Does room gain at 20hz mean a bad thing? - diyAudio
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Old 10th January 2008, 01:06 AM   #1
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Default Does room gain at 20hz mean a bad thing?

Hi, I'm asking because I have a Linkwitz Transformed sub in the corner of my room. I tuned it to 20Hz.My first sub and I wanted to hear some low bass for a change. Although my amp is not up to scratch, see here Not a lot of Amps drawn, not what I expected!
does this mean room gain could mask whats coming out of the speaker?

I need more info. With relation to the above link, I didn't know where to post it, it is related to this post.

Moderator gonna tell me off, sorry.

T3 is on tv, just witnessed Arnies bad power pack blow up at 1.04 Amps draw and the truck he's driving roared away at 0.93 Amps, I figured the power pack explosion would have zapped at least 5-7 Amps of my powersupply driving my amp???

Please can you explain?

Thankyou.

iUSERTLO72p
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Old 10th January 2008, 08:50 AM   #2
MaVo is offline MaVo  Germany
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i think room gain is a fine thing, since you gain spl for free due to sound in pressure mode - just like in headphones or cars, only at lower frequencies, since the room is bigger. a forum search will show alot of threads about this.
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Old 16th January 2008, 09:03 AM   #3
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i understand your concern with room gain but you should not worry

in-room bass response is NEVER flat and a response that rises slightly towards 20hz can actually be euphonic

in the end it will be a matter of personal preference ...
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Old 17th January 2008, 11:39 AM   #4
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Is it a good thing? I can't give a simple yes or no because it can be a bit of both.

There are a number of things going on at the same time to consider. Consider:

1. As mentioned, a flat response is not desirable - a "house curve" sounds better subjectively, and more accurate. I find +6db at 20 Hz sounds about right compared to a flat response. I prefer to slope up from about 0db @ 80 Hz to +6db @ 20 Hz after I have first got it all flat in the listening position

2. Your room might not have room gain, depending on its construction, and how much of the bass is absorbed by the room envelope and how much is transmitted through it, and this will also affect room modes

3. Room modes will also impact the sound and mess with your target response

4. A flat anechoic response is a good place to start, but then you really want to see what you are getting in-room as it may need more eq

The approach I prefer for a sealed box, which is the one recommended by Rythmik audio, is to build a sealed box with the volume that will prevent the driver bottoming. Then use eq to get a flat anechoic response, then eq to get your target inroom response. I use ultracurve and two Rythmik 12" sealed kits.
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Old 17th January 2008, 11:51 AM   #5
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Quote:
Originally posted by paulspencer


3. Room modes will also impact the sound and mess with your target response

"will also affect" just does not give room modes enough credit. room modes to room gain are like a hydrogen bomb to a firecracker. room modes dominate bass response if the speaker has bass at all. it is as if god created room modes to make fun of all our efforts at producing accurate bass ... you simply can never overestimate their importance imho (unless you're listening nearfield or your room is size of a stadium).
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Old 17th January 2008, 12:32 PM   #6
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This is highly room dependent. In my room they are quite tame, and I have little in terms of peaks and dips to correct. In some rooms they will be extremely difficult. They are often talked about in forums as if they are a HUGE problem in every single room. In the 3 rooms that I have set up and eq'd flat, I have not had significant problems that weren't easily corrected. However, those 3 rooms were all a fairly light construction, plasterboard construction and timber floor. I hear houses are more solid in the US, resulting in much bigger problems.
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Old 18th January 2008, 05:34 AM   #7
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i think on the average in US the construction of buildings is very flimsy

but i specifically picked an appartment in a concrete building so that my music would not disturb my neighbors as much ... now i have a mode around 40 hz for which i am applying about 25 decibels of correction ...

in the previous building i lived in i probably would not have this problem .. but i would not be able to enjoy bass there at all ... instead it would all go to my neighbors which would subsequently call the cops

i mean bass either reflects back causing standing waves or it goes through causing cops to show up

unless you own the entire building ...
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Old 18th January 2008, 11:21 AM   #8
MaVo is offline MaVo  Germany
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you could cover your listening walls with plate resonators to get rid of the room modes to a degree. that would also help to not annoy the neighbours as the amount of sound energy that hits the walls is reduced by them. the patent

http://www.google.com/patents?id=JX4...J&dq=5,975,238

looks interesting, as it claims much more bandwidth than previous "wood box with air spring" resonator designs and could be an easy diy project, as all you need is foam, glue and metal sheets. I read the book about room acoustics, that the patent guy has wrote, he seems to know what he does
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Old 18th January 2008, 12:05 PM   #9
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im not going to bother with room treatment ... too much effort

i would rather just kill myself, its easier
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Old 18th January 2008, 12:12 PM   #10
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I've modified my current room recently. I removed the plasterboard on external walls, put acoustic insulation in, sealed up all the gaps, then put the old plasterboard on, with a second layer of new plasterboard fixed with liquid nails for its flexibility. The difference was huge, and a major surprise. Bass impact is now far more dramatic, but room modes aren't too bad. I have a peak at around 40 Hz which is easily removed.

I did a test. I put the sub in the listening position then moved my mic around the room with a noise generator and a RTA running. This is after I had applied my EQ to get it all flat in the normal position of the two subs. As I moved the mic around, I found I got the best response where they are placed (each sub under the mains), and it was exactly the same as in the corners. The best positions were those I had chosen already.

As far as neighbours go, I don't have problems. I've improved the sound proofing enough that it's not a concern. I've removed all penetrations (central heating ducts) and avoided downlights which put holes in the ceiling - I use trapeze lights instead.
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