2. speakers
  3. 174352-154490

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
jjss49's avatar
Ag insider logo xs@2x
jjss49
6,612 posts
 

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

david_ten
5,480 posts
 

+1  @jjss49 

ghdprentice
7,186 posts
 

Excellent explanation. @jjss49 

 

 

missioncoonery
1,227 posts
 

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

rbwnc's avatar
rbwnc
18 posts
 

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.

More to discover