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nondirectional below 80hz?


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jmelton86 
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Posted: August 28, 2007 at 9:47 PM / IP Logged  

I'm upgrading my front stage. I've realized that with my tiny budget, I won't be able to get any decent midrange down to 32Hz, where my sub is low-passed at, so i'll need midbasses. I'm thinking i'll need either 2 8's or 2 10's in the rear to fill in from 32 to about 80Hz.

Is 80Hz and below the typical non-directional frequencies for most people or what? Could I go a bit higher, or if anything, will I need to go lower than 80Hz?

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Alpine Guy 
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Posted: August 28, 2007 at 10:08 PM / IP Logged  
Why is your sub cut off so low? Bring the sub up to 60 hz at least and bring the components down to 60hz, that should work well with quality speakers.
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jmelton86 
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Posted: August 28, 2007 at 10:16 PM / IP Logged  

My sub sounds great l/p'd at 32Hz. I have it tuned to about 30Hz, and I try to keep 'sub' bass frequencies to it. This is why I need midbasses.

I love midbass, and my budget for midranges is small, so i'll need midbasses to make up for them.

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stevdart 
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Posted: August 28, 2007 at 10:35 PM / IP Logged  

Sub bass freqs go to about 80 Hz.  You could probably make an argument for as low as 60 Hz, but not 32 Hz.  The point being:  what is a mid and where do you consider its lowest freq?  Keep in mind the gradual fall off slope of your mids which you will hear at two octaves below the crossover point, so always consider this large additional frequency band when deciding on crossover point.  You want the mids to perform without stress at these lowest audible freqs. 

Lower quality mids can't even be crossed at 80 Hz because of this, so something around 100 Hz or higher is chosen when that is the case.

Crossing another set of woofers with the sub at 32 Hz is the same as adding another pair of subs.

80 Hz is almost directional and its hard to pinpoint location below that.  Do some experimenting with your test tones and you'll know at what frequency you hear the sub bass all around instead of being able to locate the source.  The steepness of the LP crossover will have a lot to do with it, as well as any port noise that may occur in a sub setup.  Another source of higher freq noise, and one that a lot of people don't pay attention to when designing a vented enclosure, is the higher harmonic ringing that occurs if the port exhibits resonance within the sub range (including two octaves above the LP point.)   Natch, a sealed sub setup is easier to listen to for pinpointing the freq that localization begins to occur.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
DYohn 
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Posted: August 28, 2007 at 10:36 PM / IP Logged  

"Sub-bass" is the first two audible octaves, from 20Hz to 80Hz.   "Bass" is from 80Hz up to 240Hz.  "Mid-bass" is 240-400Hz.  What your system is missing is bass.  Most acoustic design theories use 80Hz as the beginning of directionality for the average human.  80Hz is the standard Xover frequency for subwoofers.  32Hz is very low indeed, much lower than I can normally recommend, but if it works for you, go for it - although if it was me, I'd change the Xover freq. up closer to 80Hz.

How much do you want to spend for your woofers?

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jmelton86 
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Posted: August 29, 2007 at 12:52 AM / IP Logged  

I've got a BostonAcoustics G51044 (dual 4ohm) and a GTR PR. I've got them in a 1.8 cubic ft. sealed box. It's being powered by about 300watts RMS. I've got the 'stage2' weight set in the GTR, in a .5 cubic ft box it'll tune the system to about 35Hz, so with my huge 1.8cubic ft box, and some 19-45Hz test tones, it sounds like it peaks at about 32Hz. The bass is great sounding to me. I love for it to go low.

The 2 6.5's and 2 6x9's i've got in the rear deck are l/p'd at about 160Hz and put off decent bass, but I know some 8's or 10's would do it better. I want to l/p them (8's or 10's) at about 80Hz so when I get my new front midranges I can h/p them at about 80Hz.

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DYohn 
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Posted: August 29, 2007 at 9:27 AM / IP Logged  
Like I said if you like it then fine, but you are not using your gear to its full potential.  Enjoy!
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jmelton86 
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Posted: August 30, 2007 at 10:10 PM / IP Logged  

So, I raised the lpf to about 40Hz on the sub. I feel it meets the 4 speakers in the back that are l/p'd at about 180Hz.

What my major question is, with the bass like this; Sub and PR l/p'd @ 40, the 2 -soon to be- 8's or 10's bandpassed at 40 and 80Hz (reason for 2 is to retain stereo sound from 40-80Hz), and my front midranges h/p'd @ about 80Hz, will it all sound ok?

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stevdart 
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Posted: August 30, 2007 at 10:33 PM / IP Logged  

You don't need to worry about stereo sound between 40 and 80 Hz.  It's omnidirectional below 80.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
jmelton86 
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Posted: August 30, 2007 at 10:45 PM / IP Logged  
stevdart wrote:

You don't need to worry about stereo sound between 40 and 80 Hz.  It's omnidirectional below 80.

Cool, so I could actually just get 1 8 or 10" for 40-80Hz and be good, right?

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Big3 in 1/0G
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