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Multiple sized drivers in same cab....good or bad?

#22
DigitalMan said:
Sound travels at the same speed and in straight lines. You may have volume differences based on radial patterns, but you will have zero synchronization differences other than what is caused simply by having two points of origin - and both problems apply to any two speakers, not just speakers with different phase response patterns.

The horizon for experiencing differences in phase will be a maximum of the spacing between the two speakers.
Click to expand...

Multiple drivers in a cab are multiple points of origin.
 
#26
DigitalMan said:
BTW - while I'm downloading a java update and switching over from Chrome to Safari, can you recommend a particular setting that demonstrates the effect we're discussing?
Click to expand...

You can move the sources, but these should work. The arcing grey areas are points of deconstructive interference, where the sound (amplitude of the wave) is falling out. Depending on frequency of the sources, and their spacial alignment, these areas can be stationary, or in the settings I have, not.

Phase.JPG
 
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#28
I've played with the app and it's very cool. Fwiw I've been trying to prove your point in doing so, not my own.

For the first example I can see that two sources playing different frequencies interact differently throughout the room. But you'd agree that different frequency and different phase response are two entirely different things. This example hints at the complex interaction of two sources playing full range sound but does not speak to phase response. If you take this example and remove the positional difference the pattern becomes completely uniform. As the tool rightly points out, you can have two different frequencies or two different phases, but not both. There is no such thing as two dissimilar frequencies being in phase or out of phase with each other - we know they will oscillate unless they are harmonics of one another.

For the second example with phase difference invoked, the information at every point in the room seems identical to me except in the 10 lines of destruction that radiate out about the same width as the speaker difference. Those lines are the same when in phase or out of phase and they don't move over time at all. To verify, watch what happens when you drop the sources very close together. If you eliminate the positional difference (or close to it) the destructive interference disappears altogether. If you move them a little further apart but crank the phase up to max, you will see the distinct lines of cancellation - but they still don't move at all.

Please check out my alternatives with the tool and try to humor me a bit to understand where I'm coming from.

We agree that multiple sound sources and multiple frequencies create complex interaction (example 1). I think this reinforces the line array notion which was never in dispute because the line array create the most equal possible distance to the listening plane (although the line array would have the opposite effect if people were standing on the wall, but I digress).

We saw that different frequencies interacting caused information patterns to move around the room.

We agree that different phase responses create patterns of constructive and destructive interference - no doubt about it. I'm simply saying that I am not seeing any evidence that phase response causes interference patterns that move about the listening space. In the tool, the interference patterns for different phase seem completely static.

I'm not trying to be a jerk or stubborn, and I do greatly appreciate the civil discourse.
 
#29
You cant move the sources so very close to each other. That is a point source. It is impossible to get drivers center to center close enough for them to act that way. Additionally, yes with this applet you cant vary phase and frequency. That is ok. If you could do that, you would be demonstrating more of a bi-amp system. When running drivers in parallel full range, you are sending them the same signal, and if their response differs (slightly out of phase) you see what the demo shows. Similarly, you could send slightly out of phase signals to identical drivers, and get similar results.
 
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#30
CL400Peavey said:
You cant move the sources so very close to each other. That is a point source. It is impossible to get drivers center to center close enough for them to act that way. Additionally, yes with this applet you cant vary phase and frequency. That is ok. If you could do that, you would be demonstrating more of a bi-amp system. When running drivers in parallel full range, you are sending them the same signal, and if their response differs (slightly out of phase) you see what the demo shows. Similarly, you could send slightly out of phase signals to identical drivers, and get similar results.
Click to expand...
The problem is that it is a model of a two dimensional plane. You could stack drivers vertically with one being six inches above ear level and the other being six inches below.

All I am saying is that the interference patterns associated with multiple points are significant and they don't change materially when you introduce phase response deltas. The pattern of information in the room is fixed. Some listening points are optimal and some are not as shown by the destructive interference.

When the sources are spaced normally there is no substantive difference nor should there be when one source is out of phase versus when they are both in phase. That is precisely and exclusively the point I'm trying to make. That the listening position problem has no business being attached solely to the mixed driver discussion as it applies equally to any two drivers in similar relative position. It's an extremely narrow point, but it's all I've been trying to say. Just redo the second pic with both drivers in phase and you will see that the picture doesn't materially change.
 
