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PC Speaker

            I wanted to experiment with those new PE speakers that just came out.

            The speaker I used is a Dayton 2.5" Aluminum cone full range.

            The previous speaker I was using was a Hivi B3N in a sealed enclosure with the Zaph Audio filter network. Since this is a smaller driver, I wanted to give it a try in a ported box. There is no simulation or calculation or whatever. I just went and designed it along the build.

            Here are some shots of the build. This is one of my screw-less/Nail-less box builds.

            I got some scrap 1/4" MDF from the shop and worked with what I have. The planned enclosure was a dual chamber ported box with a common port in the middle. I decided a 13" x 7.5" x 3" box was a good starting point with the wood I had.

(sorry for the picture quality, I was using my cam phone as I don't want to put dust into my dad's camera)

I needed uniform 2.5" wide strips of MDF but I didn't have a table saw. The solution? A band saw, Angle aluminum and some clamps!

MDF powder and offcuts starting to pile up....

Drawing the planned chambers and port on the bottom panel

I actually cut too much 2.5" strips. The long ones in the previous pics weren't used.

All panels cut and prepared:

Glued all panels except the top and front baffles

Test fitting the front baffle

Making the driver cutout on the front baffle

Using a jigsaw, I added a notch for the speaker terminals

No router? No problem!!! Using a drill press (at high speed) and a countersink bit, I removed the corner for better airflow at the back of the driver.

Not bad I would think.

After a bit of sanding to smooth the edges....

Gluing the front baffles on

A last view of the chambers with everything before gluing the last panel.

Pressing everything together

Completed enclosure

            How does it sound? I had some nasty resonance in the lower mids. I stuffed a lot of polyfill into the chambers and it seems to have helped.

            One thing though. I get a lot of IMD from the drivers. It seems the published xmax is incorrect. It does reach the published xmax but is no longer linear.

            Also, it is very directional with the highs. It sounds OK when on axis but the HF response rolls off rapidly when off axis. I will try to do measurements when I have time.

            It does produce decent bass from two 2.5 inchers (goes down to about 45Hz but only nearfield) It will be used under the laptop so it is fine.

            Power amp I'm using is an Amp32 from 41Hz powered by an 11.1V Li-polymer battery pack.

23 Feb 2011: I have measured the speaker's TS parameters using WT3 and found out that the published TS parameters in the PE page is not accurate.  Well, some of them. Here's what I was able to measure and what is published:

Parameter Published Actual
Qts 0.77 0.79
Qms 5.86 6.47
Qes 0.88 0.87
Vas 5.4 L 0.4 L
Fs 84.80 Hz 94.88 Hz
Re 3.70 Ohm 3.71 Ohm
Le 0.45 uH 0.27 uH

            It shows that the Vas in the PE page must have been a typo as it is less than 1/10th of the actual parameter. That explains the weird graph I got when I first simulated it in WinIsd. When I plugged the new numbers into WinIsd, the plot now made sense.

            I paralleled both drivers as they are in a common chamber and ran a impedance sweep to find out the box tuning frequency. Click on the image for full size view.

Box tuning is at ~48Hz.

For amplification, I'm now using the 2way xo/amp combo. This speaker box is only run low passed at 109Hz 2nd order LR. I'm using a pair of unknown 1" drivers for the HP outputs. Highs sound much nicer than these 2.5's.

Page updated and copyright R.Quan © 23 Feb 2011.