Building a pair of DML speakers

I have always been fascinated by loud speaker technology.  I have owned several pairs of speakers over the years, but all of them have been conventional cone speakers.  I fell in love with the flat panel speakers the moment I saw them, be it Martin Logans or Magnepans.  I never owned one though.

I recently stumbled upon a new type of speaker technology.  It is called Distributed Mode Loudspeaker (DML).  It was fascinating to see how simple it was yet how incredible the sound reproduction was, based on the reviews online.  I watched a few youTube videos on how to build one and read a few online forums for more info and got ready to build one.  Here is an account of how I built two pairs of the DML speakers and how they turned out.

The DML speaker is built out of a flat panel made of a light but stiff material and an exciter.  The exciter is like a speaker without the cone.  This exciter vibrates the panel to produce the sound output.  The DML speaker is unlike any cone speakers or flat panel electrostatic (Martin Logan) or magnetic ribbon (Magnepan) speakers.  The DML speaker randomly generates vibrating nodes that translate into sound output in different frequencies and amplitudes.  Due to its nature, it generates equal sound both from the front as well as the back of the panel.

The first speaker is a 2'x2' flat panel speaker made out of:
- 2'x2' (1" thick) Foamular XPS insulation board (Home Depot)
- Dayton Audio DAEX25FHE-4 24W exciter (PartsExpress)
- Gorilla wood glue
- Speaker wire
- Solder

That is it!

I rounded the corners of the board with a 3" radius.  Rounded the edges as well and removed all sharp edges.  Sanded the entire panel with 110 grit sandpaper using a orbital sander.  Applied a 1:1 mixture of wood glue and water to the entire surface.  Once dry, I applied the second coat.  This produced a sandpaper kind of finish which is what makes it an amazing sound generator.  Attached the exciter 2/5th from the top and side.  Soldered the speaker wire to it and I was done.  Check out the youTube video for more details on the steps and the reasoning behind them. 

Rounded corners.

Ready for prime time!

I hooked it up to the amp and was amazed by the sound it produced.  I was not expecting this big of a sound stage from such a small (and inexpensive) exciter.  Because of the wide panel, there is no sweet spot like with conventional speakers.  High frequency is a bit pronounced due to the size of the panel.  Imagine a tweeter the size of the panel!  It acts like that.  But, the sound stage is incredible.  I have the speaker placed about 8 ft from the back wall and 1 ft from the side wall.  Maybe the distance from the back wall as well as its omni-directional nature, the sound stage appears to be behind the speaker.  This works great for me when watching movies since the screen is far behind the speaker.

Once I completed the first test speaker, I was ready to build the larger one.  I wanted to see what effect the larger panel would have.  Boy, was I rewarded.  The larger panel had a more flatter response.  Better mids, lower highs.  I am still breaking it in.  Hopefully, it will get better as it ages.

I used the same process for building this speaker as well.  Below are the parts used for the larger speaker:
- 4'x8' (1" thick) Foamular XPS insulation board (Home Depot)
- Dayton Audio DAEX32EP-4 Thruster 32mm Exciter 40W (PartsExpress)
- Gorilla wood glue
- Speaker wire
- Matte spray paint
- Solder

This exciter is the bigger brother of the previous one and there is a marked difference in quality and sound reproduction.  It is also heavier and bulkier.  The only problem with this foam board is that it is scored to make it easy to break it into pieces.  I was afraid that the score lines would create unnecessary vibrations and hence I poured glue into the cracks and sealed them.  I was a bit over zealous and ended up with awkward looking glue lines in the speakers even after sanding them.  Lesson learned.  I would take a fine tube and just squeeze the glue into the cracks and wipe off any extra.  This will keep the surface clean looking.  From this large board, I was able to cut out 2 20"x44" pieces and I am still left with half of the board.  Is 20"x44" the golden ratio?  Absolutely not.  It is not even close to the bronze ratio (if there is such a ratio).  I had to choose between great sounding speakers and good looking speakers.  I chose to compromise and go for good looking ones in order to make sure I could keep them "inside" the house and not in the garage collecting dust. 

I followed the same procedure as earlier to prep the boards, paint them with glue to generate the sandpaper-like surface.  Once the glue dried, I painted it gray with the matte spray paint.  I attached the exciters using the same formula (2/5th) and soldered the speaker wires.

Cutting the corners with a knife.

Filling the scored cracks with glue.

Painting it with 1:1 glue-water mixture.

