resonance and sealed enclosures

A port is typically tuned at the point of resonance that the woofer achieves within that given box. By "counter-acting" this resonance, two smaller resonances are created. It is this elevated bass plateau due to these resonances that typically results in greater extension. At the same time, more resonance equates to less control and definition, which is why most vented designs sound "sloppy" compared to a well designed sealed box. The sealed box loses when it comes to output levels though, so you have to choose which trade-offs you want to live with and go from there. As i've mentioned before, sealed vs vented is equivalent to quality vs quantity.

I don't think that a 10" sub would be out of place filling in the bottom for 5.25" mid-woofers. If you cross it over properly, you can play around with the placement and probably get it to work pretty well. As far as using it on a desk-top, that may be a bit much depending on the size of the cabinet and the size of the desk : ) Sean
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I have read a revuew about a similar setup from M-Audio, slightly more expensive, that features an 8" ported sub. The complaint is that the sub sounds right at middle volumen levels but is too weak at high volume levels and too strong at low volume. Is this a classic case of the type of distortion that is found when using ported subs?

This has to do with port velocity and turbulence within and / or near the port entrance and exits. Using a port that has radiused flares tends to reduce these problems quite a bit. This allows the port to maintain more consistent tuning / proper operation over a wider spl range. If such a port is not used, the output of the port will be far peakier in a specific spl range and lower the performance standard if used outside of a narrow range of average spl's. Using a port that is flared on one side rather than at the inlet and the outlet is better than a straight port, but it will still run into the same problems, albeit to a lesser extent. Sean
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Sean...We know how you feel about vented speakers, sealed speakers, and even TL, but what is your take on the resistive vent, such as used with great success in the old Dynaco speakers? I tried this once with a box that was a trifle too small for the driver, but didn't see much effect, good or bad.

El: I don't have a lot of personal experience with this type of design as compared to others that i've discussed, which for the record, is called an Aperiodic or "Vario-Vent" by some. From what i have heard, experienced and read about these designs, i like it better than most commercially available ported and passive radiator designs. Like anything else though, one would have to carefully select the proper box / driver combo to obtain optimum results.

As a side note, there was a commercial speaker designer that was posting on AA under the pseudonym of "Mr Bigglesworth". Whoever he was, he wanted to remain anonymous but at the same time, tried to share his experiences and educate the masses. When it came down to it, he stated that if one were do all of the measuring in the world and their goal was to achieve the highest levels of linearity possible, a sealed and stuffed low Q box would be what they would end up with. I asked him what his thoughts were on Aperiodic's and Transmission Lines and he referred me back to the sealed box along with an explanation why he had those thoughts. Given that i was already on the same page that he was, i didn't need much convincing. I was just looking to compare notes with someone inside the industry that didn't have a reputation to uphold or specific product to market. Sean
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