CROSSOVER or FILTER?

[Lonesomedave]

hey guys, again, please excuse my ignorance but i really do not have much experience in this area.

i have a question about eliminating unwanted frequencies.

specifically i have heard that your speakers will last longer and sound better if you eliminate all unwanted harmonics/frequencies below about 25-30 HZ.

first of all, is this true?

second, how do you do it if your amp does not have such a filter?

could you fit your cabinet with a crossover of say 30 HZ which would only pass frequencies above that limit?

if so, how would you do it, where would you get it and about how much would it cost.

is there any other way to go about achieving the same result?

any thoughts or input would be appreciated.

/s/ Dave

 

[Downunderwonder]

You're talking about fundemental frequencies and extraneous thumpings. My main amp has oodles of EQ so I drop the 30 Hz right out and most of the 40 Hz which just make speakers flap without actually adding to the bass. A simple bass EQ pedal will take care of it for you.

You can build a passive crossover but it will soak some power and cost a few bucks

 

[Jim Nazium]

i have heard that your speakers will last longer and sound better if you eliminate all unwanted harmonics/frequencies below about 25-30 HZ.

That sounds like something that would have applied to home stereo systems back in the days of vinyl LPs. Bumping the turntable, or vibrations through the floor form a passing truck, etc. could cause the needle to move in such a way that it produced a very low frequency noise at a high amplitude that might damage speakers. Some phonograph preamps had an 'infrasonic' filter to prevent this.

The lowest frequencies produced by a bass guitar are about 30 hz if you have a low B, or 40 hz for low E. Regardless of that, if your speakers are "farting out" (over excursion of the woofers) you need to turn something down, either the overall volume or the bass frequencies. The tone controls on your amp should take care of it; there is no need to add an external filter. If your speakers are playing clean at your desired volume, you're fine.

 

[odk]

You are not looking for a crossover, but rather a High Pass filter.
This can be realised with a capacitor in series with the speaker input.
It will add phase to your signal, because 25 or 30 Hz are in very close proximity to 30.87Hz (Low B).
The filter has to attenuate only very low frequency content, without disrupting anything else, and with minimal phase shifting. For this you would have to plan a high order filter that will have a very sharp slope.

The filter can be designed as a passive filter, but when dealing with such low frequencies and high currents and voltages (at the output stage), this translates into very large and heavy filters (large caps and inductors).

The filter can also be realized in the small signal stage as an active filter (which means small size, but higher complexity).

 

[Lonesomedave]

downunderwonder-

ok, let's say i get this pedal:

now, this is a ten band eq pedal like what you said.

i have a question. do the 10 frequency sliders only affect the exact frequency they are marked?

say the second one which is marked 62.5 hertz. does that slider only cut/boost exactly 62.5 hertz or does it affect all frequencies from the first (31.25 hertz) up to the second slider? in other words, if i got this and cut the 31.25 all the way off to -12, would that eliminate all frequencies below 31.25 hz?

if it does that, it would seem to be the ideal solution.

sorry but i am new to this.

/s/ Dave

 

[odk]

No it does not.
These filters are band pass filters.
A band pass filter has a property that is calld Bandwidth, or Q.
The larger Q, less "frequencies" are affected by the filter.
A filter that takes care of a very small bandwidth, or a very high Q (say 60 to 65Hz), is called a notch filter, but I think you are looking for a high pass filter, not a band pass filter.

 

[Lonesomedave]

odk-

ok

so i need to know the "Q" of the pedal sliders on any particular pedal in order to make an informed decision?

are there any high pass filters that install easily and do what i want?

/s/ Dave

 

[odk]

hmm... maybe. let me get back to you on this one.
you should be aware though, that inserting this filter in the signal chain is better than nothing, but will not help you in case your amp is producing this harmful frequency content.

 

[dannybuoy]

Your search is over: [Invalid or Expired Link Removed]

Review here also: http://www.talkbass.com/reviews/showproduct.php/product/1568/cat/500

Most EQ pedals like the one shown above will have quite a wide Q point, meaning the bands overlap and a 30Hz slider will also reduce around 60Hz. The high pass filter in this steeply rolls off the subsonic lows leaving the rest of the signal intact:

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There's also a video where you can really see the difference it makes to the speakers: ‪[sfx] micro-Thumpinator‬‏ - YouTube

 

[Lonesomedave]

odk,

yeah, i know what you are saying. that's why i wanted something like a crossover to act at cabinet, that way wherever the frequencies are coming from they would be eliminated.