Panel is ready for testing.  The ugly lines are the scored lines where I applied glue.

Big brother with the younger brother, before the final paint job.

A-B testing.

I also took this opportunity to design and build a pair of stands for the speakers.  I went to Home Depot and bought some poplar boards of different sizes.  The design is a simple inverted T supported on the back by a beam.  I cut the wood to the desired size put the stand together with one screw.  I then coated it with polyurethane to protect it.  I bought dual-ended gold speaker binding posts from PartsExpress and affixed them.  I use one end to connect to the amp and the other end to go to the speaker.  This allows me to disconnect the panel from the stand for transportation or storage.  It also lets me switch panels on the same stand.  I attached soft foam for the bottom and back support so that the speaker is not touching any hard surface.  I used a soft multipurpose cleaning sponge to create these supports.

The final product.

Back supported by a soft sponge.

Dual-ended speaker posts.

I did not expect the panel to reproduce the entire range of frequencies from 20 Hz to 20 kHz.  The smaller panel has pronounced high frequencies whereas the larger panel is well balanced.  The smaller panel lacks mid freq response.  It completely lacks low freq (below 150 Hz) response.

As seen in the youTube video, I think making panels with 2-3 different materials and using a crossover will give the best full range speaker.  I am happy with the results so far and am going to enjoy these speakers for the time being.

Here is the final setup.  The speakers were moved into the room to fit in the picture:

Here is a demo of how the speaker sounds.

The larger panel is better at reproducing mids whereas it also lacks low freq response.  I had to pair it with a sub-woofer to take care of 20 - 150 Hz.  Overall, I am very satisfied with the build.  It was a fun experiment and a great DIY speaker to show off.

Eindhoven GLOW Festival

Eindhoven, a city in the Netherlands, hosts an annual light festival called GLOW.  Eindhoven is known as the City of Light, mainly because of the fact that it housed several match stick factories.  And, then Philips established its light bulb factory. 

I was lucky enough to be in town to experience GLOW 2014.  It was a fabulous experience and some of the installations were mind-blowing.  The city had spent considerable amount of resources to put this project together.  The entire project spanned over 20 installations spread around the city center (Centrum, as they say in Netherlands).

The installations were in the form of light installations, sculptures, projections as well as live performances.  Some of the installations were elaborate and involved high-tech equipment. The entire 'show' started at 6 PM and went on into the night. 

One of my favorite installations was the 'Parklaan Flashback'.  This installation captured the history of Eindhoven at the beginning of the twentieth century.  The show was a light projection on two buildings facing each other.  Spectators stood between the two buildings and watch the show.  The show is synchronized between the opposite buildings and moves from one building to the other.  Different scenes are depicted and 'painted' on the buildings using light with accompanying music.  It made for a spectacular show.  I shot both video as well as still images.  Here are a few of the still images:

The 'Pendulum Wave' was a piece of art built on the principles of pendulums.  This was a great engineering installation with 15 pendulums of varying lengths suspended from a frame.  At the end of each pendulum was a lighted ball.  All the pendulums were simultaneously raised to the side (I guess, using electro-magnets) and then let go.  The pendulums formed interesting patterns governed by their lengths.  As the pendulums swung, the balls would change color.  The entire experience was enhanced with music and fog.

The 'Figures that Wander' was a shocker amongst all the exhibits.  This was the only 'live-art' in the whole festival.  The performance involved four dancers dancing behind semi-transparent plastic curtains.  They formed shapes using light and shadows.  Initially, I thought that this was a projection onto a semi-transparent screen, just like all the other installations.  After watching for a few minutes, I realized that this was indeed live, and there were people performing behind the screens.  This was the most creative, bold and provocative art installation in the entire festival. 

The 'Enchanted Cathedral and the Seasons' was an innovative art creation using high powered color projectors.  Computer generated images are projected onto the façade of the cathedral to depict the four seasons.  Again, the animation was accompanied by lively music.

Here is a view of the cathedral from my room.

'Stereo' was the video mapping projection done on the façade of the Augustijnenkerk cathedral.  This cathedral was right next to my hotel and I could see it from my window.  This audio-visual production transformed the cathedral into a living and moving structure.  Set to music, the high powered projectors painted the façade with features and made the features undulate to music.  It was an interesting way to convert an irregular surface into a projection surface and paint pictures. 

There was another show inside the cathedral.  Even here, they had used a half dozen synchronized projectors to project images onto the tall ceiling as well as the walls of the cathedral.  I was surprised to note that each of the projectors was using film instead of digital technology.  The entire show was cued to baroque music.

