Taming a noisy beast: A new fan for the Kurzweil K2600XS

As part of my return to actual physical synthesizer use, my last investment was into a shiny Kurzweil K2600XS. Yes, the big beast, with seven-octave keyboard and sampling option. And yes, unlike the successor PC3, with sampling option, allowing you to process input live with the sampler, the synthesis options and the KDFX effects.

Now that synthesizer is above any possible discussion or critizism regarding its synthesis power, and also its role as a very efficient and sensitive keyboard; an optimum choice for master keyboard use, and I have been more than happy with it in both regards. However when I powered it on the first time, the noise struck me as very annoying immediately.

Seems that the noise comes from the Kurzweil’s built-in fan, and it’s really rather loud. How loud you ask? I’d answer “louder than a high-powered desktop computer with server harddisks, a Core-i7-920-powered laptop and a noisy city street through the window together”. Checking through some Kurzweil-related forums (e.g. that one), I found that this was a problem of the device in general, not only of mine: people usually advised agains just disconnecting the fan, but reported good experiences with replacing it.

So how to replace it? The good news is that the developments in computer technology – steadily rising heat dissipation due to higher integration and clock speeds, a market for “silent PCs” and finally that odd cult called case-modding – really played into my hands here: opening the web page of a local electronics store, I found fans with a specified sonic rating as low as 10dB. Now 10dB, in case you wonder, is roughly three times as loud as something you’re just barely able to hear – in an anechoic chamber. It’s also about 1/4th of the noise level of a very quiet room, or roughly the same of someone breathing very quietly.  All in all, it’s quiet enough (check here for some unreferenced examples of noise levels, and keep in mind that every 6dB more means twice as loud, so e.g. 24dB more is sixteen times (!) as loud).

One guy in the aforementioned forum cited a form factor of 80x80x25mm for the Kurz, claiming that “a height of 30mm should also fit in”. So I went to the store and got an 80x80x25mm fan specified at 10dB and at a price of €9.90. The name: “Noiseblocker Black Silent Fan Ultraquiet”.

The official Kurzweil specification from the “harddisc installation kit” provided just the information I needed to take the thing apart. I decided to place it on my bed (to be able to flip over things at will without having to worry getting scratches on the display or damage to levers or wheels).

Removing the fan requires removing the power supply electronics first, which is done via four Philips #2 screws (note that you may need some kind of extension when using a powered screwdriver, as two of the screws are situated next to the heat sinks), then the fan itself is removed with four more screws and disconnected from the power supply via a small jack.

Now measuring the dimensions of the original fan, I found that it’s actually 90x90x25mm. Now is that a problem?

Now the fan lies below roughly 1/3 of the length of the heat sink, sucking away the hot air from there. As heat sinks, by design, have a very good heat conductivity, reducing the surface “sucked onto” by 1/9th shouldn’t be a problem here. Also, as the curvature of the fan is actually a little steeper for the smaller radius, it’s also ensured that the smaller fan fits well with the grille below.

The only point of concern may be that you’re only able to use one of the four screws to attach the fan to the flange on the K2600s case. This can be worked around simply by using a sufficiently thick piece of sheet metal (e.g. 2mm or above) of about 100mm in length, drilling two holes in it at 90mm distance and then use that to fix the fan in place (that’s what I did).

Now putting the fan in place is one thing, attaching it electrically another one.

Most of today’s fans have three wires opposed to the two of the Kurzweil’s fan: the third wire is used for regulating the fan speed. Fortunately, simply keeping that one unconnected works pretty fine, making the fan run at full revs all the time (which is just what the old model did, only at much higher noise level). Unfortunately, the jacks don’t match, and also the crimped wire ends don’t match the jack.

I helped myself by simply cutting open the wires of both fans and quickly soldering the black and red wires of the new fan to the corresponding wires of the old jack.

