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clarets2
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Advice needed to complete JA's "Getting the best from your loudspeakers"

I suspected I had a midbass bloom. Even though I cannot move the speakers more than a few inches (domestic harmony - well I did get the TV!!) I thought I'd use JA's methods to see how bad the problem is in measurements.

Here's the room (19'w x 21'l x 20'h) with cathedral ceiling

Left speaker position with fireplace to left of listening position

Problematic right speaker with rug treatment

Rear of listening room

Having set the reference playback level using 1 KHz tone (track 20) at 75db I recorded the sound level of the track 21 warble tones at intervals from 200Hz down to 20Hz.
I used a digital Radio Shack sound meter.

I created this spreadsheet - hope you can read it!

Having isolated the 50Hz 10db bloom (or should I say boom?)
to the right speaker and attributed it to the box effect created by the TV built-in which is 24" deep, I concentrated on trials to offset:

- Sock as bass plug for front bass port
- Rolled rug as per pic above
- Sofa cushions piled in front and around rug
- moving speaker 10" forward so back is level with front of built-in unit

Plug worked the best as most others were ineffective or killed the 100/80 Hz tone while improving at 50Hz.

I need some more suggestions please and also an indication of how exaggerated these issues are relative to other systems/rooms.

The speakers are Linn AV5140 driven actively by 3 x av5105 200watt power amps. Pre is AV5103 and front end is Ikemi CDP and VPI Scout tt with BenzLP cart.

Speakers have front ported rear facing 8" woofers which may be adding to my problems. However, I have to work with what I've got. Changing speakers is not an option at this time.

Thanks for your help and please ask for clarification / image reposting as necessary.

Peter.

preistube
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Re: Advice needed to complete JA's "Getting the best from your l

Can you set the crossover for the front speakers in your pre/pro higher than 50hz and use your sub to fill in the low bass?

Lin

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

Unfortunately when I set the main speakers to "small" in the pre it impacts 40Hz and below so does not resolve my bloat at 63 and 50 Hz.
All suggestions very welcome!

mrlowry
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Re: Advice needed to complete JA's "Getting the best from your l

What about bass traps specifically tuned to that frequency. Real Traps even has a line of "Spouse-Friendly" Products.

ethanwiner
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Re: Advice needed to complete JA's "Getting the best from your l

Agreed. Bass traps is the most direct solution to improved bass. Then again, if Peter can't even move the speakers without spouse objection, I can only imagine the reaction when he tries to sneak a dozen 2x4 foot bass traps in the door.

--Ethan

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Re: Advice needed to complete JA's "Getting the best from your l

That's why I was nice enough to subtly suggest your "Spouse-Friendly" products.

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

You are correct in assuming that full scale room treatment will not be tolerated but then I did manage to sneak a fairly full size TV, a turntable and LP storage into the book and art display. This is our living room!

I can move the speakers up to 12" but not so that they intrude into the room and are free from the built-in unit.

I can treat the right corner behind the speaker up to the height of the speaker which is 41". The "box" is 27" wide and 22" deep. Currently there is 18" from the back of the speaker to the back wall.
Given there are 2 problematic corners in this "box". Can you recommend what to use to fix?
I'm guessing that Real Traps planter bass trap won't be sufficient.

I'm assuming that this is the major problem I have in the room. Is the bloat at 63/50 Hz, as measured, extreme vs norms or do you see it regularly?

One option I'm considering (just learnt about this option) is lowering the right side bass signal which is possible as my system is fully active and the mono card in the bass amp allows me to reduce the gain by as much as 5db or as little as 1db in single db increments.
What do you think?
I'm not a great fan of treating one speaker differently from the other but it seems that my room situation may make it worth it.

Thanks for your help.

ethanwiner
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Re: Advice needed to complete JA's "Getting the best from your l


Quote:
Given there are 2 problematic corners in this "box". Can you recommend what to use to fix? I'm guessing that Real Traps planter bass trap won't be sufficient.


Yes, our Planter Bass Traps work very well for their size, but that's a big room and you're talking about a very low frequency. I have plenty to recommend, but I imagine they'll all be rejected by She Who Must Be Obeyed.


Quote:
Is the bloat at 63/50 Hz, as measured, extreme vs norms or do you see it regularly?


I see extreme response variations all the time. Not having them would be the exception.


Quote:
I'm not a great fan of treating one speaker differently from the other


Well, you have a room that affects each speaker very differently, much like an EQ. So it stands to reason any correction needs to be asymmetrical too.

--Ethan

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

Am I incorrect in thinking that I can really improve things by treating the right hand speaker and corner alone?

My rationale:
The measurements from the left speaker don't seem terrible indicating that the room as a whole is not a major problem - and as you have correctly pointed out, I am not prepared for the invasion of my living room - forget my other half, I can't accept that level of aesthetic intrusion - now if this was a listening room we could go crazy!

