Circuit I'm going to use:
It's a (24 dB/octave) 4th order Linkwits-Riley filter with input and output buffers at a low cut-off of 45 Hz.
Do you have a suggestion for an op-amp. I'm most familiar with the LM741, however they usually require a split supply (+12 0 -12) to operate in this fasion. This is for my car so I don't have that option.
I do know it is possible to voltage divide my battery using resisters, but that would only give me (+6.5 0 -6.5) .
I just don't want my subs to go into excursion, If I get a signal below 45 Hz, that's what'll happen, at least that's what WinISD has calculated.
I've looked everywhere for an adjustable subsonic filter, but they only seem to come with certain amplifiers. Where can I get just the filter?
An externally hosted image should be here but it was not working when we last tested it.
It's a (24 dB/octave) 4th order Linkwits-Riley filter with input and output buffers at a low cut-off of 45 Hz.
Do you have a suggestion for an op-amp. I'm most familiar with the LM741, however they usually require a split supply (+12 0 -12) to operate in this fasion. This is for my car so I don't have that option.
I do know it is possible to voltage divide my battery using resisters, but that would only give me (+6.5 0 -6.5) .
I just don't want my subs to go into excursion, If I get a signal below 45 Hz, that's what'll happen, at least that's what WinISD has calculated.
I've looked everywhere for an adjustable subsonic filter, but they only seem to come with certain amplifiers. Where can I get just the filter?
I'm sorry but a 45Hz filter is going to sound quite bad. You are not building a sub you're building a 'not very good at bass' speaker. I would take a revisit of your speaker design.
TL07x series op-amps would work fine in such an application, you could make an active supply splitter, or easier still would be just to AC couple the whole thing.
TL07x series op-amps would work fine in such an application, you could make an active supply splitter, or easier still would be just to AC couple the whole thing.
Perhaps you can get a better scope of what I'm trying to do. At the bottom of this link, http://spkrbox1.spaces.msn.com/ , is my 4th order band-pass bass box. My actual design has changed a bit and I haven't had a chance to update it. My new design calls for a 9.5" X 4" port. I used WinISD to aid in the design and it calculates that anything below 45 Hz (@ 200 WRMS), my sub will go into excursion.
Any suggestions would be most appreciated.
Any suggestions would be most appreciated.
I skimmed through the page in about 30 seconds. All I can say is that you need to change your box design, maybe trade some efficiency for bandwidth, or maybe use a different driver. I haven't looked up the parameters of the one your'e using but it might not be suited to bandpass or vented boxes.
That box will be a one note trick, and when you add a 45Hz filter it will make it even worse. Also there will be no real deep bass.
That box will be a one note trick, and when you add a 45Hz filter it will make it even worse. Also there will be no real deep bass.
for some simple reference, read a paper i wrote:
http://www.ee.siue.edu/~cstahl/e592b.pdf
this paper detials the common non-inverting single amplifier biquad in the general case and then expands to two of the three common cases.
case 1 -- equal resistance, fixed gain of 1, Q adjusted by capactiors.
case 2 -- equal capacitance, fixed gain of 2, Q adjusted by resistors.
case 3 -- equal capacitance, equal resistance, Q adjusted by gain.
i didn't cover case 3. for this circuit a high gain makes component tolerance requirements unreasonable. for a general purpose filters i prefer case2, which allows the Q to be adjusted with resistors which are found in 1% tolerance.
now you just need to find a look-up table for the desired Q and F values for the filter you want.
also look into "filter free" by nuhertz. or filter pro ect... filter free will give you up to 3rd order filters.
http://www.ee.siue.edu/~cstahl/e592b.pdf
this paper detials the common non-inverting single amplifier biquad in the general case and then expands to two of the three common cases.
case 1 -- equal resistance, fixed gain of 1, Q adjusted by capactiors.
case 2 -- equal capacitance, fixed gain of 2, Q adjusted by resistors.
case 3 -- equal capacitance, equal resistance, Q adjusted by gain.
i didn't cover case 3. for this circuit a high gain makes component tolerance requirements unreasonable. for a general purpose filters i prefer case2, which allows the Q to be adjusted with resistors which are found in 1% tolerance.
now you just need to find a look-up table for the desired Q and F values for the filter you want.
also look into "filter free" by nuhertz. or filter pro ect... filter free will give you up to 3rd order filters.
