Sunday, 7 June 2015

MEASUREMENTS: The Effect of Speaker Grills...

"Clothed" or "Naked"... What's the difference?

A quick measurement for this week...

I was curious the other day as I was doing some room measurements what effect speaker grills make. My Paradigm Signature S8 V3's have typical fabric and plastic grills up front. Simple question - How much difference does the grill make to the sound of the speaker?


Audiophile magazines and "serious" listeners tend to recommend removing the grills. In my experience, I have not really heard much difference over the years with my various speakers and have tended to keep them on. This has been especially true in the last 10 years with kids in the home and especially when their (untrained!) friends come over so as to avoid any disasters with sticky fingers contacting speaker cones :-).

So, here's the simple setup. I have my calibrated Behringer ECM8000 measurement microphone placed 65" in front of my speakers on axis at approximately the heigh of my mid-range driver. I made a second set of measurements with the microphone 20-degrees to the left off axis as well to see if there was a difference with and without the grills attached.

I measured the speakers with the latest awesome Room EQ Wizard v5.12. Test tone was played off the TEAC UD-501 DAC while measured with my E-MU 0404USB. The right speaker was tested.

ON AXIS:

1/12 octave smoothing, no EQ/DSP.



20-degrees laterally OFF AXIS:

1/12 octave smoothing, no EQ/DSP.



As you can see, the grills made a difference in the upper frequencies starting around 3kHz. Nothing untoward was seen with the time-domain impulse response (there's a typical floor-bounce first reflection seen slightly past 4ms).

Looking at the on axis frequency-response graph, overall, the magnitude of the difference with the grill is that it toned down the tweeter response by about 2dB from about 3.5kHz. However, there was a bump from 8.5-11.5kHz where the grill actually accentuated the frequency response up to 1dB above the measurement with the grill off. With good ears, these differences could represent an audible tonal difference and would be dependent on the music of course. For these speakers, the overall effect of the grills would be a taming of the high frequencies (probably a good thing in terms of general listener preference).

At 20-degrees off axis, the measured difference between grill on and off was actually a little smaller.

This amount of difference with grill on/off is expectedly much smaller than the difference between listening to the speaker on-axis and 20-degrees off:

The bottom line then is yes, at least in this example, the speaker grill does make a difference. However, the difference is quite small, restricted to the high frequencies (the Paradigm S8 speakers crossover at 2kHz so it's the tweeter frequencies affected which makes sense from a wavelength perspective). Your mileage may vary as usual but I suspect in general what I'm seeing here is rather typical...

-------------

Doesn't seem like much new this week in audiophile news. Looks like another audio show has gone by without Meridian doing any A/B demonstration comparing their MQA encoding with a reasonable comparison like standard lossless 16/44. This seems odd after so many months of demos. Gee... Could it be that there's minimal perceptible difference using the same mastering?

Remember: Get your results in for the Digital Filters Test! We've surpassed 40 responses... Keep 'em coming!

Have a great week ahead and enjoy the music...

16 comments:

  1. Interesting. Though it does depend a lot on the type of speakers and grills. I have Focal Chorus speakers, and there is a separate grill over the tweeters, which has quite large holes. Unlike the grill over the mid-range speakers, the tweeter grill is metallic, so, given the size of the holes, I doubt it would have much effect.

    All Focal Chorus speakers do this, as you can see here (not the same model I have):

    http://www.focal.com/en/enceintes-hifi/38-chorus-836-v-3544055691112.html

    ReplyDelete
    Replies
    1. Yup, Kirk, nice speakers! Lots of variability depending on construction of the grills...

      I'm sure any reputable manufacturer would make sure that the grill affects the sound minimally since I think everyone realizes that consumers listen with them on or off. I don't think it's in anyone's interest to use the grills as some kind of "tone control"!

      Delete
    2. Oh no, what have you done Archimago! Now we will have people making 3rd party audiophile grade speaker grills with batter operated network boxes that provide increased transparency and widen the soundstage into your neighbor's house.

      Delete
    3. Hmmm... Interesting side business :-).

      $1000 "ultra acoustically transparent" and/or "soundstage enhancing" replacement grills anyone?

      Delete
  2. Hi Archimago,

    Some things in audio are just so obvious ... but I am glad that you measured it ... if only you could measure common sense.... :-) It would be interesting to redo the test pointing the mic directly to the tweeter.

    In your previous post you are worried about -100db noise, and in this post you state that +/-3db diff at ca 4kHz is "quite small".... Digital audio is just SMALL part of HiFi audio experience man!

    ReplyDelete
    Replies
    1. Yes. Of course in audio many things are relative aren't they?

