Comparative tests of ~$50 stereo pairs

Does anyone need the classical stereo pair in the era of all-out multichannel audio? As our poll showed, the percentage of potential consumers of this type of produce is such that it is still early to disregard. Anyway, I am taking the risk to presume the consumption will not go up, especially in the multimedia sector where there is immense quantity of stereo pairs.

Today's comparative tests preceded a strict preliminary selection. I intentionally won't mention any model names which have not been included in our final list. The technical remarks have already been sent to the interested parties, and we'll certainly inform you if the modernization of "outcasts" has been carried out and is successful.

There were such trademarks which promised to present their acoustics "as soon as possible" but due to unknown reasons they fell into a prolonged hibernation.

So, there goes the list of participant models which passed the selective test by Ferra.ru:

Solo-1 mk2 by Microlab Technology Co. Ltd. (Russian web site www.microlab-speaker.ru).

Microlab Pro-1 (again www.microlab-speaker.ru).

Defender SPK710 Mercury 40A (www.defender.ru).

Sven MA-230 (www.sven.ru).

AVE D-60 (the Russian web site has just appeared: www.ave.ru).

Note that the above mentioned model by Sven lags a bit behind other finalists at both specific parameters and the price. Nevertheless, some qualities of Sven MA-230 allowed it competing on par with definitely stronger contenders. We can discuss if it is justified to relate Sven MA-230 to our «almost Hi-Fi first group" of stereo pairs, however the technical specifications declared by the manufacturer leaves no doubt regarding that. If only they showed the operating frequency band is, e.g. 120-16,000 Hz, then it would be different. But, as they say, "If you have called yourself a milk mushroom - go into the basket!"

Packaging and package bundle

The package bundles of Microlab Pro and Sven models, apart from the typically computer "inter-unit kit" (a mini-jack for 2 "tulip" connectors), there is also a cable for plugging in to a household DVD-player (2 RCA by 2 RCA, i.e. all «tulips»). The cable length is standard: about 1 meter.

Unlike Solo1, all the other models were bundled with an acoustic cable with a copper core in a trendy transparent shielding. It's a pity the cable is getting thicker, with the length turning shorter (at best, it is a bit more than 2 meters).

Specifications

* - irregularity of the frequency response curve not specified by the manufacturer

Don't worry about the declared range of operating frequencies in Defender 40A – it is simply the most truthful. Basses are OK in this "40A"!

Of course, a decently sounding active acoustics at $50 must have been manufactured only in China.

Technical solutions

Today, "first rank" stereo pairs have all acquired separating filters without adding to the price at all. Evident progress! But the law of Nature says: if a quantity is added somewhere, the same quantity is subtracted elsewhere. As I already noted, inexpensive filters do a sure job of fixing the response in the frequency area but make it worse in the temporal part (the pulse response of the acoustic system suffers). As a result of whatever discrepancies, there arise problems with phasing the right-hand and left-hand speakers.

All multimedia stereo systems which we've had the chance to test suffer from poor processing of the scene depth (as compared to the truly Hi-Fi equipment). And that is no wonder! To reveal the reconstructed sound space into the depth, a very distinct phasing-in of both the stereo speakers and amplification stages is required, and within a very wide frequency range. But that costs a lot - much more than $50.. And even more than $500, I'm afraid.

Clearly, the separation filters for the speakers at $50 are made, softly speaking, on a tradeoff basis. First of all, the response in the frequency range has to be corrected to make the sound richer and pleasant. The precision of reconstructing the stereo effects is the other thing.

Manufacturers of Hi-Fi acoustics all "tune" the sounding of their systems as if arching the frequency response curve at some specific frequencies. For instance, some worldwide respectable companies taking account of the tastes/passions of buyers are inclined to accentuate basses and the highest frequencies (that's where the term "American sound" comes from). Indeed, the sounding proves far not be like that in a studio or on a monitor. Well, what's so big about that? Which positions do you set the timbres to on popular household stereo equipment while listening to music? I bet it is HF set to the maximum, with the LF set to almost the maximum. At the low volume, you also switch on the tone compensation. Why so? You don't complain about the ear and taste... This is because only very expensive Hi-Fi (is it Hi-End already?) equipment is able sounding a real music without tumbling down over the edges of a frequency range. Moreover, because of the direction effect upon deflection from the acoustic axis the tumbling down at high frequencies is inevitable, and if your listening area is not restricted to a tiny spot, then you should take care of some margin at the high frequencies.

Another way of improving the acoustics, of which multimedia audio manufacturers do not forget, is application of advanced dynamic heads and domes of ad hoc properties. Among our finalists, various speakers have been selected: ones with pulp-and-paper dome, with a dome of glass fabric, with plastic diaphragm etc. All the bass speakers have a long-stroke hanger, i.e. are able processing depth lows with the relatively small size of the dome. By the way, the most flexible hanger system together with the centering ring was found in the white cellulose bass speaker of AVE D-60 model. At the same time, as never before multimedia acoustics manufacturers are being tempted by newly-fledged producers of speakers which are growing like mushrooms all over China. Time will tell how good the new speakers having a tempting price will prove.

