My Subs response Graph

fuel2000

Active Member
Hi

Been trying to get to grips with REW the last couple of days as i've got a BFD coming in the next few days, and i finally got a graph out it.

Now what does it mean? Will the BFD help it and make it better?

Thanks in advance.
 

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mattkhan

Distinguished Member
it looks like you have big peaks around 35Hz, 42Hz & 75Hz and that (as a result?) you have the sub turned down. A BFD should help you tame those peaks and let you turn it up quite a lot. The way it falls off a cliff beneath that 35Hz peak looks odd. Have you tried different positions?
 

Member 96948

Distinguished Member
My thoughts exactly. A Monolith should extend down to at least 20Hz in room. Peaks are dominating big time. You haven't heard how deep the Monolith goes yet, so once you've mastered it, the BFD is going to give some fairly spectacular results.

Russell
 

Fjorko

Active Member
My second Monolith is being manufactured as we speak !:thumbsup:
 

Member 96948

Distinguished Member
Try plugging those dimensions (plus the height of the room) into this.

If it is confusing, try putting in just one dimension at a time setting the others to zero. It's quite enlightening as to which peak is caused by what.

Russell
 

simonoaks

Active Member
Try plugging those dimensions (plus the height of the room) into this.

If it is confusing, try putting in just one dimension at a time setting the others to zero. It's quite enlightening as to which peak is caused by what.

Russell

it is all confusing, 1, 2 or 3 numbers entered, it just generates a load of (to me) random frequencies that mean nothing and it does not explain any of it :)

Think I need to come back to learning about subs, when I am ready to buy one !! :suicide::suicide:
 

bob1

Well-known Member
That curve looks wrong to me ,I've only use rew a few times so i'll let someone with more experience respond further.
 

Badger0-0

Distinguished Member
Nah, cut those peaks by around 15dB, add a hint of boost, then turn it up a bit and that will be quite nice, IMO.

Surprised by some of the lows though :confused:

Looks ideal for placement experimentation, to me.

The BFD will improve that response, big time :thumbsup:
 

Member 96948

Distinguished Member
it is all confusing, 1, 2 or 3 numbers entered, it just generates a load of (to me) random frequencies that mean nothing and it does not explain any of it :)

Think I need to come back to learning about subs, when I am ready to buy one !! :suicide::suicide:
Put your room length into the first box.

5m gives room modes at 34.4Hz and second harmonic at 68.8 Hz. Ignore the rest because they're too high in frequency to matter.

If you are suffering a peak or trough at those frequencies (and you are) then movement of either the sub or youself up or down the length of the room will affect a change to those modes.

Remember, these effects are localised to specific areas of the room. The higher the harmonic the more often the mode happens, but at a reduced potency. Moving a small distance may move you out of the effects of that mode, or help ameliorate the effects of a bigger one.

The same goes for width, except of course we're now talking about movements across the room.

There's not much you can do about height and trying to figure out tangential modes will make your head explode. What you are looking for is normally across the top of each table and that is frequencies that are repeated or very close to each other especially if they're below 100Hz.

Repeating frequencies either are either additive (give a really big peak), cancelling (make no difference), or destructive (give a really big dip).

For instance you have a combined peak at 68.8 & 71.6Hz which are shown in the Axial Modes of the calculator and in your REW graph. Either peak by itself is probably not quite as big as shown, but the overlap gives a boost to each. When you get your BFD it would be tempting to create a filter at 70Hz to squash 'em, but two less savage filters at 69 & 72 Hz may do a better job and sound better.

If a trough fails to disappear whatever you try, there's nothing you can do about it and certainly don't try using the BFD to boost them if they're below 40Hz. They can be caused by openings into othe rooms, chimneys or alcoves. Unless you fancy rebuilding, they're normally there to stay.

Its all about looking at different pictures to gain an idea of whats going on. I'd use the room mode calculator plus REW to do what you can in terms of positioning before the BFD is introduced. EQ is very handy, but less is always more with audio.

