[stevenkelby]

Quote:

Originally Posted by jp11801 /img/forum/go_quote.gif generally speaking I am against eqs for no other reason than most people tend to use them incorrectly. Unless you know what you are doing an eq can be a pandoras box. I know Steve will tell you different but the learning curve can be steep. One thing to think about is room treatments they are relatively easy to set up.

I'm getting my SPL meter back from a mate tonight so I'll at least run some tones and sweeps to see where I'm at now. I do plan on room treatment to try and fix big errors but can see that only an EQ can do the fine tuning. 2 identical systems in different rooms will sound different. EQ must be the best way to avoid that as much as possible, once room treatment has been done.

i'll start with traps in the corners and panels behind the speakers. My room is not ideal which is why i'm wanting to do something in th first place, and while I'm doing something to fix the FR, why not do it as well as possible?

My old room, I never considered it as teh sound was close to flawless, the room was almost perfect.

I can see how people would make things worse with an EQ but I'll soon figure it out, I know where to start and know what I'm doing in a car, same principles apply I assume.

 

[bigshot]

Quote:

Originally Posted by jp11801 /img/forum/go_quote.gif generally speaking I am against eqs for no other reason than most people tend to use them incorrectly. Unless you know what you are doing an eq can be a pandoras box. I know Steve will tell you different but the learning curve can be steep.

Actually, I agree. Properly adjusting EQ takes a lot of concentration, hard work and trial and error. But it teaches you a lot about sound.

See ya
Steve

 

[JaZZ]

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif Jazz, was the Technics a cheap or expensive unit? I can see how a lower end one could easily degrade the signal and a high end one might not.

It was definitely a consumer device, but at the upper end of the scale then within this segment. It was about $1000. The majority of EQs were graphic EQs and much cheaper.

Anyway, it's yesterday's technology -- maybe today even cheaper EQs are better.
.

 

[bigshot]

Quote:

Originally Posted by JaZZ /img/forum/go_quote.gif Let's leave it at that! I know that you only take signal degradation on sound-transducer level seriously.

I don't know what you're talking about. It sounds like something in your system was acting up. I was trying to figure out whether it was the equalizer or some other component. You aren't making a lot of sense.

By the way stevenkelby, Technics is a home audio brand- a good one- but it isn't pro grade like the Rane. There are other equalizers that are even more elaborate and expensive. Generally the quality of a graphic equalizer is judged by flexibility/features and the spill between channels. Spill is quite important. It has to transition smoothly from band to band, but not overlap into surrounding channels too much. Cheap digital EQs have great isolation from band to band, but bad transitioning. Cheap analogue EQs have great transitioning, but bad isolation. I've been very pleased with both the smoothness and the isolation of my Rane. It is also very transparent. The rule of thumb is that the wider the correction, the more noise. So your theory of doing as much room treatment first, then EQing as a fine pass is perfect. If you decide on a graphic EQ, you will want to do subtractive corrections to keep the sound clean. This means eliminating imbalances by pulling back loud bands instead of boosting weak ones.

I have only had experience with computer based parametric EQs, so I don't know what the story is on analogue versions of them.

See ya
Steve

 

[jp11801]

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif I'm getting my SPL meter back from a mate tonight so I'll at least run some tones and sweeps to see where I'm at now. I do plan on room treatment to try and fix big errors but can see that only an EQ can do the fine tuning. 2 identical systems in different rooms will sound different. EQ must be the best way to avoid that as much as possible, once room treatment has been done. i'll start with traps in the corners and panels behind the speakers. My room is not ideal which is why i'm wanting to do something in th first place, and while I'm doing something to fix the FR, why not do it as well as possible? My old room, I never considered it as teh sound was close to flawless, the room was almost perfect. I can see how people would make things worse with an EQ but I'll soon figure it out, I know where to start and know what I'm doing in a car, same principles apply I assume.

great thing about test tones and eq is you will also train your ear to a degree about what each frequency is. I often hear people talk about headphones having a peak at 12k or some other random number when I am pretty sure they could not identify a 2K tone from a 12K tone at random.

I've been pretty lucky with my rooms they have been small with carpet and a couch with bookshelves and lp shelves to soak up reflections. The other thing to consider is some people like a live room and some a fairly dead room.

 

[stevenkelby]

Quick update:

Yesterday I called at Derringers, THE pro audio store in ADL. I buy a bit of stuff there and give them chocolate so we're friendly.

They don't have Rane in stock but had DBX, my friend there let me take home 231 free for a week or so to try. Never having used a home EQ before I made some cable when I got home to plug it in with. As I'm not balanced (in any way...) I made some RCA to 1/4" cables but didn't have any mono 1/4" plugs so used stereo and bridged the tip and ring L+R together. I didn't know at the time but this was a mistake! The output was a very low level and I couldn't work out why. No harm done and I got some mono plugs tonight to use, haven't had time to solder them up yet though.

Anyway, before plugging in the 231, I used audacity to make a disc with 20 second tones at all 31 centres, 20,25, 31.5 etc all the way up to 20k.

