My guess would be apple is sucking them all up at the moment for the G5. Purely a shoot-from-the-hip guess.

On a personal note, I am shocked and amazed to find such a competent and informative board here. I have many MANY questions, and must admit, I am more than slightly intimidated by the level of expertise here. (Like the various engineers from the companies designing this stuff, Yikes!)

I too, an quite interested in this product.

Sorry for lack of clarity. I just meant that cooling-masters has no NDA or wait on product testing/announcements presumably because they got their DDC directly from Laing. I thought in one of the previous articles they mentioned "Mr. Laing"; maybe my reference to that was too obscure.

It's not "Mr. Laing" but an employee of Laing Germany. It's a good contact, but rosco could tell you more about it. ;)

I know what 1046 and 1048 Eheim pumps sound like - which made the pump sound recording in that cooling-masters article very useful.
Bill, you mentioned that it was only "pretty quiet" (sorry - might be misquoting here). Did that mean "not dead silent"? - Is this recording representative of the sample(s) you've had your hands on?
Anyway, if this recording isn't misleading I definitely want one. :)
Bob

that recording is not to my taste at all
which D4 is that, the original ? (should explain why we did not wish to sell it)
- the present ones don't make that noise, different pitch and lower volume
the DDC was/is not isolated (something is resonating)
no exp with those Eheim models

jd - your wakeup call here

any 3600 RPM pump not isolated from the chassis will 'buzz', and no high head pump of this type can be "dead silent"; but appropriately isolated they can be inaudible
also in a fanless case in a 20dBA environment ?? - no data but doubtful

Already explained that in mails but I do it again.
The D4 comes from DangerDen, please stop to compare it each time with Swiftech products as a unique design because it's not. Dan said me that it was a little different from yours (it's a muffled one he said too but I don't have both to compare them). But now, he said he will receive the same as Swiftech. Mine has a MFR of 08/2004. Here is his explanation from mail :
Nothing is resonating in the foam box because pumps are put on another piece of foam very soft to avoir all vibrations. If you had read carefully you should see that I introduced a restriction in the discharge tubing (I pinch it slowly) to go to 0 flowrate and then I relax it to go again to the "max" flowrate with almost no restriction (just a tubing). So it's normal that the noise grows up because DC pumps spin faster under high restriction (~3900tr/min), it's not a resonation sound with lower frequency... DDC is very quiet like Eheim and almost inaudible in a case with appropriate considerations !
Pay attention to the speakers volume, it must be very low to join the reality because pumps are very quiet, except D4. No dB measurements sorry, it requires good materia and technicl to capture such low sounds and I don't have any.

Bill, is it the methodology of the recording you don't like?
Without the $$$ for an anechoic chamber, ultra sensitive mike(s) and spectrum analyzer this seemed like a very sane way to come up with a comparison. I would guess that most folks who are water cooling PCs, and who are interested in quiet operation, have at least one 1046 or 1048 in their history. The 1046s in particular are nearly inaudible. Yes, they shake a bit, and can resonate a case, but Roscal made an effort to eliminate/control this. Yes, there were a number of things not controlled for ( I can think of: differing weight/base area ratios - so differing vibration isolation; differing axes of rotation - so possible different "lobes" of high/low noise emanating - issue if microphone directionally sensitive; microphone (or recording equip't) response not "flat" across frequency ranges at low levels; possible transmission of sound from the inlet/outlet hoses - would have used the softest silicone I could have found) but they are all fairly minor. But my major question was, indeed, around the D4. I've never herd one, so I'm going on indirect evidence. You had mentioned that they were around 30dB and there isn't enough difference in volume between the 1046 and D4 to account for a 7 to 10 dB difference in sound levels - so maybe some sort of automatic gain was on (?) making this recording inappropriate for judging relative sound levels.

