alan
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Posts: 21
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Post by alan on Jun 24, 2016 16:59:42 GMT
I've enjoyed reading Mr. Winer's informative articles and used them to build some corner bass traps and side reflection panels out of rockwool. First, the details of my room. My room is 22l by 13w by 9h. I have some absorption at first side reflections and along the front wall behind an 11 foot movie screen, and a panel in each front corner, midway on wall and straddling corner as described in bass trap article. On measurements, I show a sharp spike at 80hz and a null at 33 or so. Not surprising. The weird thing is I show a mid to high mountain peak which begins around 450hz, climbs up plus 10db, then slowly falls. I have martin logan vistas and the crossover is at 450. I also have a sub crossed over around 50 (the Vistas spec at 40hz +-3db). Any thoughts on what can cause this? Could it be floor and ceiling? I have a thin rug and some kind of drop tile, which I thought might be absorptive but reading more that seems unlikely. I'm trying to figure out where to move forward, given the separate issues. I'm most puzzled by the high hump.
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Post by Ethan Winer on Jun 24, 2016 18:24:57 GMT
Without seeing a photo of your room or the actual graph, I can only guess. The first thing to do is rule out the speakers themselves. I suggest you measure each speaker separately with the microphone as close as possible to each speaker. Those ML speakers are tall, so a good "mid point" is probably near the bottom where the woofer and upright panel are joined. Or ask ML for their advice. The Vista web page claims "43–23,000 Hz ±3dB" and I have no reason not to believe them.
Then, if measuring close is flatter, move the mic back in one foot increments and see where the broad peak occurs.
--Ethan
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alan
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Posts: 21
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Post by alan on Jun 24, 2016 19:48:30 GMT
Thanks, I was looking for the best way to measure the electrostats but couldn't find any info. I'm hoping they are not the issue obviously because that would be a major fault, though the crossover point gave me pause. I'll do some measurements and see. In a couple of days I should be able to post some pics and graphs. I appreciate the help. After a few years of audiophile dabbling I've finally come to realize the primary importance of the room. Your site is very valuable.
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alan
New Member
Posts: 21
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Post by alan on Jun 27, 2016 17:09:39 GMT
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alan
New Member
Posts: 21
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Post by alan on Jun 27, 2016 17:52:17 GMT
Here is the back and front of room. I can add more pics if necessary My first look at the charts seem to show that adding the ceiling foam tamed the high frequency mountain somewhat, though it is still showing a little hot in that region. Also need to address that 80hz peak. Looks like there may be some smaller peaks in there as well. Not sure if 30ish null is the speakers crapping out below 43 or room issue. Attachments:
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Post by Ethan Winer on Jun 27, 2016 19:05:52 GMT
You response looks more or less normal, though it would be nice to see what happens above 2 KHz. As always, the solution for bass peaks and nulls is more bass traps. Always!
--Ethan
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alan
New Member
Posts: 21
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Post by alan on Jun 27, 2016 19:11:49 GMT
full range
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Post by Ethan Winer on Jun 28, 2016 16:18:47 GMT
In the big picture this seems for like a broad dip centered at 10 KHz than a peak starting lower. Note that frequency response graphs are usually shown with log horizontal spacing rather than linear. The only time I use linear is when showing comb filtering, or maybe distortion products that occur at regular frequency intervals.
--Ethan
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alan
New Member
Posts: 21
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Post by alan on Jun 28, 2016 17:56:41 GMT
hows this
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Post by Hexspa on Jun 28, 2016 18:18:43 GMT
My eyes tell me your room is insufficiently treated to expect any sort of flatness in your response curve.
I see dips in your low mids/upper bass rather than a "mountain" at 2k.
"Some corner bass traps and some side panels" is a start but not enough. With a 1:2 ratio as your guide, take the first number as your current number of panels (hopefully at least 4" thick) and take the second number as how many you need to build. Then check again.
Thanks,
-m
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alan
New Member
Posts: 21
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Post by alan on Jun 28, 2016 21:12:02 GMT
I'm using what I believe is called rockwool, which I think is about 3 inches thick. I'm thinking I'm going to at least try to get floor to ceiling front corners covered and maybe increase thickness to 6 inches or use different types of panels (rigid fiberglass? 4 inches?) I've got record shelves along the rear wall but I might be able to treat upper corners there. Maybe a little more foam on ceilings. I don't want it to take over the room frankly so I'm probably going to have to live with what that gets me.
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Post by Hexspa on Jun 29, 2016 3:17:41 GMT
I don't want it to take over the room frankly so I'm probably going to have to live with what that gets me. Understandable. That being said, you can really treat the goodness out of your ceiling without it "taking over". In that case I'd advise against foam and just go for regular insulation whether 3-6" rockwool or 10-12" fluffy. The target is around 20% coverage minimum - roughly - I believe (depending on material and specific room conditions). I'm saying forgo the foam because the alternative will give you better modal control in addition to taming early reflections. It's up to you. Thanks, -m
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alan
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Posts: 21
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Post by alan on Jun 29, 2016 16:34:20 GMT
If I order some rigid fiberglass, should I go with Owens Corning 703? I think that's the 4 inch stuff. Seems easier to work with than the rockwool.
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Post by Hexspa on Jun 29, 2016 18:00:10 GMT
The number refers to the density.
I'm using rockwool that's basically equal to 703 but I've doubled up the 2" panels to make 4". You can get 703 in different thicknesses, I think. I'd recommend 4" at least for simplicity and effectiveness.
I think you're making the right choice. Given you're making graphs, acoustics is probably more important to you than you appeared to initially let on.
-m
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alan
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Posts: 21
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Post by alan on Jun 29, 2016 19:13:46 GMT
Yeah, all I'm saying is this room doubles as a movie/social room, with posters on the wall, etc, and I want to be a little judicious about how much coverage I get. But ceiling and corner panels seem not too obtrusive, so I have more flexibility. I've definitely come to believe after a couple of years of dabbling, upgrading equipment, etc, that the room is the most important thing along with speaker placement. No doubt
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