[musiclear]

OK....After a bit of messing around from the listening position both channels driven full frequency, with 1/6th octave smoothing here is where I am.  All and all, not to bad and it really it sounds good. Jazz, classical so far the bass strings sound real nice.  Male voices clear with a nice open sound stage I can hear into quite deep.  I'll probably play with the 35hz bump a bit.  Maybe pull the tuning frequency down a bit, but I think this is going to be pretty close to where this system goes.

I think I got caught up a little to much in what  the graphs look like rather than what it sounds like.

Maybe I'll play with additional subs at some point, or maybe consider some room treatment, but for now.  I am happy.  Maybe I'll finish that veneer now.

At 1 meter:




At listening position with both speakers playing:

[ricardojoa]

Why does it looks like there is alot of low end in your system?

[AJinFLA]

At lower frequencies, there's actually not a huge amount you can do with the speaker design itself, as the dispersion pattern "wants" to become omnidirectional.

Hi John,

I don't quite agree with this. Yes, it is true that, for example, a dipole won't exhibit true free field characteristic figure 8 response when placed on the floor in a bounded space. Also true, is that with enough time duration for room reflections, there will be "fill" in the null positions, with a steady state signal. However, music is not steady state, but impulsive in nature. Then there is the psycho-acoustics of what we actually hear. A great example of a better way to "see" the difference, is Eliases Bark Wavelet tests http://dl.dropboxusercontent.com/u/2400456/html/Elias_Pekonen/Dipole_vs_monopole_bass.html

And you're in the modal region, so the primary factor is location, location, location. While not the only factor, it's a big one.

Absolutely. But also remember, dipoles and cardioids can be rotated in location and thus will couple to modes differently, even in the same location.

Edit: I forgot to include cardioids anywhere above. They could be an interesting option to explore.

I'll post some in room responses in the Axpona thread this weekend. Zero "treatment" as usual. System utilizes both a dipole and monopole woofer system (independently amp/eq'd), with cardioid mixed mode operation, so all 3 are possible. Form the same position. Steady state responses are easier to interpret, so I'll stick with those.

cheers

AJ

[musiclear]

ricardojoa, I added a frequency plot in the post above to compare with listening position.  I believe I could lower the tuning frequency and it would bring that 35hz bump down a bit.  Also, and the original reason for the thread is there is some room interaction involved that increases the appearant volume at those frequencies.  It should be addressed, and this is a work in process, so that will be in the works. 

[musiclear]

AJinFLA  I see you are a fan of Dipoles.  Me too.  Thanks for pointing out some of those benifits.

[jimdgoulding]

How does your music SOUND, btw? 

[AJinFLA]

AJinFLA  I see you are a fan of Dipoles.

I'm not tied to any particular format, but I do have a personal preference for "multi" polar speakers, dipole being one such format. For bass in particular, yes I prefer some form of first order gradient, be it dipole or cardioid, at least above 50hz. Since, by my observations, "room" issues can be found up as high as 400 or 500hz, I do not find multiple monopoles and smooth steady state response only, to be a panacea either. At least not for stereo content.
YMMV

cheers,

AJ

[JohnR]

I tried some measurements with a speaker pointed to the wall and then next to it, the other speaker pointed into the room as usual. 
...

I'll have to scrap the idea of moving one of these woofers to the back of the cabinet and look for better ways of minimizing room artifacts.

Hi I would like to thank you for taking the time to do the experiment!

 

I mean, with eq, I have modified the peaks down so it really sounds pretty good, I just would rather not have to do that.

May I ask why not? I'm not onto page 2 of this thread yet (and I see AJ has jumped in, which will as always be interesting and educational) - but, if you accomplish the results you are after is there some reason to worry about how it was accomplished? On that note, you may find that looking at time-frequency (waterfall, delay plot) response curves might be the next step.

[JohnR]

I don't quite agree with this. Yes, it is true that, for example, a dipole won't exhibit true free field characteristic figure 8 response when placed on the floor in a bounded space. Also true, is that with enough time duration for room reflections, there will be "fill" in the null positions, with a steady state signal. However, music is not steady state, but impulsive in nature.

Hi AJ, actually I think we are in violent agreement I should have said something like "At lower frequencies, there's actually not a huge amount you can do with the speaker design itself short of going to a dipole (or cardioid) design."

Absolutely. But also remember, dipoles and cardioids can be rotated in location and thus will couple to modes differently, even in the same location.

Yes, I left that out Even so, you can't just rotate a dipole (or even cardioid) independently of its location.

