how to setup a sub for flatline response I have no experience

Ok I'm sure you all still remember the franken sub I'm thinking of creating. Though I've never had a real sub period let alone one with all the tweaker knobs adire has on there plate amps. I'm totally in the dark as to how I would properly setup it up in any given room. I've heard of using test tone cds and an spl (which I recently got) which I would feel would be best for me to learn to how to do seing as I've never really heard a stereo running at a good flat response. So it's not like I would be able to detect room gain peaks or loss by just my ear and I'm also under the impression it takes more than a good ear to do that anyway then again I could be wrong. I'm thinking I need to learn all this before I buy a sub so I may learn something that could affect my decesion once again EX: you guys said large subs are more difficult to setup esp in a small room. I've never seen one of these test cds for sale nor do I know what frequency range they cover as in do they also help dial in highs? I require a lesson and ya thanks for all the help you all have been given me I've learned alot here. -Mark

Hi Mark.

I see you liked my "Franken-sub" moniker...I think that's the right name for the beast you are planning to make :D

A test CD is pretty cheap and easy to solve...here's a great link to some test tones:
http://www.snapbug.ws/sinewaves/

these are in MP3 format, you may wish to use Nero or some software to convert them to standard cd files( WAV or whatever). Burn them onto a CD with titles if you can, and make a directory on paper for quick reference.

You don't need all of the tones.

A good link to read about improving bass response would be the following:
http://www.snapbug.ws/bfd.htm

It instructs you on use of the Behringer Feedback Destroyer, a Parametric Eq used to obtained flat sub responses. This should give you some good info to start with.

Huge subs in small rooms should work, but your room could (and likely will) limit performance. Smaller subs are usually recommended because they are a better fit.

I just rigged a BFD up to my system and posted my results in the HT forum the other day...
http://forums.audioreview.com/home-theater-video/bfd-plot-after-2-weekends-im-finally-getting-somewhere-12193.html
If you're going to build that sub of yours, you owe it to yourself to spend $100 on one of these.

You can detect room peaks and dips by ear, you just might not realize it because you don't have a flat response to reference to. Sometimes ignorance is bliss, not knowing what you are missing means you don't miss it. The tools just help you accurately quantify what you are hearing.

Kex,

I have a question about the sweeps on the site you mentioned. How would you tell what frequency it's at when playing a sweep ?

You can't. Instead, download the specific tones...
Some are sweeps, others are sine waves at fixed frequencies.

Quote:

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Originally Posted by kexodusc

You can't. Instead, download the specific tones...
Some are sweeps, others are sine waves at fixed frequencies.

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If you can't tell what frequency it's at then what purpose does it serve ?

Quote:

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Originally Posted by Selvyn

If you can't tell what frequency it's at then what purpose does it serve ?

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Selvyn, did you even look at the link?
There are over 100 individual test tones available for downloading,each one named after the individual frequency it plays.
So if you download the file 32Hz, it's a 32 Hz test tone...can't be much simpler than that.

I think he was wondering what the purpose of a sweep tone was?

Thanks noddin0ff - my bad...

Selvyn-
Sweeps are good for identifying troublesome areas and for seeing how well your sub integrates with your main speakers. It's a pretty fast way to demonstrate peaks and dips, but I use them only for integrating with main speakers and setting levels. I used them to help decide the cutoff point to set my receiver at. Trial and error. Maybe others have better uses for them.

Quote:

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Originally Posted by kexodusc

Thanks noddin0ff - my bad...

Selvyn-
Sweeps are good for identifying troublesome areas and for seeing how well your sub integrates with your main speakers. It's a pretty fast way to demonstrate peaks and dips, but I use them only for integrating with main speakers and setting levels. I used them to help decide the cutoff point to set my receiver at. Trial and error. Maybe others have better uses for them.

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Maybe I didn't express myself too well.

I'm quite familiar with sweeps and what they are meant for. I used to be very active a couple of decades back builiding my own amps and speakers. In those days I used to use a signal generator which could be set to sweep mode in conjunction with an oscilloscope to read the frequency. Using this combo I would chart the frequency response of a speaker.

I haven't done much in the recent past and I've kind of lost touch with what's available . I'm sure there must be dvds which give a readout of the frequency on a TV while using a sweep but I've never used one of these.

I thought you might have a way of actually reading out the frequency in conjunction with the sweeps on the link you posted. I see no use of a sweep where you are unable to see the frequency as well. Yes you would know there are bumps and dips, but what use is that info if you did not know at what frequency these bumps and dips occurred ?

Selvyn: I see your point, for identifying dips and peaks and their specific frequencies, you would use the sign waves and make sure the CD player display reads the file name (ie: frequency #) so you could determine the dips and peaks. That's how I do it.
Test DVD's I've seen don't give you enough control or time to really identify peaks or dips at certain frequencies, the sweeps move too fast and the individual tones are in too large of intervals to be of much use.