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WD SE16 Caviar 640GB is now Blue

June 19, 2008 by Mike Chin

WD Caviar Blue (SE16) 640GB WD6400AAKS-00A7B0 SATA 3 Gbps Desktop Hard Drive
Sample Supplier
Market Price

The 320GB WD drive we reviewed some weeks ago is the single platter version of the two-platter 640GB drive under examination here. Both of these drives feature very high areal density, 320GB/platter, which is just shy of the Samsung F1 1TB model's 334GB/platter. That does mean high performance, hopefully achieved with very low noise, like the other mentioned drives.

WD has just revamped its Caviar line into three color categories: Black, Blue and Green. The Green category is a no-brainer these days; WD's marketingspeak quips, "cool, quiet, eco-friendly." Blue represents "performance and reliability for everyday computing", while Black products provide "maximum performance for power computing." So does the SE16 Caviar in 640GB capacity still exist? Yes, it was only introduced a few months ago. The model number remains the same (WD6400AAKS-00A7B0) but its moniker is now Caviar Blue... a delicacy prized by fat cats everywhere?

The Caviar Blue 640GB 2-platter drive has a more substantial casing than the single-platter version.

We discovered during our review process that there were two different types of casings for the 320GB model, one considerably less robust than the other. The practical end result was that with one casing, the drive was very quiet, and with the other, it wasn't so quiet — demonstrating once again the importance of resonance and vibration control for good acoustics in all devices that have moving parts. Thus far, no such variations in casing has been discovered with the WD6400AAKS... but that does not necessarily mean it doesn't exist. We certainly hope it doesn't, because with the 320GB model, the casing difference is not indexed or referenced by the model designation, so there's no way of telling which casing you'll get unless you're actually looking at it.

WD Caviar SE16 (or Blue) 640GB WD6400AAKS

(from WD's product overview)
Top performance for Windows Vista - WD Caviar SE16 SATA and EIDE drives are certified for Windows Vista and are top performers on the Windows Vista Experience Index. The usual marketing fluff.
16 MB Cache - Bigger cache means faster performance. Quickly becoming standard.
Perpendicular Magnetic Recording (PMR) - The latest generation of WD Caviar SE16 drives employs PMR technology to achieve even greater areal density. PMR is quickly becoming standard. It's part of what makes the high areal density possible.
IntelliSeek™ - Calculates optimum seek speeds to lower power consumption, noise and vibration It sounds good.
SecurePark™ - Parks the recording heads off the disk surface during spin up, spin down and when the drive is off. This ensures the recording head never touches the disk surface resulting in improved long term reliability due to less head wear, and improved non- operational shock tolerance. Did not cause audible clicking in the 320GB version.
3 years End-user Limited Warranty OK, but not as good as Seagate's 5 years.

Specifications: WD6400AAKS & WD3200AAKS-00B3A0
Disks / Heads
2 / 4
1 / 2
Interface SATA 3Gb/s SATA 3Gb/s
Spindle RPM
7,200 RPM
7,200 RPM
Data Transfer: Buffer / Disk 972 Mbits/s (max) 70 MB/sec
Data Transfer: Buffer / Host (SATA) 3 GB/sec 3 GB/sec
Average Seek - Read / Write
4.2 / 4.7 ms
4.2 / 4.7 ms
Average Latency
4.2 ms
4.2 ms
630 g
600 g
Power Requirements: Idle / Seek
7.7 / 8.3 W
7.2 / 7.8 W
Acoustics: Idle / Seek / AAM
25 / 29 / 26 dBA
25 / 29 / 26 dBA

A quick glance at the table of published specifications indicates that the two drives are virtually identical, as they should be, aside from the number of platters and heads. This difference is reflected in the weight and power, which are higher in the 640GB model, but the acoustics are the same, which goes against the truism that higher platter count usually means higher noise levels. Automatic Acoustic Management (AAM) seek is not specifically mentioned; the reference is to Seek Mode 0 and Seek Mode 3, the latter showing the lower dBA.


Our sample was tested according to our standard
hard drive testing methodology
. The test drive sample was compared against many other drives. Our methodology focuses specifically on
HDD noise, and great effort is taken to ensure it is comprehensively measured
and described. Performance is usually not tested, for reasons discussed in detail in
the methodology article. For comprehensive HDD performance testing results,
we recommend Storage
, who have established a long reputation as the specialist in
this field.

Two forms of hard drive noise are measured:

  1. Airborne acoustics
  2. Vibration-induced noise.

These types of noise impact the subjective
perception of hard drive noise di fferently depending on how and where the drive
is mounted.

