@perrymarshall
I am using 2 no eminence alpha 15A in parallel with FR. Would I be able to use this circuit with 4ohms or shall I do series and make 16ohms and try it out?
I am using 2 no eminence alpha 15A in parallel with FR. Would I be able to use this circuit with 4ohms or shall I do series and make 16ohms and try it out?
I'll assume you mean you're running the 15As as bass with a Full Range as a mid tweeter.
You would make the series vs parallel decision based on the sensitivity of the full range. Series if your FR is ~95dB. Parallel if your FR is ~101dB.
You can use a Passive Bass Boost circuit either way, but with some low impedance cautions. If you wire them in series then you use this circuit and double the inductor values and halve the capacitor values. If you wire them in parallel then you double the capacitor values and halve the inductor values.
The low impedance caution is that the 8 ohm woofer in this circuit has a 3 ohm minimum. Those woofers in parallel would dip down to 1.5 ohms, so you need an amp that can handle that.
You should simulate this on VituixCad or similar software before you build, if you possibly can.
I've tried similar with small Karlson ("K12 size") boxes but lower Q woofer - A Samson amplifier could almost "ratchet" if driven hard on a drum beat with Kappa12A - ~600uF/20mH. I remember nearby pliers to the steel laminate core "singing along"
This technique sounds like a great thing to do with open baffle when applied properly. Back in the day when things were cheap, Goldwood's GW1858 made a good open baffle woofer and its low mass shook the frame a lot less than a Pyle 21".
This technique sounds like a great thing to do with open baffle when applied properly. Back in the day when things were cheap, Goldwood's GW1858 made a good open baffle woofer and its low mass shook the frame a lot less than a Pyle 21".
Using a shunt inductor with the capacitor kills the impedance, but since it's highly reactive the effect on EPDR is horrific. I would say it's definitely better to not use the inductor if just a capacitor would suffice (the woofer is already inductive below Fs on the order of 25mH). Then you can use a smaller, cheaper capacitor, and you can't endanger an amp with just a series reactance. Far cheaper this way and safer for your amp.
Even if your speaker does not fit the criteria (besides being sealed), this can improve the sound - if your woofer has any inductance below Fs then the capacitor will boost. If just a capacitor does not lead to some improvement, then it's unlikely that adding an inductor will.
To avoid interactions with crossover shunt components, it may work better to use the capacitor directly in series with the woofer.
This is the result with a SIG180-4 in a 6.8L box. The pivot point at 85Hz is in-box Fs, the pivot point at 270Hz is the bottom of the woofer impedance. I think this demonstrates the "box too small" use case. 330uF or 500uF sounded best, with 330uF being cleaner and very controlled, whereas 500uF is more impactful and brings back the tom toms. I used bipolar lytics, it was not an issue.
Even if your speaker does not fit the criteria (besides being sealed), this can improve the sound - if your woofer has any inductance below Fs then the capacitor will boost. If just a capacitor does not lead to some improvement, then it's unlikely that adding an inductor will.
To avoid interactions with crossover shunt components, it may work better to use the capacitor directly in series with the woofer.
This is the result with a SIG180-4 in a 6.8L box. The pivot point at 85Hz is in-box Fs, the pivot point at 270Hz is the bottom of the woofer impedance. I think this demonstrates the "box too small" use case. 330uF or 500uF sounded best, with 330uF being cleaner and very controlled, whereas 500uF is more impactful and brings back the tom toms. I used bipolar lytics, it was not an issue.
You certainly have to consider this issue, but surely it depends on the specific use case and values in question? Modelling suggests to me that you will almost certainly need some resistance in series with the shunt inductor, but I think the inductor is still a possible strategy. No?
It's possible, but you can very easily end up with a worse load than a 2ohm speaker. It just depends on how well damped the LC filter is. The problem is that to have any peaking, the LC filter cannot be damped. An undamped LC highpass filter becomes a series resonator loading the source. In this scenario, multiply the inductor resistance by 0.39 and that is the worst case equivalent load resistance in terms of average power (not even peak power which is EPDR). If we leave out the inductor, the series resisance is equal to the woofer resistance which means your EPDR does not get any worse than the woofer already is.
I'm interested if anyone can come up with a scenario where adding the inductor is an improvement in response compared to just using a capacitor. In my simulations I didn't see it. When you add the inductor, you are putting it in parallel with the woofer's motive inductance. So the inductor reduces the overall inductance seen by the capacitor. We go through all the trouble to pick the largest inductor we can find just so we can reduce the inductance that is so important for getting the desired effect.
One thing I won't deny is that this is an effective subsonic filter and will reduce intermodulation caused by sounds lower than a typical woofer can reasonably produce, if it's not a special woofer.
I'm interested if anyone can come up with a scenario where adding the inductor is an improvement in response compared to just using a capacitor. In my simulations I didn't see it. When you add the inductor, you are putting it in parallel with the woofer's motive inductance. So the inductor reduces the overall inductance seen by the capacitor. We go through all the trouble to pick the largest inductor we can find just so we can reduce the inductance that is so important for getting the desired effect.
One thing I won't deny is that this is an effective subsonic filter and will reduce intermodulation caused by sounds lower than a typical woofer can reasonably produce, if it's not a special woofer.
A capacitor all by itself won't boost an Eminence Alpha 15A by 5.5dB as shown here
I get at most 2-3dB.
I get at most 2-3dB.
True, but that is a narrow peak that rings. This is not what I had in mind when I asked for an improvement. The peak height and sharpness increases as the LC filter is less damped. You are trading all your EPDR for a wolf note at 50Hz. I'm sure it has a subjective impact and sounds good in it's own way, but I would prefer a shallower but broader peak which is what you would get without the inductor.