Roscal - thanks for going to all this work! You've got me working on my very rusty (haven't used it for 30+ years except to order beers on some carribean islands) French - and it wasn't very good to start with :) And thanks for including a link to procooling. If nothing else you're making folks here a bit more sensitive to what non-English speaking folks go through trying to be part of this community...

Thanks for the clarification Roscal
FYI all Laing pumps with a manufacture date of 7/04 or later are the same
I followed your procedure and set the volume of the D4 to a level that I thought was representative,
and under the listening conditions the other 3 pumps were inaudible

so what were the "listening conditions" ?
the 'source' was a pair of stereo desktop speakers each with a 4" speaker + a tweeter
my wife's mini tower is on the desktop with a single fan in the psu, making too much noise apparently

re the D4, again, it has a spike at 4k Hz - which is a somewhat 'high' frequency and easily recognized once heard
Roscal's recording seems to have dropped this pitch somewhat (??), or my speakers ??

and yes bk, like fans the sound emanation is not uniform; sides about the same while the top and bottom are each different
while a defined procedure will address some of this, it is the 'calibration' of the listening environment that is troublesome
- and the ratty sound coming out of 2" speakers, or 4" + tweeters, etc. etc.

if something is better than nothing then, as JoeK would say, its all good
I have reservations

Is there any indication from where the sound is coming from? Is it an mechanical sound or does it have something to do with the shape of the impellor?

Sound comes from the movement produced by the current shape in coils. In a D4, current is sent with a rectangular signal (simple electronic) whereas in the DDC the current is sinusoidal -> no more brutal transitions creating vibrations, it's a smoother rotation but electronics is more complex. Mechanical design in a DDC is the same of a D4, just a change of electronics (to simplify).

I put the DDC impeller in the D4 to test that fact but the noise is almost the same ->no impeller problem.

Pitch seems ok:

1046:
http://img94.exs.cx/img94/8858/1046.gif

D4
http://img81.exs.cx/img81/7694/d13.gif

Headset mic (I think it was?) + 4" desktop speakers may not (indeed) be optimal combo for reproducing 50Hz hum :D

Is it active voltage control by stepping the power transistors or just passive filtering with something like an LC filter?

Nice lolito, 50Hz harmonics are clear (~3000tr/min for France).

[mode fr :D]
C'est quoi ton soft? Goldwave gérait pas ca... J'ai bien envie d'updater le dossier avec ca.
[/mode]

Thx

Sorry I don't know ;)

Roscal, I used Adobe Audition (ex CoolEdit Pro)
no problemo si tu veux faire un copier/coller (même si jai fait ça un peu Ã* l'arrache, comme on dit :D )

C'est bon j'ai trouvé un freeware qui fait les FFT , ca rend très bien :) -> http://audacity.sourceforge.net/windows.php
Regarde la 1048 le fondamental est a 100Hz par rapport au 50 de la 1046, pourtant elle tourne a la même vitesse d'après leur moteur (3000 tr/min), bizarre que la fréq soit exactement le double, je vais réfléchir Ã* ca.

Bizarre...
1048:

http://img20.exs.cx/img20/2951/2705.gif

As Roscal says, no 50HZ fundamental for this one?!

Also note the cutoff at 7k or so (same for the other pumps) this is due to the mic and/or codec, and will have an effect on the perceived noise - of the D4 in particular

DDC:

http://img48.exs.cx/img48/2576/ddc.gif

small spike at 58Hz, moves up to 62Hz when the pump speeds up. 3480->3720rpm?

Yep, DDC spins from 3465 tr/min at full flow to ~3900tr/min at 0"head. Codec cut high frequencies I think because I must compress sound records for bandwitch.
The 1048 is perhap's a bad recording but strange because I didn't change anything, just a pump replacement. There's a little spike at 50Hz but very small in comparison of 100Hz.

Sounds like the D4 could become nearly as quiet as the DDC, given the right electronics (i.e. done as a product update/improvement at Laing).
Is it possible that this more sophisticated electronics might not get along so well with over/under volting? Might be why they went with square wave on the D4. Probably just a cost of goods issue, though...

