Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

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Grant Bunter
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#16 Post by Grant Bunter » Thu Feb 11, 2021 4:55 am

Krillin wrote:
Wed Feb 10, 2021 9:59 pm
The guy at speakerhardware did state he had a lot of orders which is fine.
Leland is the owner of speakerhardware. Leland is a forum member, authorised builder par excellance and helps a lot of us out with some harder to source bits and pieces.
He won't be fibbing if he says he's busy.
Krillin wrote:
Wed Feb 10, 2021 9:59 pm
What would be the impact of enlarging the baffle by an inch and using a single AE TD6M-4 with my Transducer Lab N26MGR-G? Is the MTM crossover compatible with a TM?
Bill will need to answer, but that would require a redraw of the design as well.

My thought is that modifying the/any part of Bill's design(s), which is based on TS parameters of the recommended drivers, immediately makes cabs a lottery. Crossover points may need redefining, meaning changes in the filters themselves.
Performance then becomes an unknown quantity.

The age old adage here, is follow the plans to get expected results.
Hope this helps...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#17 Post by Bill Fitzmaurice » Thu Feb 11, 2021 7:53 am

Rule #1: Follow the plans.
Rule #2: Never break rule #1.

Krillin
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#18 Post by Krillin » Mon Feb 22, 2021 5:26 pm

Well good news Leland has started my flatpacks :)

Bill, is there a published impedance/phase graph for the David with the recommended drivers? Also, the plans state that the mid-bass driver crosses at 3khz and needs to be 8-ohm 90db+. Assuming that there is no breakup how much of a rise is allowed above the crossover point? I am looking at a 8-ohm drivers with a FR like below:
SKDM.PNG

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Bill Fitzmaurice
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#19 Post by Bill Fitzmaurice » Mon Feb 22, 2021 10:15 pm

I don't have graphs. Those drivers don't have a severe enough break up to be a concern, but crossing over low enough to avoid the break up mode is only half the reason for where the crossover point is. The other is off-axis response, which at even 3.5kHz is much better with a tweeter than with a four inch midbass.

Krillin
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#20 Post by Krillin » Sat Feb 27, 2021 8:13 pm

I was asking impedance questions only because I have both solid state and tube amplifiers. And more importantly I intend to add a SE tube amplifier to the mix. Thanks Bill

There is one last question. There is a 95db tweeter I am looking at with a stated 6-ohm impedance but on the graph drops down to 5 ohm then above 10khz starts rising to 6 ohm. Will this be a deal breaker?
N28be.PNG

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Bill Fitzmaurice
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Re: Tuba 18, David, Table Tuba 8" subwoofers. Best choice?

#21 Post by Bill Fitzmaurice » Sat Feb 27, 2021 10:15 pm

Impedance is not a set figure, it's an approximation based on the minimum impedance, which equals DCR, which may be as low as the 0.7 times the impedance. A six ohm driver may have as low as 4.2 ohms DCR.

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