[ctviggen]

So, George, if you're using a 70 Hz high pass and a 140 Hz low pass, you have both the subs and the RM40s playing bass in the 70-140 range.  How is bass imaging with that?  (Yes, I know that people aren't supposed to image bass, but I've had troubles using a single sub because of imaging, which is why I don't use mine for stereo.)  Does the TACT take this into account and lower the output over that range? Where are your subs?  Are they still in the corners?  Have you moved your RM40s more into the room?  Why are you using such a high (10th order) crossover on the sub?

Personally, I'd like to move my RM40s into the room more (to lessen the reflections off the TV), and get two larger subs.  This would allow me to place the RM40s where I want for the best imaging, without worrying (too much) about low bass response.  I think my next upgrade is room treatment, then subs and amp, then TACT.

[zybar]

So, George, if you're using a 70 Hz high pass and a 140 Hz low pass, you have both the subs and the RM40s playing bass in the 70-140 range.  How is bass imaging with that?  (Yes, I know that people aren't supposed to image bass, but I've had troubles using a single sub because of imaging, which is why I don't use mine for stereo.)  Does the TACT take this into account and lower the output over that range? Where are your subs?  Are they still in the corners?  Have you moved your RM40s more into the room?  Wh ...

Bob,

Imaging is fantastic.

I am playing with different crossover settings and trying to figure out the best ones.  The Tact takes into account the crossover settings when figuring out the correction curves for each speaker/sub.

The RM 40's are now around 40 inches from the front wall (measured from the back of the speaker to the wall) and 45 inches from each side wall (measured to the center of the front face of the speaker).

The subs are actually into the room as well. They are 62" from the front wall (flush against each side wall).    So far, this placement has given me the best measurements (flat at 18Hz).

George

[ctviggen]

Interesting!  So, your subs are farther into the room than the RM40s?  That might work for me, as I could put both subs into the room a bit.  You sound like you've spent a while getting this all setup!

[John Casler]

Interesting!  So, your subs are farther into the room than the RM40s?  That might work for me, as I could put both subs into the room a bit.  You sound like you've spent a while getting this all setup!

Hi Bob,

Nothing to do with TACT, but yesterday I moved a pair of my LARGER subs out from the wall to now act as "stands" for my 626Rs.

While I haven't had a chance to measure responses or even play with moving the listening position, I noticed an immediate "deepening" of the bass frequencies.  I would guess 3-4 Hz at least.

I also still have another pair of LARGERs "on the front wall",  behind this.

Listening late last night for a few cuts, at very low levels of less than 60 db (I live in a condo) I was amazed    at the quality and quantity of low bass.

[zybar]

Big B,

Any thoughts why there is more output when the Larger subs are moved out of the corners?

Isn't the opposite supposed to happen?

George

[JoshK]

It is likely due more to room modes then corner reinforcement.  With them out you are probably getting less cancelation at the seating position.

[mac]

Anyone ever listen to a system with dipole woofers?  IME, depending on the room, they can make orders of magnitude improvements over what any electronic correction system is capable of.

[zybar]

It is likely due more to room modes then corner reinforcement.  With them out you are probably getting less cancelation at the seating position.

I am going to take some measurements at 1M from the sub to see how things differ from my seating position.

I have no doubt that the subs can produce a tremendous amount of bass at very high spl's.

George

[John Casler]

I wrote this, then took my daughter to the school bus, then posted when I sat back down only to see that others had already posted the same.

I'll leave it "as is" for whatever it is worth

Big B,

Any thoughts why there is more output when the Larger subs are moved out of the corners?

Isn't the opposite supposed to happen?

George

Hi George,

If I might add something.  

Corner loading subs, "does" increase perceived output by what is called "room gain".  This is simply a more efficient directing and containment of the pressure wave as if comes away from the woofer.  The boundaries direct the bass wave energy, so that more of it is "focused or directed" to the listening area.  Plus les of that energy can escape behind the woofer and it too is directed toward the listener, rather than being lost.

But,

It doesn't nessessarily change room modes or how the room responds frequency wise.  If your room dimensions cause specific frequencies to be cancelled, this will not change them.

Moving the sub into the room will normally reduce the room gain and may even change the specific listening position where one might hear or not hear certain frequencies, but it won't change that frequency specific "interaction" to the room dimensions. (just the spots where they occur)

I think the increased depth, I heard was due to "changing" the distance of the sub, from the "back" wall and thus changing the position where I could hear certain "uncancelled" frequencies.

It also "synchronized" the great bass of the 626R, with the depth of the LARGER and probably caused them to be more "in phase".

The second pair of LARGERs  firing still from the wall position likely also have an effect, but I haven't had a chance to figure out if it is good or bad yet.  I'll start by simply unplugging them and also facing them outward to see what effect they seem to have.

"THEN" it is "putty time".

At least that is how I understand it.

[ekovalsky]

You can determine whether a particular position of the sub will result in bass cancellation or reinforcement based on where it falls on an even (halves, quarters, eighths, etc) or odd (thirds, sixths, ninths, etc) grid of the listening room.  I've used this to help minimize bass cancellation which was a big problem for the RM-40's and RM-X in my rather small 14.5' x 17' room.

I did my room grid using CAD which makes it very fast and easy.  Doing it without CAD would be very tedious -- eyeballing measurements will not work, they must be exact, and the grids would have to be laid out with colored tape.  Hours of work, versus minutes with CAD  

This was tricky to do with the RM-X since there is significant bass output from the front firing woofer and passive radiator slot and also the side firing woofer.  Thanks to CAD I was able to find a position where both the front and side woofers lie very close to even grid intersections, while still getting adequate toe-in towards the listening position.  

My TacT RCS 2.2X just arrived

 

so now it's time to have some fun !

[ctviggen]

Isn't there a speaker setup article that dissusses this?

[jgubman]

There are some good white papers on the Harman Intl. site about loudspeaker placement.

I've found thes articles on number and placement of subwoofers very accurate in my room:
http://www.harman.com/wp/index.jsp?articleId=122
http://www.harman.com/wp/index.jsp?articleId=1003

[rkapadia@ROOP]

,
Nothing to do with TACT, but yesterday I moved a pair of my LARGER subs out from the wall to now act as "stands" for my 626Rs.

 Moving the sub into the room will normally reduce the room gain and may even change the specific listening position where one might hear or not hear certain frequencies, but it won't change that frequency specific "interaction" to the room dimensions. (just the spots where they occur)  

John - you're spot on re: frequency cancellations; unless you change room dimensions, there's really no clean way to change room peaks and nodes.  That being said; it's all about the sweet-spots of listening, so moving around can have a huge difference on perceived bass response.  

George - as always, use your own judgement, and if you have a friend, you should definitely move those bad boys around.  With some moving around, I was relatively flat (+/- 5db for <100Hz) to 14Hz in room 40x22x13 for the single HT row of 3 seats with a pair of Largers + the RM/X .

Also, now that you have that Tact, you may want to take off some of that foam.  I believe it was either Steve Deckert or the folks at Adire that measured response of similar egg-crate foam, but they found the response to be *extremely* non-linear.  Drop me an email, and I'll send you the PDF I have.