Simple coil switching of the motor coils is definitely the simplest and cheapest solution. It reduces losses in the drive circuitry and it also gives you more power out of the motor compared to a sinusoidal drive. The cost is reduced motor efficiency, increased motor heating, and increased noise. It's certainly possible to design a sinusoidal drive that will undervolt well, but cost, efficiency, and drive circuit dissipation tradeoffs may weigh against it. A sinusoidal drive shouldn't add more than $1-$2 to cost of manufacture.

After thinking about things, I am now more curious about the actual physical cause of the 50Hz switching noise of the D4. It cannot be electronic in nature, since electrons don't make noise. :D

So, is it the electromagnets vibrating as they are turned on and off? Is it vibration of the shaft as it is subjected to changing torque when the electromagnets turn on/off? Is the amplitude of the noise caused by the required travel freedom of the D4 spherical rotor? Would a traditionally axle driven rotor be less noisy for a given drive electronics type because it might be less "sloppy" ?

When you switch the coils on it generates a sudden torque pulse on the motor. The rotor is given a sudden push, and the pump frame experiences the same torque pulse in the opposite direction. Sort of like hitting it with a hammer at 50HZ to make it go around . Something similar happens when the coils suddenly turn off.

You can modify the abruptness of the torque pulses by changing where in the rotation you turn the coils on and off. If you turn the coils on when the magnetic field is at it's strongest on the coils you will get the worst case, if you turn the coils on before the rotor rotates into the strongest part of the field the initial torque pulse is less.

You can also reduce the abruptness of the torque pulse by turning the coils on and off slowly which is essentially what a sinusoidal drive does.

You can also get noise from the metal laminations that are used to build the core of the electromagnets. As the magnetic field is turned on and off they are alternately pulled together and apart. This is not usually a dominate noise source.

Thank you ferdb. That was what I expected to be the answer, although you describe it much more clearly!

I guess the operative question is "Why is the Laing pump so noisy in comparison to other pumps?" Is it doing a trade-off of noise versus efficiency that other pumps don't? Or is it made with cheaper tolerances so that the vibration from torque on/off is less damped (i.e. accumulating the energy from torque accel over time to deliver a rapid impulse when the slop factor is reached)?

The reason for asking is to see what the probability is for the pump mfg to produce a decent (still high head and low temperature) pump that is quieter if a bit more money is thrown into production costs or if we are experiencing a natural consequence of the required performance. You get what you pay for, but you can't pay to remove the laws of physics.

I'm sure most of the noise comes from the brushless dc motor and little from the pump. So if you make a quiet motor, you'll have a quiet pump. It's certainly doable, the question is is the market for such a pump big enough to bother with and will that market pay the price premium necessary for such a pump.

Maybe you are missing the key(?) : The D4 coils are fed with simple square wave AC, all the others are sine wave driven
(apologies if you already knew this!)

I knew that most pumps are given 120VAC or 240VAC power, but I was making sure that this was the only reason that the D4 is noisy. I was wondering if it was possible to keep the high efficiency square wave impulse and keep it quiet via mechanical dampening. Not insulation, but sturdy construction or other mechanical designs.

Thank you, though.

All I want to know is where I can buy one. :)

EDIT: Ack. Current pump failed. Cooked a Radeon 9800Pro 256. I just ordered the MCP650 directly from Swiftech. :shrug:

Sorry if this is mostly off topic, but does anyone know how MCP350 and MCP650 compare to CSP-750 purely on the grounds of acoustics?

MCP350 (DDC) is apparently "inaudible"
CSP-750 should also be inaudible, but I have heard of people claiming it gurgles.
MCP650 (D4) is far from silent, but it's likely a new version will fix that.

I don't hear my CSP-750s gurgling. In a closed case sitting on a piece of foam I cannot hear them at all. If somebody is hearing gurgling I would guess they still have bubbles in their system.