The B&W 603 speakers were measured in free-air at a height of 4 feet at a 2-meter distance from the microphone, with the microphone raised to a 7’ elevation that was level with and aimed at the tweeter center. The measurements were gated at 8-milliseconds. In this time window, some resolution is lost below 400 Hz and accuracy is completely lost below 200 Hz. Measurements have been smoothed at a 1/24 octave resolution.

Horizontal Response +/- 95 degrees



The above graphs depict the B&W 603’s direct-axis and horizontal dispersion out to a 95-degree angle in five-degree increments. This is a decidedly imperfect response, and the elevated treble was something I sensed right away but was able to greatly alleviate by having the speakers face outward in a parallel direction rather than toed in to face the listening position. It’s an odd response considering the design of the speaker. I expected the dispersion of the midrange driver to contract as it moved up in frequency, but the narrowing at 2 kHz is lower than I would have guessed; I expected that behavior around 3 kHz. The on-axis response has a strange dip in the peakish treble around 6 kHz that goes away off-axis. The on-axis response here is problematic, but the off-axis response is not so bad. It’s not easily clear from this densely packed set of measurements, but around 30-degrees the treble flattens out without the midrange getting sucked out too much from that 2 kHz dip. Let’s take a closer look:



B&W 603 Horizontal Response on-axis, 30-degrees, and 35-degrees

The above graph compares the on-axis response to the response at 30 and 35-degrees. These off-axis angles have a much tamer treble sound. The dip centered around 2 kHz is still an issue, but that isn’t something I particularly noticed in listening, unlike the on-axis treble peaks. On-axis, the treble was rather sibilant, but, as was mentioned before, this quality was significantly reduced by angling the speakers that put the listener well off-axis. The response at 30-degrees is not bad overall and does produce a nice sound. I imagine this was the listening angle intended by B&W, although it is not stated anywhere in the literature for these speakers.

B&W 603 Polar Map of Horizontal Response +/- 95 degrees

The above polar map shows the same information in the preceding graphs but depict it in a way that can offer new insight regarding these speakers’ behavior. Instead of using individual raised lines to illustrate amplitude, polar maps use color to portray amplitude, and this allows the use of a purely angle/frequency axis perspective. The advantage of these graphs is they can let us see broader trends of the speaker’s dispersion behavior more easily. The most immediate feature is that the 603s are a very wide dispersion speaker for the most part. In this polar map, we get a better sense of how the directivity of the midrange driver narrows as we move up in frequency, at least until the tweeter begins to take over. The 2 kHz dip doesn’t look to become severe until past 40-degrees. The dispersion of the tweeter is very wide, at least up to 10 kHz. To be sure, the 603s do not seem to be overly concerned with directivity control. These speakers will take on a fairly different sound character depending on the angle they are listened to.



B&W 603 Low-Frequency Groundplane Response

The above graph shows the B&W 603 low-frequency response that I captured using groundplane measurements (where the speaker and microphone are on the ground at a 2-meter distance in a wide open area). In this measurement, we can see that the 603 does begin to roll off at a somewhat high frequency, but that the slope is very gradual. The speaker has some real bass extension, although a bit rolled off. For my tastes, this response without boundary reinforcement was a tad anemic. However, placing the rear end of the speaker close to a wall will load the port, and with this type of response, that can really bring out the bass. Some people might find that type of placement will produce too much bass, and if so, the user can pull the speakers out into the room more, or they can use the port plugs. As was discussed before, the port plug can seal the port, but its core can also be removed which merely damps the port. Here are the differences the port plug makes in both of its configurations.

B&W 603 Port Plug Differences on Low Frequency Response

In the above graph, we can see the reduction in bass caused by the port plug modifications. The top curve is the low-frequency response with the port open. We can see here the resonant frequency of the port looks to be in the mid to upper 20’s Hz range. The middle curve is the effect of the port plug with an open core; here we can see that some port output is permitted but at a significant reduction to a totally open port. The lower curve is the response with the port completely sealed which naturally eliminates all port output.



B&W 603 Impedance and Phase Response

The above graphs show the electrical behavior of the B&W 603. Bowers & Wilkins specifies the impedance load of the 603s to be 8 ohms nominal with a 3-ohm minima. However, in our testing, that is a pretty optimistic characterization of the overall impedance. The upper bass region and a big chunk of midrange frequencies hover around 5 ohms with a 4-ohm minima at just above 100 Hz. We can see from the low-frequency saddle that port tuning is just below 30 Hz, and that is a relatively deep tuning frequency for a speaker of this size. The good news is that the impedance curve is pretty stable and does not have wild swings. The bad news is that there are some rather steep phase angles in low impedance points in the bass frequency range. That will make this speaker a tough load for cheap receiver amplifiers. These speakers should be used with amplifiers that are rated to handle 4-ohm loads, especially if the user intends to push these speakers to loud levels.



