SEAS KingRO4Y Mk III Active Loudspeaker Kit - Pair

SEAS KingRO4Y Mk III Speaker Kit - PAIR

Price shown includes the sale price on the Hypex units and 10% discount on all other parts!

Watch YouTube video "SEAS King RO4Y MKIII Speaker Build By Von Hertzog at The Social Club - Undisputed KING of DIY Kits"

The SEAS KingRO4Y is a 3-way loudspeaker kit, using a 10" aluminum cone subwoofer and a 6.5" midrange coaxial. The coaxial unit uses a magnesium/aluminum-alloy cone for both the midrange and dome tweeter. All are housed in a compact sealed box enclosure and powered by the Hypex Fusion FA503 or FA253 DSP + NCORE® amplifiers.

The design goal for this kit is to get a true fullrange loudspeaker system in a compact enclosure with outstanding performance.

Application Notes & Assembly Guide (pdf)

Product page & DSP file on Seas website here.

The Drive Units

To achieve the design goals of this kit we chose to start with a coaxial unit in order to save some baffle space and get the unique benefits of sound quality that a coaxial offers. Since the chosen midrange coaxial can easily play down to 150Hz, it was possible to use a high quality subwoofer with excellent low-frequency extension to take care of the lower frequencies.

Seas Excel C18EN002/A - The coaxial unit uses a lacquered magnesium/aluminum-alloy cone and dome, and are integrated to form a single acoustic source. A benefit of the coaxial arrangement is that the off-axis response is equal in all directions. That makes the sound imaging very stable with a large sweet spot. It uses a Neodymium magnet system for optimum air-flow, minimal back wave reflection and a healthy sensitivity.

Seas L26RO4Y - This subwoofer driver is the perfect solution for good bass in a small enclosure. With its high power handling and low Q and Fs it can handle a large amount of EQ in the low end. Since it also has a smooth response high up in frequency it can be used all the way to a midrange unit, thus eliminating the need for a dedicated mid-woofer in this loudspeaker kit.

The Amplifier and DSP

We chose to use a three channel plate amplifier with DSP capabilities which is of high quality, easily available and provided ample power for the speaker system. The choice lands on the Hypex FusionAmp FA253 or FA503. They deliver 2x 250W and 2x 500W respectively into the subwoofer and midrange section & 1x100W into the tweeter. They have a large filter bank for crossover and EQ. Three channels of amplification mean that DSP is available for each individual driver.

Detailed info and datasheets on the DSP-amplifiers can be found on the Hypex website.

Note: The Hypex units are not supplied with 3-pin IEC power cords. Consider the Supra LoRad 2.5mm MKII, available factory terminated or build your own! 

The Enclosure Design

One of the design goals of this system was to make a compact enclosure that is also relatively easy for a DIYer to build. The bracing inherent in a chambered design adds a high level of rigidity to the cabinet. The finished cabinet measures 12.2" wide x 19.7" tall x 12.2" deep. 

For even more low end-output, the system can be made into a floor standing speaker by extending the subwoofer enclosure height another 19.7" and adding two SL26R 10" passive radiators.

Each KingRO4Y Kit Includes:

(2) Seas Excel C18EN002/A 6.5" Coaxial Driver

(2) Seas Extreme L26RO4Y or Seas Extreme L26RO4Y2 10" Aluminum Cone Subwoofer w/ 4-layer Voice Coil

(2) Hypex FusionAmp FA253 3-channel NCORE® Amplifier w/ DSP (higher powered amplifier available from drop down menu)

Optional Accessories Package Includes:

(1.5) Wool Felt 1/4" thick, 36" x 36" - line internal walls of cabinet

(.5lb) Acousta-Stuff - fluff and fill the inside of the cabinet

(12) OXSOCKET8x1 hex head screws - mount coaxial to front baffle

(16) OXSOCKET10x1 hex head screws - mount subwoofer to front baffle

(20) OXSOCKET6x3/4 hex head screws - mount Hypex to rear baffle

(4) QC110 quick connects - connect speaker wire to tweeter

(4) QC205 quick connects - connect speaker wire to midrange

(4) QC250 quick connects - connect speaker wire to subwoofer

(4ft) Foam Tape - airtight seal of coax drivers to cabinet

The Measurement Results

Anechoic chamber frequency response. All of the measurements are made at 1m at tweeter height.

Sound pressure frequency response measured in an anechoic chamber is shown. The below figure shows the off-axis measurement at 0°, 15°, 30°, 45° and 60° using "Preset 1" in the provided DSP setup file.

The next figure shows the on-axis response of the different presets provided in the DSP setup file.

Listening Room and Placement

High quality stands should be used to bring the tweeter approximately to ear level or slightly above. This can also be accomplished by building the cabinet into a tower. Even in the best listening room, it is important to determine the positions where the loudspeakers will perform optimally. Placing the cabinets too close to the walls or corners will result in more powerful bass but may also cause response irregularities in the bass/midrange area. Some experimentation is recommended in order to find cabinet positions that result in a good tonal balance and freedom from coloration.

As can be seen from the off-axis response plot above, the smoothest listening angle is around 15° - this should be taken into account when placing the speakers.

After finding a good placement of the speaker, then there are almost endless possibilities to fine tune the sound balance with the Hypex DSP. Please see the Application Note for further details.

Seas Excel C18EN002/A (E0060) 6.5" Coaxial 

Seas L26RO4Y 10" Subwoofer

Single kits are available for 1/2 the price of the pair.