Both forms of noise are evaluated objectively and
subjectively. Both the subjective and objective analyses are essential to understanding
the acoustics of the drives. Airborne acoustics are measured using a professional
caliber SLM. Measurements are taken at a distance of one meter above the top
of the drive using an A-weighted filter. Vibration noise is rated on a scale
of 1-10 by comparing against our standard reference drives.

A final caveat: As with most reviews, our comments
are relevant to the sample we tested. Your sample may not be identical. There
are always some sample variances, and manufacturers also make changes without
telling everyone.

This sample came off the assembly line about one month behind the 320GB models we tested earlier.

Ambient conditions at time of testing were 17 dBA and 20°C.


The WD 640GB is smooth and quiet in operation, very similar to the better acoustics version of its single-platter 320GB sibling, to WD's older 500GB Caviar SE16, and also to the Samsung F1 750GB and 1TB drives. It has no audible tonality (sharp peaks that rise more than a few decibels from the average) in idle, and certainly nothing high pitched. The overall sound is broadband, except for the 120Hz fundamental tone of its motor spinning at 7200 RPM. The drive came with AAM disabled, and in seek without AAM, it developed a slight audible tonality around 2.2 kHz. Although the seek noise was low in amplitude, it was sharp enough to be audible from a meter away in a quiet room. Turning the AAM on improved the seek noise quite audibly. The 2.2 kHz tonal peak faded, and the sound became both smoother and quieter. Recent hard drives have not been much improved acoustically by AAM; this drive benefits a bit more with AAM.

The level of vibration was also very low, matching the WD Green Power, a feat because the latter's 5400 RPM speed gives it a natural advantage. It has low enough vibration that soft grommet mounting may be enough to keep them from becoming an audible factor in most systems, but this is probably subject to sample variance and the mechanics of the particular PC case.

There are no surprises in the power profile. It draws a bit more power than the single platter model, a little less than most 3-platter models, and more than either the 5400 RPM WD Green Power or the 2.5" VelociRaptor.


Mfg date

firmware version


(10 = no vibration)
Activity State

Airborne Acoustics

([email protected])

Measured Power
Western Digital WD6400AAKS

February 2008

firmware 01.03B01


6.8 W

Seek (AAM)


8.1 W

Seek (Normal)


9.3 W

WD VelociRaptor WD3000GLFS

(bare, w/o frame)

300GB, 10K RPM

15 May 2008

firmware 03.03V01


3.9 W
Seek (AAM)


5.7 W
Seek (Normal)


6.2 W
Western Digital WD3200AAKS

320GB (quieter casing)

February 2008

firmware 1AA01109


4.6 W

Seek (AAM)


5.8 W

Seek (Normal)


5.8 W

Western Digital Raptor WD1500ADFD

March 2006

firmware 20.07P20


8.2 W
Seek (AAM)
12.2 W
Seek (Normal)


12.2 W
Samsung F1 3D



February 2008

firmware 1AA01109


7.0 W
Seek (AAM)


8.8 W
Seek (Normal)


9.9 W
Seagate Barracuda

7200.11 1TB ST31000340AS

December 2007

firmware SD15


7.8 W
Seek (Normal)


11.6 W
WD Caviar SE16 500GB WD5000KS

March 2006

firmware 07.02E07


8.5 W
Seek (AAM)
8.6 W
Seek (Normal)


10.7 W
Western Digital Caviar Green Power 750GB WD7500AACS

October 2007

firmware 01.01B01


3.3~5.9 W
Seek (AAM)
5.4 W
Seek (Normal)


6.7 W
Hitachi Deskstar 7K1000 1TB HDS721010KLA330

June 2007

firmware GKAOA70M
Low RPM Idle
3.6 W


8.5 W

6.2 W (unloaded)
Seek (AAM)
11.7 W
Seek (Normal)


15.4 W
* These drives are references in the sense of previously tested and known entitities to which newly tested products can be compared and contrasted against.


The averge read speed of 90.8 MB/s with maximum burst speed up to 237 MB/s was similar to the results obtained with the 320GB Caviar SE16 samples, as was the 12.4ms random access speed. The read speed was faster than the 750GB Samsung F1's 77 MB/s, and about the same as the 1TB F1. Access speed at 12.4ms was slightly better than both the Samsungs, at 13.6ms and 13.8ms. In actual use, most users should see little or no differences among those various drives, except, perhaps, for big file transfers with the Samsung F1 750GB taking a bit longer. Turning Automatic Acoustic Management on to the minimum noise setting exacted a 4ms price in access speed.

Almost identical to the WD 320GB model, and similar to the Samsung F1 1TB drive.

With AAM engaged for lowest noise, random access speed suffered.