The 603’s sensitivity measured at 86.8 dB for 1 meter at 2.83v. That isn’t that far from B&W’s spec of 88.5 dB, and the difference could be due to a number of factors. 86.8 dB is somewhat low for a tower speaker, but it isn’t surprising given the deep tuning frequency. These speakers have some real bass extension, but they pay for it in sensitivity. The sensitivity isn’t bad though, and users will not need a monster amp to drive these to loud levels.

Conclusion

In my time with the 603s, I found them to be a bit of a strange bird. They could sound very good, but they needed placement and angle fussing to get there, and the measurements show why. Nonetheless, once I had them set up just right, I quite enjoyed them. Before wrapping this review up, I want to briefly go over a few of their highlights and also some of their shortcomings as I do with all the products I review. Since I am the kind of guy who always wants the bad news first, I will list some of their weaknesses before discussing their strengths.



The 603’s foremost flaw is, in my opinion, the elevated treble response around the on-axis angle. Listening on-axis could make some recordings sound quite harsh, especially rock or pop music. It also gives many vocals a sibilant sound where the T, S, and CH parts of speech were overly emphasized. This can be greatly alleviated by positioning the speakers to be facing straight ahead so that they have no toe-in angle toward the listening position. As I said before, my hunch is that this is how they were intended to be positioned, but that isn’t stated anywhere in B&W’s literature for these speakers. For the best sound, keep the listening position around a 30-degree angle with respect to the on-axis angle as that will provide the most neutral direct sound. Room correction equalization such as Audyssey cold probably tame the treble for those who want the speakers aimed at the listening position but without the hot treble sound.



Another complaint I would list is that th ere is a dip in the response centered around 2 kHz, however, this might only be an academic complaint since I didn’t hear anything missing in this upper midrange band during actual listening. This flaw may be audible if this speaker were directly compared to one that had a flat response in that range, but it didn’t bother me in practice. However, it would be a technically better speaker were that dip not there, and past a 40-degree angle, it becomes a very substantial gap. In my opinion, the idea of sequestering so much frequency range to this midrange driver was not worth the penalty in directivity control. This dip may be an unavoidable consequence of crossing over the midrange driver to the tweeter at such a high frequency.



Those are my only gripes with the 603s, so now let’s move onto their virtues. As I said, once positioned correctly, they sound delightful. I wouldn’t characterize them as warm even with optimal positioning but they aren’t harsh either. They can be very detailed without accentuating treble frequencies too much. Their imaging is outstanding. If you want speakers with a wide yet precise soundstage, these are a terrific choice. With a port-tuning of below 30 Hz, their bass extension digs deeper than many of their similarly priced peers. The bass level isn’t too high, and users can take advantage of boundary gain to elevate low-frequency output to their taste. Those who want heavy-duty, bombastic bass will still want to use subs, but most people will be perfectly satisfied without a sub.



Outside of the tonality of the speakers is their good dynamic range. Although the 603’s sensitivity isn’t terribly high, they can still pack a punch if given sufficient amplification. That isn’t all that surprising with a 6” midrange cone. However, a beefy amplifier is definitely helpful with these speakers when one considers their midrange impedance load and middling sensitivity. When combined with a good amp, the 603s could tackle a good-sized room without breaking a sweat.



The 603s look very classy as well. The silver midrange and tweeter serve as a nice visual focal point against the hard-edged flat black cabinet. Without grilles on, they might clash a bit in highly traditional decors, but with grilles on they are pretty innocuous and would disappear in almost any interior design. They would really make a nice fit in modern interior styling.



The 603s have a sense of solidity that exceeds their pricing. The cabinet is very well-braced and has a heaviness that is reassuring. It gives an impression of a speaker that is built to last.



In the end, I enjoyed my time with the 603s even though I have to concede that they have unquestionably flawed response characteristics. I am not sure how B&W settled on the type of response that the 603s produce. I am sure that B&W has the engineering chops to achieve any kind of frequency response that they want. My guess is that they were so intent on adhering to certain design principles that they were willing to pay the penalty in the frequency domain, whatever that penalty was. The result is a loudspeaker that has an odd change in tonality depending on the angle of listening. They can sound good but they need finessing in terms of positioning and placement. The good news is that type of positioning that they benefit from is fairly common as a default speaker placement in many people’s homes. And once they are setup right and the music is playing, the listener is rewarded with a crisp, natural sound that is easy to listen to for hours on end.