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Speaker/Room Measurement Witchcraftery

Placing the bass near to the rear boundary allows the direct and reflected bass to arrive at the same time, nearly every pro manufacturer recommends this approach, 10-50cm from rear wall, ime this works pretty well, especially if you can adjust the output of the bass as you can with the Kiis and Dutch&Dutch 8C according to their positioning.
Keith
 
Perhaps the sweep tones used to measure are gentle (controlled/slow) compared to dynamic real world instruments say a trumpet or trombone? If this is correct what is the point of these measurements?

The sweep tone is just as slow or fast as the harmonics of a trumpet... at the same freqency!

Your 2nd question is exactly what I am trying to find out :).
 
Placing the bass near to the rear boundary allows the direct and reflected bass to arrive at the same time, nearly every pro manufacturer recommends this approach, 10-50cm from rear wall, ime this works pretty well, especially if you can adjust the output of the bass as you can with the Kiis and Dutch&Dutch 8C according to their positioning.
Keith

My theory is that it's more important for the LF to be time aligned with the higher frequencies that it is to be time aligned with LF reflections. After all if you played a double bass in my room it would be impossible to make the fundamental come from a different location and it would probably sound wrong.
Only my theory though ;)
 
I had ls50's and SVS subs , I rolled the 50s off at about 100hz (48db/octave) and got great results

The LS50s are a really very good.
My crosssover is rather different and uses the natural slope of the LS50 as part of the integration (which is why it's very convenient that they roll off like the CAOW1s).

Anyway I have to put some some strange clothing on now and ride round in a large circle on my MTB :). Thankfully there is a pub near the end of the circle!
 
My theory is that it's more important for the LF to be time aligned with the higher frequencies that it is to be time aligned with LF reflections. After all if you played a double bass in my room it would be impossible to make the fundamental come from a different location and it would probably sound wrong.
Only my theory though ;)
Could you post a photograph of your room?
Keith
 
Why I crossed over so high was to save the poor speakers from doing any bass duty as at higher levels they didnt do so well.
 
Try gating at 5ms (IR Windows > Right Window). Our brains are pretty good at filtering out reflections which arrive more than 5ms behind the source.
 
I've just realised that I measured L+R together, whereas JA measures them separately and then averages. I don't know if this makes much difference.

As far as I know, room response should be measured independently for each speaker.
I believe that JA averages the response of each speaker in a few different positions and then averages the response of both speakers:

For this in-room spectral analysis I use an Audio Control Industrial SA-3050A spectrum analyzer with its own microphone. I average six measurements at each of 10 separate microphone positions for left and right speakers individually. These positions are arranged in a rectangular grid 8' wide by 18" high, centered on the position of my ears in the listening chair, 36" from the floor and around 9' from the loudspeaker positions. The 120 original spectra are averaged to reduce the effect of room resonant modes. What you're left with is basically a snapshot of the balance that the listener hears. Fig.35 shows a typical curve (again it's the loudspeaker whose anechoic response was shown in fig.24). This measurement has proved to give a good correlation with a loudspeaker's perceived balance in my room.
Read more at https://www.stereophile.com/content/measuring-loudspeakers-part-three-page-8

Something like this perhaps?

y4cG8iO.png
 
I also feel that for tonal balance using steady-state pink-noise correlates better with listening.
 
IIRC this is with ports blocked and active crossover in place.

Have you tried the measurements without the ports blocked? Whilst ported speakers tend not to be my favourite things I’ve yet to hear any that have been improved by blocking the port (the only exception being ES14s which are designed to be used with a bung). Every time it kills the mid openness and spoils the tonality. The LS50s are very cleverly designed speakers, I’d be beyond astounded if they would be improved by dramatically altering the way the driver suspension behaves.
 
Have you tried the measurements without the ports blocked? Whilst ported speakers tend not to be my favourite things I’ve yet to hear any that have been improved by blocking the port (the only exception being ES14s which are designed to be used with a bung). Every time it kills the mid openness and spoils the tonality. The LS50s are very cleverly designed speakers, I’d be beyond astounded if they would be improved by dramatically altering the way the driver suspension behaves.

Yes, the measurements are identical for the port versus port open above ~200Hz for both LS50s and CAOW1s. Sorry I didn't save the charts and it might not be the best idea to try to re-do them until my pub stop has worn off.

The LS50 port bungs actually come with the speakers - either a partial bung for near to wall positioning, or full bungs for very close to wall positioning.
I suspect the lack of openness you have experienced is due to the lack of low bass. The ZRBs overcome this.... and some!

My crossover assumes an 80Hz 2nd order natural rolloff from the main speakers - which is what I measured from both pairs of main speakers.
I have been told, by a very experienced speaker designer, that my crossover of around 80/120Hz is more audible than the traditional ~300Hz for a 3-way speaker.

@tuga - that's a lot of measurements :eek:
 
Hi Lee,

Yes, what do you want?
L + R separate measurements at the listening position?
 
...Oh and if you would like a pair of Dutch & Dutch 8c for comparison, please just let me know. I am no longer stocking the Kii Three.
 
@ Lee - OK will do (measurements).

@ h.g.
Cal file (0.5dB/div). I have not tried to enter this into REW. -3dB at 2 or 3Hz at the bottom end:

B_and_K.jpg
 
S-Man, Your in room measurements I assume were taken from the listening position. first, use 1/12 smoothing.

Your sub should be brought at least 5db down imo. Your trying to compensate the 40hz dip with the sub but clearly you should find another placement for your subs . As you can see, you have a serious dip at from 35hz to 50hz. since you cross the sub around 80hz, due to how long those frequencies wavelenght are, as long as your sub are within 3.5 feet from the mains, the subs are <<time aligned>> with the mains. the rule is 1/4 wavelenght. 80hz wavelenght is 14 feet. 14/4 is 3.5 feet.


My experience with subs have been constant, they measure easily flat, at the LP, up to 60hz/80hz if you place them on the front wall, as close as you can from the front wall. this placement helps to remove dips at the LP because it bring the cancellation from the front wall up in frequencies. you should try it at least.

secondly, you have a serious dip at 100hz which is probably easy to deal with by moving your mains around. the 100hz is a cancellation from the front wall or maybe your listening position in relation to the back wall. try either to move your listening position, the 38% rules helps. do not place your LP at the 50% of the room length, nor the 25%!

good luck
 
A mate had a problem with boomy bass. He took measurement and built notch filters but couldn't seem to target the problem frequencies. In the end, I sat in the listening position while he played test tones. It was easy to spot where the problem frequency was but the surprising thing is, what I heard didn't match his measurements.
 
A mate had a problem with boomy bass. He took measurement and built notch filters but couldn't seem to target the problem frequencies. In the end, I sat in the listening position while he played test tones. It was easy to spot where the problem frequency was but the surprising thing is, what I heard didn't match his measurements.

That suggests that either something is wrong with the measurement rig or something is wrong with your hearing, or maybe both.
 


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