Category: Orion

The Analogue Signal Processing filter (ASP) of the Orions is a separate Printed Circuit Board (PCB). As the signal is not yet amplified and doesn’t at all depend on the amplifier/filter/driver/speaker interaction, you can build and test the filter separately. A PCB can be ordered directly from Linkwitz, but I thought it would be nice to make it myself so that I could fit all five in one casing. I hadn’t designed a PCB before but with the help from our electrical engineer at work I managed. I used the PCB design program Eagle to first draw the circuit and then place the parts on the circuit board. Eagle can add the routes between parts automatically, but I wanted to do that myself as well. As an extra cumbersome challenge, I wanted to have all routes on one side only. I suppose this added to the general idea of solving an intriguing puzzle. With the electric scheme that came with the plan set it was little more than connect the dots and paint by numbers to make the PCB work.

This is the signal route side with the locations of all the parts. This is really a complicated design especially compared to my old speakers that have only two filter components total (the midrange driver isn’t even filtered). The theory behind the filtering is all explained in wonderful detail on the Orion Website with a nice decomposition of all the ingredients and their complex (i.e., not real) gain and phase transfer functions. I designed this PCB with all parts fairly close together. I started by ordering a single test board that was error-free and sent my order for 5 revised boards priced to Eurocircuits; they sent me six.

Here are the boards fully loaded. As I ordered enough parts for the 6 boards and one test board, I decided to load them all should one fail completely. I found soldering all the parts in place quite calming.

I tested all the boards and they all worked fine; I had a bit of stray solder short-circuiting one board (nasty burn) but that was quickly solved. These are measurements of all boards showing the transfer functions of the gain for the three frequency ranges and this is what they are supposed to look like. They are nearly the same, quite surprising given the few percent of uncertainty in the value of capacitance and resistance of all components. The current boards are Orion version 3.2; the Orion and its ASP received a few updates over the years that are not yet implemented.

The boards were placed in the casing of an old Rotel amplifier; the height of the amplifier actually determined the maximum width of the PCBs and precluded the use of the standard PCB (the reason I made my own PCBs). I first asked the Rotel importer if I could have a Rotel casing, but they scorned at this indecent proposal. So I watched the second-hand market until I found a defective amp that was disembowelled. The rear panel of the amp was replaced by a sheet of brass hammered into shape and supplied with a very large collection of holes, plugs, sockets and connectors. The colors indicate the channel (ring) and the driver (red/blue/green for bass/midrange/tweeter).

Note that there are five large connects top-right by Speakon; these can be fitted to a speaker cable with 8 cores. I choose to have the pre-amplified signals run to all amplifiers, collect all the amplified signals back to the filter cabinet and move them internally to the Speakon connectors for an easy connection. This way the ASP cabinet and three amplifiers form one block with only five preamp signals and five Speakon connectors to disconnect when moving the gear. The complicated business of sorting out how to hook up the speakers is now simplified making the filter casing a ‘black box’.

A view of the inside of the filter with the power supply bottom right, the signal cables to and fro the filters top left and the amplifier cabling bottom left. After all the connectors and plugs and sockets were placed, the rear panel sprayed black, and the soldering completed—taking well over two days—I ran another test of the signal boards. It took some time to work out how to measure the ASP performance with a program called ARTA (meanwhile this is a few years later after finishing the filters) but after the right settings in Windows were found all the characteristics returned nicely. More than fifty cables running on the outside of the filter were made.

Sub project complete!

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Introduction
The plan
Design changes
Signal processing
The listening room
Production
Listening

The construction of the Orions can be quite easy if you buy all the components and parts but you can also choose to buy the plan set only and do the rest yourself. This is one of the many appealing characteristics of the Orion but the drivers of the loudspeakers are very expensive. We were planning to expand our living room so I knew I had some time which ended up being over four years. As I wasn’t in a particular hurry I decided to do everything myself. This included designing my own circuitry and making my own cabinet from self-made panels. The trouble was that I had no experience in either electronics or woodworking so I knew I was in for a learning curve than might become uncomfortably steep! I decided not to be held up by these distracting facts.

Fortunately, the Orion is an active speaker. This means that the amplified signal from your receiver is not sent to your speaker to be distributed by a filter in the speaker for the low, mid, and high-range drivers; the signal is first split into one frequency range for each driver, amplified separately for each driver, and only then sent to the speaker with one speaker cable per driver. You could see the subwoofer as an active speaker as they nearly always have their own amplifier, but that is merely a self-powered speaker; there is not frequency filtering going on (a low-pass filters perhaps). Articles on the advantages of active verses passive systems can be found on the net and I’m not qualified enough to start lecturing. A clear disadvantage of active speakers is the cost of the amplification.

An active system needs to first filter the signal between that part of the receiver that processes your signal and the horde of amplifiers. There isn’t a single piece of equipment that can do that, so you need three; the incoming signal is handled by the so-called pre-processor, you then use the filter and the amplification is performed by separate amplifiers. Most audio systems have the filtering in the speaker; the pre-processor and amplifier are joined into a single receiver, or two ‘separates’, when you have two pieces of equipment performing the same function. Audiophiles will argue that such a system of ‘separates’ is superior to a receiver, but if you put separates into a new single casing nobody will know, right? Most receivers can work as a pre-processor, having the pre-amp out connectors for low-voltage signals to be amplified later, but then you won’t be using the amplifiers in the receiver which is wasteful. A dedicated pre-processor, without amplifiers, is typically twice as expensive as a receiver or more. This is probably due to the cost of leaving out the amplifiers. Then you need to amplify four channels per speaker; normally you need only one.

Separate amplifiers can be bought everywhere but I wanted to be prepared for a 5-speaker setup, meaning 20 channels and that is an absurd number for normal home systems. Fortunately I was able to buy a stash of Rotel RSP-1077 amplifiers, fitted with 7 channels of 100 Watts each, more than enough for the Orions. Next to being very small, they are also very efficient. These Rotels use the Bang & Olufsen ICE amplifier modules that B&O use for their own active speaker. I now have 21 channels, leaving one channel unused, using the space of a some stereo amps. I don’t really need to have 100 Watts standing by for each channel except for the bass drivers, but there aren’t many multi-channel amplifiers with lower power outputs.

NEXT

Introduction
The plan
Design changes
Signal processing
The listening room
Production
Listening