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B&W ASW CDM
12" Active 1 kW Subwoofer (c. 2001-2003) MADE IN ENGLAND
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B&W ASW CDM

B&W ASW CDM (12" driver in sealed 15.4 x 15.6 x 19.3" cabinet with 1kW amplifier, 72 lb/32 kg, about $650 used). I got mine at this link directly to them at eBay (see How to Win at eBay).

September 2014       All Reviews    Audio Reviews    B&W Reviews

 

B&W ASW CDM

Back, B&W ASW CDM. enlarge.

 

B&W ASW CDM

B&W ASW CDM. enlarge.

 

Introduction         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

Adorama pays top dollar for your used gear.

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I use these stores. I can't vouch for ads below.

The B&W ASW CDM is a very sturdy (72 pounds/32 kg) sealed subwoofer with a 1,000 watt amplifier. It doesn't mess around; it has enormous output and decent response right down to subsonics. This is not some lightweight offshored vented-box imitation; this is the real thing.

It sounds great, pumping out loads of deep clean bass where few subwoofers can.

It has same performance as the ASW800 subwoofer, but in a simpler and therefore less expensive conventional cubical cabinet. It actually has about the same response as the awesome 15" ASW850 and ASW855, but with less maximum output.

The ASW CDM goes an octave below what most other common "subwoofers" can reproduce.

The bass is half the music, so especially if you've only got wimpy speakers like the B&W 805, you need a pair of woofers like this.

The B&W ASW CDM is styled to match the CDM1 speakers.

The ASW CDM has no resonances and just thuds where it needs to, never adding its own coloration or changing the pitch.

I prefer crossing this woofer in below 40 Hz to reproduce only the lowest bass when used with with decent full-range speakers like the B&W 802. For the ASW CDM, bass guitars are trivial; standard 4-string bass guitars and stand-up basses don't even play as deeply as 40 Hz; the ASW CDM kicks in and gets busy below where the basses usually stop!

The ASW CDM is built like a tank. Its solid sides don't vibrate at all to the touch when the woofer cone is moving a half-inch or more in and out.

The woofer cone looks like paper, but it's actually paper and Kevlar. It feels more like thick cardboard or a thin sheet of wood veneer than just paper.

The 1,000 watt amplifier is silent; there's no buzz or hiss even if you stick your head to the woofer cone.

 

Specifications         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

 

Driver

12" (300mm).

Paper/Kevlar cone.

Rubber surround (not foam).

 

Frequency Response

Frequency Range: 15 - 140 Hz at -6dB.

Frequency Response: 20 - 110 Hz ±3 dB.

 

Internal Amplifier

33k Ω input.

Power output: 1 kW (1,000 watts).

SNR: > 90 dB.

 

Internal Crossovers

Low pass: 12 dB/octave, 40-180 Hz continuously variable.

High pass: 18 dB/octave, fixed at -6 dB at 80 Hz.

 

Power Input

Two-prong polarized standard HP power cable.

100-230V, 50-60 Hz.

Rated 150 watts power consumption.

See also actual measured power consumption.

 

Colours

Black Ash (shown), Cherrywood or Red-Stained Cherrywood.

Black grillcloth.

 

Included Accessories

The included cord is quite nice. It's only 6 feet (1.8 meters) long, but very soft and flexible. It's a two-conductor (ungrounded) cord.

 

Base Thread Pitch

There are four M6 (6mm maximum thread outer diameter x 1.0mm pitch) threaded inserts on the bottom to attach the rubber floor bumpers or spikes included above.

 

Size

15.4 x 15.6 x 19.3 inches HWD, including front grille and rear controls but excluding any screw-in feet or spikes.

392 x 396 x 490 millimeters HWD, including front grille and rear controls but excluding any screw-in feet or spikes.



Weight

71.5 pounds (32.5 kg).

 

Price, USA

September 2014: about $650 used.

When new: about $2,000.

 

Measurements         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

 

Sensitivity

7 mV produces 100 dB SPL at 1 meter at 100 Hz in anechoic half space with the level control at maximum.

With the level control at center (12 o'clock), 45 mV at 100 Hz produces 100 dB SPL at 1 meter in anechoic half space.

With the gain control in the 9 o'clock position, 200 mV at 100 Hz produces 100 dB SPL at 1 meter.

 

Maximum Input Level

It starts distorting with low frequency inputs above 500mV, regardless of the position of the level control.

The high-pass filter is perfectly happy with signals up to 5.5 volts.

 

Maximum Output

Whatever it is, it's more than I fealt like measuring.

 

Frequency Response

I'm impressed: it reasonably meets its response claims down to 14 Hz! Speakers usually lie about bass performance, so this is encouraging.

