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Buckle-meister

Buckle-meister

Audioholic Field Marshall
...is never-ending (sigh).

Dear all

Continuing from where I left off here (Thankyou Mr Nomas for revealing the secret ;) ), I have attached a scale plan (I'm really sorry WmAx; if I knew how to make an AutoCAD drawing into a .jpg I would) of my rooms layout for y'all to help me obtain better sound than I currently enjoy. :)

Bear in mind the following:

1. My two heaters cannot be moved in position.

2. Because I do not yet have a screen to project upon (I use the wall), I am constrained to project in the direction shown. This in turn necessitates that the speakers also be placed as shown.

3. The three windows along the left wall are full-height, i.e. from floor to ceiling.

Right then, lets start out with a few questions shall we?! :eek:

1. When using bass-traps, would I be right in saying that with the windows passing bass right through them, there would be no need for bass-traps at those locations?

2. From the attached plan, it is clear that I could place traps across almost the whole of the wall behind the front speakers. Would this be a poor location though? I mean, if both the direct and (first) reflected sound travels away from that wall, is placing traps there worth it?

3. Bearing in mind that my front towers are a three-way design with rear ports, would bass traps along the wall directly behind the towers help absorb the 'exhaust' from them?

4. From the attached plan, the first reflection from the right speaker bounces off of a doorway. However, at present, this doorway has been removed (don't ask) so that in principle, the sound is not immediately reflected and must travel out into the hallway. Would it be advisable to put the doors back in and place a trap there, or just leave it as it is at present?

5. Even though the couch takes up a fair proportion of the room's area, would I be correct in saying that with regards to bass frequencies, it is almost as if it doesn't exist due to the wavelength of those frequencies?

Well, that's all for the moment folks. Thanks in advance for any help.

Regards
 

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B

bpape

Audioholic Chief
Your assertions about bass trap locations are correct, though not necessarily for the right reasons.

Bass absorbers are most effective in corners. They are less effective or less all encompassing in other places.

The window where the reflection point should still be treated as such - just not as a bass absorber necessarily.

The front wall should be treated somewhat (there is disagreement on this). The idea is that the only thing coming from the front should be the direct sound from the main speakers. What you're trying to absorb, is upper bass, lower mids, and reflected sound from the surrounds.
 
S

sploo

Full Audioholic
For those who haven't yet signed their bank balance away to Bill (and haven't got Word), here's BM's pic...
 

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RLA

RLA

Audioholic Chief
Hello
Is that picture to scale? If it is the listening position is way too far back in relationship to the width of the speakers The golden triangle rule still applies to multi-channel audio ;) Subwoofer 1/3 in from the sidewall is a good place to start as well Knowing that you need seated distance from a front projection system.

I would choose the projector based on resolution and then screen size and set the seated distance based on that. 2.0x the screen distance for low res projectors 1.5 -1.8 x for high res projectors. Lots of planning needed for no compromises in new HT. Speakers may need to be selected based on dispersion characteristics, If they are placed close together and the seated position is back in the room. Get the mechanic's of the install right first, then pursue treatments all the treatments in the world cannot compensate for a poor install. Lots of good advice from folks on this forum. Take your time and read lots to avoid costly mistakes You may want to read some of the many article’s posted on this site
 
ironlung

ironlung

Banned
Buckle-meister said:
Dear all

if I knew how to make an AutoCAD drawing into a .jpg I would



In AutoCAD 2002 go to File/Export... export bitmap then use most any photo program to open the .BMP and save as .JPG.

Hope this helps.
Click to expand...
 
j_garcia

j_garcia

Audioholic Jedi
You can also just screen capture the entire drawng, paste into whatever photo software you have and trim it down to what you need and save as a JPEG. PDF writer would be even better.

I would not point the surrounds directly at your head, as you have shown. This is a common mistake. For the front stage, this is great, but not for monopole surrounds. Yes you want directionality, but not pointed directly at you, as it can become distracting; even when calibrated correctly.

I'm not sure what you mean by "trap"? It sounds like you are talking about damping material, not bass traps - two similar, but somewhat different purposes. Bass traps are not used to eliminate main speaker reflections, they are used to break up low frequency waves collection at the boundaries (generally corners) of the room. Acoustic foam, or something similar, are used to control direct reflections of upper mid and high frequencies.

Do you already have these speakers and you've got them in your room right now? If they aren't handling the lows (sinec you have a sub), you don't need traps to manage the bass they are putting out.
 
