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Old 3rd December 2003, 06:31 PM   #21
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Default Re: I triple dog dare you......

Quote:
Originally posted by Fred Dieckmann
Do I win anything besides the inevitable lecture about where I went wrong, Nelson?
No, your journey is its own reward.
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Old 3rd December 2003, 07:00 PM   #22
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Thumbs up Thanks

It is at that ......... Thanks for your excellent manual which is a very good primer on active crossover design. I really wonder if many people realize what a fascinating and well thought out product it is. I see no comment on how far I am from my desitination, but I take it that I am not wondering in circles in the woods. I have some ideas for a different approach to the resistor and capacitor matrix that would use less parts and PCB real estate at the cost of more programing complexity. Parallel combinations of maybe half a dozen resistors and an equal number of capacitors would give even greater tuning selectivity and the possibility of using all unity gain followers for a simpler circuit with no negative feedback op amp (or discrete transistor op amp) sections. It will be interesting to see the final approach that Mr. Rollins takes with his design. I can see why this would be a formable DIY design project and now understand the time required to undertake it.
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Old 3rd December 2003, 07:04 PM   #23
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Maybe we should all pitch in and buy him a Sponge Bob t-shirt.

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Old 4th December 2003, 02:32 AM   #24
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Default Who............

(Everyone join in singing..........)

Lives in a sealed enclosure (of Q = 0.5) under the sea??

SpongeBob HexPhred!

Cranky, and ornery, and feisty is he.

SpongeBob HexPhred!

If DIY abuse is something you wish.........

SpongeBob HexPhred!

Then make a post, and wind up on his "list"!

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Old 4th December 2003, 03:08 AM   #25
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Old 4th December 2003, 04:16 AM   #26
Variac is offline Variac  United States
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What are these strange feelings i've got?.......
Gratitude and appreciation of Fred?
It looks like competition is a benefit for us, the insatiable DIY consumer! This crossover war has now begun- begun to enlighten even someone as lost as me!!!
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Old 4th December 2003, 04:29 AM   #27
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"I afraid begun, the Active Crossover Wars, have".
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Old 4th December 2003, 01:33 PM   #28
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Quote:
Originally posted by Fred Dieckmann
I can not tell what your bandpass does with no units for the amplitude (y axis) unless I simulated it.[/B]
It is obvious. In schematic exists only one LPF and this is 6dB/oct. You will easily find in frequency response from 20kHz to 40kHz that curve drops for 6 segments. One segment (unit) is than 1 dB and overall resolution on y-axis is 30dB. (Difference from C and D marker is 4 dB). I expect more from one back engineer.
Quote:
This is not a hand holding thread and reading some of the references is required to follow the thread. [/B]
Opps..... My "Lancaster" is only 10 years old.

Are you sure that your back engineering on Pass XVR1 is correct?
Can you draw schematic of 6db/octave filter for all frequency with those resistor packs and additional resistor R=12.4k? Or, for example, please tell me what are combinations of resistors for 36, 66, and 106 Hz (I suppose that C is 47nF).

How you get fr=180Hz for R=12k4 and C=47nF?
Isn't f=1/(2*PI*R*C)?

From Dave's site:
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Old 4th December 2003, 03:03 PM   #29
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Default I guess only Passlabs knows for sure...

quote:
Originally posted by till
High pass should be first or second order at ca. 700Hz.
I want the crossover for the high freqency speaker to provide a 6dB/okt ramp more signal from 10kHz upwards for compensation of the high frequency horns roll of.
I want it to provide about 4dB more between 700Hz or 800Hz and 5,5kHz than beween 5,5 and 10kHz.


Now I am even more confused...

The first section in Till's requirement is for a band pass filter made of a high pass at 700 to 800 hz and a low pass at 5.6Khz.

I assume your band pass is for this range.... your low pass corner(-3dB) is at above 10Khz.

"Are you sure that your back engineering on Pass XVR1 is correct?

The cap is actually 0.047uf for this range and the x1 multiplier.

Reasonably...... go look at the graphs on page 39 of the XOVR1 manual. The cap is actually 0.047uf for this range and the x1 multiplier. The circuit's -3dB point moves with the amount of damping. The schematic is shown with the medium Q setting(the op amp with unity gain) selected and with R1=R2 and C1=C2. Run a Spice model and let me know what you get.
I have not looked at the 6dB section yet but image the capacitor value will be different for the same resistor matrix, if it even is the same matrix........
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Old 5th December 2003, 03:13 PM   #30
moamps is offline moamps  Croatia
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Quote:
Originally posted by Fred Dieckmann
[B]Reasonably...... go look at the graphs on page 39 of the XOVR1 manual.
My manual has only 34 pages. Do you have some special edition?

My attempt in XVR1 reverse engineering (filter only) with some approximation (using standard R and C):

a) fmax/fmin=180/22=8.2
b) for SK filter with R1=R2, C1=C2.....than...... f(i)=1/(2*pi*Ri*Ci)
c) Rmax/Rmin=8.2
d) available resistor raster (using one jumper for setting and with rpacks 4.5k*8 and 18k*4) is 4.5kohm from minimum 4.5k to max 108k (4.5, 9, 13.5, 18, ....103.5, 108)
e) for f1=180 and f2=133 is Rmin/(Rmin+4,5k)=133/180=0,74
f) from d) and e) 4.5/9=0.5, 9/13.5=0.67, 13.5/18=0.75; combination 9/13,5 is used with preresistor for fine tuning, Rpre is 3k9; (9+3k9)/(13.5+3k9)= 0,741
g) from f) Rmin=9+3k9=12.9K, than for fmax=180 C=1/(2*pi*Rmin*fmax)=68.6nF=68nF
h) results (target frequency(Hz)--used resistors(k)--overall resistance--resulting frequency)

180------2*4.5k+3k9------------12.9k------181.5
133------3*4.5k+3k9------------17.4k------134.6
106------18+3k9------------------21.9k-----106.9
88--------18+4.5+3k9------------26.4k------88.7
75--------18+2*4.5+3k9---------30.9k------75.8
66--------18+3*4.5+3k9---------35.4k------66.1
59--------2*18+3k9---------------39.9k-----58.7
53--------2*18+4.5+3k9----------44.4k-----52.7
48--------2*18+2*4.5+3k9-------48.9k-----47.9
36--------3*18+4.5+3k9----------62.4k-----37.5
29--------4*18+4.5+3k9---------80.4k------29.1
25--------4*18+4*4.5+3k9-------93.9k-----24.9
22--------4*18+7*4.5+3k9------107.4k-----21.8

C=68nF, Q=0.707 (another caps for higer frequency are 6n8 and 680pF)

Some curves for 12dB/oct filter outputs (first 8) and switchers position are in pictures below.
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