New JL fathom 113 Graphs

I just got a new jl fathom 113 and i was running a ton of tests... the one question i have is i have an old digital RS meter and not sure which file to use... i will post both my graphs using the oldanalog and the digital calbration files... the first is the old analog cal file... the second is with the new digital cal file... i'm just not sure which one to use... i don't know if one looks better then ther other or what... also what would help me with those big dips at 140hz and there is another one at 190hz when not smoothing...

I also set the ELF trim to -8db wich i'm starting to think maybe i shouldn't have set it so low???

[Wayne A. Pflughaupt]

Hi Craig,

You might want to check the info on this thread. It looks like you’ve done a linear graph rather than a logarithmic graph. Try redoing them, and things might not look as bad.

Regards,
Wayne

ok i must have hit that by accident... do i just need to redo the graphs or the actually measurements???

also i'm not sure where my target line is supposed to go... it set it while i took the measurements but then when i saved it didn't save....

alright i changed the graphs...

[brucek]

the first is the old analog cal file... the second is with the new digital cal file... i'm just not sure which one to use.

With regard to the cal file for the meter, read this thread here.

help me with those big dips at 140hz and there is another one at 190hz

Normally we first measure the sub with the mains removed to check its response and then equalize or move the sub around to get the best result. Then we add the mains (as you've done) to see the interaction around the crossover region. Any dips at the frequencies you've mentioned are a mains problem and we don't generally equalize that area. You can try repositioning the mains to help with their responses.

brucek

i know u can't equalize stuff from the main... i'm just wandering about things like acoustic panels , bass traps... i don't think i plan on EQing the sub other then with the ARO that came with it i was just getting some opionions.... on the results of the graphs and the interactions between the sub and mains...

[Wayne A. Pflughaupt]

Acoustic panels are for taming upper-frequency reflections and therefore won’t do anything for subwoofer response. Depending on your room you may not need them at all. If you have a carpeted floor, over-stuffed furniture, draperies and the like, you probably don’t need any. However, if you have a hard floor they can certainly be beneficial.

Bass traps are to the low frequencies that acoustic panels are to the highs – they absorb reflections and reduce low frequency decay in the room (also called [for some inexplicable reason] “ringing”). REW has a “waterfall” setting that will show your bass decay. Traps would improve what you’d see with the waterfall graph. As a result, your bass should sound much tighter. However, traps generally can’t deal with ultra-low frequencies.

Traps can reduce response depressions, but are deficient when it comes to eliminating most peaks. Here are some examples from Ethan Winer’s legendary Real Traps Vs. Equalizer showdown:


No Traps or Equalization



17 Mondo Traps With No EQ



EQ Only



We can see that the traps did reduce the peaks and dips some. Overall, it would be realistic to say that equalization blew away the traps. However, look at what happens when we add the time domain:


No Traps or Equalization



17 Mondo Traps With No EQ



EQ Only



As you can see, the traps practically brick-walled decay – above 50 Hz at least. Equalization not only smoothed response, but appeared to reduce the decay as well. However, that’s just a side effect of the worst peaks being reduced by 10 dB or more. Once you turn the sub back up to compensate, the decay at the peaks be the same as it was before equalizing.

Here are a couple of charts with both EQ and traps:








As you can easily see, traps with equalization gets you the best of both worlds – reduced decay (above 50 Hz), and smoother response.

It should be noted that there were some conspicuous problems with this showdown, so take these charts as “general information” only.

The traps used weren’t optimal for the lowest frequencies.

And the equalizer was very poorly utilized, in my opinion. They took readings at 28 different locations, but only applied a single set of EQ filters. In other words, the EQ wasn’t tailored specifically to these charts. Additionally, very poor equalizing technique was employed. You’re seeing the results of twelve filters in the EQ graphs, and as you can see it still looks pretty bad. Nine of the filters were 1/24-octave or even less! A few others were only 1/12-octave. Ultra-narrow filters like that are seldom called for, and certainly not as the overwhelming majority of filters needed. Additionally, a few filters were erroneously applied (read "wasted") out of range of the chart. All in all, it’s miraculous the EQ graphs show any improvement at all.

