DWPG.Com - Review, Logitech Z-540 computer speakers
By: Sverre Sjøthun

Introduction

Computer speakers are a contradiction in terms – they are extremely small, yet the manufacturers promise 400W heart pounding bass, crystal clear treble and fantastic midrange and what not. Here’s a keyword -- Physics. There is no way you can get all that from some 10x10x10cm plastic enclosures and an 8”sub-woofer. To get all that, you need weight and volume -- it’s not a coincidence that great tenors, almost without exception are, politically correct speaking, “big men”. You simply need weight and volume to produce.

Size versus sound quality, the Logitech satellite on top of my right speaker

Size versus sound quality, the Logitech satellite on top of my right speaker


By now, you probably have a feeling that I’m pretty passionate about sound, and that is correct. Sound, and more specifically high-end stereo equipment is my other vice. To give you an idea, the ScanSpeak D2905/9700 tweeters in my front speakers cost 3 times the Z-540 each. Each speaker weighs in at 55Kg. I’m not a fanatic, but you may call me a demanding listener.


Some thoughts and facts about sound

But before we return to the initial subject, the Logitech Z-540, I’d like to share some thoughts and facts about sound. Like I said, to get “proper” sound, you need volume and weight. Generally, the volume in the enclosure will make it possible for the woofer to reproduce the super-low frequencies, whilst the weight, in combination with very specific materials, will lower the resonance frequency in the enclosure.

Ideally, it’s only the driver that’s supposed to make the sound, but materials, enclosure design and damping of the enclosure plays a big role in what it sounds like in the end. With poor materials, little or no damping material and poorly designed enclosures, stationary waves and resonance occur, and it sounds dreadful.

There are many means to combat these problems, but the most common are an enclosure made of MDF(Medium Density Fibreboard) or NRFB(Non Resonant Fibreboard), bracing the inside of the enclosure, proper damping material and asymmetric design.

The adding of damping panels to the inside of the enclosure walls, usually in the form of bituminous pads, does much to reduce resonance hangover, but not much to reduce panel flexing while still being excited by the driver. The flexing is non-linear and the distorted harmonic structure of the total output from the speaker changes the timbre of the sound. Stiffening of the panels reduces the amplitude of flexing and this can be done by a combination of increasing the panel thickness and bracing.

Bracing taken to the extreme by Bowers&Wilkins

Bracing taken to the extreme by Bowers&Wilkins


You can get a pretty good idea about the enclosure quality by simply knocking on it – if it sounds hollow it’s usually not very spectacular. What you want is a dense, tight knocking sound.

The driver units obviously also plays a major role. One driver can not produce every frequency from 20Hz to 20KHz, which is what the human ear can perceive. Again, the keyword is physics. You need a big mass to produce low bass because big mass equals lower resonance frequency. And while adding mass to a driver, you make it slower, so you cannot reproduce the high frequencies. At this point, it doesn’t take much brain activity to figure out that what we need is a tweeter, or at least a midrange driver.

Seas Excel magnesium high-end woofer

Seas Excel magnesium high-end woofer


Now that we have two drivers in our system, we cannot let both play the same signal, as the woofer would play blurry and distorted midrange and the tweeter might end up being fried because of the high-powered midrange and bass signals. We need a crossover to distribute the correct signals to each of the units.

A cheap, very simple yet effective crossover consists of a capacitor and a coil – the capacitor act as a high-pass filter and is hooked up to the tweeter and the coil act as a low-pass filter and is hooked up to the woofer. This crossover will dampen the signal by 12dB per octave, and is a so-called 1. order crossover.

Finally, output is never going to get better than the input, which brings me to the amplifier. Next time you see a small 5Kg amplifier that the manufacturer claims to be 2x300W, laugh at it, cause it ain’t true. It might be true in a given period of time, in a certain frequency range, but it’s true RMS that counts -- true RMS at 8 ohm is the de-facto standard for measuring output power.

ZAPsolute Mk4, a 50W amplifier with a 650W PSU

ZAPsolute Mk4, a 50W amplifier with a 650W PSU


To get even close, you need a transformer, a PSU, that’s capable of delivering 600W minimum. With some yields we’re talking close to 8-900W, and a 900V/A toroidal core transformer tends to weigh 10-15Kg, which explains why good amplifiers easily hit 20Kg or more.


Technical details and mounting

What you end up with is compromises, technical solutions to fool you, psychoacoustic effects and yet another compromise. The Logitech Z-540 is a 4.1 surround setup (4 speakers plus 1 subwoofer), and seems reasonably good at first glance -- that is, after unpacking and unwrapping every single cable, plug and speaker from layers of plastic. They could’ve used half the plastic and still have had plenty protection of the parts.

But let’s take a look what’s included in this set:

- 4 satellite speakers, 110 x 850 x 130 (LxWxH) including stands
- 1 subwoofer 250 x 230 x 230 (LxWxH), 8” driver
- A variety of cables
- User manual

Technical details:

- Total power output: 40 watts RMS; Subwoofer: 20 watts RMS, Satellites: 20 watts RMS (4 x 5 W)
- System frequency response: 35 Hz - 20 kHz
- Signal-to-noise ratio: > 75 dB
- Input impedance: > 5,500 ohms
- Power switch on satellite
- Volume, fading and surround control on satellite
- Independent bass level control on subwoofer

Thankfully Logitech has been relatively conservative when it comes to specify the power ratings. This is a good sign. Another good sign is when I opened the sub, it seems as they had used MDF, and not standard fiber board as I would've thought. Unfortunately, the cords were so incredibly short, I was unable to take a good shot from the inside of the enclosure

The front of the sub with protecting grill

The front of the sub with protecting grill

The back of the subwoofer with its levelcontrol and input/outputs

The back of the subwoofer with its levelcontrol and input/outputs


Mounting the speakers was a piece of cake with everything colour coded or marked with a text label. To get the most out of your speakers, it’s important to place them correctly. A rule of thumb is to place them with the same distance from the listening position as it is from speaker to speaker, or slightly bigger distance from the listening position, in my case 90cm all three ways.

