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dude, where's the final pics. If youre holding out till u can make it "pretty", come on man... we've all seen naked enclosures. I'm not gonna ride you about vids, I can let that slide, but come on can we at least see sime final 21" in-box pics please?
 

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Discussion Starter #82
Well, how I have it positioned in the living room, you don't see the driver because it's pointed towards the front corner. I'll have to pull it out tonight and take some photos of it. I should get off my butt and find my mixing board and mic so I can measure it as well...so I'll get some photos tonight.
 

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can't wait to see some pics! Have you listened to any music and watched anymore movies? How is your impressions today with more listening time?
 

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Discussion Starter #84 (Edited)
My fiance was out of town over the weekend, and I got her parents to take the (very large) puppy so I could get some work done around the house. I started working on running 3/4" conduit from the mains panel towards the home theater, but the main reason I was working all weekend was to strip wallpaper, paint, and overall "refresh" the fiance's bathroom as a surprise. I'm really beat...and I realize I hate oil based primers....

That said, in between contact highs of two coats of oil based primer, I watched a couple older movies and a couple newer (non-action) movies. The sub fills in very well no matter how I used it. I also listen to a bunch of electronic and ambient music while I painted, and again, the M-21 really fills in the bottom end well without overpowering the rest of the system. I've also watched a few episodes of "V" and "Heroes" and "Flashforward"...I guess I'm getting so used to the sub really adding depth to everything I watch and hear, that I forgot how weak the really low end was with my old sub. I find myself catching sub-20Hz ambient and percussive sounds that I never knew where there before!

All that said, I'm a bit concerned with the "speed" of the woofer. "speed" as always been described to me as the speed at which the sub can change pitch, keeping up with the mains. The larger the sub, the less speed it typically has and the more it seems separate from the mains. The M-21 seems to blend well with the mains, but doesn't seem to do so as seamlessly as my folded horn did. And there are people on both sides of the fence on if "speed" really exists or it's just audiophile mumbo-jumbo.

Again, all this is just my impressions from casual listening...I hope to know more, and get some guidance after I take some measurements. This weekend was just not the time for measurements, though I did get a couple photos I'll post up tonight...I just need to download them from my camera.

Also, for those that were asking about videos...I'm going to borrow a cheap point and shoot that has some basic video capturing capabilities, and see what I can get out of that. It may take me a bit to figure that out, and I don't believe my online photo gallery will accept video...so I may have some work there as well.

I'll update as I have something solid to show.
 

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Discussion Starter #86
sounds great thanks for the update. If you had to do it all over again would you change your mind on what you have now?
It's hard to say.

Kevin recommended 12 cu ft, and I went more like 16 cu ft, well beyond the point of diminishing returns, but not quite large enough to go LLT cabinet. Sometimes I feel like I should *feel* more output below 20Hz, but maybe I'm just expecting too much (due to my large room with connecting hallways and stairs that I can't close off).

I'd love to have tried an M-18 in LLT and directly compared it to my M-21 sealed.

Again, I've not taken any measurements...so my wanting more 15Hz could just be me not really understanding what 15Hz feels and sounds like. Maybe I have PLENTY and I'm sitting in a dead spot. So till I get measurements and make sure I have the best sub placement, I really can't say if I built the perfect sub for me, or if I should have gone with Steve's suggestion of an 18" LLT, or other suggestions of tapped horn, or dual 18 sealed or so on and so forth.

I'm not disappointed, I'm just wondering what difference I would get in an 18" LLT. And if I had the cash, I'd build one just to compare and sell what I thought didn't suit me as well. :wave:
 

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All that said, I'm a bit concerned with the "speed" of the woofer. "speed" as always been described to me as the speed at which the sub can change pitch, keeping up with the mains. The larger the sub, the less speed it typically has and the more it seems separate from the mains. The M-21 seems to blend well with the mains, but doesn't seem to do so as seamlessly as my folded horn did. And there are people on both sides of the fence on if "speed" really exists or it's just audiophile mumbo-jumbo.

Again, all this is just my impressions from casual listening...I hope to know more, and get some guidance after I take some measurements. This weekend was just not the time for measurements, though I did get a couple photos I'll post up tonight...I just need to download them from my camera. .
It's likely to be the blend between the sub and mains, or the room, or the overall FR could have a resonance somewhere. It's possible that there is a bad enclosure resonance sometimes, but probably not the driver/cabinet itself. When you get around to investigating that it'll probably show up somewhere.:T
 

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It's hard to say.

