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 http://www.diyaudio.com/forums/showthread.php?s=&threadid=115177
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:confused:
 
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.
 

vasyachkin

Disabled Account
2007-12-31 1:16 am
paulspencer said:


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).
 
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.
 

vasyachkin

Disabled Account
2007-12-31 1:16 am
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 :D

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

unless you own the entire building ...
 

MaVo

Member
2006-01-07 12:40 pm
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=JX4XAAAAEBAJ&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 :)
 
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.
 

MaVo

Member
2006-01-07 12:40 pm
vasyachkin said:
im not going to bother with room treatment ... too much effort

i would rather just kill myself, its easier

the room is an important part of the playback chain.

uneven reflections can mess with the stereo image, room modes mess with the bass response, reverb messes with the original room information in the record, boundaries introduce phantom images and comb filtering...

ignoring this and you dont have to make an effort to build nice speakers, since it will be fundamentally flawed.

besides... the effort makes diy fun. i wouldnt dare to diy without having fun with the work.
 

vasyachkin

Disabled Account
2007-12-31 1:16 am
im perfectly aware of the fact that room is the weakest link in my system ... and im not going to do anything about it

to me room is an "external" factor and modifying it constitutes cheating

it would be like treating asphalt with something to make your car get better quarter mile time ... im sure it would work, but it would be cheating ... because on another track your car would still be just as slow

you don't need a very good system to get good sound in a perfect room. to get decent sound in an untreated room is another matter.

i prefer having a factor of 10 reserve in power output and three digital sound processors to having a treated room even though it doesn't work as good - why ? because i could move to another room tomorrow and it would work the same.

in fact i could sell every part of my system on ebay if i wanted ... try that with a piece of foam that you glued to the wall ;)
 
Interesting views

Hello everyone, I think when it comes to rooms, its a subject that most will either not understand, or get frustrated. If I'm wrong, I apoligise now. Me, I understand it from a point of (Torch) view. As in a torch/beam of light fires across the room, meets a boundary and reflects in a straight line across to another boundary, slowly delaying. But that on a larger scale with multiple reflections and including the other channel.:confused: Then theres room Modes, and Nodes, standing waves and so on. Would be a pretty spectacular light show.

I'm stuck with room treatment because of W.A.F. I'm in a 3m x 4m x 2.5m room made of brick walls, 2 glass windows and a glass door. A fire place/chimney, wooden door and 2 2seater sofas, a PC with small LCD and a LCD TV a radiator and small coffee table.

I think I need to EQ my sub, I got some audible boom as well as some seriously nice deep lows.

I downloaded SynRTA and have a Vocal mic I bought from Tandy/Radioshack, cost me £30 to 40. Some years back, but not sure how I should use it. I have my PC connected to my amp and a 24Bit 96khz soundcard from Creative.

What do you think?

iUSERTLO72p:)
 

vasyachkin

Disabled Account
2007-12-31 1:16 am
Re: Interesting views

iUSERTLO72p said:
I downloaded SynRTA and have a Vocal mic I bought from Tandy/Radioshack, cost me �30 to 40. Some years back, but not sure how I should use it. I have my PC connected to my amp and a 24Bit 96khz soundcard from Creative.

What do you think?

iUSERTLO72p:) [/B]

i think you can equalize room bass response by ear. no need for for any measurement equipment just a free software test tone generator.
 
If you own the space that you use as a sound room, then it makes sense to pay attention to its acoustics. It can be one of the most cost effective things you will do. Spending about $250 on the room gave my two subwoofers the impact of many more subwoofers - they sound more like 6! To buy that many subs would have cost a lot more than what I spent.

However, if you are renting then your options are much less, but they are still worthwhile.

I've found in an average room that doesn't have heavy construction, and one that isn't without reasonable absorption, that you don't need treatment to achieve good sound. A little digital trickery can help a great deal.

I'll soon be doing some paintings, with foam behind, and placing them to absorb first reflections. Quite cheap and they serve a dual function. They do nothing for bass of course.

I have no experience with bass traps, but I suspect that to get a worthwhile improvement, they need to occupy too much space.

My preference is for open baffle, hence a dead room is not required, and not desirable. I've also found that for conventional box speakers, I prefer a room of "average" acoustics - not too dead.
 

vasyachkin

Disabled Account
2007-12-31 1:16 am
paulspencer said:
vasy, I think that's a bit optimistic to think you could do it by ear! I use my ears to evaluate what has been measured and corrected. When I try something, and see the response, I then evaluate and get feedback.

i run the test tone generator and slowly change the frequency - 79hz, 78hz, 77hz, 76hz etc ...

when i determine that some range sticks out or is lacking i go to my parametric EQ and boost or cut it ... then i repeat the process

i repeat the process as many times as it takes until there are no ups and downs just a smooth rolloff

then i listen to some test tracks and decide if i like the character of bass. if i want to emphasize or de-emphasize anything i then go to the graphic equalizer and adjust. then i listen to some more test tracks, adjust again, repeat.

eventually you reach the sound that is just right.

i would argue that my method is actually more effective than yours. because my negative feedback loop spans not just the electronics, transducer and room but also the ear-brain mechanism.

in other words my technique inevitably produces response that is better than accurate. it produces response that sounds accurate and that is more important.

the goal is not to satisfy your microphone, it is to satisfy your ear-brain.

i haven't tried to design DSP crossovers by ear yet, so i cannot say if that works or not ... but equalizing the sub by ear certainly does.
 
You might want to know what method I use before saying yours is better.

I start with a very accurate mic and calibrate it flat at the listening position - in fact the entire system from 20 - 20k.

Then I dial in a house curve using parametric equalizers. I can see how it is made different to flat, and evaluate and change it instantly. Very easy to try different settings, and switch from one to another quickly.

I also add dynamic eq, which compensates for the sensitivity of the ear at different levels. I can boost bass at lower levels, and I also tend to tame the treble dynamically at very high levels, which I find subjectively better.

Essentially I'm using both my ears and the mic. I let the mic do what it does best - give me a starting point that is flat. Then I let my ears tell me when the house curve sounds just right. I typically boost the bass 6db over flat relative to 100 Hz. It's very quick and easy to add more or less, or change the curve that I use.

It's quite possible that either method could arrive at a similar place.

Before you described your method I was thinking that you meant you would guess the settings. ie "ohhh that sounds like it needs 6db of boost at 37 Hz with a high Q and -17db @ 20 Hz with a mid Q." That's what I was thinking when I said "optimistic."
 

SpeakerBob

Member
2002-08-15 6:21 pm
UK
I'd just like to stick a counterpoint in that ime anything calibrated 'flat' with an RTA sounds absolutely horrible due to the RTA not being able to filter out the rooms reflections.

Way too much treble.....

Harsh , cold, but wow lots of detail!...

Rob.

I use the RTA mainly for bass where the sub needs EQ and to match seperate drivers at their xo's.

I expect to see my tweets way lower than my midbass when I'm done.