#31
For the record I'm leaving the conversation as it stands, largely because I'm about to leave my hotel to catch a plane, but also because I've said my piece. I feel neither frustrated nor victorious - just enjoying the positive intentions and competition of ideas.

I truly appreciate the sharing of insights. The app was really cool.

Respectfully,
 
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#34
allenhumble said:
You guys are much smarter than me.
Click to expand...

Me too. That is, I'm also a non-techie, but over the past decade-plus I've been trying to learn as much as I can from these guys. To throw in my non-technical 2¢:

Glancing at the page of the TecAmp 10/12 cab, I'm reminded of the original Schroeder cabs with the angled baffles (if you're not aware, those cabs were designed to cram more speakers into a particular box size). The selling point: "I'm not some armchair expert, I'm a real-world working bassist who knows what he wants from his gear". Audio engineers (correctly) attacked the original Schroeder designs as having weak bass response and exaggerated midrange, however they became fairly popular cabs. Why? On the one hand, there are always fads that come and go due to effective marketing hype. On the other hand, sometimes wrong is right. Meaning, it's perfectly okay to prefer a cab that is flawed from an audio engineering standpoint. Best example is the classic Ampeg 8x10 cab (I use a similar 6x10). I know that the parallel tens cause some destructive interference out in the audience, but it sounds great to me onstage, and I often get FOH support so the interference is not much of a factor. I also love the enhanced midrange punch, and the relative lack of high end from not having a tweeter sounds especially great with overdrive/distortion. I also believe that the slightly attenuated bass response down low can be a big advantage when playing live: less onstage rumble, better note definition, less bleeding into the kick drum mic, etc.

Note that I am NOT encouraging anyone to dismiss the audio experts: to the contrary, learn as much as you can so that you can make an informed decision. However there's a minority of experts who venture into "audiophile" territory, and claim that the only way anyone should build a bass rig is to use the flattest, mnost perfectly designed components possible. That's just ivory tower purism-for-its-own-sake -- might as well claim that 98% of the bass tones you've ever heard are no good because they aren't perfectly clean and flat. Note: "flat-is-where-it's-at" is a valid way of assembling a bass rig, but it's just one of many ways. Most of my rigs can do clean-and-flat well enough, but I'd be utterly bored if that's all they did. I prefer variety such as adding overdrive and tone coloration. Even if I'm using the same technique to play the same bass line with the same bass, sometimes I feel like a modern tone, sometimes I feel like a vintage tone, sometimes I feel like trying something different.

Sorry to be long-winded. To sum up: yes, the Tecamp (same as many other bass cabs) is flawed from an engineering standpoint, and I agree with the engineers that you should be skeptical, but the bottom line is that if you like it then you like it and there's nothing wrong with that.
 
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#36
I think cl400peavey and digitalman, in some respects anyway, might be explaining similar things in different ways.

Imagine a rifle shot. You move the barrel one inch to the right and the bullet lands several feet to the right of the target out at distance. A baseball hits a different portion of the bat by only a tiny amount and ends up going in a wildly different direction. As the sound spreads out from speakers, the areas of constructive and destructive interference also become greater out at distance, to the point you can walk back and forth and hear the differing response in different listening positions that you can't hear as well up close.

That stuff is pretty easy to hear when you're playing outdoors. You can walk back and forth out in the audience and hear null zones, high frequency dispersion dropoff, etc.

When you put the speakers in a room, you don't have to get very far away from them before you start hearing more and more reflected room sound and less and less direct sound straight from speaker to ear.

The distance is so short you can show this to yourself in your living room. Sit directly in front of a speaker, very close to it, and hold a pillow in front of your face. You will hear the highend become subdued as it is damped by the pillow. Next sit only a few feet away, not even all the way to the couch on the other side of the room and hold the pillow up again. You'll still hear the highs as you are hearing them reflected and not straight from the source. You'll find that in most any room, you have to be pretty much right up on the speaker in order to hear a vast majority of direct sound.

This is why our tone never sounds the same out in the room as it does up on stage right in front of your cab.
 
#37
All I know for sure is:
The ISP Bass Vector 1-15" and 2-8" drivers, sounds freaking phenomenal, far away, up close, everywhere. At 2 grand it's a little pricey-but damn this thing sounds good-regardless of rocket science.
 

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