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Author Topic: Tuba 60 vs. ? ?  (Read 20165 times)

Art Welter

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Re: Tuba 60 vs. ? ?
« Reply #10 on: December 04, 2010, 12:04:27 pm »

This thread has Silas impedance plot of a Lab sub:

http://srforums.prosoundweb.com/index.php/t/59824/19717/

Even if you take the “average” approach, I think 4 ohms as a nominal figure would be about right.
The T60 would have a different impedance plot, but the minima and maxima probably would be similar.
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Ivan Beaver

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Re: Tuba 60 vs. ? ? Spec numbers
« Reply #11 on: December 04, 2010, 01:57:20 pm »

Phil Lewandowski wrote on Fri, 03 December 2010 21:56

(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



You are exaclty correct.  You cannot describe a complex number (such as impedacne) with a simple single number).

You would not believe how many people have no idea how impedance and wattage and voltage are related.

If a loudspeaker had a published impedance of 10 ohms (or any other number than the "standards") you would see a WHOLE bunch of questions like "My new speaker has an impedance of 10 ohms-I can't see that rating on my amps spec sheet-what kind of amplifier drives a 10 Ohm load?".

I'm not kidding.  But if the same exact loudspeaker was rated at 8 ohms-there would be no questions Rolling Eyes Even if there was a published impedance curve of the loudspeaker that SHOWED it to be a 10 ohm load.

Many people simply cannot get past the few couple of numbers on the front page of a spec sheet.  They want simple answers (and they totally belive the simple numbers given)-the truth be damned.

Coverage angle of a loudspeaker is another area in which very often the actual coverage angle is nowhwere near the published number.  Yes that number may be right-at some freq-but not across the intended freq band.  At some freq it is narrower and at other freq it is wider.    How much? You have to look at the polar or a ballon plot or directivity plot to figure that out.  And then people believe that the sound "stops" at those printed angles Rolling Eyes Simple numbers simply don't do it-it takes more data to give a real understanding of how a loudspeaker performs.

But I'll stop now. Laughing

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For every complicated question-there is a simple- easy to understand WRONG answer.

Can I have some more talent in the monitors--PLEASE?

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dB Audio & Video Inc.
Danley Sound Labs

Kevin Unger

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Re: Tuba 60 vs. ? ? Spec numbers
« Reply #12 on: December 04, 2010, 02:06:38 pm »

Phil, an Impedance graph is included with the plans.


Nominal is always stated, as it does change with frequency.
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Phil Lewandowski

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Re: Tuba 60 vs. ? ? Spec numbers
« Reply #13 on: December 04, 2010, 03:48:36 pm »

Kevin Unger wrote on Sat, 04 December 2010 14:06

Phil, an Impedance graph is included with the plans.


Nominal is always stated, as it does change with frequency.


That is nice then, and is definetely the right thing to do.

I wonder why bill hasn't published them on the charts part of the forum?  Maybe you could ask if he could do this, as that would be very helpful in combination with the responses.


Any chance you have the T60 plans and would be able to post the impedance plot of the dual-lab12 T60?


Thanks much,

Phil
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Stipe Ercegovic

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Re: Tuba 60 vs. ? ? Spec numbers
« Reply #14 on: December 04, 2010, 04:21:19 pm »

dammmm   Very Happy  

..don't want to start The Impedance Wars here.

I understand power/impedance/freq. and averaged than rounded to closest "standard" one very well.
(Yes power amp standard power/impedance values and whole mess of questions which will rise if we have few similar cabinets one rated 6.7 Ohm, other 3,7 Ohm and next 9,1 Ohm ..etc.)

Just thought that two LAB12 nominally rated 6 Ohm in parallel will give nominal ~3 Ohm so slight rise to 4 Ohm nominal load for that cabinet can't be too wrong assumption?
So even if we look it as complete "system" including slight rise in average impedance through usable freq. range I think that it is still more real to talk about it that it is 2W/1m plot.

However I have not seen imp. graphs of T60's so this is just my assumption which can be wrong.

Best wishes, Stipe
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Jeff Babcock

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Re: Tuba 60 vs. ? ?
« Reply #15 on: December 06, 2010, 05:28:49 pm »

Art Welter wrote on Sat, 06 November 2010 16:22


The 60 inch depth would be a problem in many venues.


That's an understatement....

I can think of many venues where they simply would not be practical to use at all due to their dimensions.  I don't doubt that a horn of that size can have significant output, but in such a form factor it is rarely useful.

Re Phil's request for impedance charts on the BFM forum.... Phil, I wouldn't expect much movement on this.  As you are probably well aware, I campaigned for real world data for ages over there and it only ever caused friction and resistance.  I think my posts were often misinterpreted as confrontational.

I suspect your smaart session a while ago with other sub models injects a dose of reality when compared to the near worthless SPL charts on the site and this may be the reason why I received so much resistance.
http://srforums.prosoundweb.com/index.php/mv/msg/58435/56487 3/16126/

Kevin Unger

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Re: Tuba 60 vs. ? ?
« Reply #16 on: December 06, 2010, 05:52:25 pm »

Space problem?


Most users stand them up, with the horn "firing" into the ceiling. This won't work all to well in a bigger place with high ceilings, but most user are doing bar gigs.


-The chart's were not all to far off.
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Mark Coward

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Re: Tuba 60 vs. ? ?
« Reply #17 on: December 07, 2010, 11:59:32 am »

Phil Lewandowski wrote on Fri, 03 December 2010 20:56

I think what has really been needed for the designs is publishing a impedance plot


Quote:

(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




So there is an impedance plot for the Growler?
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Phil Lewandowski

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Re: Tuba 60 vs. ? ?
« Reply #18 on: December 07, 2010, 01:08:31 pm »

Mark Coward wrote on Tue, 07 December 2010 11:59

Phil Lewandowski wrote on Fri, 03 December 2010 20:56

I think what has really been needed for the designs is publishing a impedance plot


Quote:

(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




So there is an impedance plot for the Growler?



Yes,

It is 4th post down:

http://jtrspeakers.websitetoolbox.com/post?id=4683881



~Phil
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Miguel Castro Rios

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Re: Tuba 60 vs. ? ?
« Reply #19 on: December 16, 2010, 12:20:58 pm »

I don't have a chart like the one you guys are looking for...

Since I bought the plans...

This is what Bill says in the plans.

Quote:

Impedance
   
   LAB drivers have a nominal impedance of 6 ohms, but the mass of air in the horn adds about 2 ohms of acoustic impedance, giving a nominal 8 ohm load. In a 2x12 a pair of LAB 12s wired in parallel will have a nominal 4 ohm load, a pair in series a nominal 16 ohm load.
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