All in all, it was an amazing experience.  I heard that other European cities are also hosting such GLOW events and I can't wait to visit them and experience GLOW again.

Airport Design

I was looking at the airport terminal maps on a recent flight for various international airports and noticed that no two airports looked similar. I had to figure out a way of transferring between two terminals in SFO in the shortest possible time. Only after I ran through the airport did I discover that I had to go through airport security once again, even though I was just changing planes! That is when I started thinking about airport designs.

Why isn't there a standard airport terminal design that is optimized for airplane traffic as well as passenger traffic?

Airports have been around for quite sometime and there are hunderds around the world. A lot of thinking goes into airport design such as environmental concerns, reuse, use of natural light, efficient heating/cooling, etc. I have seen several contemporary airport terminal designs, each expressing their own style and culture.

But, what is surprising is the fact that the terminal maps and the runways are different in every airport. I had imagined that studies had been conducted and standard designs would have come out of optimizing the operations of an airport. Most airports are built upon a rectangular patch of ground. Of course, some airports will have certain constraints, but none too great to not use a standard, efficient and proven layout.

I am all for unleashing ones creativity when it comes to the cosmetic design of the terminals. But, when it comes to efficient design of the runways, taxiways as well as the terminals, there needs to be a study conducted by an operations research scientist. I am sure someone has already done this, but I fail to see it in use anywhere.

Blogs, blogs, blogs...

Why do I blog?
Why do I read blogs?

These are some of the questions I had to answer when I was trying to introduce a friend of mine to blogs (believe me, there are still a few who are yet to be exposed to blogging). I had to think a bit before answering these questions.

Why do I blog?

First of all, let's define a "blog". Blog stands for 'weB LOG'. An online dairy of sorts. As per Webster, it is "a Web site that contains an online personal journal with reflections, comments, and often hyperlinks provided by the writer". Wikipedia says "a blog is a website where entries are made in journal style and displayed in a reverse chronological order".

Blogs have come a long way from the initial online personal diary. I got introduced to the 'online diary' concept by Philip Greenspun of photo.net and Joel Spolsky of JoelOnSoftware. Philip is a great photographer and my interest in photography drew me in. His Travels with Samantha series captivated me as well as his other entries on technology. Joel wrote about the business of software, and related technology topics. Of course, there are many more who had online public journals even before 'blogging' was officially recognized. I was fascinated by their thought process as well as writing style. I always wanted to, one day, have my own blog and publish it.

With the advent of technology and tools/services that made blogging so easy, I got my chance to publish my own content.

I started blogging for the primary reason of sharing my thoughts with like-minded people. It also served as a daily/weekly/monthly assignment which helped improve my writing ability. It has now morphed into a showcase for some of my art. It has helped me connect with like-minded people from all over the world.

Blogs come in all shapes and sizes. There are blogs that share ideas, thoughts, commentaries, opinions, etc. Blogs that give a face to a (faceless) company. Blogs that just plain try to get hits (see Blog Pimping) in order to make money. Blogs that report the latest news, be it politics, happenings, technology or gadgets. Due partly to citizen journalism, blogs are becoming a source of news (and rumors?).

People blog for a variety of reasons, some of which are:
- Just because you can do it (there is nobody editing your content before publishing)
- To spread useful (or useless) information
- To share ideas
- To teach
- To make money
- To connect with like-minded people
- To get exposure (I blog, therefore I am)
- To expose one's mind (via sharing thoughts and commentary)

Why do I read blogs?

The answer to the previous question partly answered this question too. I read blogs to get information, learn new things, to connect with people, to get into another person's head. Blogs have been a great source of information as long as you know what to read. Where would a school kid sitting in a remote corner of Srirangapatna get a chance to get into the head of a CEO on an almost daily basis? Thanks to blogging, this has become a reality.

There are millions of blogs and there are only a handful that have any useful content. In today's world of Ads where every pageview counts, there is tremendous competition to get new content into blogs and keep it interesting. It is a lot easier to start a blog than to maintain one.

Once you start following a few blogs, you will discover that there are a lot more that are interesting, and that some of them are very active. How do you know if a blog content has changed? Do you visit them daily to check for changes? That is almost impossible. Here comes RSS and the feed readers. Feed readers help you subscribe to blogs and get notified whenever the content of a particular blog changes.

The fact that you are reading this blog means that you are familiar with blogging. Go ahead, and explore the wonderful world of blogs.