help with sub positioning for spl comps

[fergie_vs]

so ive got my 2 digital design subs goin in this weekend and the rest of the digital design gear

2 questions, at spl comps where is the spl reader placed to get the reading and to achieve a higher reading should i face the subs towards cabin or facing outwards away from the rear seat

help appreciated. cheers

[calais_cruzin]

Mic on dash.

Subs facing rear of car

[fergie_vs]

subs facing towards the seats?

[calais_cruzin]

No towards the boot,
sum say its better to place them at the furthest place in the boot facing out. right up agaist the boot lid

In sedan? or Wag

[fergie_vs]

sedan, while im not doubting your advice as i guarentee you know alot more about this subject than i do but how do you not get a higher reading if there facing directly towards the mic?

[calais_cruzin]

Jus try it out.

Sedans always are louder when u face it away from the listening point.

Not 100% sure, but its to do with the resonance in the boot increasing the overall loudness.

Have a look on mobile electrics aus, there was a thread couple days ago, alpine tech did a heaps of tests on postions eq n spl, best was always facing away but not right up agaist the rear seats

All this techy sorta stuff is heading out of my league a lil bit.

[fergie_vs]

well thats good as the box has just been built to sit in just behind the seats but facing outwards, just wanted to make sure i was doing the right thing. appreciate your help.

[calais_cruzin]

When u fit it, just go do sum testin, put it in different spots of the boot n try work out u think is louder.

i always find it easier to judge volume while ur driving around, so go for a cruze n change ur sub positions around until u think its the loudest spot

Ino in mine, right up agaist the boot it works the loudest but i need boot space, so it sits up agaist the seats facing the boot for daily

[holdenboy]

Yeah if you fire the subs into the car without sealing them off from the rest of the boot then it'll hurt your score.

Youre much better off to place the box at the rear of the boot and fire the subs towards the tailights, leave about 20-25cm of room in between the tailights and the sub box though to allow for loading.

The reason this works is because the subs "load" off the tailights / rear of boot and the pressure is increased as it passes back towards the rear seat. During tests in sedans ive gained anything from 1-4db by turning the box around.

[fergie_vs]

my plan was mounting them about 35cms from tail lights in order to lay my amp and capacitors in the space between the subs and tail lights

[holdenboy]

That'll be fine.

Do you have a test tone disc?

[fergie_vs]

no i dont. im new to all this, just wanted a stereo i could enter comps with. haha. ive learnt theres so much more to it than most people would assume

[holdenboy]

Oh yeah, theres heaps of little tricks and tips to SPL that will increase your score......heres a few

1. Get yourself a test tone CD, this is just a normal CD but has "tones" on it, which are just one frequency per track (the track number tells you what frequency is playing). You can anything from 0.5-5db using a test tone as opposed to a music track. just go to this site, sign up and go to the download tab, then to the test tone download and follow the instructions

2. Disconnect the remote wires from your speaker amps (if you have any). Speakers dont count for SPL in comps so youre only wasting power by having them on.

You might as well have a look at this article on the other site, it has basically all you need to know about competing in SPL competitions
Getting into SPL Competition, the begginers guide. | DecibelCar.com the SPL Knowledgebase

[fergie_vs]

thanks a heap mate, really appreciate your advise and opinions. as you just stated about removing the wiring to other speakers i did hear this somewhere else. there runnin straight from the head unit as there only alpine r types. so how do i unplug them? does this mean removing head unit at every comp?

[holdenboy]

If theyre running off the head-unit i wouldnt bother with disconnecting them......does your head-unit have high pass filters built in? If youre not sure just post up the model number and i'll have a look. If it does have HPFs then you wont need to worry about the speakers, as the HPF will filter out the low bass (the subs play) and they wont play anything.

[fergie_vs]

Sony - XAVW1

[holdenboy]

OK well it does have high pass filters, so go into the audio settings etc (look in the manual if in doubt) and turn on the "HPF" to 60-80hz. This will not just allow you to play test tones at comps without worrying about your speakers, it will also allow them to play louder as they arent trying to reproduce bass frequencies that your subwoofers are playing.

Nice head-unit BTW

[fergie_vs]

awesome so i will have vocal sound but no bass?

[holdenboy]

Basically yes, your fronts will play everything down to around the HPF setting. With subs installed you wont notice much of a change in sound, if any. But you will be able to play with Type Rs louder, thats a certainty.