test tones, SPL's, eq's and such................... (1 Viewer)

[KevinW]

With my home theater budget stretched tighter than the head on a snare drum, I've been trying every tweak I come across with the hopes of squeezing every ounce of sound out of my system. My system currently consists of a Sony DE835 receiver, Sony 530 dvd, Def Tech ProCinema 100 speaker set, VCR, Sony T60 Tivo, and a 32" RCA tv (which I consider to be the weakest link and first piece to be upgraded). I'm saving for the Toshiba 42h81, which my local BB finally got in stock.

Anyway, I've been trying to make sense of the use of products such as the Rane and Beringer eq's, test tone cd's, my RS SPL, and such. I downloaded a couple of test tone generators and burned a cd with tones from 10-99hz in 1hz increments and a sweep from 20-20,000hz. I discovered that my sub bottoms out at about 24 or 25hz, with a fairly constant dB level down to about 32hz. But, I've known since first getting the sub that I've got some peaks in the 40-50hz range. At least that what my ears tell me.

I've read just about every post concerning this topic, but need some step-by-step directions on properly calibrating everything. Also, who's got the best price on the Rane and Beringer units? I could use the chart showing the proper adjustments to make using the RS SPL. Also, could someone drop a link to one of the computer programs that helps with this process.

Thanks in advance for any and all info.

Kevin

p.s. Can the eq on my receiver be of any real use? The sony's allow you to adjust the frequency at which you boost or lower the tone controls for the fronts, center and rears independently. Anyone using a sony and familiar with the eq?

 

[KrisK]

Kevin:

In trying to set up my SVS, I was amazed at how much difference the location of the sub can make to frequency response. I tried several locations in my room and was able to get a position with an overall flatter response. I would try playing around with that and other existing parameters on your sub (phase control ...) first, if you have not already tried it.

= Kris

 

[Wayne A. Pflughaupt]

Kevin,

Moving a sub around to find the best response is fine if you don’t have an equalizer – it will definitely make a difference. The downside is that you end up with response characteristics you can live with at the expense of extension and output.

Since you’re getting a parametric equalizer, you will get the best results by putting the sub in a corner, one with the longest uninterrupted wall length in each direction. Of course, you will have one or two response peaks, as you have already discovered, but the equalizer will take care of that. Then you will have it all: the lowest extension, the highest output, and the smoothest response.

There is really no reason to take 100 frequency readings, Kevin. Readings at 1/6 octave intervals will get the job done. Take readings at these frequencies and post them here, and I’ll tell you how to set the equalizer.

20

22/23 (either or both, unless you can do 22.5)

25

28

31

35/36 (either or both, unless you can do 35.5)

40

45

50

56

63

71

80

90

99

Happy Holidays,

Wayne A. Pflughaupt

 

[Kevin C Brown]

Kevin (!):
Here is the Radio Shack meter adjustments. I just put it in a spreadsheet, and then let Excel do all the correction after I get the real measurements with the test disc and the RS meter.
http://www.hometheaterforum.com/uub/...17-000048.html
Know where I found that post originally? Not HTF! But on the www.audioasylum.com FAQ portion of their web site!

 

[KevinW]

Perfect timing guys. The wife has been out of town all week and my daughter is staying with Grandma tonight, so I've got the house all to myself. A local music store rents PA equipment and they have the BFD. It's not an item they usually rent but since I'm looking to buy they're making an exception. If I decide to keep it my rental fee will just be part of the purchase price.

Thanks again guys!

p.s. Just for my clarification, using a room analyzer and mic or using test tones and an SPL will give the same results, the room analyzer just does it automatically, correct?

 

[KevinW]

Just realized that I don't have a clue how to connect the BFD, since I've never used one before. Suggestions?

 

[BruceD]

Kevin,

Connecting the BFD is done in the following way:

Go to Radio Shack and get the appropriate number of

"Mono 1/4" Jack Adapter" part#274-884. Mono 1/4" phono plugs are the input and output connectors on the BFD.

These are female RCA-to-male phono plug adapters designed to go on your standard IC cable. If you use both stereo channels of the BFD you will need 4 of these (2 for input 2 for output).

Then connect the BFD in the sub cable output signal path from your receiver or pre-pro as follows:

1) Receiver/pro SUB LINE-OUT -> BFD Left LINE-IN (w/adapter)

1a) if you used a Y RCA IC because sub requires L&R in;

SUB LINE-OUT Y cable -> BFD Right LINE-IN (w/adapter)

__________________________________________________ _____

2) BFD Left LINE-OUT (w/adapter)-> Sub Amp Left LINE-IN

2a) if you used a Y RCA IC because sub requires L&R in;

BFD Right LINE-OUT (w/adapter)-> Sub Amp Right LINE-IN

__________________________________________________ _____

As far as software measurement vs SPL meter and CD tones, results should be similiar.

Note: In order to properly capture room modes in your measurements, you need to use pure tones with frequency spacing of 1/3 to 1/6 octave spacing. This can also be dangerous for your speakers if left on too long (more than a few seconds). Also, warble tones (like the Stereophile disks) won't work correctly.

If you have the RS meter and availability of a PC you might try the free software ETF5 or SpectraPlus.

BruceD

 

[Kevin C Brown]

I use the test disc/Radio Shack meter approach. I can imagine that using the software on a PC is much faster, and a lot more automated. Probably more repeatible too.

 

[jacek p]

I am new to HT and I plan to do something similat to what Kevin is doing.

However, manufacturers of my speakers and sub warn that using test CD or tone generator may demage the drivers.

I actually did damage a tweeter once while having a computer generating high frequency tone (long, long time ago, using an Atari 8 bit machine

My question is how real this danger is and what precautions are needed. My receiver is rated 5x100w 0.7%THD and the speaker are rated up to 100W (except for 120W sub).

Thanks a lot,

 

[David Judah]

If you download the newest version of the Spectra Plus demo, it has Radio Shack SPL meter corrections built in. All you have to do is add it in the scaling menu.

I tried it both ways(SPL meter/test tones & Spectra Plus/test tones)and the RTA was definitely easier, faster, and more accurate.

It makes a big difference when you tame those peaks as many have mentioned. I am very pleased with the results I acheived in a relatively short amount of time.

Good Luck,

DJ

 

[KevinW]

Awesome guys! Thanks for the help.

 

[Wayne A. Pflughaupt]

Jacek,

However, manufacturers of my speakers and sub warn that using test CD or tone generator may damage the drivers.

The manufacturer is right, it can happen. The situation is, a typical program signal is complex and causes cone movement. This is true even of a tweeter, even though it isn’t visible to the eye. The cone movement is necessary to reproduce sound, but it also serves to cool the driver’s voice coil. With a steady test tone come movement is minimalized, and the voice coil can over heat. If it gets hot enough, it can melt the voice coil, and then the speaker is officially a paperweight.
However, you can avoid this unpleasantness with a little common sense.

• Don’t take your readings at 115dB.
• Don’t leave the test signal on for 30 minutes. 15-20 seconds is enough time to get a reading.

Happy Holidays,
Wayne A. Pflughaupt