Frequency Reponse

[djoxygen]

Unfortuantely, such an E.Q. will usually also have a large effect at much lower frequencies, despite the band specification on the front panel. If anyone here wants some comparison samples with precise bands cut or boosted, just let me know and I'll create and post some file samples along with reference sample versions, that accurately demonstrate the effects of a particular band manipulation.

-Chris

Just an example, Chris. Not meant to be scientific in any way. There's a lot of stuff going on up above 10K, even though none of it is fundamental frequency information.

 

[Dumar]

Unfortuantely, such an E.Q. will usually also have a large effect at much lower frequencies, despite the band specification on the front panel.

Chris,

Can you elaborate on this please. Earlier in this thread I floated the idea of using an EQ to compensate for hearing loss. I don't know too much about EQ's and was wondering if this is a worthwhile exercise.

Thanks,
Dumar

 

[WmAx]

Chris,

Can you elaborate on this please.

The Q(bandwidth) of the filters in standard graphic equalizers is usually very wide, and to boot, the filters usually effect/interact with each other if you use more then one. Basicly, it might say '10kHz' under the slider, but it may have a broad effect much higher and lower as well. I have an older standard graphic E.Q. laying around that demonstrates this behaviour. If you really want to see the effect, I could measure the transfer function and upload some plotted charts for you.

Earlier in this thread I floated the idea of using an EQ to compensate for hearing loss. I don't know too much about EQ's and was wondering if this is a worthwhile exercise.

The E.Q. might do what you need. Just try it. If you don't already have an equalizer, I can recommend some very high quality units with high precision that are available for a bargain($250-$330) price.

As for compensating for hearing loss -- this is not as simple as it sounds. The brain adapts to hearing changes. If you 'compensate' in order to attempt to provide the same balance as you would have had before the loss(if you have this data), it would not seem natural if you had a theoretically perfect recording and linear playback system, since your brain would not suddenly be exposed to a balance to which it is no longer accustomed. But, if you are just looking for a euphonic(as opposed to accurate) experience, this might be beneficial. The only way to know is to try.

-Chris

 

[Dumar]

Thanks for the reply, Chris.

I would be interested in looking at some plots, as well as hearing your recommendations for some high quality EQ's.

What I had in mind was obtaining my hearing test data, which has been collected over the last 10 years or so, and seeing what would happen if I added some boost to the frequencies I am deficient in. I understand there are digital hearing aids available (for big bucks) that can be programmed to do the same thing. I'm sure it will be cheaper (and a lot more fun) to experiment with an EQ than to buy the hearing aids.

Dumar

 

[WmAx]

Thanks for the reply, Chris.

I would be interested in looking at some plots, as well as hearing your recommendations for some high quality EQ's.

I'll try to get to that for you in the next day or so. I'll post the graph(s) in this thread.

For equalizers, the following will work near perfect in terms of noise, distortion and accuracy/precision:

Behringer DCX2496 ($250)
http://www.zzounds.com/item--BEHDCX2496

Behringer DEQ2496 ($300)
http://www.zzounds.com/item--BEHDEQ2496

You do need XLR-->RCA adapters, or just make up some custom cables that terminate with RCA on one side, XLR on the other and short pin 1 to pin 3 in the XLR connector when soldering for unbalanced(RCA) use. The output level(since this is pro gear) may be a little bit too hot for your consumer equipment -- if that turns out to be the case you can just solder a couple of resistors on each of the output leads to create a voltage divider, or use potentiometers for a variable voltage divider.

Note that the DCX is not strictly an E.Q. -- but it has a precision parametric EQ function. It has the added benefit of also being able to act as an active crossover if you ever wanted to experiment with that functionality. The DEQ is only an equalizer.

-Chris

 

[djoxygen]

You do need XLR-->RCA adapters, or just make up some custom cables that terminate with RCA on one side, XLR on the other and short pin 1 to pin 3 in the XLR connector when soldering for unbalanced(RCA) use. The output level(since this is pro gear) may be a little bit too hot for your consumer equipment -- if that turns out to be the case you can just solder a couple of resistors on each of the output leads to create a voltage divider, or use potentiometers for a variable voltage divider.

