Very low tuned (16 Hz?) vented enclosure for JBL W15GTI

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I've always liked ultra low bass. No, actually I love it! I have one woofer already waiting to be "properly" used, but it doesn't have an adequate enclosure to satisfy my needs. I've made some modelling using WINISD and I'm currently leaning on box with volume of 334,15 liters and tuning frequency of 16,01 Hz. Is two 100 mm round ports enough to guarantee good airflow? I was thinking of using three ports, but it takes way too much space, so I'll hope that two is enough. I'm currently using amp with ~ 500 WRms (Hypex DX 4.0) but in the future I'll get a more powerful amp. This woofer will be used for movies and music and my current room size is about 5m*3,5m*2.6m.

I attached two pictures of group delay and two pictures of SPL levels played with 1000 Watts. First option is just to use woofer and second one is with butterworth type second degree LPT cutting at 35 Hz with 150 grams of added mass to the cone. With second option frequency response is a bit smoother, but group delay grows quite a lot (mostly because of LPF).
In any case I need to use LPF, so will this become a problem (group delay)? Should I add some weight to the cone? Also my room has pretty terrible room mode near 30 Hz (need to get a house with big living room :D ).

Here are the parameters for JBL W15GTI subwoofer in case you need it:
Qts: 0,480 Vas: 132,01l Fs: 25,2Hz Xmax: 20,3mm Qms: 7,200 Qes: 0,514 SPL: 88,17dB Sd: 780 cm^2
 

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Check in WinIsd for Port air speed, introducing the 800W or 500W you are planning (RMS). It looks that your ports might be enough. Calculate for max area and the the length of port. You have to calculate their total volume and aloud the ports volume as adding to NET (+driver) for the total internal volume of the speaker.
Interesting applications with smaller speakers volumes below
W15GTI MkII & W12GTI MkII

Consider a more round and linear application like this: 267L@18Hz
Better for the space/rooms and behavior like the group delay and "room gain" that you suggest. Have fun.
 
Is two 100 mm round ports enough to guarantee good airflow? I was thinking of using three ports, but it takes way too much space, so I'll hope that two is enough. I'm currently using amp with ~ 500 WRms (Hypex DX 4.0) but in the future I'll get a more powerful amp. This woofer will be used for movies and music and my current room size is about 5m*3,5m*2.6m.

Sim problem I had; large port ducting to avoid air noises sucks out too much internal volume.....I raised the whole speaker 2" off the floor using wheels and used that gap between the flooring and the cabinet as part of the bottom loaded duct, although it will have to be experimented to get the correct 'humps'. Don't use this method on wooden flooring ! My 15 inchers have this.

rich
 
Check in WinIsd for Port air speed, introducing the 800W or 500W you are planning (RMS). It looks that your ports might be enough. Calculate for max area and the the length of port. You have to calculate their total volume and aloud the ports volume as adding to NET (+driver) for the total internal volume of the speaker.
Interesting applications with smaller speakers volumes below
W15GTI MkII & W12GTI MkII

Consider a more round and linear application like this: 267L@18Hz
Better for the space/rooms and behavior like the group delay and "room gain" that you suggest. Have fun.

Hmm 267L@18Hz looks very nice. Element can take a bit more "punishment" when considering the limited Xmax (up to ~16 Hz). Although group delay is a bit higher than with 334L box, the amount of eq:ing needed to soft the curve, will make it worse.
Thanks for the tips, this looks to be the road where I'm heading now :eek:
 
Sim problem I had; large port ducting to avoid air noises sucks out too much internal volume.....I raised the whole speaker 2" off the floor using wheels and used that gap between the flooring and the cabinet as part of the bottom loaded duct, although it will have to be experimented to get the correct 'humps'. Don't use this method on wooden flooring ! My 15 inchers have this.

rich

:D This is a great idea, but I don't have the mindset currently to solve these kind of equations :) If I recall correctly you don't need to have pipes in that 2" space, but it will still effect the tuning frequency, is that correct?

What kind of pipe would you guys suggest that I use? Sewer pipe is very common where I live. Does it have any defects that might lower the quality of bass?

Edit: Black color would be good, cos my current design color is glossy black
 
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I quess I made too quick assumptions about the equalization, but my idea wast to boost ~20 Hz area a bit with the 16 Hz box. But that difference is curves isn't really that much after all. I guess needs for equalizing will be known after I have sub in my room. Friend of mine told me that he has microphone for measuring speakers so I think that will help somewhat. I've added graphs of group delay with 16 Hz box and a 18 Hz box. Also I inserted SPL levels with signal of 1000 Watts. Red graph indicates 18 Hz box in both graphs.