Russell
 

simonoaks

Active Member
sO,

In the real world, I buy (probably svs sub), plug it into amp and place it where I would like it (athetically, right next to wooden cabinet in same finish). I then type in my room dimensions (L16ft/W12ft/H8ft) and it will then show me where problems will be ?

Does this mean that you can preject issues before installing kit ?
 

mattkhan

Distinguished Member
it shows you where problems are likely to be concentrated. The calculator is based on a box with the dimensions you provide but the typical room is not perfect box and is filled with things that distort the shape hence real world experience can & does vary from the theoretical prediction.
 

simonoaks

Active Member
so the best thing , is to not worry too much about it, chuck it where I want and enjoy. I guess, with a top amp, speakers, source and sub, it will sound fantastic anyway and I probably couldn't tell any minor differences anyway ?
 

mattkhan

Distinguished Member
so the best thing , is to not worry too much about it, chuck it where I want and enjoy. I guess, with a top amp, speakers, source and sub, it will sound fantastic anyway and I probably couldn't tell any minor differences anyway ?
it really depends on the sub & where it can realistically go in the room. In my room there really is only one place it can go and that is next to the cabinet between the front speakers. This happens to be approximately at the room quarter point (which IIRC russ.will has posted about before, I forget the reasons why this is a good spot). Fortunately this is theoretically a good position and my room is ~14' * 12' * 10' so no repeating modes and it has assorted features that break up the space somewhat (see pic).

lounge.jpg

One might therefore expect that a sub in such a room wouldn't be subject to serious peaks & troughts and in general this turned out to be true. However there is still an audible difference between the raw sound & the EQed sound so a BFD & REW were still good things to have.

Ultimately though I have all the tools required and know how to use them so it's a no brainer for me to run a sweep and EQ the sub as a matter of course. Once you're used to the software/BFD then it takes a matter of mins to see what the sub is doing in room so why not do it?

Cheers
Matt
 

fuel2000

Active Member
Well got my BFD and midi cables today so here are the results of my first mess around with it. Still trying to understand the BFD have read up a bit more i think. Well heres my graph.

Its definetly better than the first, and sounds a lot a better less boom more punch and you can feel it alot more lower down!!

What do you guys think of it?
 

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mattkhan

Distinguished Member
for comparison it's best to use the same scale on the graph & 45-105dB & 15-200 (which you do have) are usually advised.

is that a corrected response? it looks quite quiet to me & does that ~75Hz peak respond to cuts?
 

simonoaks

Active Member
better go find out what BFD and REW is. And then I might be able to make sense of all those lines on the graph and what they stand for/represent and what is a good/bad result !:suicide:
 

Member 96948

Distinguished Member
Its definetly better than the first, and sounds a lot a better less boom more punch and you can feel it alot more lower down!!

What do you guys think of it?
Definitely heading in the right direction.:smashin:

When you're next 'tweaking', just go right ahead and turn the sub up until the area between 22-30Hz is on the line. This will result in the remaining peaks being well above it, but that's what you bought the BFD for. Do this and you'll be amazed how deep and how tight your bass sounds.:devil:

One thing though. Give yourself time to adjust to each round of tuning with a good lengthy period of listening in between tuning sessions. Give yourself time to enjoy and understand, each inprovement. It's easy to get hung up on flattening every last bump totally when anything inside of +/-2dB of the line is inaudible.

Russell
 

fuel2000

Active Member
Thanks guys.

Yep thought that 20-30 area should be louder, will play more tomorrow.

Can't believe how much better it sounds already.:thumbsup:

Had a chance to listen properly now, wow the sound is so much deeper you can feel it in your belly, and now i know what people mean when they say their sub pressurises the room.

Not going to play any more now till next weekend though as i'm having a wooden floor laid next week which will undoubtbly change the room response (and now i'll actully be able to see how!!)
 

Nimby

Distinguished Member
Check the mains plug is tight in the back of the case.
Mine has fallen out twice. Makes a hell of a bang in the speakers so switch everything off first before giving the plug a wiggle.
Otherwise it's back to the dealer. (if any)
 

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