ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Oct 27, 2006 8:58:44 GMT -7
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Oct 28, 2006 23:50:52 GMT -7
Just wondering with my setup - would I be better off driving the two subs in parallel and bridged mono? That would be a 4 ohm load and the EP-1500 pumps out 1,400 watts in bridged mono mode. Currently it is feeding 260w into each 8 ohm speaker.
Or since it is sounding the way I want it to just fo'get about it...
Thanks!
Mike
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Post by ThomasW on Oct 29, 2006 8:17:59 GMT -7
Cool, pretty stealth installation... Most IB's play quite a bit lower than what your graph shows. So you might want to dial in a bit of EQ boost using a 20Hz filter. The only reason you'd need more power is if you needed more output (SPL) is this the case? BTW, please add your name to our map of IB owners..
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Oct 31, 2006 0:48:18 GMT -7
I don't need more SPL, although maybe I'll play around with it a bit. I do have the dials cranked up pretty high on the EP1500. With the bridged power I'm assuming I can turn the dials down significantly.
You had mentioned earlier about being careful with boost below 30hz with my drivers. I was checking out the movement of the woofer on the THX opening at pretty high volume, and there isn't much movement. So you think it is pretty safe to boost at 20hz?
I had put myself on the map, did that not show up?
Thanks for the nice comments!
Mike
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Post by ThomasW on Oct 31, 2006 9:17:46 GMT -7
I had put myself on the map, did that not show up? Mike Yes you're there, with monikers and or just first names sometimes it gets confusing for me to know/remember who's who..
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 10:34:03 GMT -7
Cool, pretty stealth installation... Most IB's play quite a bit lower than what your graph shows. So you might want to dial in a bit of EQ boost using a 20Hz filter. The only reason you'd need more power is if you needed more output (SPL) is this the case? Okay, so I bridged the amp and am running the two in parallel for a 4ohm load. I also played around with the REW (manual input) and re-worked things a bit. Check out this graph: www.teamwrongway.com/REW_graph.jpg] As you can see there is a boost of 16db at 20hz - not sure if I should do this - seems like from what I've read this is a bit dangerous. And then I lowered the other frequencies substantially to make the house curve. Haven't tested it at higher volumes but at normal volumes it sounds nice. I'm concerned though with that 16db boost - although I see someone else here did that. Input is appreciated.
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 11:05:56 GMT -7
I was just checking out the excursion of the woofer with volume at probably the highest I would ever turn it up - seemed reasonable - I don't think it got to the xmax of 12mm (.47"). Probably 80%-85% though. Never heard any bottom and I was there with the finger on the mute button ready to go.
The movie was The Incredibles. Wouldn't watch the entire movie at that volume.
I think eventually I'll upgrade the 18's to something with more xmax to be on the safe side.
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Post by ThomasW on Nov 3, 2006 11:16:03 GMT -7
I changed the hosted image to a link since the graphic is huge.
There is something fundamentally wrong (possibly placement). In my entire life I've never seen a raw plot that bad.
No one is using 16dB of boost at 20Hz it would take multiple kilowatts of power to pull that off. That statement was a joke Chrisbee posted. He has a cumulative boost, but that's a result of cuts elsewhere in his plot.
This is a situation where we're going to need to see a series of measurements. First nearfield in the manifold. Then every 12" going backward from the opening.
I have a scratched cornea, as a result it's almost impossible for me to type. I'll comment more later.
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 12:33:12 GMT -7
Okay, I'm going to have to move the computer downstairs and do the REW the correct way. I'm probably doing something wrong if you've never seen a raw graph that bad before. Unfortunately if it is placement I'm pretty much stuck. It isn't moving, and I'm okay with the sound how it is. I'll just make sure I don't hear an IB that is done correctly... My measurements were taken from the seating area - when you say a series of measurements, do I take the readings with the series of sine waves I used for the initial measurements, and then move back 12" towards the seating area until I reach the seating area? Thanks! Mike
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Post by ThomasW on Nov 3, 2006 13:35:07 GMT -7
I understand that placement is of course fixed. What we need to diagnose is the 'why' of the odd FR plot. There's a technique called 'mapping' the room. That involves taking a series of measurements at different distances and locations. Doing that provides a 'map' of the FR in various locations in the room. Here's a link to the ETF website where they explain a very comprehensive example of mapping a room. www.etfacoustic.com/demoroom.all.htmlNow you don't need to go to this extreme. But we need to know why there's no room-gain at the lower frequencies. And the best way to do that is take a series of measurements at increasing distances away from the outlet and compare them. It would be best to do this using a program like REQW or TrueRTA that has a frequency 'sweep' instead of using test tones.