I'll post some in room responses in the Axpona thread this weekend. Zero "treatment" as usual. System utilizes both a dipole and monopole woofer system (independently amp/eq'd), with cardioid mixed mode operation, so all 3 are possible. Form the same position. Steady state responses are easier to interpret, so I'll stick with those.

I look forward to that!

[musiclear]

JohnR,

A reason I would rather not have to EQ to fix room interactions at my listening position is that from what I understand, these modes happen at particular spots in the room and if I "fix" a problem with EQ at one listening position, then it will be broken somewhere else.

The idea is to create a system where room interaction is minimal everywhere so any "fixing" that happens in one listening position, won't disrupt another listening position to much.

If I were to make an assumption I would say that is part of the reason AJinFLA likes woofers that activate so much of the room.  From what I understand, this would even out large energy swings and frequency response over a larger area.

The result is a flatter frequency response in more seating areas.

The same can happen with adding radiation points with extra subs placed strategically around the room.

[JohnR]

You shouldn't make assumptions! Measure, then decide. No-one on a forum can tell you anything more useful than that.

[musiclear]

True words JohnR.  True words.

[musiclear]

AJ, did you post your build of the "Inspired by Orion" project any where?  I'd like to read through it if you did.

[Letitroll98]

He owns Soundfield Speakers.

[musiclear]

Oh,  Cool.  Thanks for the heads up.

[AJinFLA]

Hi AJ, actually I think we are in violent agreement I should have said something like "At lower frequencies, there's actually not a huge amount you can do with the speaker design itself short of going to a dipole (or cardioid) design."

Figured I had misread your intent.

Hi musiclear,
My record keeping from more than a decade ago, was less that stellar, sorry. Most of those files are long gone on old computers.

cheers,

AJ

[JLM]

My sound quality priorities:

1. Speaker (lots of flame producing ideas but I believe in point source mid/high frequencies, fewer drivers in the mains, distributed bass sources, and transmission lines)
2. Room (can't be poorly shaped like a cube/tube/L and can't be tiny)
3. Treatments (I call them room band-aids, if you need many, the speaker/room are sick)
4. EQ (as mentioned above only works for a single point in the room, easy to overdue, should be the last resort)

[Jim Griffin]

Robert E. Greene has some interesting thoughts on room/speaker interaction with his various reviews of loudspeakers for The  Absolute Sound. He has a website at:

www.regonaudio.com

See his tests and his comments on one speaker that he tested (McIntosh XRT28):

http://www.regonaudio.com/McIntosh%20Supplement.html

The XRT28 which is a line array which has symmetrical lines of mid range drivers on each side of the tweeter line.   The line array configuration mitigates the floor and ceiling bounce while the symmetrical configuration of the mids will lessen the sidewall reflections. 

My conclusion from Robert's discussion is that speaker design can reduce the floor, ceiling , and sidewall reflections.  Another thing to try, if you have room for a dipolar configuration, is to use the inherent benefits of a dipolar speaker and build a dipolar line array in the future. 

[Duke]

I would like to take a look at what might work to help get those nasty bumps out of our lower frequencies.

The idea is to talk strictly about things we can design into our speakers.  NOT to talk about room treatment. 

If smoothness of bass with good extension is the top priority, but you can only go with two main speakers (no swarming of subs), here's what I'd suggest:

Position your bass sources on your enclosure so that their distance from the room boundaries is as different as possible in all three dimensions.

So if you're using two woofers, maybe mount one on the front down by the floor, and the other on the rear up near the top of the cabinet, and then toe the speakers in.  If toeing-in isn't part of the design, offset the bottom woofer toward the inside edge, and the top woofer towards the outside edge.    If the enclosure design includes a port, maybe use a down-firing port in one of the enclosures, and an up-firing port in the other, or otherwise introduce asymmetry into the port locations.

The idea is to introduce as much de-correlation into the in-room bass energy as possible, because de-correlation results in a net smoothing-out of the response.

[musiclear]

Thanks for your input.  I am beginning to understand about multiple woofers or "Swarming" subs. That's a great term BTW. 

I was hoping to get where I wanted with my existing speakers, but after lot's of moving and listing, I am still hearing room artifacts that I would like to tame and question whether room treatments will do the job.  Maybe they will, but that would be a differant conversation.

If I were to start a swarm, what is the best way to determine how many subs and where to put them?

I'v seen classic positions talked about by others, but I am wondering if that might change depending on the room.

This is the room I am dealing with. It's 18' wide and 12' to the sloped ceiling.  12.5' to the couch and behind the couch is the kitchen with an additional 15' and then a family room off to the side.  It is a really big open area.