Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 63

Hmmm.. can this really be this easy?

 

Here are some screen caps of the EQ function in REW:

 

This one shows the pre-Audyssey response of my two subs together (all graphs below at 1/24th smoothing). Ignore the waterfall for now as I didn't set the modal parameters in REW - I just wanted to concentrate on the FR for this exercise:

 

This one shows the target curve I set for 10-200Hz:

 

This shows the predicted curve after REW has calculated the filters:

 

This shows all three of the above overlaid for comparison:

 

This shows the filters calculated by REW, using the Behringer DSP1124P Parametric Equaliser. REW would be able to upload these automatically to the 1124P if I had one:

This shows the assumptions I gave REW to work with (I stabbed in the dark):

 

 

Can it really be that easy to get such a flat FR over the selected range, using a cheap parametric EQ and REW?

 

I should add that once you have set the parameters, then you just hit the GO in REW and watch as it creates the predicted curve. Amazing.

 

You can also load a target curve too if you have one, but I am thinking that if you EQ the bass response to flat, as I have done here more or less, then run Audyssey, the latter will add its own target curve to the input it finds. I realise we don't want a flat response across the bass region, but a gradually rising one - but won’t Audyssey take care of that, along with DEQ?  Alternatively one could run Audyssey first and then apply the EQ to Audyssey's final curve by way of fine tuning. I believe it is better though to get the curve as flat as possible before running Audyssey so it has less to do - but that might be me conflating this with getting the room as good as possible before running Audyssey. If so, then I'd run the EQ first and Audyssey second.

 

If it really is this easy, I feel the purchase of a 1124P coming on :)  It's only $100 or so...

 

Anyone who knows what they are doing (as opposed to me who is guessing), please chime in... Thanks!

I did some more measuring to concentrate on the sub alone and placement; so, I disconnected the speaker. I also turned off the EQ. So all of the measurements below are without EQ.

My first comparison was the center of the rear wall with the center of the front wall. Moving to the center of the front wall appears to have removed the dip at 70 Hz, but introduced a hump at about 35 Hz and 30 Hz. To me it appears that the location on the rear wall is smoother overall. Thoughts?




But then things got a little weird. I decided to do some very near field measurements of the sub to establish the response without the room modes. I had done this about a year ago when I went through a similar exercise. Remember I had EQ'd things for my previous measurements because there were some humps in the graphs. These humps were not there last year when I was measuring. The graph below shows what I mean. Again, there is no EQ on for the new measurements and none a year ago. I thought maybe my current sub (the Def Tech) had a problem, but then I connected an older Yamaha sub to see if that would show something similar. Any idea what's going on here? Either the signal from the receiver is 'off' or something else?? It looks like my receiver's sub out is being EQ'd , by the look of the response but I triple checked. The near field measurements were done within about 1 inch of the subwoofers.

^^^^

Different mic? Slightly different mic position?

^Same mic. On the position - Good point. I just checked my notes from last year and it looks like I may be about an inch closer. Last year's measurements were about 1.5 inches away and this time I was only about 1/2 inch away. Do you think that could have caused that?

Yes. Even a complete novice such as myself was able to do pretty well, first with one sub and now with two (one in each channel - very cool).

I bought my DSP used. I'm pretty sure it's not manufactured anymore, but I haven't checked in a long time.

BTW, that's a LOT of filters. You'll actually only need half of them, but you'll play when you have the chance.

Entering them manually is no big deal, so don't get hung up on "downloading" to the DSP.

Well, it most definitely skewed your new measurements. Not sure it that's the issue, but you won't know until you duplicate the conditions exactly (which may me impossible to do being a year apart).

Yep, I'll have to try it. The thing that concerns me is that the humps seem to be showing up in my in room positions too. That is, when I started doing measurements this time around, I noticed a couple new humps (peaks) than the last time, which is why I was EQ'ing for my previous measurements. I realize I shouldn't expect the same exact responses but those humps look really odd and the responses on either side of the peaks look very close to the originals. But, maybe I am too close this time. One more thought: I did measure a speaker using the same sweep range and did not see any similar uniform humps and I was as close to the woofer. That made me think it was just the preamp out to the sub that was causing the problem. More troubleshooting tonight I guess.

Thanks. Did you create filters for each sub individually or for the two subs as a pair?

 

I'd probably go with the Behringer  FBQ2496 if I go this way at all as, I think, the other one is discontinued now, but they are essentially similar.

 

Do you use Audyssey or similar?  If so, did you apply the Parametric EQ filters before or after Audyssey?

 

Point taken on number of filters used - my aim would be to use as few as possible to get the job done - more fiddling would be needed.

 

I could enter them manually but the REW feature is just so cool!

I had one sub for a long time, and started with REW and the DSP with it. Recently added a Klipsch RW12-d. I have the old sub handle 80Hz to 40Hz (left channel of DSP) and the Klipsch 40Hz to 20Hz (right channel). Great results for mismatched subs in an acoustically horrible family room (open to one side, cathedral ceiling, skylights, the whole works).

 

Keep in mind that you don't need the fancy feedback features; you're just using the unit as a parametric equalizer. The 1124P used is <$100.

 

My Pioneer has MCACC, which doesn't do subs, so they are independent.

 

Fiddling is fun! And never-ending!

 

Enjoy.

 

Michael

Indeed. I snagged one from Guitar Center for 50 bucks.

Kbarnes lives on the other side of the pond, though, so availability may differ.

Thanks for the info. It seems I may be venturing into yet another rabbit hole...

