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103db @20hz with 4 si18's...Is something wrong?

10K views 188 replies 31 participants last post by  Mfusick 
#1 ·
I spent the better part of a day playing around with REW to try and get the best curve I could. My room is horrendous. I finally got bass in the 50hz range as it was non existent before and I brought down the rest of the eq instead of bumping up the gains in the 50hz range. Long story short it does sound better and more balanced to my ears but taking the measurement at my listening position its still not nearly as loud as I would expect. I am using a umm-6 mic and made sure to DL the calibration file for it.

Measurement taken at my listening position, 3300 cubic foot room, AV at -0 and subs set to just below clipping. I have two subs in front and two in the rear of the room. Any suggestions would be great.

I am using two nu3k's, two subs are marty cubes, two are full martys.

Front subs


Rear

6

 

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#4 ·
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#7 ·
Makes sense. I was going to recommend playing with phase. Subs end up fighting each other quite a bit in multiple setups. I can change the db's by quite a bit by altering the delay by only fractions.
 
#13 ·
I highly doubt you are running sweeps at 134-140db.
The ULF spreadsheet says more like 116db@20hz@xmax. What does the box model say? Probably 20db lower, if that...
Are you sweeping at full excursion / full power or somesuch? :eek: (Somehow I doubt it.)
 
#14 ·
I changed the delay of three of the subs(one was closer than the others). If I am doing something wrong, I honestly have no idea what could it be set up wise. I will take another measurement tomorrow. I also turned off the AV from adjusting peaks previously it was set to Medium. It is much louder than before I will say, my second set of ears (wife) also agree, from down stairs.

She also had a dance party in the room after coming up to talk to me about it at -0.
 
#15 · (Edited)
When I was at jbrown's we did sweeps at 90db, with quad UXL-18 and dual 6000DSP's



The loudest thump of the day was How To Train Your Dragon, and was 113db @ 18hz, which was deliberately cranked up (but still running flat, no hotness applied).
That was (basically) as loud as anyone really wanted to comfortably go in a residence.


The average was more like ~105db.


Here is what 4 LMS-18's do at ~70mm of excursion @ 24hz with about 12,000watts of power.

Now this number is real, because TermLab's are accurate to within +- 0.01db.

(Note: All of this is unweighted)

Just saying ;)
 

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#16 ·
With 12 of my subs and something like 30kW, I get about 128db C-Weighted peaks on music-program at the front wall.

This song is heavy on the 23hz and 70hz thumps.

 
#20 ·
With 12 of my subs and something like 30kW, I get about 128db C-Weighted peaks on music-program at the front wall.

This song is heavy on the 23hz and 70hz thumps.

https://www.youtube.com/watch?v=IyVgtsl7hOo
You only get 128db in the upper bass with 12 subs and 30kw of power? I would think 140db + should be easy in the 40-100 range with that kind of fire power. Heck I hit 128db c-weighted on peaks playing heavy bass music with 3 measly 15" subs.
 
#28 · (Edited)
It is best to have a purpose-built SPL meter:

http://www.triplett.com/shop/sonichek/
http://www.parts-express.com/triplett-tsc-mc1-sonichek-mc-mini-sound-lever-meter--391-078
C Weighted reads 40-130dB from 31.5-8Khz 40db-130db
$38

http://www.galaxyaudio.com/CM130.php
http://www.parts-express.com/galaxy-audio-check-mate-cm-130-spl-meter--245-262
Resolution 0.5 dB
±2 dB (under reference conditions 94dB @1KHz)
125Hz to 8KHz
40db to 130db
$60

http://www.galaxyaudio.com/CM140.php
http://www.parts-express.com/galaxy-audio-check-mate-cm-140-spl-meter--245-263
The CM-140 and CM-150 meet the same IEC 651 Type 2 standards of SPL meters that cost 5 times as much or more.
Resolution 0.1 dB
±1.5 dB (ref 94dB @1KHz)
31.5Hz to 8KHz
32db to 130db
$130

http://www.termpro.com/storefront/termlab.asp
Competition Mode: 10hz to 100hz +- 0.01db @ 120 to 183db
NASA Mode: 2hz to 240hz +- 0.01db @ ~105 to 190db (not officially "certified"?)
$650

http://www.acopacific.com/mics.html
2 Hz to 40 kHz
20db to 160db
I'm afraid to ask: $1500+?
Bossobass owns one, and I think one was used for databass too.
 
#18 ·
He's got (4) SI 18" in Marty boxes so if he's thinking it's not loud enough something is probably wrong.

