The Listening Room Reality

Hi Peter, the sound is a bit thin which I am guessing is due to the dips below 210Hz. I borrowed some basic old bookshelf speakers (Denon SC-M101s) and put them on each end of the media cabinet between the Spendors. They gave a much fuller sound though couldn’t compete with other aspects. I measured them and they didn’t suffer from the broad dip in that lower mid range.

I’ll try Xanthe’s suggestion tomorrow evening and report back.

All good, but my worry is that your reading is still showing a 20+ DB difference peak/ trough at just under 60 Hz. Even with God sat on your shoulder moving a speaker by a foot is not going to level that out. Don’t worry, I’ll get me coat… ATB Peter

Whilst the spectrum of the combined signal with the original positioning shows a bass resonance at peaking at 54 Hz which will overemphasise some bass notes, the underlying pattern shows a net roll off of the bass relative to the rest of the spectrum, Is not a simle matter of too much bass, but too much in one fairly narrow band, and too little otherwise (all relative to a flat response - different people may have different preferences for the overall degree bass, some oreferring as recorded, some preferring rolled off, and some preferring some emphasis. The peak at 54 needs fixing, but likely a room effect that likely can be fixed or at least reduced by altering speaker and listening positions, or using room treatment. The net roll-off may be consistent with the OP’s description “thin”, not helped by some sharp troughs in the upper bass.

The separate plots after moving things appears to have countered that general rolloff, but still with a lot of sharp troughs - and still a resonance in tgat same place on one channel.

This is really funny. I listen to quite some organ music and these deep tones are good opportunities to test sonic characteristics of rooms.

Now, my room is 3.95 metres wide. Guess which tone gets reinforced …

…there is no need to worry about all of this…all you need to do is to audition your prospective speakers, in their best placement, in your own room. If the music is good, then you have achieved what I would guess is what most of us want from our systems.

Hi jlewis.
I couldn’t agree more with your observation. In my case we moved into a our new house 18 months ago with an opportunity to have a dedicated listening room finally. A pair of mischievous Fact 12s moved along into a smaller listening space here ( 21 sqm.), and clearly decided to put their foot down. Being determined to make them work to my liking, I had to go through the trials and trepidations of getting the room acoustically sorted to accommodate them. I would agree entirely with you, that buying a set of speakers for a given room would have been much easier, than doing things in reverse order. ATB Peter

I’ve been there too!..but, one way or another, got there in the end.
BW,
J

Your theoretical first harmonic should be at ~43Hz, the second at 86 Hz, etc…
So the first overtone is around 86Hz.

This is for the given dimension, and considering your room is a rectangle

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Congratulations Thomas, you are entirely correct. This more or less equals the F, which therefore gets reinforced. I noticed before that the F was a bit stronger than other tones so when I started to check the values it all matched.

The good thing is that I have SBL’s which limit the impact of it. I had rear ported loudspeakers before and that was a disaster.

Once I have a bit more time, I’ll get a REW microphone out of curiosity.

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Hi @Xanthe

Here are the new measurements, your suggested movements were spot-on to place each speaker the same distance from their nearest sidewall (130cm). VAR smoothing again. Mic was centred, I tried to keep the toe-in similar. I can’t move the furniture as it is bolted into the front wall, so the rear of the right speaker is close to the front of that cabinet.

As to how it sounds (I took the measurements before listening to music so I’m sure that has some influence). The stereo image is sharper, particularly the position of lead vocals. I think bass guitar and drums are louder, there is more foot-tapping drive, and it’s not quite as thin-sounding. There is a slight loss of clarity and separation between instruments. These are all small changes.



Well, that’s much better from the perspective of the frequency domain, to sort out the rest we’ll probably need to look at the time domain.

The first place to look at is the minimum phase plot of the system, then we need to look at the impulse response both the longer time (0 to 500ms) and short time (0 to 10ms).

I’m still concerned about the depth and width of null (cancellation interference) on the left side around 66Hz, that may need sorting out but the left side impulse response may help with that.

Thanks, will look into the minimum phase calculation when I get home tonight.

