The Smaller Advent Loudspeaker
- Thread starter Zilch
- Start date
No, but you're set up to do that, I presume, and will present your findings for this forum's perusal, along with YOUR measurements of Smaller Advents for comparison?
It's a -6 dB hole at 2 kHz, and a -20 dB notch without the grille, even with 1/6 octave smoothing. Not the mic, I guarantee.
There IS a valid thesis, not unrelated to your original observation, and, notwithstanding the fact that these are no longer on the test stand, I'll check it out.
Edit: See below.... :yes:
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For curiosity's sake -- just how many other people on AK have you asked for calibration verification on their gear?
John
For anyone doing a scientific investigation into acoustics the test setup must be calibrated and any irregularities must be nulled. As you can see there are significant differences in results based on test mike polarization. At best you can see the Smaller Advent is pretty darn flat across the whole freqency range.
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May we see YOUR results on The Smaller Advent for comparison here, please?
You suggest that my measurements are inherently inaccurate, yet they reliably indicate that the Smaller Advent is "pretty darn flat?" Not hardly, with those prominent peaks at 1 kHz and 13.5 kHz, also previously found by others, and the hole at 2.kHz punctuating them, these response anomalies are quite audible.
I have no clue what "test mic polarization" is; you apparently have a recognizable agenda here. If you asked the appropriate questions, I would be pleased to answer them, but thus far, you're not getting it, alas....
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marantzfan
...
Lumpy is a good name for a troll... 
If it is caused by the crossover and is dependent on microphone position then it is not a measurement artifact, it is part of the speaker's polar pattern.
That is a moot point. Zilch is measuring using MLS which is a gated signal and using a mic pointed directly at the speaker. The only signal presented in the charts are direct signal from the speaker so the polar pattern of the mic is irrelavant. If he were trying to measure the diffuse sound field at a certain point in the room then the polar response of the mic would come into question.
What the heck does that mean? If you're still talking about the mic's polar pattern then, as stated above, it doesn't really matter as long as it is good on axis. Callibration is important, but if it's reasonably flat then you'll get reasonable results.
Didn't you just try to point out how the mic was skewing the results? If you stand by that reasoning then you can't draw any conclusions from these graphs as they are incorrect.
What I see is +/-4dB or so. I wouldn't call that pretty darn flat.
Ray
Actually +- 4db is excellent for a speaker. Especially one that has bass response into the 30 hz range and is so small. It is very flat. The polar pattern of the microphone is significant at the crossover point because the radiator is not a point source at that frequency. The correct way to measure is to measure the individual drivers and splice their curves together.
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Lump ON!
Please study up Dickason and D'Appolito regarding how to measure loudspeakers.
You apparently did not play the AudioMojo game -- all of the contestants measure better than these Smaller Advents.
See also Original Large Advents here:
http://www.audiokarma.org/forums/showthread.php?p=2963942#post2963942
Yeah, well, AR used that practice during their "Vintage" years and abandoned it soon thereafter, along with their reverberant chamber; it is so patently deceptive that no manufacturer or scientist does it, since it ignores the interaction of the drivers in the system.
Please study up Dickason and D'Appolito regarding how to measure loudspeakers.
You apparently did not play the AudioMojo game -- all of the contestants measure better than these Smaller Advents.
See also Original Large Advents here:
http://www.audiokarma.org/forums/showthread.php?p=2963942#post2963942
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The Indignia, designed here on AK, measures out at +/-1.75dB.
Doesn't matter. The wavefront coming from the driver is still going to be coming at the mic on axis. Whether it's a line source (cyllindrical wavefront), large panel (planar wave front) or a point source (spherical wavefront) has no bearing as long as the mic is pointed at the source. At 1m with a smallish 2-way you're looking at a couple of degrees between the axes of the drivers. Once again, as long as the mic has good on axis response, the polar doesn't really matter.
That takes the cabinet and crossover out of the equation. Do you listen to your speakers without the cabinet and crossover?
Yeah, but none of the Mojo test speakers were designed 35 years ago... when there was NO computer test apparatus in existence of the sort that was used to measure the units in that test. Not even to the big boy companies.
And I would say- there's really no way you could say the Unity fullrange speaker in the Mojo test measured as well as the Smaller Advent. That giant hump in the response trumps all the faults in the Advent response.
Also, the Gini speaker really isn't any better, in overall response, from what I see, than the Advent...
I would say that for the price, and the time, that the Smaller Advents were pretty remarkably evenly voiced... probably at least as good as any other small speaker of the day. Other than the mild midrange hump, there's really nothing to annoy, and the speaker is just plain well-balanced through the spectrum...
Regards,
Gordon.
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The response difference is negligible. Overall power response is also a big part of the sound. I doubt a directional waveguide could match the original sound and reproduce the concert hall balance of the original. The woofer and cabinet are a system and are traditionally measured together. The tweeter is measured separately because interference effects between the cabinet and driver invalidates the measurements. They have no audible consequences
Yes, but the HF driver WILL BE PERMANENTLY MOUNTED in the cabinet. To measure one without the other is a fools errand, IME. And I've measured a lot of them...
How do you know if diffraction interference effects from the cabinet on the HF drivers can be ameliorated by slight changes in baffle positioning or not? Sometimes, you can get 3-4 dB differences in the peaks and dips in the response, just by moving the tweeter around an inch or so sideways on the baffle. Seen it happen lots of times...
Regards,
Gordon.
Where are you getting all of this "traditional" information? Everyone I know who measures speakers uses a far field measurement of the enclosure, crossover, and all drivers from the high limit (most use 20kHz) down to the frequency where the signal is no longer valid because:
a) the MLS signal reaches it's low limit
b) a gated sine sweep reaches the frequency where the first reflections enter the gate and corrupt the direct sound
c) an anechoic chamber ceases to be anechoic
From that point down a near field woofer measurement is taken and spliced with the far field. If a ported or PR system then the port or PR is measured near field and added to the woofer response and then spliced.
This is pretty much standard practice in the industry.
edit: Gordon types faster than me. Good comments on tweeters and cabs!
a) the MLS signal reaches it's low limit
b) a gated sine sweep reaches the frequency where the first reflections enter the gate and corrupt the direct sound
c) an anechoic chamber ceases to be anechoic
From that point down a near field woofer measurement is taken and spliced with the far field. If a ported or PR system then the port or PR is measured near field and added to the woofer response and then spliced.
This is pretty much standard practice in the industry.
edit: Gordon types faster than me. Good comments on tweeters and cabs!
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I don't doubt that diffraction effects can be minimized and that perhaps it is worthwhile if there are no other costs. I just doubt that they can be heard. I think they become even less signficant when you are further away from the system as they are averaged out in the reverberant field.