My measurement preamp is down 0.5 dB at 20 Hz and 1 dB at 14 Hz, and my measurement mic is down 0.5 dB at 20 Hz. Therefore, add 1 dB at 20 Hz.

These are measured in the BYPASS position for the low-pass filter. Response extended to about 160 Hz, and was down about 20-30 dB by 300 Hz.

Like most good subwoofers, the ASW CDM uses internal equalization to get the response flat to lower frequencies. The amplifier applies a lot of low frequency boost, and the 1 kW amplifier and sturdy driver suck it all up with aplomb.

There are two EQ settings: A and B. The A setting gives the flattest, deepest bass, while the B position doesn't extend the low frequency response as much in exchange for the ability to play louder for most music.

In the A position, the ASW CDM applies the most boost at 16 Hz; God bless B&W!

 

B&W ASW CDM frequecy response

Frequency response at 1 meter, half-space anechoic, "A" EQ setting, 16-160 Hz, LP filter OUT.

The A EQ setting boosts the amplifier's response deeper, to about 17 Hz. The B EQ setting doesn't boost the really deep and subsonic bass as much:

B&W ASW CDM frequecy response

Frequency response at 1 meter, half-space anechoic, "B" EQ setting, 16-160 Hz, LP filter OUT.

With my Radio Shack SLM, it's -3 dB at 28 ~ 140 Hz at A, and 36 ~ 130 Hz at B EQ.

 

B&W ASW CDM frequecy response

Frequency response at 1 meter, half-space anechoic, "A" EQ setting, 16-200 Hz, LP filter set to 180 Hz.

 

B&W ASW CDM frequecy response

Frequency response at 1 meter, half-space anechoic, "A" EQ setting, 16-100 Hz, LP filter set to 40 Hz.

 

B&W ASW CDM frequecy response

Frequency response at 1 meter, half-space anechoic, "A" EQ setting, 10-100 Hz, LP filter set to 40 Hz.

 

B&W ASW CDM THD at 90 dB

Frequency response at 1 meter, half-space anechoic, "A" EQ setting, 16-200 Hz, LP filter set to 40 Hz (lowest trace), 180 Hz and OUT (highest trace).

 

B&W ASW CDM THD at 100 dB

THD at 90 dB SPL at 1 meter, 16-200 Hz. (100 dB SPL set at 100 Hz, actual SPL varied with frequency as shown above.)

 

B&W ASW CDM THD at 100 dB

THD at 100 dB SPL at 1 meter, 16-200 Hz. (100 dB SPL set at 100 Hz, actual SPL varied with frequency as shown above.)

 

High Pass Filter

 

HPF Gain

-0.035 dB at 1 kHz.

 

HPF Channel Balance

The right channel is 0.0086 dB lower than the left.

 

HPF Output Source Impedance

104.6 Ω (-2.6 dB when loaded by 300Ω)

 

HPF frequency response

It's 18 dB/octave at 100 Hz:

B&W ASW CDM THD at 100 dB

High pass filter frequency response, 20 ~ 1,000 Hz.

 

B&W ASW CDM THD at 100 dB

High pass filter frequency response, 50 ~ 200 Hz.

 

HPF high frequency response

B&W ASW CDM THD at 100 dB

High pass filter frequency response.

I measured it to 110 kc and it's just as flat.

 

HPF Maximum Level

5.5 volts at 0.1% THD, input and output level.

 

HPF THD vs. Input Level

B&W ASW CDM THD at 100 dB

High pass filter THD versus input level 1 kHz.

 

HPF Output Noise Level

-94.5 dBV A-weighted, -85.6 dBV unweighted, 22 kHz bandwidth.

 

Measured Power Consumption

0 watts, switched off (no pilot light).

2.0 watts in standby (red LED, standby or sleeping).

22.3 watts at idle (green LED, ready to play).

23-27 watts playing at reasonable or loud levels.

AC power draw is directly related to instantaneous audio output. It demands a firm AC supply line and will flicker your lights if it isn't.

The ASW CDM should cut itself off if you do something really stupid and your power breaker doesn't blow first. If the ASW CDM cuts itself off, turn the big power switch off and on to reset.

 

Magnetic Fields

The ASW CDM's big magnet isn't shielded, so keep it away from color CRT displays.

I measure as much as 2,000 µT (20 Gauss) around the sides of the ASW CDM. Directly in front, I measure as much as 1,500 µT (15 Gauss).

 

Compared         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

The ASW CDM seems to have identical performance to the ASW800, which has the same response but only 67% the acoustic output of the ASW850.

I compared the ASW CDM and ASW800 side by side; they distort the same way at the same levels and frequencies.

