Initial cbt36k measurements
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Author:  brombo [ March 4th, 2017, 3:02 pm ]
Post subject:  Initial cbt36k measurements

Finally have cbt36k together and working. Measured near field response (measurement location suggested by Don Keele) of left and right speakers with miniDSP configured for "flat" output response. 1/12 octave filter on measured data. Measurements made with miniDSP Umik-1 usb mic and REW software. cbt driven by 4-channel emotiva XPA gen3 amp. Subwoofer is off.

cbt36k_measure.jpg [ 216.54 KiB | Viewed 15586 times ]

cbt_RL_flat.jpg [ 59.72 KiB | Viewed 15586 times ]

Author:  Pelliott321 [ March 4th, 2017, 5:16 pm ]
Post subject:  Re: Initial cbt36k measurements

Not a bad room response. Curious upper mid range lower highs ther is a broad hole. I'm sure that correctable with the DSP

Author:  brombo [ March 4th, 2017, 5:35 pm ]
Post subject:  Re: Initial cbt36k measurements

I sent the curves to Don Keele. I waiting to see what he suggests.

Author:  SoundMods [ March 4th, 2017, 5:44 pm ]
Post subject:  Re: Initial cbt36k measurements

So -- wait for it -- do your speakers bend over backwards to please you? :crazy:

Author:  brombo [ March 4th, 2017, 6:16 pm ]
Post subject:  Re: Initial cbt36k measurements

I also belong to punsters anonymous. I will say that the enclosures curve make them as rigid as any enclosure I have ever seen and there is additional internal bracing.

Author:  brombo [ March 5th, 2017, 9:54 am ]
Post subject:  Re: Initial cbt36k measurements

Don Keele's suggestions which I will try -

Hi Alan,

Thanks for the curves! They don’t look to bad except for the differences between 1 - 4 kHz. I would suspect that the differences are due to left-right differences in room setup and environment and not speaker differences. To check this, just re-measure the left speaker in place and then simple swap the left and right speakers and measure the right speaker in the left’s position and see what happens.

Also here’s something else to try. Measure again an overall curve of the left speaker in the left position and then flip the polarity of the HF and then measure again (I hope you can just reverse the wires at the amplifier because you can’t do it at the speaker end with the Speakon connector or reverse polarity in miniDSP!).

With polarity reversed you should get a decent response null at crossover. If not, you can twiddle with HF delay (was 0.17 ms) to make the null sharper. This ensures that the LF and HF responses are fully in phase at crossover (a good thing!).

Also measure respectively the LF and HF responses (turn amp channel down or mute in miniDSP?). This will show the separate crossover LF and HF curves.

Thanks for taking these measurements!


Best Regards,

Don Keele

Author:  Jay Bala [ March 11th, 2017, 11:18 am ]
Post subject:  Re: Initial cbt36k measurements

I like this kind of setups, especially for subwoofers. Morel makes a 6 1/2" base driver with a sort of a line approximated circular shaped large dust cap, when you string lots of them in a line the "system" goes down to 14 Hz -3 dB. Yes, each driver Fs is in the 30 or 40 Hz region. The one I had listened to was a side firing with 16 on either side. Exceptionally clean and low distortion. Very powerful in the ultra low sub-region and you felt it in an overwhelming way.

16 drivers on either side, totals 32 drivers equaling three 18" subs and no 18" driver is going to keep up with a 6 1/2" driver. And its clean up to 2kHz, but it was xo over in the 80 to 120Hz region.

After the 12" sub I am trying to build, I will have to do one of this once I get some technical articles on it to get the science right.

Author:  TubeDriver [ March 11th, 2017, 11:23 am ]
Post subject:  Re: Initial cbt36k measurements

They sure look cool!

Author:  brombo [ March 11th, 2017, 11:37 am ]
Post subject:  Re: Initial cbt36k measurements

I am building a second parts-express 18" subwoofer identical to the one already in the system and then will configure each cbt36K and subwoofer as a full range speaker. This was suggested by Don Keele.

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