An afternoons comparative listening to 5 pairs of powered audio monitors

This past weekend a friend and I spent an afternoon listening comparatively to a collection of powered audio monitors. It was by no means a scientific study, just a casual session of listing to music in a focused manner.

We used three Slim Devices Squeezebox 3s as sources, all playing in sync from a music server. The SB3s were running Squeeze Center v7. We setup a playlist of music we both knew well then switched between monitors in pairs.

We tried to get all the levels matched so as to make the easiest comparisons. But we didn’t use any instrumentation to make level or frequency response measurements.

The goal is to generate an opinion on the hardware at hand. The present collection of hardware I intend to use for a distributed, whole house audio system. The opinion developed would then become the basis of my planning for a home theater setup.

Here’s what we found. In order of preference; best to worst.

1. Alesis Pro Linear 820 DSP

MSRP = $699 each, but discontinued in 2007. Acquired online 3/2008 for $249 each.

These are by far the largest monitors in our arrangement. They are two way with 8″ woven kevlar woofers and 1″ silk dome tweeters. The woofer is powered by an 80 watt power amplifier, while the tweeter is driven by a 40 watt amp.

What’s really unique about these is that the crossover is implemented in the digital domain using a DSP chip. By doing it this way the maker provides very tight control of the crossover behaviour, as well as a four band parametric equalizer in each monitor. The eq includes a series of 8 presets and 8 user memories. The presets are supposed to mimic common control room monitors such as Yamaha’s NS-10s, Aurotone cubes, etc.

For the purposes of our listening session we left the eq in preset 1 which is flat response.

The enclosure is ported for enhanced bass output. The front panel is a molded plastic material while the rest of the cabinet has a plain grey vinyl cover over MDF. In truth, the cabinet finish is not all that great. They’re just not attractive. They look cheap.

Sonically the 820s are simply the best of the bunch. They reach deepest into the bass, and had the smoothest and most balanced upper end. The low end was quick, not sloppy or boomy.

We listened to a range of music, from rock to jazz and classics. We especially listened for voices on solo singers and strings on orchestral pieces.

They are capable of playing quite loud but were not the most powerful in the bunch. The amps were warm to the touch under most listening conditions. The weight of the cabinet, not as heavy as the Behringer B2031A, suggests the use of a digital switched mode power supply. Traditional transformer power supplies would simply be much heavier.

Even after extended listening we felt that these were the best of the bunch. The pity is that they were some time ago discontinued by Alesis. However, they are available refurbished direct from the manufacturer or from a limited range of online sources.

2. KRK Rokit 5

MSRP = $299 pr. Can be found for $198 pr.

These are almost the smallest monitors in our collection. They feature a 5″ woven kevlar woofer driven by a 30 watt amp. The tweeter, a 1″ soft dome, is driven by a 15 watt amp.

While physically small these sounded the best balanced of all the small models. Just not capable of the low end output of the larger 820’s or 2031a’s, they nonetheless presented very well, with nicely detailed midrange. They were especially clean on complex passages of female voice and strings.

These two also featured the least amplifier power of our test group. This limited their maximum output level. It made me think that perhaps I should audition the larger Rokit6 or 8, which feature more power and better low-end output.

For my home theater application they would need to be augmented by a sub-woofer, which was in the plan anyway.

The cabinet was finished in a semi-gloss black lacquer. In fact, the KRKs build quality was easily the best of the test group.

3. Alesis M1 Active 520

MSRP = $299/pr. Can be found online for $179/pr refurbished.

I’ve had this little pair of monitors for about four months. They’ve been installed into our living as part of the whole house audio project. They’re very inexpensive, yet sound surprisingly good.

Alesis claims that they provide 50 watts into the 5″ poly cone woofer and 25 watts into the 1″ silk dome tweeter. For their size they play reasonably loud, but can easily be overdriven. I expect that Alesis’ stated power output is a little optimistic. Perhaps peak output vs rms output. The amps are self protecting, and the power on LED in the top of the cabinet flickers to red when the amp engages a limiter to protect the driver from clipping.

These little 520’s get down surprisingly low. There are a range of adjustments on the back of the cabinet including;

• Low freq filter -3 db point @ 56, 80 or 100 Hz to limit low freq power when used with a subwoofer
• Mid freq level boost on/off
• High freq level boost, level or cut
• Acoustic space compensation; free space, against a wall, or in a corner

By tinkering with these controls we could get a very pleasing sound from the 520’s, but not at the higher levels of the larger models. With the max bass extension dialed in the bottom end was boomy, but when set for 80 Hz roll-off it seemed better balanced.

