Servo 15 update. My Thoughts and BFD results.

Very nice work indeed,considering you didnt have a digital equaliser and room correction setup to work with.

 

Hi Phil, I'd add a filter at 36Hz and 71Hz to curb those minor peaks, aside from that you have a very nice response there, nice one.

Why don't you do as I've done and create your own figures, I have 21 measurements but they are all from 20Hz to 80Hz, it means you can get a more accurate picture of your sub's performance. You might be surprised at the findings, when I first did it I uncovered a huge room node at 52Hz that previously wasn't detected due to the large gaps between frequencies in the default graph.

 

That's a good idea, but where do you get correction values for the SPL meter?

Also, it looks from that almighty dip like your two Servos may be cancelling each other - have you tried messing with their positioning? If they are cancelling, then I imagine fixing it by BFD can only be bad....

Dunc

 

looks more like a square room to me with at least two dimensions being very similar.

 

looks like a room with a tv,chair,dvd and probably audio equipment to me.

 

That same dip is almost exactly the same problem I get with one CHT-15 in a ~14.5x14x8 ft room. I managed to tame the dip by putting my sub at the half way point of the left wall.

Although from what I've read on two sub set up, the 12 and 6 o'clock position has been found to be the optimium. Have a look here IIRC: http://www.harman.com/wp/pdf/multsubs.pdf

 

Surely to get correction values all you need do is interpolate between the correction values we do have..... they follow a general trend so i really doubt there will be aby big deviations.

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That's all I did.

Cheers,
Liam

 

Hmm, inter.. intepr... interperpolate.... D'oh, does that mean I'll have to go into the part of my mind labelled "Things I Learned In Maths Class For The Finals And Then Promptly Forgot"...? I hate it when I have to do that....

Or did you just guess?

Dunc

 

Interpolate means to go in a specific number of even steps between two points.

ie. 30 - 70 in 10 unit increments would be interpolated as:

30 40 50 60 70

Surely everyone knows this?

 

Wow, you said your room was bad but that looks scary - it's sucking the life out of the damn things.

How much gain did you have to apply to get rid of that trough? I had a go with my sub this evening and discovered that there don't really seem to be any rules at all when it comes to EQ, just a lot of experimentation! The main trough took +10dB to correct whilst the big peak (no doubt the primary resonant mode of this room) required a staggering -18dB attenutation.

I was a bit worried that I was just killing a tiny frequency range but have done higher resolution tests to check it's actually flattening things out evenly and it looks fine. I'm also not so keen on the +10dB application, but that should be fine once I recalibrate to 85dB. Now I can see how much of a problem I had before....



Definitely worth doing. I can completely understand why people start using BFDs etc and never go back to a non-EQ'd setup. The improvements are very apparent.

MuFu.

 

I agree with the major suck out. Sucks big time.

I too agree there isn't any rule to EQ-ing. So long it sounds good.

Mufu, you could insert in a house curve. House curves tend to make flat response bass sound better. Many feel flat response doesn't sound good. A house curve gives a slight downward slope from 30hz onwards.

You cn try to insert a suitable house curve for your room by doing this.

Play a 100hz tone. Remember how loud it is to your ears. (Don't use the SPL meter anymore). Now play a 30hz tone. This 30hz tone is expected not to be as loud as the 100hz tone. Use the BFD to insert some gain until the 30hz sounds just about as loud as the 100hz. The final part is just to get a nice slope from the now boosted 30hz point to the 100hz point. (Now you can use the SPL meter to help you plot the final curve and settings.) Thats your house curve.

Definately worth doing the house curve. Will definately further heighten the appreciation of the BFD.

 

I don't don't have a BFD, I'm using an impulse convoluting plugin with parametric EQ for a software player to correct the sub's output (just for stereo use). I'll give what you suggest a go sometime - should be fairly easy to do just using the standard graphic EQ.

Cheers,

MuFu.

 

You've just made that up

 

Heheh. Had to get the ol' flux capacitor fired up first, of course.

jag77, I did a little reading about house curves. Apparently C-weighted calibration already applies boost in the sub 50Hz region to make frequency reponse more "subjectively flat". Since I'm already adding 11.5dB@16Hz to try and correct the meter readings I'm not sure it'd be wise to push the sub any more. It's a pretty modest unit with a 10" driver and 200W amp.

Phil, I assume you're using the correction values supplied in the snapbug spreadsheet as well (?).

MuFu.

 

I'd recommend doing this as well. I found similar things by recording a 16-160Hz sweep using the RS meter (shown in green) and overlaying it onto the meter plot:



Look at how much detail is missed by using 1/6 octave intervals! Bear in mind that the sweep recording isn't calibrated, neither does it use the same vertical scale as the discrete meter readings.

MuFu.