The right speaker is the issue, according to the measurements, and I place that problem firmly at the door of the "box" created by the built-in unit, back wall and side wall. Is this likely to be the case? I am surmising that this "box" is acting as a secondary speaker cabinet.

Potential solutions:
1)Lower the bass input of right channel through the active amp
2)Plug the front bass port of right speaker only (are there downsides to this?)
3)Treat the three walls behind the right speaker with something up to the level of the height of the speaker -41".
This is where I really need help as I've no idea what to use. Am I correct in thinking that it would be possible to place absorbtion material behind the speaker against the walls and effectively reduce the impact of the "box"? or am I wasting my time?

I know whatever solution I end up with will be less than perfect and my main concern is not to mess up what I've got.
So given my physical limitations any practical suggestions?

Thanks for your help.

ethanwiner
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Re: Advice needed to complete JA's "Getting the best from your l

Room treatment is never a waste of time. It can only make things better. As for plugging speaker ports, that doesn't sound like a great solution. Does the speaker maker suggest that?

--Ethan

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

Linn have never recommended a plug and I don't think they have ever manufactured one. I just experimented and it positively impacted the measurements. I agree that it's probably better not to do this.

Hopefully I can get a better response by doing something with the area behind and around the sides of the speaker...but what to do?

ethanwiner
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Re: Advice needed to complete JA's "Getting the best from your l

Your situation comes up a lot in my business.

Potential customer: My room sounds terrible and I know your products will help a lot. The only problem is my wife. But what do you recommend?

Me: I suggest bass traps in as many corners as you can manage. Most rooms need at least four traps to make a meaningful difference, plus absorption at the side-wall reflection points.

Potential customer: Oh, I could never get my wife to agree to that.

Me: Well let me know when something changes.

--Ethan

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

This brings me back to my "waste of time" comment.
If I take your commentary literally you are agreeing that it is a "waste of time" treating the area behind the speaker in order to nullify (not get rid of) the secondary speaker effect of the "box".

Do you agree that this "box" might be acting like a secondary speaker and therefore might be worth special attention?

I understand that your bass traps may not be my solution for this particular corner but my common sense tells me that if I can reduce the "box" effect I will be on my way with an improvement.
Am I mistaken?

ethanwiner
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Re: Advice needed to complete JA's "Getting the best from your l

Two posts up I wrote, "Room treatment is never a waste of time. It can only make things better." And that's the truth. Why don't you just try it and see what happens? Start with six bath towels stacked to be much thicker and see what happens. If it helps, there's your answer and you can then get a proper absorber.

--Ethan

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Re: Advice needed to complete JA's "Getting the best from your l

You need to move the speakers out into the room for serious listening. Your wife won't mind if you move them out when listening by yourself and then move the back when she's home. I do this all the time.

Search my my thread "Sumiko Speaker Set" to see how placement is roughly optimized, then take detailed measurements from the walls to replicate the setting as needed.

Of course, it's up to you to deal with your wife. Dig in and do it. There's no skin off her nose, so she shouldn't object at all. If she does, then you need to do it and stop letting her control your life.

Dave

clarets2
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Re: Advice needed to complete JA's "Getting the best from your l

I hoped that my extensive chart and experimentation up front, shown in my first post, might be seen as starting and seeing what happens.

The chart shows the positive effects of a rolled rug in the corner with sofa cushions stacked in front of it immediately behind the speaker : -4db at 63Hz and -2db at 50 Hz.

Is this enough to indicate that a proper absorber could work?
What would that absorber look like? I can't find one that fits the need of that corner.

I would prefer to find a solution that does not require me to constantly move the speakers.
My listening habits tend to be less than one hour and often.
Even if I choose to move the speakers significantly into the room I still believe the "box" effect of this corner is significant.

Thanks for the prompt responses.

dcstep
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Re: Advice needed to complete JA's "Getting the best from your l


Quote:

I would prefer to find a solution that does not require me to constantly move the speakers.
My listening habits tend to be less than one hour and often.
Even if I choose to move the speakers significantly into the room I still believe the "box" effect of this corner is significant.

You have a choice, move the speakers or kill the room.

Dave

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Re: Advice needed to complete JA's "Getting the best from your l


Quote:
The chart shows the positive effects of a rolled rug in the corner with sofa cushions stacked in front of it immediately behind the speaker : -4db at 63Hz and -2db at 50 Hz. Is this enough to indicate that a proper absorber could work?


Sure!


Quote:
What would that absorber look like? I can't find one that fits the need of that corner.


This would do the job (stand not needed in your front right corner), and we also have a "corner" version that looks a little thinner.

--Ethan

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