TL-MTM

My new speakers are of the type "Transmission Line" which means that it is a quarter wave tube which has a decrasing cross sectional area towards the mouth. It is also damped using polyester wool which is packed harder at the beginning (where the driver is) and then looser towards the throat, this combined with the decreasing x-area is lowering the speed of sound to around 310 m/s without the drawbacks of a long tube plus that you get a flow resistance at the back of the driver even below the tuning frequency = reduced cone travel and lower distortion.

The Enclosure

The X-Over

This is just a temporary x-over until I get my new digital x-over, note there are no baffle-step compensation so I have to increase the bass somewhat on my amplifier.

Measurements

As you may notice on the graphs below is there some standing waves, i will remove these by damping the walls. There is also diffraction at 8 kHz which will be removed with a peace of plexi-glass (fake flush mount). When I have added more damping and added the plexi-glass will I make some new measurements which I will post here...


Frequency curve which is a merge of 3 near-field curves and one far-field curve, the dip at 230 Hz is caused by the merge function in LoudSpeaker LAB 3 and this can be removed with the option to smooth the splice point.


The impedance curve for the system, notice the small peaks at around 120 Hz and 190 Hz this is caused by standing waves in the enclosure.


The CSD (waterfall), this is on a far field measurement, based on the same far-field curve as in the merged curve above.


And finally a sonogram which is a 2D CSD where the color show the magnitude.

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