      On the digital side, we can say that a certain hi-res DAC (A) measures more accurately than another (B) with a signal difference down at -100dB when the noise floor is at -130dB. This is "obviously" different and suggests an inaccuracy in DAC (B). It's not to say that DAC (B) sounds "bad" or anything but we can say as a perfectionist that from the engineering perspective DAC (B) isn't as good as (A) in terms of accuracy. Meaningful if we spend quite a lot of $$$ and expect the "best" in all areas of performance.

      On the transducer side like the measurements here, differences are obviously much bigger! A good reminder of how important the speakers (and ultimately the room) is in the scheme of things. When just removing the grill can result in these kinds of changes, it really puts into perspective the importance of things which many obsess about, like say expensive cables, or folks who wax poetic about "amazing" differences between ultra-expensive DACs yet the measurements seem to suggest essentially inaudible differences...

      This is why for years, I have said that I can measure anomalies on the jitter test with DACs but I really do not feel jitter is an audible issue - at least at the typical levels we see in even reasonably priced digital gear these days.

      [As an aside, if you're referring to the -100dB 8kHz tone from the USB circuitry I previously talked about, realize that this was just the measurement out from the pre-amp and that level is somewhat arbitrary depending on gain levels I applied on my ADC... With that unusual case, the 8kHz interference was audible once it got amplified by another 30+dB through the monoblocks, thus I needed to find a way like with the optical USB cable to remove it; especially at that very annoying 8kHz frequency.]

      Delete
    2. Can I ask you what the "real" noise floor is - not the one shown in the FFT but the one that is correctly calculated using the bin size used for your FFT?

      Delete
    3. Well, noise floor in my room when I tested (in the evenings) was measured as ~30dB(A) SPL. The measurements done here were calibrated with white noise 68dB... >30dB spread between the sound level played and noise floor in the room - I trust this is adequate for these kinds of measurements... Not like we're measuring DACs with 100dB+ range!

      Delete
  3. Hi Archimago, thanx for your answer.

    Your reasoning (common sense) is why I like your blog :-)

    All best.

    ReplyDelete
  4. I would dispute that the difference is small: a couple of dB (and more) across a broad range of frequencies should be quite audible, I think.

    ReplyDelete
  5. Would love to see you do this with a projector screen intended for centre speaker to go behind the screen.

    ReplyDelete
  6. Hi Archimago,

    Is it 'grill' or 'grille'? Me thinks it's grille, but then again I say potato and you say potato.

    I noted your comment that you can't really tell the difference between speakers with and without grilles :-), yet you measured a 'significant' difference in the sounds produced by your speakers with and without.

    I got thinking: supposing you offered the readers of your blog a further test to determine whether they could hear a difference. Simply record the two pieces of music or sound, and offer people a simple A/B choice. Maybe there are people with 'Golden Ears' who will be able to hear a clear difference, in which case the difference you measured truly will be significant, or else maybe the results will point to there being no discernible difference at all (meaning that up to 3dB difference at some frequencies is inconsequential). I know that people can test their own speakers at home, but the difference is that if you were to do it, you'd be offering a test of two sounds with known differences.

    I then got thinking some more: if, in the course of conducting the above test you were to do a further test on one of the samples (say with the grill removed) but for this test you recorded the same sound twice but using different USB cables, you could provide a much more meaningful test of cables. In your tests of cables to date, you have largely done the tests using signals, not sounds. I know you have offered subjective thoughts as well, but the tests were done purely on signals. I'm not challenging the assumption that the same signal must produce the same sound, but I'm opening up the possibility, however remote, that different cables may not affect the signal, but may affect the sound. I'm a cable sceptic, and I don't think so myself, but you seem to have a test method which measures the sound produced, and on the face of it, does so with greater accuracy than your hearing permits. Perhaps you have 'cloth ears', and things you can't detect, others can do readily. Again, I don't think so, but you have a simple way to find out.

    I'm mindful of volunteering someone to do something, particularly if I'm not inclined to do it myself. As an inducement, and in support of the scientific endeavour you place in such matters, I offer you an 'audiophile USB cable for use in the above stated test. Why, you can even keep it and not send it back. I say 'audiophile', it'd be a Wireworld something or other that cost around $150 for a 1m length. I know that these days, that is probably a 'budget' cable, but nevertheless it is sold as an audio USB cable which brings many benefits beyond your ordinary wire.

    In any event the offer of the USB cable stands. You might not use it, but having one may give you some 'cred' with the 'true believers'.

    Cheers,

    Bob

    ReplyDelete
    Replies
    1. Hi Bob, and Archimago,

      I have done blind tests with/without grill(e)'s some years ago while having Focal Electra 1037 speakers. I got it right 10/10. Since Electra have separate grilles I have concluded that there is no audible difference in the bass section (go figure :-) and could not tell the difference in the mid section (crossover 2k), but there was audible difference with tweeter grill on/off.

