BBV's Room Measurement Saga Continues...

Yes it seems silly to over optimise for one point in the room.

Tenson is that -8db at 630 hz on one channel correct?

 

No you are missing the point. The room suckout has a very low Q. Are the walls stud walls or do you have a solid build? In normal circumstances we would expect to see the 2nd axial mode on the pre eq plot but I can't see it. This is either down to the type of walls you have or your listening position IME.

 

The walls are 1m thick solid concrete on all 6 sides. Wooden laminated floor on top.

 

I could actually cut max boost to 6db and only affect 40hz. Effectively halving the boost for 40 hz.

 

I am surprised Mr Sauer and Mr Coherent havent waded in yet given this golden opportunity to enlighten me!

 

The second axial may not be obvious because his back wall is missing.

-8dB at 630Hz is correct. It needed -4dB overall and the matching of the channels needed another -4dB.

Try cutting the boost as 40Hz and see if it sounds better. I would think the difference in frequency response was going to be more obvious than the difference in dynamics. Remember not all CDs will hit the correct 'spot' at full power causing problems.

 

Yes thats correct - what is the 2nd axial exactly?

15db gain sounds like too much so I will cut it to 6db on both channels, as well as altering the three other bands. I will then check it out when I get the django back.

 

Haha.. sorry I kept thinking 'why does he keep saying he will do it and not just try it?!'

The 'axials' are the length, width and height of the room. These are the primary axials. You then get tangential and oblique. These are when the sound reflects between the surfaces that are not directly opposite each other.

 

Speaking for myself only, I can't provide any enlightenment on digital room correction as I don't have much hands-on experience in this. SM is much better placed to advise. I'm following this thread to learn from it.

Looking at the response graphs on page 1 of this thread, your crossover obviously doesn't have baffle step correction. Is there a way to include that in the digital domain, in a digital xo?

The broad elevation from 6 khz or so up would probably bother me, but 3 dB might be too severe a cut. I'd try following SM advice and shelve down everything above 800 Hz or so by a dB, and possibly another dB from 5 kHz.

OTOH you can leave it as is and work on the reflections; with the anmount of treble energy you have, I'd want to look at some room damping urgently.

 

Yes because you stole my preamp furtively. So which one of these is the 2nd axial?

Markus - yes I agree about the reflections however there isnt that much I can do bar a thicker rug and felt mats around the drivers. When I get my own flat I plan to go for full sound treatment. I think the behringer dcx crososver can do that sort of thing. That would be the next step. I plan to tweak down the hf peaks a little and see where it leaves me. It didnt really sound at all bright as it was. The behringer added some residual harshness. I did try shelving the treble above the crososver point at 3.8 khz one or more db but to be honest it sounded worse.

The current limiting factor appears to be the behringer dac fed from a dvd recorder transport.

 

I don't think there is a 'second' axial as such; simply that SM can see one and not the other. I may be wrong though. I always think of it as length, width and height.

 

Aha got it. It may be they coincide at 40 hz. The cross section is kind of square and there is no real rear wall.

 

The second axial I was referring to was the second harmonic of the primary room mode which should appear at 58hz or so.

Instead we have a null. Given that you have concrete construction, we have two possibilities to my knowledge. which are Tenson?

 

Nope.. I don't think I am the cause!

 

<<The walls are 1m thick solid concrete on all 6 sides>>

Padded Cell?

 

Come on Tenson. I won't spoon feed you. After all - this is your career and profession, I'm merely have a passing interest.

How far exactly are the speaker baffles out from the rear wall?

 

You don't have to spoon feed me, I'm just not going to play your point scoring game. If you think you can help Nick then do so.

 

The speaker front baffle is about 2m from the rear wall and about the same or slightly less from side walls I think. I can measure up tonight.

 

Nick I'm going to leave in a bit, see you soon.

 

Ok see you at the station...