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| Introduction | Estimates | Design | Measurement | Equalization | THOR-ORION xo |
| Supplies | SPL limits |


THOR Construction Plans+

The plans provide detailed information for building and integrating THOR subwoofers with the ORION. These subwoofers will NOT extend the low frequency response of ORION. They will only add deep bass output VOLUME capability. The word 'subwoofer' is not the right descriptor since it acts like a 'substitute woofer'. The THOR units may also excite unfavorable room mode resonances depending upon their placement. THORs can have their application if you try to listen at realistic volume levels to organ music, or to sound effects from the movie LFE track. Thus I recommend to listen to ORION first and establish that you really need to add THOR to be satisfied with the maximum bass volume capability of the ORION System. Note that the ORION xo/eq has a 30 Hz, -6 dB/oct low-cut switch on its front panel, which reduces subsonic woofer cone displacements and effectively increases bass output capability when engaged. (See your ORION Owner Support Page) THOR can be added later and does not require any changes to an existing ORION System. 

The THOR plans also serve as an example on how to correctly integrate subwoofers with existing loudspeakers. The places where the electronics need to be customized, and how to go about it, are clearly marked in the circuit description.

This is a simple project and can be a good learning experience for working with line level crossover filters and equalization.

For budgetary purposes consider that the total material cost for two THOR units, including tax and shipping, is approximately $970. Adding the power amplifiers will increase this to $1720. Building a set of woofers takes about 20 hours of your time. 

 - THOR Construction Plans + pcb
 - Electr. components, chassis, power supply
 - Loudspeaker drivers (2)
 - Wood & miscellaneous 
 - Plugs, cables, interconnects
 - 180 W Stereo power amplifier 



Woofers can be built with different drivers and in different size cabinets, but then it is not a THOR. Please do not ask me for free advice about modifying the THOR. Use the documentation as a guide and study the extensive background information in the THOR pages of the website Archive CD . Then try on your own. Let me know when you find something of significance.


Example of an assembled THOR/ORION crossover/equalizer. A DIN cable is used to connect to the +/-12 V supply on the ORION xo/eq.

Example of finished THOR cabinets with mounted drivers.


From LINKWITZ LAB you can order:  

This project is no longer supported, but worth studying for adding a sub to an existing speaker

THOR Construction Plans+
          Project documentation
          (two) w-ASP (instead of WM1 & 2-MT1)

AT1802 power amplifier     

$25      Inventory sold!
$100    Inventory sold!


THOR Construction Plans+ consist of 19 pages of documentation and two w-ASP circuit boards for adding THOR to the ORION

Each channel of the assembled THOR/ORION  xo/eq comes wired for driving a single power amplifier and for driving two power amplifiers in push-pull as when used with the AT6012. To obtain correct voltage levels for the two push-pull outputs of the xo/eq it will be necessary to clip off the leads of the jumper resistor that is mounted over R75. 
It is intended that the xo/eq will receive +/-12 V via the supplied DIN cable from the ORION xo/eq.

The AT1802 is a 180 W per channel stereo power amplifier. 
If you own the 12-channel AT6012 power amplifier for driving ORION, then its 4 unused amplifiers can be driven from the w-ASP in bridged mode to provide power to left and right THOR. No additional power amplifiers are needed.
The Peerless XLS 830500 woofer driver is no longer available. Its replacement is the Peerless XXLS 835017
The new driver has 4 ohm impedance and cannot be safely driven from bridged AT6012 power amplifiers. 
It requires a separate power amplifier like the AT1802.

Ordering information 

This project is no longer supported, but worth studying for adding a sub to an existing speaker

*DIY construction of the THOR crossover/equalizer should only be undertaken, if you have some expertise in electronic assembly, test, measurement and component selection. You may have to procure substitute electronic components due to changing inventory of vendors. Some capacitor leads may have to be bent or lengthened to fit the hole pattern on the pcb. I provide an updated Support Page with the Documentation but cannot help you individually. The ORION/PLUTO Users Group has been very helpful in solving problems and answering questions.

| Introduction | Estimates | Design | Measurement | Equalization | THOR-ORION xo |
| Supplies | SPL limits |



What you hear is not the air pressure variation in itself 
but what has drawn your attention
in the streams of superimposed air pressure variations 
at your eardrums

An acoustic event has dimensions of Time, Tone, Loudness and Space
Have they been recorded and rendered sensibly?

Last revised: 02/15/2023   -  1999-2019 LINKWITZ LAB, All Rights Reserved