      The difference in my case was audible as slight change in tonal balance, and perception of soundstage. For me it was good enough reason to take the grill(e)s of the tweeter (and mids to be on the safe side :-). Of course, now we could start endless debate about Focals grill material, type of grill, type of driver, my ears, amplifier, room acoustics…. thats why i am glad that you measured, and TO A CERTAIN DEGREE confirmed something that I heard.

      On the other hand, regarding your post, my “true believer” friend that can hear power cables, USBs, speaker stands etc…keeps his grills ON Willson Sophias stating that he read that Willson people measured grills +/-0.5dB, and thats irrelevant in his opinion. You see how important measuring is :-)

      As for USB cables, at the same time I blind tested grills, I was switching to comp audio and got my new m2tech YoungDAC. A friend of mine (Focal dealer) gave me four USB cables for a few weeks to give them a try. 5$ Bandridge, and three audio branded cables up to 200$ + 3m generic cable that I got with DAC. After a few days I politely returned branded cables and bought 1m Bandridge just because 3m USB that I got with DAC was impractical. I use it to this day.

      Bob, USB cable stands....priceless!! Try it!! Gives you at least 2 inch in length and 1 in girth :-)

      Delete
    2. Hey there Bob:
      Thanks for the thoughts and generous offer of the USB cable... As far as I'm aware, "grill" and "grille" should be interchangeable as per the fund of all human knowledge known as Wikipedia :-):
      https://en.wikipedia.org/wiki/Speaker_grille

      Yes, indeed I could run tests with recordings from different USB cables as others have done over the years. I remember seeing recordings of SPDIF cables like on "Best of Chesky Jazz Vol. 2" years ago. Also, wasn't there an article with numerous USB cables tested recently like this - I think maybe some European magazine in 2014?

      But then what do we do about the folks who insist on comparisons with AudioQuest Diamonds >$500 USB? Or how about folks who claim the test is invalid because the USB cable from the ADC to my computer isn't "audiophile", or the analogue XLR cables from DAC to ADC aren't good enough, or that I would need a much better ADC itself - maybe like an Ayre QA-9 to truly make it audiophile-approved?

      This brings up the issue of why I challenge others to demonstrate a difference and leave a link for all of us to see! Why should it always be up to the objectivist folks? As far as I'm concerned, the objectivists have over the years shown the lack of difference whether through blind listening tests or measurements... Yet one sees *nothing but faith and testimony* from various companies and pure subjectivist "believers". At some point, one has to ignore those folks.

      In the same way, I believe that subjective reviewers should show their hearing credentials and openly post some basic personal information like *how old* they are. Not trying to discriminate based on ageism but one can surmise a thing or two about hearing and age, especially when we're talking about at best tiny differences. Here's a post I did on this awhile back:
      http://archimago.blogspot.ca/2014/02/musings-golden-earism-philips-golden.html

      I see that as of today, 16,362 people have started the training and 2133 have completed - a 13% success rate. Of course not everyone perseveres to complete but I think tests like the "Philips Golden Ear" should be a *pre-requisite* for subjective reviewers to at least show us some measure of competence and discipline.

      Anyhow, I guess the long and short of it is that indeed we could run these tests reasonably easily. I'll just record the analogue output from the DAC, distribute as I have in the past, and receive the anonymous survey results. The procedure is straight forward. I think the results posted with signals already speak for themselves for those who have thought about this matter and see the world with reasonably scientific mindset. Maybe we can have a poll to see how many people want me to proceed with a test like this once the current filters test is done!

      Delete
    3. Marin:
      Thanks for the anecdote. I think in audiophilia it's realistic anecdotes like these that rarely get heard... Instead we're wow'ed by claims of remarkable differences between cables costing hundreds or thousands. I guess because we all want to achieve sonic nirvana and are always on the lookout for the next best thing. Plus this is the kind of thing that the "industry" wants us to believe.

      Good example of cognitive/intellectual dissonance when +/-0.5dB from the speaker grille is regarded as inaudible but USB cables, power cables, etc... with immeasurable properties thought to be significant.

      Delete
    4. I am an architect, so I guess I have to be on both sides - engineer/artist - objective/subjective. But I am not.

      Me and 99% of audiophiles may not have the knowledge or equipment to do scientific measurements, but we all have ears and at least one friend (or wife :-) to do the switching of cables, stands, grills,… and IMO if one is really interested in HiFi audio, some knowledge of acoustics and electronics is required.

      It is much easier to go with the flow and shout *I can hear the difference!!!*, then to educate and at least try to understand how things work. People are lazy and ignorant, 90% of *true believer* colleagues that I know had D's in math and physics :-)

      Investigate!

      "cognitive/intellectual dissonance",…. brand obsession. May be true that 0.5dB is inaudible, maybe not. Problem is he never tested it. Willson marketing claim it is irellevant, and they are not to be challenged :-) In that same manner true bileivers can hear or not hear anything …. Cognitive dissonance MkII

      Delete