Bowers & Wilkins 705 S3 loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Bowers & Wilkins 705 S3's behavior in the farfield, and an Earthworks QTC-40 mike for the nearfield responses. I left off the grille that covers the woofer for the measurements.

Fig.1 Bowers & Wilkins 705 S3, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

B&W specifies the 705 S3's sensitivity as 88dB/2.83V/m. My B-weighted estimate was a little higher, at 88.9dB(B)/2.83V/m. The 705 S3's nominal impedance is specified as 8 ohms, with a minimum value of 3.7 ohms. The speaker's impedance magnitude (fig.1, solid trace) remains above 5 ohms for almost the entire audioband, dropping below 4 ohms above 15kHz. The electrical phase angle (dotted trace) is occasionally high, as a result of which the equivalent peak dissipation resistance, or EPDR (footnote 1), lies below 3 ohms in the bass and lower midrange, and below 2 ohms in the top two octaves. The minimum EPDR values are 2.63 ohms at 56Hz, 2.33 ohms at 117Hz, and 1.92 ohms at 8.6kHz. The 705 S3 needs to be paired with amplifiers that don't have problems driving low impedances.

Fig.2 Bowers & Wilkins 705 S3, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall (measurement bandwidth, 2kHz).

The impedance traces are free from the small discontinuities in the midrange that would imply the existence of resonances of various kinds. When I investigated the enclosure's side and top panels' vibrational behavior with a plastic-tape accelerometer, I found a strong resonant mode at 617Hz on the speaker's sides (fig.2). As this mode is relatively high in frequency and has a high Q (Quality Factor), it may have no audible consequences.

Fig.3 Bowers & Wilkins 705 S3, acoustic crossover on tweeter axis at 50", corrected for microphone response, with the nearfield woofer (green) and port (red) responses respectively plotted below 500Hz and 900Hz.

The Bowers & Wilkins speaker's impedance-magnitude plot has a saddle in the bass centered on 45Hz, which suggests that this is the tuning frequency of the flared port on the rear panel. (Fig.1 was taken with the port open; with the port blocked with the supplied foam plug, the impedance has a single peak at 69Hz.) The woofer's nearfield response (fig.3, green trace) has the expected reflex notch at this frequency, and the port's output (fig.3, red trace) peaks between 30Hz and 80Hz. The port's upper-frequency rolloff is initially clean, though some significant resonant peaks are present between 400Hz and 800Hz. This behavior may well be ameliorated by the fact that the port faces away from the listener. The complex sum of the woofer and port responses is shown as the black trace below 300Hz in fig.4. The apparent boost in the upper bass is mostly an artifact of the nearfield measurement technique, which assumes that the baffle extends to infinity in both planes. The 705 S3's reflex alignment appears to be maximally flat, in textbook fashion.

Fig.4 Bowers & Wilkins 705 S3, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and port responses plotted below 300Hz.

The woofer crosses over to the tweeter (fig.3, blue trace) at 3kHz, with shallow low-pass and high-pass filter slopes. The tweeter's on-axis output then rises precipitously, peaking by almost 10dB at 10kHz. (Both samples were identical in this respect.) The response then drops by the same amount before starting to rise again above 20kHz. I don't have a microphone that allows me to measure frequency responses above 40kHz; the tweeter's fundamental dome resonance appears to lie above that frequency. (Paul Miller, in Stereophile's sister magazine Hi-Fi News, found that the dome resonance of the similar tweeter in B&W's 703 S3 floorstander occurred at an extremely high 49kHz.)

Fig.5 Bowers & Wilkins 705 S3, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90–5° off axis, reference response, differences in response 5–90° off axis.

Fig.6 Bowers & Wilkins 705 S3, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

The 705 S3's farfield output, averaged across a 30° horizontal window centered on the tweeter axis (fig.4, black trace above 300Hz), still has the rising response above 3kHz, despite the spatial averaging, due to the wide horizontal dispersion in this region (fig.5). Fig.5 does indicate that the top-octave output starts to fall off beyond 20° to the speaker's sides, so directing the speakers straight ahead instead of toeing them in toward the listening seat should reduce the audibility of the energy excess in this region. In the vertical plane (fig.6), a suckout appears in the crossover region 5° above and more than 10° below the tweeter axis. The speaker should be used on a sufficiently high stand to place the listener's ears on or just below the tweeter axis.