Ok, here they are:
--Subs
Blaupunkt TSw1200
Qes 0.38
Qms 4.06
Qts 0.347
Fs 25 Hz
Vas 4.178 cu. ft.
Ze 4 ohms
Re 3.69 ohms
Xmax 0.22 in.
SPL 90 dB
Pe 200 W
BL 12.5
Sd 0.549 sq.ft.
air volume displacement 0.12 cu.ft.
--Amp
Sony Xplod XM2200GTX
200 WRMS X 2 @ 4 OHM
250 WRMS X 2 @ 2 OHM
500 WRMS X 1 @ 4 OHM
50 - 300 Hz , 12 db/oct Low-pass filter
0 - 10 dB (40 Hz) Low boost
--------------------------------------------
Space I need to work within:
Width - no more than 29"
Heigth - no more than 14.75"
Depth - my entire trunk if needed
Would be best if front of box was at a 79.5° to fit nice and snug against the back of my back seat. My seats fold forward.
--Subs
Blaupunkt TSw1200
Qes 0.38
Qms 4.06
Qts 0.347
Fs 25 Hz
Vas 4.178 cu. ft.
Ze 4 ohms
Re 3.69 ohms
Xmax 0.22 in.
SPL 90 dB
Pe 200 W
BL 12.5
Sd 0.549 sq.ft.
air volume displacement 0.12 cu.ft.
--Amp
Sony Xplod XM2200GTX
200 WRMS X 2 @ 4 OHM
250 WRMS X 2 @ 2 OHM
500 WRMS X 1 @ 4 OHM
50 - 300 Hz , 12 db/oct Low-pass filter
0 - 10 dB (40 Hz) Low boost
--------------------------------------------
Space I need to work within:
Width - no more than 29"
Heigth - no more than 14.75"
Depth - my entire trunk if needed
Would be best if front of box was at a 79.5° to fit nice and snug against the back of my back seat. My seats fold forward.
Why may i ask? i hope you know passive subsonic filter make the speaker sound like poo... I mean you could use 600w a/c rated Poyproplene caps and big air ribbon coils and it would still be yukkie sounding. Just to spout out a question on a rolloff without giving the senerio of the rest of the circut does no good if you expect a honest real life agreeable awnser
to awnser your question, use a active filter linkwitz-riley to do a fair job at rolling off 24db.
for the purposes listed, a linkwitz-riley filter is not really appropriate. the only advantage is is large band-wagon.
i'd say a typical butterworth filter might be more appropriate, if your going active.
i am not entirely sure, but you should check to see if basic RC filters will work. maybe a C-R highpass on the amp input, and a C-R filter on the amp output.
i'd say a typical butterworth filter might be more appropriate, if your going active.
i am not entirely sure, but you should check to see if basic RC filters will work. maybe a C-R highpass on the amp input, and a C-R filter on the amp output.
I don't think I need anything on the output (tell me if I'm wrong) since I'm using a 4th order bandpass bass box. The upper frequencies are already taken care of. It's the lower frequencies (below 45 Hz) at higher wattages (above 70 WRMS out of 200 WRMS possible) the I'm trying to cut off to prevent excursion.
Now if I have the gross dimensions of my box
Vf = .76 cu.ft.
Vr = .87 cu.ft.
tuned at 60 HZ
port dia. 3.94"
port length = 9.54"
Excursion is just below the line @ 200 WRMS with a 4th order Linkwitz-Riley set at 33 Hz my excursion graph looks like this @ 200 WRMS:
Now if I have the gross dimensions of my box
Vf = .76 cu.ft.
Vr = .87 cu.ft.
tuned at 60 HZ
port dia. 3.94"
port length = 9.54"
Excursion is just below the line @ 200 WRMS with a 4th order Linkwitz-Riley set at 33 Hz my excursion graph looks like this @ 200 WRMS:
An externally hosted image should be here but it was not working when we last tested it.
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