DoubleWhoosh

Good in theory, but the car didn't work worth a damn...

Fair imaging, staging was average, tonally it wasn't even close. Sitting that far back caused stage width to suffer greatly, and for the supposedly optimal speaker layout there was little if any stage depth. The sub bass was definitely not blending with the rest of the sustem (probably since they were like right behind your back).

Of course that guy comes in thinking he's gonna womp on everyone, he got sent home with his tail between his legs.

Just goes to show that it isn't as easy as people think...

Harry won with the Acura Legend that year for best of show, but I had a processor take a dump and limped it through the lanes with a little bit of system and engine noise...if that didn't happen there's no doubt I would have had him! Oh well!!! =|

That show was pretty awesome though, 20 judges judging all 25 cars with the scores averaged. That was truly the measure to see how all the cars stacked up, with no victories by luck.

Todd Matsubara
TM Engineering LLC

bbfoto

Todd, Percy, & Ira,

I took this tip from Scott Buwalda and Mark Eldridge and it WORKED! This applies especially when your mid and tweets are separated by more than 6 inches (e.g. mid in door or kick, tweet in sail panels/A-pillars.)

If your midrange in the door can play easily up to 4.5k-5k without cone break up or distortion (and obviously most all 5.25 mids and anything smaller easily can), set up your crossovers from the mid to the tweet as close to 5khz as you can, preferably with 24dB/octave slopes.

I know that most of us out there are looking for a tweeter that we can cross over As Low As Possible, but I learned that this doesn't work in 99% of the car audio environments out there. It can work great for a home speaker setup, but very rarely in a car. Midrange drivers have a much wider, and more easily defined "sweet spot" for imaging cues and this works to our advantage in the car environment. The main two areas this helps are:

1) Your imaging/staging will not wander in the transitions to the lower freq's.

2) It will reduce the near-side bias.

This is especially noticable with male vocals and instuments in the 1.5khz to 4khz range. Most mid/tweet passive crossovers are set up somewhere in this range! This is an even greater problem anytime your mids and tweets are separated by more than just a few inches, and more so when they are not located in the same vertical plane.

The passive crossovers that come with most component sets, even the very high-end ones, are designed with the idea that the mid and tweet will be mounted as close as possible to each other. I'm sure that Stevie and Percy from this forum can elaborate on this.

The perfect track to test this phenomenon is "Calling Elvis" by Dire Straights. Buy this CD! Listen to the lead singer's voice. His voice should not carry AT ALL into the tweeters. At 4khz, the top end of his voice can be heard. If your tweeters are playing that low, you will have near-side bias and the image will "wander" between the mid and the tweeter.

Once you have change the XO's to 5khz/24dB slopes, if there is ANY way to play with the angle of your mids in the door to get your center image optimized, do it. I used wedge-shaped spacer rings on my mids an rotated the wedge in the door mount to get the best angle. Angle the mids without the tweets playing to get the CENTER image maximized as best you can, from both seats for competition. Don't worry about your image height and width yet, just go for the best center focus you can get. The height and width will be there when you hook up the tweets again. Then play with the angle of the tweets too if you can (if you have mid-bass drivers, too, angle those while the mids are playing before you move on to the tweets.)

The other problem with your stock locations in the GS, if I'm not mistaken, is that your tweeters have shorter overall pathlengths to your ears than your mids. Without having the advantage of time alignment, you always want to have your tweeters on a longer pathlength than your mids because all of the really important imaging cues are coming from your mids, and the early arrival of the higher frequencies from the tweets combined with their slightly increased SPL level because they are closer, throws-off or interacts with the imaging cues you should be receiving primarily from the mids.

Todd, you can always go back to your original setup since you aren't changing drivers or mounting locations. Obviously, this is something that is VERY difficult, expensive, and time consuming to do with passive XO's, especially regarding the phase relationships between the drivers. The XO frequency of 5khz is more important to acheive than the steep slope (as long as your drivers are comfortable slightly above 6khz), so if you can't change to a higher slope easily, don't sweat it, just try and get the XO frequency as close to 5khz as possible, and at least to 4khz.