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 14:14:56 GMT -7
Okay, I'll get the REW setup - unfortunately it won't happen for a week or two as I'm gone on business.
Thanks for your help - hopefully I can get this thing setup correctly. Scary to think of the performance if mine is performing at a substandard level currently.
Mike
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Post by jagman on Nov 3, 2006 14:56:33 GMT -7
Thomas...
Sorry to hear you have a scratched cornea. Have you been to an optometrist or ophthalmologist today? There are many things that can be done to dull the pain. The most effective thing is wearing a "bandage contact lens". If you haven't gone, you should go see a doctor (especially since it's Friday!). The pain usually goes down substantially with a lens on. BUT, DON'T DO IT YOURSELF. Ibuprofen can help, too. You can take as much as 800mg (if your stomach can handle it).
BTW, I'm an optometrist so I'm speaking from experience.
Hope you feel better soon.
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Post by ThomasW on Nov 3, 2006 15:45:43 GMT -7
Sorry to hear you have a scratched cornea. Have you been to an optometrist or ophthalmologist today? ..... Hi, thanks for your concern. And yes I have been seen by the Dr.
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 15:47:04 GMT -7
But we need to know why there's no room-gain at the lower frequencies. I'm wondering if the size of my room has anything to do with the lack of room gain. It is very large and open to upstairs, kitchen, family room. Oh and it has a vaulted ceiling too. We're talking a lot of cubic feet. Hard to get that pressurization effect. I'll definitely do the REW test. What happens if I happen to have one of those rooms that doesn't have the room gain effect? Would drivers that move more air be better? I'm liking those Ficaraudio speakers... maybe I just should have bought those to start with. Thanks! Mike P.S. - and yes, hope you get that taken care of and feel better soon!
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Post by ThomasW on Nov 3, 2006 16:12:14 GMT -7
If it's the room/placement more drivers or different drivers won't change the situation.
What I'm looking for is info that will tell us whether or not you need some bass traps.
Understand this is a situation we can fix, it just appears the fix will be a little more involved that it is for most people.
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Nov 3, 2006 16:33:55 GMT -7
Cool thanks Thomas - you da man!
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Dec 8, 2006 17:37:05 GMT -7
Okay, sorry for the long hiatus. Lots o' stuff going on. I finally got the REW program hooked up and did some tests. Note that these are with the sub signal being processed through my receiver (crossover frequency 80hz). Here is the curve with some EQ: That is from the seated position. Here are some other measurements: Meter lowered inside baffle in front of woofers: At baffle opening: At 12": At 24": At 36": At 48": Let me know your thoughts Thomas. Interesting that I never got anywhere close to 20hz from any measurement... I'm beginning to think that I have an acoustically challenged room. SWAG (Scientific Wild A$$ Guess) - Is it possible the EP1500 mounted in the baffle opening is causing some weird cancellation? Or will I have to do some bass traps? I'm guessing the bass traps will be tough to get past the wife. I think I'd have better luck installing a second subwoofer in the corner opposite the IB (non-IB, painted white).
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Post by ThomasW on Dec 8, 2006 19:05:12 GMT -7
First you must check the low cut filters on the power amp. Make sure they're turned off. From the looks of the measurements they're turned on.
It's not the room. There's something wrong with the measurements or measurement equipment or measurement technique.
If there's a 80Hz crossover in place there should be very little output above 80Hz and no output at 150Hz.
There should be no difference between the 'in-manifold' and the 'at the opening' measurements.
So the meter's messed up (defective? wrong weighting? wrong corrections being used)? And or the software's not working or not set up properly or there's an issue with the soundcard/PC.
To double check don't use REQW, just run test tones and take meter readings and write them down. The meter should be set to "C" weighting and use the 'slow' setting.
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Post by PeterW on Dec 8, 2006 22:15:21 GMT -7
you could also add two more subs for good measure ;D
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ginmtb
Junior Member
Posts: 74
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Post by ginmtb on Dec 8, 2006 22:50:20 GMT -7
First you must check the low cut filters on the power amp. Make sure they're turned off. From the looks of the measurements they're turned on. It's not the room. There's something wrong with the measurements or measurement equipment or measurement technique. If there's a 80Hz crossover in place there should be very little output above 80Hz and no output at 150Hz. There should be no difference between the 'in-manifold' and the 'at the opening' measurements. So the meter's messed up (defective? wrong weighting? wrong corrections being used)? And or the software's not working or not set up properly or there's an issue with the soundcard/PC. To double check don't use REQW, just run test tones and take meter readings and write them down. The meter should be set to "C" weighting and use the 'slow' setting. Yeah, I thought something seemed odd with my crossover point set at 80hz and there being quite a response above there. I'll keep working on this to see what is going on.
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