Resonant Frequency of a Nubira II

[Carr]

Does anyone know the resonant frequency of a standard Nubira II Sedan? I am going to be building a SPL box for my sub but don't have access to a meter to test what the frequency is.

Cheers
Chris

[PrecisionBoost]

Are you trying to determine the resonant frequency of the cabin to get a few extra Db of gain ?

Personally I think measurement is best.... even changes to the seat position can affect the outcome slightly.

If you can't find a meter you can use a microphone connected to an oscilicope and measure readings that ways.

I don't normally jump in on audio threads, but I use to compete.... and I use to design boxes and systems.... and I'm an electronics eng. tech..... and I was this close (holding my fingers 1/8" apart ) from starting my own car audio manufacturing business.

[Carr]

Damn Boost, is there anything you don't know. I always look forward to reading your posts as they are so informative and well explained.

I am looking at getting the most dB from my car as I can with a very small budget. As part of my effort to get the most from the car, I am trying to increase the resonant frequency as much as possible without going to a wall. I was hoping someone knew what the frequency was on their standard car as I have already sound deadened my entire boot, so mine will should be slightly higher than standard (from what I understand). I was hoping to see how much difference it made. I need to get a meter so I can spend a solid week or 2 doing some testing as to box and port position as well as size and tuning. I was thinking of getting a fairly cheap ($100) sound level meter to get me started as I don't have $1200 for a term lab. Even a fairly cheap oscilicope is a few hundred bucks plus a decent mic.

So far I have only spent about $1200 on my entire system and in my first comp hit 140dB in a box tuned to 38hz with a 52hz tone. I figure if I can do as many basic mods as I can to increase the res frequency and build an spl box to match, then I may get somewhere close to 145dB with only spending a couple of hundred dollars.

Any tips would be most apreciated

Cheers
Chris

[Big Jeff]

Damn Boost, is there anything you don't know. I always look forward to reading your posts as they are so informative and well explained.

well he doesn't get out much...JK

[PrecisionBoost]

Mainly I don't post into audio because I allready get a ton of PM's about car/engine questions... but given your question I figured you were serious about audio.

The Last time I competed I ran 144dB, but I don't tune my car specifically for SPL....and I don't measure cabin resonance with equipment.

I use a laptop to go through the tone range in question ( 30hz to 200hz ) and move the box around until I get the sound quality I like.

Sometimes I will scrap a box and build a new one if I don't like the sound.... quite often I have multiple box designs... not just one to give the exact sound reproduction I like.

That is to say I use my ear to detect changes in volume and quality rather than a meter.

max SPL quite often sounds like crap.... I'd rather tune for sound quality and then work on bringing up the SPL.

I like to use a combination of passive and active filters on the sub box to give the desired output.

That is to say I take the response of the subwoofer and create a filter to even out the response... giving a nearly flat response from 30hz to 200hz

I usually use the passive filter to give a general response tune then I relocated the active cross over to the front and play with it while sitting in the front seat.

The last active filter I had allowed me to change phase +/- 90 degrees and I can change the Q of the filters which allows you to make the best use of the cabin reflections.

By tuning it just right you can usually push well over 4 times the power rating of the subwoofer without damage.

For me... I tend to like to use ten to twelve 8" subs.... I have some older JL audio subs rated for 100W RMS but I can usually push 400W RMS without a problem and with minimal distortion.

I also prefer to use passive radiators over your standard ported style.... but that's just my personal preference.

I'm also a bit old school.... I think Class D amps are cheating..... I prefer Class A and nice Class A/B.

[jidasas]

I used to run a few Eight's in my lanos...it sounded quite good. I actually liked it more than my two twelves. The eights had a much clearer sound and better response. As far as db's, I got 115 with the eights and with the 12's I only get around 125 so it's not much difference. (that's tested with a cheap $89 sound meter) They also weren't overpowering the other sounds in the car.

Jimmy

[Carr]

I have only just been bitten by the SPL bug but about 5 years ago I had a Lanos with the same sub and amp which did about 143dB. I had to take the rear wiper off as it would come about an inch off the window when the bass hit.

I am in the research phase at the moment before I get too far into the build. I will probably be running 2 boxes, 1to use at comps for SPL, the other would be my everyday music box. I am still to decide what type of box I will build for SPL, this is where the research comes into it.

The amp I am currently using is a 4 channel A/B, the only reason I will move to a class D is when I upgrade my sub to a 4,000w one and need much more power.

Thanks for the input guys, I am interested in any ideas that you may have. If anyone has any idea how in raise my resonant frequency, I am very eager to hear from you.

Cheers
Chris

[PrecisionBoost]

I built a box where all the subs face each other towards the center and I managed some really big bass.

You can go with 4,6,8 subs ..... here is an example....

BOX.jpg

(13.3 KiB) Downloaded 324 times

You may have seen these before, because all subs fire at each other it allows you to push way more power into each subwoofer.

[wolfsreign]

im not that engrossed into sound and comps, as i LOVEEEEEEEEEEEE the bass to hit as fucking hard as possible. hahaha. idk why.. anyway... im running a rectangle box in my boot, with 1 12" fusion sub 400w max, i thinkkk its a DVC but im only using oneVC as my amp can only put out 300w bridged. lol, weak yes ill admit.. so that makes my sub 200w max.. yet i havent blown my sub but anyways im probably guessing also the box is not even close to being tuned right for the freq.. but my HU is 80hz and my amp is some where tuned to 70-90hz.. and the gain.. if you were to split a circle into that peace sign.. /\ the gain is only at - (like 1/5) and well.. it hits hard.. dB wise, no clue.. but what im saying is that.. if i had a choice now.. i would go with 4 8"'s in one box. using my same amp i would do 2 channel and hopefulllly wire them correctly for Ohm compatibility.
so what you experts talk about, i have no clue, but if you could rock my socks off, mad propssssss.