advanced spl...the real deal!

Ok ladies!! tell everyone here, in this thread, how you build for spl...I want technical theory on sound, reflection, rarefraction, wave length, wave pitch, wave intensity, wave form, wave travel, wave pressure, wave loading, etc.etc.etc....

I will start with my own example. I will explain my theory, then I will give my technical breakdown and explain its relevance....Then i want the next person to do the same.

If a poster does not understand what is being said, then ask questions. Spl is not easy, yet enough of us get by in local competition by doing whats been done by others before without understanding what they are doing.....simply winging it will only let you be as good as others, and luck will only let you win by a margin. Those who want to win big, need to understand sound in a big way.

Well, my personal battle with the no-wall class had lead me to being frustrated by why my tuning needed to remain low and by enclosure needed to be large to maintain the higher score. When i reduced box volume, my subs had better excursion and seemed to perform better, my tuning peaked at higher frequency but my score fell. I also noticed that my passenger side woofer worked harder than the portside woofer when i shrunk the box.

With many hours of testing, i found i created loading issues with the waves in the box, I peaked higher freq. and made more power but i also had less port velocity. I tried angling the rear wall of the box to move the wave toward the port and it gained spl but still wasnt as loud as with the box being huge and peaking lower.

I should mention that my front baffle was 35" wide and housed 2 18" subs...

Ive concluded that the cause to my loading issue was the width of the baffle. Waves move toward the low pressure area "port" but in order to make the travel toward the port without obstruction, the wave also needs travel further back away from the subs to do so. That causes the wave to lose intensity and essentially "slow down" the enclosure now needs a longer and more intense wavelength to maintain pressure "load" Lower frequency provides more intensity over distance.

By simply using smaller woofers to allow for a narrow baffle, i believe the box could then be smaller and utilize higher frequency with a shorter wavelength to achieve higher spl. I believe angling the rear loading surface is not proper, it seems more like a band-aid affect for wide enclosures with loading issues..Yet, everybody does this practice without question and their results spl wise are only determined my the amount of power the competitor can throw at the problem.

I invite anyone to further explain what ive said and perhaps show a diagram of how you would explain it. Also, bring up an important theory of your own and like i sorta did, explain the machanics of that theory!! If anyone wants to challenge my findings, do so and explain with detail.

the whole superstreet angle is apparantly to throw the 1/4 wave closer to the mic position. you and pete didnt gain from this as you were both in low power applications.

i'll see if i can find the post where i first read about the infamous super street angle and post exactly what was said about it.


As for my spl advice!

BUY A MIC

buy a mic and try EVERYTHING, even if it seems stupid and not logical, even if EVERYONE says it wont work...TRY IT!

the only way ur gonna be louder than the next guy is trying something new and untested by others, if everyone had the same thing it would always be a tie, set yourself out from the crowd.

Excelent poins Mat!

The idea of the "superstreet angle" came about when loading became a negative issue in large standard wall builds using more than two subs...ex: 4x 15" or 18" wall. the northAmerican auto makers have built their vehicles wider to accomodate passengers with more comfort, this is an advantage for spl competitors here over the european's because we can use larger cone area to create higher mass sound waves.

The big problem is as you said about testing everything... ive seen alot of ss 1-2 builds using the same angle while i have my doubts the individual competitor tested to find if they were actually gaining from this. Sometimes if your enclosure is too large, adding an angle will gain you but the thing to realize is you may have only gained from the removal of necessary volume from the enclosure. North american vehicles are much larger and to our advantage, there are bandpass enclosures much more efficient in spl especially for builds using much cone area. a badpass enclosure has 2 chambers. You can solve loading issues by having a large loading chamber vented into the cabin..and you can move the woofers to load in different various positions. These are some benefits available to us.

If you really want to see if angles and such are beneficial to you, calculate the volume of which the angle will remove, then remove that volume while maintaining the flat back wall.

Keep in mind that as your enclosure is more shallow, the quarter wave wont move as easily toward the vent and you may need to make adjustments to your sub baffle in order to see the gains.

Remember, this is spl were talking about...the same rules dont necessarily apply to musical systems in the same manner.

Umm...does this mean that only myself and Mat wish to share and discuss intricate spl theory's for the good of everyone on this forum? is there no'one else here that seeks the greater understanding to improve on their build? Common guys...even if you dont know the technical portion or if you have a theory which youd like to discuss but dont fully understand, post it up!!

i read this im not understanding what you mean by te "angle"? paint picture or something?

more or less the idea

im prety sure its the other way around! but that is the jyst of it. im sure if you imagine the way a wave forms from a sub, you will understand how "yes" this will aim the wave close to the port but will create a strange 'standing wave' on the side wall of the port. this will have odd effects on the front cabin spl.

You will see big numbers with this design usually if the cone area is large and the power is larger...this design is not nearly as efficient as a square box but is essential for using many large subs in a large vehicle without a bandpass enclosure.

To visualize a sound wave from a round speaker, think of a raindrop on water. The raindrop is light so its impact causes a tight ripple that expands evenly away from the center. Throw a stone in the water and you will see a wider ripple which will go on further before it weakens.

This is the same effect from a soundwave...high frequency's create a tighter and shorter wave (like the raindrop) and lower frequency makes a wider wave that travels further (like the stone)

As you add power to the woofer, waves will form. As you increase the power, the wave becomes more intense. How does this relates to your build? the size of cabin requires a certain frequency to allow pressure to form at the sensor, any obstructions IE: seats, dash etc..require the wave to reflect while maintaining velocity, and you control all this by the characteristics of your enclosure internally and the starting point for loading pressure to the atmosphere of the vehicle based on where obstructions are and how the waves can maintain velocity enroute to the windshield. WHAT A MOUTHFUL!

this was more referring to street class type setups so really hard to explain in detail. Walls are different because they dont need tricky loading positions to get around seating and such, walls are straight forward having mainly the dash and windshield working against them...the idea is basically having the right combination of cabin volume vs. box volume, proper ratio of power to box and port volume, and this is all in accordance with wavelength at a certian frequency that allows maximum pressure to be achieved at the focus point which is the sensor.
The perfect frequency is also dependant on the body of the vehicle. The vehicles resonance will either harmonize with the frequency you play, or it will work against it causing cancelation weakening the wave. Wall enclosed vehicles will have a high resonant frequency because the short distance from front baffle to sensor, and also because the vehicles structure is stiffened behind the b-pillar decreasing the amount of unsupported metal.

Great thread with solid info.

thats what i was thinking it was just wasnt to sure thanks!

yea, my bad man, it IS the other way, im retarded

Meh...you got the idea across!

So, who here wants do show a simple calculation to find relation between peak frequency and distance from enclosure to windshield?? This is one we all want to know!

^^^^ See, if I had a mic, I'd test all kinds of stuff like this.

so...buy one

yes.. buy one i wanna know how loud i am without leaving windsor! haha

a new termlab will cost about $800 shipped....I dont recomend buying used