Passively, you can't boost, you can only attenuate. But boosting bass and attenuating midrange / treble is pretty much the same thing.
So if you want to attenuate 3db at about 150Hz and higher, you could use a coil and resistor in parallel with each other, attached to the driver's red / positive terminal. The value of the coil determines the frequency, the resistor determines the amount of attenuation.
This also happens to be the same as what's called a baffle step compensation (BSC) circuit. You might be able to use a BSC calculator to determine the values you need, for example:
Difraction Loss / Baffle Step Compensation (BSC) Circuit Calculator
So if you want to attenuate 3db at about 150Hz and higher, you could use a coil and resistor in parallel with each other, attached to the driver's red / positive terminal. The value of the coil determines the frequency, the resistor determines the amount of attenuation.
This also happens to be the same as what's called a baffle step compensation (BSC) circuit. You might be able to use a BSC calculator to determine the values you need, for example:
Difraction Loss / Baffle Step Compensation (BSC) Circuit Calculator
What 'magic' acoustic load your sub uses ?
If it is sealed ,adding a cap before the speaker may help in lowering the first peak,together with very little stuffing inside ,so a high Qtc ,otherwise damped by heavy stuffing ,might make the sound punchy but not well extended .
So ,yes , a cap ( me too , I was thinking of it as a natural High pass filter ...)
may help in sealed boxes to extend low freq reproduction .
If it is sealed ,adding a cap before the speaker may help in lowering the first peak,together with very little stuffing inside ,so a high Qtc ,otherwise damped by heavy stuffing ,might make the sound punchy but not well extended .
So ,yes , a cap ( me too , I was thinking of it as a natural High pass filter ...)
may help in sealed boxes to extend low freq reproduction .
Hmm this might be cheaper and more efficient, put the baffle step at the line input, looks like it turns the source into a 5k though.
Baffle Step Compensation
Baffle Step Compensation
How about just putting a capacitor in parallel with the speaker? Would this not short out anything but the low frequencies? Or could this somehow be dangerous to the amp?
I'm thinking of trying this with headphones for my iPod to have the effect of a bass boost. The volume is plenty loud enough (especially when using and in-line remote into the dock connector, which is much louder) but the bass to mid and treble ratio is too low. I have no idea what capacitor value to try using for 70 Ohm headphones though, or whether to try a variable capacitor.
I'm also thinking of trying a resistor, probably a variable resistor, in series with the capacitor to see if that can affect the shape of the frequency response curve, perhaps making it a less sudden low-pass, but I'll only have my ears to measure this. Or perhaps even multiple parallel capacitors with resistors. Can't remember the equations off the top of my head.
I'm thinking of trying this with headphones for my iPod to have the effect of a bass boost. The volume is plenty loud enough (especially when using and in-line remote into the dock connector, which is much louder) but the bass to mid and treble ratio is too low. I have no idea what capacitor value to try using for 70 Ohm headphones though, or whether to try a variable capacitor.
I'm also thinking of trying a resistor, probably a variable resistor, in series with the capacitor to see if that can affect the shape of the frequency response curve, perhaps making it a less sudden low-pass, but I'll only have my ears to measure this. Or perhaps even multiple parallel capacitors with resistors. Can't remember the equations off the top of my head.
re:'could this somehow be dangerous to the amp?' - yes, it'll short it out, $$$$
re:' variable resistor, in series with the capacitor' - this will change the turnover frequency; if you want to change the amount of low pass, the pot will have to be in parallel. This sort of thing is best done at line level, it's less likely to result in smoke
Baffle Step Compensation
re:' variable resistor, in series with the capacitor' - this will change the turnover frequency; if you want to change the amount of low pass, the pot will have to be in parallel. This sort of thing is best done at line level, it's less likely to result in smoke
Baffle Step Compensation
Yes, completely agreed. I might add that this way your filter sees a defined and constant impedance and will work like calculated. For a speaker load with it´s varying impedance you probably would need to simulate, measure, try different values etc. (time consuming and expensive).
Here is another link:
Loudspeaker Diffraction Loss & Zero PSRR
Thanks for the replies.
I'm thinking of using this in the context of headphones/earphones connected to an iPod. I'd have thought an iPod is designed to cope with the 3.5mm jack being shorted, or surely it would at least be fine if I put a small resistor (10 Ohms?) in series with the capacitor? You do after all get very low impedance earphones that don't wreck an iPod.
