Hi there. I'm going to build a subwoofer and hook it up to an amp that doesn't have low pass built in. I know this has been asked countless times, but could someone point me in the right direction? Would going for a line level low pass or an internal low pass be cheaper or is one better for noise? And is ebay the way to go or could I get better components if I go DIY? Thanks in advance.
Both have pros and cons: low level filtering is cheaper but requieres extra dedicated amplifier. High level requieres no amp but call for inductors and capacitor, often with a little headache.
How much of a headache is making a high level low pass? And can I just buy these on ebay? I'll be pushing over 600W by the way, so I doubt any ebay filter could handle that anyways.
A high level low pass (aka woofer crossover) is just a series inductor for a first order crossover.
Second order crossovers require both a series inductor and a shunt capacitor.
Does the 600W amp only drive the woofer? If so, a line level active crossover would be better, if properly done.
If it's just a series inductor then that's a hell of a lot easier than I thought. Are there any calculators you could point me towards, where I can just plug in some specs and it tells me what inductance I need? E.g. for -3dB 80hz at 8ohm I need x inductance? And same with power - am I looking for a certain voltage the inductor is rated for?
This should get you going on the first order low pass with an inductor.
You can start out with that, and if it's satisfactory, that's all you need.
https://www.omnicalculator.com/physics/crossover
Some inductor examples:
https://www.parts-express.com/speak...inductors/solid-core-inductor-crossover-coils
You can start out with that, and if it's satisfactory, that's all you need.
https://www.omnicalculator.com/physics/crossover
Some inductor examples:
https://www.parts-express.com/speak...inductors/solid-core-inductor-crossover-coils
I'm probably wrong here, and forgive me if I am, but does that calculator do what I need? There's only one driver - a 600W RMS 1200W peak subwoofer - being powered by a bridged 1000W amp, which is the t.amp E800. That calculator doesn't give me a 1st order low pass when I select one driver, only zobel and L-pad? Is that what I want? The diagrams show more than just a series inductor.. I might be wrong, I'm new to DIY audio
Easy, but a first order crossover only drops six dB per octave (assuming the sub does not have a rising upper response) and you will hear vocals through your sub, which probably won't sound good, especially if you want to pump 1000 watts through it.
12dB per octave (second order) is the minimum you should bother with.
24dB per octave (fourth order) would be better, but doubles the parts count and increases passive losses.
The cost of good capacitors and inductors that can handle over 150 volts may exceed what an active crossover would cost.
What's your definition of a "Sub-woofer" ?
Because if you are aiming for the octaves below 80Hz a dedicated electronic crossover can be a lot cheaper than going passive when high power is concerned.
A Citronic could cost as little as 99 quids and second hand maybe half that. I shudder at the thought of buying a cored inductor to handle a killerwatt
Because if you are aiming for the octaves below 80Hz a dedicated electronic crossover can be a lot cheaper than going passive when high power is concerned.
A Citronic could cost as little as 99 quids and second hand maybe half that. I shudder at the thought of buying a cored inductor to handle a killerwatt
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If it's a single subwoofer for stereo equipment, there is also the issue of mixing stereo down to mono. You need a double-voice-coil driver or two drivers for that when you use passive filters after the amplifier.
I'll never understand why people need such high power levels, unless it's for a PA application: causing hearing damage to a hall full of people.
I'll never understand why people need such high power levels, unless it's for a PA application: causing hearing damage to a hall full of people.
So, how do you mix stereo to mono in a passive loudspeaker-level crossover without DC shorting the amplifier outputs? It's easy with a line-level crossover filter, but I don't see how you could do it with a loudspeaker-level crossover, not in a practical manner anyway.
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I won't be pushing anywhere near 1000W. 600W peaks for very short amounts of time occasionally. In normal use 100W will be fine, it's just fun to crank it up. Also, maybe for HT I'll need decent SPL, 105dB at a few metres, which needs a bit more juice
Would something cheap like a soundking pocket DSP work? And are dirt cheap aliexpress DSPs maybe a better alternative?
About 100 years ago I made someone a vented box for a Cerwin-Vega woofer and used a passive line level xo aka PLLXO before the amp....
I would go line level active. But for testing, you can use even simple passive filter before the amp. It will reduce signal a little, but for testing its ok. I actually used it with simple jfet preamp (hamptone, i made pleanty spare) and still use it. So simple pre, passive subwoofer filter, amp.
I posted it in 'whats on bench tonight' thread, i guess.
https://www.diyaudio.com/community/threads/whats-on-the-bench-tonight-obt.372508/post-7412387
Are there any line level amps available on amazon or ebay or would I need to make one myself?
This is a bit ghetto but might work - hook up my speaker’s amp up to a sound card’s L+R channels, and then the subwoofer amp to the center channel. Use equalizer APO on my PC to low pass the center channel and high pass the L+R channels. Problem solved.
Only thing is, I don’t know how noisy the USB 5.1 cards on amazon are, and what alternatives are cheap enough to fit my budget, ideally under £40.
This is a bit ghetto but might work - hook up my speaker’s amp up to a sound card’s L+R channels, and then the subwoofer amp to the center channel. Use equalizer APO on my PC to low pass the center channel and high pass the L+R channels. Problem solved.
Only thing is, I don’t know how noisy the USB 5.1 cards on amazon are, and what alternatives are cheap enough to fit my budget, ideally under £40.