RE MT 18 decision?

[Goldtaz1 10+ year member]

Guys, I posted the following question on Termpro and I can't get a response. I am assuming it is because I am a noob on their forum. At any rate please help me out, here's the post:

I have done some testing in my car (I have a Mazda Protege' 5 hatchback) with a sealed enclosure and found that 47 Hz gave me the highest decibel readout, but I stopped going up in the frequency tones after 53 Hz because every frequency after 47 Hz received a lower Db score. Should I have kept going up to say 65-70 Hz just to make sure there was not another frequency that was louder? Also, I am going to be building only my second SPL enclosure ever and I was wondering if I should build a CRX box style enclosure or should I stick with a box that has the woofer firing at the back glass and the port firing at the back glass? I am using a single Resonant Engineering MT 18 and I was thinking to build an enclosure that was 10 cubes net with 200^2 inches of port. What are your recommendations?

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[Nikuk 5,000+ posts]

If You are building to compete, You should test all valid frequencies for Your organization (i.e.-dBDrag only records 20-80hz then You test up to 80hz).

-Nick

 

[Goldtaz1 10+ year member]

If You are building to compete, You should test all valid frequencies for Your organization (i.e.-dBDrag only records 20-80hz then You test up to 80hz).
-Nick

I guess I was kind of under the impression that most SPL organizations only recognize "true" bass frequencies (i.e. those frequencies that are 80 Hz and below)??? Anything over that usually sounds like a locomotive horn, not bass. Are you saying that my test was invalid because I didn't continue through the spectrum of frequencies?? Also, would you have any advice as to how I should place the subwoofer and port?

 

[psych0ticnemes1 5,000+ posts]

sub up, port facing rear...

 

[Nikuk 5,000+ posts]

I guess I was kind of under the impression that most SPL organizations only recognize "true" bass frequencies (i.e. those frequencies that are 80 Hz and below)??? Anything over that usually sounds like a locomotive horn, not bass. Are you saying that my test was invalid because I didn't continue through the spectrum of frequencies?? Also, would you have any advice as to how I should place the subwoofer and port?

What I am saying is: dBDrag measures from 20-80 hz for competition.

What I will point out now: My Trailblazer loves the upper ~48hz. But it also likes ~76 hz.

sub up, port facing rear...
You've heard wrong. No single style is loud in any given vehicle. Bandpass put me into the mid 150's legal in an '02 Trailblazer. A few "CRX" styles could only get me to 153.x with the same power.

Moral of competition = test.

1st things 1st... buy a TL setup & a cheap laptop with a spreadsheet program.

-Nick

 

[squeak9798 5,000+ posts]

Are you saying that my test was invalid because I didn't continue through the spectrum of frequencies??

Not invalid; just not complete.

What are you referencing your in-car measurements to?? You can't just sit a sealed box in a car and tune your box to the frequency that hit the highest score because you are not isolating the sub/enclosure peaks from the peaks actually caused by vehicle. Only way your testing will be worth a darn is if you do the exact same test in an open area, such as your yard (NOT a room in your house), and compare the two output levels. The frequency with the greatest difference between in-car and open space testing is where you want to have your SPL box peak.

Sorry if you already knew that........just sounded like you were going solely by the in-car measurements....which won't help you any by themselves.

 

[Nikuk 5,000+ posts]

...... The frequency with the greatest difference between in-car and open space testing is where you want to have your SPL box peak.
Sorry if you already knew that........just sounded like you were going solely by the in-car measurements....which won't help you any by themselves.

Then change subwoofers in the sealed enclosure and do it again, You'll notice a difference.

This method is good in theory, but does not play out very often in real app's.

If You use Your SPL driver in a 0.707 sealed enclosure and run a long sweep on the TL You'll be much better off... the software will simply show You the loudest recorded freq's. Work from there.

More often then not, the loud note will change as Your box changes to boot.

-Nick

 

[squeak9798 5,000+ posts]

Then change subwoofers in the sealed enclosure and do it again, You'll notice a difference.
This method is good in theory, but does not play out very often in real app's.

If You use Your SPL driver in a 0.707 sealed enclosure and run a long sweep on the TL You'll be much better off... the software will simply show You the loudest recorded freq's. Work from there.

More often then not, the loud note will change as Your box changes to boot.

-Nick

Then I'd skip all the sealed box BS and just do this: http://www.bladeice.com/resfreq.htm

 

[Nikuk 5,000+ posts]

Yea, read it, done it myself. Through 3 different vehicles I've found that the TL provided better results then in car measurments vs. open plane near field response.

$0.02.

-Nick

 

[Goldtaz1 10+ year member]

Thanks so much for all the help guys. While I have certainly been doing car audio for a while, I am rather new to getting something extremely loud. Hopefully I can take what I've learned here today and get some good numbers.