The idea is to make something that doesn't require any batteries and is small, ideally very small. At the moment I use the (cheap, tiny and battery-free) FiiO E1 Headphone Amplifier, which I think essentially just attenuates the iPod dock line out better than the iPod does internally and makes louder volumes available. It's plenty power for my headphones but I want to add a passive bass "boost" (by reducing mid and treble) without going to line level or involving any batteries.
I'm imagining a short cable that is only comprised of: cable, 3.5mm jack and socket, one or two capacitors (possibly variable/trimmer) and one or two resistors (probably one variable), perhaps simply enclosed in heat-shrink tubing with holes cut to access the variable parts with a screwdriver.
Basically I'm thinking is it not possible/safe/suitable to channel/dump some of the mid and high frequencies through a resistor and capacitor, whilst letting all of the bass and some of the mid-high into the headphones, thus giving the effect of a bass boost? (And a capacitor would be smaller and cheaper than putting an inductor in series with the headphones, tho maybe a small inductor would be better.)
When trying to design this circuit, is it accurate to represent the headphones as an inductor and resistor in series? I know the impedance is 70 Ohms at 1kHz, but I would need some other pair of values to calculate out the actual resistance and inductance, which I think I would need to know for calculating capacitor and resistor values. I was thinking I could just measure the headphones' DC resistance with a multimeter (when the reactance would be zero), but can't find mine just now.
It has now occurred to me that putting a capacitor in parallel with an inductor may create resonance and something that sounds a complete mess... hmm.
Is there any way to achieve a bass boost/enhancement/emphasis passively without seriously degrading the quality and without using batteries?
Thanks.
I'm thinking of using this in the context of headphones/earphones connected to an iPod. I'd have thought an iPod is designed to cope with the 3.5mm jack being shorted, or surely it would at least be fine if I put a small resistor (10 Ohms?) in series with the capacitor? You do after all get very low impedance earphones that don't wreck an iPod.
The idea is to make something that doesn't require any batteries and is small, ideally very small. At the moment I use the (cheap, tiny and battery-free) FiiO E1 Headphone Amplifier, which I think essentially just attenuates the iPod dock line out better than the iPod does internally and makes louder volumes available. It's plenty power for my headphones but I want to add a passive bass "boost" (by reducing mid and treble) without going to line level or involving any batteries.
I'm imagining a short cable that is only comprised of: cable, 3.5mm jack and socket, one or two capacitors (possibly variable/trimmer) and one or two resistors (probably one variable), perhaps simply enclosed in heat-shrink tubing with holes cut to access the variable parts with a screwdriver.
Basically I'm thinking is it not possible/safe/suitable to channel/dump some of the mid and high frequencies through a resistor and capacitor, whilst letting all of the bass and some of the mid-high into the headphones, thus giving the effect of a bass boost? (And a capacitor would be smaller and cheaper than putting an inductor in series with the headphones, tho maybe a small inductor would be better.)
When trying to design this circuit, is it accurate to represent the headphones as an inductor and resistor in series? I know the impedance is 70 Ohms at 1kHz, but I would need some other pair of values to calculate out the actual resistance and inductance, which I think I would need to know for calculating capacitor and resistor values. I was thinking I could just measure the headphones' DC resistance with a multimeter (when the reactance would be zero), but can't find mine just now.
It has now occurred to me that putting a capacitor in parallel with an inductor may create resonance and something that sounds a complete mess... hmm.
Is there any way to achieve a bass boost/enhancement/emphasis passively without seriously degrading the quality and without using batteries?
Thanks.
I've made a sketch of what I was thinking:
Is this sensible? Can anyone provide an equation for what effect this would have on the frequency response curve? Assuming I can determine Ro, Rh and Lh, then I have three values to play with. Of course I only want to reduce the mid and treble mild-moderately, not cut them out!
Thanks.
Is this sensible? Can anyone provide an equation for what effect this would have on the frequency response curve? Assuming I can determine Ro, Rh and Lh, then I have three values to play with. Of course I only want to reduce the mid and treble mild-moderately, not cut them out!
Thanks.
A serial cap will give a bass boost over a very limited range, it ca be used both in a sealed box or vented to get third and fifth order slope respectively. The boost is linked to have the cap interact with the impedance peaks and for a "skews" it to a lower impedance and thus more bass output. So it is a boost linked to a impedance reduction not an amplification, the rules of physics do rule.
There has been some articles in Klang & Ton about it and there should be something on the net about it.
There has been some articles in Klang & Ton about it and there should be something on the net about it.
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