According to WinISD 16 Hz box will have a better group delay down to ~ 16 Hz. I don't know how big deal increased delay is with frequencies below 20 Hz? My main speakers are Jbl Ti6K so I think I can set LPF pretty low (or maybe not?).
 

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:D This is a great idea, but I don't have the mindset currently to solve these kind of equations :) If I recall correctly you don't need to have pipes in that 2" space, but it will still effect the tuning frequency, is that correct?

Yes; the real drawback of the bottom loaded floor tuned vent on big cabinets is the difficulty of adjusting the tuning frequency, but I did this with my 15 inchers, an adjustment sleeve from the inside (removable top cover) as the standard 6" orange drainpipe comes up though the bottom of the cabinet. Although the idea is fairly sound; as you mention the physics is awkward, and more so as if the cabinet is placed in a near corner. This I found effects the loading, and presents the resonance as somewhat broad loaded, as the two peaks then don't reckon with that on paper. Redoing the simple test of measuring the two impedance peaks either side of the driver resonant frequency will show to vary when the cabinet is moved from a corner. The trick is to block off the rear and part sides section of the floor loading, redimension and retune, which gave more consistent results. Low frequency waves tend to cling to outer surfaces, the 3 plane corner placement is already a good 6dB boost at the low end just to make things more complex. My cabinets forced with my 500W tube amp at 400W at 25Hz, displayed very little cone movement but shattered the striplights in my work area; despite being an acoustically hard room. It rattled every electrical connection in the wall sockets loose. Be careful in not creating more work when it need not be !

richy
 
Don't be absurd. You don't need a video just for the kick of it...you should know darned well the vibration is enormous, and to ones insides.

OK so that might have been a little abrupt on my part and my response is very unusual for me so let me try it again:

What method of audio force "shattered" your workshop strip lights?

Our workshop has six double 18" sub boxes loaded with JBL 2242's driven by three AETechron 7780's with a combined output of nearly 12,000 Watts. With 68 strip lights hanging from the ceiling we have never had one fall out. I am just wondering how you got that done with 400 Watts, thats all.

Barry.
 
OK so that might have been a little abrupt on my part and my response is very unusual for me so let me try it again:

What method of audio force "shattered" your workshop strip lights?

Our workshop has six double 18" sub boxes loaded with JBL 2242's driven by three AETechron 7780's with a combined output of nearly 12,000 Watts. With 68 strip lights hanging from the ceiling we have never had one fall out. I am just wondering how you got that done with 400 Watts, thats all.

Barry.

Pics or doesn't exist :D
Seriously post pics, that must be amazing
 
The wife and I were cleaning house Friday pm. I had Pandora playing thru my Pioneer AVR. I have an old Yamaha AVR connected to a Kicker 08S15L7 in a T-TQWT (negative flare tapped horn). Our master bedroom is above my mancave. She said she walked into the bedroom and felt the floor sunk in on a dubstep type track that was playing. The Yamaha AVR might put out 100w per channel in stereo mode. There are cracks along the ceiling in the mancave and around the door frames in the mancave (walk in closet) and master bedroom.
 

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This pic was taking Super Bowl day 2016 by the wife. Note the sub is not firing into the corner like the 1st pic, flatter response. The silver receiver is the Yamaha AVR powering the sub. The Sony AVR in the 1st pic was going bad when I built the sub. The wife JUST got on me Sunday night for not finishing the sub. I told her it was just a test box made out of scrap wood. The next box is going to be the size of the Cowboy blanket or bigger.
 

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Pics or doesn't exist :D
Seriously post pics, that must be amazing

I Finally got a minute to dig a little.

The first pic shows the backside of the old racks with six Techron 7560-7570's running the subs. The pics of the big amps were taken before they were tested and employed. They were set up for constant current, glad I caught that!

I absolutely hate the sideways pictures, they are correctly oriented in my computer so I don't get why they uploaded and or displayed like this but I don't have time to try to fix them, sorry.

I need to get up there and take some better pics!

All the best,
Barry.
 

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I don't know why I think they are so cool but I do.

The three phase power requirement is the only down side, oh and the weight, at over 130 pounds each, once they are in a rack, that's where they stay.

They are the boss though, a woofer does what it is told when connected to these. :)

Barry.
 
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