It really helps if you have a versatile active crossover to test this out, such as the Premier DEQ-P9 or one of the Alpine PXA units. If you do have a P9 or something similar, you can also play with the pathlengths/time-alignment, but you will usually only be able to get it close to perfect for either the driver's seat, or the passenger's, and not both, which is usually not good for competitions, especially if you are using passive crossovers on your front stage and not time-aligning the mid and tweet independently with an active setup.

The other thing that will make a tremedous difference is to tune or EQ the right and left sides INDEPENDENTLY. I think that Stevie mentioned something about using a snare drum as a guide in tuning and XO settings in another post, and he's exactly right. Use the IASCA snare drum track with the 7 beats that go from left to right to determine BOTH your stage WIDTH/IMAGE PLACEMENT and TONALITY/SPECTRAL BALANCE while transitioning from LEFT TO RIGHT. If your system is set up correctly the Snare will sound Fat and Deep along with the higher-frequency detail of the snare wires vibrating against the bottom head of the drum. The SPECTRAL BALANCE and TONALITY of the snare SHOULD BE CONSISTENT as the individual beats travel from Left to Right! Often the snare will sound full on one side, and become "thinner" as the snare beats travel to the other side. Hope this is useful and not too confusing.

Bill Bodwell
bbfoto@hotmail.com

Percy

Bill,

How is "Scottie" doing anyways? Last I heard from him he wanted to mod out some stuff but didn't have the time.

Percy

bbfoto

Percy,

How are you? I received the above info from Scott and Mark in a discussion on the CarSound forums months ago and haven't the slightest clue what he's up to these days.

I did want to ask you about those mods you mentioned for the Sony CDX-C90 though. What are they, what do they accomplish, do they acheive anything if you are using the XDP-4000X with the C-90, how much does it cost, who does the work, and how long does it take????

My 101 questions!

Also, do you know of any mods available for the Premier DEX/DEQ-P9 setup? I love my CDX-C910, but between the multiple problems that I've had with it, Sony's customer service (or lack of CS), and not being able to see the display 90% of the time, I decided to go with the P-9 set up. I don't know anything about the op-amps, caps, or DACs in it, so I don't know if they can be improved upon or modded.

Hope all is well.

Bill Bodwell
bbfoto@hotmail.com

stevie

Hi Bill,

That was an interesting piece. Far be it from me to knock what works in practice, I'd just like to state the counterargument for the record.

>If your midrange in the door can play easily up to 4.5k-5k without cone break up or distortion (and obviously most all 5.25 mids and anything smaller easily can)

This is certainly true for some high quality drive units, although an average quality 5 inch driver will be breaking up quite badly at 5k. However, between 2 and 5k there is no doubt that a 1 inch dome provides both lower distortion and lower delayed resonances, i.e. a cleaner sound.

>Midrange drivers have a much wider, and more easily defined "sweet spot" for imaging cues

I'm not really sure what this means. Imaging cues come from higher frequencies (the twig snapping beneath the enemy's feet phenomenon). So setting your speakers up so that the imaging cues come from the midrange seems a bit of a strange approach to me.

>Once you have change the XO's to 5khz/24dB slopes, if there is ANY way to play with the angle of your mids in the door to get your center image optimized, do it.

Unfortunately not possible with the GS. What you are doing by adjusting the angles of the bass/mids is trying to equalize the off-axis frequency response for driver and passenger speakers. A five inch driver rolls off off-axis from about 2k. The further off-axis you are, the steeper the rolloff. In the GS, the driver's speaker is about 130 degrees off axis from the listening position; the passenger speaker is maybe about 45 degrees. Even if you could adjust the angles, the difference in listening angles is such that you could never get them the same. This means that the frequency response above 2k for each driver will be different, which is a very good argument for crossing over to the HF unit at between 2 and 2.5k.

Moreover, if you have a 24 dB crossover slope at 5k you will inevitably have a much faster acoustic slope at that frequency, because must add the driver's acoustic rolloff to the equation. You will therefore have unequal crossover slopes between mid and HF - and these will be different for the driver and passenger speakers. Not good.

