| bri1270 |
Hi All,
I've been lurking for a while trying to take as much in as I can before actually posting a question. I am NOT a math guy at all, so some of this stuff is making my head spin.
I eventually would like to go with an IB, but I'm really not up for ripping into my wall right now, and there may be a problem with the location of my mains (they're only a foot from the wall where the IB would go).
I'm using Ascend Acoustic CMT340's for my mains and center. My room is 16x16 with an 8 foot ceiling which is actually a loft that extends about 2/3 over the listening area and then opens up to about 24'.
Right now I have an Earthquake Kompressor S12. It's a pretty good sub for $370 shipped, but I can't help but want more after reading all the DIY acclaim. What I am thinking of doing is using an Ascendant Atlas 15 with an O-Audio 500W BASH Amp. I'd like it to be musical, but I really want some good slam for movies. My EQ actually does a pretty good job at both for a sealed sub.
My thought was to get the Atlas 15, so that later, if I do decide on an IB I just need to get another one, and start ripping apart the family room (which I just finished remodeling last spring).
I can't seem to come up with a viable enclosure using WinISD. It's probably my steep learning curve.
I think I am entering the T/S parameters incorrectly or something.
Anyway - box size isn't all that much of a concern, but I'd like to keep it reasonable (2x2x3 or so). I have no preference as to sealed or ported, as long as you can tell me what the port diameter and length needs to be. If a ported design is suggested, then I would also like it to be a front firing design, as I get the best reponse in the front right corner, but a rear port definitely gets booming (which is why I went with the sealed EQ). If there's anything I can add to help someone help me then let me know.
Thanks,
Brian |
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| Tweeker |
| Atlas 15 in 2*2*2 cube, tuned to ~19hz with 2 4" diameter ports 19 inches long each perhaps? Dont give it more than ~300watts, cant bottom the voice coil but can cook it. |
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| DougL |
There is a sugested Sealed box for Q=.5 that looked sweet on the AA website. There is also a ported allignment.
I have no reason to beleive that the box volumes are not "spot on" unless you want something very unusual.
YMMV
Doug |
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| bri1270 |
Thanks Tweeker and Doug. I saw those recommendations, but I wasn't sure about the tuning portion of the vented box. I like output on both so I guess it comes down to personal preference.
At 20hz the ported sub tuned to 19hz is at 88db and the Selaed with a Q of 5 is 86db but the sealed sub seems to keep up within 2db or so all the way down to 10 at which point the sealed is actually 3db higher than the ported sub. I thought the opposite was supposed to be true?
If a sealed sub is producing good bass at the levels I want, isn't that the way to go because of "clarity" for lack of a better word?
Thanks Again for your help. |
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| bri1270 |
One last question on the Amp portion. I like the O-Audio because it has the built in parametric Eq. But I also like the Parts Express 250W amp because it's $128 and I won't overpower the driver. That being said, if I went with the O-Audio, and kept the gain in check, would that prevent a meltdown of the voice coil? Also, I've seen in other threads something about staying away from "bass boost," why is that?
Thanks,
Brian |
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| Tweeker |
Ported subs roll off quickly below tuning frequency as the driver becomes unloaded. Output just above tuning is higher though. Are you sure your read the 6.5 cu foot sealed box graph correctly? I see 82dB for it @ 20hz, vs 88dB ported. At 30hz 91dB ported, 87 sealed. Also the ported sub has half again the power handling for a smidgen over 1 more dB.
Yes if you keep the gain down youl be fine with the O-Audio. Id suggest looking at the 350 watt Rythmic Audio amp for $160.
Edit- bass boost can cause you to quickly run out of excursion, it may sound wretched doing it but you cant hurt an Atlas sub this way as the magnet wont allow the voice coil to bottom out. |
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| bri1270 |
| Sorry I was looking at the .57 Qts with a 7.8 cubic foot box. That Rythmic Amp looks like a pretty good deal. Would you reccomend adding the LT to the amp? Or just get the 350 Basic? |
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| Tweeker |
Ah, I see, I got confused, I was looking at the sealed enclosures that had .57q, rather than the ones where the driver had .57q.
Theres soo much you can fiddle with on Atlas subs. Actually you could even switch back and forth between the 7.8 cu foot .57 qts driver setup and the ported alignment I suggested just by blocking the ports and changing driver q, or aperiodic by putting a sock in it.
I dont think you need LT given how much box size you have to work with and the Atlas drivers flexibility. If you want a great parametric eq look at Behringer Feedback Destroyer Pro $100. |
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| simon5 |
The Atlas 15 seems to want a really big box to be flat down low.
Since you are limited by 2x2x3, I would go with 10 cu.ft internal tuned to 18.4 Hz using two standard Precision Port 4" diameter ports with full length center tubes. I would also use a Rythmik Audio 350W amplifier since you can't use more than that to stay into linear excursion.
