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Audio Test Gear - What do you use and are you satisfied w/ the performance? (1 Viewer)

Phaseshift

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I am curious as to what test and measurement gear that you all use for setup and equalization of your systems. I was asked by someone to do a review of some of the prevalent hand held units and compare them in a real world, but controlled environment to the measurements taken by lab equipment. I am not confident that I have a handle on all the brands out there and need to ask your help in filling in the names and maybe your comments on functionality / perceived accuracy. Even better if any of you have calibration or gauge R&R experience and have ever done a study that you would be willing to share with the rest of us.

The units I am aware of are as follows-

PC/RTA, Galaxy, NTI, Goldline, Phonic, Radio Shack, Gabriel, TerraSonde – Others??

The plan is to test them in a theater environment conforming to IEC268-13 to see how they stack up against the more common lab grade gear. The test will likely be a shootout of 3 or 4 of the more popular units vs a couple of the high end lab pieces and one QA based acoustic measurement system. (AP-2/DSP, SoundCheck and ClioQC-8. Maybe MLSA and LMS for comparisons, but they were not in the scope of the docs, if we do, it will be for the fun of it. I know that LMS will perform the worst of the group with the sine swept and the others using MLS testing will be similar. Mics will come into play, so we will use GRAS microphones calibrated with a GRAS pistonphone between every test. I am betting that the handheld equipment will have good repeatability with the downside being calibration and absolute measurement, mainly due to calibration. As a side note, we will likely do comparison testing in the anechoic environment as well to get a baseline on overall sensitivity and to weed out any potential issues before they can contaminate the data pool.

The idea here is not to shoot holes in the hand-held equipment. In fact, I believe that the results will show that handhelds are reasonably good for relative measurements; in the case of a system setup, relative measurement is what you are really looking for in most cases- getting your levels set correctly and making sure that you do not have a blaring peak or dip in your response at a particular setup position.

Where I believe the handhelds will be weak is in resolution and reference accuracy. Of course, this is about as profound as saying that comparing a mid 80’s pickup to a new luxury sedan from Europe’s finest will show significant differences in ride quality and interior sound levels. ;)

Any input from the forum?
 

Bob McElfresh

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Hi Phill. Welcome to HTF! :)

If you want, I can move your post to the "Speakers" fourm where more people who do RTA and configure "house curves" hang out.

Most of us use the common-as-dirt Radio Shack analog SPL meter. There ARE adjustment tables to try to bring it to standards - but ... level adjustment is kind of like using a stick to make fence posts the same height. We dont care if the stick is 7 ft or 7.3123 ft as long as the same stick is used for all measurements.

The big issue to hand-helds RTA systems is how quick and easy are they to sample from multiple seating positions. Anyone can measure/equalize/measure/.. for the primary seating position. Then you have to ping-pong to the other seats.

The subwoofer frequencies are also an issue. It's very easy to swing many DB by moving the measuring device a foot or two. Any hand-held device that works well for subwoofer RTA would be of interest.

Let us know how things work.
 

Phaseshift

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Thanks for moving this to where I would get some action- I am a noob. ;)

The comment that Bob makes about stick height not being right on 7 feet for measuring fence posts is a good one; a prefect example of absolute (reference) measurement vs. relative measurement. IN the case of using a hand-held SPL meter or RTA is more like using the stick to get a relative measurement. One thing I am going to be looking for is which "stick" is the same length for every measurement. People are often surprised to find out how much an audio measurement can change from one test to another, even without moving the microphone or changing the room arrangement.

Yes, setting up a room with an RTA (or any measurement system for that matter) can be a challenge, particularly when you are trying to make every seat in the house sound the same. Frankly speaking, a person can EQ the room to death and make every seat sound worse but the room “looks” better on the RTA or whatever analysis you are doing. I believe that a lot of folks overlook the concept of prioritizing the listening positions and worry too much about what they perceive to be an issue because they are looking at a peak of valley on an RTA in a particular position. My opinion is that if you have a seat with a big peak, look at the proximity to a major boundary such as the wall of a large piece of furniture with a lot of right angles. Then listen to several different program sources played _un-equalized_ through the system and ask yourself “can I really hear a problem??” A lot of cases you can not or the perception is that the seat may not be the ideal, but it is where your mother-in-law’s pooch will be sleeping anyhow. ;)

If the issue is happening in your primary seating positions, I suggest changing the room more than the EQ settings- for instance, your bigger issues are typically going to be in the lower end of the spectrum; some you can work on, some you can not without involving a contractor and a lot of $$$. First of all, kludge your speaker positions a bit- this is often going to result in significant changes in the overall room response and character. Not only speaker to wall distance, but angle to the listening position and separation distance. Another good trick is to move the sub around a bit. Here is one that is easy to try different locations and note significant changes in the room. Obviously you have cosmetic concerns and the all important WAF to consider, but in general, you can move stuff around enough to make more of a livable difference in the seat to seat voicing of a room than you can get out of dramatic EQ changes.
 

