[Guest]

Is there a point for me to even bother yet with my level of understanding?

I got a cheap checkmate cm-130 SPL, it really helped with balancing especial the sub & back speakers. I am learning more& more about treatments & traps. It's the math & practical meaning of terms that is throwing me. Basic concepts:Where and how to find 1st reflection pnts?
I am looking for a tutorial that not only shows me how to use wizrd, but how to apply it to room acoustics and speaker placements. A lot is taken for granted for knowledge. Which is fine, it looks like a good program but take a look below, the intial description of wizard and this symbol ? of what I dont understand:


Room EQ Wizard is a Java application for measuring and correcting room resonances. It includes tools for generating test signals, measuring SPL and frequency responses and automatically adjusting the settings of parametric equalisers ? to cancel the effects of room modes ?. It was initially written to help with the setup of the parametric TMREQ filters ? on TAG McLaren Audio AV32RDP and AV192R ?, but the latest version also supports the BFD Pro parametric filters? (with correct modelling of the effect of the bandwidth control?, which is quite different to the description in the BFD manual? ).

Measurement is stepped sine?, with local loopback? for soundcard response compensation and DFT ?to isolate the measurement frequency. Log swept sine measurement? and impulse response extraction ?are on the dev list but some way off. The Wizard can also import measurements in the ETF export formats? or from text files in a basic comma-delimited format - details are in the help files, which can be browsed online at the site and are included in the program.

The sig gen? provides sine waves to 0.1Hz precision?, sine sweeps (linear and logarithmic)?, square waves and various pink noise signals including "full" range (pink spectrum down to just below 10Hz?), speaker cal?, sub cal ?and custom filtered? to suit your needs?.

Note that the app requires V5.0 or later of Sun's Java Runtime Environment (JRE) to be installed, available from http://java.sun.com/j2se/downloads.html

Hope it proves useful.

Well..... :scratch:

 

[brucek]

Is there a point for me to even bother yet with my level of understanding?

I got a cheap checkmate cm-130 SPL ??

parametric equalisers ?

Here is the BFD Guide on the parametric equalizer that is referenced on this site. It is an inexpensive equalizer designed to modify the signal between the subwoofer-out signal of a receiver/processor and a subwoofer. Subwoofers tend to have poor frequency responses created by resonances in a room that we want to repair with an equalizer (you know what that is). This is a special equalizer that can modify all the 'parameters' of its internal filters (gain, bandwidth and frequency parameters).

room modes ?.

Without getting too crazy in an explaination, at low frequencies subwoofers react in a room rather poorly, and exhibit a frequency response that isn't flat or desireable. We need to measure that response and then apply a filter(s) to modify the response to make the subwoofer sound better. We accomplish this by modifying the signal that passes to the subwoofer. We simply use the REW program to help us set up the filters in the BFD.

TMREQ filters ? on TAG McLaren Audio AV32RDP and AV192R ?,

Ignore this. It gives a history of why the REW (Room EQ Wizard) program was invented. These are model numbers of home theater processors.

BFD Pro parametric filters?

Since you've read the BFD Guide now, you're an expert on what this means....

Measurement is stepped sine?

This is a method of measuring a frequency response in a room. We transmit SINE waves at increasing frequencies and it helps decide on filters to enter into the BFD.

with local loopback? for soundcard response compensation and DFT ?

The REW program is run from a PC (you know what that is) soundcard. Soundcards exhibit poor frequency response. We compensate for that poor response by a method called local loopback to make the soundcard theoretically perfect to remove it from the equation.

swept sine measurement? and impulse response extraction ?

Cool REW features you can ignore at this point.

ETF export formats?

REW competition. It can read their files....

The sig gen? provides sine waves to 0.1Hz precision?, sine sweeps (linear and logarithmic)?, square waves and various pink noise signals including "full" range (pink spectrum down to just below 10Hz?), speaker cal?, sub cal ?and custom filtered? to suit your needs?.

REW produces a bunch of different types of signals to help in determining the frequency response of your subwoofer in your room and recommend filters to enter into the BFD.

Note that the app requires V5.0 or later of Sun's Java Runtime Environment (JRE) to be installed,

REW won't run unless you download a program from a company called SUN.

Any more questions?

brucek

 

[Guest]

:T wow, thanks for the effort. :T

Ok so basically, rew just helps make a filter or settings for an equalizer for your subwoofer?

People don't look at these readouts and go, " Oh I see I need acoustic panels here in the room to compinsate for this spike in the graph? Oh i can see modes here in this readout, I need bass traps here and here.

