The Audioholics review of the Polk Audio T15 speakers has a upper dB limit of 95 dB for the vertical and horizontal polar plots. However, the Audio Science review of the Polk Audio T15 speakers has an upper dB limit of 68 dB for the vertical axis polar plot and 66 dB for the horizontal polar plot. The same is true for the Audio Science review of the JBL Stage A130 speakers where the upper dB limit on both vertical and horizontal polar plots is only 62 dB. Based on this, I wouldn't put much faith in any speaker review from Audio Science since their measurement results seem very suspicious.
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Polk Audio T15 review
- Thread starter YesI'maEE
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>[...] their measurement results seem very suspicious.
You ok, hun?
You ok, hun?
I don't know if it's an issue or not on that chart, but ASR is pretty consistent on that range for the polar plots.
Ex:
I believe what OP is alarmed about is that the Audioholic scale for polar plots is different. For example, from Audioholics:
Is the difference meaningful? Here's the Audioholics and ASR polar for the T15 side by side:
"Polar map of Polk T15 horizontal response at 20 degree angle below tweeter +/- 90 degrees"
ASR:
Note that the ASR graph is much wider. You would need to zoom in as well. Both charts show a big drop after the hotspot. Both reviews note the issue around 4Khz. It also sounds like ASR's is taken on tweeter axis, where AH is 20 degrees below tweeter axis. Given that the common placement advice I read is "place the speakers with tweeter about ear level", I can't immediately say ASR is wrong. What's it supposed to be? Is there a standard?
Ex:
I believe what OP is alarmed about is that the Audioholic scale for polar plots is different. For example, from Audioholics:
Is the difference meaningful? Here's the Audioholics and ASR polar for the T15 side by side:
"Polar map of Polk T15 horizontal response at 20 degree angle below tweeter +/- 90 degrees"
ASR:
Note that the ASR graph is much wider. You would need to zoom in as well. Both charts show a big drop after the hotspot. Both reviews note the issue around 4Khz. It also sounds like ASR's is taken on tweeter axis, where AH is 20 degrees below tweeter axis. Given that the common placement advice I read is "place the speakers with tweeter about ear level", I can't immediately say ASR is wrong. What's it supposed to be? Is there a standard?
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- Thread Starter
- #5
Audioholics recommends that the T15 be located +20 degrees or - 20 degrees vertically with respect to the listener's ear. They are designed to be off axis speakers and make perfect surround speakers. By the way, I happen to own a pair of T15s and they are the best bookshelf speakers I've ever heard for $69/pair. The sloppy speaker reviews from Audio Science should be considered Poor Science and cannot be trusted.
Thanks for sharing your opinion, and I'm glad you are enjoying the speakers. Where is the testing standard stating that polar measurements should be taken at +20 or -20 degrees vertically from the tweeter, instead of 0 degrees? Does it also specify SPL for testing levels?
Your posts come off as trolling as opposed to a good faith attempt to engage in dialogue over testing methods. Is it your intent to troll and bait or to engage in honest discussion?
- Thread Starter
- #7
I'm simply stating the facts about the Polk Audio T15. The Audioholics T15 review is spot on. Audio Science didn't even bother to contact Polk about the off axis design intent of the T15. If the Audio Science review used the same dB scale on their polar plots as Audioholics, then we wouldn't be having this discussion.
- Thread Starter
- #9
I am a retired Sr. Electronics Engineer and also own a Polk Audio PSW10 subwoofer.
I suspect there are no standards for audio polar plot dB scales, but it's hard to compare apples to apples when the T15 Audio Science review polar plots don't even approach 90 dB, particularly when the T15 speaker sensitivity is rated at 89 dB.
I suspect there are no standards for audio polar plot dB scales, but it's hard to compare apples to apples when the T15 Audio Science review polar plots don't even approach 90 dB, particularly when the T15 speaker sensitivity is rated at 89 dB.
Distance is set at 10m in the ASR plots vs 1m in the Audioholics plots.
It would be equally fair to say that if the Audioholics team used the same scale and methodology as ASR, we wouldn't be having this discussion.
This doesn't matter, as the polar is made to show you relative levels at various angles. The polar plot will look the exact same as long as the color grading and total dB amount from highest to lowest level (in the case of ASR, 30dB) stays the same. Audioholics graph has the lowest level 35dB below the highest, and finer steps (I think 0.5dB compared to Amir's 1dB). I could measure this loudspeaker at 100dB if I wanted, and then normalize the graph to show 0 to -30dB and the result would be the same.
If your complaints about the measurement axis are correct, then you're right that these graphs aren't comparable, but it has nothing to do with the scaling. As long as the data in the graph is good, it can be exported and rescaled as necessary.
Have you considered adding your comments directly to the existing review thread? Note that the original review measurements do show there is better performance at +/- 20 degrees, and others in the review mention the intended use. The protocol here has been on axis for measurements for consistency.
I find the measurements and process here useful. Good luck to you and please continue to enjoy your speakers.
I find the measurements and process here useful. Good luck to you and please continue to enjoy your speakers.
- Thread Starter
- #17
Typically, 10m is one of the distances used to measure EMI (ElectroMagnetic Interference) inside a shielded anechoic chamber. But a 10m distance doesn't make any sense to measure a speaker's frequency vs amplitude response.
Freeway
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"These have also been measured by Audio Science review. They do measure a bit below what I have. Not too surprising that our measurements differ. In very low-budget speakers like these, there tends to be less manufacturing consistency from unit to unit."
Shady J - Staff Member Audioholics
Shady J - Staff Member Audioholics
Disregard the distance. It's arbitrary, the directivity behavior is going to be the same as soon as you're distant enough from the speaker for the drivers to integrate. As for the directivity polar plots, note two things:
1. ASR is measured on tweeter axis and is not normalized to on-axis response.
2. Audioholics notes the exact same problem with regard to on-axis response. The design choice that they respond best 20 degrees vertically off axis is an odd one indeed, and doesn't really make that much sense all things considered.
Unfortunately, this does not mean much of anything with regards to your understanding of speakers. I mean no disrespect, but this would be like me going up to you and saying "I'm an audio engineer therefore I know your board design is bad".
I suggest you read up on how the NFS system works, because it most certainly isn't measuring at 10m distant.
Facepalm time.
You also compare NFS measurements with DIY outdoor measurements. As far as I can tell, Klippel NFS is more accurate/reliable all day.
Anyway, I see no point for this thread since there's nothing more obvious than what you're doing here: trolling.
Why are you doing it, then?
You also compare NFS measurements with DIY outdoor measurements. As far as I can tell, Klippel NFS is more accurate/reliable all day.
Anyway, I see no point for this thread since there's nothing more obvious than what you're doing here: trolling.
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