I sat my DB meter on a tripod on the chair, right where my head goes and let rip.

From 10k to 500Hz was within 4 db of 60 dbA, but 200Hz was 43dbA and 100Hz was 63 dbA.

Hmmm, I knew my room was bad but... Trouble is I have my listening chair in a giant port, a sort of big doorway between two rooms. This way has best WFA but will be changing tomorrow, room will be changing around, sideways, which should be much better. I also have some big acoustic foam pieces to try out in the corners etc. I'll make some bass traps too eventually.

I did listen to the 231 last night but only with headphones and incorrectly wired jacks. At reasonable volume, hitting pause, there was a lot more noise in the signal than without the EQ there. Moving a bunch of sliders in either channel up or down increased the hiss massively. I will try it with my speakers, wired right and set it up etc but I know I'm not going to be happy with this unit.

The DBX 231 retails here for just over $500 AUD ($450 US today). I would get a big discount but still... My friend looked it up and get me a Rane DEQ 60 for about $2500 AUD ($2250 USD) but I can get one from B&H Photo in NY for $719 USD plus $80 postage. Under $900 AUD.

I want to try one first though. I called the AUS importer and they are trying to find one locally I can try in my system. I don't feel bad taking advantage of the offer then paying less than a third of the best price I can get in Australia, would you?

Anyway, that's it for now. Going to rearrange my room, test the FR again and play with this EQ a bit, then treat the room and try to listen to a Rane DEQ30.

I am considering knocking down some walls and building a dedicated room at the end of this year anyway, can't wait for that.

 

[JaZZ]

Good luck with your EQ adventure!

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif Anyway, before plugging in the 231, I used audacity to make a disc with 20 second tones at all 31 centres, 20,25, 31.5 etc all the way up to 20k. I sat my DB meter on a tripod on the chair, right where my head goes and let rip. From 10k to 500Hz was within 4 db of 60 dbA, but 200Hz was 43dbA and 100Hz was 63 dbA.

Using fixed-frequency sine waves as measuring signals will result in unrealistic corrections. Reasonable equalizing needs a smoothed frequency response -- all the narrow-band resonances which can have extreme amplitudes need to be filtered out --, so calls for sine sweeps and the like plus a smoothed frequency-response plot.
.

 

[stevenkelby]

Quote:

Originally Posted by JaZZ /img/forum/go_quote.gif Good luck with your EQ adventure! Using fixed-frequency sine waves as measuring signals will result in unrealistic corrections. Reasonable equalizing needs a smoothed frequency response -- all the narrow-band resonances which can have extreme amplitudes need to be filtered out --, so calls for sine sweeps and the like plus a smoothed frequency-response plot. .

Thanks! I don't know about this, If a sine sweep is played, the db meter will not be able to show the FR accurately anyway, it happens too fast. I know the importance of using your ears but surely knowing where to start with the peaks and troughs helps? I was using sine wave tones at all 30 odd centers, if that was wrong, I don't see why but would love to know and also, how would I get a smoothed plot as you suggest?

All advice much appreciated.

 

[JaZZ]

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif I was using sine wave tones at all 30 odd centers, if that was wrong, I don't see why...

Unsmoothed frequency responses in listening rooms have hundreds of extremely sharp spikes and dips, which can't be compensated for with an equalizer; you have to content yourself with a raw approximation to a straight line ignoring the narrow-band amplitudes, therefore the need for smoothing. Otherwise you could arbitrarily hit an extreme spike or dip. If you don't have a freqency plotter, you could try to slightly vary the frequency around the intended frequency band and chose the average value as reference.
.

 

[883dave]

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif Thanks! I don't know about this, If a sine sweep is played, the db meter will not be able to show the FR accurately anyway, it happens too fast. I know the importance of using your ears but surely knowing where to start with the peaks and troughs helps? I was using sine wave tones at all 30 odd centers, if that was wrong, I don't see why but would love to know and also, how would I get a smoothed plot as you suggest? All advice much appreciated.

What are you using to generate sine waves?

 

[bigshot]

Where you correcting subtractively?

The other thing to make sure of is that the equalizer is properly grounded. Sometimes they need separate grounding.

The DBX 231 is pretty low end. It sells for about $200 discounted. Try the 1231 or for a digital equalizer, the iEQ31.

See ya
Steve

 

[stevenkelby]

Quote:

Originally Posted by JaZZ /img/forum/go_quote.gif Unsmoothed frequency responses in listening rooms have hundreds of extremely sharp spikes and dips, which can't be compensated for with an equalizer; you have to content yourself with a raw approximation to a straight line ignoring the narrow-band amplitudes, therefore the need for smoothing. Otherwise you could arbitrarily hit an extreme spike or dip. If you don't have a freqency plotter, you could try to slightly vary the frequency around the intended frequency band and chose the average value as reference. .

I understand now, thanks. How am I going to get a usable plot to work with using test tones and an SPL meter? I'll try making tones close to the ones I have but a bit either side as you suggest.