Because of the drooping off axis response of the bass/mids at higher frequencies, there will be a dip in the power response between 2 and 5 k if you cross over at 5k. Compounding the problem is the fact that the dip will be different for the left and right side of your system.

>The other thing that will make a tremedous difference is to tune or EQ the right and left sides INDEPENDENTLY.

Now the alarm bells are ringing. On I hi-fi system this is the kiss of death. I have never done it on a car audio system but would try to avoid doing so if at all possible. Much better to design the system so that both channels sound the same. That would entail getting the power response (the sum of direct and indirect sound) of each channel as close as possible. By doing this you will have the added bonus that the sound from the passenger side will be close to what you hear from the driver's side.

What I think you are doing by crossing over at 5k is bumping the problem up to a point where the ear is less sensitive. The image will not wander between mid and HF because all the fundamental musical frequencies are coming from the mids. In my half-finished system I am crossing over a 5 inch bass/mid to a one inch dome at 2k, and the sound is locked onto the tweeter if I listen to one channel only - even when I move my head. Everything, including the bass, seems to come from the tweeter.

If you go up close to one of your speakers on your home stereo you should hear a similar thing - the sound should be coming from a single point, either from the tweeter or from a point in between the bass driver and the tweeter. You should not be able to hear the individual drivers.

They say, if it works don't knock it. So the above is offered as food for thought.

By the way, Calling Elvis is a great track.

Stevie

Ira Senoff

I never had the opportunity to be sonically punished by the Lemans but I'll take your word for it. I never wanted to listen to the cars that used installation techniques that made the car impractical as a daily vehicle. Just not realistic nor does it follow along with what IASCA was all about......

You're not kidding, it's not easy staying competitive year after year.....

Now, does Harry know you would have taken him that year or can I create some type of heavy hitters debate like the EH/RC battle on the CarSound Forum......

When you get a chance, give me your thoughts on mild mods to my GS400 (I don't need anything like my Supra was). Just some extra kick in the pants and more detailed handling/braking would be nice. Also, w/o breaking the piggy bank, what would you suggest for wheels. Car should be done with the "street" install mid month and, if possible, I will do some of this work before IASCA finals..... (cut off some driving time to the Carolinas)

Ira Senoff

Bill,

Thanks for the detailed info. Thankfully for me, my midrange and high frequency drivers will be mounted co-axially in the kick, powered independently, crossed actively and controlled by the P9. I will be able to use the info when I build the Expedition for my wife's daily usage.

Ira

ahn3447

Instead of doing mods his gear, he purchased new version of ODR processor which is P70x II.

I am pretty sure that he would be satisfied with his new toy.

How about your story regarding SCD-1 ? It is surely a good cd player.....

Percy

Ahn,

SCD-1? (BIG GRIN!) They're good "out of the box", fantastic when modded. For 5k, it's beating out the Krell KPS25 that I listened to ... and that's at 20k. Even the 777ES sacd player can't do that.

Scott can still mod out his new P70x II.

Percy

Percy

Bill,

ANYTHING can be modded, especially in terms of car audio equipment. You just have to know what you're doing. IF a car audio manufacturer went the right way and didn't use op amps (but instead complete discrete) then the sound would be much better. But remember, like any industry, they're out to make money and in most cases, hype the product.

The C90 is one of the best, internal wise, that I've seen so far. OP275 op amps (not bad, but not great) can be improved upon. You just have to be careful on which op amp you use. I've already swapped out the OA's in my C90 and did a a/b/a comparison. The 1000 dollar C90 WASTED my 4,250 dollar, fully modded (caps, op amps, resistors, etc) Krell. Part of the reason is that Ol Danno (Dan D'Agostino) was using discrete transistors in the analog board to "beef up" the sound. In doing so, he made the board sound a bit "forward" and if you listened to it long enough, a bit grungy. The C90 didn't have the analog board that the Krell did, and in doing so, kept the signal output cleaner.

Now the C90 can't touch the modded SACD SCD-1 Sony player that I have. That player constantly amazes me. And it's not even fully modded yet, just very very light mods.

P9 setup can more than likely be modded. Buy the schematic/service manual. Then we'll talk.

Percy