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post #1 of 19 Old 07-11-2013, 11:45 PM - Thread Starter
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Now that I'm getting around to compiling the data and measurements from my latest build I thought I'd post these. After 16 years in the home we built and 6 different theater remodels we have moved. Currently we're renting a home which is the same exact floor plan as the one were interested in having built. Same builder as our last home we sold. While its a larger home, the two rooms that are designated for the HT rooms are both smaller. In the old home the HT was 18x19x8. The new house options are the media room off the entry way which is 16x12x9 or the last bedroom of the secondary bedrooms (split wing) which is 13x14.8x9. In the rental I'm using the bedroom because of complete light control. Problem is the Duo's didn't fit very well. I tried every conceivable placement and the response was not nearly as smooth as the room at the other house. I even tried nearfield behind the seating with both subs, then one only. The only thing to do was build new cabs. These would be placed next to the mains, so I wanted them to match as closely in size and finish. These started out as test boxes as I've never had much success with any subs response when place on the screen/front wall, especially with regards to tactile output.

On to the subs. These were built to match my Aerial 7b's in height and finish. In the end, i forgo'd the black ash veneered finish for a simple black satin paint finish. The box was built out of .75" MDF sheets, with 1.5" baffles and mitre-locked joints. Minimal bracing. A I mentioned these started out simply as test/temp cabs. Knowing what I know now, I would have used more extensive bracing and still may add some blocking. Each driver is in its own sealed 3.4 cuft section. About 3lbs of polyfill was added per driver. The overall dimensions are 42"x17"x24". I added a 1.5" MDF base to the bottom of each sub, To match the mains stands and to mimic the Aerial SW12 stand, both of which are made by Sound Anchors. I used the same Dayton 15HF drivers from the Duos. Do to a garage full of moving boxes, it was constructed outside under the patio and assembled inside at night. Damp weather didn't help. Cabs were glued and clamped only.

This cab/driver/placement/room combo is phenomenal. LF is deep, clean and smooth. Complete delineation of the source. Never have I been able to change crossover freqs up and down with so little change in sound. I've thought the subs were turned off when they weren't and vice versa. I do my serious (24/192) 2-channel listening with the subs on. As always I laid out the room symmetrically.

Here's a couple bad pics taken with my phone. I've since found my camera so the completed pics are taken with that. I'll have to work on the lighting during the pic session as the room has a lot of black panels. I'll post the testing and graphing shortly comparing it to the previous room and system. There's some rather interesting anomalies here.



AppleMark
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post #2 of 19 Old 07-11-2013, 11:47 PM - Thread Starter
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post #3 of 19 Old 07-11-2013, 11:53 PM
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Nice! Curious why you think you need more bracing? that looks pretty extensive.
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post #4 of 19 Old 07-12-2013, 12:18 AM - Thread Starter
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Quote:
Originally Posted by Jay1 View Post

Nice! Curious why you think you need more bracing? that looks pretty extensive.

Normally I brace front to back as well. It probably wouldn't make any difference though. Never going to be non-resonant like a dual opposed cab.
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post #5 of 19 Old 07-12-2013, 12:32 AM - Thread Starter
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post #6 of 19 Old 07-12-2013, 01:39 AM - Thread Starter
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Here's the OmniMic Docs.

All Response Graphs taken at -10db ref. Only subs running. All other amps shut off. MLP is exactly half way between subs. Distance of subs to Mic is 10.2ft. The middle of the subs dust caps measure 36" from front wall and 20" from side wall.

This is subs with no eq at 2db resolution.


This is subs with eq (Audyssey XT only) at 1db resolution.


Alternate (acoustical) tune at 1db resolution.


Heres the composite of all the above.
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post #7 of 19 Old 07-12-2013, 01:56 AM - Thread Starter
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I turned the subs to load the corners. This gave a good gain starting at 20hz and rising from there. This leads me to believe this is the wave to pressure point here. Room gain kicks at the same frequency as my other room.
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And corresponding graphs. Black is drivers facing corners.


More coming tomorrow.
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post #8 of 19 Old 07-12-2013, 02:50 PM - Thread Starter
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Today I did some more in-depth testing. Mainly running sines from 1-20hz and measuring max SPL and the voltage the amp puts out different volumes and frequencies. What a difference a room makes when it comes to ULF. Never dreamed of having this response down low. I was seriously thinking of using a HPF at 10-12hz if nothing more than to protect the gear. Don't think I need that now. The drivers match up well with 300watts, although at 5-10hz the driver are the limiting factor. This system is very flat to 14hz. The sweeps were 10 sec sweeps.

Heres a sine wave at 7Hhz. I measured voltage at 30.4. I'm not sure why the difference in SPL between FFT and RTA/DB meter or why RTA doesn't show down below 15hz in OmniMic.