I do wish that the 520s had signal sensing automatic power on/off. This would keep them from consuming power 24/7 as I presently keep them located such that it’s not convenient to reach the top mounted power switch. Also, the blue power-on LED is very bright. I may end up covering it over with tape so that it’s not so obtrusive in a darkened room.

On the whole the M1Active 520s were not the worst of the bunch, even if they are the least expensive.

4. Behringer B2031a

MSRP = $399/pr. Can usually be found for $260/pr.

These are two way systems, the 8″ poly cone woofer driven by 150 watts, while the 1″ aluminum dome tweeter is backed by a 75 watt amplifier. These have been my main office listening system for about two years. As I’ve written elsewhere, I think that they are very good value for the money, and reasonably accurate.

Of all the systems here these provide the most amplifier drive and are simply the heaviest. The amps are traditional class A/B designs with a robust power supply built around a massive tordial power transformer. All this means that they can run load, and hot, while delivering some serious volume.

However, compared to the Alesis 820s the Behringers upper-end sounds harsh and strained. Also, the lower end, while very capable is slower then the 820s. I presume this is the result of the higher moving mass of the poly woofer compared to the light but stiff woven kevlar cone of the 820s.

The B2031a’s are provided with a reasonable range of adjustments on the crossovers. The end user can adjust the high-end or low-end balance as well as compensate for placement in the room, in a corner or against a wall. There’s also a mute switch for each of the amps allowing you to completely defeat the woofer or tweeter if desired.

So while I still like these it appears that they have been displaced as my primary listening choice. Perhaps I’ll get a chance to audition Behringer’s newer B3031a’s which sport new kevlar woofers and a ribbon tweeter. They may compete better with the Alesis 820’s.

5. M-Audio BX5a

MSRP = $399/pr. Can be readily found online for $199/pr.

M-Audio’s BX5a pair a 5″ woven kevlar woofer with a 1″ silk dome tweeter. Bi-amped, they are driven by 40 watts & 30 watts respectively. The crossover is a 4th order Linkwitz-Riley filter centered at 3 kHz. That means 24 db/octave roll-off out of band for each driver.

At first listen they sounded really nice, if a little bright. What at first seems like “detailed” high-end eventually becomes tiring. As we continued to listen we also noted a pronounced midrange dip. This tended to make voices sound thin and breathy compared to others in our listening group.

The low end was also lacking, which exacerbated the brightness in the top-end. This combination made me wish I could get inside the crossover and tweak the tweeter level down a bit. That could over come the problem, at the cost of voiding the warranty. The only adjustment on the BX5a is the input level.

I must say that I found these little monitors disappointing. They come from a reputable company and the build quality was very good for the price. Sadly, they were about bottom of the group from a performance perspective.

Notes:

Of the 5 pairs of monitors that we had on-hand only the Behringers provide signal sensing power-on/off. This would be nice to see on more models. It makes it much easier to locate the devices in out-of-the-way places assured that they’ll turn off/on on their own. It greener, too. OTOH, the Behringer monitors occasionally turn themselves off during extended quiet passages of music. Some user control of the on/off switching level is desirable.

All the monitors have XLR and balanced 1/4″ TRS inputs. The KRKs also have unbalanced RCA inputs, but these seemed to hum. Connection to the SB3s was via custom made RCA-to-1/4″ TRS cables.

I think I’ve learned that I don’t really appreciate metal dome tweeters. While very clean and fast they can sound harsh compared to silk domes.

Even the smaller powered monitors seemed better performing that some more common PC speaker systems. They generally provide more, cleaner power as well as better build quality.

We had some minor trouble getting three Squeezeboxes to playback in sync when playing FLAC files from my server. There seems room for improvement in the management of multiple SB3 in sync from the Squeeze Center user interface.

Listening to one item in isolation can leave a positive impression even if the item is in some way flawed. Listening comparatively to two or more items can be much more revealing. I was a little surprised to find how much the gear I was accustomed to using over time actually fell into the back of the group.

This listening session was intended to be informal. We didn’t make any effort to perform double blind tests, or even use an SPL meter to precisely adjust playback levels. Perhaps the next time we undertake such a session we’ll have time to get into that kind of precision.