Kevin C Brown

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Yes. :) Repeatability.

Phil- I'd also be curious if you already have a bias. :) I have used the Radio Shack meter for years, and in the past few, I added ETF5 software with my PC and the Radio Shack meter. I am quite pleased with the characterization that I *seem* to get.

But ... every now and then I come across a person who has spent loads of money on a calibrated mike, who then says, the RS meter is garbage.

I say, the Radio Shack meter is "good enough". But I've never been able to back that statement up with a lot of facts. Just my feeling based on how I uses it, and the data that I get out of it.

Also, be careful in that I have come across at least two different sets of "adjustment" factors on the web (for low freqs). They aren't all that different, but one set seems to be quoted a lot more than the other.

And then I think there's a new company out with a very similar design to the Radio Shack meter:

http://www.topdjgear.com/atislprsolem.html

I emailed them once thinking that hey, if it's been improved, I'd want one, but I never heard anything back about new cal factors.

Also, there are a few web sites out there with mods to the Radio Shack meter that supposedly improves it's low freq handling (capacitors and stuff).

Anyway, I'll definitely be a person interested in what you're doing!
 

Wayne A. Pflughaupt

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Hate to rain on your parade, Phil, but I don’t think may of us use hand-held or hardware RTAs anymore (I myself would be one exception, having an AudioControl RTA). Generally, that market has shifted to software packages like TrueRTA, ETF and Room EQ Wizard. They’re cheaper than hardware units, and much more powerful to boot.

Regards,
Wayne
 

Phaseshift

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Kevin- I do not have a bias except that I do not anticipate fantastic results in terms of the calibrated accuracy, but hey, we are talking about low cost stuff and in most cases, it is used as a relative measurement device.

We do have some of the NTI hand held analyzers at the office, but I am not all that hot on them except for the very basic stuff. Once you get accustomed to having powerful computers and high-end test platforms with tracking filters, RTA just does not blow your skirt up that far. ;)

Wayne- Not raining on my parade. A client asked us to do the study for them. I believe because they have some marketing nutcase who believes that the low cost stuff is near lab grade in terms of reference measurement. Actually, we are going to be testing more than one of each unit and trying to get a baseline on the unit to unit accuracy. I do have a bias there- I bet that they will be 2, maybe 3 dB variance between the cheaper stuff and maybe 2 dB on the better stuff. Evidently the situation is that someone thinks that the hand held stuff will be repeatable and accurate to like .2 dB which is just not going ot happen. It is tough to get an insanely constructed test box and high end software repeatable to .2dB (worst case) in good conditions…. A hand held using pink noise in a room for frequency data or absolutes just isn’t going to be in that league.


My opinion is that with a typical SPL meter, you can get your room to where it needs to be. If you have access to high end software and good mics, even better, but not necessarily essential. At the end of the day, the ears and your personal tastes are where it is anyhow.

Any links to places that sell the common analysis stuff? I know True RTA and have seen PC-RTA but the others are new to me.
 

Wayne A. Pflughaupt

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ETF seems to have done a vanishing act - can’t help you there. REW is a free download you can get here. You’ll first have to register at the Home Theater Shack Forum.

It’ll be interesting to see how your study turns out. Keep us posted!

Regards,
Wayne A. Pflughaupt
 

Kevin C Brown

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ETF is here:

http://www.etfacoustic.com/

Phil- "Calibrated accuracy" ... 37.5 Hz is 37.5 Hz for example? Or 82.37 dB is 82.37 dB? Or both? :) As far as dB's, that's where relativity comes in, and even for freq, for a person looking at their room, maybe not so important if the RS meter is off as long as it's consistently off.

Precision, accuracy, and repeatability. Freq and dB's. And then linearity (?), right? What happens at low volume settings vs loud?
 

Phaseshift

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Phil
Thanks for the link-

Yes, looking at pretty well the whole range there. And yes, the point is to see how accurate and mainly how repeatable the devices are from measurement to measurement.
 

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