Anyone actually used an RTA to tune your HT? (1 Viewer)

[Jared_B]

Real Time Analyzer usage is very popular in car audio. Just wondering why it isn't so popular with the home crowd.

It would seem to me that after calibrating sound levels for all speakers, the RTA would be invaluable in fine tuning - especially for sub interaction/cancellation issues. A

fter reading the "Two subs makes my system sing..." thread, I realized that most people are just guessing about crossover frequencies, sub cancellations, and the like.

Without an RTA, how does anyone know if there is frequency cancellation between their two subs in different locations?

Granted, you could just make it sound good to you - but not everyone has heard a perfect HT. I'm sure it would be much easier to get great results in any room with any configuration if an RTA was used.

Thoughts?

 

[Bob McElfresh]

Programs like Spectra and Seven Shades software packages have been used. But then you get into using your computer and buying a calibrated microphone only to find that you have 2-3 peaks in your room.
Then you buy a $125 Behring Feedback Destroyer to use as a parametric eqalizer to tame the peaks.
Then.... you sit around and admire the $250 worth of software and microphones that you may never use again, and the mess of your computer needing to be moved back into the study...
I wish I could run down to "United Rents" and rent a stand-alone RTA for a weekend. But for some reason, the local rental companies dont stock them. :frowning:
Some people have downloaded the freewhere program NCHTone which will create test-tone wave files. They burn them into a CD and using the Radio Shack SPL meter (with corrections) figure out where they have room-peaks and rolloffs.
This is usually enough to know where to setup the equalizer on the subwoofer cable.
Check the advanced fourm for "RTA" and Behring to see some of the posts. Some people even show nice before/after graphs of their room responses.

 

[BruceD]

I have to admit my purchase of the ETF5 acoustic analysis software package, the purchasing/building of a calibrated mic and mic-preamp (9V battery power), together with the use of my notebook (full-duplex sound card) has provided me with a wealth of knowledge about acoustics I could never have achieved just by reading.

It has also pointed out every deficiency in my placement of speakers, cabinets, coffee tables, couches, drapes, and listening positions. It has really enabled me to optimize my listening environment while correlating these changes with real acoustic principles. Plus I have saved my impulse and frequency graphs and can view them later for any modifications I want to make.

Nothing else really had as much impact on improving the sound in my room then this RTA setup. I just didn't use it once to get everything right, this has been an ongoing useful tool for the last 2 years.

 

[Bob McElfresh]

I didnt mean to disparage the idea of a RTA. There IS the cool factor of having a nice tool and the fun of learning.
guess I've been living with a household full of women for too long.

 

[Rick Radford]

Bob,
You been peeking at some of my "should I use RTA or manual charting" threads lately? You have been reading my mind!

Then.... you sit around and admire the $250 worth of software and microphones that you may never use again, and the mess of your computer needing to be moved back into the study...

 

[John Morris]

Bob: You paid for Spectra? I somehow downloaded a free copy of Spectra Plus for free...? Well, maybe it was a beta copy, but it was free.

 

[George Martin]

Jared_B

I work in car audio and I have brought the Audio control RTA meter home on several occasions. I use it to both calibrate the levels and then to set the EQ in my system to get rid of any peaks or valleys. I own a R/S anolog SPL meter but I feel the Audio Control is just a lot more accurate.

 

[Bob McElfresh]

For just the sub, I'd go with the SPL meter technique.

If I got really serious about acoustic treatments, placement, etc., then I could justify the price of setting up a nice little RTA system. It would be very nice to make a change, analize. Make another change, analize. There are a LOT of issues above 120 hz that would take too long with the SPL meter to chart.

At a local store that sells M&K THX speakers, they were telling me about a THX installer that came in with an RTA, but he also had an ARRAY of microphones so that the sounds could be sampled all around the primary listening position as he tuned/adjusted the speakers. Very cool, but way out of our league.

(Hummmm.. I wonder if the Guitar Center stors rent RTA equipment. I'll have to go check.

 

[Wayne A. Pflughaupt]

I set up my system full-range with AudioControl’s “pro-sumer” R-130 RTA and got excellent results from the high end to the mid-bass.

