CBT36 clones .. sort of

[rhubarb9999]

Re: CBT36 clones .. sort of

I already have some pretty serious EQ going on with the DCX. I am crossing my mids much higher than the real CBT36 .. but the Aura driver is more full range than the ND91. I also cross to the woofers higher since the Aura wont go as low as the ND91. I would not consider my array usable without a woofer of some sort (not a sub).

I plan to do the shading at some point. This project has been moved to the side for now.

[[email protected]]

Re: CBT36 clones .. sort of

Very nice curved arrays, for the smaller amount of money spent on them. Of course, there are a few reasons why the CBT36 speakers are done differently, but without the spare change to afford the more upscale drivers, this looks like it's probably a decent solution.

Also, as Don will tell you, there are line arrays and curved arrays, but not all line arrays or curved arrays are CBT arrays -- the shading is part of the 'special sauce', and then corrective filters in the processor come along and flatten the response by reducing output in the midrange and upper bass to restore flatness (as the CBT Legendre Shading technique results in sloping treble response). If you implement both these measures (which are well documented) then you'll have a true CBT array.

[r-carpenter]

Re: CBT36 clones .. sort of

Very nice work!
I see that you have a straight array behind the curved one. Could you talk about the imaging differences and the size of the virtual image on these?
Also, have you tried or planing in the future to RTA the in room response?

[Wolf]

Re: CBT36 clones .. sort of

What's the cc of the tweeters.

Like, 5/8", in the kit form.
Wolf

[raiderone]

Re: CBT36 clones .. sort of

I did not notice much comb filtering with just the mids playing. The curve helps reduce this. With a good bit of EQ, the mids can sound OK .. but the tweeters really help.

Thanks.

[raiderone]

Re: CBT36 clones .. sort of

Comb filtering would not allow any kind of decent treble response from the mids only. Now- if the drivers had an inherently rising response up to and past 20Khz, then it could possibly comb-filter the response back to flat destructively. I have seen this happen in one instance, and it was not bad.

Later,
Wolf

And which array was that if you remember?

[Dewmiester]

Re: CBT36 clones .. sort of

What's the cc of the tweeters.

[rhubarb9999]

Re: CBT36 clones .. sort of

I did not notice much comb filtering with just the mids playing. The curve helps reduce this. With a good bit of EQ, the mids can sound OK .. but the tweeters really help.

[Sydney]

Re: CBT36 clones .. sort of

I followed the link to this thread from another about the CBT36.... I was wondering if you listened to just the mids array (tweeters off) and if you did what did it sound like? I ask because there are other threads about using only 3" drivers and sounding good, but none of them were curved, well actually one or two were curved but "concave-ly."

Visualize that the distance from the drivers ( reproducing the same signal ) to your ears will NOT be the same, and it become apparent that the sound produced by the more distant driver will arrive later.
In classic engineering texts* this is often represented as an integration of multiple trigonometric relations.
The result is summation that produces lobes.

* One example is Sound System Engineering
By Don Davis, Eugene Patronis

[Wolf]

Re: CBT36 clones .. sort of

I followed the link to this thread from another about the CBT36.... I was wondering if you listened to just the mids array (tweeters off) and if you did what did it sound like? I ask because there are other threads about using only 3" drivers and sounding good, but none of them were curved, well actually one or two were curved but "concave-ly."

Comb filtering would not allow any kind of decent treble response from the mids only. Now- if the drivers had an inherently rising response up to and past 20Khz, then it could possibly comb-filter the response back to flat destructively. I have seen this happen in one instance, and it was not bad.

Later,
Wolf

[raiderone]

Re: CBT36 clones .. sort of

I followed the link to this thread from another about the CBT36.... I was wondering if you listened to just the mids array (tweeters off) and if you did what did it sound like? I ask because there are other threads about using only 3" drivers and sounding good, but none of them were curved, well actually one or two were curved but "concave-ly."

[rhubarb9999]

Re: CBT36 clones .. sort of

I did groups of 3 or 4 drivers (19 total) in parallel and then tied the 5 groups together in series. On an Ohm meter I get about 12 Ohms .. so in reality its probably as 16 Ohm load on the amp.

[basketcase]

Re: CBT36 clones .. sort of

Could you explain how you wired the auras? I have a case and have been trying to figure out how to get to them close to an 8 ohm load in an array. Thank you.

[rhubarb9999]

Re: CBT36 clones .. sort of

The drivers are all rear mounted. I used hole saws to cut the circles (I'll find the sizes). The woofers are a nice tight fit. They have a little lip around them that fits perfectly in the hole and seals them up. The tweeters were a little trickier. What I did was glue a bottlecap to the front of one tweeter that was the exact size of the hole. Then I put this template (more of a jig actually) into each hole and drilled the holes for the screws. Then replace the jig with a real tweeter and put in the screws. Everything lined up nicely. I just used regular gasket tape for the baffles. I marked up the baffles and drilled pilot holes while the baffles were flat. Then I temporarily screwed them to the cabinets to cut the driver holes. A CNC would be MUCH nicer but doing it by hand was not bad. I took me about an hour per baffle to cut the driver holes.

I would be interested to see what you come up with for shading and a passive crossover. I would love to get the tweets and mids to be xover-ed passively and then actively cross to the woofers. Then I could use a Mini-DSP for the system and free up my DCX for other projects.

[duanebro]

Re: CBT36 clones .. sort of

I love it! Glad to hear that you like them so well. Any problems getting the drivers or baffles to seal? What did you use for gasket material? I'm going to build the same thing at some point this summer. Only I think I will try to shade them and use a passive xo... Still with eq though. How much of a PITA was it to cut all the driver holes? I have thought of getting mine done at my college FAB Lab CNC router. Not sure of the cost - they never seem to charge me.

They look great!