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Discussion Starter · #1 ·
Hi,

I have another post where I went into much more detail. I have deconstructed my room somewhat; taken down some bass traps, but my problem doesn't go away unless I point the measurement mic to the ports of my JBL 4410As; then the response is fairly even from 45hz to 10khz. However, as it stands, from most points in the room between 45hz and 150hz, I lose about 10dbs (and even more at some frequencies). Above 150hz, the room is relatively flat and my waterfall graphs from 150hz to 500hz look great. But the SPLs below 150hz are, like I said, shy 10db and more, and is reflected in my waterfall graphs. I have floor to ceiling bass traps in three corners; I removed some of those, but it didn't change anything. It has been suggested I get a subwoofer; however, I have read that in a room that eats bass, that will just make things worse and besides with ported JBL 4410s with a 10" woofer and a rating of +/- 2db from 45hz to 22khz, I should be getting enough low end, so adding a subwoofer would probably only heighten the problem, because from all my research, if I simply try to generate greater decibels in that frequency range to make up for what the room is doing, I'm going to end up with lots of standing waves and more problems than I will solve.

So has anyone dealt with a room with a problem like this before? If so, what kinds of solutions besides adding more bass, did you try; and, more importantly, did anything work?

I appreciate it if you could give advice along the lines of my questions.

Thanks,
Wade
 

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Hi marsx,
I couldn't seem to find your more detailed post, so I'm not sure of your use case, or your room, so with that in mind, I'll try to help. As to the recommendation of a subwoofer, I'm going to echo this. I have 12" drivers in my mains and 8's in my surrounds and I would never consider going subless. Your going to free up a lot of headroom by not asking your receiver to push the low frequencies allowing more dynamics while at the same time, if you get the phase, and crossover right, smooth the low end instead of making it worse. Also, placement can go a long way to even out a bad response curve. Every room in the world will have modal issues, so don't be afraid of making them worse.
If any of this is not applicable to your situation, please disregard as I've not seen your other post. As to my own experience. I had a pretty big dip at 50hz that I fixed(mostly) with speaker placement and phase settings on my subs. I've added a 3rd sub and it helped to fill the dip even more. (Planning for #4 soon) I hope this was useful!
 

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Discussion Starter · #4 · (Edited)
Okay,

I have a question, as stated in my initial question in this thread, when testing my Jbl 4410As in my room from 45hz (the speaker's published low end freq. response) to 22khz, I find a consistent decibel deficiency beginning at 45hz of 12db (-12db) or more which slowly rises in a steady logarithmic fashion (excluding occasional nulls) to a deficiency of about 6dbs-8dbs (-6-8dbs) at 150hz. From 150hz on up to 15khz the response remains relatively even maintaining my target frequency of 85dbs, give or take a few dbs and excluding occasional peaks an nulls.

So I had a thought - how about testing the speakers as subwoofers since they are designed to be broad range speakers (made and designed before anyone considered the idea of subwoofers). So I recalibrated REW as if taking measurements of a subwoofer and then I took measurements of my JBL 4410As and lo and behold, no bass deficiency below 50hz!! I measured from 15hz to 250 hz and found that the low end of the speakers achieved roughly 83dbs by 50hz and fluctuated a few decibels up and down right up to 250hz. Of course, I had a couple of narrow nulls, but my waterfalls looked good too, no standing waves, everything from 15hz up to 250hz tapered off at just under 175 ms, pretty consistently across the range.

So what am I to make of this??? When I measure the speakers as full range, the speakers are up to 12 dbs below baseline (85db) up until 150hz and then roughly normalize for the rest of the range up through 22khz; Literally -12dbs up until about 80hz, then moving slowly and logarithmically up to 85dbs at 150hz, but when I measure them as subwoofers, I get a completely different perspective on their response. Does anyone want to comment on this an offer their interpretation? Is REW just lousy at gauging full range speakers? I.e., what gives??

Wade
 

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Discussion Starter · #6 ·
Thanks for the response. Nope, that is the JBL 4410 studio monitor; I've got the Jbl 4410A, which is basically the same speaker with same specs, except they left off the knobs to help you control the speaker in a given room. Just my luck; probably saved me $200 twenty years ago, but I wasn't even aware there were two models; this was the model that was on display and that i heard and liked (and there was no internet to quickly and easily check on what else was available by JBL in the price range I was looking in. C'est la vie.

Thanks.
 

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I'm guessing that since the only thing that changed was how your measuring, it's in the setup. I thought possibly that you may have engaged your crossover somehow too... Have to go to work. I'll ponder. Wayne?
 

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Discussion Starter · #8 ·
the main thing I noticed is that when you calibrate for subwoofer, the pink noise you calibrate with is made up of much lower frequencies which required that ?I really increased the gain of my output signal to reach the proper level on my SPL meter; i.e., the content of the low frequency pink noise is much quiter in mt system calibrating for subwoofer than the higher end pink noise content output when calibrating for full spectrum speakers; perhaps a function of, and therefor a problem in, REW?

Just a thought.
 

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Discussion Starter · #9 ·
FYI, crossover frequencies on the JBL 4410A are 900hz and 4khz; I don't know how that would affect two different calibration choices. When calibrating for "Subwoofer" REW generates pink noise made up only of very low end frequency content, requiring much higher gain settings from my system, then when I do a measurement from 15hz to 250 hz, the measurement reaches 85db at about 50h. However, when calibrating using the "Main Speaker" setting, the pink noise generated sounds like it is made up of much more broad spectrum, or at least much higher spectrum content and I have to reduce gain a lot to calibrate. Then when I measure the same frequency range of 15hz to 250hz, the measurement doesn't reach 85db until 150hz rather than at 50hz. This seems to me a flaw in the design of REW. I don't know how else to explain it. Because if I thought maybe if the overall output of the "main speaker" setting was calibrated at the high gain settings used during subwoofer calibration, the gain of the higher frequency pink noise content is EXTREMELY loud, though I didn't measure exactly what it was or calibrate using the louder content. Later today I could put earplugs in and try to figure out how high the SPL is when using the gain settings for "subwoofer" calibration when calibrating for "main speakers," assuming I can calibrate at that high gain. I then could take a measurement and see if it changes the way the low frequency responds. However, since I don't know what the pink noise content is when calibrating for "main speakers" I don't know how that calibration affects the actual measurement.

Any ideas would be greatly appreciated. Also, I don't know if you read that I am using 5.0 because the newest beta version crashes every time I select the ASIO drivers for my audio card, the LYNX L22 (I don't know if the beta version's calibration settings are different, but if they are, I'd love to try the new version; however, I posted my ASIO freezing problem on a different thread and, as yet, have received no response).

Wade
 

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How big is your room? Is it open to other areas?
 
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