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Buckle-meister

Buckle-meister

Audioholic Field Marshall
Mr. Lamb Fries said:
This might be an inexpensive temporary fix to this problem!
Click to expand...
Thanks Mr Lamb Fries. However, although I am presently constrained, I'm not really looking to purchase a screen, even a temporary one, since it would only be false economy.

The reason I didn't get one at the time I bought my projector was because living in a rented flat; I had no idea what size I would require, i.e. for when eventually I get a place of my own. Until this happens, I am content with the picture I currently have. Thanks for the thought though. :)

ironlung said:
In AutoCAD 2002 go to File/Export... export bitmap then use most any photo program to open the .BMP and save as .JPG. Hope this helps.
Click to expand...
It does. Thanks. Although I have AutoCAD 2005 ;) , it's still the same procedure (refer to thumbnail). :)

RLA. Did you have to write such a long reply?! :rolleyes:

RLA said:
Is that picture to scale? If it is, the listening position is way too far back in relationship to the width of the speakers The golden triangle rule still applies to multi-channel audio
Click to expand...
Not sure what went wrong there. I thought my drawing was to scale, but I guess not. I've rechecked my sizes; my speakers are 75" apart and I sit approximately 110" from them, so I'm at about the limit of how far away I should be. I may well pull the couch forward a bit, but if I do, it won't be by much as I don't want to feel the speakers as 'almost on top of my toes' if you know what I mean?

RLA said:
Subwoofer 1/3 in from the sidewall is a good place to start as well
Click to expand...
I've still to putter-about with the sub a bit more, but I can tell you flatly that it will not be placed 1/3 of the way into the room. If I did, at it's current 'latitude', it would obscure my front towers lower drivers.

RLA said:
I would choose the projector based on resolution and then screen size and set the seated distance based on that. 2.0x the screen distance for low res projectors 1.5 -1.8 x for high res projectors.
Click to expand...
Too late! :eek: I already have my projector, and I did look into screen width vs. seated distance and read-up about all things projection at ProjectorCentral.com prior to purchasing it.

RLA said:
Speakers may need to be selected based on dispersion characteristics, If they are placed close together and the seated position is back in the room.
Click to expand...
Too late! ;) I also have my speakers. I did listen to them prior to purchasing, and do have them toed-out from a direct line to my exact listening position (contrary to my plan drawing). This is done based upon my preference, not because it is generally recommended in literature.

RLA said:
Lots of good advice from folks on this forum. Take your time and read lots to avoid costly mistakes You may want to read some of the many article’s posted on this site
Click to expand...
I agree; I've been the recipient of it on many occasions. I have read many articles on this and other sites.

I get the impression that you think I am about to purchase a heap of gear without doing any research. This is not true. I do however very much appreciate the time you took to try to help me out. Thankyou. :)

j_garcia said:
You can also just screen capture the entire drawing...
Click to expand...
Yeah, but that method always gives you a 'fuzzy' picture.

j_garcia said:
I would not point the surrounds directly at your head, as you have shown. This is a common mistake.
Click to expand...
Again, as with the towers, I guess I should've shown their correct orientation on the plan. I only drew the 'line of sight' for clarity. My surrounds actually point slightly ahead of me. Though they didn't used to... ;)

j_garcia said:
I'm not sure what you mean by "trap"? It sounds like you are talking about damping material, not bass traps - two similar, but somewhat different purposes. Bass traps are not used to eliminate main speaker reflections, they are used to break up low frequency waves collection at the boundaries (generally corners) of the room. Acoustic foam, or something similar, are used to control direct reflections of upper mid and high frequencies.
Click to expand...
Aaaaaargh! ;) Ok. It seems that my biggest fault on this site is my generalisations. Let me be more specific:

I have not yet taken an accurate measurement of my rooms response to my speakers. I am currently awaiting a splitter adaptor in order to do so. This thread was started prior to posting the results of the measurement so that I could get a few questions in.

j_garcia said:
Do you already have these speakers and you've got them in your room right now?
Click to expand...
Aaaaaargh! ;)

Again, thanks to all, but may I ask that we try to keep this thread about treatments please. At the end of the day, I can play about with speaker positions until the 'cows come home', but I'll still need to sort out the room's reflections. I'll be truly amazed if, after measuring my rooms response, the results are anything better than awful.

