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High pass filter


WCunha

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http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=266-248

 

The amazing thing is that....they actually work!

 

The 30hz filter will stop excessive cone excursion

but you won't really hear any tone change.

 

The 50hz filter will help tighten up a boomy room tone.

 

I use a 50hz through the effects loop of my SWR SM500 and it works great as a variable low cut filter dependint on where the effects blend knob is.

 

If this is by chance related to your purchase of an Acme cab....this is EXACTLY what you need.

 

Get the 50hz unit. I have a BUNCH of Acme and that little jewell is a god-send. You won't believ how crisp and accurate Acmes sound once you get all that sub-low out of the way and you'll still have bottom end for days.

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You could add a capacitor- that's the simplest HP filter there is. Granted, it's not a wonderful filter by itself, but it's very easy to add in. Make sure that you use audio grade NON-POLARIZED caps, such as those used for crossovers.
...think funky thoughts... :freak:
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Originally posted by WCunha:

How much difference is there between 30hz and 50hz? And don't say 20hz :D . How much low end will be lost?

 

Wade

It depends on the "slope" of the filter. No filter is perfect. A filter set at 50 Hz doesn't cut all sound below 50 Hz. It cuts 40 Hz a bit, 30 Hz more, and 20 Hz even more. Some filters have a "steep" slope. In this case, 30Hz would get much more cut than 40 Hz. Other filters have "gentle" slope, so that 40 Hz would be cut a little, 30 Hz a little more, etc.

 

Engineers often use high pass filters when mixing, and not just on bass. They might use it on an organ or synth track to open up room for the bass or kick. Or they'll use it on bass to get rid of frequencies that can't be easily reproduced on most home or car stereos. Most bass players are oblivious to this trick, but it's very common, and the records still sound "good" to our ears. The bottom line for mixing is that everything has to "fit" in with everything else. That's one reason by P and J basses are so popular. They fit well with other instruments with a minimum of EQ.

The Black Knight always triumphs!

 

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  • 7 months later...

Been thinking more and more about those real sub-bass lows and their overall affect on the tone. bikertrash is a keen exponent of 50Hz high-pass filters on Acmes for crazy tightness and volume yet masses of low end and it's been making me ponder. Also, been listening back to the various live recordings of my rig in action and there is a somewhat excessive amount of ultra-lows, not boom per se because the sound is remarkably tight but it's still more wallowy than I'd like.

 

So, I've done some experimenting with matching the 50Hz filter on my QSC with some EQ on Cubase and listening through headphones (which go really low) the tone loses a minuscule amount of weight whilst gaining a usefully larger amount of 'nimbleness' for want of a better word. The EQ is basically a 0.5dB boost at 100Hz with a very gradual slope up to that from 200Hz, and then a filter which is flat at 60Hz, -3dB @ 50Hz, -6dB @ 40Hz, -10dB @ 30Hz etc.

 

I only play 4-string and had always wanted my rig to be very accurate right down to the lowest notes but it seems that such extreme low end has very little musical value. It's not like you feel it that much either, its more like the earth-shaking gently than like standing agaist a kickdrum.

 

I have a suspicion that this is more of an issue due to my Warwick's wenge neck-thru construction and active pickups which both conspire to put out a lot more fundamental than a bolt-on, maple-necked, passive bass would. (IIRC, your typical Fender puts out about 3-6dB less fundamental than second harmonic on the low notes, whilst at the other end of the spectrum an ebony neck-thru (that's ebony neck not just fingerboard) Alembic puts out equal quantities of fundamental and second harmonic.

 

Now I need to find a gigging opportunity to test the new theory in anger - I'm looking forward to having a useful amount of extra punch, clarity and LOUDNESS... ;)

 

Alex

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I would tend to agree that cutting lows on recordings is generally a good thing. I've seem cases where you simply couldn't get the bass signal high enough in the mix because all the extreme lows get in the way.

