I know there have been many comments about the sound quality of the system, ranging from poor to excellent. I've had my 2010 convertible for a few weeks and have played around with the settings with mixed results as well. So I whipped out my trusty Audio Test CD, sound pressure meter and owner's manual today to measure and calibrate the system to as accurately reproduce music as possible. All measurements and listening tests were done from the drivers seat, and the suggested settings will optimize the sound quality for the driver.

The first test was a polarity phase test to ensure the speakers were wired up correctly and all was good.

Next was to check for stereo imaging, where the speakers will ideally create a center image, with the singer's voice for instance coming from a place in between the speakers, rather than from the left speaker which is closest to the drivers ear. In "stereo" mode this phantom center image was predictably and poorly located around the driver's tweeter location. The "3 Channel" mode image came from the same location. Only the "PLII" mode shifted the image to a more realistic place in-between the speakers, and basically directly in front of the driver in front of the steering wheel. There is an additional DSP setting for "driver", "front", and "all", but since there won't be any audiophiles sitting in my back seat any time soon, and I couldn't really hear any difference between "driver" and "all", so I chose "driver".

I then checked to see if the higher frequency sound from the speakers changed in intensity as you shift around in the drivers seat, and the SPL meter and CD pink noise indicated the left speakers provided even sound, but the right was a little uneven. I doubt that a discerning listener would be able to detect that, or that it would have any impact to the overall listening experience.

A common criticizm is about the amount of bass, and I checked frequency response across the audible bandwith. With bass, treble, and sub settings in their middle position, and using broadband pink noise with frequencies centered at 125, 1000 k, and 8000 hz, I measured 80, 79 and 78-81 decibels. These frequencies represent bass, midrange and treble. The treble range of 78-81 was due to the right speaker's sound dispersion variation mentioned above, and the readings were as I moved the SPL meter location slightly.

The measured frequency response of 80 db (bass), 79 db (midrange) and 78-81 (treble) isn't perfectly flat, however many listeners prefer a "pear shaped" freq. response, with slightly more bass than midrange, and slightly less treble than that. I have found that the treble was generally a little too pronounced, and these measurements confirm what my ears had been telling me. Reducing the treble from the middle setting by 2 positions settled down the highs nicely!

Now if you think the bass seems weak with the "sub" setting in the middle position you are half right. While the broadband pink noise centered at 125 hz provided the desirable pear shape frequency response curve, the lower and deep bass frequencies are pretty weak. I started measuring using separate low frequency test tones at 20, 25, 32 40, 50, and 65 hz and found them much lower than those at 125, 250 and 500 hz, but the "Low Battery" warning came on and turned off the audio system to preserve power. Testing with the engine running isn't possible because the exhaust drowns out the sound of the test tones. Testing the deep bass will continue in a few days when I can get back to it and I'll update this post.

My tests so far indicate that the setting for a more realistic stereo image is with "PLII", adjust Bass and Subwoofer to middle setting and Treble middle minus 2, and DSP to "driver"... or "front" if the passenger's listening pleasure ranks high. From there I'd twist the subwoofer volume up or down to suit personal taste or music selection. I like deep bass, but with some selections you may find cranking the subwoofer muddy's the overall bass quality too much. The audio quality would really benefit from a good quality subwoofer and large amplifier that can reproduce accurate and clean deep bass at realistic listening levels.

I think some will agree however that the best aural delight comes from the exhaust, with the "dynamic mode" being the best setting... and I wouldn't trade a fraction of that sound quality for a better subwoofer. Here's to great sounding music rooms and home theaters...and even better sounding sports cars
Continued in post 13

Bruce

 

I heart you Bruce. That's awesome.

 

Bruce, best post since I've been on board! Useable, comprehensive, and proof that I'm not crazy

Thanks and if you have any other data, we will soak it up like sponges!

Appreciatively,

Skeeter

 

Glad you guys enjoyed it! But the jury's still out on you, Skeeter... I just read your new thread and think a strong case could be built for you being as crazy as the rest of us!

Bruce

 

Great information there Bruce.

I'll have to have a play with the settings of my Alpine system now and see how I can get it as good as it can be.

 

Bruce, Thanks for the GREAT post! While I love the sound of the B&W speakers in my XKR, I am CRAZY about the sound of the exhaust under WOT!!!

FYI - sports cars first started sounding really great way back in the late 50's. As the original owner of a 1960 Corvette (thanks, Dad!), I received a complementary recording of a 1961 Corvette with the 283ci fuel injected engine and off-road exhaust mufflers driven by Zora Arkus Duntov, the legendary Corvette engineer. As soon as I heard that recording, I got a set of the off-road mufflers from my Chevy dealer and enjoyed that sweet music for over 42 years! Imagine my surprise when I just found that recording on YouTube! I think everyone else will enjoy it, too.

