nice! subscribed...

Hi and thanks.

As previously mentioned, I will soon embark on this same journey, so I am following your progress with interest.

At this point, I have a few questions:

1. If I understand correctly you located your speakers in the front corners to maximally "excite the room". Is that the generally accepted 1st step, vs approximating where your speakers are likely to ultimately go? Is the idea to get the maximum bass (by being in the corners) to see how the room responds and thus find your listening position? If so, I assume after you later locate your speakers, you will redo this to fine tune your listening position for the smoothest response from the actual speaker location. Is that the concept?

2. I note you did not do any phase testing of components, plugs, speakers. I've read that's a good idea, because if anything is out of phase it will impact what you just did.

3. Did you find "suckouts"/dips or only the modest peaks you described? From the sound of it (no pun intended) your room is unusually good with only those modest peaks.

4. From what I've read the Behringer DEQ2496 is handy to have for ongoing monitoring, however, I am wondering why you didn't use REW for mush more detailed readings/comparisons/charts, etc, etc, especially given that its free. This would also let you see time/phase info on the waterfall graph. In addition, just for curiosity you could looked at the whole spectrum and only done one measurement per location, since it uses sine sweeps and plots anything you want to see. (sorry if some of my terminology is off, I'm going from memory on somewhat foreign concepts).

Sorry to pepper you with questions and thanks

If you want to excite all the room modes, the woofer should be located in a tri-corner, rather than a bi-corner. Also, I would place the microphone at your specific sitting position ear height, because that's the relevant height. Rather than taking so many measurements, simply look at your RTA (slow, flat, 1/12 octave) and mark the smoothest response on your line while running pink noise.

Discovering optimum speaker placement will be more subjective in that, not only do you have room modes to deal with (likely, you'll no longer be contending with at least f1 & f2 axial nodes with your new speaker position), but also soundstage (speaker separation) and tonality (speaker toe-in) compromises. Eventually, you'll end up working down to fractions of an inch regarding placement of both speakers and listening positions by trusting your ears with familiar recordings. With final aiming of the speakers, use a laser pointer and measure its position on the rear wall. This will offer great accuracy for matching.

How does one test phase? I have one of the AIX calibration discs but it just allows you to listen to some pink noise out of phase. Then the same pink noise in phase. I haven't quite bridged the gap between what real music might sound like out of phase as opposed to pink noise. Is there a way to actually calibrate phase or is it just one of those things that are or aren't? I would think this is related to listening position (if not speaker placement as well)...if not forgive me for going off topic.

Please take anything I say with a mountain of salt, as I have only read, not done. Also remember my terminology may be off...

As I understand it, there are three types of phase to handle differently:

1) Components/wall sockets etc: This may be more accurately called "polarity". These can be tested with a multimeter and inexpensive receptacal tester. Here is a paste from a post on this...