Regards
 

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RLA

RLA

Audioholic Chief
but I can tell you flatly that it will not be placed 1/3 of the way into the room. If I did, at it's current 'latitude', it would obscure my front towers lower drivers.
Click to expand...
Sorry for the confusion I will make this quick :)

1/3 in from the side wall along the front wall not into the room as a starting point and tweak from there ;)
 
Buckle-meister

Buckle-meister

Audioholic Field Marshall
RLA said:
Sorry for the confusion I will make this quick :)

1/3 in from the side wall along the front wall not into the room as a starting point and tweak from there ;)
Click to expand...
i.e. behind the front speakers? Hard up against the front wall?

Regards
 
RLA

RLA

Audioholic Chief
i.e. behind the front speakers? Hard up against the front wall?
Click to expand...
Try placing the sub on the same plane as the speakers not up against the front wall. You will notice a drop in spl at that position but most likely your response will be much smoother tweak final position,spl and phase control from there.

Again just for clarification 1/3 in from the sidewall, give or take and on about the same front plane as your main speakers ;)
 
Buckle-meister

Buckle-meister

Audioholic Field Marshall
Right then. I finally managed to take some measurements (refer to thumbnail in each post).

The first thumbnail of impulse response shows a large spike at around 1.41ms which gives a reflection at around 4.8m, which roughly ties in with the first reflection distance from speaker>wall>listening position. As for the rest of this fairly ragged plot, I'm guessing that that is due to my smooth, hard, unadorned and three-out-of-four solid walls reflecting a fair amount of sound.

Am I on the right track so far?

EDIT: No, I'm not. Refer to post further on!
 

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Buckle-meister

Buckle-meister

Audioholic Field Marshall
The next plot shows the full frequency response. Here I am a little bit perplexed. My living room is square in plan, so I was expecting my results to be far worse than Sploos. However, although the difference in dB from peak to nulls is comparable, I appear to have far less comb filtering than Sploo, although the upper frequencies on my plot appears to plummet much quicker than Sploos.

Presumably, this implies that I am hearing less musical detail than sploo?
 

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Buckle-meister

Buckle-meister

Audioholic Field Marshall
Then we have the low frequency response.

Given that my front towers only go down to 48Hz, I'd say that there is around a 20dB difference from peak to trough levels up to 200Hz.

Not so good, but I'd hazard a guess that, due to my differences in peaks and troughs being shorter than Sploos, my bass response should sound smoother. Correct?
 

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Buckle-meister

Buckle-meister

Audioholic Field Marshall
And finally, we have the 3D waterfall plot.

Apart from the long decay at around 38Hz, my plot shows an average decay of approximately 150ms. Where would it realistically ideally be?

I also have a few 'blade-like' shapes which I believe is not what we want to see. True?

In summary, I'd appreciate anyone and everyone to chip in and tell me just how bad my room's reponse is. Do not hold back! Personally, it's better than I expected, though I've no doubt that treatments in the form of bass traps and mid/high (especially?) absorbtion would help.

The thing is, how much?

Regards

p.s. Sploo, sorry for using you as a guinea pig, but your own results give me a point of reference with which to compare. No offence.
 

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Buckle-meister

Buckle-meister

Audioholic Field Marshall
Hmm. Interesting. I have just placed the doors back on the right hand wall (remember in post #1 I noted that they had been removed) and re-measured. This means that the right-hand first reflection can 'bounce' off of the doors instead of travelling out into the corridor.

From the full frequency response thumbnail, I'd say the low frequency end of the plot is worse than when the doors are missing. I'd say the upper frequency end of the plot from about 10kHz onwards is better, i.e. the slope is less steep.

It's amazing the difference a (seemingly) small change can make! Wow!
 

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mtrycrafts

mtrycrafts

Seriously, I have no life.
Buckle-meister said:
It's amazing the difference a (seemingly) small change can make! Wow!
Click to expand...

Don't forget, that door is a big hole as you go up in wavelengths :D
 
mtrycrafts

mtrycrafts

Seriously, I have no life.
Buckle-meister said:
As for the low frequency plot, there's virtually no difference at all. Is this because these very long wavelengths just go straight through the doors?

Regards
Click to expand...

Just the opposite. It is a small hole to the long waves, insignificant, hence no change. On the other hand, the shorter waves as you go up in frequency, it becomes a huge hole, out they go and no reflections.

You8 can figure out the lenght at some frequencis and see the proportional difference.
 
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