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Tuba 60 vs. ? ?
Stipe Ercegovic:
Art Welter wrote on Tue, 30 November 2010 21:08
Stipe,
Nifty design, but it looks to roll off almost an octave above the Tuba 60 if this sim is accurate...
Yes you are right by looking at simulations seems like this...
CB-18 is designed to be "universal" bass solution (not dedicated SUB-woofer). So it can cover relatively wide freq. range even when used alone with upper cutoff freq. high enough so there is no need for dedicated kick bins.
Also idea was to improve sound quality at upper cutoff (seems that goal is accomplished successfully)
and improve cone movement stability (at extreme power) by symmetrical cone loading.
While trying to achieve this in pretty compact size extra deep LF extension is sacrificed.
By give-up from these two goals it is possible to fit longer horn path within cabinet of same size.. but than my goals are compromised.
General idea based on same lines defined as in this article by Jeff Berryman:
http://www.prosoundweb.com/article/building_a_big_woofer_enc losure/LINK
..However builders of CB-18 have reported great SPL flat from 40Hz -up .. with a bit of EQing even from 35Hz achievable (if needed ) - of course HPF @ 30Hz have to be used to protect speaker unit from over excursion damage at high power.
CBe-18 , and especially CBX-18 (I hope once it is built ) will give bit more LF extension (at cost of a bit larger cabinet size)
CB-18 is 374,5 ltr.
CBe-18 = 455 ltr.
CBX-18 = 464,5 ltr.
all dimensioned with "truckpack friendly" on mind
TUBA60 (dual 12 version) =884 ltr. in very weird dimension/size (huge depth dimension)
Also important to notice for honest comparison ..spl plot for dual 12" Tuba60 (on Bill site) is done as 2,83V on 4ohm load which is 2W/1m plot not 1W/1m. According to this even smallest CB-18 is same or more efficient from 40Hz - upwards.
OK, I must admit under 40Hz TUBA60 is still dominant.
Best wishes,
Stipe
Kevin Unger:
[quote title=Stipe Ercegovic wrote on Wed, 01 December 2010 14:53]Art Welter wrote on Tue, 30 November 2010 21:08
Stipe,
Also important to notice for honest comparison ..spl plot for dual 12" Tuba60 (on Bill site) is done as 2,83V on 4ohm load which is 2W/1m plot not 1W/1m. According to this even smallest CB-18 is same or more efficient from 40Hz - upwards.
OK, I must admit under 40Hz TUBA60 is still dominant.
Best wishes,
Stipe
The horn's resistance usually adds a few ohms to the nominal impedance, hence the upped voltage.
I don't have the T60 plans, but I'm sure this is why the measurement is done that way.
Phil Lewandowski:
[quote title=Kevin Unger wrote on Thu, 02 December 2010 22:53]Stipe Ercegovic wrote on Wed, 01 December 2010 14:53
Art Welter wrote on Tue, 30 November 2010 21:08
Stipe,
Also important to notice for honest comparison ..spl plot for dual 12" Tuba60 (on Bill site) is done as 2,83V on 4ohm load which is 2W/1m plot not 1W/1m. According to this even smallest CB-18 is same or more efficient from 40Hz - upwards.
OK, I must admit under 40Hz TUBA60 is still dominant.
Best wishes,
Stipe
The horn's resistance usually adds a few ohms to the nominal impedance, hence the upped voltage.
I don't have the T60 plans, but I'm sure this is why the measurement is done that way.
I know that Silas has measured the impedance of his LAB subs with the dual LAB12's.
But with the LAB12's having a 6 ohm impedance and with 2, bringing it down to 3 ohms. I would guess the nominal would be in the 4-6 ohm range.
I believe Bill measures all his cabs at 2.83v to keep it consistent. So with the dual LAB12 T60 just slide the response down 2-3dB and that would be around your 1W/1M response.
Take Care,
Phil
Kevin Unger:
Phil Lewandowski wrote on Fri, 03 December 2010 14:29
I believe Bill measures all his cabs at 2.83v to keep it consistent. So with the dual LAB12 T60 just slide the response down 2-3dB and that would be around your 1W/1M response.
Take Care,
Phil
Every horn of Bill's I've built has had a higher nominal impedance, Even a small 7ft horn (t39) It add to the impedance of the driver due to it having to overcome the air resistance at the horn's throat. (in a very simple explanation)
I'm curious, so I'll pickup the plans.
Hate to quote Bill's plans directly, but I think it won't be a problem. Here's a short from the t39 plans:
"Horn loading adds the impedance of the horn air column to the
driver’s nominal impedance. A single driver cab may safely be considered a
10 ohm load."
Phil Lewandowski:
Kevin Unger wrote on Fri, 03 December 2010 18:36
Phil Lewandowski wrote on Fri, 03 December 2010 14:29
I believe Bill measures all his cabs at 2.83v to keep it consistent. So with the dual LAB12 T60 just slide the response down 2-3dB and that would be around your 1W/1M response.
Take Care,
Phil
Every horn of Bill's I've built has had a higher nominal impedance, Even a small 7ft horn (t39) It add to the impedance of the driver due to it having to overcome the air resistance at the horn's throat. (in a very simple explanation)
I'm curious, so I'll pickup the plans.
Hate to quote Bill's plans directly, but I think it won't be a problem. Here's a short from the t39 plans:
"Horn loading adds the impedance of the horn air column to the
driver’s nominal impedance. A single driver cab may safely be considered a
10 ohm load."
I would definitely believe you. I think what has really been needed for the designs is publishing a impedance plot so that the person building can see what is going on. Since as you know impedance is going to change with frequency. I remember for a short time there being on impedance plot for one of the subs on the BFM forum but it seemed to disappear.
Anywho, I would be very surprised if the T60 would be actually classified as a "nominal 8 ohm load".
(Actually the Growler's average impedance is closer to 10 ohms as well, like with the T39. It just so happens that one of the "standards" is to pick the standard 2, 4, 8... as the nominal impedance; whichever it is closest to. So that is why a impedance plot is so helpful.)
Take Care,
Phil
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