Good Morning All,

I have posted elsewhere (and dare I mention it other forums). Since I’ve gotten back into my hi-fi the effect the room was having on what I was listening to has been given much more thought than at any time previously.

I am in the fortunate position of having a dedicated room albeit 4.7 x 3.9 x 2.5 metres.

I have utilised both SOV1 and SOV2 which has offered some improvements but more was needed.

Enter GIK Acoustic products stage right.

The temporary installation of the panels has already made a very significant improvement to the sound. The only panels permanently installed so far are the two hanging off the ceiling and the others will get done in due course.

At the risk of offering a somewhat contrary view to several posters above I’m struggling to understand the theory that different speakers will sound different in the same room. Yes they will but a significant factor in this will be the impact of the same frequency reflections ‘muddying’ what you’re hearing anyway - almost a chicken and egg situation.

I would argue that you need to first identify the fundamental room resonance(s) and, where possible, remedy these to ensure that what you are listening to is in fact the speaker and not the room?

Regards

Richard

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Different speakers can indeed sound quite different in the same room.
The same speakers can indeed sound quite different in different rooms.

The issue is that speakers and room interact acoustically. Room treatment is used to control that interaction, leaving five choices to optimise the sound (given in approximate order of the amount of change you can achieve by that mechanism):
1: Fine adjust the position of the speakers in the room
2: Completely change the entire layout of the room
3: Use room treatment to adjust the characteristics of the room to match the speakers
4: Keep swapping speakers until you find something that you like in that room
5: Use a different room

Note that option 4 includes using completely different speaker designs (e.g swapping large floorstanders for panels or sat-sub systems), if you keep to similar types of speakers, then the degree of change available is less than can be achieved using room treatments.

Incidentally, please be aware that implementing parametric equalisation on the main signal (even in the digital domain) can severely impact on the perceived quality of the signal in many ways.

So far, the only way I have found to use PEQ without causing sever negative impact on the signal is to use a sat-sub system and apply the PEQ to the sub signal only, leaving the mid-range and treble untouched. In my experience, I have found that even if there are no filters parameters that are specified for the mid-range, filters specified for the bass regions still affect the mid-range sound. Other people have however found that the generalised side effects of digital equalisation are not a problem to them.

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Hi Xanthe
Having moved into a new build, where building regs state, that the void between ground floor/1st floor must be insulated with 200mm Rockwool, what effect do you think this has in terms of the room being able to deal with low frequency pressurisation? I found my new room somewhat difficult to treat in this respect.
ATB Peter

Hi, yes that can be complex; unfortunately it depends on a lot of construction factors, not just the firebreak material.

At the outset of this response I wish to confirm I am in no way an expert in this field!!

I don’t agree with your Point 3. You aren’t altering the characteristics of the room to suit a specific speaker IMHO. You are seeking to deal with fundamental room resonances which are set by room dimensions, it doesn’t matter where the speakers are placed in that respect.

Simple physics will tell me I have fundamental resonances at 63.5Hz (4.7m), 76.5Hz (3.9m) and 119.5Hz (2.5m).

Speaker placement is important yes for a variety of reasons but, to a degree, these are separate from room acoustics.

I could be completely wrong of course.

Regards

Richard

For what it is worth, but I have 2 rooms having a width of 3.95 metres. In one of them, the loudspeakers clearly have the 3.95 wall to wall. In the other one there are 35 cm deep bookshelves. One would think this makes a difference, but in my case it does not. It seems that the bass frequencies happily go through the soft books and find the walls to reflect.

If a room has primary fundamental resonances at 38Hz and 30Hz, and the speakers have a lower bass response of 48Hz, then the speakers are only going to give a limited degree of excitation to the room modes. In this case you don’t need to use bass traps to integrate these speakers into the room; in fact effective bass traps may actually be counterproductive. On the other hand if you have a speaker with a 28Hz LF response then you’d probably benefit from effective bass traps.

So yes room treatment is about matching room characteristic to the speaker in question; room treatment doesn’t alter the acoustic properties of the speaker, it alters the acoustic properties of the room.

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