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Expert Help Needed!
I do not seem to be getting any low end out of my sealed DIY subs (see here for the build thread pics: http://www.htguide.com/forum/showpos...6&postcount=74 ). I moved the subs to a much larger room (35x14x9). I have experimented with positioning them around the room to no avail. Can someone give me some ideas on how to set up the DEQ to really boost the the freq. range from ~10Hz-20Hz? The parametric eqs. can only be set down to 20Hz so I have been playing around with setting a wide bandwidth boost at 20Hz to hopefully pull up the low end. It seems like I need more boost than the DEQ is giving me. Any ideas? TIA!!
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You can make a shelving filter to cut the higher frequencies in the sub's passband.Originally posted by InPhase
It's a bit difficult to offer any further advise without seeing some measurements of the in room performance
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson -
Use a high shelving filter to cut the highs. The pic is from the DCX software but the DEQ works the same. I set a filter at 200 so we can see what's going on on the graph but one at 20 would work the same way, at least down to the DEQ's natural low end cutoff (somewhere in the 5-10 Hz range?)Can someone give me some ideas on how to set up the DEQ to really boost the the freq. range from ~10Hz-20Hz?
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Here are Dennis' thoughts on using the DEQ to make a LT circuit...
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-BressonComment
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Thanks Thomas and Dennis. I used Dennis' guide when I orginally set it up, but later changed it. I believe I was trying to increase the output.
How do I get even more output below 20Hz if I start with a high shelving filter at 20Hz? Would either of you care to guess based on my design where I should place the high shelving filter? (I'm gonna start at 20Hz unless you guys tell me differently.) I have two 2x15" Soundsplinter RLps in sealed enclosures of about 12ft^3 volume each powered by an EP2500.Comment
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Start with the high shelving filter at the -3dB point of the driver in the box and cut from there. If one filter isn't enough, you can add another one at a lower freq. Do you have measurement gear? If you don't want to hassle with the whole computer/preamp/soundcard thing, the DEQ has a 1/6 octave RTA that isn't too bad if you have a mic to plug into it such as the Behringer ECM8000.Comment
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Close Mic'ed (1.5"s from a driver) graphs of the two subs:
I put in the high shelving filter x 2 and a wide boost at 20 Hz for a total of 3 filters to arrive at this response. They seem to drop off pretty fast below 14Hz. Shouldn't a sealed sub be more gradual? Also, sub 1's response appears fairly ragged, so I measured the driver on the other side and it was smooth. Not sure why that is.
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When you close mic there's no room gain to fill-in the bottom end.
Let's see a nearfield with filters compared to a listening position with the same filters.
Might use 1/3rd octave smoothing for both measurements...
IB subwoofer FAQ page
"Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-BressonComment
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What are the specs of the filters? Something doesn't look right. The uncorrected response is pretty flat from 40 to 100 but it slopes down after correction. Is that intentional?Comment
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I realized that the wide boost that I had put in at 20Hz was causing the downward slope at the higher frequencies. I removed it and got the response in orange (this is the average of both subs close mic'ed 1/3 smoothing). The two filters are both H12dB with -15 gain and at a frequency of 32Hz. I didn't realize that the DEQ could continue to make corrections even when they extend off the bottom of the screen. I had to add two more narrow cuts to tame a couple of huge peaks to arrive at the listening position response (in green with 1/3 smoothing) below. What do you guys think?
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That nearfield looks good! :T It looks like a good baseline to play with the room response with positioning, bass traps, EQ and all that stuff that drives everybody crazy.
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