I'm planning on building a sub to complement my KEF Q150's. This is for listening, not for home theatre; basically to remove the low-end from the coaxials to reduce distortion. I've been playing around with different designs and drivers and it looks like if I have a ported enclosure, the drivers will absolutely shred themselves (exceeding xmax) at a decent volume if there's any signal below around ~15 Hz. Should this be a concern? I was going to use the plate amps from Dayton Audio for their high level input, but I would also enjoy building it myself if it's not too hard (probably from an amp board).
I may also just use a sealed box. Since it's for stereo I'm not expecting much signal below 40 Hz anyway, right? So an f3 of 40Hz would be good enough?
I may also just use a sealed box. Since it's for stereo I'm not expecting much signal below 40 Hz anyway, right? So an f3 of 40Hz would be good enough?
Don't be worried about it. Extremely few non-film sources have subsonic info. I have heard that some music recordings have some rumbling from e.g. nearby metro/subway trains in very low frequencies but I doubt you will come across them.
If you do have trouble in the future, it's really easy to add a line-level opamp-based active high-pass filter. DC wall wart, project box, a small piece of Veroboard, a few connectors, done.
If you do have trouble in the future, it's really easy to add a line-level opamp-based active high-pass filter. DC wall wart, project box, a small piece of Veroboard, a few connectors, done.
Warped vinyl LPs can trouble a ported sub because its driver is acoustically unloaded at very low frequencies. Best not to go too low unless you have a rumble filter on your amp.
+1, but any rumble filters I've plotted don't have a sharp enough slope, DSP excepted. (Are there members out there without DSP?)
The right cut-off starts just above the system resonance. No right-thinking audiophile would want to play a system with a resonance inside the listening band. But that speaker would have to have a system resonance at 5 Hz if you want little to be lost at 20 Hz.
For all the rest of us, slicing off some power as high as 30 or even 35 Hz would not be noticed, but the improvement in the system by removing LF garbage from the signal might be noticed.
B.
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I'm not a nerd so I'm often perceived of one who asks dumb questions but and asks members to consider unconventional variables. However, I am experienced (old) enough to ask members to consider alternative variables. The only scenario in which your issue could be a real "thing" is when playing vinyl. If any of your music is mp3 based, a large part of the algorithm focusses on removing the frequencies you cannot hear. (1) What are the specifications of the tone arm? (2) What are the specifications of the amplifier? If your amp does not efficiently
amplify signals below 20hz then your speakers are unlikely to be adversely affected by them*.
*Learned that when replacing the amp on a Bose active sub. The original amp had a stated frequency response of 25hz to 20khz. The 20/20 amp I replaced it with displayed different dynamics.
amplify signals below 20hz then your speakers are unlikely to be adversely affected by them*.
*Learned that when replacing the amp on a Bose active sub. The original amp had a stated frequency response of 25hz to 20khz. The 20/20 amp I replaced it with displayed different dynamics.
Would I be better off doing that or trying to build an active line-level crossover (and channel mixer)? Was thinking about building an active set of speakers down the road sometime, would be good practice. It'd also open up more options in terms of amps.
I may also just go with a closed box... it's for music anyway, so smooth bass is my priority over more bass. Is a 15" going to be too slow when paired with my 5.25" woofers?
No, those are good questions. My music is mostly Vorbis and FLAC. I'm brand new to vinyl ("it's still in the mail" new), so what specs are relevant?
For the amp, the frequency response isn't listed anywhere that I can see outside of the range of (low pass) crossover frequencies
If you build an analog system, copy the simple APT infrasonic filter here.
This filter is 18dB/octave set at 15Hz. The corner frequency can be scaled by changing the R/C proportionately.
APT Corporation Holman - Manual - Stereo Pre Amplifier - HiFi Engine
This filter is 18dB/octave set at 15Hz. The corner frequency can be scaled by changing the R/C proportionately.
APT Corporation Holman - Manual - Stereo Pre Amplifier - HiFi Engine
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Your ported KEF Q150's haven't shredded themselves with content played well below Fb (around 50 Hz), so probably no real concern.
There's plenty of content in pop music an octave below that, 20- 25 Hz is pretty common this century.
Most "subwoofers" suspension will allow quite a bit of travel past Xmax without damage (Xmech or Xlim). Just like your Q150's, they will distort when driven past Xmax, not shred.
The KEF Q150 max out around 108 dB at one meter, the pair around 114 dB.
Design for at least 114 dB within Xmax down to 25 Hz and you should be good to go without even worrying about a HP filter.
Size of the woofer has nothing to do with "speed", but for good control, look for high Bl figures.
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Building your own active crossover is something you do if you want to tinker with electronics and soldering. If you just want a system that works, today, DSP is what you should go with.
I mean... if you're OK with less flexibility and greater time investment, active may (and I mean *may*) cost you less.
Ignoring the lousy performance, the fact it is likely an electric organ, and the antiquity of the recording.... it's the usual case of middle-low bass sounding real impressive, as is so often touted here with pop bass guitar recordings being loud at 80 Hz being mistaken for low bass.
The real-time analysis attached show some content at that low note around 32 Hz but not a lot above the ambient hall noise below that. For the pedals to contribute to a sound as delightful as a great organ concert at St John the Divine in New York or St Pauls in Toronto, they need an RTA that is quite a lot higher than anything here.
The attachment is the first 45 seconds roughly of the YouTube.
Conclusion: you need to do an RTA before offering a post about low bass.
B.
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Please pay no attention to the horrible YouTube clip. I was actually referring to the original. Back in the late 70's I got hold of a master of Fox's original work on RtR. The sound of the 32 footers was amazing if you had a great subwoofer system. I was playing around with multi amped systems back then, and had a bass system that used multiple RTR 12" woofers with passive radiators, all stagger tuned, 4 per side, each pair driven be a Marantz 510M with a 80 Hz @ 24 dB/Octave LP. I actually did structural damage to my folks house!
Most power amps give you second order filtering for free - the first is the DC blocking cap and the second is in the feedback, where the gain is usually rolled off to unity at DC. It would be worth choosing these carefully to limit cone excursion
Brian
Brian
It should be in the amps specs somewhere. e.g. I was considering using a TPA3118 board as part of an active subwoofer. However, the frequency response of the amp is stated as 35Hz to 88Khz; indicating if there was any rumble the amplifier was incapable of processing frequencies that low.