Sounds of 1961 Corvette - YouTube

.

 

Nice soundssss

 

That sounds AWESOME!

 

Thanks, Bruce. I agree that my CDs and iPod sounds best set on PLII. I have to crank up the subwoofer to hear the bass with the top down.

 

i wonder if the same holds true for the alpine system

 

Hi Bruce,
Thanks for the post. I happen to own B&W's flagship line in my HT. 800Ds for mains, 803Ds for rears, HTM1D for center and ASW855 for sub. They are truly stunning so I know how awesome B&W equipment can perform. I was therefore expecting an order of magnitude improvement over other car sound systems in my XKR with the B&W transducers. Unfortunately, no matter how I tweaked the audio settings on the XKR, the speakers/amp that came with my Toyota Venza (yes, TOYOTA!) still sounded much better than the B&Ws. I think the engineers in Steyning should stick with what they know best -- building speakers for studios/homes.

Just my $0.02

Mike

 

Hi Mike,

Great new ride there...congrats. The theater sound quality using your fine HT speakers is very much influenced by room dimensions, room acoustics, speaker placement, equipment calibration...and program material of course. Systems in sportscars with limited interior space face formidable challenges, and larger vehicles like the Venza and my Sienna have major advantages over the XKR convertible.

I hope you find the rest of my evaluation useful...I'll post it shortly.

Bruce

 

This is the continuation of the testing started in the original post.

Today, with a fully charged battery, I started testing low bass capability with low frequency test tones and sound pressure meter. With the "Bass" and "Sub" set to middle level in the "settings" menu I recorded the following in the first column, and with the "Sub" set to 3 above middle I recorded the second reading in ( ):
25 hz - 68 decibels (74)
32 hz - 81 db (84)
40 hz - 84 db (87)
50 hz - 88 db (90)
65 hz - 86 db (87)
125 hz - 83 db (83)

From these measurements you can see that the subwoofer on the middle setting provides strong bass down to 50 hz, and then it falls off 4 db at 40 hz, another 3 db at 32 hz, before plunging at 25 hz. A drop of 3-4 db is definitely noticable, and in the low bass region it is particularly significant. However, raising the sub level by 3 positions dramatically improves things, with 32 hz now being actually slightly stronger than 125 hz at 84 vs 83 db, and even 25 hz starting to get in on the action with an increase of a whopping 10 db!

What all this means is that the `Sub` setting adjusts the lowest frequencies the most, filling in where deep bass is needed most, and does not interfere with the higher bass frequencies that are controlled with the `Bass`level. This is critical because it allows the subwoofer to be cranked up to suit personal tastes without increasing the higher bass frequencies (like 125 hz) where the human ear is more sensitive, and where overly boosted levels degrade sound quality. The male voice is in this frequency range, and boosting its level makes male voices unnatural, in the same way that exaggerating the 250-300 hz range affects female voices. But if bass below 125 hz is exaggerated it adds to the listening experience. Although there are few instruments that produce frequencies below 50 hz, being able to hear those that do distinguish a system with good bass from those that don`t. Raising the `Sub`level to 6 positions above middle produced levels of 80, 88, 91,92, and 89 db, and while that looks impressive, it did not enhance the listening experience at all, and knowing that deep bass consumes a lot of power, I showed some restraint in order to keep amplifier distortion inaudible even at high volumes.

Musical Evaluation

Measurements are an important step in calibrating an audio system, and the listening tests are affected by those, as well as additional factors.

I started by listening to audiophile recordings specifically chosen to reveal particular aspects of equipment. I`ve used them a number of times in the past when completing client`s music rooms and theaters. I was generally impressed, although that was probably more due to my realistic expectations than ultimate fidelity. These recordings are brutally revealing, and even purpose-built music rooms can struggle with them.

Next up was the ACDC Back in Black album. I`ve listened to that one a hundred times over the years, but have never enjoyed it in any vehicle as much as in the Jag. It sounded absolutely amazing, and I cranked the volume as high as my pain threshold would allow (approximately three quarters full). There was very little distortion, with clean highs and honest to god deep pounding bass that you could feel in your chest. The SPL meter recorded high 90 and low 100 db volume levels, and that was enough to flutter my pant legs on occasion. The door under my arm was vibrating madly, as was the floor under foot.