This diagram show you the correct placing of the speakers

This diagram show you the correct placing of the speakers


Some speakers also need to be angled towards the listening position, and these do. Not much, just a little. This is due to lower off-axis frequency response. The more off-axis you go, the worse frequency response you get. Another important thing to remember is that the satellites should have the same height. Both the distance from each speaker and the height is to ensure that phase errors don’t occur, which again is crucial to obtain the best possible sound. The subwoofer can be placed pretty much where you want, as the human ear is not very good at determining the direction of low frequencies. Mine ended up under my desk.


The testing

These speakers were tested using the onboard C-media chip on the Asus A7V333 motherboard. Unfortunately, this has only 2 channels, so I was unable to test the true potential in surround. For those of you that have 4 channels or more, see it as an “added bonus”.

The satellites placed on the desk

The satellites placed on the desk


The first song I played was “Norah Jones – Seven years”. The sound of the whole album “Come away with me” is amazing, lots of acoustic instruments and is very demanding. The human voice is extremely hard to reproduce correctly, and the same goes for classic and steel string guitars.

To tell you the truth, I was blown away – I would never expect a cheap set like this play so good on what’s so demanding. What probably made me most surprised were the roomy feeling, correct timing and relatively speaking great treble. It was almost like sitting in a small club with Norah Jones singing only a few feet away from you. The midrange, however, sounds a bit dull and not very articulated.

Next song up was the title track sampled from the BB King & Eric Clapton album “Riding with the King”. For those of you that don’t know the album, it’s blues. The song has a nice room, quite heavy and slow bass and of course electrical guitars and solos. The high-pitched solos tend to sound dreadful on poor systems, due to distortion in the driver.

Yet again, I was mighty surprised at how well it handled it. The solo was not very hard on the ears and both BB King and Eric Clapton “were standing where they were supposed”. The bass was nice and dry, but it did have a tendency to not stop when it was supposed to, causing it to sound a bit “sloppy”. It doesn’t take much power to make a cone start moving, but it takes a lot to make it stop moving, i.e. timing, and the lack of power in the amplifier is causing this.

Time has come to put these speakers through some torture, and what’s better than Death Metal. Yep, you heard me right, Death Metal. Death Metal has an extremely dense sound, it’s almost like a huge concrete wall of sound, and if the speakers can’t differentiate the different instruments, it’ll sound like white noise at full volume. Not very nice.

I chose “Dimmu Borgir – Kings of the Carnival Creation” from their album “Puritanical Euphoric Misanthropia”, which I dare to say is about the best there is in this genre. As earlier, most things where they were supposed to be, and the subwoofer didn’t have too much problems keeping up with the insane speed of Nicholas’ arms and feet as he was pounding away on his drums and cymbals. It still miss the timing a bit, and the guitar tends to be a bit hard on my ears, but still pretty amazing good.

Last test was to see how low the woofer could go. This is where Hard House comes in handy, and more specifically "Signum – What ya got 4 me". I just couldn’t help my self -- this put a big grin all over my face. However, it was not able to reproduce the lowest frequencies, you just got a hint of what’s really there. As Logitech has specified in the documentation, the bandwidth is 35 Hz - 20 kHz, and it may be true, but not at +/- 3dB which is the de-facto standard of measuring audio bandwidth. My estimate, an educated guess, is not lower than 45Hz, and most certainly not lower than 40Hz.


Conclusion

Steak for the price of a hot dog?

Yes, that’s the feeling I have after having used them for about a week. To me it was important when reviewing this set to remember that this is not a $8000 stereo, but a $80 speaker set. In my opinion, it’s worth every single penny, even if you don’t use the rear speakers. Of course, if your soundcard or motherboard supports 4.1 surround, it’s even more value added.

These speakers kept impressing me on whatever I threw on them, be it any sort of music, gaming or a DVD movie. I have only a few minor complaints – the power-on diode is bright blue and gives a very sharp glare right in my eyes, and is not very comfortable. If you do not angle the satellites inwards to the listening position, you do not have these problems, but you miss the intense stereo perspective this gives you.

The glaring blue power on LED

The glaring blue power on LED


My second complaint is the control buttons. Even if they are ever so stylish, they are small, coned and hard to operate easily. Making them a bit bigger, easier to turn or better grip will easily remedy this. My third, and last, complaint is the level control on the subwoofer. In my opinion, there is too much bass, and I had to compensate for that in WinAmp. This might be a way of compensating for lack of deep bass, but your music should not “drown” in bass booming. This is of course a personal preference, just as I can’t stand Cerwin Vega speakers.

The coned buttons

The coned buttons


Based on this, my ratings are as follows:

Pros

- Great value
- Stylish design
- Great sound
- Handeled everything thrown at it

Cons

- Power LED too bright
- Controlbuttons hard to operate
- Too much bass with no way to decrease the level.

Sverre Sjøthun

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