Hey SQ nutters.

Over the long weekend we had recently, I had a bit of a shock re: cabin acoustics I thought I would share, hopefully others can add their experiences in.

I was driving with my girlfriend along a stretch of country road, enjoying the BeeGee's on my new DPLII 3.1 system (and LOVING it). Anyway, at some point I noticed the system didn't sound right, the left of the stage collapsed, and my side of the stage was over emphasised. I told my girlfriend something was wrong, and then I noticed it - she had lowered her sun visor. This had affected the reflections on the left side of the dash/windscreen, causing the left-stage collapse I noticed. I asked her to put it back up, and when she did, the stage was back, even and laid out across the dash evenly. This wasn't just airy fairy esoteric stuff either, my girlfriend who is no audiophile (yet) could hear the difference as we raised and lowered the sunvisor back and forth.

One of the other interesting things I've noticed is the effect of moving the seat forward or back. When moving it forward (ie granny style) I find that the stage becomes narrower, and that the centre image becomes more biased towards my side (that is, it shifts to the right). When I put the seat all the way back (ie sik habib style), the stage becomes wider and the centre image moves closer to the centre of the dash. Hence why everyone who knows me, knows I drive with my seat as far back as the rails allow and tilted as far back as possible while still permitting the car to be steered

One of the other things I want to experiment with is the effect of a carpetted dashmat on image definition and stage height

Anyway, what are experiences other people have had with cabin acoustics?

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Custom SQ System
Dolby Prologic II in 3.1

Source: Clarion DXZ925 w/ DPL2 Decoder - Front Stage: Boston Acoustics Pro 6.5's - Centre Channel: Boston Acoustics Pro 5.5LF - Ambient Satellites: Boston Acoustics 3/4" Kortec Tweeters - Processors: Audiocontrol EQT's - Subwoofers: Earthquake BR12's - Amplifiers: Kicker IX404's - Power: Stinger 1 Farad HPM Capacitor
Sounding sweet and taking it to the street

Just regarding why the centre sounds so much more defined as you move the chair back... could be that the L and R path length diffrences decrease as you move the chair back...??

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SpLbOuNd

T-Bro, i've noticed that things like cabin temperature, open windows and seats forward affect the SQ greatly. Things like moving seats back and forward shouldn't really surprise us as this is similar to a home setup. The closer to the fronts you get the more you lose the image. Then again, you can only go back so far before you again lose the image. It's all about balance, and in your case it sounds like you have to drive from the back seat to enjoy SQ sound .

Anyway, the carpeted dash will be an interesting experiment. IMO you will get a more muffled sound, as it will greatly reduce the reflections in sound from the dash and front windscreen. Not only that but i don't think it would greatly improve the asthetics of the car.

Let us know how it goes with the dash mat.


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Honda - The Power of Dreams
Honda Integra VTi-R

System in progress: Alpine, Audison, G-Spot, JL Audio, Morel, Optima

In my car you can hear the diff with glove box down or up but only from drivers seat.

Anyway seating position etc will all possibly impact on stage and thats why in compotition you set these things and judges are not allowed to change them.

This can be a good and bad thing as I am fairly tall and have heard cars that sounded awesome to those not as tall, and myself when I lowered my head and slunk down in seat, but from my normal level wasnt as good. I have to judge from my noraml seating position, and so it may be worth getting a couple of pillows if your not that tall, when setting up our front stage, so it will impress everybody regardless of height

Anyway get your girlfriend some sunnies and remove the sun visors
peace
Cyberpunky

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hehe, my glovebox makes a HUGE difference to the sound, almost blocks off the left side completely!!! Other than that, have noticed leg positition makes a big difference too, it usually sounds better having a leg there that sits "below" the bottom of the driver, actually changes the staging slightly... However, my speakers are currently mounted high (i know i know, i'm making pods!) hehe
But it should be awesome once done
Oh and another note, picking up some Dynaudio tweets this week hopefully, or next hehe
Aaron

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Noise producer - Clarion DRX9675
Noise Increasers - MTX 500D - Pioneer GMX-944 - Bridged to the front stage
Making Noise Heard - CDT Audio HD Splits - Pioneer Coax (Bah!)
Low Bumpy Noises - Alpine Type R - Sealed 1 cuft(126.7db @ 35hz, with lots of cancellation)
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-Team SQ, A Reality Not a Dream :)
-Before you criticize someone, you should walk a mile in their shoes. That way, when you criticize them, you're a mile away and you have their shoes.

The dashmat makes zip difference when there's no drivers in there I can tell you that much.. install a mid in there with the carpet over the top and the front stage becomes too muddy. Remove it (carpet) and the staging becomes too bright.

The rear of my roof lining is also loose (thanks Mitsubishi) and when you fade towards the rear fill they cause it to resonate and gives a very interesting colouration to the sound.. sounds like a plastic panel rattling slightly.

