I have been wanting to mess with the placement of my sub to see what I can improve. This is only the second position but is seems good. I measured using the rat shack meter. Mains crossed @ 80hz and playing along side the MFW. I found a DbDrag CD from my car audio days. So I tested 20-80 in 5hz increments, at -35. Everything was set to 75db with the rat shack. Here is what I came up with. Nothing is corrected by the way.

Hz DB
20 78
25 75
30 76
35 84
40 81
45 87
50 84
55 84
60 88
65 83
70 81
75 85
80 87

I would appreciate any opinions or tips on testing further to get the most out of my sub, which by the way is a B stock that is dead silent not even a faint hum couldn't have ask for anything better thus far. I have been itching bad to pick up a second

That in-room response looks really good. Did you use the Radio Shack meter correction table?

I didn't use the correction table. I checked it out but it showed corrections for only a few frequencies. Should I be testing at those frequencies instead of what I did? I could make a cd with tracks to match the tones on the correction table. I am still new to this home audio tweaking stuff and I want to learn as much as I can to get the most out of my setup

Try these correction values. I interpolated these for a 5 hz step from the existing references. Old is for the old analog meter, new is for the newer analog and digital meters. YMMV

Hz db New db Old
20 7.07 12.11
25 4.96 8.61
30 3.48 6.11
35 2.44 4.34
40 1.71 3.09
45 1.20 2.19
50 0.84 1.56
55 0.59 1.11
60 0.41 0.79
65 0.29 0.56
70 0.20 0.40
75 0.14 0.28
80 0 0

If you are using the new meter your response would look something like this.

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=130625&d=1232555570

Of course the measurement resolution is too coarse to pick up sharp peaks and nulls but it gives you an idea.

You're halfway to doing a REW run, and that would give you a lot more to work with.

http://www.hometheatershack.com/roomeq/

Thanks for that. So can I find that somewhere or is there some equation to calculator??

I just did a little number crunching with excel. It may exist elsewhere but I'm not aware of it. The REW suggestion is a good one. The only thing that keeps me from taking the leap is the lack of a line-in jack on my laptop. Eventually I'll quit dragging my feet and get a sound card.

I just did a little number crunching with excel. It may exist elsewhere but I'm not aware of it. The REW suggestion is a good one. The only thing that keeps me from taking the leap is the lack of a line-in jack on my laptop. Eventually I'll quit dragging my feet and get a sound card.

Drink the coolaid its fun:D, $50 or so and you are in the club.
Your wife will think its great trust me.

Drink the coolaid its fun:D, $50 or so and you are in the club.
Your wife will think its great trust me.

I'm considering taking a sip this weekend. I have an old pc I might dust off and drag downstairs. I'm also a little worried about what I might find. When my eyes confirm what my ears are already telling me then I'll be forced to take action:) That will be the point where the wife weighs in :eek:

I have a mic jack and headphone jack on my laptop that would work right?

I have a mic jack and headphone jack on my laptop that would work right?


No it won't. As I recall there is a difference in input level between mic and line in jacks. I haven't even cut my teeth yet so the best advice I can give is to read up at hometheatershack.com

I have read enough to know that most REW questions have already been answered over there so do a search before you post or you may get one of the blunt replies to do a search.

Not trying to give you one of those blunt replies, just a heads-up.

That in-room response looks really good. Did you use the Radio Shack meter correction table?

These correction tables keep showing up. I haven't checked in on a correction thread in over two years, but approximately 2 years ago, maybe more, I had multiple exchanges with Ethan (at realtraps.com, I think). A bunch of that discussion is somewhere on avsforum.

Anyway, search for it. I believe the conclusion at the time was that Ethan said the folks at real traps had compared the radio shack meter to their extremely expensive "good" equipment at the office, and found the correction meter stuff wasn't needed.

Once I saw a reply like that from a reputable source, I stopped worrying about the correction stuff. Like I said, maybe something has changed in 2 years, I haven't checked in on a correction thread since I got my answer. I also don't claim this is the definitive answer, but I figured a guy who worked with sound treatments probably knew his stuff when he compared the meters.

Your wife will think its great trust me.

Hahahaha this is one of the best things ever posted on AVS!

VERY NICE! :D

Just curious, how far away were you from the sub when you took those readings? Also, how big is your room?

About 10ft from the sub the room is 13' wide 21' long 8' high. 8' opening to the next room

These correction tables keep showing up. I haven't checked in on a correction thread in over two years, but approximately 2 years ago, maybe more, I had multiple exchanges with Ethan (at realtraps.com, I think). A bunch of that discussion is somewhere on avsforum.

Anyway, search for it. I believe the conclusion at the time was that Ethan said the folks at real traps had compared the radio shack meter to their extremely expensive "good" equipment at the office, and found the correction meter stuff wasn't needed.

Once I saw a reply like that from a reputable source, I stopped worrying about the correction stuff. Like I said, maybe something has changed in 2 years, I haven't checked in on a correction thread since I got my answer. I also don't claim this is the definitive answer, but I figured a guy who worked with sound treatments probably knew his stuff when he compared the meters.
Generally, above 30hz or so, the correction is not that large....but once you get lower than that, it is a big difference. I went to the realtraps site to read their position, and it says they measured starting at 600hz, but didn't say how low they went.