"CORRECT AC POLARITY

June 17, 2009 — puristaudio

System set-up

"I wanted to talk about a tweak that costs little or nothing to do, while having the potential of paying big dividends in terms of sonic improvement. It involves a simple test (with some simple test equipment) that will allow you to determine if your equipment, and wall outlets, are “polarity correct”. Almost all of your audio equipment has a transformer in it that serves as a source of power for the circuits inside. Not all manufacturers hook up their transformers so as to minimize voltage leakage to the chassis, otherwise called the “chassis to ground potential”. One can measure this by purchasing some testing equipment. What you will be measuring is the amount of voltage running around in the chassis of your audio equipment. The preferred voltage is the lowest voltage, which will save you from making dreadful subjective decisions such as “which polarity is more tuneful and in touch with the musicality?” First thing you will need is a polarity testing plug which will set you back about $3.99. The second piece of test gear is a multimeter (VOM) which reads AC volts below 500; mine cost all of $45.00. The polarity testing plug can be purchased in almost any store that carries even the most meager line of home electronics. It’s a 3-prong plug with three little lights on the back. You take the plug and insert it into each of your wall outlets, and the lights on the back will tell you if your outlets are wired properly in the wall. Many outlets, even in new digs and mobile homes, have the positive and neutral taps wired in reverse and grounds are oftentimes left open. The polarity plug will let you properly assess the orientation of the outlets that you use and make any necessary adjustments. This is the first step toward proper polarity. The next thing to do is check the chassis voltage of your equipment. With your multimeter in hand proceed as directed. Each component to be tested must be totally isolated. Disconnect interconnects, antennas, power cords and grounds. If the component to be tested has a two prong directional cord, plug it in. If the component to be tested has a three prong cord, steal a “cheater plug” from wife’s mixer and use it to float (lift) the ground of the chosen piece of equipment. Set your multimeter to AC volts, connecting the probe to a true ground (I use a true earth ground consisting of an outdoor earth rod with a cable running from it into my listening room). You can also go to the ground connection of the outlet if you have three prong outlets, or you can run to a drain pipe as I had to in my bedroom. NEVER connect to a pipe carrying electrical wiring or anything flammable like natural gas, and NEVER connect to an antenna which can be struck by lightning. Connect the red probe to the chassis ground terminal if it is a preamp you are testing, or to a sheet metal screw on the chassis on almost everything else. With the screws you may have to scrape a little paint off the screw to make good contact. Good contact is essential to an accurate volt reading off the chassis. Now plug the component in and turn it on. If you haven’t been electrocuted, you should have a voltage reading on your meter. Write it down. Turn the component off and reverse the AC power cord in the wall outlet. With a cheater plug, the neutral side of the plug is usually wider than the hot side and reversing can be difficult. In the past I have taken a pair of metal snips and cut the neutral side down so that it will fit into the hot side of the outlet. Once the polarity is reversed, turn the component back on and make a second reading. Choose the power orientation that reads the lowest. (Note: Some equipment, especially power amplifiers, should be left off a few minutes before firing them back up with the AC polarity reversed.) Easy? And with some experience you’ll get to the point where you will be able to tell the proper AC orientation by simply listening to the equipment; the meter won’t be necessary. At that point you will have earned your golden ear. Some audiophiles, when reversing a power cord, choose to leave the ground open or floating, alleging that the system sounds better that way. In some cases it is true, but remember, by floating the ground you may be defeating the UL rating for the device and maybe even voiding the warranty, which could be disastrous if for some reason a fire results. Play it safe. YOU ARE DONE. The real trick here is to get each and every component in a system oriented properly. If your system has two components oriented wrong, the correction of one may not be enough to bring on earth shaking improvements – get the entire system right before passing judgment. Proper orientation makes one’s system generally sound fuller in the midrange and more dimensional in the lower midrange. Clarity and depth of image will increase in good ways. Look for less strident and cleaner highs also a lowering of the noise floor. If on the other hand you test everything and find all the plugs properly oriented already, you could consider the entire ordeal as time wasted, or, you might consider it an average day for an audio manufacturer. Just a note if your not comfortable dealing with AC then don’t try the above post."

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=1177

2) Speaker Phase: I have read, but did not fully digested how to determine if speakers are in correct phase(polarity).

3) Sub Phase: I am not well enough versed to give details on this, but I believe in general with subs there may be times when you want to reverse their phase (polarity)depending on the length of the wave of your dominant problematic low frequency room node. Some subs have a dial to adjust the phase incrementally, vs a full 180 degree change. Others will have to correct/elaborate on this...

Sorry for so many comments on your page!

If you haven't read this, you may find it useful. It describes specific measurment goals in tuning a room/system. He is a contributor on this site and provides design/tuning/measuring services professionally. I dont know him, but find his comments and website inteligent...

http://blog.acousticfrontiers.com/storage/AMS%20for%20Stereo%20List.%20Rms.pdf'>http://blog.acousticfrontiers.com/storage/AMS%20for%20Stereo%20List.%20Rms.pdf

Here is his introduction:

"ACOUSTIC MEASUREMENT STANDARDS FOR STEREO LISTENING ROOMS PUBLISHED

THURSDAY, OCTOBER 13, 2011 AT 8:36AM

Some of the many questions that can be found scattered across the internet and overheard in conversations amongst audiophiles today relate to room acoustic measurements:

What are the key measurements?

