Some misc sub questions...

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
Ok, I've got a DIY Adire Tempest sub using the "Adire" alignment. I've been using it for a little while, but I never actually tuned my home theater properly.

Here are my questions...


First of all, in the manual for the "Rava" sub that Adire sells (and uses very similar parts to mine) it says:

"From your processor’s sub output, run an RCA cable to the RCA line inputs of Rava.

Additionally, if you need additional gain on the LFE channel, a simple “Y” jack to run the LFE input to both the left and right channels will give you a “free” 6 dB of gain." (page 5)

http://www.adireaudio.com/Files/RavaManual.PDF

Is this something I want to do? I love bass. Would it be worth it to get this extra 6 db of gain? (I've got the same amp that this sub contains).


Second, I'd like to figure out if my sub is actually performing as it should be. Adire has free files for "LspCAD" that...um...model the way the sub sounds.

http://www.adireaudio.com/miscellaneous/software.htm

So how do I go about taking these readings? I've got a digital SPL meter. I'm thinking that I should sit in my standard position and play a series of test files with the sub at different HZ and then record the data (I've already made a test CD). I'll combine the data to make a rough graph, and compare that to what I've gotten from the web. But then how loud do I play these test files in the first place? What do I set the gain and crossover to?


Viewing the Tempest files in that LspCAD program, there's a graph of "Half Space (2pi) SPL at 1m distance". What does that mean? Half Space? There's another graph of "SPL in room and cabinet". Can I assume that's what I'll hear in my listening position? (the in-room part). Newbie question: What is Impedence? I see it spike on this Tempest graph...


Thanks.


Jonny K.
 

Chris Tsutsui

Screenwriter
Joined
Feb 1, 2002
Messages
1,865
Additionally, if you need additional gain on the LFE channel, a simple “Y” jack to run the LFE input to both the left and right channels will give you a “free” 6 dB of gain."
This 6db of gain is the same as turning the gain knob on your amplifier up 6db. I don't believe the Y splitter will give you an additional 6db of maximum output/headroom.

To measure "your" response you could take your own measurements and compare them to LSP, but remember that they will be different. Rooms have a tremendous effect on the frequency response and there will be dips and peaks in various locations because of standing waves. The only thing people do about the effects a room has is try to "equalize" the subwoofer using parametric eqs that lower the volume at specific frequencies, or they use acoustical room treatments. Another thing to play with is the subwoofer location and listening position location.

I wouldn't stress about the graphs on adire and instead try and find a setup that sounds best (most lineal) in your own room because that's what matters eh?

Impedance is resistance the driver has. So like when the subwoofer is playing different frequencies it draws different amounts of power from the amplifier. An erratic impedance could result in messing up the sound because the amp has to keep changing the power it feeds to the driver. (It's nothing to worry about in your case, it's more of a designer's specification)
 

Jonny K

Second Unit
Joined
Dec 18, 2002
Messages
375
Oh, I've got another question...

When I've been measuring sound with my SPL meter, I find that when I've got trebel hitting high SPL values it's ear shattering, but bass doesn't hurt my ears at all. The other day I did a test and I had 110db of bass playing and I was loving it. Yet 110 db of trebel would have been horrid.

This is because the human ear is more sensitive to certain frequencies, correct? So then I've gotta ask, is 110db of bass damaging my ears just as badly as 110db of trebel would? (even though the bass doesn't hurt).


Thanks.


Jonny K.
 

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