If you're going to try this, you should really pop for an active transformer to convert to and from balanced and unbalanced audio. The Aphex 124AX will do both in and out for $200. Most pro audio gear stores (like Guitar Center or online @ Sweetwater) have a 14- or 30-day return policy, so you can try it out and if you decide not to keep your compensation rig, you won't be out the $$ (same goes for the Behringer or other EQ you might try).

Of course this whole thing will only work for stereo (or your mains in a surround setup). And you probably would want to make sure you have some kind of bypass ability or you'll really mess with the ears of your roommate/wife/bestfriend/etc... when they are in the room with you.

 

[WmAx]

If you're going to try this, you should really pop for an active transformer to convert to and from balanced and unbalanced audio. The Aphex 124AX will do both in and out for $200.

I don't see a reason to spend the money(I noticed the Aphex is about $200). For a few bucks you can put together the voltage dividers(if even needed) and the custom patch cords or adapters. The only purpose a transformer would serve is if in fact their was a noise problem due to inability to drive the inputs of the behringer with enough voltage -- but it's not a realistic problem with the DCX, at least, it has input analog variable gain controls with +/- 15dB range range to provide for a broad flexibility of inputs.

I would have suggested other devices for variety of choice, but I am not aware of any other devices providing the power, precision and price value of the Behringer devices. If the poster want to spend a great deal more for comparable devices of different brand -- then the options are a great deal more varied.

-Chris

 

[Dumar]

Thanks for the info you guys.

The DCX2496 looks like it would be a very nice choice. I was checking it out and noted that it automatically detects unbalanced inputs and adjusts its outputs to match. I also noted outputs are rated @ +22dBu max (9.75Vrms). Unfortunately, I was looking to see how this would match up with my older Yamaha RX-V793 and hit a brick wall. It seems I am unable to utilize my power amp independently. There are pre outs rated at 2.6V for the mains, centre, and rears (and 2.4V for the woofer when the mains are set to small), but no way to get the EQ signal back into the power amp. Is my assumption that the EQ goes between the pre amp and power amp a correct one?

Maybe now would be a good time to take a closer look at the Outlaw 7100, or maybe a couple model 200 M-Blocks ... hmmmm.

 

[WmAx]

I have the measurements.

Here is an illustrated representation of the Pioneer GR-777 equalizer band adjustments I used for this test(I made some illustrations to represent the graphical display on the GR-777):

Actual measurements as a result of the illustrated test curves:

As is all too obvious, the band adjustment indicators are not represenative of the actual adjustments, but instead are extremely crude approximation(s). Notice 'testcurve_1', which if one was to believe the graphical unit on the equalizer, would have little to no effect at 63Hz and 8000Hz. Yet, measurement reveals that in reality, considerable effect is present at even 100Hz and 5000Hz. In 'testcurve_3', it is demonstrated that the equalizer can not come close to accurately transforming the input signal to match the graphical display you control. Curiously, even though the scale on the E.Q. is labeled +/- 10 dB, the device appears to only have 8dB ability. I should note that this is probably considered one of the higher quality component equalizers from the 1990's within the mid-range level. It had no noise problem, etc.; just was not precise.

A Behringer DCX 2496 is deadly precise. Below is a plot I measured. One curve is the curve registered on the DCX GUI window(you can basicly pull and adjust/shape the curve however you like). I traced the GUI curve with a program called SPL Trace in order to import it into a measurement program for reference. I then measured the actual output curve of the DCX and overlaid them to see if it accurately applied a curve. Here is the result:

BTW, here is an example(with an absurd shaping example--but nearly anything is possible, and accurately, with the DCX E.Q.) of the DCX GUI as controlled by a computer using the RS-232(serial) interface(you can do everything from the DCX front panel also):

-Chris

 

[Dumar]

Thanks for the excellent demonstration, Chris. I see exactly what you're talking about.

My application is going to require an EQ with the kind of precision available on the DCX ... and what a cool GUI.

Thanks again.
Dumar