Kevin recommended 12 cu ft, and I went more like 16 cu ft, well beyond the point of diminishing returns, but not quite large enough to go LLT cabinet. Sometimes I feel like I should *feel* more output below 20Hz, but maybe I'm just expecting too much (due to my large room with connecting hallways and stairs that I can't close off).

I'd love to have tried an M-18 in LLT and directly compared it to my M-21 sealed.

Again, I've not taken any measurements...so my wanting more 15Hz could just be me not really understanding what 15Hz feels and sounds like. Maybe I have PLENTY and I'm sitting in a dead spot. So till I get measurements and make sure I have the best sub placement, I really can't say if I built the perfect sub for me, or if I should have gone with Steve's suggestion of an 18" LLT, or other suggestions of tapped horn, or dual 18 sealed or so on and so forth.

I'm not disappointed, I'm just wondering what difference I would get in an 18" LLT. And if I had the cash, I'd build one just to compare and sell what I thought didn't suit me as well. :wave:

Sounds reasonable. What I have learned is you ask a question and pretty much you will get a different answer from just about anyone. Each person has different tastes etc. Soon as I finish my room I can't wait to see what a sealed 21 in a 12cu ft box will do in my 2800cu ft room.
 

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Discussion Starter #89
It's likely to be the blend between the sub and mains, or the room, or the overall FR could have a resonance somewhere. It's possible that there is a bad enclosure resonance sometimes, but probably not the driver/cabinet itself. When you get around to investigating that it'll probably show up somewhere.:T
And there could be completely nothing wrong. As I said, I'm not used to subsonic frequencies, so I'm relearning what bass is. Steve C was right about that!

On a side note; I called a local music shop who specializes in live sound installs and asked if they have the FBQ-2496 in stock. He basically laughed and said all Behringer stuff was and why would I want to use that in my home theater. When I explained that a whole sub-culture of DIY sub builders have been using the B amps and EQs successfully for years, he LOL'd and said something along the lines of "they must not have very good taste...you won't find that here"

Ask 20 people, get 20 different asnwers. LOL
 

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Discussion Starter #91
Actually, the larger the subwoofer enclosure, the less driver ringing there will be, so while there isn't really any "speed" to talk about, there is delayed energy, and a larger sub will have less of it.

A FR at the seat will answer a lot of questions :bigsmile:
I am so confused by what you just said. Clarify for me please? I have a feeling there is a solid piece of wisdom that I'm missing there.


As for the second part...yeah, yeah...I'll be getting there. Just too many other things going on right now....and I STILL can't find where I hid the Mackie Mixing Board and Behringer mic! I'm sure I put them someplace safe. LOL
 

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:nerd:

When the driver is fed signal, the cone moves - the movement is progressively resisted by the buildup of pressure inside the enclosure below its resonance. The driver has to overcome its own suspension as well as the air spring of the enclosure. In an infinitely large enclosure, there is no air spring, no buildup of pressure inside the enclosure, just the dirver's suspension to overcome. This is why you gain more low frequency efficiency with a larger enclosure - less resistance to movement. With less forces acting upon the driver, it also makes it easier for the driver to start and stop when the signal tells it to (bass followed by silence for example). As the enclosure gets smaller, the pressure acting upon the driver from the inside - positive on the inward stroke and negative on the outward stroke - gets larger and larger. So now, when the signal stops, there will still be some built up energy that has to be dissipated, and the driver will "ring" or oscillate a little bit when it shouldn't.

Is the effect huge? No. Is it measurable? Yes. Member Ilkka put it to the test with clear results here. Is it audible? I guess it would depend on your driver, enclosure size, and sensitivity to harmonics. The uninitiated sometimes prefer the sound of driver ringing since it adds higher frequency harmonics, and higher frequencies are where you get "punch" or "kick". There is no punch or kick in subwoofer frequencies (to test this, unplug your speakers and just listen to music with the subwoofer on using an 80hz crossover.....no kick or punch to be found, just dummmm, doooommm, booommmm :R).

As you spend more time with this new sub, you will become more accustomed to clean bass. When you listen to a small, not so great subwoofer down the road, you'll pick up on those extra harmonics. You may or may not still like them - I'll guess not. Unfortunately though this has been mistaken by the audio community as "slow" bass, commonly associated with ported or larger subwoofers. To add to this, there is also the effect of low frequencies themselves - most are not used to them, and initially some may find their inclusion in audio to make things sound "slow" or lacking "punch" as well. When you hear these phrases, basically the person is saying they want artificial upper bass frequencies added to the sound by means of harmonic distortion and less legit low bass.

