Newbie-where to go next

[pscm]

Newbie with a couple of other posts. Looking for advise on a couple of fronts which I will explain below. Didn't have much information in first two posts so here we go.

See attached for room information. The room consist of concrete floor with carpet, one wall is concrete and entire room is studded with insulation. Ceiling is a drop ceiling with standard tiles. The room is fairly naked with the exception of one small record bookcase and bass traps. Doors have an acoustic mat but admittedly thin. I did this to the doors and added DIY bass traps blindly. The traps are6 inches deep with acoustic insulation inside. Speakers are currently set dimensionally for decent imaging.

Sound system is 2 channel speakers which are the 2 way ported Zaph ZRT's that I built. Note that I went with recommended build port length for 30 hz and have not tried tuning (due to lack of knowledge) nor anything related to resister changes for tweeter. Running a Schiit Freya and Mono Schiit Vidar's. Primary listening is Vinyl.

Measuring done using minidsp UMIK=1, laptop and mic to rca adapter plug using laptop soundcard.

I have included image of some test results last night. I did remove some of the measurement graphs to clean up the graph which is set at 1/3 smoothing. Other measurements not viewed on this image were pretty consistent with what you see. Now I am not sure I have things set up correctly although was disappointed with the results of the included measurement in which I removed the traps.

A couple of items I question is my setup based on graph results compared to what I have been studying online. On my graph I don't notice the steep climb from 10 hz until response is captured.as viewed many times on tutorials. Is my measurement results abnormal? I also question this as looking at the waterfall my results look very different. Many very thin lines next to each other.

If I understand correctly I have a mode between 50 and 60 hertz, another around 175 hz and yet another around around 600. Very open to any input on what I might try from any front.

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[pscm]

Also, image of room for visual representation of the outcrop

 

[FargateOne]

Before to go further, may I suggest to attach .mdat file of your measurements. It will help the real one here to comment your results. Also, if not already done, read a couple of guide suggested in the first sticky thread of this forumI recommand AustinJerry and Dandan to show standard graphs. For instance, 1/3 smoothing always show good looking response...but reality is more acurate with varsmoothing specially for low end FR. Many suggest to put the mic upward instead of horizontally with the appropriate cal file loaded.

 

[pscm]

Attached file. Also, yesterday i started moving around speakers and taking measurements. When I move speakers closer to front wall, the 45-60hz drop seemed to lessen but as soon as I moved the chair up to get best imaging the drop came right back. Also for fun, generated a 45hz tone from each speaker one at a time and walked around the room. Sure enough the tone almost disappeared when to the right of the chair (facing forward) at the chair distance. I can only assume this is a problem area?

 

[sm52]

I can only assume this is a problem area?

The place of the standing wave. On the right is more pronounced.

 

[pscm]

Moved speakers back 3 ft to within 2 feet of front wall and also moved listening position the same amount. Seems to addressed the lower frequency issue although introduced some drop in other area's although the trade off is favorable I think. Played around a bit with some futon cushions to see if I could notice any changes by moving around a bit. Not so much. It is nice to be able to see the difference in changes however.

 

[sm52]

Still need to try. Maybe something in between these options. The bass is better, but the mids and highs are worse.

 

[pscm]

Agree. Thinking i will start with movements of around 6" to see if we can find a happy medium. Had played around a bit with moving speaker angles but didn't really notice much of a change. Am finding that it takes some patience and moving around of just not the speakers but the seat as well but doing them individually to understand the changes.

 

[DanDan]

You can get rough information quicker using the RTA zoomed to LF plus Pink Noise PN. Do try the speakers pretty much touching the Front Wall. 6" is quite a big increment. When you get close to the end goal, 2" could be better.

 

[pscm]

Thanks for the information. Ran out of battery on the lasp top tonight and wart causes way to much interference. Also got frustrated trying some different positions. Haven't experimented with RTA yet and PN. Will educate myself and go from there

 

[pscm]

So as I continue to try and educate myself and run more testing, I have more questions....imagine that. I decided to run future tests with the mic turned to vertical and changed to the appropriate calibration file. I have attached my latest file as well as a waterfall graph. I have been concentrating on education of the waterfall. Based on what I am seeing it would seem that the decay time is way to long if I am understanding this correctly. I may have asked some of the following questions before although would appreciate any responses/help:
-Is it expected to see the db output between the speakers to be different? If not could a tube in my preamp or my preamp in general have a gain difference between channels?
-Seems as if my high end frequencies are dropping off. When looking on the test on the Zaph site, I didn't notice this although tests being done is by someone far more knowledgeable than myself.
-With a room of this size how much improvement could I expect to see if I placed around 8 qty 2X4 acoustic panels and worked on the ceiling tile area especially over the listening area?
-What other information could I provide that would be helpful?

 

[John Mulcahy]

Based on what I am seeing it would seem that the decay time is way to long if I am understanding this correctly.

No, the decay times are fine. The stuff at the bottom of the waterfall graph is just noise, decays start at the top. Here is an example of a response that has a couple of long decays:

 

[DanDan]

Some guides to REW and acoustic measurement

AustinJerry's guide has good coverage of using USB microphones.

www.avnirvana.com

The REW Manual is really succinct, a fab piece of writing, making complex physics easy on the head.

 

[pscm]

Good stuff. Thanks for guide link. Have been reading the help info and slowly starting to understand.

 

[DanDan]

Your are welcome. Happy New Year.