It seems like the trend of bringing the whole amplification part into a separate external unit is beginning to pick up. It's not by accident that the firstling - Microlab Pro1 - found itself in the list of finalists, although engineers of the renowned company have had to sacrifice with something (is it about the manufacturing technology?) to fit inside the $50.

Measurements

Like in /2/, we measured the frequency response curve using two different methods. The sound volume of the active acoustic system was set to 50%, the timbres to 12 o'clock, that is, to the center of the imaginary scale. The test signals containing both pure tones and white noise were applied at the peak amplitude - 10 dBU. A special measuring microphone with practically linear frequency response within 20 Hz to 20 KHz was used. The microphone amplifier: +0.8/-0.1 dB 20 Hz/20 KHz, +10–50 dB, maximum level –12 dBV, THD+N -95 dB, input resistance 330 Ohm. The distance from the speaker to the microphone was 1 meter, and the distance from the walls was also 1 meter. The tests were performed in a typical household premises of about 30 cubic meters, middle reverberation, without muting.

Of course, the effect of involved premises affected the measurement of frequency response curve, especially at low frequencies. Therefore, we can speak about the relative - not absolute - frequency response which can be produced in only an echoless (phonometering) chamber. In fact, the relative frequency response is enough for a comparative test because external conditions for various acoustic systems (among the tested) are identical.

I am not bringing in the frequency response curve graphs produced with the impulse method to as not to bore the readers. I'd rather say that correlation with the "running sine" when smoothing 1/2 of the octave is good enough.

So, let's look at the results of measurements produced with the running sine method using the well-known RMAA program. I intentionally use this easily available program so that everyone could compare the frequency response curves measured by them versus those provided by us (but don't forget: during calculations, the microphone should have a linear or corrected to the linear frequency response!).

It is distinctly seen that at low frequencies the shape of the frequency response curve is congruous in all the finalists. Only MicroLab Pro1 with its marked peak at about 40 Hz gets out of the common groove. The response at bass frequencies will be different in some peculiar premises, but if your dwelling is a regular flat with 2.5 m height to the ceiling, then the difference can be neglected. The most pleasant bass should be expected from Defender 40A: maximum by 70 Hz better than the maximum at 100 Hz. The most dry bass will be in Sven 230 because is frequency balance is strongly biased to the medium and high frequencies.

At the medium frequency, the best sounding will be Microlab Pro1 and Defender 40A. But the tumbling down in Solo1-mk2 will please the ear for many because in plying real music medium frequencies will start actively coming in. The bulge within 1 to 3 KHz in Sven 230 is good to speech only.

In the high frequencies area, the most ideal response is observed in Defender 40A (the high-quality tweeter makes itself felt). Alas - in the MicroLab models being tested the tumble-down starts with ~15KHz (to all appearances, the tweeter is the same). The "lift" at the high frequencies in Solo1-mk2 is definitely caused by the frequency "amendment" (the intricately built HF-timbre). At frequencies higher than 10 KHz, Sven 230 is agonizing (a tradeoff for cheap tweeter): there will be too much noise, and not all will like it.

The AVE D-60 model is a novelty on the Russian market, which merits a separate mention. What immediately catches the eyes is the most powerful splash at the low frequencies, especially within 60 to 70 Hz. Oooops! You won't get bored with bass like that. There are even two humps seen (like camel's?): one at 1.5 KHz, the other at 7 KHz. The former will make itself felt by accentuating specific sounds, whereas the latter hump will most likely not be perceived by the human ear with its sensitivity in the area 7 KHz. Unfortunately, as was found out, the timbre adjustment will not help correct the tumble-down above 10 KHz. The hollow within 150 to 800 Hz will favorably affect the adaptability of speakers to the conditions of a location, in particular on the table or shelving.

Expert listening

We used an active stereo acoustic system as the "reference":

Defender SPK-720 – first among the "$50" group (> $60);

old Microlab Solo-1 (used to be ~ $50);

Hi-Fi passive stereo pair Monitor Audio Bronze B2 (> $230), with the the receiver Pioneer 514 (> $220) in the direct stereo mode.

Activated sound sources:

multichannel sound card Creative Audigy 2;

typical portable МР3-player plugged via the earphones output;

household DVD-player Pioneer 565-A with truly high-class DAC (Burr Brown DSD1791: 24 bit 192 kHz, Dynamic Range 113 dB).