Fig.7 Bowers & Wilkins 705 S3, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.8 Bowers & Wilkins 705 S3, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Moving to the time domain, fig.7 shows the 705 S3's step response on the tweeter axis. The tweeter's output arrives first at the microphone. The two drivers are connected in positive acoustic polarity. The small discontinuity at 3.9ms, which is when the decay of the tweeter's step blends with the start of the woofer's step, suggests that the outputs of the two drivers optimally blend just below the tweeter axis. The B&W speaker's cumulative spectral-decay plot (fig.8) is clean overall. (As always, ignore the apparent low-level ridge of delayed energy just below 16kHz, which is due to interference from the MLSSA host PC's video circuitry.)

The 705 S3's measured behavior is enigmatic. That response peak at 10kHz will not be heard as "brightness" as such. Instead, it will add "air," "transparency," and "openness" to the perceived balance. But it will make system matching tricky and may emphasize surface noise with vinyl playback.—John Atkinson

Footnote 1: EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier's output devices as the loudspeaker. See "Audio Power Amplifiers for Loudspeaker Loads," JAES, Vol.42 No.9, September 1994, and

Bowers & Wilkins North America
5541 Fermi Ct. N.
CA 92008
(800) 370-3740

jimtavegia's picture

This speaker is probably right up my alley as it follows the Harman headphone curve I need these days. My only concern is the price with the stands as mentioned.

There are so many great floor speakers at $4K that would take up the same amount of floor space and fill out the bass region somewhat better. Still a great review with excellent info.

Ortofan's picture

... using an equalizer, such as the Schiit Lokius (or Loki Max) - along with the speaker of your choice.
While this B&W speaker has a high frequency peak at about 10kHz, the Harman curve peaks at around 3-4kHz.
Likewise, you could dial in however much bass boost is desired.

It'd be interesting to have a direct comparison between the 705 S3 ($3.4k + stands) and the floorstanding 704 S3 ($4k) to find out which one might be the better option for about the same total cost.

jimtavegia's picture

Your point is well taken and I would love a follow up review as you suggested.

I have looked at the EQs from Schiit as well. I have seen that the AKG K612 follow the Harman curve even better and I prefer the bass left flat for my tastes. I have found the Vali a very nice headphone amp as well and it does not have a "tube sound" that I can detect, but just sounds great to me, slightly less than my Asgard.

I have gone this route to not bother my family as much with all my music listening. I have had headphone amps from Art, Presonus, and Focusrite from my ex-USB box and the Schiit's all beat them quite easily and I have passed the others along to family and friends who could use them. Two of them are multi-headphone output models.

This might have been ever more interesting to compare the B&W's vs the KEF LS50 Meta, but the prices are quite different. This might be a good follow up for JA1.

Trevor_Bartram's picture

The Koss KSC75 headphones have gentle boost in the midrange you're seeking. They use a titanium coated polymer driver to achieve the 'sound'. Other Koss headphones using the same basic driver do not use titanium and don't have the 'sound'. The KSC75s are very inexpensive (<$20).

jimtavegia's picture

I have enjoyed my AKG K701s and just bought Monday a pair of AKG K612's for $140 off Amazon. They have a little more bass from 100hz to 400hz which makes them slightly warmer and fuller sounding with the same highs as the K701s. They are not broken in yet, but I think that based on the music it is an easy choice to pick which cans will sound better "to me". If you have excellent HF hearing you might enjoy the K612 better. The K701's are now $200 on Amazon. No dealer stocks AKG around here.

My Tony Kadleck Big Band CD "Sides" came yesterday and it is superbly recorded and sounds great. Don't miss it.

cognoscente's picture

What applies to wines also applies to audio. Or fashion. Prices are not objectively determined by quality but by prestige. I am now in the middle of the Bordeaux 2022 subscription campaign and bought a 96 point wine (average of at least 10 reviews) for 55 euros, while a wine with the same rating came on the market today for 302 euros. I would expect all 96 point wines to be about the same price. Not so, certainly not even. And 97-98 points wines are for sale from 150 euros to 999 euros. I also see it in audio, perhaps less strongly but still. Prestige determines the price and success. What is B&W type of wine?

