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hi-pass filters ?

#24
aledeville said:
Some preamps just have a massive low end. For instance the Fender TBP-1.
Thumpinator and we're good to go!
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Exactly. Maybe a cab can handle the low end, maybe an amp has adequate highpassing in it, maybe you can dial it out with eq, maybe your situation won't require it, but for the minimal price of admission, why not have such a handy little tool that can apply its subtle magic and help so many problems.
 
#25
Wolffgang said:
Exactly. Maybe a cab can handle the low end, maybe an amp has adequate highpassing in it, maybe you can dial it out with eq, maybe your situation won't require it, but for the minimal price of admission, why not have such a handy little tool that can apply its subtle magic and help so many problems.
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This pretty much sums it up. The FDECKIII is great since you can run it on batteries, it is VERY transparent, and it is adjustable.

Most head/cab combinations won't benefit much from the pure hi passing function (i.e., rolling off deep sub-bass elow 35hz) IMO and IME, but a few will (older SWR heads, older EA heads, and a few others that have very low internal hi passing). However, with the variable hi passing control of the FDECK that goes all the way up to 100hz+, it is a handy tone control (for example, to make a ported cab somewhat emulate a sealed cab, or can 'tune' a head to a very midrange voiced and/or low quality box that can't reproduce much true bass by cutting out even mid bass from your signal chain). It can be a very powerful tool combined with a typical shelving bass control on the typical bass amp.

I ended up selling mine since my amp/cab combinations work wonderfully without it (i.e., didn't really notice a difference with or without it), but I like a full, deep low end and use 'intergrated heads designed for bass' that are well controlled down low.

For those using preamps with PA type power amps, this would be a VERY good tool.
 
#28
Zooberwerx said:
Yes, and keep in mind that more than a handful of power amps and peripherals have defeatable HPF's on board. IIRC, the QSC RMX has a selectable 30 / 50 hz filter and both my dbx crossover and Peavey GEQ had 40 hz filters.

Riis
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+1, although those limited, fixed HP start points may or may not be optimal. For example, with a small, mid voiced cab, 30hz is too low, and for most, 50hz will actually impact the tonality of the low end of the instrument (which may or may not be a good thing).

40hz fixed is probably a good 'pure hi passing' start point for most regarding 'optimal performance and speaker 'safety' without actually impacting the tonality of the low end.

That is one of the big advantages of the FDECKIII, the ability to have true hi passing at variable freq start points.
 
#29
guy n. cognito said:
Remember the TB Amps forum credo: Build a cabinet capable of extreme low end reproduction and excursion, then add a HPF to take it all out!!!!!!!



;)
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To be fair, and based on the above post (i.e., PA amps having limited hi pass variability), a cab that can totally hammer at 45 hz, and a variable hi pass set to 40hz or so with massive power can be a pretty amazing thing for those how like to pound the low end at high volumes. I get that for sure.
 
#32
The big difference between the "regular" tonecontrols or eq's and a wel designed HPF(or subsonic filter) is that the latter has a steeper slope, at least 24dB/oct (48db/oct would be even better). This combined with a practical corner frequency for bassguitar(e.g. 35hz) and your set.
 
#33
Arjank said:
The big difference between the "regular" tonecontrols or eq's and a wel designed HPF(or subsonic filter) is that the latter has a steeper slope, at least 24dB/oct (48db/oct would be even better). This combined with a practical corner frequency for bassguitar(e.g. 35hz) and your set.
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The FDECKIII is cool because it has a fixed -12db cutoff at 35hz, and then an additional variable -12db cutoff above that, all the way up to 100hz+. So, if you set the variable control to 35hz, you have the classic -24db cut at 35hz. Nicely designed unit that combines the classic 'sub bass rolloff' function with an additional 'tone control' type function. Nice stuff.
 
#36
Don't get me wrong...I think Fdeck's HPF is probably great, and if you're in a situation that could use one, I wouldn't try to talk anyone out of getting one because it does beat spending a few hundy on a different cab. But as much as it pains me to admit it, I often read these HPF threads and think exactly what Guy said ;)
 
#39
JimmyM said:
Arrrgggghhh! I hate when people "fix" my words! If that's what I wanted to say, I would have said it.

:D
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Fixed it. ....wait, no just kidding! No disrespect intended, Jimmy. :cool:

Like you I haven't ever blown a driver, even though there have been four times I thought I had. I like my HPF because I play a lot of reggae and boost the lows. It can tighten the bottom, plus I get protection from subsonic power suck and transients. The cabs I use a lot are tuned in the low 40s. :ninja:
 
#40
guy n. cognito said:
Remember the TB Amps forum credo: Build a cabinet capable of extreme low end reproduction and excursion, then add a HPF to take it all out!!!!!!!
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I'm conscious of that point when I design my own speakers. From a "pure engineering" standpoint, if your speaker has too much low end, and you're using aggressive HPF'ing as a tone control, then you could have gotten a speaker that's smaller, cheaper, louder, etc. What seems more typical among electric bassists is to set the HPF to a point near or below the lowest fundamental of the bass, so it's not really serving a tone shaping function in the most familiar sense.

It makes sense to consider amplification as a "system" that consists of amp, speaker, bass, fingers, ears, etc. The design goal is to deliver a system that sounds good and addresses practical tradeoffs. Historically, bass speakers were designed to manage the tradeoff between low frequency reproduction, and protection of the cone and port from signal extremes.

Some folks find that the way historical speakers were designed, defines the "classic" tone of the electric bass. Others find it to be intolerable. ;)

For instance, in the classic Ampeg "fridge" system, 1) the speaker is an electromechanical HPF with cutoff set high enough to control the lowest fundamentals. 2) The preamp doesn't goose the lows. 3) Handling 40 Watts per driver isn't an insurmountable design task. I'm not surprised that Jimmy doesn't need an HPF.

Nowadays, there are other ways to manage speakers as well. Given contemporary technology, electromechanics are big, expensive, and hard to adjust, whereas small-signal electronics are cheap and flexible. By liberating the speaker of having to protect itself from infrasonics, and moving that functionality into the electronics through use of an HPF, the speaker can be pushed towards even higher performance, or (also as a viable option), smaller size and lower cost.

Again, this is all from a "pure engineering" perspective, and doesn't address the wide diversity of preferences for tone quality and other subjective factors that make bass amplification such a fascinating subject.
 

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