Ah I was using Log sweep for some but figured the MLS was better. Sounds like I have to use the methods I was using previously to look at integrating the subs best. I will take new measurements then.
There may be some odd reflections in the response, I have a lot of crap in the room still. There are some boxes with all my DVD's in them sitting on the floor off to the side of the speakers, and they could add odd issues. I can place all my acoustic panels together on the floor and side wall for just one speaker and see if I can't get a better measurement.
There may be some odd reflections in the response, I have a lot of crap in the room still. There are some boxes with all my DVD's in them sitting on the floor off to the side of the speakers, and they could add odd issues. I can place all my acoustic panels together on the floor and side wall for just one speaker and see if I can't get a better measurement.
Ok here are measurements with the log sweep method. There don't appear to be any built in averaging functions, but I took 6 measurements around each seat of importance. I then exported the files, averaged those within each seat, and then brought them back in to look at. I have one pre measurement for the main seat, and one post. The pre isn't really fully pre tweaking, as I had already started to move things around. None the less, the Pre measurement is with the room still having some boxes in it, no curtains, and the acoustic panels in another room. The Post measurement is with the room mostly cleaned up, a large thick upholstery fabric bolt unrolled and hung on the wall over the windows. The acoustic Panels hung up in temporary positions, and towels/blankets set up on the floor. There is also maybe an hours worth of eqing work, but I'm not fully happy with it. I like to make my adjustments very slowly. I change one thing at a time, then measure, change another thing, measure. Sometimes I will change something, measure, change it back, measure, change it again and measure, etc. This is because I'm still getting a feel for both general functioning of the filters, and how they work specifically with the Behringer. My DSP card isn't hooked in at the moment, but will eventually replace the Behringer and offer additional functionality and resolution, I hope.
Dr. Geddes, if you do get a chance to look at these and can glean anything from them, that would be great.
Oops just realized, the pics are in reverse order. The first is the post, the second is pre. Should be obvious since the first is much smoother. Look at the difference in the impulse response.
Dr. Geddes, if you do get a chance to look at these and can glean anything from them, that would be great.
Oops just realized, the pics are in reverse order. The first is the post, the second is pre. Should be obvious since the first is much smoother. Look at the difference in the impulse response.
Attachments
Yea Matt, those are not very good measurements. If I get a chance I will post what they should look like. I have at least 40 sets of Abbey data, and so I know what to expect. The impulse should ring maybe a half cycle or one at most and then go dead flat. Yours have lots and lots of extraneous "noise" or diffraction or reflections or whatever, but the data is contaminated to the point that its not going to be very usefull.
I didn't think so either.
Just to make sure everything is clear. This is taken at the listening position, so around 4 meters. The room, as mentioned, isn't a great room yet. It has all hardwood floors, so its very reflective.
Diffraction sources is certainly possible. It's not a dedicated room so nothing is built in. There are dvd racks, cd racks, the audio rack, subwoofers, etc all potentially acting as diffraction sources. I did my best to reduce these, but towls and blankets are a far cry from proper acoustic treatments. A lot of that will have to wait until I get more settles. I will need to buy some of the necessary things, so that is why I'm taking the time to do this now. I need to figure out what to get to fix these problems (such as the area rug and pad).
Just to make sure everything is clear. This is taken at the listening position, so around 4 meters. The room, as mentioned, isn't a great room yet. It has all hardwood floors, so its very reflective.
Diffraction sources is certainly possible. It's not a dedicated room so nothing is built in. There are dvd racks, cd racks, the audio rack, subwoofers, etc all potentially acting as diffraction sources. I did my best to reduce these, but towls and blankets are a far cry from proper acoustic treatments. A lot of that will have to wait until I get more settles. I will need to buy some of the necessary things, so that is why I'm taking the time to do this now. I need to figure out what to get to fix these problems (such as the area rug and pad).
If anyone in the Portland area would like to hear a pair of Summas, I may be doing a demo on Saturday. Trying to see if there's any interest. I'll also have my "take" on a Danley TH-Mini and something like a Danley Tower of Power on hand. Email me if you're interested. I demo'd the Summas in Seattle last year, but you really have to hear them with the tapped horns to get the full effect.