Audio recordings were made of the drives and are presented here
in MP3 format. The recordings below contains 5 seconds of ambient noise, and
10 seconds of idle noise followed by 10 seconds of seek noise with AAM enabled
and 10 seconds without.

Keep in mind that the recordings paint only part of the acoustic
picture; vibration noise is not recorded, and drives often sound different depending
on the angle from which they are heard.

These recordings were made
with a high resolution, studio quality, digital recording system, then
converted to LAME 128kbps encoded MP3s. We've listened long and hard
to ensure there is no audible degradation from the original WAV files
to these MP3s. They represent a quick snapshot of what we heard during
the review.

Most recordings are made
from a distance of one meter. The recording is intended to give you
an idea of how the subject of this review sound in actual use — one
meter is a reasonable typical distance between a computer or computer
component and your ear.
For best results, set your volume control so that the starting stretch of ambient
is just barely audible. Be aware that very quiet drives may not be
easily audible in idle — if we couldn't hear it from one meter, chances are we couldn't
record it either!

More details about how
we make these recordings can be found in our short article: Audio
Recording Methods Revised


Technical Note: Acoustically astute listeners may notice a qualitative difference in the ambient at the start of the WD6400AAKS sound file, and the ambient in all the other files. You are not hearing things, it is there. The WD640GB drive MP3 is the first recording made with our new 1" test microphone system from ACO Pacific. The new mic has a different sonic signature than the Sennheiser ME-66 we've used for the past couple of years. The Sennheiser is optimized for speech intelligibility, and to that end, it has a frequency response which drops steadily by about 2 dB/octave starting from 500Hz to a maximum drop of about -8 dB at 40Hz. In plain words, it sounds a bit thin in the bass. There's a broad peak of about 3 dB centered around 8kHz which helps with voice intelligibility but also adds a brightness to all sounds. The ACO Pacific mic is much more linear, with a ruler-straight response from under 10Hz all the way to over 15kHz, and it has less internal noise. The differences can be heard, and it may affect your perception of how audible and/or annoying a particular noise really is. Be forwarned that recordings made with this new mic may make the earlier ones sound brighter and thinner. This will tend to give an unfair advantage to new recordings when you're comparing them to earlier ones. Focus on the difference between the ambient and the product noise within each recording. This difference should be your guide.

Sound technologists may ask why not just apply a frequency tailoring filter to the new sound files to emulate the sound of the Sennheiser mic and avoid the discontinuity? This option was explored and rejected after much experimentation because the effect was not truly convincing (ie, the ACO Pacific mic still didn't sound like the Sennheiser) and it would artificially extend the use of a less accurate recording tool. Better that you all get used to the sound of the new, more accurate mic sooner rather than later.

After it is operational, we'll record a sampling of reference quiet products with the new mic in SPCR's sound isolation / anechoic chamber and use them as comparative references in future reviews. This was also done the last time we made an upgrade in our microphone. Some of our product samples are long gone, some products are discontinued, and some products are not worth refreshing, so many of the existing sound recordings will never be updated. This is a bit unfortunate, but impossible to avoid when trying to maintain a reference library in a field where products have such short lifespans.


The WD640 is a highly viable alternative to the Samsung F1 750GB and 1TB drives, which appear to be their natural competitors. None of the other drive makers have released drives with greater than 300GB/platter areal density. The WD640 is the equal of the Samsung F1s acoustically, and very close in performance. It betters the F1 750GB model in sustained read speed, and matches Samsung's 1TB model (at least on our test system). Note, however, that the performance of this drive is excellent, at or near the top of the current 7200 RPM desktop drives.

There have not been any reported variants of the WD640's casing, unlike the single platter WD320 we mentioned at the start of this review. The casing feels quite sturdy, more substantial than either of the WD320 casings we examined. Despite the the WD640's 2 platters, it seems subjectively a touch quieter than the quieter sample of the single-platter WD320.

The bottom line on the Western Digital WD6400AAKS is that it is a very quiet desktop drive offering excellent performance and high capacity at a sweet price. What's not to like?

Many thanks Western Digital for the review sample.

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SPCR Articles of Related Interest:

SPCR's Hard Drive Testing Methodology

SPCR's Recommended Hard Drives

WD VelociRaptor WD3000GLFS

WD WD3200AAKS single platter drive

Samsung F1 750GB & 1TB Drives: Fast... and Silent?

WD Green Power: A New Benchmark in HDD Acoustics & Power

The Terabyte Landmark: Hitachi Deskstar 7K1000

Seagate Barracuda 7200.11 Terabyte drive

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this article in the SPCR Forums



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