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Old 25th June 2013, 09:19 PM   #3561
tb46 is offline tb46  United States
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Join Date: Jan 2006
Location: Texas
Default Posts # 3552,3554,3558

Hi David,

Thanks again for you effort it is very much appreciated.

Looking at Bagby's software (Woofer Box Model and Circuit Designer, Version 4.5 12/4/2009) again, it looks like I may have found the basic error: when switching the "Selectable Textbook High Pass Filter" from "Fourth Order Butterworth" to "Fourth Order Linkwitz-Riley" there is no change in the "Circuit Shape" as indicated on the graph; but, when using both of the "Optional Second Order Adjustable High Pass Filter Stages" @ Fc=24Hz Q=0.707 [Gain(dB)=-3.0dB] I get the expected 4th order LR response on the graph. The LP section also shows the same curve for Bw and LR. In other words, I think I may have found a bug (or two) in Bagby's spreadsheet, not in Hornresp.

I'll attach a few screenprints:

1. Bagby's Input screen
2. BP: Dual 2nd order Butterworth HP plus 4th order LR LP
3. BP: 4th order LR (both: HP and LP)
4. HP: 4th Bw
5. HP: 4th LR
6. HP: 2x 2nd Bw
7. SPL w/o filters
8. I'll tried to add Bagby's Excel file by changing the extension from .xlsm to .txt; but, the file size is too big (I can email it to anyone interested).

So, at this time it looks to me like all is well in Hornresp land.

Regards,

P.S.: Just downloaded and tested Baby's Version 5.0, same result as Version 4.5.
Attached Images
File Type: jpg WBCD_Input.jpg (30.6 KB, 95 views)
File Type: jpg WBCD_BP_24Hz_HP_2x_2nd_BW_82Hz_LP_4th_LR.jpg (65.1 KB, 91 views)
File Type: jpg WBCD_BP_24Hz_82Hz_4th_LR.jpg (64.7 KB, 90 views)
File Type: jpg WBCD_HP_24Hz_4th_Bw.jpg (61.5 KB, 91 views)
File Type: jpg WBCD_HP_24Hz_4th_LR.jpg (62.8 KB, 90 views)
File Type: jpg WBCD_HP_2x_24Hz_2nd_Bw.jpg (63.5 KB, 13 views)
File Type: jpg WBCD_Flat.jpg (64.6 KB, 9 views)
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Oliver

Last edited by tb46; 25th June 2013 at 09:44 PM. Reason: Added P.S.
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Old 25th June 2013, 10:05 PM   #3562
tb46 is offline tb46  United States
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Join Date: Jan 2006
Location: Texas
Hi kees52,

Post #3560: "...I think you have to experiment in real live to get it right."

I'm a great believer in experimenting; but, if we cannot simulate the electrical behaviour of a relatively "simple" filter circuit with some accuracy anymore, then we would have taken a vast step backwards. So, we may experiment for whole system response and integration; but we should be able to get the basic (particularly electronic) building block simulations correct.

Regards,
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Old 25th June 2013, 10:20 PM   #3563
kees52 is offline kees52  Netherlands
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Quote:
Originally Posted by tb46 View Post
Hi kees52,

Post #3560: "...I think you have to experiment in real live to get it right."

I'm a great believer in experimenting; but, if we cannot simulate the electrical behaviour of a relatively "simple" filter circuit with some accuracy anymore, then we would have taken a vast step backwards. So, we may experiment for whole system response and integration; but we should be able to get the basic (particularly electronic) building block simulations correct.

Regards,
Hi TB

Afcourse you are right about that, simulating has bring a lot of deeper science to us in DIY, thanks to David and other programmers.

I did mean when the simulation is a like, then fine tune, you will see that loudspeakers are a big challence for filters, I do like to use impedance correction circuits, it make better behavior and audio is more relaxed, the same as you use a very good speaker who is very smood frequentieplot.

