MF 1000

Treating Room Nodes with bass traps etc

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Super Wammer

Revise down plot as requested Tuga...

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49 minutes ago, MF 1000 said:

I might have chance to do some more analysis this morning and post up the curves.

If you post the mdat files it will actually give us more information and be quicker for you.

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25 minutes ago, MF 1000 said:

Revise down plot as requested Tuga...

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The most important change suggested above was to measure left and right channels separately. Is this curve still both played together?

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Super Wammer
Posted (edited)

A single guided I've carried out some more analysis this morning and this has been quite revealing 😀

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above is the LHS Volt driver from 1 m 

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and the RHS Volt .....immediately it's obvious that it's output is lower, so I adjusted the A500 gain to get a closer match to the LHS

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a small improvement- I'll investigate this more at a later date

i looked at increasing the gain & eq on the midbass to address the 'shelf' comments which gave this overall curve

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breaking this down into LHS & RHS 

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The RHS bass is still lower by around 5-8 dB I will look into this to get a better bass balance

and the final overall curve

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With the psycho acoustic smoothing the bass dip at 65 Hz looks much better .....which is probably why on listening tests you don't hear it 😀

Edited by MF 1000
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Posted (edited)

Balance looks better after EQ but you may wan't to consider reducing the tilt angle, make it more horizontal.

Psychoacoustic smoothing is adequate for checking the overall balance, but to evaluate room-generated peaks and dips it's best to smooth 1/24th or 1/12th at most.

Could you post graphs 1 and 3 with 1/24th octave smoothing?

It looks like the LHS needs repositioning. Are the subs postioned symmetrically in the room?

Edited by tuga

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Super Wammer

I'll post up the 1/24 graphs later Ric....off travelling to Worcester this afternoon - work gets in the way of hifi at times 😛

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Super Wammer

Thanks Martin

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Super Wammer

The subs are symmetrical in the room and my listening position is dead centre between the speakers.  The curves for the Volts LHS & RHS were taken with the mic directly in front of each cabinet 1m from the driver.

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here they are with revised smoothing at 1/24th.  Quite clearly there is an output difference - each Volt 18 is driven by a single Behringer A500 in bridged mono mode.  Once I'm back home I'll look at gain matching the LHS to RHS, probably by lowering the LHS by around 10dB, the knock on effect of this could be reducing the 'tilt' in the overall curve.

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As I have the sub & mid bass on one dcx unit and the midrange and tweeters on another dcx I can adjust the overall gain on each unit to address the tilt.  Currently if I increase the gain on the midrange/tweeters the background hiss level increases, so a reduction in the bass gain would seem to be the way forward.

I will also look at a LHS & RHS check on the midbass/midrange from the KEF 103/4's

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18 minutes ago, MF 1000 said:

Quite clearly there is an output difference - each Volt 18 is driven by a single Behringer A500 in bridged mono mode.  Once I'm back home I'll look at gain matching the LHS to RHS, probably by lowering the LHS by around 10dB, the knock on effect of this could be reducing the 'tilt' in the overall curve.

This looks like a good starting point.

Once they're matched my suggestion is that you work on the transition from subs to mains. What slopes are you using? High and low pass filters should start roll-off before transition frequency. It's easy for the summed output to result in a bump and there's one at around 120-130Hz. Ideally you sould be tweaking and measuring outdoors.

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Super Wammer
Posted (edited)

Thanks for the guidance Ric.  I'd love to do the outside test but given the weather and time involved in moving 800lbs weight of gear, setup time etc it's not a viable option.

once I'm back home I'll look at the xover frequencies/filter curves to see if that will help with the hump......something I hadn't considered ....all part of the learning process and the crazy journey I'm on 😀

And it's great to have the environment back here where you aren't flamed for lack of thought etc :^

Edited by MF 1000
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1 hour ago, MF 1000 said:

 Once I'm back home I'll look at gain matching the LHS to RHS, probably by lowering the LHS by around 10dB,

You probably have this in mind anyway, but I think it's important to understand why the current difference has arisen, rather than just changing gain. You could swap the subs over to separate out room/position induced differences. I actually wonder if there may be an issue affecting both subs, since both look like they have a response that's gradually falling off as frequency decreases. In case it's of any interest I'll post a measurement from my own sub with no crossover or EQ applied (and the same 1/24th smoothing you have above). I'm a little surprised at how different yours are but I may well be missing something obvious. image.png.8317c4c5b6aada0cb8450ee159734506.png

I'm not sure how much you want to explore but bear in mind that you have the option of running your two subs with a combined left plus right mono signal, rather than as separate channels. There are advantages to doing this provided your crossover frequency and roll-off are such that the frequencies from the subs don't get high enough that you can tell where they come from. With a sharp roll-off this may well be higher than you expect (I'm currently crossing over at 120 Hz but with 48 dB/octave roll-off filters). The benefits of running the subs mono are that you'll get consistent results for bass no matter where the sound is panned in recordings (which is not universally the dead-centre you might expect). Having the subs working in a consistent complementary fashion means you can take advantage of placements like one in a corner and one in the middle of a side-wall, or opposite corners, to get a more even bass response.

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Super Wammer

I might try swapping the subs over and/or the A500's to see if it's variances in the amps etc. The more longer term test would be to convert the ports to 150mm from the current 100mm, which may aide the very lowest frequencies.

 The bass response from a listening perspective is good my go to test track for ultra low bass (Daniel Chorzempa at West Point Cathedral...64ft bass pipes playing Boellmann Suite Gothique Toccata) sounds very good.

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