Time for a PEQ

[Highlander]

Oh OttoMatic OttoMatic OttoMatic, what am I to do?

I'm still attempting to come to a decision re a PEQ but have hit a bit of a mental brick wall.

If I place a PEQ between the receiver and sub then I can only EQ below my crossover frequency of 80Hz. This seems too limiting to me when inserting a PEQ between the Universal player and receiver allows me to EQ the entire frequency range.

So. Between the Universal player and receiver then. Except that only CDs would end up being EQd because Behringer (all manufacturers?) PEQs don't accept DVD multi-channel digital audio. Whilst audio from CDs is of far greater importance to me than that from DVDs, again it seems limiting to rid the room of acoustic ills when playing CDs but be stuck with them when playing DVDs.

It is of course possible to EQ both CDs and DVDs by using the analogue-outs from the Universal player but this now means that I've got multiple cables from Universal player to PEQ and again to the receiver. It also breaks an all digital path from source to receiver which I was keen on preserving if at all possible. In addition, I think it may also prevent me from extracting a DD/DTS Matrix or DTS Discrete channel from any such recorded DVD soundtrack because decoding is then performed by the player and not the receiver and the former has only 5.1 channel outputs (I have a 7.2 system).

Any advice/ideas (from anyone) on how to EQ CDs and DVDs would be most gratefully received.

 

[OttoMatic]

Hey Robbie,

Well, I went back through some of the posts here to refresh my memory. I looked at your "old" living room plot vs. your "new" living room plot. I'm accustomed to viewing these types of frequncy plots with a vertical axis of 45 to 104 dB. I see yours is 70 to 100, which is a much smaller range, so it will exaggerate these negative effects. I'd also suggest you plot the horizontal in a logarithmic scale.

Those are a couple minor things I just noticed, but thought I'd mention it.

If I were you, I'd start with a BFD. I believe you can fix up most of that <200Hz FR with it. I'm wondering if you could address that big dip at ~110 Hz with phase or distance settings, or perhaps by moving the sub around a bit. I understand that placement can sometimes be difficult.

What mains are you using, and what are your sound quality complaints at frequencies over 200 Hz? Any measurement > 200 Hz? Keep in mind that measuring >> 200 Hz (more like > 5kHz) can become misleading because of all the reflections, possible comb filtering, etc., that occurs as frequencies get higher.

 

[WmAx]

Any advice/ideas (from anyone) on how to EQ CDs and DVDs would be most gratefully received.

If you have any basic experience in electronics (simple basics + can solder ), you can open up the receiver and sever the pre-amp lines from the internal processor in route to the amplifier stage, and add bypass lines to external added RCA jacks on the back of the receiver. I have done this before on an older HK receiver -- it was easy and effective.

Or just buy outboard amplifiers and use the pre-outs on the back of the receiver.

-Chris

 

[Highlander]

I looked at your "old" living room plot vs. your "new" living room plot. I'm accustomed to viewing these types of frequncy plots with a vertical axis of 45 to 104 dB. I see yours is 70 to 100, which is a much smaller range, so it will exaggerate these negative effects.

Hmm. Bear in mind that I'm a perfectionist and am aiming for a response as good or better than that obtained from my previous living room. Mostly, however, I set the scale to 30dB because this more or less covers the range of peaks and dips in the response.

I'd also suggest you plot the horizontal in a logarithmic scale.

I can only do that with ETF for frequencies above 200Hz (see below).

...I'd start with a BFD. I believe you can fix...

The problem's not so much with whether or not I can fix the frequency response, which I'm confident I can, but how to EQ both CD and DVD over the full frequency range (should I wish to make adjustments above ~200Hz) whilst keeping the signal digital throughout if possible, and without a mass of cables from player to PEQ and PEQ to receiver.

Easy huh?!

What mains are you using...

These.

...what are your sound quality complaints at frequencies over 200 Hz?

I've no real complaints at present about frequencies >200Hz as they're higher in average level (approximately 6dB) than frequencies <200Hz which makes the sound come across as more detailed, which I like. I'd simply like to be able to EQ any and all frequencies to, more than likely, flatten the response a bit should I choose to do so. If I place the EQ between the receiver and sub I only get to EQ <80Hz (crossover), never mind <200Hz!

Any measurement > 200 Hz?

This is the (again poor) plot that coressponds to the one provided earlier in the thread.

Bear in mind that in the time since last we spoke, I have discovered that around Christmas time I'll be moving yet again because my landlord has decided to sell the flat I currently rent. Even so, I still intend on getting a PEQ, even if only for CDs in the event that my dilemma re EQing both CDs and DVDs cannot be resolved to my satisfaction.

...you can open up the receiver and sever...

And butcher my beloved Z9?

No chance mate.

