Interesting day! (maybe not interesting to read?)

Kevin, just to clarify, I do think your system would still be improved by digital room correction even after the acoustic treatment. I don't think you would need anything like the TACT to do this though. The DEQ2496 will be more than enough to finish the job off to perfection.

Things regarding my prototypes have shifted forwards quite quickly today so I don't think it will be that long before you can hear them in your own place.

Tony, I would love to come and check out your system. I am always interested in hearing how other people do things. I'm not sure how easy it is to get to Cheltenham from where I am in Kent though? Is it easy enough to get there by train?
 
Measuring it with what Tenson? Another Tact or a unit using completely different measurement criteria? Were you windowing the high frequency measurement?
 
As I said in a previous post, I used white noise analysed at a FFT sample size of 32768. I didn't need to though, it was clear from listening that it wasn't achieving the target. Let me play wit this thing for a week when I get the chance and I'll get back to you on what the problem was, as I am sure there was one.
 
Tenson, If you want any help, do PM me. Peter always advised that you could not use another form of measurement to check the RCS's veracity, only another RCS so your results don't really mean much I suspect. If you measure post correction with a second RCS and ,upon averaging get a match to the chosen target curve, then the Tact is clearly doing it's job.

If you were not windowing the high frequency measurement there will be a substantial difference there just to start with. One measures direct sound , the other both direct and ambient sound - big difference.

With regards to the bottom end, two possibilities. One is that you are inadvertently applying the high pass filters when not needed in a 2.0 setup. The second is that you are used to a more reverberent low frequency performance. Certainly the Tact bottom end differs from the like of Velodyne subwoofers and other Para EQ solutions. Prolonged exposure taught me that this is usually due to the highly accurate transient information and that most other solutions are wrong. The temptation is to EQ the bottom end to be flat but the Fletcher Munson curve clearly shows us this is wrong. Additionally, sadly most mastering engineers set levels assuming a certain amount of room gain at lower frequencies. remove that and everything is bass light. The solution is to shelve the curve downwards from the bass, increasing attenuation and not making unneccessary demands on your power amp.

Might I suggest you speak with someone experienced with the unit before proclaiming it to be faulty and inaccurate. It seems a bit hasty to me.
 
Stereo Mic said:
The temptation is to EQ the bottom end to be flat but the Fletcher Munson curve clearly shows us this is wrong.
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The Fletcher Munson curve is simply a graph which demonstrates that hearing is more sensitive in the mid-band than at the top or bootom of the audio frequency range. From this you can't imply that you shouldn't EQ to flat.

When you think about it, it should be no surprise. Human hearing has evolved to perform tasks such as communication with other humans, hunting and running away from predators. Humans, the animals that we hunt and those that might hunt us all have their voice ranges in the mid-band so we can expect increased sensitivity in that region.
 
Steve, when listening at say 80db, the bass needs to be 10db louder than the midrange to be perceived as equal loudness. No problem in most circumstances - the room does it for the listener and the engineer takes account of this I am led to believe.

But what if most of the room gain is removed electronically?
 
We are used to listening through ears which have this response. To EQ it out would sound un-natural. On top of that every ear is different, its just impossible to actually know how to EQ it for your actual ears.

If you listen to a system that has been EQd to be flat even by something simple like white noise, it does indeed 'sound' flat. Or maybe my ears/minds perception is different from everyone elses and I really do have a flat response! I'll keep dreaming.
 
Tenson, if a system is EQ'ed to be flat, it will sound thin and bass light. That's pretty well accepted I think. Again at 80db, a 25hz synth tone will sound half as loud as a 2khz tone if they are recorded at the same level and played back on a system EQ'ed to be flat. Not what we expect or what the producer intended I suspect in most cases.
 
Stereo Mic said:
Steve, when listening at say 80db, the bass needs to be 10db louder than the midrange to be perceived as equal loudness.
Click to expand...
At the 'true' listening level, flat is flat. If you're listening at quieter levels, you may want to turn up the bass (and the treble) a little. The quieter you listen the more the compensation required except that, as Tenson says, our hearing adjusts for this already. Therefore, fully compensating electronically (through EQ) generally leads to an unnatural sound.
 
Sorry, with regards to EQing a flat response I was just thinking flat in the bass, but nothing wrong with raising it a little bit as a whole.

Yes, in that case I do think its a reasonable idea to follow the Fletcher Munson curve. Only to a degree though. As I said all ears are different and as it changes depending on the volume level, I think its best to only be subtle doing this.

If you have a live acoustic recording and play it back through a flat, flat system it will sound the same as it did live. It wouldn't do this if you EQ the Fletcher Munson too heavily in to the response.

If you look at the response of many speakers they actually follow this curve to a level. I wouldn't follow it above about 5KHz though. The directionality of these frequencies makes it pretty hard to EQ anyway.

Interestingly, without actually thinking about it, my system generally follows the Fletcher Munson. It just didn't sound right if I EQd away all the treble boost or didn't have a very slight rise in the bass as it got lower. I usually EQ the bass flat then raise it a little. The treble I normally leave well alone apart from some very low level, broad Q alterations.
 
My college hi-fi system included an Alba UA101 (I think) integrated amp. You used to set the volume control for 'realistic' (read 'loud') and then adjust the sound level to taste using a loudness knob. This automatically followed the F-M curves. Damn clever.
 
Tenson said:
If you have a live acoustic recording and play it back through a flat, flat system it will sound the same as it did live.
Click to expand...

Only at one playbwck level sadly. And I'm a realist, how many unprocessed live recordings do you have in your collection? If you are like me, the answer will be zero.

Steve, as you say at the right level flat does become flat. But it's bloody loud, and most domestic systems are incapable of reaching such levels without increases in distortion.

Tenson, with the Tact, I found, like you, that a curve made up of three flat shelves was highly productive. And no steep roll off of HF information was required because the measurement is already seperating the direct energy from the reveerberent field to an extent.
 
Stereo Mic said:
And no steep roll off of HF information was required because the measurement is already seperating the direct energy from the reveerberent field to an extent.
Click to expand...

Thats quite clever. With the DEQ2496 I just let my speakers have whatever naturally roll-off they already have.
 


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