A High-Performance loudspeaker kit featuring the SEAS Metamodal™ TPCD coax C16NX001/X.

This compact loudspeaker kit excels both in stereo and surround sound setups with its point source dispersion, balanced sound and versatile placement. You can choose between making it with a passive crossover or a dsp.

Drive unit
The coaxial driver is SEAS C16NX001/X - E0121-04/06 feauturing Metamodal™ TPCD diaphragm for both the tweeter and woofer. This has low weight, high stiffness and controlled damping ensuring an unparalleled sound quality. Combined with an FEA optimised magnet system and a Titanium voice coil former this compact driver can really deliver a dynamic, clean and detailed sound.

Enclosure
We wanted to make a compact speaker, so we chose to use a closed box design. The internal volume is 5,7L resulting in a Qbox of 0.59. This give the driver a good balance between low end extension, transient response and a flat SPL. The enclosure is filled 70% with a polyester foam damping material without compacting it. Most distributors have a version of this and they come with many different brand names: Acousto-Q, Acoustilux, Acousta-Stuf and so on.

The Crossover
We chose to build both an active and passive crossover to let everyone choose their preferred setup. In this kit we used a miniDSP 2x4HD to do the dsp task, but it could also be implemented on most other dsp platforms.

With the crossover we aimed for a balance between a smooth and slightly falling response in the listening window and a smooth power response while keeping a good phase tracking between the drivers. The listening window is here defined as the average response within 0-30 degree off-axis.

The passive filter uses a 3rd order electrical high-pass for the tweeter, and a 2nd order low pass with a correction filter for the woofer. The resulting crossover point is 2kHz. All capacitors are metalized polypropylene foil and the coils are air-core coils, except for the 1.2mH coil which uses an iron core. The resistor is 10W MOX.

On the active filter, we have used a selection of parametric EQ's, Pole shift, high and low pass filter, shelving filter and an all-pass. The all-pass filter is used to get the two drivers in phase over a large frequency range for a seamless crossover between them. The crossover point is also here set at 2kHz.

The schematics for the crossovers are shown in the below graphs. The setup file for the miniDSP is available as a download on the top of the page. This also includes the measurements of the drivers in the box and the VituixCAD file for simulating the crossovers. This can be used to explore other ways of tuning the dsp or passive crossover.

Active:

Passive:

Measurement Results
The on-axis measurement of the SEAS Toy kit, including the individual drivers and a measurement with the tweeter polarity inverted is shown below.

Active:

Passive:

The next graph shows the off-axis response. Here we can see a nice and controlled off-axis dispersion. Then we know that the room reflections also have a smooth frequency response so that we get a large and natural sound stage.

Active:

Passive:

The harmonic distortion is shown in the last graphs below. Here we have set the on-axis SPL to be 96dB averaged from \SI{100}{\hertz}-\SI{10}{\kHz}. Then we can see that this speaker has a very low distortion, even at a high SPL output.

Active:

Passive:

Listening Room and Placement
High quality stands should be used to bring the tweeter approximately to ear level. It's important to experiment with different positions in the room and toe-in to find where the loudspeakers can perform at their best with good tonal balance, defined sound stage and freedom from coloration. Placing the cabinets close to the walls or corners will result in more powerful bass, but may also bring about response irregularities in the bass or midrange area. For some extra punch in the low end, you could pair it with one of our Extreme subwoofers.