How do I interpret them?

What does good look like?

How do they relate to each other?

These questions arise from the recent availability of cheap and accurate 'consumer' acoustical measurement products like XTZ Room Analyzer, Room EQ Wizard and Dayton Audio Omnimic. Whist these packages allow you to measure your room they do not provide any guidance on how to interpret the results relative to the audiophile situation of two speakers in a room."

Here is his site:

http://blog.acousticfrontiers.com/

Thanks for that tip. I may plop them on the floor and re-measure again in 6" increments and compare them to my current results!

As for the mic height, I'll be using an adjustable height desk chair so I'll be able to get my ears to the height that I'm measuring at without issue.

I've read elsewhere about using pink noise, perhaps I'll try that out and compare as well.

The more I read the more I understand that it will ultimately be a compromise when it comes to bass, soundstage, and tone. Not being at that point yet, I think that will be the more enjoyable part!

Thanks for all of your thoughts and tips!

Bill

Glad to have someone else going along this path with me! To answer some of your questions in your first post:

1. Correct, I placed the speakers in the corners to excite the room modes. I haven't been able to find a "generally accepted 1st step" so far in my research. I got the idea from some of the seasoned acoustics veterans over on GearSlutz. It was the first time I read someone say "do this first" so I went with it as it seemed to make sense with regards to everything else I had been reading. Before that it drove me nuts like a sort of chicken or the egg type thing! Once I find the best spot with my current measurement tools I will remeasure, from top to bottom, the entire frequency spectrum from 40Hz to 20kHz. That is my concept...for now.

2. The only phase testing that I've done so far on the system is to play "Channel Phasing" track (2) from Stereophile's "Test CD 2". I realize it's probably not the most scientific thing but it's all I've got at the moment. I'm not sure I'm going to open up all of my components, including my iMac, to test their polarity. I may grab one of those electrical polarity testers that you plug in to test my outlets though.

3. I did find significant sickouts and peaks at other locations that I measured. For instance the front 1/3 of the room had peaks at 250Hz. As I got further back in the room (around the 1/2 way point) they measured high at 200Hz. The rear 1/3 of the room had significant nulls at 125Hz and 315Hz. In the very rear of the room the biggest nulls were at 250Hz.

4. REW keeps coming in up in many of the more current articles I read on acoustics. It seems to be a very well done software package. I'm in the process of trying to find out what other gear I'd need to invest in to make use of it though. It may end up being part of "Phase 2" where as this first phase, for me, is to use what I've got currently to see what I can come up with and learn things along the way. As I continue to research online and read the 1000+ pages of the two books I just got I'm sure there will be new approaches that I want to try in order to compare them to my current results.

Bill

Thanks for the AcousticFrontiers link! I'll be checking that out...now.

Bill

Task chairs are meant for medium duty use

and a perfect for home offices and small office

It should support you in any position you assume,

at any task your office job serves up. Anthropometrically,

a chair ought to be inclusiveLike Us on Facebook!

Follow Us on Twitter!Read the Chair Hero Blog!

Sign Up for Our Monthly Newsletter!Don't miss

a single special offer or exclusive coupon!

Sign Up to receive savings and updates.

ChairHero is you number one resource for

value-oriented office chairs. At ChairHero

you will find a wide selection of inexpensive

office chairs that will make your shopping

experience; simple, fast, and efficient.

Our mission is simple, to save innocent

customers from villainous office chair prices!

Task Chair

Bill,

I don't know what microphone you are using, but now that I see a photo of your testing procedure, I'm hoping it's an omni and suggest that you aim it straight up (at ear height) in order to capture the front/back and sides of the room effectively.

Thanks for the pointer! I wasn't sure how to aim it. It's a Behringer ECM8000 so yes, it is an omni.

I'm going to have another go with the REW software this weekend and hopefully post some screen captures of the results so I can start a plan of attack on treatments.

Bill