Bass vs mic preamps: what will I lose?

[greenboy]

The evidence that bass amps have high pass filters is that some print it in their specs (phil jones bass for example), some are switchable (acoustic image sweepable filter, GK deep switch for example), all the bass amps that have been scoped in Bass Gear Magazine show high pass filtering,

Gee, I lust have missed a few issues, because the ones I saw didn't have anywhere close to at least an 18 dB per octave dropoff at a useful frequency: ie a frequency that places the drop-off where a cab's drivers are otherwise going to unload (below box tuning).

I've seen a lot of plots that indicate faltering performance, or default voicing choices by the designer that begin falling off very shallowly well above a ported box's protection needs, but very few that indicate a good HPF. Not too many are building something that's going to keep a cab's drivers from unloading.

I did see an example of something that was decent for some lower-tuned cabs the other day though, ironically from SWR which has been noted for designing some heads which were kind of radical in the low end. I'll search for it.

 

[dincz]

On a budget? Me too. I use a Behringer BDI21 and a Samson Servo 300 power amp - and spent the money I saved on a decent cab (Barefaced Compact). Works for me.

 

[KJung]

Gee, I lust have missed a few issues, because the ones I saw didn't have anywhere close to at least an 18 dB per octave dropoff at a useful frequency: ie a frequency that places the drop-off where a cab's drivers are otherwise going to unload (below box tuning).

I've seen a lot of plots that indicate faltering performance, or default voicing choices by the designer that begin falling off very shallowly well above a ported box's protection needs, but very few that indicate a good HPF. Not too many are building something that's going to keep a cab's drivers from unloading.

I did see an example of something that was decent for some lower-tuned cabs the other day though, ironically from SWR which has been noted for designing some heads which were kind of radical in the low end. I'll search for it.

The key is to have a low end that is musically voiced for the bass guitar. Whether that is a voicing decision or HPF or whatever doesn't really matter to me. However, the low end filtering, however it is accomplished by all these amp manufacturers, really makes a difference in performance.

The ones that are way wide open on the bottom (Puma, EA iAmp800, SWR400, etc.) can be problematic IME, regardless of whether a cab can handle those low frequencies are not (I assume most can't).

If a given amp rolls off higher than necessary for a given cab, that doesn't seem like a problem (don't know the technical issues there) if it sounds good and tight and punchy, and most amps seem to have a nicely voiced bass shelving control that can bring the deepest bass up a few db if you really want that.

 

[greenboy]

The key is to have a low end that is musically voiced for the bass guitar.

That's more a brand's or player's tonal philosophy thing than anything that's deigned to protect a vented box from unloading. And being subjective as it is, some people will approve of some choices while others will dissaprove. Or better yet, some will find those choices suitable for some gigs and not appropriate for others.*

But pretty much anyone can agree, regardless of tonal preferences and what works well for them in a specific room, that they'd like to have better driver protection that doesn't make them gut the low end unless that's what they want, that provides an extra margin of safety, and clarity.

I should underline that CLARITY bit, because you can have quite extended bass that works well in a lot of types of mixes if you don't have all that extra non-useful energy below the box tuning also pushing the cone around.

I really must check out the GenzBenz units that have a selection for their HPF characteristics.



* Which is why some people are looking at other options like channel strips and mic/inst racks.

 

[KJung]

That's more a brand's or player's tonal philosophy thing than anything that's deigned to protect a vented box from unloading. And being subjective as it is, some people will approve of some choices while others will dissaprove. Or better yet, some will find those choices suitable for some gigs and not appropriate for others.*

But pretty much anyone can agree, regardless of tonal preferences and what works well for them in a specific room, that they'd like to have better driver protection that doesn't make them gut the low end unless that's what they want, that provides an extra margin of safety, and clarity.

I should underline that CLARITY bit, because you can have quite extended bass that works well in a lot of types of mixes if you don't have all that extra non-useful energy below the box tuning also pushing the cone around.

I really must check out the GenzBenz units that have a selection for their HPF characteristics.



* Which is why some people are looking at other options like channel strips and mic/inst racks.

+1. Not sure about the Genz thing... that 'bass' button sounds like a regular old bass boost to me, and IMO too extreme for use in most cases (like most of those 'on/off' boost sort of things). All the HPF talk came much later as quite a few were noting how thin the low end of the Shuttle 6 was... and all of a sudden, the 'bass boost (I think centered or maybe shelving at 50hz if I remember from the manual) became some kind of exotic HPF filter

 

[greenboy]

+1. Not sure about the Genz thing... that 'bass' button sounds like a regular old bass boost to me, and IMO too extreme for use in most cases (like most of those 'on/off' boost sort of things). All the HPF talk came much later as quite a few were noting how thin the low end of the Shuttle 6 was... and all of a sudden, the 'bass boost (I think centered or maybe shelving at 50hz if I remember from the manual) became some kind of exotic HPF filter

Ah ; }

I've had a fair number of pro pieces like EQs and such that provided a switchable HPF like OFF|40Hz|60Hz but they left the actual EQing up to the operator.

