Speaker design for portable devices

HiVi M4N with a TN25 and Parallax EmbeddedBlue BlueTooth Board
HiVi M4N with a TN25 and Parallax EmbeddedBlue

Speakers are surprisingly simple yet can be made very complex with the addition of crossovers, self-amplification, and source control.

At Weburban, we decided to come up with the ultimate high end mass production prototype for something that would sound good with a portable device — for example, an iPhone.

We started with a look at speakers. We needed something small in size and wide in tonal range. The HiVi M4N 4 inch midrange speaker looked like the best candidate. We coupled this with HiVi TN25 tweeter at just 1 inch. We were astounded at the optimum box size for the M4N at a mere 0.17 cubic inches.

The passive crossover circuit we used can be seen below. Basically, this high pass crossover removes low frequencies from the sound going to the tweeter. It’s passive, so no additional power is needed other than what is coming from the amplifier. The HiVi has an amazing range so we didn’t think a low pass was necessary. But that might change depending on how muddy it might end up sounding.

Simple custom crossover circuit
Simple custom crossover circuit

I used male/female 0.11. x 0.020 terminals to connect the wires together so I could swap out the crossover if it didn’t sound good. Soldering the crossover was pretty straight forward. Don’t forget to swap the positive and negative terminals on the end of the crossover.

Finished high pass passive crossover
Finished high pass passive crossover

For amplification we ended up going with an off the shelf circuit design for a Tripath battery driven chip amp. It produces amazing sound out of an amp the size of a pack of gum. Stay posted for some pictures of our really rough prototype.

HiCon iPhone application

When HiCon was on the drawing board, there was a lack of high quality black and white photography software for the iPhone. It’s pretty simple to strip the color information out of a picture. However, HiCon amplified the iPhone’s sensitivity to colors allowing the application to be used with infrared filters to turn skys black, or without filters to show harsh gradations in color as rich blacks and whites.

“HiCon was our homage to the early pioneers of black and white photography. We wanted something that had it’s own flavor without compromising the integrity of the artist taking the picture. Many professional photographers have iPhones and use HiCon as an ad hoc capture device — a trusty friend who is always there to take the decisive moment picture when the more serious cameras are away” says Weburban President and Chief Scientist Rob Newport.

The funny thing is that the iPhone is becoming a medium in its own right. It’s slowly evolving into more than just an “alternative” to a regular camera — it’s become an “alternative” to conventional camera photography. At Weburban, we are proud to be part of this exciting evolution.

Modifying a stock Porsche stereo to play an iPhone


The stock stereo for a Porsche Boxster is a Becker CDR-220, which sounds pretty awesome. Unfortunately, it does not play MP3s and barely plays burned CDs with regular audio. This, coupled with the dismal radio selection in Los Angeles has finally pushed me to consider replacing my stock stereo or modifying it to play MP3s.

Originally, I wanted to replace the head unit for a simple MP3 playing unit like the FB275BT and toss the stock stereo. But after hearing one installed I felt aprehensive since the Becker sounded so better. Also, with the introduction of Genius on the iPhone I really cannot imagine myself not using it ever again. Yes, this is a bold statement. Genius works so well for me that I would change my musical architecture to fit it.

Luckily, the Becker CDR-220 has an AUX output. The funny thing is that it is turned off in the interface by default and requires some awkward acces to it in order to connect it to a mini jack. I had previously planned to use the iPhone’s audio output in the dock connector but found out recently that Apple disabled it — possibly to prevent the iPhone from cannibalizing iPod sales. So, instead, I will be using the iPhone’s regular audio output minijack, which works perfectly for outputting audio.

The first step is making sure you have the code for your stereo should you accidentally disconnect it. Any kind of power distruption will prompt you for the stereo code. Make sure you have this before you start or you will be scrambling to get it at your local dealership, and they may or may not charge you for it.

Once you have the code, use Becker extraction keys to pull the stereo out. I ordered these directly from Becker. With the stereo out, look in the back and you should be able to see a cord of wires leading down. If you remove the side panels, you can remove the coin holder in the bottom and drill a hole in it for the 1/8 inch miniplug that connects to your phone.

You can remove the side panels by gently pulling out the edges and popping them off. The should come off with a click. I freaked out when I first took them off because it sounded like snapping plastic. But they were fine. The snap back into place when you are done. Once the side panels are off, look for catches on the CD holder and change holder and slide them out. You should see something that looks like the pictures I attached above.

Now, the most difficult part is getting fishing the wire from the head unit cavity to the change holder cavity. I used a stiff television coax cable to poke through the hole, then I taped the 1/8 inch plug to that and fished it up and out. It got caught up at some points, and I had to gently guide it through with my hand. It was a solid frustrating half hour of fishing. But once it’s through, it is much cleaner than having it dangle out the side.

Once the wire is fished from the head unit cavity to the change cavity, you need to drill a small one inch hole in the change holder to feed the wire through. This will place the 1/8 inch plug neatly in the change holder, which also makes a perfect iPod or iPhone holder. The rubberized insides prevent it from slipping around, but also make drilling more difficult. Once you have the hole in the plastic, I recommend using an exacto blade to cut the rubber around the hole to make it easier to feed the plug through.

Now, the final step is connecting the wires to the back of the head unit. You should see three rows of sockets. The middle row of sockets should be empty. To the far right, close to the edge of the head unit, you should see three rows of pins. The far right colum of pins are the left, ground, and right pins. Here, you need to either solder the pins to wires off a 1/8 inch miniplug, or buy a stereo RCA cable kit with female sockets for each pin. I recommend testing the pins with your iPhone or iPod before putting the stereo back in.

To test the unit, you need to do this last step, which will make the AUX option selectable in the front panel. Hold down TP on the face for at least 8 seconds until the option menu comes up. Move the arrows until AUX shows up and then select “on” to active it. Now, when you change your source, you should see AUX as an option. Hopefully, you will hear your iPhone or iPod crystal clear!

Also, please check out JR’s Boxster S Page for his instructions too.


Weburban brings in the New Year

A special thanks to all the folks who made last year super memorable. We have some cool new intellectual properties brewing just around the corner, and as always, we love collaborating with like-minded talented individuals.

If you are an electrical engineer, artist, or software developer with an entrepreneurial spirit please contact us for collaboration in the film, music, and imaging industry.

We require that you be located locally in Los Angeles and have the time and energy neccessary to devote to emerging technology.