I agree with them when saying that not all RS meters are the same, but without a professional calibration, we are just trying to get as close as generally possible.

curtis....out of curiosity, my RS SPL meter (analog) is about 6-7 years old. Not knowing about the differences, do you know how far off they are? And, have they actually changed that much over the years?

I guess the real question is, would it benefit me in any way to buy a new one?

curtis....out of curiosity, my RS SPL meter (analog) is about 6-7 years old. Not knowing about the differences, do you know how far off they are? And, have they actually changed that much over the years?

I guess the real question is, would it benefit me in any way to buy a new one?

I have an analog one and supposedly they are still king!

I have an analog one and supposedly they are still king!

GOV.....how old is yours? I know these won't be "spot on". And, as best I can tell, they really haven't changed much over the years (if at all). Just wondering if their accuracy has somehow been improved over time.

curtis....out of curiosity, my RS SPL meter (analog) is about 6-7 years old. Not knowing about the differences, do you know how far off they are? And, have they actually changed that much over the years?

I guess the real question is, would it benefit me in any way to buy a new one?
The corrections values have supposedly changed since then...but I don't know what old ones are.

I have the older analog model, and a newer digital, but have not bothered to compare.

I don't trust measuring pure tones and writting down what the SPL meter says. I have tried this before and after measuring each speaker I had measured 80dB with my subs and a main over 10 times for 5Hz increments right after the meters range did not need corrections for one speaker and others were close also. Somethings not right with that.

I don't use the SPL meter as scripture. I do take measurements in 10 Hz increments up to about 100 Hz and make a mental note of peaks and valleys.

I'm not going to be spot on. But, I have been able to smooth out the response in my room by taking the measurements and adjusting accordingly.

Then, I tweak "by ear". It usually takes me a week or so of doing this before I get it "dialed in". Then, I just leave it alone, unless something major is changed in my room, or with my HT gear.

graphicguy...what do you do when making adjustments?

graphicguy...what do you do when making adjustments?

Curtis....I can make EQ adjustments in the MCACC of my AVR. Can't go below 63 Hz, though. The rest of the measurements I take are strictly to see what different placement works best and do level matching.

I also do some measuring using either 50Hz or 80Hz crossovers.
-Dan

Ever thought about EQing the sub?

GOV.....how old is yours? I know these won't be "spot on". And, as best I can tell, they really haven't changed much over the years (if at all). Just wondering if their accuracy has somehow been improved over time.


Mine is about 4-5 yrs old

Ever thought about EQing the sub?

Yeah....thought about it. But, that's about as far as I've taken it. Most of my "tweaking" has been old tech. Aside from what I can do in my AVR, I use the RS meter and start shoving the sub to different locations. Tedious, but after a while, I can get things seamless and sounding pretty good to my ears.

Right now I've got a garage full of some really nice wood that I was planning on building a separate custom gear rack.

That means I'll be shifting things around a lot....including the sub.

I'm procrastinating, though. Telling myself it's too cold to do any wood working.:o

But, I'm open to suggestions if you have any.

If you really want to tweak, the BFD is a cheap and effective way to go....also can be tedious. To be really effective though, you need something like Room EQ Wizard, which is free, but you need a decent soundcard and mic (RS meter will work).

Curtis....thanks.....is that strictly a windows application? I run an entire MAC house.....:D

Curtis....thanks.....is that strictly a windows application? I run an entire MAC house.....:D
There is a version for OS X as well.
http://www.hometheatershack.com/roomeq/

There is a version for OS X as well.
http://www.hometheatershack.com/roomeq/

Thanks a bunch, Curtis. When I finally decide to go that route, I'll jump on it.

BTW.....I know you love the Rythmic (very nice sub). Got a quick question for you on the MFW 15.

In planning custom cabinetry for my HT, one option is to have the MFW 15 on a side wall, about 1/2 way between the front soundstage and the listening area. I'm still deciding to whether to keep my L/R bookshelf Rocket RS250 Mk II (which I dearly love) with the much larger RS 850s to replace them. That would compress the amount of space I have in the front, however No room for the MFW). As a side note, I am looking at the Sierras, too. But, I'd run 6 of them to keep tonal consistency. Don't know what that would net me as compared to the RS 250s.

While I can point the driver directly at the main seating position, that would mean that the back of the MFW 15 is visible (pointing towards the front). I'd rather not do that. What I'd rather do is to point the sub out into the room. But, that would make it pointing perpendicular to the seating area.

Room is W: 18' X D: 22' X H: 10' Open at the back, but cut off by the main seating area.

Downsides? Thoughts?

All I can sat us try it and see if it works for you...I suspect it will be fine.

Generally, above 30hz or so, the correction is not that large....but once you get lower than that, it is a big difference. I went to the realtraps site to read their position, and it says they measured starting at 600hz, but didn't say how low they went.
.

Like I said, it was 2-3 years ago, so I don't recall the specifics. Thanks for the realtraps site info. I'm sure it would be helpful to know how low they went.