Flat Response

[Deward Hastings]

Re: Flat Responce

We were speaking specifically of the Behringer 2-way with the WG loaded tweeter. At lease, I was.

The OP opened the thread with "I would like your opinions on actual vs. perceived flat frequency response. Some say a flat response sounds to forward or even harsh . . ."

Which it does. A flat on-axis response combined with a flat power response will sound too forward, even harsh. This is the problem that SL encountered with the addition of a rear tweeter to ORION (one of the problems, anyway).

There can also be issues at the MT crossover because of the (sometimes) different polar patterns of the M and T drivers (especially if the M driver is too large) . . . that's a (mostly) different issue, which is more room dependent than the tweeter's off-axis droop.

[Guest]

Re: Flat Responce

The OP opened the thread with "I would like your opinions on actual vs. perceived flat frequency response. Some say a flat response sounds to forward or even harsh . . ."

Which it does.

Because you said so?
Deward's subjective opinion is an unerring reflection of physical reality?
Or do you have scientifically verifiable/repeatble data to support this claim?
Can we see it now?

A flat on-axis response combined with a flat power response will sound too forward, even harsh.

How many speakers in the marketplace meet that criteria? All in the OP's experience?

This is the problem that SL encountered with the addition of a rear tweeter to ORION (one of the problems, anyway).

So a case specific application morphs into a generalization?

There can also be issues at the MT crossover because of the (sometimes) different polar patterns of the M and T drivers (especially if the M driver is too large) . . . that's a (mostly) different issue, which is more room dependent than the tweeter's off-axis droop.

No that is the issue, that most are oblivious to, when they "fix" the on axis, the only one they are aware of.

[Deward Hastings]

Re: Flat Responce

Deward's subjective opinion is an unerring reflection of physical reality?

Not *absolutely* unerring, perhaps, but obviously far better than yours . . .

[Zilch]

Re: Flat Response

In relating the desirability of flat axial response to directivity, that must also be known in order to ascertain what might be appropriate?

Here we go, then, black lines are -6dB in these maps as measured by Geddes. Minor isos delineate 6dB increments, with green encompassing -12 through -24dB, and cyan, -24 through -30dB. Black is -36dB.

Geddes Nathan:




Behringer Monitor:




Linkwitz Orion:




Orion Rear:




8" Cone/Dome 2-Way:




Typical 8" 2-Way #2:

[Zilch]

Re: Flat Response

A flat on-axis response combined with a flat power response will sound too forward, even harsh. This is the problem that SL encountered with the addition of a rear tweeter to ORION (one of the problems, anyway).

Fortunately, there are very few loudspeakers with flat power response; at one time it was a design objective. Now, the criterion is "uniform" power response tracking the axial's linearity.

Advocates of controlled directivity such as Linkwitz and Geddes have of late recognized that power response must also be controlled, and that, extended across the entire spectrum, constant directivity can, indeed, result in an "overly bright" presentation as a consequence of providing excessive high-frequency energy into the listening space. Thus, depending upon other factors such as beamwidth, deployment, and reflectivity/absorptivity characteristics of that space, it may be desirable to downwardly tilt the axial response in this region.

I measured the Behringer monitor's vertical polars today, but only listened to it briefly in ZilchLab, so I have little more to offer in this regard than that its axial response is indeed flat(ish) within a -10° to +20° (-6dB) forward vertical window about the midpoint between woofer and waveguide centers:



Violet and cyan are -15° and -20°, respectively....

[mzisserson]

Re: Flat Responce

Zilch,
I will say on the 8" 2-way you can tell EXACTLY where the handoff to the tweeter is!

That said, why did you use 2 examples of an 8" 2-way speaker? I have been following, but unsure why. Thanks!

[dlr]

Re: Flat Response

Now that's an interesting set of comparison measurements. The Behringer Monitor seems to be ever so slightly smoother overall than the Geddes Nathan. The relative difference in perception would be really interesting as a followup.

Makes me think that outside of the bass range, the vertical polar response might be the most influential in the difference in perceived response between them.

dlr

[dthomas]

Re: Flat Responce

I'm talking about fundamentals, here. You can boost the 'presence' of anything by making it bright. If you cut all but 800Hz+ for vocals, you'd have a shrill mess .. cut everything above, it'd still be perfectly intelligible.

Is that thing seriously claiming nearly 5000Hz? Jesus. Just because it's on the internet doesn't make it right. I haven't produced a note above 1000Hz in my life, and that was back when my falsetto worked right.

Breath noise perhaps?

My argument here is pure vocal frequency, not the combined effect of the voice, mouth, tongue, etc. - I've no doubt those sounds are high in frequency.

But the combined effect of voice, mouth, tongue etc... is vocal frequency. The human voice is not a signal generator with a pure fundamental and some level of distortion. The full spectrum generated by the voice, mouth, tongue etc... is the human voice and when you filter parts of it out you definitely reduce the intelligibility.

