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Port compression and optimization


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I'm aware they aren't a hard cutoff but it's not like you need to use a 48 dB or 24db slope for the crossover.

Most likely I'll use a 6db or 12db slope for my system but that will be determined when I tune the system.

A little eq'ing helps too as you stated to get the curve you want.

But there's always a cost as you said.

That being said a lot of people's definition of "music" is a clipped 30 hz sine wave with some 80 IQ knuckle head grunting about committing crimes and his genitals.

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So you're saying that tuning at 20 or 50 doesn't make a difference in output below 80hz?

As already stated, above 80 Hz.

I hear so many times "I need to tune higher so I can get the higher bass".

More than likely the system has a large peak in the output just above tuning so that all that is heard is the peak, which gives the idea that the upper bass is missing. The proof here would be that upper frequencies do not roll off based on tuning frequency.

The correct idea would be to design a system that didn't have such a large peak in the response.

This is what I was getting at, so people could just tune to 20hz it shouldn't have an effect on output at 50hz compared to tuning at 35hz right?

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This is what I was getting at, so people could just tune to 20hz it shouldn't have an effect on output at 50hz compared to tuning at 35hz right?

Yeah within reason. If the example you gave 35 Hz is close enough to 50 Hz that you probably are going to see a difference vs a 20 Hz tuning.

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."

Builds:

U7qkMTL.jpg  LgPgE9w.jpg  Od2G3u1.jpg  xMyLoO1.jpg  9pAlXUK.jpg

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great read still!!!

Fidelity

Built to Last

Team Sound Asleep

24Runner Build Log: http://www.stevemeadedesigns.com/board/topic/196657-24runner-sleeper-system-lots-of-fi-neo-dd-focal-new-video-w-juicebox-lithium/

2 x 12" Fi BTL N2 / 2 x 12" Fi BTL N3

2 DD M3b

Maxwell 2.7V 3000F Supercapacitors

Pioneer DEH-80prs

Focal P165 V30 components

Rockford Fosgate T-400.4

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Is it not true that our ears can begin to localize sounds somewhere around 80hz - 100hz?

If that is true why would you ever want to have your sub covering frequencies up that high?

I cross mine at 63hz typically.

One way to get around this is to use an array of drivers at low frequencies. For instance, if you have four drivers covering the two octaves from 80-320hz, and those four drivers are in front *and* behind you, it's going to be difficult to localize where they're located.

I am using this trick in my current build; I have the subs running all the way to 200hz and I have six midbasses total. The midbasses are under the seats *and* under the dash and they're time aligned. (Don't bother doing this if you can't EQ and time align them; all the midbasses need to arrive simultaneously and have the same response.)

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With all of your testing ability, another fun project would be to build a nice flat enclosure (.707 Q) and look at impedance plots.

Then using the impedance plots, compare output at the lowest and highest impedance frequencies.

You could also do this with a driver in free air.

Would be nice to show everyone that just because a driver has an impedance spike at Fs, you may not be providing as much power at that frequency, but that doesn't mean you are getting a big dip in the output.

If you have a Fi driver, a nice free-air impedance plot would be cool too. Just so everyone can see the difference between DCR and impedance.

Current system:

1997 Blazer - (4) Customer Fi NEO subs with (8) American Bass Elite 2800.1s

Previous systems:

2000 Suburban - (4) BTL 15's and (4) IA 40.1's = 157.7 dB at 37 Hz.

1992 Astro Van - (6) BTL 15's and (6) IA 40.1's = 159.7 dB at 43 Hz.

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I just read this. Good stuff.

91 C350 Centurion conversion ( Four Door One Ton Bronco)

250A Alternator (Second Alternator Coming Soon)

G65 AGM Up Front  / Two G31 AGM in Back

Pioneer 80PRS

CT Sounds AT125.2 / CT Sounds 6.5 Strato Pro component Front Stage

CT Sounds AT125.2 / Lanzar Pro 8" coax w/compression horn tweeter Rear Fill

FSD 5000D 1/2 ohm (SoundQubed 7k Coming Soon)

Two HDS315 Four Qubes Each 34hz (Two HDC3.118 and New Box Coming Soon)

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