Hi all, I'm building for my son a box (like a tools box) that will contains his PSP and related stuff, my idea is to make it also an aplifier box, so I'll have on the cover 2 laudspeakers (took from an old stereo cassette record (a good one!) to which there are already connected two tweeters with a capacitor (I think to cut low freq). I've already made 2 amplifiers with 2 tda7053B and a tone control with a tda1524A (I've made the PCB myself and it's working fine, if anybody's interested in this PCB pls ask), my question is , I have another loudspeaker bigger than the other two that I would like to use as a subwoofer, but there is no space left for another circuit/PCB under the cover. Do you have any suggestion how I can have only bass freq on this single loudspeaker using few passive component (R,C,L)?, please bear in mind my electronical knoledge is limited to 3 years I've studied in the old '70s!!!. thanks for you help.
xstephanx said:
Thanks xstephankx for your reply but it's not clear what u mean, or may be my post was not clear enough, I don't know too much frequency, inductor and things like that. What I really need is something ready made, I mean ''1 capacitor of x nF, one restistor of xohm and so on''. What I need is to hear more low freqs. than now, so no HiFi sound, I've already connected this single loudspeaker and I hear more low freq but I hear also all the other freq. Thx again.
If you want to play around and have got some old broken teles or
computer bits try to find the coils in the switch mode supplies unsolder them ,smash the ferrite cores out of them and wire them up in series
with the big speaker till you get the high frequency cut you desire. you can just add them up like resistors.
computer bits try to find the coils in the switch mode supplies unsolder them ,smash the ferrite cores out of them and wire them up in series
with the big speaker till you get the high frequency cut you desire. you can just add them up like resistors.
Hi,
your in danger of converting stereo to mono.
What you need to do is this :
Set up your amplifiers in bridged configuration but with stereo inputs.
Connect left and right speakers in antiphase which will make the
overall configuration phase consistent.
The bass with a series inductor is then connect betwwen L+ & R+.
Note that a bass unit will need to have a particular sensitivity
that matches the Left and Right speakers for this to work well.
You also need to make sure the amps can drive the bass unit
impedance in bridged configuration.
You can also connect series capacitors to Left and Right
if they overload at low frequencies.
/sreten.
your in danger of converting stereo to mono.
What you need to do is this :
Set up your amplifiers in bridged configuration but with stereo inputs.
Connect left and right speakers in antiphase which will make the
overall configuration phase consistent.
The bass with a series inductor is then connect betwwen L+ & R+.
Note that a bass unit will need to have a particular sensitivity
that matches the Left and Right speakers for this to work well.
You also need to make sure the amps can drive the bass unit
impedance in bridged configuration.
You can also connect series capacitors to Left and Right
if they overload at low frequencies.
/sreten.
Hi my submission purely related to finding cheap air wound coils to mess about with .Treat the bass unit with the coils as one unit for the purposes of the circuit ,from whats been said it appears like your setting up a difference signal channel ,this used to be used as a pseudo surround sound rear channel in the old days.You would get more bass by fitting 2 smaller units and keeping the channels separate
I think.
I think.
Have you tried that coil tip baggins? Seems to me that you will need a shedload of inductors chained to get enough inductance...
What sreten is suggesting is how most car amps work. He left out some imprtant info thugh You actually need one amp non-inverting with gain=x and the other amp inverting also with gain=x. Then the inverted channel you connect the speaker the other way round. This maintains phase when the usual inputs are used, but also provides a bridged summed channel should you wish to connect a speaker across the output of each channel.
It's not a difference channel, just a neat way of doing it which also has the benefit of symetrically loading the PSU and making it run nicer when only stereo (2 speakers) are used.
What sreten is suggesting is how most car amps work. He left out some imprtant info thugh
You actually need one amp non-inverting with gain=x and the other amp inverting also with gain=x. Then the inverted channel you connect the speaker the other way round. This maintains phase when the usual inputs are used, but also provides a bridged summed channel should you wish to connect a speaker across the output of each channel.It's not a difference channel, just a neat way of doing it which also has the benefit of symetrically loading the PSU and making it run nicer when only stereo (2 speakers) are used.
