Wonderful weather day here today for March 8th. 52 °F and just a light breeze. Was able to flush trim and round over all the edges. Next up is to add the open cell foam damping, then wiring up and mounting all the drivers. Not looking forward to crimping 64 push on connectors.
Last night my Son and I checked all 25 tweeters to make sure they had the proper terminal marked red for positive. A 2 second sweep with OmniMic looking at the impulse response confirmed all 25 were correct. Sorry for the blurry picture:
Got one speaker wired up last night. Wow was that a lot of work. I was hoping to take some FR and distortion measurements tonight but came home to find that my daughter is sick and is sleeping. If she doesn't get up no big deal. I'd rather her sleep and get well. I can always measure another day. No specific deadline on these unlike all of those car and motorcycle shows pretend to have hard deadlines (made up drama)
Finally got measurements done a few nights ago. I had the tweeters wired: 3 groups of 4 tweeters wired in series for 16 ohms, then those 3 groups wired in parallel for a final 5.33 ohms. The tweeters ended up 3 dB lower sensitivity than the 4 woofers, even after a full 6 dB of baffle step loss. I rewired the tweeters: 3 groups of 4 tweeters in parallel for 1 ohm, then the three groups wired in series for a 3 ohm load. That worked! Final impedance might end up kind of low but none of my amps will complain, especially since it only takes a few watts to drive these stupid loud. I questimate these will be at least 93 dB/m/2.83V.
Another note: I intially measured these at 50" mic distance so I could capture and see the BSL. There was a significant (over 5 dB) dip at 8kHz. Luckily as I moved the mic further and futher back that dip got less and less. These will need some listening distance. Hopefully at InDIYana I can move them back towards the front wall to help with that.
I'm curious: What happens to the dip on the listening axis? 8k is about 7.5 inches. Is this just a cancelation caused by woofer/tweeter spacing? Tweeter in or out might make a significant difference.
Horizontal off axis (both direction) helped a little bit. The big improvement was moving further back. I measured at 50", real world listening distance will be about 120". I'm going to remeasure at that longer distance to work on the xo sims. The 50" measurement was useful to help me determine the BSL. Projects like this force me to learn more that a typical 2 way would.
I remeasured last night at 86 inches (furthest practical mic distance). That eliminated the dip almost completely. I used those new meeasurements and worked up a very promising prototype crossover design at lunch today. Only 7 parts per side and I'm pretty sure I have all those parts on hand.
Are you doing any shading on the tweeters, or just wiring it like a standard 2-way. I have always wanted to try a small line array, but was not sure how much comb filtering would be at play.
No shading. Lots of comb filtering up close but it gets better at distance. I'll really find out once I get them both wired up and start my voicing process.
Comments
Wonderful weather day here today for March 8th. 52 °F and just a light breeze. Was able to flush trim and round over all the edges. Next up is to add the open cell foam damping, then wiring up and mounting all the drivers. Not looking forward to crimping 64 push on connectors.
very clean work, as always
the measurements will be interesting
line arrays are cool shit
You could make a pair every year and stack em
....as the years go longer, as does the array.
Got all the foam and denim damping installed on the walls. Hope they sound as bad azz as they look! LOL
Fixin' to get screwy, aren't you?
Screwy AND crimpy. 72 crimp connectors to be exact!!! Oh my aching fore arms!
It'll make you look like a teenager again . . .
You'll have monster grip strength after all those connectors!
Time for a ratcheting crimper....
InDIYana Event Website
I thought the tweeters were going to be rear mounted when I saw the chamfers.
Last night my Son and I checked all 25 tweeters to make sure they had the proper terminal marked red for positive. A 2 second sweep with OmniMic looking at the impulse response confirmed all 25 were correct. Sorry for the blurry picture:
Got one speaker wired up last night. Wow was that a lot of work. I was hoping to take some FR and distortion measurements tonight but came home to find that my daughter is sick and is sleeping. If she doesn't get up no big deal. I'd rather her sleep and get well. I can always measure another day. No specific deadline on these unlike all of those car and motorcycle shows pretend to have hard deadlines (made up drama)
You have to measure them NOW!!! Or we'll loose the shop!!!
Finally got measurements done a few nights ago. I had the tweeters wired: 3 groups of 4 tweeters wired in series for 16 ohms, then those 3 groups wired in parallel for a final 5.33 ohms. The tweeters ended up 3 dB lower sensitivity than the 4 woofers, even after a full 6 dB of baffle step loss. I rewired the tweeters: 3 groups of 4 tweeters in parallel for 1 ohm, then the three groups wired in series for a 3 ohm load. That worked! Final impedance might end up kind of low but none of my amps will complain, especially since it only takes a few watts to drive these stupid loud. I questimate these will be at least 93 dB/m/2.83V.
Another note: I intially measured these at 50" mic distance so I could capture and see the BSL. There was a significant (over 5 dB) dip at 8kHz. Luckily as I moved the mic further and futher back that dip got less and less. These will need some listening distance. Hopefully at InDIYana I can move them back towards the front wall to help with that.
I'm curious: What happens to the dip on the listening axis? 8k is about 7.5 inches. Is this just a cancelation caused by woofer/tweeter spacing? Tweeter in or out might make a significant difference.
7.5" Is below 2k, 8k is closer to 2".
InDIYana Event Website
Horizontal off axis (both direction) helped a little bit. The big improvement was moving further back. I measured at 50", real world listening distance will be about 120". I'm going to remeasure at that longer distance to work on the xo sims. The 50" measurement was useful to help me determine the BSL. Projects like this force me to learn more that a typical 2 way would.
Correct. Google did me dirty.
I have this one bookmarked for quick checks.
mcsquared.com/wavelength.htm
I am usually in the back of the room so I will have lots of company during Craigs demo.
This tool will allow you to key-in a measurement (baffle width for example) and will calculate the wavelength that will fit upon it:
https://www.omnicalculator.com/physics/sound-wavelength
I remeasured last night at 86 inches (furthest practical mic distance). That eliminated the dip almost completely. I used those new meeasurements and worked up a very promising prototype crossover design at lunch today. Only 7 parts per side and I'm pretty sure I have all those parts on hand.
Very curious to see what you come up with, Craig.
Now I have to wire up and mount all the drivers on the second speaker
Are you doing any shading on the tweeters, or just wiring it like a standard 2-way. I have always wanted to try a small line array, but was not sure how much comb filtering would be at play.
No shading. Lots of comb filtering up close but it gets better at distance. I'll really find out once I get them both wired up and start my voicing process.