 

However, I also believe that live sound and recorded sound are two different things. I would generally not cut lows in a live situation, or at least not to the same extent that I would with recorded material. Just MHO though...

 

Dave

Old bass players never die, they just buy lighter rigs.

- Tom Capasso, 11/9/2006

 

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Originally posted by SteveC:

30, but with the cab rated to 42 or so, I could probably go 50.

I've always used the 30Hz filter until now but having done some highish volume comparisons I'm going to go with the 50Hz filter henceforth. There's slightly less fundamental to the lowest notes, but you'd be hard pressed to tell unless you're listening for it, and the extra tightness to the sound is nice. Plus it reduces the cone movement massively, even when my bass knob is cranked. Give it a whirl and see how the Berg likes it!

 

Alex

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This is why I'm looking at QSC because they have two filter switches on the back, 30hz and 50hz.

 

After an extensive read of the PDF manual online I've determined that my first settings upon start-up once I get everything, will be to have both of those switches ON. Then adjust EQ on the pre-amp to flat, with then play with the low freqs, cut some mids a little, see what happens.

 

I am thinking I should have a very tight bottom end-which is good on not just basses-and I can boost the low freqs on the EQ or my active bass if I want more lows.

"The world will still be turning when you've gone." - Black Sabbath

 

Band site: www.finespunmusic.com

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I appreciate the thanks and I wish I could take credit for the discovery but...that was a tip I picked up from a post at talkbass. I can't remember who it was but thats the guy we all need to thank.

 

You ever notice that people have the same gripes about Acme cabs that they do about sound guys mixing bass? Muddy, indestinct, lost in the mix. ect.?

 

I think the majority of what get's blamed on the sound guy's is our own fault because we give them mud to begin with. Chances are if you use a "normal" bass cabinet you don't realize it because your cabinet just can't reproduce it. The cabinet itself acts as a sublow filter up until the point it tears itself apart trying. Acmes, like PA subs CAN reproduce it.

 

Think about it for a second. Active basses and 5 strings especially are all about lower lows and higher highs. Highs never hurt anybody but lows...I don't think the human ear and brain have what it takes to process all that low frequency information as well as it does in the frequency range of the human voice or what normally exist in nature. It's an evolution thing.

 

Add that to the the kick drum contests that sound guys seem to measure each others johnson by and you get...what we all complain about.

 

I've gotten to the point where I'm insane with low cut filters. My big rig is set with the 30hz sub filter engaged on my SWR Grand Prix, The 50hz filter engaged on my PLX 2402 AND a 50hz FMOD run through the effects loop!

 

Common sense would tell you that my Sadowsky 5 must sound like a mandolin. It doesn't. I send the house the post EQ from the Grand Prix and the house gets essentially the same spectrum that the Acme gets from the PLX filter. The more I cut, the better sound guy's and other people with real ears like it. You can't make me muddy and indestinct. The frequencies just don't exist in the signal chain. The only really audible effect it has is on the last 5 notes of the B string which just get more clear, not at all "thin" sounding.

 

If I boost low end, I get more low end with ZERO mud.

 

I've been gigging since I was 13 years old and I just turned 46. The realization that in order to get more usable low end....you need to cut low-low end...is the greatest tonal epiphany I've ever had.

 

You ever wish you could get some more beef without all the boom?

 

You want to have sound guys come up to you over and over and over again and tell you that you have the best sounding bass they have ever heard?

 

You want the sound guy to put you on top of the kick drum instead of underneath it?

 

You want to walk up the the house console and see your channel EQ flat and untouched because the guy just can't get it any better?

 

Not only can you get all that for less than the price of a set of strings...you get it twice because there's two in the pack.

 

How about this, I have an extra one. If you don't believe me and you want to check one out give me your address and I'll send you my extra one. If you like it buy one. If it doesn't work for you send it back to me or agree to send it to the next guy that wants to check it out and we'll just pass it around the forum.