I am serious, I feel soooo dumb but it is like reading a cook book and not knowing what measurings spoon,blenders, ovens, etc.. are. U have a idea what a knife is, but how do you use it to and end up with a 3 course meal?

I am having serrouse problems with very harsh mids and highs..i have gotten a lot of help from other av forums (TREATMENTS! TREATMENTS!), and I am just making panels now, i have placed them all over the room, and notice a big diff buy not exceptional, but I would like tools that would actually help me do it right, and not have me hang all of them up and never get the best sound i could. i though eq could help. I am sure I have probs with the bass, I just can't tell yet.

 

[brucek]

I am having serrouse problems with very harsh mids and highs

The REW program is quite capable of checking the full range (10Hz to 20Khz) frequency response of a room and could be useful for speaker and room treatment positioning effectiveness. Generally in this forum we are using REW to monitor the response of the range covered by a subwoofer (10Hz to 200Hz).

The parametric device (BFD) that we use is very inexpensive and as such is only suitable for low frequencies. For full range treatment you need to use treatments (such as you're already into).

brucek

 

[mike c]

on the same note ... what about treatments for bass? what about terrible dips ...

 

[pepar]

on the same note ... what about treatments for bass? what about terrible dips ...

IN order of preference for dealing with room modes to flatten bass response:

1. Subwoofer position
2. Acoustical treatments (bass traps)
3. EQ (parametric)

Terrible dips are caused by the same thing as terrible peaks - certain frequencies, determined by room dimensions, that resonate (think "organ pipes") between room surfaces, back and forth, to and fro. Where they "meet themselves" in phase, they add and cause a peak. Where they meet out of phase, the cancel causing a dip. Sub positioning can be used to excite as few room modes as possible minimizing peaks and dips. Understandably, not many of us can put our subs in the best position, but we can locate what I refer to as the least worst position. Acoustical testing software can aid in finding that position. Next up is installing bass traps, which can make a HUGE difference by absorbing bass frequencies and preventing them from resonating in the first place. (Why not have bass traps as the first thing on the list? Moving a sub is free; bass traps are not.) Preventing room resonances prevents peaks and dips. Finally, a parametric EQ is used to put the finishing touches on the room response.

What was the question?

 

[Sonnie]

Terrible dips are terrible yes! I hate it when that happens.

Keep in mind a couple of things about bass traps. Most of your cosmetic appealing bass traps don't do much below 80-100hz. I remember one of Ethan's test where he had several (and I mean several) bass traps standing around his room. There was very little, if any (I can't remember exactly), effect below 80hz. And those weren't very cosmetic appealing either. That doesn't mean that the area above 80hz is not important though... but we are mainly focusing on subs here. Monetary cost might play a factor in this too... for several folks who are looking for the cheapest method.

I have heard of bass traps that tamed frequencies below 80hz, but they took up nearly an entire back wall and it was lots of trial and error and very costly to strategically target a particular response peak.

So for sub 80hz and below... I might would stick the parametric eq back to #2. lol

 

[pepar]

Keep in mind a couple of things about bass traps. Most of your cosmetic appealing bass traps don't do much below 80-100hz. I remember one of Ethan's test where he had several (and I mean several) bass traps standing around his room. There was very little, if any (I can't remember exactly), effect below 80hz. And those weren't very cosmetic appealing either. That doesn't mean that the area above 80hz is not important though... but we are mainly focusing on subs here. Monetary cost might play a factor in this too... for several folks who are looking for the cheapest method.

I have heard of bass traps that tamed frequencies below 80hz, but they took up nearly an entire back wall and it was lots of trial and error and very costly to strategically target a particular response peak.

So for sub 80hz and below... I might would stick the parametric eq back to #2. lol

True, a sub's output is almost always 80Hz and below, but "bass" extends a few octaves above that. And the PEQ is usually only on the .1, which leaves acoustical treatments as the best way to deal with the 100Hz - 300Hz range.

Right-o as well on the "cosmetically appealing" issue; unless one is starting from scratch with a large empty space allowing integration of a huge trap (or traps) into the theater design, tacking things onto walls and corners is the only thing to do. StudioTips SuperChunks - the 34" face design, is effective into subwoofer range, but are awfully huge. And covering them with GOM doesn't make 'em any smaller either!

I bought some OC703 and am working on building the 24" face version. By doing both wall corners and the wall/ceiling corner behind my false wall, I'm hoping to minimize the traps needed in the room itself. The 24-inchers don't get as low as the 34's, but most of my problems are 100Hz - 300Hz, and if I can get some low bass absorption, EQ'ing will be that much easier. Sooo, your conclusion is pretty much right on for subwoofer frequencies.