 

[KJung]

Ah ; }

I've had a fair number of pro pieces like EQs and such that provided a switchable HPF like OFF|40Hz|60Hz but they left the actual EQing up to the operator.

The manual says it is a 'low frequency peaking gain' 37 to 68hz...

 

[greenboy]

Here's that graph I talked about a few posts ago, but it was from jnewmark's Timbre control on Thunderfunk thread.

A little hard to tell, but the Navy Blue FLAT line seems to be falling off at about a 3rd order slope starting somewhere around 40 Hz, without making any assumptions about useful bass content above that frequency. That's actually a pretty good assumption for some mid-sized or up enclosures.

 

[KJung]

Here's that graph I talked about a few posts ago, but it was from jnewmark's Timbre control on Thunderfunk thread.

A little hard to tell, but the Navy Blue FLAT line seems to be falling off at about a 3rd order slope starting somewhere around 40 Hz, without making any assumptions about useful bass content above that frequency. That's actually a pretty good assumption for some mid-sized or up enclosures.

+1 I gigged that head for a couple of years, and the low end was nice and tight. The Markbass stuff has a slightly fuller, deeper low end, so I assume it rolls off just a touch lower, or possibly not as steeply, but still very nicely voiced for most 'typical' production bass cabs.

My TecAmp Puma on the other hand, seems to want to put that 3012LF right through the grill, even at low volumes! I assume that is pumping out some stuff WAY down low

 

[Son of Bovril]

The XLS Drivecore amps have a sweepable HPF but it only goes down to 50Hz which I find to be too high for my tastes, 40 or 30Hz would suit my needs better and not influence my tone too audibly

 

[greenboy]

The XLS Drivecore amps have a sweepable HPF but it only goes down to 50Hz which I find to be too high for my tastes, 40 or 30Hz would suit my needs better and not influence my tone too audibly

50 hz would suit a lot of 210 or 410 cabs, but defintely a bad choice to stop there for a lot of other cabs. What's the topology/slope on that?

 

[Son of Bovril]

50 hz would suit a lot of 210 or 410 cabs, but defintely a bad choice to stop there for a lot of other cabs. What's the topology/slope on that?

dunno, the crown manual for this model is seriously lacking when it comes to in-depth info

It sounds pretty steep to my ear and it is probably a variation of the cross-over system they use for the biamping function

 

[greenboy]

+1 I gigged that head for a couple of years, and the low end was nice and tight. The Markbass stuff has a slightly fuller, deeper low end, so I assume it rolls off just a touch lower, or possibly not as steeply, but still very nicely voiced for most 'typical' production bass cabs.

As I recall the LittleMark graphs I saw didn't indicate much rolloff, not a lot of prevoicing, no intentional audio HPF. Fairly flat.

My TecAmp Puma on the other hand, seems to want to put that 3012LF right through the grill, even at low volumes! I assume that is pumping out some stuff WAY down low

That sounds like a lot of default voicing before EQ even gets touched, either some big boosting at some bass frequency, or some big cutting elsewhere which can be practically the same thing, depending on choices. Look at that yellow line in the graph. Imagine if it didn't also drop off rapidly below that huge 40 Hz peak. That would be what a lot of people face when they do bass boosting.

 

[KJung]

As I recall the LittleMark graphs I saw didn't indicate much rolloff, not a lot of prevoicing, no intentional audio HPF. Fairly flat.



That sounds like a lot of default voicing before EQ even gets touched, either some big boosting at some bass frequency, or some big cutting elsewhere which can be practically the same thing, depending on choices.

I think Bowlus and the gang found the LMII pretty 'flat' down to around 40hz, so not that much difference from the TF. Sounded to me like just a more gentle roll-off than the TF, but I'm only able to use my ears.. not sure at all what is happening down low). The low end definitely 'behaves' nicely (i.e., sounds full, but the drivers aren't pistoning like crazy).

The Puma doesn't sound 'boosted' at all down there... sounds quite even to me. However, it does seem to (just guessing) roll off much, much deeper than the TF or LM... maybe 30hz. They do have a shelving bass control with a shelving start point of 30hz, and that does a pretty good job of reducing that wild speaker pistoning without really changing the actual nature of the low end that much with most cabs.

 

[greenboy]

I play my stuff without HPF engaged sometimes at loud home levels. Really doesn't sound any different than when the HPF is engaged. That's the beauty of a true HPF. It stays out of the way of content and tonal choices. It just provides protection and at higher levels maintains clarity.

 

[KJung]

I play my stuff without HPF engaged sometimes at loud home levels. Really doesn't sound any different than when the HPF is engaged. That's the beauty of a true HPF. It stays out of the way of content and tonal choices. It just provides protection and at higher levels maintains clarity.

+1... that 30hz shelving on the Puma is kind of a 'poor man's HPF' I guess. Back in the day, I had a Rane parametric EQ that could switch the lowest parametric band to a variable hi pass. That saved me with the original SWR SM400, which extended so far down into the sub harmonics or whatever to be almost useless. Roll off at 30 hz or so, and it sounded exactly the same, but your were able to turn up much more without the drivers coming out of the front of the box!!!!