After moving back into my parents house, I had no space to place my large mtm speakers. But I still wanted to listen to speakers that I had designed and built myself. That's why I decided to use the parts of my mtm's and build smaller speakers. I still had 2 woofers and two tweeters, namely: the Scan Speak 18w/8546 and the Raven R1. The choice for a small bookshelfsized speaker was easily made. These speakers were to be placed on my desk, where I do most of my studying (That's the reason I moved back to my parents, if I hadn't, I doubt that I would ever finish).
I made a quicklist of whishes (small, able to be placed against a wall and in a corner, bass). About the only way of accomplishing this that I could think of, was making a sealed enclosure and using a linkwitz transform to extend the bass. Allthough the linkwitz transform would make the woofers run out of excursion pretty quickly, I decided that that wouldn't be a problem, since my listening distance would be around 80cm anyway.
I measured the T/S parameters of the woofers, with the setup described in the loudspeaker cookbook. This gave some surprising results. Every parameter differed substantially from Scan Speaks specs. I posted a question about his on the basslist and several people confirmed that this was also the case with their woofers of the same model. So in the simulations, I used my own measured parameters, instead of Scan Speaks.
I modelled the enclosure in LspCad. I already had a target volume, and would like to see how much a Linkwitz transform could add to the bottom end of the response. Without the Linkwitz Transform, the speaker's F3 point was at 62Hz. After some simulating, I decided to bring that down to 45Hz with the transform (which adds about 6dB in the low end)
Group delay and impulse respons were still pretty acceptable, the only thing that worried me a little was the increased excursion demands. But since I have no need to play really loud, I can live with that. Besides: the linkwitz transform is an external component, so I can modify it if needed.
So I decided to draw a cabinet and start construction. Read more about this on page 2