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Author Topic: BS-212 Test Sweeps  (Read 8088 times)

Antone Atmarama Bajor

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BS-212 Test Sweeps
« on: October 20, 2005, 03:33:07 pm »

     UPDATED

     Ok I did a bunch of sweeps on various drivers yesterday.  
among them  TAD TL-1603's, JBL 2225, JBL 2245 in 4645 cab, and of course Eminence Lab 12's in my BS-212 Cabs.

    Test setup:
TEF 20
Old P2 Laptop running SL 6.7.9.4
Alesis Matica 900 Bridged Mono
Fluke DMM
Crown XXX omni microphone placed 32.8' away from speakers hovering ~ 2" off the ground.

    Issues:
I Didn't have calibration data for mic until last test.  Volts per pascal was set at default .01 and needed to be .011.  The final test was the JBL 2225's.  I tried changing these values under "current settings" it seemed to make about .5dB difference
but I seem to be measuring ~5-6dB more than predicted.  If anyone knows how I can make those corrections after the fact it would be greatly appreciated.  I Corrected This Using Calculation tools at
http://www.sengpielaudio.com/calculator-soundlevel.htm

This site was very helpful.

I am not sure at what the high cut should be doing a 1/2 space ground plane measurements.  Everything things to start rolling off in the low mid 100's.

    Here is an overlay of four cabs tested:

index.php/fa/2857/0/



    I'm not sure How Bass Box determines its Normalize Amplitude 0dB point but it claims I'm at 0dB around 43Hz -7dB around 20Hz and +1.5 around 100Hz.  I'm measuring (6Hz resolution) -6dB @20Hz relative to 43Hz and +4.4dB @100Hz.  I guess that would actually put me ~-10dB @20Hz.  I'm wondering if getting 3dB more than predicted @ 100Hz has something to do with the dimensions of the two cabs being about 3.5'X4'???

More to follow
Antone-

    Update the 2225 sweep says 8 Ohms at 20VRMS this is incorrect it was two drivers in parallel so 4 Ohms @ 20VRMS.

    The 4Labs were wired in series parallel so 6 Ohms @ 24.5VRMS.

    I tried to keep everything @ 100Watts @ rated Z.
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Antone Atmarama Bajor

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BS-212 Test Sweeps Harmonic Tracking
« Reply #1 on: October 20, 2005, 03:35:40 pm »

Here is the 2nd and 3rd Harmonic Tracking of the BS-212

index.php/fa/2843/0/
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Antone Atmarama Bajor

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Re: BS-212 Test Sweeps Harmonic Tracking
« Reply #2 on: October 20, 2005, 03:39:41 pm »

Check this out these measures were unexpected.

These are my THD measurements (I didn't do noise there was plenty of ambient noise around)

index.php/fa/2844/0/
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Antone Atmarama Bajor

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Extension.
« Reply #3 on: October 20, 2005, 05:22:55 pm »

     Although the Pair of BS-212's would require some radical EQ to get them Flat too 20Hz, which would limit the cabs overall output to around 116dB @ 1Meter (Never Exceeding XMAX).  The only cab configuration of similar volume that I know of that can beat this is Toms Tower Of Bass.  I don't know how THD @ 100Watts @ 10Meters translates back to 1W 1Meter but 1.07%  THD @ 20Hz is Retarded low Distortion.  I only wish I had enough AMP to run these things @ full RMS.  I would like to see what THD would be there.

    Still the weakest point of these cabs is the Group Delay is in the mid 20's of ms at around 20Hz.  Can't have everything well maybe I can tweak with some digital processors servo feedbacks and all pass filters.  But that would just make everything Later than on time.

Antone-

P.S.  Oh please I don't wanna be Duane Dibbley.
index.php/fa/2846/0/
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Antone Atmarama Bajor

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Re: BS-212 Test Sweeps
« Reply #4 on: October 21, 2005, 02:22:46 pm »

     I know there isn't anything monumental or groundbreaking about my cab here but does anyone have any thoughts about it?  

    I know I'm going to have to retake the sweeps with the mic calibration set (Unless some one here is a TEF guru and knows a correction factor I can apply).

    The part about this cab that I'm most impressed with is that it is a reflex cab with very low Harmonic Distortion Below 20Hz down to about 16Hz.

   I know you guys are all a bunch of bass horn gurus.  That will be my next project.

Antone-
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Antone Atmarama Bajor

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Is there a better driver?
« Reply #5 on: October 22, 2005, 02:58:20 pm »

     Is there better than the LAB 12 driver for LFE on the market????  I can't find anything that models as well; some of the others that come close would need twice the internal volume for 1-2dB more output at 20Hz.  The only other option to keep size down seems to be Isobaric  But then I'd need my own power plant to get the SPLS.

    So anyhow.  Let me know if there is anything close to as efficient down in the 30Hz and Bellow Range.  The only things that come to mind are Danley Subs, Contra Bass, And Genelec.

    These things must make a wicked low car sub with all of the in cab gain.

Antone-

 
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Johan Rademakers

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Re: Is there a better driver?
« Reply #6 on: October 25, 2005, 05:33:30 pm »

Perhaps Tumult, Mealstrom and alike?

Wkr Johan Rademakers
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Antone Atmarama Bajor

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Re: Is there a better driver?
« Reply #7 on: October 25, 2005, 05:38:08 pm »

     Are those Manufacturers or model names??

Antone-
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Antone Atmarama Bajor

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Re: Is there a better driver?
« Reply #8 on: October 25, 2005, 05:57:44 pm »

Oohh That Tumult 18 looks like it would be really nice in a sealed box.  Really good in a vented box too but I don't think I'd want to build that Cab.

Thanks those are some cool drivers.

    Though A vented Box with the tumult 18 would have ~the same output as my 4X12 Lab subs @ 20Hz in almost exactly the same Volume.  The best part about the tumult 18 is its huge XMAX would keep it in the gap across its entire power bandwidth and than some.  A Sealed single 18 Tumult would however have slightly more output @ 20Hz Than a single Vented Lab 12 using roughly the same volume box, but thats mainly due to 2X the LABS RMS.  But I'm sure the single 18 would sound Tight in a sealed box!!!  Too bad they are 4X the price of 1 Lab 12.  But it looks like a reasonable candidate for many projects!!

Antone-
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Antone Atmarama Bajor

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Limits of Reflex Cabinets.
« Reply #9 on: October 27, 2005, 02:09:41 am »

     Have we pretty much reached the limits of what is possible with reflex speaker cab technology and LF extension.  Without using unreasonably Large Pistons in unreasonably Large Cabinets?

    Toms Tapped Horn seems to be the only thing in existence that is as efficient at 20Hz in such a small Volume.

    4 Lab 12's or 1 Adire Tumult 18" are the ~ the same vas.  Seem to be the best I have modeled yet.  It is becoming apparent to me that Reflex cabs are not the way for significant output bellow 40-50Hz.  Unless you have a lot of space and a lot of power available.

    I think Tom has designed the only true compact sub with significant output in the 20Hz Range.  I could come within 4 or 5dB of the DTS-20 with close to the same volume cab.  Or close the Gap by 2dB with a 20 or 30cu' Cab.

    There has to be another way to accomplish this in a compact package with High output and High fidelity.

Antone-    
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