[auracle]

Re: Flat Responce

Zilch,
I will say on the 8" 2-way you can tell EXACTLY where the handoff to the tweeter is!

That said, why did you use 2 examples of an 8" 2-way speaker? I have been following, but unsure why. Thanks!

Basically to illustrate that if you don't account for each driver's beam width and the resulting power response at your intended crossover frequency with your intended crossover type - you wind up with large variations in off axis response. These pretty multi colored pictures say more for the designer's choice of driver, crossover type, and crossover frequency than they say about the alleged benefits of "controlled" or "constant" directivity waveguides. To put it in more simple terms, a lot of the benefit of what is perceived to be "constant directivity" comes from the use of high frequency drivers that can be effectively crossed low - not because of some miracle that Oblate Spheroid waveguides solve everyone's directivity and power response problems throughout the operating range. The frequencies of interest are essentially those from 1.2Khz to 2.5 khz - where a midwoofer is likely to be crossed to a tweeter. If one compares the Linkwitz Orion to the waveguided speakers, there's not a heck of a lot of difference in off axis performance - mainly because the Orion's Millenium tweeter doesn't need a waveguide to limit the spread of energy down low - it is robust enough to be crossed at frequencies lower than 1.5khz and still generate plenty of clean output. Furthermore, at lower frequencies, the Orion's "controlled off axis directivity" clearly surpasses that of any of the other designs - reducing off axis output dramatically as is considered desirable by its builder..

[dlr]

Re: Flat Responce

Furthermore, at lower frequencies, the Orion's "controlled off axis directivity" clearly surpasses that of any of the other designs - reducing off axis output dramatically as is considered desirable by its builder..

Clearly? No. Geddes design does what he desires since he also uses multiple subs placed in the room to control the low end. There's nothing to indicate that the Orion achieves the desire of SL any more than the Nathan response desired by Geddes. The low end is in the room mode range. I would suggest that Geddes design achieves his goals better due to his ultimate goal of the integration with subs. The Orion dipole response certainly reduces the low end influence with the room analyzed in isolation, but that does not by itself define the goal of each designer, especially since the low end response in isolation is overlooks the fact that it is a system, not just a low end producer. In that regard, the Nathan and the Behringer are both superior, at least in the supplied measured performance. None of this says anything about how they actually sound in comparison, though, so this is pretty much an academic exercise in this thread.

In addition, the vertical polar response comparison is totally lacking. Without doubt, the Orion will fall on its face in comparison simply due to the number of drivers and physical vertical separation with the crossover points used, so it's more appropriate to say that overall the Nathan achieves the goal of controlled directivity far better than the Orion could in any sense. Excluding the vertical polar response leaves out an important aspect of the analysis.

dlr

[auracle]

Re: Flat Responce

Clearly? No. Geddes design does what he desires since he also uses multiple subs placed in the room to control the low end. There's nothing to indicate that the Orion achieves the desire of SL any more than the Nathan response desired by Geddes. The low end is in the room mode range. I would suggest that Geddes design achieves his goals better due to his ultimate goal of the integration with subs. The Orion dipole response certainly reduces the low end influence with the room analyzed in isolation, but that does not by itself define the goal of each designer, especially since the low end response in isolation is overlooks the fact that it is a system, not just a low end producer. In that regard, the Nathan and the Behringer are both superior, at least in the supplied measured performance. None of this says anything about how they actually sound in comparison, though, so this is pretty much an academic exercise in this thread.

In addition, the vertical polar response comparison is totally lacking. Without doubt, the Orion will fall on its face in comparison simply due to the number of drivers and physical vertical separation with the crossover points used, so it's more appropriate to say that overall the Nathan achieves the goal of controlled directivity far better than the Orion could in any sense. Excluding the vertical polar response leaves out an important aspect of the analysis.

dlr

:D You might want to rethink just about everything you just said. In other words, talk to the graphs above. If you actually read them, you'd find that off axis response from 800 hz down to 200 hz is highly controlled by the dipole radiation pattern of the Orion - no such control exhibited by any of the other speakers.

And this statement by you above:

"The Orion dipole response certainly reduces the low end influence with the room analyzed in isolation, but that does not by itself define the goal of each designer, especially since the low end response in isolation is overlooks the fact that it is a system, not just a low end producer. In that regard, the Nathan and the Behringer are both superior, at least in the supplied measured performance."

- is so out there in left field, I'm not sure it merits a response. Reduced side wall interaction is a major goal of most dipole OB speaker designers - which Linkwitz has been and continues to be. The only speaker that exhibits directivity or directionality control at lower frequencies is the Orion. To suggest that any of the other speakers exhibit some kind of control in the directivity of energy from 200hz to 800 hz ignores the response graphs that are slapping you upside the head.