I got my restrictor and fiddled with it on the way home from work one day. To be honest the stereo sounded so much different it was spooky. Which brings me back to a topic I started a long time ago about exhaust harmonics and the effect on stereo performance, its an aspect of car audio I find extremely interesting.

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TR Magna: Alpine, Orion, Kenwood, StreetWires Big, Maroon, Different
WF Festiva Clarion, Kenwood, Rockford Fosgate, StreetWires Small, Blue, Different
- 2nd Bathurst LiveWire 0-160 Class, Oct.2k2 @ 138.4dB

Andu: Yeah take a photo, this is the only sport we're good at !
Clean throttle, IAC & filters, run a tank of PULP + 1 cup Metho
Required: Kove Armageddon, JBL 1200.1

moving the seat back effectively reduces path length difference (PLD) just as moving speakers forward to the kickpanels does. and yes, i drive almost sitting on the back seat

from reports from IASCA winners in the USA, dash mats do make a positive difference even with systems with kick/door pods, so it's worth trying. i can actually hear the difference between cars with leather interiors, and those with cloth interiors - cloth sounds more solid and accurate, leather is airy and has more echo. so adding more carpet to the dash which is one of the more reflective areas, has to have some kind of impact. there are reports that carpeting under the dash and around the steering column help imaging too, as this reduces distracting reflections from the nearside speaker, helping to shift the image closer to the centre. some guys even find that turning the steering wheel upside down at SQ soundoffs helps with imaging, as the steering wheel hub presents less of an obstruction to the nearside speaker. all fun stuff worth considering!

the glovebox doesn't surprise me given its reflective nature and location close to the doors/kicks. but these are generally shut during driving anyway (my huge door pods prevent opening the glove box with the doors closed!).

and the impact of exhaust is interesting - Blackice, check out my tutorial file "Overcoming the Challenges of Car Audio" in the techical section of the CAA website, i cover it somewhat in the section on extraneous noise, where i compare the ambient noise between a quiet factory sedan with OEM exhaust (my magna), to a sporty coupe with low profile tyres and 2 inch aftermarket exhaust (a lancer). i conducted these tests myself with an SPL meter along sydney roads at 80km/h. anyway, short and curly of it is that sports exhausts and ultra thin tyres do not a good listening environment make!

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Custom SQ System
Dolby Prologic II in 3.1

Source: Clarion DXZ925 w/ DPL2 Decoder - Front Stage: Boston Acoustics Pro 6.5's - Centre Channel: Boston Acoustics Pro 5.5LF - Ambient Satellites: Boston Acoustics 3/4" Kortec Tweeters - Processors: Audiocontrol EQT's - Subwoofers: Earthquake BR12's - Amplifiers: Kicker IX404's - Power: Stinger 1 Farad HPM Capacitor
Sounding sweet and taking it to the street

[Edited 1 time by T-Bro on 16 October 2002 at 13:15]

*T-Bro changes moniker to "Ful Sik Habib T-Bro" *

Interesting level of change for such a small alteration in the interior, especially considering where the main front stage drivers are in the Magna .......

Sometimes I think that it is practically miraculous how good some systems sound given the environment we stick them in, fabric, glass, leather, reflective surfaces at all sorts of different path lengths and angles.

Ah, the mystery of it all


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Mazda SP20 - NOT yellow,Dynamat Extreme and G Spot in front doors
HU - Alpine CDA-7876RB
Audison VRx 2.150EX front stage amp
JL Audio 500/1 Class D monoblock sub amp
Front Stage - Morel HCW 6.5 woofers, Morel MT2 tweeters, Morel MX2.2 x-overs.
Rear fill - stockies with power from HU (not that they get any)
Sub - Kicker S12L72 in 75 litre 30Hz slot-ported display box.
Stinger cables and connectors etc
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Well no more booming exhaust for me drowning out half the subtlties or causing bass cancellation for me. Installed the restrictor at lunch time (with a hammer) and its all good. Unfortunately money contraints and my new found desire for SPL in the Festiva has put my new front stage on hold for the moment. On the plus side, I'm thinking 4 way, possibly fully active

I'd never considered the steering wheel as a source of interference, can't say I've noticed any either. But then again I own an Alpine steering wheel .

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TR Magna: Alpine, Orion, Kenwood, StreetWires Big, Maroon, Different
WF Festiva Clarion, Kenwood, Rockford Fosgate, StreetWires Small, Blue, Different
- 2nd Bathurst LiveWire 0-160 Class, Oct.2k2 @ 138.4dB

Andu: Yeah take a photo, this is the only sport we're good at !
Clean throttle, IAC & filters, run a tank of PULP + 1 cup Metho
Required: Kove Armageddon, JBL 1200.1