Well my whole point was to help the guy to try and experiment on the cheap, he had said he didnt understand inductors etc. etc. He was hardly likely to go out and start buying MilliHenries worth of them
without Knowing what they did.
About the values he could always leave the cores in at the expense of distortion (vast) to prove that it works and then maybe purchase some decent air cores when hes got enough confidence to apply the formulas and decide on the values .
without Knowing what they did.
About the values he could always leave the cores in at the expense of distortion (vast) to prove that it works and then maybe purchase some decent air cores when hes got enough confidence to apply the formulas and decide on the values .
richie00boy said:He left out some imprtant info thugh
It's not a difference channel, just a neat way of doing it which also has the benefit of symetrically loading the PSU and making it run nicer when only stereo (2 speakers) are used.
Hmmm.....
seems to me a different way of saying the same thing,
/sreten.thank to everybody for all the answers, that are too techical for me, you are like Einstein trying to eplain relative theory to a child at scoo! ;-)
I'm getting confused and lost on what I have to do, so I think that what I want to achive cannot be done in a simple way, 'couse I don't want to spend more money on this projet and so I have to use what I already got. So I will say my question in another way :
-I dont need HIFI stereo, so I can have low freq only from I channel (don't say boooh!)
- wich value for capacitor/resistor/coil I have to use to connect one loudspeaker in order to cut high freq, and how I need to connect it parellal/serial.
If this is not possible I thank you again in advance for your kind help.
Arma61
I'm getting confused and lost on what I have to do, so I think that what I want to achive cannot be done in a simple way, 'couse I don't want to spend more money on this projet and so I have to use what I already got. So I will say my question in another way :
-I dont need HIFI stereo, so I can have low freq only from I channel (don't say boooh!)
- wich value for capacitor/resistor/coil I have to use to connect one loudspeaker in order to cut high freq, and how I need to connect it parellal/serial.
If this is not possible I thank you again in advance for your kind help.
Arma61
Arm ,
Read what I said earlier- get some coils and put them in series with
the big loudspeaker and 1 channel, if you like, but remember it will unbalance the system If you can find enough coils you may be able to connect the one loudspeaker to both channels but youwill need big coils or a lot of them or you will end up with MONO.
( amp +ve) -- (coil) -- (coil) -- etc -- (+ve loudspeaker-ve) -- (-ve amp)
This is how to wire it
Bill.
Read what I said earlier- get some coils and put them in series with
the big loudspeaker and 1 channel, if you like, but remember it will unbalance the system If you can find enough coils you may be able to connect the one loudspeaker to both channels but youwill need big coils or a lot of them or you will end up with MONO.
( amp +ve) -- (coil) -- (coil) -- etc -- (+ve loudspeaker-ve) -- (-ve amp)
This is how to wire it
Bill.
arma61:
Everyone wants you to go purist. I agree, but your question CAN be answered, and you don't always have to follow all the rules.
You must NOT connect both amp channels to the woofer if using only one woofer/voice coil with stereo source. This is where dual VC will be very handy, otherwise you have to choose a channel if not bridging, as described by others here. I hate the idea of loading 2 channels differently, but the laws of physics will allow it.
My assumption is that driver impedance is nearly resistive (in the impedance curve swoop between resonance below and inductive rise) at filter frequency of interest (I suggest 3-400Hz if driver smaller than 8 inches). Check ohms with multimeter. This will not tell you everything, but it gives the ballpark. A nominal 8-ohm driver will probably measure 4-6 ohm DCR. Add about 1 ohm to figure the impedance minimum value (roughly where driver will interact with filter). You can compensate for inductance above this point with a Zobel network to maintain filter performance, but not essential. You could probably assume 6-ohm impedance for rough guessing.
