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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Subwoofer FUD Forum Archive => Topic started by: Miguel Castro Rios on November 05, 2010, 11:13:28 pm

Title: Tuba 60 vs. ? ?
Post by: Miguel Castro Rios on November 05, 2010, 11:13:28 pm
Has any one built the tuba 60??

Any measurements.

We are considering building a couple of them.

http://www.billfitzmaurice.com/T60.html

http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=1 1124

We are wondering if it could replace a conventional Front Loaded. Dual 18" Sub woofer. (spl-wise)

Like the EAW sb850 or SB1000.
Title: Re: Tuba 60 vs. ? ?
Post by: Art Welter on November 06, 2010, 04:22:11 pm
Miguel Castro Rios wrote on Fri, 05 November 2010 21:13

Has any one built the tuba 60??

Any measurements.

We are considering building a couple of them.

http://www.billfitzmaurice.com/T60.html

 http://billfitzmaurice.info/forum/viewtopic.php?f=12&t=1 1124

We are wondering if it could replace a conventional Front Loaded. Dual 18" Sub woofer. (spl-wise)

Like the EAW sb850 or SB1000.


I have not built them, but looking at the design it is easy to see that it is a very long horn and a larger cabinet than the LabSub.

One to one, I would think it would have no problem outperforming the much smaller subs you mentioned (the T-60 is almost double the size), especially when used in multiples.

The 60 inch depth would be a problem in many venues.
Title: Re: Tuba 60 vs. ? ?
Post by: Miguel Castro Rios on November 11, 2010, 12:37:47 am
Thanks for the info.

It would be nice to compare it to other subs, to have opinions from several users to have a better reference for those of us who haven´t built it... Yet

Title: Re: Tuba 60 vs. ? ?
Post by: Stipe Ercegovic on November 30, 2010, 02:21:06 pm
If you look for (relatively) compact DIY cabinet to replace classic bass reflex double 18"er one of my "Cyclops" may be one of possible choice.
Symetryc tapped horn -designed to quality cover ~40Hz to ~130hz range.

On Free Speaker Plans and Speaker Plans forums ..there are few topics about building CB-18 and one about CBe-18 (standard-extended version)

    http://www.freespeakerplans.com/index.php?option=com_jfusion &Itemid=64&jfile=viewtopic.php&f=7&t=1132Link1
    http://forum.speakerplans.com/build-of-2-cb18s-modified-x10- and-duran-tops_topic40867.htmlLink2
    http://forum.speakerplans.com/four-cb18-cyclops-and-four-mod ified-single-smt_topic44449.htmlLink3
    http://forum.speakerplans.com/beware-the-one-eyed-monster_to pic39393.htmlLink4

    http://forum.speakerplans.com/extended-cb18-cyclops_topic450 15.html - CBe-18 Link


CB-18 standard "Cyclops" ; compact size (W=1052mm,H=576mm,D=618mm)
CBe-18 front extended version (for better stacking stability in higher stacks and slight more LF extension.)
Above noted two versions are built/tested and have reported only very good results and positive impressions about sound and performance.

There is also available CBX-18 - full extended version (W=1152mm, H=576mm, D=700mm)..for even a bit more LF extension and slight gain in sensitivity through usable freq. range) - based on same schema as two smaller versions but this version is still not built/tested

Plans are free for DIY - personal use not commercial production (for sale)

Best wishes,
      Stipe
Title: Re: Tuba 60 vs. ? ?
Post by: Art Welter on November 30, 2010, 10:08:59 pm
Stipe,

Nifty design, but it looks to roll off almost an octave above the Tuba 60 if this sim is accurate.
index.php/fa/33988/0/

102 dB sensitivity is good for a small bin though.
Title: Re: Tuba 60 vs. ? ?
Post by: Stipe Ercegovic on December 01, 2010, 09:53:53 am
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 Smile ) - 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  Very Happy  ) 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
Title: Re: Tuba 60 vs. ? ?
Post by: Kevin Unger on December 02, 2010, 10:53:45 pm
[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.

Title: Re: Tuba 60 vs. ? ?
Post by: Phil Lewandowski on December 03, 2010, 09:29:34 am
[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
Title: Re: Tuba 60 vs. ? ?
Post by: Kevin Unger on December 03, 2010, 06:36:53 pm
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."
Title: Re: Tuba 60 vs. ? ?
Post by: Phil Lewandowski on December 03, 2010, 09:56:52 pm
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

Title: Re: Tuba 60 vs. ? ?
Post by: Art Welter 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.
Title: Re: Tuba 60 vs. ? ? Spec numbers
Post by: Ivan Beaver 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

Title: Re: Tuba 60 vs. ? ? Spec numbers
Post by: Kevin Unger 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.
Title: Re: Tuba 60 vs. ? ? Spec numbers
Post by: Phil Lewandowski 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
Title: Re: Tuba 60 vs. ? ? Spec numbers
Post by: Stipe Ercegovic 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
Title: Re: Tuba 60 vs. ? ?
Post by: Jeff Babcock 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/
Title: Re: Tuba 60 vs. ? ?
Post by: Kevin Unger 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.
Title: Re: Tuba 60 vs. ? ?
Post by: Mark Coward 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?
Title: Re: Tuba 60 vs. ? ?
Post by: Phil Lewandowski 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
Title: Re: Tuba 60 vs. ? ?
Post by: Miguel Castro Rios 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.
Title: Re: Tuba 60 vs. ? ?
Post by: Phil Lewandowski on December 16, 2010, 02:34:19 pm
Miguel Castro Rios wrote on Thu, 16 December 2010 12:20

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.



Thanks Miguel, that's exactly what we were expecting. Thank you for confirming that.


Take care,
Phil