 

[Highlander]

If I go with the DEQ2496 and place it between the universal player and receiver I can, should I wish to, auto EQ the full range signal but would set the lower-bound limit in accordance with the instructions to approximately 100Hz.

How then do I EQ frequencies below 100Hz? Normally the impulse from ETF is outputted directly to the receiver and so would bypasses the PEQ. I could EQ below 100Hz manually but would have to do so using the display on the DEQ2496 which cannot match the accuracy of ETF.

If I use RCA to XLR cables I could input ETF's inpulse to the PEQ. Can anybody foresee any problem with this, or have any alternative recommendations?

 

[Highlander]

Well, after a lot of thinking I've gone ahead and ordered the Behringer DEQ2496, the ECM8000 mic, PS400 phantom power supply for the mic, 2 RCA to XLR adapters and 2 XLR to XLR cables.

The DEQ will be connected between my universal player and receiver using Toslink cables from each component, thus preventing any issues with signal voltage (I hope!). Having the DEQ between the player and receiver will enable me to EQ CDs over whatever frequency range I choose, though I'll deliberately set the lower bound frequency to 100Hz so as not to obtain erroneous results when auto EQing. The auto EQ will be implemented using the DEQ's RTA along with the mic, using the XLR to XLR cables (mic to phantom power, phantom power to DEQ). For frequencies up to 100Hz I'll use ETF by connecting the RCA cables that carry the impulse from my PC to the DEQ's analogue XLR inputs by means of the RCA to XLR adapters.

Should I decide at some point that I wish to EQ the sound from DVDs, the DEQ will be placed between the receiver and sub so as to work upon the low frequencies the subs see.

...buy outboard amplifiers and use the pre-outs on the back of the receiver.

This was a good suggestion and would certainly have solved the problem of EQing CDs and DVDs. However, I'm simply not at a point where I want to purchase a set of power amps. When eventually I upgrade my (front L/R) speakers, this may be the time to re-evaluate.

Many thanks OttoMatic and WmAx (but not Zumbo ) for all your input. It was very much appreciated.

 

[WmAx]

he auto EQ will be implemented using the DEQ's RTA along with the mic, using the XLR to XLR cables (mic to phantom power, phantom power to DEQ).

Why would you use an external phantom power supply box when the DEQ has phantom power built in?

For frequencies up to 100Hz I'll use ETF by connecting the RCA cables that carry the impulse from my PC to the DEQ's analogue XLR inputs by means of the RCA to XLR adapters.

Actually, the easiest way will probably be for you to use something like Room EQ Wizard( http://www.hometheatershack.com/roomeq/ ), the freeware application. I believe this program will measure and give you resultant parametric filter values to manually program into an equalizer such as the DEQ.

You will need to feed the mic to the computer soundcard input. You can get a Behringer UB802 for about $40 from musiciansfriend.com (they have UB mixers on clearance), which has built in phantom power and proper outputs to feed directly to your sound card line input jack.

-Chris

 

[Highlander]

Why would you use an external phantom power supply box when the DEQ has phantom power built in?

$!%"&!!!

Thanks WmAx. Should've noted that in the manual I'd downloaded and 'read'. I should be able to correct the order before it's sent out. This also means that I need only one XLR to XLR cable instead of two.

...the easiest way will probably be for you to use something like Room EQ Wizard...You will need...a Behringer UB802 for about $40 from musiciansfriend.com...

Checked the website. Although they do ship internationally, they don't ship Behringer internationally. Here in the U.K. the UB802 is twice the price noted above.

Thanks for the advice. I may yet go down that route but for the moment I'll give ETF a go and see how I get on.

 

[OttoMatic]

Good luck, Highlander; let us know how it goes.

 

[Highlander]

...let us know how it goes.

Will do.

 

[Highlander]

...let us know how it goes.

Hmm, well, you my find this hard to believe, but I received (most of) my order only as of today.

The good news is that the DEQ rocks! A fitting addition to my system...apart from the very minor scratches along the front (top) edge. For this reason I'll probably send it back for a like for like replacement.

The ECM8000 mic is surprisingly weighty. It certainly gives one the impression of quality.

I'm still due to receive one of the two ordered RCA to XLR adapters (this is the reason the rest of the order was held back ). As soon as that arrives I'll be good to go. However, as reported earlier, I'll be moving flat soon - I now have a definite leaving date of no later than 20th December. In light of this, I've decided that I'll play about with the DEQ's functions to become totally familiar with it but will not attempt to fix any of my rooms ills as there's no point with my move being imminent. I'll start that after Christmas and report how I get on.

Did I mention how cool the RTA display is? (definitely a boy's toy)

 

[evan]

deq

I don't want to wait until after xmas , go ahead and fix your room so I can make my mind up on this

 

[Highlander]

I don't want to wait until after xmas...

Then I'll tell you what Evan; just for you, as soon as I get my replacement DEQ and adapter I'll take measurements and, so long as you appreciate that it'll only be an excercise to show you what difference the DEQ can make, will report back as soon as I can. Deal?