Not to get OT, but I'll think we may see some of this come to fruition with the popular bass horn being tested - higher frequency harmomonics that is.
 

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Discussion Starter #93
Awesome writeup Steve, thank you!

So, assuming I've done my part in building and damping a good box, and assuming the 21" has no inherent (physical) ring or issues, it sounds like I have plenty of positives on my side.

I'm not sure I agree 100% on your thoughts about "speed", but I totally see your point. I do wish I had my folded horn right now, so I could A-B the two boxes and see if those harmonics are apparent. I know in car audio I've seen people go ga-ga for boxes that I thought were resonant and speakers that seemed like one note wonders...so I guess some people will listen to anything.

I still have plenty of listening to do. I am only an egg....waiting for fullness.
 

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Discussion Starter #94
Alright, I found my Mic and Mixer, I've gone step by step through the REW setup, everything looks about right....except for this measurement. I've done it three times over, and I keep getting the same thing. I have my crossover on my Onkyo setup at THX spec of 80Hz, but I still get readings out to 200Hz. I've even gone as far as to disconnect all my speakers except the sub, and I still get the same reading. Tell me if this looks correct at all.

I'm using the Behringer Mic and calibration file, I've calibrated my sound card which is very flat from 12Hz out to 20+KHz, and everything was set to 75db according to my Rat Shack digital db meter. No smoothing, measured from 5Hz out to 200Hz with eight 1MB sweeps.





Suggestions? I can't think of where I might have a loop out of the receiver and back to the computer that would give me readings out to 200Hz. Though it's been a long day so maybe I missed something.
 

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Discussion Starter #95
I don't know if this helps any, but here is within 3 feet of the cone...which puts the mic right in front of my super-chunk bass trap...so it's somewhat in a corner.




I need to get some sleep...these long hours are starting to catch up to me...
 

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Something is not right with your measurements. Are you sure that the signal is not clipping somewhere? Use just 1 1M sweep for measurements. Make sure the results are repeatable. Also it looks like you are possibly double dipping on your calibration. Make sure you don't have C weighting checked under settings.

Are you sure that the microphone mixer output is going into the SC input and that is the only line going into it? :scratch: Check that you have the correct channel selected under the settings tab and also check all of your levels with pink noise and make sure everything is in the clear.
 

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Discussion Starter #97
Something is not right with your measurements. Are you sure that the signal is not clipping somewhere? Use just 1 1M sweep for measurements. Make sure the results are repeatable. Also it looks like you are possibly double dipping on your calibration. Make sure you don't have C weighting checked under settings.

Are you sure that the microphone mixer output is going into the SC input and that is the only line going into it? :scratch: Check that you have the correct channel selected under the settings tab and also check all of your levels with pink noise and make sure everything is in the clear.
I'm not sure I understand the double dipping part. I checked everything last night, but I'll check again tonight with a fresh mind and a few hours of sleep. Work and working on the house are beating the hell out of me, so it's probably a stupid mistake I've made.

For the close up measurement, I didn't readjust the levels, I was right at the verge of clipping. I just wanted to see if my measurements looked right up close.

I'll go over everything again tonight and see what happens. Thanks for helping me look at this Ricci
 

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Discussion Starter #98
Mini-update:

I spent an hour going over my connections, and I can't find where I'm getting feedback into REW that's causing the weird readings from my HTPC sound card.

So I tried to set everything up on a laptop I have that has a proper Audio IN (and optical out believe it or not!), but the calibration of the sound card scared me...it was a HUGE hump in the middle, flat up high, and a pit of despair below 80Hz. So I scrapped that plan.

I'll have to come up with a better measurement solution.
 

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This looks like a missing crossover to me. For such a large driver I suggest a 60 hz L-R crossover if you can manage it.

Distortion and breakup modes are what matter in drivers not speed. I'm sure this is a very low distortion sub. So that's not an issue.
 

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Discussion Starter #100
This looks like a missing crossover to me. For such a large driver I suggest a 60 hz L-R crossover if you can manage it.

Distortion and breakup modes are what matter in drivers not speed. I'm sure this is a very low distortion sub. So that's not an issue.
That is what it looks like, though I triple checked my settings, and my Onkyo 805 is crossed over at THX 80Hz standard.
 
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