My guess is either:

Phase issue. (#1 suspect)
Room interaction issues (always a problem)
Reversed polarity
Reversed polarity inside amp (it's happened)

I'd start there. If you get some accurate measurements and decide it's still not enough then perhaps you are just a bass head :D. Build 8 ghorns and ride off into the ULF sunset.
 
#19 ·
The first step would be to post a rew graph scaled correctly. Vertical axis should be 5db incriments in a 45db range or so. Horizontal should be from 10-200hz. Start your sweep at MV-10, then -5, and -0. Post the graph with all three measurements overlaid.

To check REW spl calibration, in REW click the SPL meter tab, click calibrate, and a pink noise tone should start playin. Now place a c-weighted spl meter next to the mic and verify the spl reading in REW matches the spl meter. If not, you should be able to adjust the difference save/exit.
 
#21 ·
Also, I just ordered a nu6000dsp this morning (last one partsexpress had instock). I am kinda running out of space in my room to put subs. I could fit maybe two more martcubes OR should I use the amp and upgrade two of the drivers?

I tried to model out a SI HXT but think I was doing something wrong as it didnt look all that much better with twice the wattage compared to an SI.

Someone wouldn't happen to have the WinISD file of that OR maybe a sundown 15 or 18 V.3 or V.4?
 
#25 ·
Yes probably. But it's mostly a matter of phase. A horn is out of phase with a sealed about 90 degrees, a ported is out of phase with a sealed about 180 degrees. You can fix this stuff with DSP and calibration but it's just an extra step and thing to worry about.

Some the the very best bass systems on AVS mix, and have different kinds of drivers and or enclosures. I don't mean to suggest you can't do it, rather you'll need a certain level of understanding and commitment. It's not as simple and building a box and hooking it up. But I think you are starting to pass that level already with 4 marty boxes, so I could see you venturing into those waters.

lukedamdman has one of the better systems, he uses two GJALLARHORNS and two OTHORNS, and crosses from the Ghorns low to the Ohorns high...

N8DOG has Ghorns mixed with his 21" and 18" drivers- his system is excessive. Not the same drivers.

You can basically do anything you want, but it's about your level of commitment and desire for simple. Simple doesn't always translate to optimal. There is a reason why so many just grab a good driver in a sealed box, and then add a second to get louder. It's not because it's optimal, rather it's because it's simple. If it was simple to build folded bass horn or tapped horn and they fit easily everyone on this forum would have one.
 
#29 · (Edited)
If you ignore WinISD for a second and just look at the subwoofer's sensitivity and the distance and power by using this online calculator: http://www.crownaudio.com/elect-pwr-req.htm

You plug in your typical subwoofers sensitivity, a reasonable LP distance, and desired SPL and hit go.


143kW? :eek:
(Thank god for multiple subs and amps!)


How about 115db?

That's looking more human. Well within the abilities of 4 UXL-18's and two FP14K's.

13db of air pressure is bigger than most people assume.
 

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#31 ·
here is a prime example....look at the Chase SS18 with 1500watts vs LMSU with 4200watts at data-bass.com







The LMSU is a deep bass monster, not as efficient as several Eminence drivers in the upper bass. Most here are looking for deep bass output, but if you are wanting max performance above 40-50hz there are plenty of other options that will go way louder with less power.
 

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#33 · (Edited)
Very nice! Amazing setup you have!! To confirm with the above most spl meters tend to roll off starting around 30-40hz...at least that is what I have read, so that makes sense your term lab is showing +6db @ 40hz.

There is correction tables for the Rat shack digital, I believe it is down 3db @ 30hz, 6db @ 20hz, 11db @ 16hz....etc. From what I have read there is a capacitor mod that will fix the roll off...not sure about the cm-140.
 
#34 ·
BassThatHz, can you tell me if that cheap Triplett would be ok to use for setting the levels in REW to take typical measurements? What about the CM-130?

I need to find a way to properly set the levels in REW so that I can finally start to take some measurements, and my budget is extremely limited. If the Triplett or CM-130 will not work, then I will have to wait until I can afford a suitable SPL meter.
 
#41 ·
I do, just want an SPL meter, but, the primary and perhaps only use for it will be setting levels in REW. I want the cheapest tool for accomplishing this job!

So it looks like the Triplett is crap due to unknown inconsistencies, and the CM-130 won't work if it is limited to 120hz and up. So what is the cheapest way to go about this? (ie setting levels in REW)
 
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