/s/ Dave

 

[Lonesomedave]

dannybuoy-

what the hell is it. it seems to do exactly what i am talking about.

is it a high pass filter?

and, where do i get one? they don't have any on ebay.

/s/ Dave

 

[billfitzmaurice]

hey guys, again, please excuse my ignorance but i really do not have much experience in this area.

i have a question about eliminating unwanted frequencies.

specifically i have heard that your speakers will last longer and sound better if you eliminate all unwanted harmonics/frequencies below about 25-30 HZ.

first of all, is this true?

Very true, and your amp will gain headroom as well.

how do you do it if your amp does not have such a filter?

With a graphic or parametric EQ in your effects loop.

could you fit your cabinet with a crossover of say 30 HZ which would only pass frequencies above that limit?

It would cost well over $100, the size of the components being so large. And to get the increased amp headroom the filtering must be done before the power amp, not after.

 

[dannybuoy]

dannybuoy-

what the hell is it. it seems to do exactly what i am talking about.

is it a high pass filter?

and, where do i get one? they don't have any on ebay.

/s/ Dave

It is a high pass filter, yes, one especially designed for this particular task. You have to order from the site I linked to which is based in the UK - although they ship wordwide. They don't come up used very often!

 

[Lonesomedave]

dannybuoy:

thanks, buddy. that thing looks incredible.

Bill Fitzmaurice:

have you checked out that micro thumpinator that dannybuoy referenced?

it looks amazing and seems to do exactly the job that i want. why the hell are they not better known and why the hell does every bass player not have one?

are there some hidden drawbacks to it that are not readily apparent? pending your reply, i am an absolute disciple of sfx on this one.

/s/ Dave

 

[staindbass]

i like the subsonic booms but really those frequencies are quite a bit down in level from what normal people hear and are used to. i dont think it would add that big of an advantage, and you would have one more circuit in the signal chain to add other crap you werent expecting. but when playing vinyl records its a big advantage to have a subsonic filter, warped records make the woofer cones pump and you cant even hear it, but you can see the cones stop moving/pumping when you switch on the subsonic filter.

 

[xk49w]

There is a TB thread about these. You really want an active filter designed for this purpose. TB thread by TBer fdeck. It is a 2nd order active HPF with an adjustable cutoff frequency. Full documentation and the design is on the link.

 

[Lonesomedave]

codger,

thanks also.

i am not sure whether you come down as against the micro thumpinator or are simply pointing out another product that also does what i want. could you please elaborate.

do you know how these two products compare, and what are the advantages of one over the other? just asking, if you don't have experience with the micro thumpinator i understand.

anybody? i would like to hear a comparison. thanks to everybody who has responded.

/s/ Dave

 

[dhomer]

One more item to consider. I know its been panned by some of the experts here, but this is what I have plugged into the effects loop, and it works

Harrison Labs FMOD-Sub

 

[sunbeast]

There is a TB thread about these. You really want an active filter designed for this purpose. TB thread by TBer fdeck. It is a 2nd order active HPF with an adjustable cutoff frequency. Full documentation and the design is on the link.

fDeck's HPF Pre is great, but was designed for use with piezo equipped upright basses, and not for the higher output of bass guitars. I have one and love it, but I bought it having conversed with him about the likliehood of an electric bass signal clipping his preamp. It is designed to clip smoothly (it isn't really noticeable to my ears), but if all you're looking for is a high-pass filter, ideally you probably don't want any clipping along with it! Had the Thumpinator been available when I was looking for a High-pass, I would have bought it instead- the roll off is steeper, and it is designed specifically for use with bass guitars. The one cool element of the fDeck HPF that I haven't seen on other micro HPFs is that the cutoff frequency is continuously adjustable...

 

[billfitzmaurice]

have you checked out that micro thumpinator that dannybuoy referenced?

Not personally. My amp has a parametric EQ, I use one band as a steep high-pass filter set at 35Hz.

One more item to consider. I know its been panned by some of the experts here, but this is what I have plugged into the effects loop, and it works

Harrison Labs FMOD-Sub

IMO it's better than nothing, far from ideal.