 

Keep in mind that these things are only available in RCA end so, the cost of the adapters to change it to 1/4 inch are on you

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Wow very cool explanations. What filter do you recommend for a cab that is capable of 30hz? Cab is Carvin BRX12 (2x12"). If it can produce 30hz do I even need one? My head is a B1500 w/the subbass knob @ 50hz if that matters. Thank you for enlightening me.
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Those things are a line level device only so it's got to go somewhere in front of the amplifier output to the speaker.

 

I chose my effects loop because it's variable and I can tune it to my mood or the room. If I'm outside I back it off a little to make up for what you loose by not having help from acoustic coupling due to walls.

 

I never got any sonic benefit from the 30hz filter from my QSC. I did get what I wanted from the 50hz filter but...that doesn't help me with the send to a house console

 

The thing is small enough...I've actually toyed with the idea of putting it inside the electronics cavity of my Tobias and Sadowsky for those times when you run into a sound guy that just insists I use his $20 Rapco DI box.

 

My revalation came from the use of a 5 string with my Acme cabs and also my Epifani 212D which also has low end for days. It was much less so when I used it with my Eden 210XLT or 115XLT boxes because despite what the published specs may say...they don't really put out enough down there to be really problematic. It still has great value for a FOH send.

 

In any case, it's an interesting study in physics to play with it and hear your sound get louder and tighter while you watch the speakers move less and the status lights in you signal chain come down.

 

Before y'all go out and flush the entire $20 there is, as with everything, a downside.

 

My rig is now extrordinarily unforgiving. It's like a Telecaster guitar through a fender twin. You hear it ALL. There's nothing to hide behind anymore. I've had more than one guy come to a gig, love the tone, want to sit in and then get killed with fret click, finger squeek and God knows what else he never even knew was there.

 

It's kind of funny in a sadistic kind of way to watch but it's not all that much fun when it's happening to you.

 

One other tip, if you try it and you thinks it's sucking the guts out of your tone, don't remove it before you try turning up a tone knob. You'll probably find that you can get back what you want and still leave the boom behind.

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I love my high-pass (low-cut) filter, but mine is built-into my Fishman Platinum Pro EQ Bass "stomp-box" so it sits in front of my amp (a simple Bassman 200 combo), rather than being between the preamp & amp as suggested by the original topic here. It is variable, so I can control the cut-off frequency. Love it!

 

Is there any reason the emphasis in this thread is on the use of fixed-frequency cutoff between preamp & amp (either at 30 or 50 Hz), vs. a variable cutoff before the preamp? Just wondering if the preamp re-introduces some sort of sub-sonic sub-harmonics...

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Originally posted by PhilMan99:

Is there any reason the emphasis in this thread is on the use of fixed-frequency cutoff between preamp & amp (either at 30 or 50 Hz), vs. a variable cutoff before the preamp?

It's just what our gear has, or how it can be tweaked. I would be very surprised to find a preamp creating subsonics which weren't already there, unless something was broken.

 

I don't think it matters where the high pass filter is placed, as long as it's before the power amp.

 

Alex

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What exactly do you think you are filtering out?

low e = 41 hz.

low b = 29 hz.

 

Uf a filter is called a 50 hz filter than 50 hz is at - 3db of the filter slope.

in otherwords a 50 hz filter will cut low e volume by more than half. This is not a recipe for good bass tone.

If you use these filters and don't hear any difference in the volume of your lowest notes than guess what? your speakers are already rolling off these frequencies.

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Originally posted by Big Daddy from Motown:

What exactly do you think you are filtering out?

low e = 41 hz.

low b = 29 hz.

low B ~ 31 Hz

 

Originally posted by Big Daddy from Motown:

a 50 hz filter will cut low e volume by more than half. This is not a recipe for good bass tone.

No, it'll cut the fundamental of low E by more than half. The change in tone and loudness will purely be a reduction in subsonic rumble and a marginal decrease in weight.

