It was kind of a coincidence, but it was in fact Christmastime when we received a not-so-surprise gift from an angel. He put an active module with a digital sound processor under our tree; we had been waiting for it for a long time because it was an important gap in our range of products. Okay, the WAM 300 DSP wasn’t exactly free – the costs for the CE test alone were quite a blow to the pocketbook. But without the required certification, you can’t sell any devices within the EU. Simply printing “CE” on it wasn’t enough for us.The fact that we still ended up with a module that had a switching power supply and proven 270 watts of output, remote control and software controls for under 250 euros is surely grounds for celebration. Finally, the direct path to the home theater heavens is no longer littered with hindrances in the form of third-party products. The first one to benefit from the dawn of this new age is our SB theater, whose subwoofer is now available both in the familiar 75-liter reflex box and also with a space-saving 35 enclosed liters, thanks to a large number of adjustments. In exchange, these subwoofers are happy to help us explain the features of the WAM 300 DSP a bit further.
We don’t want to spend too much time explaining the structure of the reflex version of the SB 29 Sub; that has already been done in detail in another report. There, interested readers will find the assembly plan and the SketchUp file available as downloads. Also not really worth a long discussion is the enclosed box, which we created with brute force and a handheld circular saw from the top 36 centimeters of the old construction and a new floorboard made of black MDF. Still, we drew it in SketchUp; it can be downloaded here as a zip file
We are not providing any pictures of the cabinet assembly this time; for one thing, they have already been given for the reflex version, and for another the closed cabinet is hardly worth the princely effort involved in photographing it. Still, we will let you take a look at them – after all, it’s nice to know what you’re going to be putting in your living room.
Anyone who wants to install the WAM 300 DSP in a subwoofer simply needs to cut out a matching hole measuring 23 x 18 cm, without any backing structure. All of the outgoing connections are perfectly sealed, and there is even a wide rubber seal glued all the way around the metal plate. Since we like to use two subwoofers – and not because the added price is commercially attractive – we put the module into its own housing, with a bi-wiring box in the back and a slit for the infrared eye in the front.
An extensive PDF helps with the software installation and provides information on the use and equipment of the WAM 300 DSP. Left-click to load it instantly to your computer, and then we won’t have to torture ourselves and our readers with any more product presentations on high-gloss paper. However, we especially want to point out the otherwise unexplained feature of the low-pass filter, which can also be switched off, for use with an AVR with adjustable LFE output. It practically turns the plate amp into a mono amplifier with DSP bass management. Still, the small box cannot be used as a remote-controlled full mono amplifier with customized room adjustments for boxes with a passive crossover, since a steep-edged filter separates all of the subsequent upper notes from the ear at 2 kHz.
Now we come to the real meaning of life, I mean the report, in which we look at the use of the software and how it affects our subwoofer. First let’s take a closer look at the program window that we see on the screen once we have installed and started up the program.
Right at the top is a menu bar, which actually only consists of “File” – that includes the terms Load, Save, Write and Exit. “Link” is used to search for a module that has already been connected to the PC via the provided USB cable. Otherwise, the user will see “Device not found.” “Help” simply tells you which version of the software is on your computer.
Also just for informational purposes, but this time with content, are the things below the bar. If the subsonic filter is turned on, the red line will drop off wherever the middle slide controller tells it to. The setting range is between 16 and 40 Hz. At the top, the right-hand slider regulates the separation frequency between 40 and 160 Hz, and below it you can choose an edge steepness of 12 or 25 dB / octave. Clicking on LFE turns off the separation altogether. The volume is determined by the left-hand fader, which goes from -26 to 0 dB. As you would expect, the phasing can be moved up to 315 degrees in 45-degree steps. That allows a perfect adjustment to the satellites even without a measurement system. The user can choose the shutdown time, and Night Mode lowers the bass level quite a bit, to the disappointment of any children who have already been sent off to bed. These presets can always be modified using the software, according to the user’s needs or those of the other satellite devices, and they always have the same effect on the equalizer functions, which can be seen below for different modes. In nine frequency bands, the level changes in different ways according to which program has been set. Music simply needs a different kind of emphasis than home theater. You can save the settings and restore them by clicking on mem1 through mem3, and the factory settings are “default.” The following images give you a quick overview of the provided programs.
