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Revisiting the L7

dcibeldcibel
edited December 2018 in DIY
This is the L7:
This is a speaker I designed and built a few years back, using Hivi L6-4R and SB26STCN. It's an L6 plus a 1" tweeter, hence L7. I started this speaker as an experiment in building techniques to try a few different things, and learn what worked and what didn't. I learned a lot along the way, and in the end the speaker is very attractive IMO, but after extensive listening I was not completely satisfied with the sound.

The biggest issue with this speaker was the location of the tweeter on the baffle. Off to the side on its own isn't a real problem, but the specific location here made for a diffraction null at 3.5kHz followed by a bump at 4.5kHz, the combination of which put a shelf in the tweeter response right above where you'd want to crossover, making for a real pain in the ...


These were supposed to be a pair of smooth easy working drivers...sigh...What I ended up with was a bit of a droopy response between 1-3kHz, followed by a bump at 5kHz, and the sound was somehow a bit muddled while being shouty at the same time. This year we stayed home for Xmas, so I have some time to play with my toys, and decided to see if I can make an improvement to this speaker with only minor changes to the existing crossover.

After much fiddling, I settled on a change, while not perfect, is a great improvement, and with only one added component. I simply changed the tweeter filter from a 2nd order to 3rd order. The steeper slope removed a lot of the issue caused by the response shelf, and allowed for a workable response crossed at 3kHz.

For a before and after comparison, I took a quick and dirty measurement of the speaker pre-change, mic at 60cm, and only a 3.6ms gate since I didn't elevate the speaker off the ground. In this response there is a bump at 900Hz that is a result of the fact that I had the stuffing removed behind the woofer, a fairly significant reflection exists here. Lots of stuffing in this cab when its done, so nothing to worry about.


Here we have the "new and improved" response, one cap added and one cap moved. Less of a lump at 5kHz, and elevated response from 1-3kHz. This could of course be further improved, but would require more component changes, meaning I might as well rip apart the crossover and start over which I didn't want to do. So far I like the way this sounds and think it was worth the time and effort. As you can see there is some phase error on-axis, but this short band issue is much less awful sounding than the wide band issue and 5kHz lump that used to be there. We'll just call it a BBC dip and make like it's supposed to be there ;)





I'm not deaf, I'm just not listening.
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