I demo'd them at a DIY audio show in Seattle last Summer. While they sounded good, they really need subs. I enjoy them a lot more when that last octave is there.
Also, it looks like we'll have three or four people on Saturday, around noon. I live about 15 minutes south of Portland Oregon, if anyone's interested.
Could someone please comment on an idea I have for speaker placement. Taking a large wedge style absorbent corner bass trap, and sculpting it so the speaker fits flush into it, similar to studio style soffit mounting.
The speaker is a large floorstander, and is omnidirectional throughout the bass frequencies, but directional and suitable for corner positioning above the bass frequencies.
The purpose would be to drive the modes evenly and to also tame them...along with the constraints of trying to save floor space combined with the fact that the rear two corners are not available for putting traps into, so I don't want to flush mount and waste bass trap real estate.
I guess I'll want the rear edges of the speakers to be a few inches from the walls so the bass can get past and converge in the corner.
The speaker is a large floorstander, and is omnidirectional throughout the bass frequencies, but directional and suitable for corner positioning above the bass frequencies.
The purpose would be to drive the modes evenly and to also tame them...along with the constraints of trying to save floor space combined with the fact that the rear two corners are not available for putting traps into, so I don't want to flush mount and waste bass trap real estate.
I guess I'll want the rear edges of the speakers to be a few inches from the walls so the bass can get past and converge in the corner.
That should be fine. I forget who posted it, but I think it what discussed having a foam wraparound at one point to limit diffraction. I believe Geddes' home theater is full of absorption directly behind the speakers -so very similar.
-Tony
First I tried a tapped horn and a bandpass sub. That wasn't enough output to match my Summas.
I briefly tried a dipole sub with some TC Sounds fifteens, and that worked pretty darn well. Definitely the easiest solution, but the size of the baffle was insane. (Something like fifty square feet!)
Next I tried an array of sealed subs, and that was the worst by far. Distortion products were very audible, and it colored the sound of the midbass.
At the moment I am using three subs. On is an infrasonic tapped horn that's very similar to the Tower of Power. The other is very similar to the TH-Mini. The last is a bandpass sub.
I'm fairly happy with the results, but I *could* use some extra output down low. The 'Tower of Power' clone goes so deep, it flexes the walls of the house itself. But due to these insane amounts of excursion, I should really invest some effort in adding braces, and buy a bigger amp.
Or better yet, add another 'Tower of Power' type sub.
Also, I don't think the 'Tower of Power' type sub is worthwhile if you listen to music primarily. When watching movies, there's a TON of low frequency content, but when I listen to music, I don't hear it much.
Curious that you didn't like sealed subs? These should have the fewest distortion products if implemented correctly?
Has anyone here tried matching against an infinite baffle sub? I have a stereo IB in my setup which uses the underfloor space that we have in most british homes (I guess you folks on the other side of the pond call it a "crawl space"?).
The IB gives a lot of output, with very low distortion and can be adjusted to be pretty flat down to single digit Hz levels.
I'm interested in adding a pair of Abbeys, but haven't got around to doing much more than planning at the moment (shortage of time to play with hifi...)
Has anyone here tried matching against an infinite baffle sub? I have a stereo IB in my setup which uses the underfloor space that we have in most british homes (I guess you folks on the other side of the pond call it a "crawl space"?).
The IB gives a lot of output, with very low distortion and can be adjusted to be pretty flat down to single digit Hz levels.
I'm interested in adding a pair of Abbeys, but haven't got around to doing much more than planning at the moment (shortage of time to play with hifi...)
ewild, the measurements tend to show that sealed subs have higher distortion than just about everything else. Bandpass subs filter acoustically (and the filtering is applied also to distortion products), horns reduce distortion overall while vented boxes reduce it around tuning. I'd guess that open baffle bass would have the highest distortion, but IB gets low distortion through sheer numbers. There are quite a few measurements at the HT shack of commercial and diy subs.
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