I did make amps without sims long ago, it did costs a lot more because of blown parts, now it is very rare that i do blow something thanks toy simulations.

regards

kees
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Old 26th June 2013, 07:19 AM   #3564
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Quote:
Originally Posted by AndrewT View Post
I don't understand what you mean withand similarly for the others.
Hi Andrew,

"Red trace - 4th-order Butterworth, 2 x -3dB = -6dB at fc (94dB - 100dB)" shows the combined effect of the two filter gain responses given in Attachment 1 below, when applied to a constant 100dB signal. At the cutover frequency of 100 Hz the gain is -3dB each for the high-pass and low-pass filters. When used together to form a band-pass filter, but with both the HF and LF cutoff frequencies at 100 Hz, the gain at the single common 100 Hz cutover frequency becomes (-3db) + (-3db) = -6dB, as shown in my earlier post.

Similarly, "Grey trace - 4th-order Linkwitz-Riley, 2 x -6dB = -12dB at fc (88dB - 100dB)" shows the combined effect of the two filter gain responses given in Attachment 2 below, when applied to a constant 100dB signal. At the cutover frequency of 100 Hz the gain is -6dB each for the high-pass and low-pass filters. When used together to form a band-pass filter, but with both the HF and LF cutoff frequencies at 100 Hz, the gain at the single common 100 Hz cutover frequency becomes (-6db) + (-6dB) = -12dB, as shown in my earlier post.

The other results shown in my earlier post were generated in a similar fashion.

As mentioned previously, it is important to remember that two separate filter gains are being applied to a single signal - as distinct from two separate signals being combined.

If you can see any flaws in my reasoning, please let me know.

Kind regards,

David
Attached Images
File Type: png BW.png (56.2 KB, 21 views)
File Type: png LR.png (56.1 KB, 24 views)
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Old 26th June 2013, 07:26 AM   #3565
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Quote:
Originally Posted by tb46 View Post
So, at this time it looks to me like all is well in Hornresp land.
Excellent :-).

Many thanks Oliver, for taking the time to investigate the matter further, and for letting me know the outcome.

Kind regards,

David
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Old 26th June 2013, 12:35 PM   #3566
AndrewT is offline AndrewT  Scotland
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I still don't follow.
Can some one else step in and explain that to me?
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Old 26th June 2013, 06:40 PM   #3567
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We have the TH1 option that jumps the back side of the driver from S4 to S3 leaving us with a second segment after the driver.

How about TH2 jumping the frontside of the driver from S2 to S1 giving us another segment between the drivers. A chamber could be used if the simulation needed the cushion that L12 provided before. I have seen many simulations with L12 already at the shortest length possible so why not.
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Old 27th June 2013, 07:16 AM   #3568
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Quote:
Originally Posted by David_Web View Post
How about TH2 jumping the frontside of the driver from S2 to S1 giving us another segment between the drivers.
Hi David_Web,

This option was recently requested by Djim in Post #3530.

The code changes necessary to implement the functionality would be significant - particularly the modifications to the Loudspeaker Wizard. Unfortunately from my perspective the work required far outweighs the relatively small additional design flexibility to be gained.

Sorry, but you will have to use AkAbak if you wish to simulate such a configuration.

Kind regards,

David
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Old 27th June 2013, 08:42 AM   #3569
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Quote:
Originally Posted by AndrewT View Post
I still don't follow.
Can some one else step in and explain that to me?
Hi Andrew,

I will try one more time, before admitting defeat and then letting someone else have a go :-).

"Red trace - 4th-order Butterworth, 2 x -3dB = -6dB at fc (94dB - 100dB)"

Imagine a 4th-order Butterworth band-pass filter being applied to a 100dB signal:

Attachment 1 below shows the un-filtered 100dB signal.
Attachment 2 shows the filtered signal when lower fc = 25 Hz and upper fc = 400 Hz.
Attachment 3 shows the filtered signal when lower fc = 50 Hz and upper fc = 200 Hz.
Attachment 4 shows the filtered signal when lower fc = 100 Hz and upper fc = 100 Hz.

Attachment 4 is the same as the red trace referred to above.

Kind regards,

David
Attached Images
File Type: png Attach1.png (63.5 KB, 23 views)
File Type: png Attach2.png (50.7 KB, 20 views)
File Type: png Attach3.png (49.9 KB, 19 views)
File Type: png Attach4.png (50.3 KB, 22 views)
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Old 27th June 2013, 09:53 AM   #3570
AndrewT is offline AndrewT  Scotland
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Ah, I get what you have been trying to describe.
A bandpass filter that has NO passband !
Why ?
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