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SQ-50 Studio monitor
Reproduction so exact that we recommend SQ-50 both for high quality music listening at home, DVD movies in home cinema systems and close field test listening in recording studios. (A number of recoring engineers and professional musicians have already bought the original driver kits for the SQ-50´s.)
Yet, because you build it yourself, the cost is far from what you would expect from a loudspeaker of this quality.

Link to speaker driver kit (HSQ-50e).
Link to speaker drawings.
Customer response (=email from customers).
Questions? send your requests to email@valutronic.se

This is hi-fi at its very best.
A customer in our shop suddenly went all quiet when a tuba started playing on a test recording (the customer was a tuba player himself). When we asked him what was the matter, he said "I can almost tell you what brand it is". He is not alone. Here are some email comments we have received:
Spontaneously I must say that these cabinets sound better than my BWCDM NT7! It is fabulous.
On several occations I have discovered new dimensions in the music I listen to.
Now when everything works and the new 7-channel amplifier is plugged in I have noticed that when listening to DVD concerts you hear sounds from the audience, smalltalk and a lot of other stuff you didn´t notice before. To say the least, a revealingly clear sound. Take the cotton out of your ears and build a pair of boxes. Brilliant.
About the precence in these speakers, it is fantastic. You make a return trip into the throat of the singer... even diffuse sounds are clear, like room-acoustics (both real and added)...
First of all I want to congratulate you on the design of SQ-50. We use them right now for TV/movies and they sound too XXX* good! More and more they are also used for DVD music. Impressing sound... * censured by us
I must also tell you that I listened to one of my orchestra recordings one evening at rather low volume, and suddenly a bass drum is hit (you know the real "Gran Casa", a bass drum about the size of a dog´s hut) which was recorded using Bruel & Kjaer-microphones (A-B non-directional stereo 60cm between the cartridges) and principally unfiltered, wow, what a sound -- the whole bass drum was there!!!
I have just finished building my SQ-50´s with huge success, I hope. Even if I haven´t broken them in yet, they sound amazingly good. Heavy precence and richness of detail.
We are not surprised. Not at all. When we first assembled our first SQ-50´s we almost didn´t believe our ears. Despite the moderate size the bass was among the best we had ever heard. Really deep and clean. Clearly better than most subbass units we had listened to. Had anyone told us before that a 7" driver could go this deep we would not have believed it. But that´s not all. The midragne was also fantastically clean. The SQ-50 is really transparent. You will not be disturbed by colouring, resonances or other distortion. It sounds real, live. Not only in the midragne, but through the whole range from the deepest bass and up. The bass driver goes all the way up to 10 kHz (-3dB), and the tweeter goes down to 800 Hz (-3dB). When the filter divides at 3 kHz none of the drivers work even close to its limits. That is one of the secrets behind the unusually clear and uncoloured sound. What type of music is the SQ-50 best suitable for? None. A real high-class hifi speaker has a neutral reproduction. Everything sounds as it was ment to when the recording was made. The loudspeaker doesn´t add any flavour of its own, and doesn´t substract anything either. So, a tight studio recording stays tight, a live concert sounds live, and fills the room. Harsh synth sounds remain harsh, and a soft voices remain soft. Which is what high fidelity is all about. Not making any changes. In fact, you should avoid speakers that are "perfect for"... a certain type of music. Let´s suppose that a speaker is advertised as perfect for hard rock. Then it probably adds "hardness" to the sound, which makes hard rock extra intensive. But playing soft music and live instruments in such a speaker is a catastrophe. On the other hand, a speaker "suitable for acoustic music and human voice" may have an inferior bass response.

The features that add up making SQ-50 one of the best hifi speakers available:

Bass reproduction:

Clean. When a loudspeaker (even so called quality speakers) is fed a low frequency sinewave, let´s say 40 Hz, the sound that leaves the speaker is usually a mix of 40, 80 and even 160 Hz. Harmonics can be a substantial part of what leaves the speaker.
SQ-50 produces extremely small amounts of harmonics. The bass remains clean. 40 Hz in = 40 Hz out.

Deep. The -3 dB limit is deep down at 32 Hz. We don´t use the -10dB or (even worse) -20 dB figure that some manufacturers use in their advertising. Neither do we refer to DIN, ISO or other standards that tell most people about nothing. When we say 32 Hz it is the - 3dB figure. That means powerful pressure at really low frequencies. Note the comment the recording engineer gave about the Gran Casa drum further up this page. Also, notice that he said that he was playing at "rather low volume". This is one thing that many SQ-50 owners experience. You don´t have to play loud to get deep, solid bass, as you have to with "normal" speakers.
Direct. A bass note that is switched on and off suddenly will not gradually come and go. The bass driver´s cone has perfect damping. This meansthat a bass drum, bass guitar and synth bass can be perfectly separated.