...go ahead and fix your room so I can make my mind up on this

Perhaps I can help by listing the features that in the end made me choose the DEQ2496:

1. No need for potentiometers to reduce the line voltage from the (Pro) DEQ in order to be compatible with my (Consumer) receiver by instead using the SPDIF optical digital input/output;

2. An all digital signal path from source to receiver;

3. A PEQ with what should be a sufficient number of bands (10 per channel) for me to sort out low frequency issues (the 31 band 1/3rd octave semi-parametric or so-called 'virtual paragraphic equalizer' GEQ was an added bonus);

4. A RTA in conjunction with the ability to auto EQ to a user specified curve;

Hope this helps.

 

[Highlander]

Question:

Although I'm due to receive my replacement DEQ2496 and adaptors tomorrow that will enable me to begin taking measurements and posting results, I had a trawl through previous results and noticed that consistently around 39Hz and 73Hz I've what appears to be a couple of room modes.

As a quick experiment I went into the PEQ section of the DEQ and began cutting the gain, centred on the aforementioned frequencies. When lowering the gain beginning with 39Hz, whilst playing a CD simultaneously I should add, I noticed the LED meter at the left side of the DEQ light up red, indicating clipping.

Why would lowering the gain over a range of frequencies possibly cause clipping?

 

[Highlander]

Hmm, well it seems that lowering the Gain Offset parameter in the UTILITY menu sorts out the problem. However, the only explanation given for this feature in the manual is "Here you can correct the overall gain of the EQ modules" (the manual probably expects the user to know what he's doing ). Given that this was at 0dB, i.e. leaving the signal untouched, my question still stands:

How is it possible to cut the input signal (the LEDs are for the input signal only) and yet show clipping ocurring?

Also, in the I/O menu, one can set the parameter DITHER to OFF, 24-bit, 20-bit or 16-bit. Now I know that CDs are 16-bit, but my question is whether DITHER should be set to 16-bit or OFF. If, as described here dither is part of the CD production process, do I really need to re-apply it? Is it perhaps instead meant to be used when EQing an analogue source?

 

[Highlander]

I still haven't gotten to the bottom of the problem even though I know how to get around it. I have, however, made an observation and to explain, I'll describe in detail what is happening regarding the issue of clipping.

1. The LEDs that form the METER display only ever monitor the input signal, in my case always from the player to the DEQ2496 via Toslink;

2. As many will know, CDs are not all recorded at the same level; many modern CDs are recorded 'hot' whereby their peak level is very close to 0dB over which digital clipping occurs;

3. No matter what CD I play, if the signal input to the DEQ2496 is directly routed to the output jacks, thereby bypassing the GEQ, PEQ etc modules, no clipping occurs. However, analysis of a CD like Erasure's Nightbird reveals that the peak level (though the meter remains virtually stationary at the peak level over time) of most if not all songs is at a staggering -0.1dB. This would be a 'hot' CD. By comparison, playing Chris de Burgh's Missing You reveals a peak level of -1.9dB (with the meter varying over time).

4. If the Gain Offset parameter is set to 0dB then logically the input level will equal the output level when either (a) the output signal bypasses the GEQ, PEQ etc modules or (b) the output signal does not bypass the GEQ, PEQ etc modules, but the module levels are set at 0dB, and this does indeed occur;

5. Following on from 4 above, routing the input signal through the GEQ, PEQ modules but reducing their gain should have no effect on the input level and should not cause clipping to the output level, yet it is at this stage that clipping occurs...and is shown occurring to the input signal!

6. Clipping does not always occur. I now know that part of the problem is that with a 'hot' recorded CD, clipping is much more likely because the initial level is on the verge of clipping before you even start to make any changes. For the same but opposite reason, with a properly recorded CD clipping does not occur at all;

7. The question is: why is clipping ocurring at all? The input signal is just that; an input. When any adjustments are made in the GEQ, PEQ etc modules it is the output signal that varies, yet the LED meter clearly shows that when the GEQ, PEQ etc modules are engaged with changes, and a 'hot' CD is playing, cliping occurs.

Doesn't make sense to me even though, as I wrote at the outset, the problem is easily solved by lowering the Gain Offset a touch in level. This has the effect of reducing the level of the output signal but, as far as I can see, must be reducing the input level too because clipping then ceases.

Doesn't anybody have any ideas/explanations?

 

[Highlander]

Doesn't anybody have any ideas/explanations?

Guess not.

...I'll tell you what...

Evan, bad news I'm afraid. I'm simply not going to have the time to putter about with the DEQ2496 any more than I have until after Christmas when I'll be settled into my new place. I'm very sorry for not being able to deliver what I wrote I would. If you're still interested, keep an eye out for results to be posted, hopefully, sometime after the New Year.