[DDF]

Re: Flat Responce

Let's reframe the question a bit and see what we get...try this:

"What is the optimum (in-room, spatially averaged) frequency response for a home music playback system where the program material will consist of commercially available recorded music from the past 50 years?"

I tried to specify how the response is to be measured and the program material that would be auditioned. These are both critical elements of any serious inquiry into the appropriate frequency response for a sound playback system.

If we were strictly doing acoustics research and were trying to accurately reproduce the sound of a live source (a voice for example) then we would use a microphone with a known flat frequency response to detect the sound and then we would reproduce it through a loudspeaker with a flat (in-room, spatially averaged) on-axis frequency response. This setup would likely provide a good reproduction of the live sound source.

John, I snipped the rest of your discussion because I believe it describes in great detail what many of us have already said in this thread. However I do want to raise some dissenting points about your ideal scenario above, since I don't believe this ideal is correct. I think the differences are important to discuss since this ideal asymptote is very much indicative of the "holy grail" in reproduction many are trying to attain, whether the goal is "they are here" or "you are there".

They are here
==========
If the voice is recorded with a flat mic in an dead room (little room sound contribution to the recording), than the playback over speakers should have the same directivity index over frequency as a human voice should, in order for it to accuratley illuminate the sound power in the room, if the goal is for the playback to sound like the person is in that room. This speaker would decidely not have a "well behaved" power response. I think this is a key point missed in most every discussion. How can a speaker with a "smooth" power response accurately replicate a voice recorded closed miced, when the human voice does not exibit the same 'smooth power response"? OTOH, how do you balance this paradox when every instrument has a different radiation pattern? What is the ideal compromise? Toole seemed to find that it was well behaved power response.

You are there
==========
OTOH, if the recording is made with a flat mic but in an acoustic space, and we want to reproduce that acoustic space in our room, then I believe the only shot at accuracy we have is to use speakers with a DI similar to the recording monitors and in an acoustic space similar to the monitors. The idea here is to put blind faith in the recording engineer and replicate his set up, as you mentioned. To augment this, we should remove as many early reflections as possible which give strong clues of the reproduction space size, in order to minimize masking the recording's space cues. We can then augment the natural recording space cues by using speakers (eg dipoles) that have a much higher proportion of longer delayed reflections vs earlier delayed reflections. early reflections more mask the recording space cues than do longer delayed reflections. Olive showed fairly conclusively that a recording natural "space" and reverb cues are augmented by some presence of natural reflections in the playback space, so getting the right proportion of these longer delayed reflections is also important.

Dave

[m.a.c.]

Re: Flat Responce

The only speaker that exhibits directivity or directionality control at lower frequencies is the Orion. To suggest that any of the other speakers exhibit some kind of control in the directivity of energy from 200hz to 800 hz ignores the response graphs that are slapping you upside the head.

You may want to completely ignore Geddes graphs that Zilch posted because the data, at least for the Orion, is completely flawed. The front and rear graphs for the Orions should look identical below 200Hz, but they are far from it. When I questioned Geddes about this he didn't have an answer why this was so.

[dlr]

Re: Flat Responce

I don't need to rethink any of it. What I said was accurate. That you think that due to the Orion directivity being as it is makes it achieve SL's target better than Geddes' target is met is simply your interpretation. You're placing SL's target as being superior, when in fact you have not addressed each individual designer's goal. You have somehow decided that the one factor is the same goal and that what is shown is the complete implementation towards their goals. That is not the case.

Furthermore, at lower frequencies, the Orion's "controlled off axis directivity" clearly surpasses that of any of the other designs - reducing off axis output dramatically as is considered desirable by its builder..

You seem to think that your interpretation of the goals is correct and that both are after the same thing. Given that Geddes goes beyond SL with the addition of low end control using multiple separate subs, your analysis of the desires is incomplete and incorrect I believe.

Feel free not to respond to anything that you feel does not merit a response. This is a debate board, but if you prefer not to engage in a genial debate as appears to be the case, that is your choice. But if that is your choice, it would better to then say nothing as nothing will be gained by your posts in that case. Nothing is "slapping (me) upside the head" other than your inconsiderate and hostile posting that is all too frequent in your posts. For some reason you feel that this enhances your position when in fact it is quite the opposite.

If you feel that this post also merits no response, please do not respond. In any case, given your proclivities I feel that your posts will likely merit no further response from me and I will not respond to any of them, unless you decide that a genial debate is in order. The choice is yours.

dlr

[dlr]

Re: Flat Responce

You may want to completely ignore Geddes graphs that Zilch posted because the data, at least for the Orion, is completely flawed. The front and rear graphs for the Orions should look identical below 200Hz, but they are far from it. When I questioned Geddes about this he didn't have an answer why this was so.

I would like to see some other measurements that can be considered more reliable. That was rather appalling. We can only go by what we see here for now. It's unfortunate that there isn't some other source to include. But given that the low end will be covered by the bass dipole, it certainly should be nearly perfectly symmetric in that range.

dlr