Next let’s look at the “defeat” setting, which sets all of the controllers to zero within the range of 16 to 80 Hz at 25 dB edge steepness, and its effects on the SB 29 CB, the enclosed 35-liter subwoofer:
The “music” setting creates more volume around the bottom and reduces it slightly at the top:
A home theater needs more power, which is achieved by emphasizing the range from 40 to 60 Hz:
For increased dynamics, the next setting is adjusted:
If you want a lot of bass, “impact” is what you’re looking for:
The outstanding implementation of the software’s requirements in the box can be seen clearly here in terms of volume and frequency. Unlike most sub-modules, it represents exactly what was pre-set by the manufacturer. As a comparison, here are all of the frequency curves at a glance:
The five fixed program settings cannot be changed or adjusted to a specific subwoofer. Oh well, too bad, you would normally say, but then you see the item “user” on the remote control and in the software. So it does exist, a place to store customized settings according to the space and the listener’s tastes. Of course it would be ideal to have a measurement system handy to smooth out the frequency curve of any bass cube or block. Unfortunately, though, most households don’t have that. So for our assembly suggestions we will test settings that can be used as a basis for your own experiments. Variations are always possible, and they aren’t restricted to the upper section of the program window, where you can, for instance, establish 50 to 60 Hz as the upper separation for large satellites or 30 Hz as the lower limit for small subwoofers.
As is common in most cases, we set the “user” limits at 16 and 80 Hz and then blew up the little SB 28 CB to a large bass. We decided against using attention-seeking effects. The goal was a linear frequency curve with a -3dB point at 30 Hz, which is intended for listening to music with the enclosed SB 15 Front.
Naturally the SB 29 CB is also a wonderful supplement to the SB 18 when it is used in a home theater. In that case, the separation frequency should be set to 50 Hz.
Anyone who wants to expand the SB 36 with a subwoofer will do better with the larger reflex cabinet. Naturally, we also connected that to the WAM 300 DSP and took some measurements.
We did not document the upper separation at 50 Hz or even lower, which is also useful with the SB 36. However, the reflex tube can also be closed off and the satellites can be capped at 80 Hz using AVR, with the setting shown here. But we did measure some more unusual separations at 120 (24dB) and 150 Hz (36dB) with 25 Hz subsonic, and obtained some nice frequency curves.
These specifications can also be used to support a wide-range speaker like the AX-08 in an enclosed 20-liter cabinet, with the necessary bass foundation.
Now that we know what can be done with the DSP, we need to remember that it still needs to be transferred from the PC to the WAM. We captured this process in pictures.
First the fader settings are saved to the memory (here, mem3) and backed up in a folder.
In order to transfer the file to the module, it first needs to be loaded again. It can be found in the WAM 300 index, where we saved it earlier. Any number of settings can be saved there; they should be labeled with more characteristic names than mem1 through 3 for easier searching. Anyone who owns several different subwoofers – we don’t know anyone like that, but let’s not rule it out – could even create separate folders to help organize them.
The overwrite is initiated through “Write” and confirmed by the software. The fader settings here do not match the actual file.
On some computers, a “Connect failed” message is shown over the confirmation because the connection to the module was interrupted after the transmission. At first this bothered us, along with the fader display, but the newly loaded data and the measured curves were correct. The USB cable just needs to be taken out of the amplifier once it has received the data.
It is relatively easy to set the right levels for the subwoofer, especially since it can also be corrected later with the remote control. Achieving the right phasing between the subwoofer and the satellite is an important step, which depends on more than the relative positioning of the boxes. Without a measuring device, this setting is harder to adjust simply by ear and personal preference, but nonetheless possible. First, the volume is balanced out and then the phase is shifted by 180 degrees. Starting with the more even bass behavior, the rest of the fine tuning takes place in 45-degree steps. There will probably still be a few small audible faults in the tuning at the end, but after at most a couple of days of adjustments, the results will be nearly ideal for the space and your own preferences. We have still plenty of work to do too, since there are plenty of other basses waiting to be set up with the WAM 300 DSP – and some of them are also still waiting for the matching satellites to be developed.
The loudspeaker assembling kits and the DSP Subwoofer amplifier can be ordered here:
Kit : SB 29 SUB-CB (closed), inlcudes: speaker, DSP Subwoofer module, Terminal, Sonofil