In other words, proper equalizing and trapping should yield better results for both response-smoothing and decay than you see here (at least if you can accomodate countless traps).

And perhaps most egregious, no subjective listening evaluations were performed.

Regards,
Wayne

[Wayne A. Pflughaupt]

Well, the second graph looks the best. Notice that re-doing the graph shows the 160 Hz null is actually too narrow to worry about.

Not quite sure what you’re wanting from us at this point. Advice on sub placement? Pointers on remodeling your living room for best acoustics?

Regards,
Wayne

sorry if i'm being a little vague... i was just asking about diff spots to place the sub in... i know with the fire place and it being an open room it can be very troublesome... i was wandering how much things like bass traps and accoustic panels would change the sound... my speakers tend to me to be a little bright... i would like to turn my system up a little more for more bass but then the speakers just sound to bright... i have a 2496 but i think i'm gonna use it in my basement because it is a much more sealed room...

[Josuah]

Your room looks very reflective. I bet there's a lot of echo when you have people over. That might be the annoying sound you're describing as bright. Not sure how well those speakers handle loud though, they look pretty flat unless they're actually in-walls and not on-walls? It could be you're just driving them to crazy levels of distortion. I couldn't find any real information on the speakers.

I'd pick the second graph too.

[Wayne A. Pflughaupt]

i was just asking about diff spots to place the sub in... i know with the fire place and it being an open room it can be very troublesome...

Actually open, irreguglar rooms are more beneficial to response than you might think.

In the upper frequencies they do a better job of breaking up and “randomizing” reflections (assuming the wall directly perpendicular to the speakers isn’t a solid, unbroken expanse of sheetrock).

With the lower frequencies you usually get more uniform response throughout a wider area of the room. Sealed symmetrical rooms tend to have a low frequency dead spot in the center of the room, and bass levels increases the closer you move from that point to any boundary. So, response varies greatly from seat to seat.

i was wandering how much things like bass traps and accoustic panels would change the sound...

Traps were discussed in my earlier post. Acoustic panels, if there are enough of them decrease reflections - some people say they tame high frequency response in a highly reflective room, but I don’t really buy it. If your reflections are bad enough, dampening them attenuates all the high freq energy bouncing around the room, which can be perceived as taming the highs. However, there won’t be any change in direct-radiating response between the speaker and your listening position. I agree with Joshua that your room looks fairly reflective. The rug on the floor isn’t all that big, plus a significant portion of it is covered by the hard table. So, acoustic paneling might indeed help “tame” the highs. That said...

my speakers tend to me to be a little bright... i would like to turn my system up a little more for more bass but then the speakers just sound to bright...

You could gain a lot of mileage in that department simple by adjusting your receiver’s treble or high frequency tone control.

Regards,
Wayne

[Ilkka]

I would use the correction file for digital meter with this one. I doubt the true frequency response is as bottom heavy as it is with the analog correction file.

yea i just saw that one article back in 1996 where they both were the same but i guess he used diff numbers for the calibration... i don't know i'm getting a galaxy 150 so i don't have to worry about it... here is the article so i'm unsure what to use for my digital meter since i purchased it in 1999 or 2000...

http://www.hometheatershack.com/foru...l+rs+spl+meter

i am just thinking about whether its worth spending the money on some of those GIK accoustic panels... i talked with a guy that does the design over there and he recomended two 244 on the front wall and 2 on the corners left and right of the front wall... then 3 242 on the back walls...

just wandering if its worth it and what kind of benefit i will obtain???

[Josuah]

Try close-mic'ing your decay measurements and placing your sofa cushions to prevent the sound from getting to your walls/ceiling/floor or something. Then you can tell the difference between the decay due to the speaker and the reflections.

The information on the manufacturer site isn't much, and the 125W peak doesn't say if that's with 50% distortion or 10% distortion or 1% distortion. The reason I mention it is the speakers that came attached to my TV can also play somewhat loud but it sounds horrible because it's incredibly distorted. That might be what you're describing as "bright".

i'm not sure exactly what u mean by close mic'ing the decay measurements...