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post #9 of 19 Old 07-12-2013, 07:58 PM
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Perhaps I missed it, but what are you using to power these with?
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post #10 of 19 Old 07-12-2013, 08:30 PM - Thread Starter
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Couple of old, old Parasound HCA1500's. I bought an EP4000 a year ago and turn it on then boxed it after a few minutes. Can't tolerate the fan noise even modded. These work good, have remote 12v turn on, are dead quiet, pretty much flat to 5hz and are durable.
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post #11 of 19 Old 07-12-2013, 08:44 PM
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Look. Cool. Coolrda biggrin.gif. I like my parasound hca 2205at. Too
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post #12 of 19 Old 07-14-2013, 05:22 AM
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So how do you like these duel Dayton HF15's compared to the Aerial SW12?
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post #13 of 19 Old 07-14-2013, 06:52 PM - Thread Starter
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The Aerial is a fantastic sub. Very precise sub. Their cabs are certainly better than mine. Both subs sound similar in quality and output at 20 and above. Below 20 is where the difference shows of course.
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post #14 of 19 Old 07-15-2013, 11:07 AM - Thread Starter
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I haven't read up on sub coupling for many years. It used to be you spike the sub when on carpet over concrete. Then I heard decoupling with dense foam was better. The cabs are rocking front to back badly. Any ideas on the best way to deal with this? My front three are spiked.
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post #15 of 19 Old 07-15-2013, 11:24 AM
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You're on carpet, you need to spike down into the underlayment.
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post #16 of 19 Old 07-17-2013, 12:32 AM - Thread Starter
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Thanks. I found some old unused spikes. Got one leveled and locked and compared it to the other sub. Huge difference. Unfortunately it was the spiked sub that vibrated uncontrollably compared to the unspike sub. At least 2x the vibration of the unspiked. I removed the spikes. The cabs weren't rocking back and forth like I thought it was. Its the top vibrating. I'm guess I'm just used to the opposed designs vibes being completely nullified. No difference in sound between spiked and not.
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post #17 of 19 Old 07-17-2013, 01:03 AM - Thread Starter
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The anomaly I was referring to was the difference in readings I got below 10hz. One day I would have this.



The next day this.



Back and forth. Tried everything to recreate it but couldn't. Then just by chance my son opened the door to his room while I was taking readings with OmniMic and I saw the change. Opening his bedroom door creates a peak centered at 7hz and a dip at 5hz. His bedroom is the door on the right. Theater door on the left. Bathroom door in the middle doesn't really have much effect.




Top graph, door open. Bottom graph, door closed. Crazy. Or at least I am walking through the house opening and closing doors and rearranging the pantry to see if I can EQ that 10hz valley. If I didn't see this with my own eyes I would never believe it. It makes sense though, in that a house is a big box.
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post #18 of 19 Old 07-17-2013, 03:22 AM
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Quote:
Originally Posted by coolrda View Post

Or at least I am walking through the house opening and closing doors and rearranging the pantry to see if I can EQ that 10hz valley.

LOL!! biggrin.gif

That is awesome, I got some really messed up readings if I had the windows open. There is an airport near my house - no good for readings lol.
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post #19 of 19 Old 07-18-2013, 01:04 PM - Thread Starter
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I spent some time taking voltage readings using OmniMic and track 18 I believe which is the 50hz continuous tone. Using my trusty old Fluke Mod#16 voltmeter i adjusted the volume until I reach 2.0v at the speaker terminal. 2v into 4ohms should give me my system/room sensitivity. Then I measured all 4 terminals and all read between 1.98v- 2.01v. All channels are performing to spec. The subs are about 10-11ft apart and are equidistance to the MLP. The subs are 10.2ft from the MLP. So at 4x1w@50hz I get 100db. In my case that corresponded to a master volume setting of -3db



Next. I was interested in a comparison of room gain, not so much as to how much I get with my current sub/room combo but in relation to my former room. As always there's some variables. In this case its only a small difference, that of the box design (duo opposed vs single plane). The duo box was 8 cubes and the new box is 6.8. First room was 2700+ and my current room is 1700+. Everything else is exactly the same. From the drivers and amps to the frontend (Onkyo 885/Oppo 93/Omnimic CD track 2), same interconnects and speaker cable, to the multiples of Audyssey tunes I took of the system. Both subs are still sealed. I went back and looked back at all the data from the previous room and the new room. I unfortunately never took distortion measurement which now would have been very useful. My process for finding MaxSPL of the given sub system is to play track 2 and raise volume until audio clipping or compression of the waveform is showing. Having spent hours and overlaying hundreds of different graphs I've come up with this. This is the difference between the same sub system in a 1700cuft vs 2700cuft room.



Disregard the black wave. The red wave=1700 room and blue=2700 room. Interesting how the 1700 dominates at 15hz and 5hz but their equal at 10hz. Now to really analyze the difference I concentrated on the 20-50hz area. This is what I got.



Now I know the readings can be influenced by other sources. Even with the AC, washer and dryer on, noise in the room has never exceeded 60dbs. Despite that, I always make sure everything is off and take readings at a minimum of 95dbs, just to be sure. Comparing this graph I get a 5-9 db gain from the 1700 room compared to the 2700 room. So just doing a straight average I'm going to say a person can expect somewhere around a 6db difference between a 1700 vs 2700 cuft room. In other words you need to double the drivers or quadruple the power. I have 4x15 with 4x300w in the 1700 room. I would need 8x15 and 8x300w in the 2700 to match. Or 4x15(Ultras or XXX's needed) and 4x1200w.

Crunching numbers I came up with a 1700 cuft room is .63 of a 2700 cuft room. Or a 2700 cuft room is 1.59x a 1700 cuft room. Using this formula a 1700cuft needs 4 drivers. A 2700=8. A 4300=16. How about a 6800 cuft room. 32 drivers. Are you freakin kidding me. Suddenly those Maniacal Bass Mongers here don't seem so crazy. I don't have any proof to back up these numbers on the larger rooms or if it would stay linear like that as room size grows. But it sure opened my eyes as to how fast things can get out of control with rising room volume. Total cost of my modest system with 2 old amps and complete build is about $1700. You triple the room volume and you could very easily need to spend 10x that to match the performance. i just figured this was the new cold war. I had no idea of the necessity of the huge systems built here. WOW.
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