Optional: Zobel network to flatten inductive rise. Inductance could probably be guessed around 1.5 mH (L measurement at 1kHz would be helpful). If 6-ohm DCR, use 6-ohm resistor in series with capacitor where C=L/(R^2) (here would be about 40 uF). Connect these two in shunt with the woofer.
I recommend a second-order filter, as filter frequency is not a function of actual driver impedance, only Q (damping) is.
Per ohm (at 350Hz), use inductor (L) of about 0.85mH for critical damping (larger = overdamped, smaller = underdamped). and C=1/(2*pi*350Hz)/L. Connect the capacitor in shunt with the woofer and the Zobel network (3 parallel paths), and the inductor in series with the works.
To quantify the example, my component choices, assuming you have about 6 ohms DCR and 1.5 mH VC inductance;
parallel paths:
path 1 = woofer
path 2 = 6 ohm + 40 uF
path 3 = 33 uF
and hook the whole shabang in series with 4.5 mH inductor.
If you get a dual voice coil (say, 4 ohms each) woofer, halve the resistance and inductance values, double the capacitance values, and connect two complete and equal networks, one to each voice coil and amplifier channel respectively.
Choice of frequency is inveresely linearly proportional to inductance and path 3 capacitance (filter frequency= 1/(2*pi*sqrt(L*C)).
The whole thing is more involved in truth, but my impression is this is the sort of analysis you are seeking... This is a definite finger-in-the-wind approach, but it won't blow anything up and may even sound OK.
Have fun!
Everyone wants you to go purist. I agree, but your question CAN be answered, and you don't always have to follow all the rules.
You must NOT connect both amp channels to the woofer if using only one woofer/voice coil with stereo source. This is where dual VC will be very handy, otherwise you have to choose a channel if not bridging, as described by others here. I hate the idea of loading 2 channels differently, but the laws of physics will allow it.
My assumption is that driver impedance is nearly resistive (in the impedance curve swoop between resonance below and inductive rise) at filter frequency of interest (I suggest 3-400Hz if driver smaller than 8 inches). Check ohms with multimeter. This will not tell you everything, but it gives the ballpark. A nominal 8-ohm driver will probably measure 4-6 ohm DCR. Add about 1 ohm to figure the impedance minimum value (roughly where driver will interact with filter). You can compensate for inductance above this point with a Zobel network to maintain filter performance, but not essential. You could probably assume 6-ohm impedance for rough guessing.
Optional: Zobel network to flatten inductive rise. Inductance could probably be guessed around 1.5 mH (L measurement at 1kHz would be helpful). If 6-ohm DCR, use 6-ohm resistor in series with capacitor where C=L/(R^2) (here would be about 40 uF). Connect these two in shunt with the woofer.
I recommend a second-order filter, as filter frequency is not a function of actual driver impedance, only Q (damping) is.
Per ohm (at 350Hz), use inductor (L) of about 0.85mH for critical damping (larger = overdamped, smaller = underdamped). and C=1/(2*pi*350Hz)/L. Connect the capacitor in shunt with the woofer and the Zobel network (3 parallel paths), and the inductor in series with the works.
To quantify the example, my component choices, assuming you have about 6 ohms DCR and 1.5 mH VC inductance;
parallel paths:
path 1 = woofer
path 2 = 6 ohm + 40 uF
path 3 = 33 uF
and hook the whole shabang in series with 4.5 mH inductor.
If you get a dual voice coil (say, 4 ohms each) woofer, halve the resistance and inductance values, double the capacitance values, and connect two complete and equal networks, one to each voice coil and amplifier channel respectively.
Choice of frequency is inveresely linearly proportional to inductance and path 3 capacitance (filter frequency= 1/(2*pi*sqrt(L*C)).
The whole thing is more involved in truth, but my impression is this is the sort of analysis you are seeking... This is a definite finger-in-the-wind approach, but it won't blow anything up and may even sound OK.
Have fun!
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