Reassembling the thing and putting the K2600 back together was again a breeze, also thanks to the very helpful instructions in that specification I mentioned before.

Now for the big test: how does it sound? Turning it on, I simply notice: no noise. I quickly turned off the computer, listened again: no noise! I put my hand below the ventilation grille in disbelief for fear of having mixed up the connection of the new fan – yes, it’s blowing all right.

So for a quick summary: If you happen to own a Kurzweil K2600, have ever been unhappy with the noise of the fan, and know how to at least open some screws and solder two wires together: get yourself a fitting (again: 90x90x25mm) low-noise fan (as I mentioned, they’re available with specs down to 10dB, and invest roughly one hour for continued years of silent bliss!

11 thoughts on “Taming a noisy beast: A new fan for the Kurzweil K2600XS

  1. You may have replaced a fan, but did you match the original fan’s ability to move air and dissipate heat? It’d be important to know what CFM rating the original fan had, and how many CFM your replacement fan was moving at whatever rpm it ended up spinning after being rigged.

  2. Thanks, Josh, for that valuabel comment. Although I did make the considerations you mentioned, I didn’t treat this in the article, and here’s why:
    When choosing my fan, I found that the fans I was looking at (meaning high-performance case-modding variants) were considerably above the ratings of the standard cheap off-the-shelf components resembling the one installed in the Kurz.
    While I didn’t have access to the specs of the fan in the Kurz (a rather aged low-price design), I went with the rationale that the newer, performance-optimized component would out-qualify the original fan, especially as in my situation, it’s running in a non-controlled (i.e. always at full revs) fashion.

    To validate by inspection, I made a comparison after installation, and it *felt* like it was in fact moving more air by an order of magnitude.

    So, while I feel safe myself (and that with a professional background of mechatronic equipment operating under extreme environmental conditions), you’re right that the right way would have been to first analyze (or research) the specs of the original fan and then select accordingly.

  3. Thanks for making this article and other peoples comments too.
    I just replaced the fan of my old Kurzweil K2000RS with a Noctua NF-B9 that I already had from an old computer but didn’t use anymore. The Noctura NF-B9 is 92x92x25 and its fits perfectly to wholes of the K2000RS, so no adapter needed here. The Noctura NF-B9 has three speeds (with adapter) and I use the one that causes to lowest noise level which is not completely noise free but almost, and there is still lots of airflow, so K2000RS doesn’t get too warm. I hate fan noise, so I have also disconnected the internal scsi harddrive of my K2000RS, because I use the computer for samples anyway, so I just want to my Kurzweil as a synthesizer and not a sampler. The harddrive gets warm and even though I can park the harddrive in Kurzweil so it is noise free I don’t think its worth the trouble having to park the harddrive all the time, now that I can do my sampling into my computer instead using Native Instruments Kontakt and my DAW.
    When I bought my first Kurzweil K2000R back in 1994 (and worked full time for a whole year in order to save up enough money to buy it) I tried to fix the fan noise with a temperature controlling device between the motherboard and the fan, but the K2000R got hot in no time, so it got noisy after about 15 minutes anyway, so no improvement back then, but the modern noise less fans really do an improvement. My computer is completely noise free and I expect that by adding some polystyrene material behind the K2000R it will be both noise free and still well cooled down for use for many years to come.

  4. Important to note, the fan should blow in NOT out.
    I can’t find 2 pin connectors so I may have to use your idea of directly soldering the fan to the power supply cable.

  5. took me a while to find the right one… (caused by revision update by the manufacturer)
    in summary:

    old: Noctua NF-B9
    new: Noctua NF-A9 FLX
    both have the same dimensions of 92x92x25mm, punch 82,5×82,5 mm
    so they will fit in all Kurzweil 2000, 2500 and 2600 X,XS,R,XR (if I’m correct)

    instead of soldering i would recommend “dual channel T connector for low voltage”
    Kurzweil technicians did it this way (with single channel ones)

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