The ASW800 and ASW750 have the same performance specifications as the ASW CDM, with the same weight and box volume, amplifier size and driver size. It seems the real difference between these are how fancy are the cabinets.

 

Usage         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

 

Unpacking

Put the box upside-down, with the bottom up. Open the bottom flaps, remove the bottom foam, turn each box over where you want each woofer, and voilà, your ASW CDMs are sitting right where you want them.

 

Packing

If you no longer have the original box, double or triple box it.

Put bubble wrap on the back where there are no heat sink fins.

Put it face-up in an smaller box, with more bubble wrap to cushion the back which faces down.

Fold the flaps of the smaller box over the front grille. We're going to hope that the curve of these flaps as you've folded them will protect the grill.

Still leaving the front grill UP, put the smaller box inside a much larger box, with plenty of padding all around.

 

Grill

There are two B&W logos; one shows on the grill, or on the speaker if there is no grill.

The grill also mounts upside-down.

 

Placement

Few nonprofessionals have any idea how critical is placement.

A small 8" subwoofer placed well in a good room will sound far better than this great subwoofer put in the wrong place, or used in a poor room.

Don't put on the spikes (if you use them) until you've spent a few weeks listening and moving the woofers around for the best sound.

Personally, I use a dolly to move this around to find the best position.

Try to keep the subwoofers near each of your main speakers to keep the wavefronts coherent. For instance, if you have the subwoofer several feet further away than your main speakers, you may get a big suck-out at 60 Hz, requiring setting the phase switch to 180º to remove the response dip. That seems reasonable, until you realize that having your woofer further away is delaying your bass by an additional several milliseconds or a significant portion of a wavelength, which does nothing to give you the tight, coherently bass you deserve.

 

Pilot Light

Off is off (no power consumption).

Red means the woofer is in standby ( 2 watts power consumption).

Green means the subwoofer is on. (about 22 watts power consumption at idle or playing at reasonable levels.)

 

Power Switches

There are two power switches.

There is a big square rocker switch and a little slide switch. Flip the big one to ON and the little one to AUTO.

The big rocker switch is a regular switch. Leave it on; it's just a way to disconnect the subwoofer completely if you're leaving it for a long time.

Once the subwoofer is plugged in and the big rocker is turned on, the pilot light lights.

The little slide switch has four positions: STANDBY, AUTO and ON.

STANDBY is a silly setting. It forces the ASW CDM to stay in STANDBY (red light) mode, and not turn on. The only reason for this position is working in a laboratory where you want to mute the system while changing connections.

AUTO is the correct setting. In AUTO, the ASW CDM turns ON (green light) as soon as it gets any signal, and goes back to STANBY (red light) after a few minutes of no signal.

ON forces the system ON at all times.

 

Stereo Sound

Ideally you should use two subwoofers for stereo.

If you use only one subwoofer, be sure to cross it over as low as possible (like 40 Hz) so that you are turning as little of the bass into mono as possible.

 

Built-in Crossover

The built-in crossover is all you need for simple installations. Simply feed the signal from your preamplifier to both your main power amplifier as well as the ASW CDM's input. My Apt preamp has dual outputs, if your's doesn't, use a piggyback cable to send the output to both places.

I wouldn't bother with the built-in high-pass crossover. I see no reason to run my main signal to a subwoofer and back. If you want better sound, use an external crossover:

 

External Crossovers

See the crossovers section of Stereo Subwoofers.

 

Crossover Frequencies

Set the crossover to 40 Hz for most uses. If you're using small speakers like the 805, set it higher, typically to the rated low frequency cutoff of your main speakers.

Try setting the crossover to 40 Hz even with smaller speakers and increasing the subwoofer level for a smooth crossover at the higher cutoff frequency of the smaller speakers. This can get you a smooth crossover and a big boost in response below 40 Hz.

Using higher crossover settings will get more boom, as opposed to deep bass, out of the ASW CDM.

 

Levels

B&W suggests starting at the 12 o'clock setting and going from there.

I find if you're using this with a typical main amplifier and speakers that that's about right, which is a load of bass. I usually have to turn it down from 12 o'clock.

 

Recommendations         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

I love this woofer. It does what it's supposed to, and is easy to move around and set up.

If you think you want one, you'll love it!

If you've found all the time, effort and expense I put into researching and sharing all this, this free website's biggest source of support is when you use these links, especially this link directly to them at eBay (see How to Win at eBay), when you get anything, regardless of the country in which you live. Thanks! Ken.

 

More Information         top

Intro   Specs   Measurements   Compared   Usage   Recommendations   More

 

ASW CDM flyer

ASW CDM users manual

ASW CDM PDF drawing

ASW CDM CAD drawing

 

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Mr. & Mrs. Ken Rockwell, Ryan and Katie.

 

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27 September 2014