 

Yes, the secondhand market for AV gear is very limited here compared with the USA. Mainstream gear from the major UK manufacturers like KEF, B&W etc is readily available, along with mainstream AVRs etc, but apart from that, stuff rarely comes up. But... I have found a new 1124P for about $150 shipped, so not so bad. Currently I am trying to convince myself that I do not want to travel this road! ;)  But...

If that's new (and US dollars), that's great! The other was almost twice that.

And no, you do not want to travel this road. You want to continue with the mediocrity that's good enough for everyone else.

I just sold mine to a fellow in Canada. Just missed the boat. Sorry. Not sure if this has been brought up yet, but have you looked into this: http://www.minidsp.com/

That would probably be the route I would go for subeq'ing.

^^^^

And, isn't MiniDSP based in Europe? Even a better option for KBarnes me thinks.

I think so. It's also REW integratable.

 

Well I wouldn't ay my own system was mediocre, or indeed that of anyone likely to be reading this thread, but I take your general point in the spirit in which I am sure it was intended. It's certainly another way to get the control over my system that I perhaps need, given the adverse nature of my room. 

 

I think a 1124P would be good enough - it only has 12 filters as opposed to the 2496's 20 - but who wants to use 20 filters!

 

Not looked into it - but definitely will. I am just (barely) on the first rung of this learning curve ladder so far... I guess I could always start a thread for 'noobs using parametric EQ with REW'.

MiniDSP is a Hong Kong based company equally far away from both sides of the pond. They have two distributors in Europe (Netherlands/ Norway). For EU members its best to order from the Netherlands dealer, their stock is already EU customs cleared, they just add up the Dutch VAT + shipping. In case of ordering directly from Hong Kong one would have to go to the customs office to clear the goods, stand in the queue and spend hours in an outskirt "office". Ordering from European dealer is much easier and comfortable coz they can provide the door-to-door service, unlike when ordering from Hong Kong.

Norway is not a member of EU, so same or similar rules (read: hassle) shall apply like for Hong Kong.

Sorry for the OT.

Keith, FYR Audyssey MultEQ XT32 has a filter resolution in the subwoofer channel equalling 512x. Well know fact. What we don't know is "x", coz it's industrial secret. OK, but then, let's assume x = 1, that means MultEQ XT32 has 512 filter taps (adjustment points) compared to just 12 filters (adjustment points) in a PEQ. But in case x = 10 that means XT32 has 5120 measurement points in the sub channel.

What do you think a 12 point PEQ will additinally do for you? 512 + 12 = 524, or 5120 + 12 = 5130, eh?

You may easily find yourself knocking on the door of Mssrs. L.D.M.
Edited by mogorf - 3/7/13 at 1:06pm

You could fully jump down the rabbit hole and get the MiniDSP 8 x 8 device, as well as the Advanced plug-in. Then you could have REW send filters for all 8 channels, not just the subs. You'd have to give up Audyssey, as both inputs and outputs are analog, but at least you can 'compare and contrast' the REW solution, which supposedly can optimize impulse response or FFT to taste.

http://www.minidsp.com/applications/auto-eq-with-rew

I suppose it's cheaper than high-level Trinnov

Sorry, by "everyone else" I meant the general public, as opposed to the fanatics here.

Frankly, I think the challenge I've enjoyed most is taking my relatively mediocre components and transforming the overall audio and video experience into something way beyond the sum of the parts. Which I would NEVER have been able to do without the help available here.

By the way, that's ONLY 12 filters PER CHANNEL!

You may want to call to see what "international shipping" would cost:

http://www.musicgoroundorlandpark.com/detail.aspx?id=1324105

Michael

Already done:

http://www.hometheatershack.com/forums/bfdguide/

Be careful with the Behringer items, i tried an 1124P and it introduced a, hum that i couldn't tame. I returned it and bought a MiniDSP.

"Difficulties of development" are always and immediately followed by "development of difficulties", eh? Nothing new, ces't la vie!

You can pretty much assume based on what Chris K. said here in the past years that x=32taps
You still can't compare FIR taps with PEQ bands. You can do much more useful stuff with 12 PEQ bands than with 32 taps of 2EQ... And even hundreds of taps will not be nearly as useful for low frequency EQ as just few PEQ bands.

 

I showed what it could do in the graphs I posted. If you want to see what I now KNOW it can do for me, not what I THINK it can do for me, on a FR that has already been EQd by Audyssey, here are two graphs:

 

 

 

 

 

 

 

 

 

 

The difference is clear to see. I know you believe Audyssey is perfect but I believe that it is good but far from perfect. By using additional tools such as REW and the 1124P, you can see what can easily be achieved.

 

EDIT: here's one with the two curves overlaid. Sorry the colours aren't very contrasty - I can’t figure out how to change the graph colour for the PEQ-d trace:

 

 

Edited by kbarnes701 - 3/7/13 at 2:54pm

 

I wouldn’t want to give up Audyssey. I'd want to use further EQ in combination with Audyssey in order to make adjustments that Audyssey fails to make to my satisfaction. I think, on brief research, that the Behringer DSP1124P would suit me better than the Mini-DSP, mainly because I think it would be easier for me to use. That view is subject to revision as I learn more about the Mini-DSP.

Yes, no offence taken :)  I agree with you entirely about the system being able to be greater than the sum of its parts, thanks to the application of hard work and some additional technology. I am finding the EQ section of REW to be utterly fascinating. Damn it, I came very close this evening to buying the 1124P just to play around with, but I restrained myself :)  I need to learn more first.

 

:)  Yes I have that bookmarked already :)  It doesn't do exactly what I am looking for though, which is sort of the equivalent of this thread but for EQ via REW only. I need to understand the fundamentals better before I jump in - although, HST, the 1124P is cheap enough to buy just to play around with and learn 'hands on' what can be achieved.