This album, and the others I used, have excellent stereo channel separation, with different instruments sounds distinctly played through the left or right speakers. In the PLII setting vocals came from a realistically centered place in front of the steering wheel, as discussed in the original post, and in stereo they came from the drivers door tweeter location...however, all the instruments came from exactly where they should regardless of setting. I found myself switching between PLII and Stereo repeatedly. The Stereo mode just sounded a little bit cleaner, with the digital processing artifacts of the PLII mode being slightly noticable in direct comparison. I found I didn`t mind the vocal image being off centered terribly, although leaning my head over the center console identified the best listening position of all.

I was immersed in an epic musical experience that was about to become religious with Pink Floyd. Another Brick In The Wall (Part 2), Money, Time, Sorrow, Comfortably Numb...all reproduced brilliantly. Deep bass notes played at 100 db! That`s enough to get you evicted...even from a parking lot. The race track I took mine out on has a 94 db noise limit and tests cars for compliance. The XKR`s exhaust can pass but don`t try it with Pink Floyd cranked! Steppenwolf was up next, and I finished with Best of the Doors. That`s the only album I had on 8 track tape when I had my `70 E-Type...and it sure sounds a whole lot better on CD in the XKR!

So while I sure didn`t buy this car for the fidelity of its sound system while blasting down the freeway with the roof down, and sure didn`t expect it to sound this good, I`m very pleased that it`ll sound great the odd time I might care to do a bit of critical listening. There might even be a better sounding system out there in another sports car, but this was the car of my dreams...and it turns out the audio system isn`t half bad either!

Final settings: Bass-middle, Treble-middle minus 2, Sub-middle plus 3, PLII best vocal image, DSP-driver, balance and fade middle. If you turn up the volume and still can`t hear it over intense wind and exhaust sound the problem isn`t the audio system!


Bruce

 

You know, I tend to prefer the stereo or 3 channel spot vs the PLII myself. I was feeling that it pulled too much of the sound in addition to the vocals to the center stage. I'm a bit of a spoiled brat when it comes to sound myself. I think I need therapy for the amount of money I spent overhauling my last car (I do the work myself -- no one solders all their work anymore), and now I've been invaded by Martin-Logan inside the house. I could still use a little additional SP inside the Jag, but I really don't think I can complain about SQ and your tests here Stuart provide quantifiable reinforcement of that.

Interestingly enough, I suspect that a lot of complaints about sound can be traced to their source. MP3s are often not ripped correctly, or are rips of an internet radio station which is akin to recording something off of FM. And the Satellite Radio quality varies by channel, but a lot of those channels are NOT getting full audio spectrum bandwidth -- the same songs from a CD and the Satellite have a profoundly different sound when played back.

 

I think you're right about source material likely being the complaint culprit. Some songs over FM sound good because of lots of bass, reverberation or strong stereo separation, but FM reductions in broadcast dynamic range, channel separation and frequency range really ruin most sound tracks for anything more than background sound...and the better the sound system the worse they sound. My wife hooked up her i-pod and it sounded so bad I had to shut it off (not sure if it was a bad setting on the i-pod). But Cds sound great, although I haven't tried yet with the roof down...and I'll be pretty forgiving when I do.

I think we need a home audio sub-forum as it seems there may be lots of us with decent systems in our homes!

Bruce

 

Another cause of subwoofer/deep bass performance criticism, beyond poor source material, will be related to the volume level you are listening at. Where I measured and heard impressive deep bass at high volumes, the human ear is much less sensitive to low frequencies at lower volume levels. This relationship can be seen in the "Equal-loudness" contours seen here... Equal-loudness contour - Wikipedia, the free encyclopedia. This shows how much louder ever-lower frquencies need to be reproduced in order to be heard at the same perceived loudness level.

Home theater subwoofers have the benefit of standing waves formed between parallel walls that amplifiy their lower frequencies, but unless the interior of your car is 20 feet long and rectangular in shape it just isn't going to happen for you.

And lastly, convertible owners are going to be the most challenged of all. The tactile part of bass in a theater is caused by the large driver's ability to pressurize the listening space. When your seat at home shakes it's actually because the floor is flexing. To ensure this desirable factor is utilized dedicated home theaters are built airtight whenever possible, and THX certified subwoofers are rated for the size of space they can effectively pressurize. The problem is obvious in a convertible with a canvas roof up, and especially when it's down.

I enhanced the deep bass tactile sensation for lower listening levels in my theater by installing tactile transducers under the seat riser platforms. They run off the processor's LFE channel and are separately amplified.

So those are some of the bass challenges that manufacturers face. But we should find comfort in the knowledge that when our audio systems come up a little short we still have that wonderful exhaust sound system!

Bruce