what tou have and run them mono or bi-amped?

I’m impressed, some excellent suggestions! You have your work cut out for you, this will keep you busy for a while I would imagine. Take your time and listen closely. I would start with imhififan’s idea first just to eliminate the possibility of driver phase error. Nothing else will help much if this is the problem! Good luck.

If you have played with placement and still aren’t happy, maybe it’s time to move the speakers. Go audition others with your amp. 100w that can double into 4ohms is plenty powerful for most speakers in a reasonable room. The Mac gear isn’t my favorite, but it’s a premium amp that does very listen wrong (for the price I just like some other gear better in My system). I have friends who own Vandersteen’s and Wilson’s who love Mac with it. I’ve never heard that amp sound bad,  nor unpowered ever. 
 

adding a sub just adds more to the equation. In the right situation they can be awesome, but in you case why throw more money if you are chasing your tail to get  better bass from a pair of speakers. Multiple ways to fix something that shouldn’t need fixing.  Good luck.  

 second amp to drive the woofers. use the pre outs to a mac amp thats rated with 50% more power than the current amp and slave it to the woofers.

1. Have they had a sufficient break-in period???  2. As someone else suggested, you may want to place an ad here or on Craigslist to see if someone has a higher-powered quality amp who wishes to audition the 702's before pulling the trigger on them.   Not a big fan of subs for 2 channel towers, prefer them with HT.  A $7500 pair of towers shouldn't require a sub-woofer if sufficiently powered and broken in, unless in a huge room...

@dridel

Neither playing with the EQ at the source nor the amp was satisfactory.

What sort of EQ options did you have at the source and at the amp?
 

How about some measurement like an REW graph of the left and then the right channel? (And finally both)

That would answer a lot of questions, including @imhififan woofer issue in the Theils.

There is no easy way to make a rational decision on multi k$ changes to fix the problem, without first having some factual way to understand what is (or maybe) the problem.

@james633 totally agree about his reviews, you just have to look at how he raves about the Auralic Altair G1 as the best streamer available which is a paid review. Nothing against Auralic, I own the ARIES G2.1 and love it, but the minute you put a review out like that as paid, it undermines everything else.

@dridel from your further comments it does sound like there might be a synergy issue here if the highs are unbearable, however B&W are known for having a bright treble (from the many reviews and conversations with dealers) which will become more apparent higher up the chain as it becomes more resolving. However it is worth trying the free stuff first before changing gear. You may also want to hang duvets and get more soft furnishings in your room if it’s got a lot of bare walls at the moment to see if it’s the reflections that are emphasising the treble. Just worth trying all the easy free stuff first before buying more and becoming disillusioned if it doesn’t fix it, as the sound you are after is out there!

Another aspect of this is that the issue doesn’t resolve with high volume, which yes, comes with a better bass response but at levels where the highs are too piercing and fatiguing. The amp and speakers ARE capable of getting to good bass levels, but not in balance with the rest of the frequencies.

Years ago, I had a similar problem with my Thiel cs1.6 and cs2.4, the cs2.4 that I bought used at this site had weak bass compare to the cs1.6 in my system!

I perform a battery test and found out the culprit was one of the woofer wired reverse polarity.

you should burn both the amp and the speakers, if they don't pair well, it's possible they just refuse pairing. 

The combo of MA252 and BW 683 S2 (raved by Stereophile) is the first 2-channel I have auditioned. I was satisfied by, in particular, its full/sweet midrange but somehow the mid-bass is a bit boosted/muddy and the bass note is neither tight or fast to my liking. In terms of Lab measured freq. responses, they were both rated down to 30Hz (683) and 28 Hz (702) but those are at -6dB. At -3dB, they were only at 52Hz (683) and 45Hz (702) despite of being a floor stander. Basically, for both models, the mid-bass is boosted before rolling off at a rather deep slope. Later I switch to different I.A. with higher wattage/current, same story and that leads me to believe the speaker is the weak link. I guess you just need to identify another set of speakers that have well-defined bass notes to your taste.

A pair of REL S2 SHO Subwoofers would solve the problem.  Take some of the weight out of the towers and create a better sound stage.

I would not trust Andrew Robinson’s opinion. He seems to lack highend experience or be a paid shill, I am undecided. No hard feelings toward the guy but you will get better advice here.