Recently, we added the CD «Audio-Doctor» (www.salonav.com) to our test material. It is a very useful disk who I do recommend to acquire (the magazine issue to which the disk was enclosed was sold out in no time). The only suggestion to the creators (because apart from that you have to get a test disk for multichannel audio) - do not forget about the energy-rich music, better with dense ornate bass.

The listening was performed by means of locating the tested acoustic systems on a 2-2.5 meters stereo base. The speakers were placed on supports so that the HF-speaker be at the level of ears (keeping such acoustics at the desktop close to the monitor is not the best solution in all respects!).

What I liked is that contenders for the first prize did not have to turn the timbre to the full. Personally, when listening I set the HF for no more than 1 hour, and not to the neutral middle (for Microlab Solo1 mk2). At the same time, the LF timbre was set at that for no more than 3 hours. A very good sign!

The frequency balance of our finalists (perhaps, except Sven 230) will successfully compete with entry-level Hi-Fi acoustics which is several times as expensive.

Defender 40A, an uncomely stereo pair at first look, performed surprisingly superb - it did a great job of handling both the high-amplitude output of the DVD-player and the weak output to the earphones of the MP3-player. Its stylistical simplicity is of special mention. With this Defender, and at Solo1-mk2, you can enjoy music of any style.

The punch of modernized Solo1-mk2 offers a bit less distinct attack as compared to the three-year-old progenitor Solo1. Percussion pulses are evidently damped due to the increased dome area of the LF/MF speaker.

To my personal perception, I didn't like it the way timbres in Microlab Pro-1 work. The margin is more than enough, but once you depart from the neutral, some rough sounds turn up (is distortion going up?) Things are somehow better with the tone compensation (the loudness button).

During tests of LF-percussion, the bass speakers in AVE D-60 were literally jumping out of the casing. At the same time, they were not muttering or buzzing, and the bass was so soft that even some floor acoustic systems can't boast it. That's what a successful speaker combined with a thoroughly selected phase inverter mean. Among the cons: the input is reluctant to deal with high-amplitude signal sources like Pioneer 565A. The acoustical power of AVE D-60 is not giant of course, but deserves respect. As a tradeoff, the over-tuned sounding resulted in nonlinear rise of distortion as the volume goes up.

On the whole, all the finalists have demonstrated a reasonable power. A perfect match for home, family, movies, and games! The margin for undistorted power is a bit too little for a full-featured sounding of complex symphony music, and you won't get along much with it at fast dancing too, - but these are all inevitable tradeoffs for a low price.

Improvement suggestion

Prior to the tests, I assumed that there came the turn of a demise for multimedia stereo pairs, even those of the highest quality. But - no! The price is really good! The good price combined with quite decent sound (even by the standards of entry-level Hi-Fi) will still provide impressive sales volumes in Russia. Alas, any further improvement in the quality of sound of the design through industrial way will essentially affect the price. And that will kill the idea to the root.

Therefore, it is simpler and cheaper to introduce amendments on your own, e.g.upholstering the housing sides with self-gluing films of desired texture color.

The only thing what you miss while plugging to a household CD/DVD-player is a hard-wired (say, 5 meters long) remote control with the only volume control resistance.

Conclusion

By the sound quality, first-rank "hi-fi" multimedia stereo pairs (priced about $50) have come closest to one another. I suspect no more than 5-10% of consumers are able telling the differences apart, and only those who would prefer a natural Hi-Fi at about $1000. Therefore, the major criteria of selection will be the nicety-design, functionality, and ease of use!

If we compare them only by the attraction of sound, the first-second places are shared between Microlab «Solo 1 mk-2» and Defender 40A. . In terms of Hi-Fi requirements, the most genuine sound is demonstrated by Defender, but Microlab is appealing for its complex approach.

AVE D-60 – the whistle-blower – did not interfere with the row for the first prize mainly because of its plastic HF-head. Even with this tweeter, D-60 sounds attractively! Moreover, D-60 can be used as a combo for electric guitars (with echo effect) due to its microphone input able withstanding high-ohm load. So, for now you can't find anything better for karaoke at $50. If the manufacturer replaces the tweeter soon, then competitors will have a hard time!

As was assumed, SVEN MA-230 demonstrated a relatively good showing at merely medium frequencies. By the way, in terms of the minimized distortion this is the cheapest acoustics among the "right". The exquisite and elegant МА-320 can be recommended for sounding speech (for music - you can't get by without a subwoofer).

The sound of newly-fledged Microlab Pro-1 has not produce any sheer delight at all: evidently, the model hasn't matched the expectations and foretastes. Anyway, it has all as should be: the velvet bass (more balanced than that of Pro-3), and silky high frequencies. Most importantly, albeit tuned, the medium frequencies are not shrewd to the sensitive ear. Life is real: you won't squeeze out more at $50.

But in terms of ease of use and functionality, Microlab Pro-1 is an undisputable leader.