MarkAudio Pensil speakers

History

In early 2009 we bought a house in New Zealand and began our plans to move there permanently. One challenge was the living room which is about 6m x 6m with a ceiling that slopes from just over 2m high to about 5m, with an open balcony at the top.

At that time my main hifi was my Ella amplifier and the B&W 802 Matrix speakers. I wanted to keep using the Ella but it was only 50W per channel and would have trouble driving the B&Ws in that size room. And even if I changed amp I was worried that the B&Ws, being ported three-ways, wouldn't sound so good at higher volumes.

So I discussed this with Mark Fenlon from MarkAudio. The largest driver he had was the Alpair 12 which would be ideal for the Ella, so he looked into finding a cabinet that would suit the room. A friend of his in the UK called Scott designs speakers and came up with the Pensil idea. It's a Damped Air Coupled box similar to speakers designed in the 1930's, when rooms were larger and amplifiers had little power.

For those that don't know, the Alpair is a single cone fullrange driver. That means that one driver handles all frequencies, from the treble down to the bass. In order to do this it must vibrate quickly (for the treble) while moving in and out (for the bass). So it has to be very thin and light while also being very strong. It's clearly much harder to make a driver of this type than a driver for more common modern speakers, which only cover a small frequency range. The big advantage is that no crossover is required, with the full signal going straight to the driver. So if it's done well, the sound created is much cleaner.

The prototype

Mark had some cabinets made out of MDF to Scott's design and brought them around to my apartment in Hong Kong. So here is a picture of the first ever Pensil speaker:

Prototype

Our living/dining room there was relatively big at 5m x 6m but with a lower ceiling and a smaller listening area. So we knew extra damping material would be required to keep the drivers more restrained, and started with 250g but later reduced it to about 180g. This was still more than was ideal for the Pensils but it showed the idea was likely to work in NZ. They sounded much cleaner than the B&Ws with a much more immediate sound and more impact.

New speakers

So I decided to have some speakers made (I didn't have the skills, tools, space or time to do it myself) and at the same time I added some rear and centre speakers for home theatre use. The centre was limited by space as it had to fit inside my existing rack. Mark decided a sealed cabinet with another Alpair 12 was the best option. For the rears I wanted to stick with Alpairs but wanted smaller cabinets. So we choose the Alpair 7s, but as they were only 4ohm (compared to 8ohm for the Alpair 12) and the room was quite large we decided to put two drivers in series in each speaker. For pure sound quality this wasn't ideal but it increased output and gave them greater power handling capacity, so was better for home theatre effects. So the final plans used were:
Note that these plans are for the metal cone Alpair 12 drivers, not the newer 12P paper cone ones which require slightly larger cabinets (but apparently sound better!).
PDF Metal cone Alpair 12 specification
I don't have plans for the centre speaker but it is 310mm wide, 240mm high and 300mm deep at the base and 270mm deep at the top, so that the driver tilts up slightly. This means it is about 13L in volume.

The cabinets were made in MDF and finished in a piano gloss burgundy red by Michael, one of Mark's friends in China. I believe it took him about seven layers of paint to get the final finish. We double checked the driver colours and chose the gold ones before finalising the installation:

Cab1
Cab2
Cab3
Cab4

Testing

Mark had another friend, Mr Chu, with a CNC machine and he made some stands for the main and rear speakers. These are in an "H" shape, cut out of brass and finished with chrome, each with four adjustable feet. The MarkAudio drivers really do need a while to loosen up and sound their best so I let them run in for a while before really testing them. It was quite easy to get a lot of hours on them as it was World Cup time so I ran the TV sound through them and listened to hifi vuvuzela's!

Room Pic

They are much clearer than the B&Ws, with vocals especially sounding very good. With piano music too you could hear the impact of the hammer on the string and the decay of the note much better. The quantity of the bass was a bit less than the B&Ws, but it was a much clearer, better defined bass.

At this point I realised I was going to have a spare set of B&W speakers so decided to make up a second system for use in our new house's dining room. I bought a Luxman L505u amp and found that the extra power (100W) really did make the B&Ws sound better. But what was interesting was that with the Luxman/Pensils combination I could hear some graininess in vocals that couldn't be heard with the Ella/Pensils nor the Luxman/B&Ws. A friend in Hong Kong subsequently bought some Pensil 12s too and he got the Luxman L590AII Class-A amp which sounds really smooth and clearly better than the L505u.

In place

In 2011 we finally made it to New Zealand and set up the speakers in the room they were designed for. Some photos are on the Home page of this site. The only change required was to remove some of the damping material that had been needed in the smaller Hong Kong room. Mark and Scott have done a great job - the speakers sound really excellent in their new home.

There is lots more information about these and other MarkAudio based speakers at the DIYaudio forum and other cabinet plans on the Frugal-Phile web page:

MarkAudio forum

More speaker plans