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Double Bass "It practically prevents upright feedback"

#42
drurb said:
Tom, I understand but, as you undoubtedly know, when you use a parametric tone-shaping circuit or other type to fight feedback, you usually are attenuating the output of the cabinet within a narrow range of frequencies. Those frequencies are the ones that are excited by the interaction of the cabinet and the particular resonances of the room it is in. The particular frequencies will, of course, change from room to room. Now, for argument's sake, if one noticed that the problems often occur within certain narrow bands of the spectrum, one could attempt to build a cabinet that had nulls in the response within those bands. That would seem a very foolish thing to do. It would certainly affect the desired characteristics of the cabinet.

On the other hand, one would want to avoid cabinets with strong resonances that would show up as peaks in their frequency response. Those would likely be more susceptible to feedback than others with a flatter response.

In summary, I'd say that looking at frequency-response curves might give you insight into which cabs would be atypically susceptible to feedback. In the absence of wild frequency-response anomalies, however, I don't think the curves will do you much good.
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Gotcha. I am probably in agreement with you, but, going on the theory that usable volume with some slices of the tonal pie missing is more desirable than no usable volume (due to feedback), frequency response is a least worth considering (and possibly what Jorg is getting at with his cabinet design).

That being said, I am with you in that I would call cutting frequency response a means of last resort. It is much more desirable to control your feedback via other methods.
 
#43
tombowlus said:
Gotcha. I am probably in agreement with you, but, going on the theory that usable volume with some slices of the tonal pie missing is more desirable than no usable volume (due to feedback), frequency response is a least worth considering (and possibly what Jorg is getting at with his cabinet design).

That being said, I am with you in that I would call cutting frequency response a means of last resort. It is much more desirable to control your feedback via other methods.
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Yup, we are in agreement (as usual). I'd still prefer a reasonably flat cab and if I have to produce a notch in the response to cut feedback, I'd rather do it via the electronics than have it "built-in" the the response of the cab.
 
#44
I've used fully parametric eq's for 30 years. Once you get used to them you know what to notch. For instance, on my bass with a Full Circle, the D and Eflat are always a bit louder than the rest of my bass. I know now what frequency and "Q" and how much to attenuate. The result is a much more balanced sound. All gain, no loss. The Fishman Dual Parametric direct box is a fabulous piece. I have one and couldn't live without it. Too bad they stopped making it. I also have a 5 band Symetrix parametric eq. The 2 bands on the Fishman usually offer enough help, though.
I've heard that the Schroeder cabinets sound nice, and I believe it. To my knowledge, they are still ordinary cabs (either reflex or sealed box) that use ordinary drivers. This is not a criticism. Almost all cabs don't use exotic drivers or cabinet configurations. If they are well engineered they sound good. It's just that a goofy claim like the feedback one casts a (probably good sounding ) cabinet in a negative light, at least for me.
 
#45
I suspect that directionality is not the answer, as a speaker is likely to be omnidirectional below a few hundred Hz. Thus, performance is still going to be governed by the five parameters that I mentioned. At first glance, adding a custom notch with passive components would seem likely to be expensive, heavy, and unlikely. I am open minded about Schroeder's design, but I am just explaining why I have some preconceptions about the possibilities.

For some time I have considered studying bass feedback in more depth. One idea of mine is to measure the acoustical gain of the bass by running it backwards -- feed a signal generator into a speaker close to the bass and measure the output of the pickup at different frequencies. Maybe others have tried this already. This might make it easy to identify the specific problem areas of any given bass. The test could then be run with various common treatments, such as afterlength damping, to quantify what is going on. One could go crazy and try different placement and acoustical conditions as well.