Ortofan's picture

... variety of grapes and the production process are specified by a vintner located in the UK, while the grapes are grown and the wine made and bottled in China?

cognoscente's picture

Viewed exactly does any comparison fall short on the basis of differences that are always there, indeed. I'm just trying to make a point and clarify. Btw there is also sympathetic made-in-China like my Holo Audio dac. Invented, designed and made by Chinese in a small factory in China. To me that is the same as made-in-UK or made-in-EU or made-in-USA. Even though wages are lower there. But they are also in Greece or Italy, just to name two countries where audio also comes from.. Then we are not even talking about Romania. But I get your point.

And there is Iranian wine. Grapes from Iran, shipped to France where they are made into wine and then sold as Iranian wine world wide. Except in Iran itself, although people there make their own wine in the cellar.

Anton's picture

Is there a certain method to how they taste and rate the wines you mention?

If there are two 96 points ones, what happens if you prefer one over the other?

cognoscente's picture

As for wine ratings and reviews, I think and hope the same as with audio. Professionals who put aside subjective preference and judge it by objective standards. As I trust (some) audio reviewers, I do the same with wine reviewers. If everyone has more or less the same opinion, I trust it. Not if one or two reviewers love it and everyone else just likes it.

And yes, in the end it is the end consumer who makes an individual and personal choice. But the pre-selection, at least I leave it to professionals, after all, there is too much on the market to make the big pre-selection yourself.

PeterG's picture

A great review of a fine speaker. But having owned 3 B&W stand-mounts over the years, I'd say they are really meant to be paired with a good subwoofer. Though this adds obvious issues into the review process, I'd love to know how they'd fair against the Revels and KEFs when given an extra boost for the low stuff

Long-time listener's picture

I just don't understand why B&W continue to think that boosting the highs is such a good thing. Even listened to way off axis, the response is still significantly high between 4-8 KHz. And it's not really balanced by deep bass. As John Atkinson said, the measurements are a bit "enigmatic." I.e., puzzling.

David Harper's picture

I bought a pair of B&W stand-mounted speakers a few years ago. They were very well reviewed in the audio press. I think they were model 606(?) I don't remember. Brought them home and listened for a week.I hated them.
They sounded LOUD, harsh,bright and unlistenable. Returned them to Best Buy. I was used to Polk speakers which have a very smooth laid-back sound so maybe that's why I hated the B&w speakers.

Ortofan's picture

... high-frequency peak represents an ideal response curve, you wonder why they don't include a switch/control that would allow the selection of something closer to a flat(ter) frequency response, let alone a slight roll-off.

Given that the woofer and tweeter connections are brought out to separate terminals, one could experiment with an external network to bring down the high-frequency peak.

jimtavegia's picture

Maybe their new marketing plan should include AARP's magazine.

remlab's picture

paired with a relatively large, baffled midbass. Looks cool, but from a physics perspective, it's just a terrible idea. I'm amazed that B&W has stuck with this gimmick over the years.

johnnythunder1's picture

France's Jean Marie Reynaud brand - their Cantabile Jubile to be exact - has a decoupled silk dome tweeter and it sounds amazing. Lovely, smooth, bright and musical. They have an almost effortless electrostatic sound to them. The sound has a delicacy and spaciousness that is very appealing to me (I own them.) B+W speakers always have sounded too bright to me. Metal dome tweeters vs. silk domes maybe. Or just a tipped up treble that isn't to everyone's liking.

Ortofan's picture

... a function of the material used for the tweeter dome, consider the performance of the recently reviewed (and similarly priced) Monitor Audio Silver 500 7G. It has an aluminum/magnesium tweeter, yet the frequency response is "impressively even from 300Hz to 11kHz" and then it rolls off above that point in the audible range.

johnnythunder1's picture

- I'm sure there are speakers w silk domed tweeters that are executed poorly and metal dome ones that are smoother (or at least voiced to sound smoother.). I have never owned a speaker with a metal dome tweeter finding them just too fatiguing to my ears (sensitive+tinnitus.) Spica Tc-50s. Spendors. JMRs for the past 20+ yrs..). I have also enjoyed and considered purchasing QLN speakers and NOLA Boxers....

Trevor_Bartram's picture

What you're getting here is a superbly manufactured speaker, just look at the cumulative spectral plot to confirm, that is designed for a well heeled audience with hearing loss. The bass alignment (+3dB, 150Hz) will lead to chestiness from radio announcers etc in-room. My Paradigms have the same problem. I've inserted passive electronic equalisation between my pre & power amp to solve the problem without effecting low bass (<100Hz) as tone controls would do. Perhaps I should manufacture the circuit?