However, when I took individual low frequency readings for the subs I found that things were not as good as they “appeared” on the display.

The problem is that pink noise (which is typically what you use with RTAs) is a bit random, especially with lower frequencies. The display jumps around a lot making it a challenge to set up subs. Even with individual filtered pink noise test tones I couldn’t get a steady reading on the RTA or SPL meter. Luckily I have the digital Radio Shack SPL meter, so I was able to take time-lapsed averages.

RTAs are great, but if you’re using pink noise I recommend double-checking the subs with a sine-wave test disc and SPL meter.

By the way, Bob, your best bet for renting an RTA is at a pro-audio company. There should be no shortage of them in San Francisco. (Next bet would be a car stereo shop, but I doubt many will rent one.) However, it might be more cost-effective to just buy the ETF package.

Regards,

Wayne A. Pflughaupt

 

[BruceD]

ETF essentially eliminates the pink noise problem Wayne was talking about. It is why I selected it over other RTA-based systems.

The program produces a MLS test signal (Maximum Length Sequences) which is a special form of white noise. It then captures the room's response to that test signal during specific (selectable) time windows or gates that enable the program to eliminate or highlight specifics about speaker/room interaction.

The initial capture of the impulse response to the test signal can be used to create frequency graphs over and over again with different variables showing different specific speaker/room characteristics.

 

[Rick Radford]

Wayne,

According to Doug Plumb (ETF),

"You must use the ETF test signal CD with the ETF program. It is much better for this type of measurement than any test CD, in addition to this, a standard test CD will not work"

I had thought to use the Stryke test CD or a homebrew, but apparently this is not an option with ETF.

Regarding LF tests, Doug had this to say after I mentioned using a test CD:

"The best option is to use full duplex capability of your sound card and run cables from and to your computer in your office. THIS IS WHAT YOU SHOULD DO- especially for low frequency testing because ETF is very powerful for LF

testing using (record+play) full duplex sound cards."

Hope someone finds this helpful.

I'll say this, the customer service response from ETF is on par with SVS customer service. (And that says something to me.)

Now I just gotta find a way to work the s/w into the budget. I think it's too good to pass up. (I thought I'd only be out about $150 by using the BFD 1124p. Silly me.)

BruceD.. your input has also been invaluable. Thanks a lot!

 

[Greg Lee]

Having just completed a multi-day round of familiarization, experimenting, and finally getting my system set up using ETF and BFD, my answer to the question posed in the title of this thread is ABSOLUTELY. Regarding cost - I did purchase ETF, but had already made significant progress using the demo version - it was just a little more work and headache. I think you could do a fine job with the demo version.

Also, doing the testing is sooo easy if you do have a duplex sound card; if you don't already, I would recommend to buy one just for this.

With this setup, you can put the thing in Sequential mode, and about every 2 seconds, without touching any controls (on PC or HT system), get new graph showing the new situation resulting from moving the sub, moving the mic, or setting the EQ.

I frankly think there can be no comparison in terms of convenience and flexibility between using the RTA software and manual charting.

And as Wayne said, I can imagine myself using this stuff on an ongoing basis for experiments, tweaks, perhaps friends' systems, etc.

 

[Wayne A. Pflughaupt]

Bruce, Rick, Greg,

I was of course referring to a stand-alone RTA. Great info, though, thanks for all of it.

That said, it’s obviously hard to beat a software RTA package – with their price and function capabilities they’ve made stand-alone units virtually obsolete.

What are the prospects with ETF and a laptop? (That’s the only way I’d get a software package, since if I use my RTA it’s typically off-site.) What is a “duplex” sound card?

Regards,

Wayne A. Pflughaupt

 

[BruceD]

Wayne,

I think it depends on the laptop. Even though mine is a fairly old Hitachi, it was marketed as a multimedia notebook. So it has full-duplex stereo sound capability.

I think the prospects are probably pretty good these days as battery time and CPU speed has gone up. Mine is only a 150Hz Pentium.

Full-duplex just means playing and recording at the same time (simultaneously), rather than half-duplex which can only do one at a time. Like today's phone versus a walky talky.