This assumes I am suddenly presented with a huge block of time when nobody is in the house to be bothered by the noise. :D
 
#46
Being an old audio guy and just naturally curious, I called Jorg Schroeder. He's a very nice fellow and was kind enough to spare some of his time to talk with me and answer some questions about the Mini 12+. What I got out of the conversation is Jorg has worked closely with his designer and double bass players to balance the various parameters for the woofer (which is custom manufactured by Celestion for Schroeder) and the cabinet so as to minimize feedback problems. He seemed quite sincere about this. Although I am usually skeptical about claims such as the one that started this thread, I'm interested enough that I would like to hear a Schroeder Mini 12+ for myself.
 
#48
robgrow said:
Being an old audio guy and just naturally curious, I called Jorg Schroeder. He's a very nice fellow and was kind enough to spare some of his time to talk with me and answer some questions about the Mini 12+. What I got out of the conversation is Jorg has worked closely with his designer and double bass players to balance the various parameters for the woofer (which is custom manufactured by Celestion for Schroeder) and the cabinet so as to minimize feedback problems. He seemed quite sincere about this. Although I am usually skeptical about claims such as the one that started this thread, I'm interested enough that I would like to hear a Schroeder Mini 12+ for myself.
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Let me see if I have this right. He minimizes the feedback via a design that balances various parameters of the woofer and cabinet in order to reduce feedback. Well, that clears that up! :)

I gather he wasn't very forthcoming.
 
#49
Well, I just played the first gig (quartet) with my new Mini12+L. I can't really comment on the feedback thing because I don't play too loud and rarely have those concerns anyway. However, the box sounds excellent. There is alot of nice punchy midrange coming out of it without any hard edges (i.e. boxiness). My lowest notes were very clear and tight without sounding choked or compressed. The high end wasn't nasty or gnarly at all, which is always a worrisome possibility when you see a nice shiny tweeter.

Again, I dunno nothing about the feedback preventing powers of the cab but I just assume it has something to do with the lack of low-low freqs coming out of the box. I quite liked it.

W

Edit: Here's me with the cab, feel free to make fun of my upper octave dots...:)

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#51
fdeck said:
...For some time I have considered studying bass feedback in more depth. One idea of mine is to measure the acoustical gain of the bass by running it backwards -- feed a signal generator into a speaker close to the bass and measure the output of the pickup at different frequencies. Maybe others have tried this already. This might make it easy to identify the specific problem areas of any given bass. The test could then be run with various common treatments, such as afterlength damping, to quantify what is going on. One could go crazy and try different placement and acoustical conditions as well.

This assumes I am suddenly presented with a huge block of time when nobody is in the house to be bothered by the noise. :D
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This is similar to the way they treat acoustic instruments in the 'vibrelax' technique (see [Invalid or Expired Link Removed]) , only it is not aimed towards feedback, only towards more even response and improved resonance.
 
#54
fdeck said:
Well, on my old Kay... :hmm:

But I would not mind knowing what frequencies feed back on various basses.
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You know, I thought more about this and I think you're right about where the feedback might be. Still, I don't think the cabs are quite as omnidirectional as you might assume in the critical spectral regions. For example, it's been my experience that sometimes feedback can be relieved by adjusting the position of the bass or cab within a foot or so. In any case, I'm still not buying the hype.
 
#59
drurb said:
You know, I thought more about this and I think you're right about where the feedback might be. Still, I don't think the cabs are quite as omnidirectional as you might assume in the critical spectral regions. For example, it's been my experience that sometimes feedback can be relieved by adjusting the position of the bass or cab within a foot or so. In any case, I'm still not buying the hype.
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Interesting. I am not an acoustics guy, but I wonder if the bass ends up in a node or antinode of a room resonance depending on where the speaker is placed. A quarter wavelength at 120 Hz, where my Kay gets squirrely, is somewhere around a couple feet.
 
#60
fdeck said:
Interesting. I am not an acoustics guy, but I wonder if the bass ends up in a node or antinode of a room resonance depending on where the speaker is placed. A quarter wavelength at 120 Hz, where my Kay gets squirrely, is somewhere around a couple feet.
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Yup, that could very well contribute!
 

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