 

Originally posted by Big Daddy from Motown:

If you use these filters and don't hear any difference in the volume of your lowest notes than guess what? your speakers are already rolling off these frequencies.

I'm using Acme cabs which go deeper than most. There's isn't a reduction in volume but there is a reduction in demand on the power amp. The SVT 8x10" has almost no response at low E fundamental but still sounds plenty loud.

 

Here's a frequency analysis of an open E on a Roscoe 5-string:

 

http://www.cafewalter.com/cafewalter/signals/estringfft.jpg

 

That's an active 5-string known for having some serious bottom and the fundamental of low E is still about 5dB quieter than the second harmonic.

 

Here's some mixing tips which also throw light on what's going on in the 'bass' region:

 

20 Hz and below - impossible to detect, remove as it only adds unnecessary energy to the total sound, thereby most probably holding down the overall volume of the track

60 Hz and below - sub bass (feel only)

80(-100) Hz - feel AND hear bass

100-120 Hz - the "club sound system punch" resides here

200 Hz and below - bottom

250 Hz - notch filter here can add thump to a kick drum

150-400 Hz - boxiness

200 Hz-1.5 KHz - punch, fatness, impact

800 Hz-4 KHz - edge, clarity, harshness, defines timbre

4500 Hz - exteremly tiring to the ears, add a slight notch here

5-7 KHz - de-essing is done here

4-9 KHz - brightness, presence, definition, sibilance, high frequency distortion

6-15 KHz - air and presence

9-15 KHz - adding will give sparkle, shimmer, bring out details - cutting will smooth out harshness and darken the mix

 

 

Instrument Specific

 

 

Voice: presence (5 kHz), sibilance (7.5 - 10 kHz), boominess (200 - 240 kHz), fullness (120 Hz)

 

Electric Guitar: fullness (240 Hz), bite (2.5 kHz), air / sizzle (8 kHz)

 

Bass Guitar: bottom (60 - 80 Hz), attack (700 - 1000 Hz), string noise (2.5 kHz)

 

Snare Drum: fatness (240 Hz), crispness (5 kHz), sharpness (7 kHz), Cut at 1kHz to remove jangling

 

Kick Drum: bottom (60 - 80 Hz), slap (4 kHz)

 

Hi Hat & Cymbals: sizzle (7.5 - 10 kHz), clank (200 Hz)

 

Toms: attack (5 kHz), fullness (120 - 240 Hz)

 

Acoustic Guitar: harshness / bite (2 kHz), boominess (120 - 200 Hz), cut (7 - 10 kHz)

 

And here's another frequency analysis, this time just looking at the low frequencies produced by the open E on a Jazz Bass:

 

http://www.spiderplant.net/alex/jazzespectrum.jpg

 

Alex

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I *LOVE* a nice warm, phat low EQ flat-wound sound. At live volumes (even in a modest Church setting...) though, the EQ needs at "high" volumes are different than at low volumes. This is sort of like the need for the "bass boost" button on your stereo at low volumes, but not at high. Just backing-off the low EQ doesn't do it for me on my (humble) rig - I need the high-pass. Others with a good parametric EQ may not need this, if the parametric portion is not just in the mid-range frequencies.

 

I have an adjustable high-pass filter on a stomp-box of mine (compressor/EQ) - not sure what the frequencies are at various knob positions, but I know it really helps "tighten" my sound when I adjust it to my liking.

 

On the other hand, I see a lot of kids these days putting sub-woofers in their cars, so I guess many people *want* the sub-sonic bone-rattling stuff. Not me though.

 

Your actual mileage may vary...

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Originally posted by PhilMan99:

On the other hand, I see a lot of kids these days putting sub-woofers in their cars, so I guess many people *want* the sub-sonic bone-rattling stuff.

But is it down to us to do the really subsonic bone-rattling or should we leave those last few Hz to the kick drum?

 

Alex

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