Midrange and treble reproduction:

Very precise, very clean. You hear the music with all it´s details, and the presence is wonderful. A closeup recording really sound close. At the same time the airy feeling of an outdoor concert will fill the room.
Don´t be surprised if you suddenly hear new details in music you have been listening to for years, as several of our customers have written to us about.
The total moving mass of the bass driver is a mere 12.5 grams (0.44 oz), and the air-tight dome in the middle works as a midrange dome.
The tweeter has a refraction damping surface and a 28 mm ultra-light silk dome, driven by a powerful magnet system (using ferrofluid for cooling), capable of 50W RMS. Therefore, a 6dB filter is enough, which in turn gives a soft phase response. The sound is very clean, without the resonances (metal-sound) that some tweeters have.

The column shape is not just an attempt to make the cabinet elegant. It is also for practical reasons: The speaker drivers get higher than tables and chairs, avoiding midrange and treble from being damped by the furniture. The bass pipe is situated far from the drivers, and therefore does not emit a lot of midrange as it would, placed closer to the drivers. At the same time the floor space needed is not much more than an A4 (or Letter) sized piece of paper.

The side walls are slightly longer than the front and back, which makes the cabinet stand on its side walls. As they don´t vibrate vertically, almost no vibrations are transported down into the floor. Therefore the SQ-50´s can be put directly on a wooden floor without resonance problems. If you really want to remove every trace of vibration, just glue strings of felt or soft carpet under the side walls. Spikes are not needed.

The design makes the speaker fairly insensitive to placement. The distance from the back of the speaker to the wall should be at least 2 cm (0.8") or more. That´s all.

Use as home cinema speakers
If you connect your SQ-50´s to your TV or video/DVD via a good amplifier, you will experience a really good cinema sound. Or to be more precise: A better sound than in many cinemas. Both deep bass and pure sound at the same time. (Many cinemas have loud and noisy bass, but the sound is rarely clean.)

When one wants to make a scene extra exciting, subbass pressure is not uncommon. Animated movies are no exceptions. For example: Finding Nemo, the scene with the mines and she submarine, or the trip with the turtles in the East Australian Stream – Don´t let small children watch those scenes alone with the SQ-50´s connected, the sound can be very intimidating.

Many of our customers use SQ-50´s in their home cinema systems, without needing any separate subbass speakers.

Breaking in speakers
...is something you often read about in newsgroups where loudspeakers are discussed. This is how the need for this is described:

The suspensions that hold the membrane in place (often a rubber surround and a suspension made of coated fabric where the coil meets the membrane) should be soft. The rubber surround is usually soft enough from start. However, the fabric often seems to be too stiff in a new driver. The coating binds some of the fibres in the coating together, making it harder, and therefore this part may needs softening. From start the sound can therefore be a little hash, and lacking the deepest parts of the bass range.
However, the fabric will soften while the speaker is playing, the bass gets deeper and any harshness will dissappear.
As the amount of coating can differ som driver to driver, one speaker may even sound a little different from the other when it comes "out of the box". This will however even-out as the fibres of the fabric are loosened from each other.
The period of time this takes differs quite a lot. Some drivers need up to 100 hours or so before they are broken in.
The bass drivers in the HSQ-50 kit (the speaker kit for the SQ-50) only need about 10-20 hours at moderate listening level to get broken in.
To obtain maximum sound quality, don´t try to blow away the coating using maximum level at once. If the fabric is unevenly coated, full power at once may skew the coil and harm it. Take it easy the first hours, and you can enjoy the full quality of these gems for decades.

Important notice. The above comments on sound quality only apply using the original speaker drivers. The SQ-50´s are RVH cabinets, requiring drivers with exactly the right Thiele-Small parameters as well as correct stiffness and interiour damping. Even small deviations can ruin the sound quality.
Therefore, if you happen to have "similar" drivers in the closet... forget them. At least for this cabinet. "Almost" right drivers can result in totally wrong sound. Also, it is not enough to calculate a filter using standard methods. To get Q-damping and phase response correct you have to compensate for how your speaker drivers behave close to the crossover frequency.
On the other hand, the original speaker (and filter) kit is not expensive. In fact, considering the quality you get, it is durt cheap! Just click in this area to read about the HSQ-50 speaker kit, which is exactly what the SQ-50 cabinet was designed for.

With 50W input power the SQ-50 delivers 107 dB (at 1m) which can result in hearing damage within minutes.
Normal listening level for modern music (84 - 90 dB/1m) is obtained at about 0,25-1 W, and "party volume" (about 93-96dB/1m) at 2 - 4 W.
Recommended volume for music mixing in a recording studio is often 90 dB. Lower volume can make the recording engineer miss some details, higher volume will increase distortion in the ears, giving the same result.

The SQ-50 delivers 90 dB at 1 (one) W input power (distance 1m). So you really don´t need a gigantic amplifier.
If you are on a budget this means that you can choose a low power high sound quality amplifier instead of high power low quality one.
If possible, try to choose an amplifier where the power amplifier is made entirely from descrete components (not IC´s). IC power amps are usually designed like operational amplifiers, with low internal bandwidth, giving listening fatigue after a while.