Quote:

Originally Posted by 883dave /img/forum/go_quote.gif What are you using to generate sine waves?

I just used Audacity to generate sine tones at the 30 different frequencies.

Quote:

Originally Posted by bigshot /img/forum/go_quote.gif Where you correcting subtractively? The other thing to make sure of is that the equalizer is properly grounded. Sometimes they need separate grounding. The DBX 231 is pretty low end. It sells for about $200 discounted. Try the 1231 or for a digital equalizer, the iEQ31. See ya Steve

I didn't correct anything yet, only listened through headphones while moving teh sliders. The noise/hum got very loud moving the L or R sliders, up or down, especially moving half a dozen together, very loud hum. This was at normal loudish level, with source paused. This must have been introduced by teh sliders. With them flat there was extra noise but probably not noticeable during playback.

How can I ground it better? Should I run a wire to ground teh case of the source, EQ and amp al together? All use 3 pin AC power plugs to ground them.

They do have better DBX units at my local store, I will try something better but already like teh reviews I read of the Rane DEQ 60. Would love to hear one in my system, hopefully soon.

First thing though is to sort out the room as much as possible before playing with the EQ again. Will do it tonight.

 

[sejarzo]

What you really need to do is get a Behringer ECM8000 (~$50 USD) or borrow a similar inexpensive omni measurement mic from one of your pro audio contacts, an inexpensive microphone preamp so you can drive your sound card inputs, and RoomEQ wizard freeware. Quite honestly, it is amazing how much capability is in that for a freeware audio application!

You must register at the hometheatershack forum to download the program, but that's painless...see this page for more info:

Room EQ Wizard Home Page

You can very easily set it up to run full-range sweeps--even though most folks use it to flatten out just their subs using an inexpensive Behringer digital EQ unit.

As JaZZ has mentioned, you probably won't believe the number of peaks and nodes in the response...the raw graph will look like solid area with spikes sticking out of it above 8 kHz or thereabouts, and likely even at some lower frequency.

Actually, you don't even need the graph to prove to yourself how ragged frequency response is in your room.....sit in your favorite listening spot, and just listen to the volume of the sine wave as it runs up the range. You will definitely hear some "warbling" above 4 kHz. Run the sweep in both channels, and close your eyes, and the point from which the sound appears to be emanating will dance between your speakers if your room isn't particularly symmetrical.

I have to say, if anyone hasn't done that on his or her speaker rig, it is a real eye-opener. It only takes about 30 seconds to realize why a given model of speaker can sound so different in various rooms!

You absolutely must use something like 1/3 octave smoothing to view the results in a way that can allow you to decide what to do. (The graphs that you see in magazine reviews for in-room speaker response are created using 1/3 octave smoothing--that's why you never see what comes up in the raw sweep graph published in a magazine.)

It's also imperative to sweep each channel separately to make your decisions on boost/cut. You will likely find points at which you could get one channel flat, and not the other, because one channel is too far off. I believe the best option is to get them as equal as possible rather than have one flat and the other off...consistency between the channels is also important. That will take a lot of trial and error.

There is another program out there called TrueRTA, which also requires a measurement mic/preamp to feed the sound card. It has real time analysis capability, so it can display the your system's response with a pink noise input as a bar graph with various levels of resolution.

The freeware version only has one-octave resolution, but I think it's $40 to upgrade it to 1/3 octave (you pay, get a code, enter it into a config screen, and you're good to go.....you don't have to reinstall the app completely.) You feed pink noise from TrueRTA's generator to your system, then adjust the sliders on your EQ to get the bars on the display as flat as possible.

True Audio: Audio Spectrum Analyzer and Loudspeaker Design Software

Probably a lot easier than using RoomEq Wizard, but involves at least another $40 outlay to get the resolution you need to use it properly.

 

[sejarzo]

I forgot one possible quicker solution:

Steven......does your SPL meter have an RCA jack on it that provides a pre-amp output from the mic, a la the Radio Shack models?

If so, then all you need is an RCA-to-mini arrangement to interface it with your sound card for some preliminary checks--even the inexpensive RS meter is flat enough up to 8 kHz to provide you with some good results.

I also forgot this caveat:

You really do not want your room dead flat. If you adjust it that way, it will sound almost as if you've sucked all the bass out and have two AM radios sitting there instead of your speakers! Well, that's an exaggeration....but typically the response has to drop down as the frequency goes up to sound correct. It varies from listener to listener, but it all amounts to dropping the response significantly down from the high midrange on up.

Google this string:

"house curve" drop per octave db

and you can find some recommendations.

Yup, it ain't easy.

 

[bigshot]

Quote:

Originally Posted by stevenkelby /img/forum/go_quote.gif The noise/hum got very loud moving the L or R sliders, up or down, especially moving half a dozen together, very loud hum. How can I ground it better?

That definitely sounds like a ground loop problem. Connect a wire to ground and try touching it to the chassis of your various stereo components. See if the hum goes away. That will help you figure out what needs to be grounded better. Ground loops can be a real bear to track down.

See ya
Steve