Brace the box correctly and you will be satisfied, especially if you put that box in the corner. |
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| bri1270 |
| Thanks Simon. What do you mean by full length center tubes? |
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| simon5 |
| If you buy Precision Port 4" diameter flared ports at PartsExpress or somewhere else, they have a 12" long ABS tube that you can cut to the required length to go with the two flared ends. With my idea, you can keep them at the original length, that's all hehe! |
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| bri1270 |
| cool, that's easy enough, thanks Simon. |
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| bri1270 |
| Actually, after taking some additional measurements, I think I can go 1.75' x 2.5' x 3.5' which ends up being a little over 15^3. Would it make sense to go that big and tune to 16hz? If so, what would those port dims be? |
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| simon5 |
I would use that space if you don't mind. :D
Keep them at full-length.
Two ports at full-length will give a final tuning of 16.14 Hz for a 13 cu.ft internal volume box.
You can use a 250-300W plate amplifier, you don't need more. If you want to get the O-Audio for the parametric EQ, then set the rumble filter at the lowest frequency. |
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| bri1270 |
| Thanks Again Simon. How about the Rythmik 250 or 350 amp? Speaking of Rythmik, any thoughts on their DirectServo? Seems pretty good for the size and money. |
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| Tweeker |
What is the problem with the IB near the mains, ideal is centered between them is it not?
Might not be in the budget but 15 cubic feet is enough for 2 Atlas 15s or an Avalanche 18.
The Rythmic 350 amp is enough to power 2 Atlas 15s, its actually 380w.
It might be worth getting the $200 version. |
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| bri1270 |
I thought I read somewhere (the Cult forum) that the IB should be at least 3' from the mains if you put it in it's ideal location. For me, that location ends up being behind my right front channel and only about 1' of clearance, unless I put them in a transition box and mount it low.
To be honest, I've been looking into IB, and I'm trying to figure out how I can do it, which is why I want to buy a driver that can be used in that configuration. I guess if I went with two of the Atlas 15's in a manifold, that would work, but I really wanted to do an array...I might just have to sacrifice. At least I can build a manifold big enough to house more drivers in case I ever want more bass.
So I could put 2 Atlas 15's in that size enclosure and run them with one amp? That might be nice. How do you install them, firing away from one another? Or would I have to do an Isobaric configuration? |
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| simon5 |
You need less than 300W so a Rythmik Audio amp would be perfect IMHO. You can buy the basic 250W version or the special edition to get a 24 dB crossover. You could also get the 350W version if you want to, but don't use too much power.
DirectServo technology seems to be quite good, but you need to use their driver and it's not cheap. I have not heard it so I can't comment it more than that. |
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| Tweeker |
You can run two drivers off one amp, but I dont think that amp will handle a 2 ohm load and has only 245 at 8 ohms. Slipped my mind that you could no longer have a 4 ohm load.:whazzat: If you dont need the crossover look at a Nady XA900 $180. You can put one driver on each channel, and it can handle 2 ohm loads so would allow 2 on each channel if you needed.
You can use the box sub to find the best location for IB, non ideal IB still beats most other setups. |
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| bri1270 |
The Whole Rythmik Servo kit is $399 shipped, that's not too bad.
As for the IB, do you really think a non ideal IB is better than a regular sub, either vented or ported? |
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| Tweeker |
Yes, a non ideal IB would be better than a "regular" sub, unless your severely limited on mouth area. The competition would be dipoles, large horns, and TLs.:smash: :smash: :smash: :smash:
245watt @8ohms would be ok for 2 15s in IB config. That said, if going straight for IB the 4 AE IB15s for $400 is kinda hard to pass up. But those drivers only really work in IBs, dipoles, or open baffles. |
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| bri1270 |
how does a dipole work?
I took some more measurements, I think I can actually install two 15" drivers above my center channel in a line array configuration. I am going to dig into the wall from the back (that's where the mudroom is, and I just gutted it this past weekend) I think it's high enough (76" from the floor) to avoid any romex that's behind there. It'll also let me get a good look at the studs and what not. I still have to keep my options open though, in case it doesn't work out. I'm really not sure if I'm up for it, but what the hell, I can sell my Earthquake and probably make up enough to almost pay for the drivers anyway.
I definitely can't do more than two drivers in a line array, but I could put all four of the AE's in a transition box. Which would be better? |
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| Tweeker |
I think using 4 would be worth having to use a manifold. How much space do you have between each stud? The drivers not having to work as hard should easily make up for not being line array.
Dipoles
Pheonix Dipole Woofer |
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| bri1270 |
| it's hard to say how much room I have between the studs, my house was built in 1850. I won't really know until I get in there. |
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| bri1270 |
| I just read that the AE's should be mounted upside down, so either they're out or I have to go with an Array. |
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| Tweeker |
If the manifold has to be horizontal you could possible mount them this way: <and/\=woofer
................/\/\
wall ___<|.....|>___wall |
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| bri1270 |
sorry, i made a typo, the AE's Should NOT be mounted upside down.
I suppose I could put one on the back, one on the bottom and one left and right, but I didn't see any that way in the Cult Pics
Anyway, I don't think it will be too much of an issue as I am pretty confident that I can get a horizontal through the wall array anyway. Nothing says that they have to be grouped in a nice set, If I can place two sets of two next to one another and a couple of feet apart, that should work also if I'm not mistaken. Plus, I think it looks pretty damn sweet haveing four 15" drivers sticking out of the wall into the listening area.
Tweeker, do you think I can power four drivers with a plate amp if they are wired Serial/Paralell which should keep the ohm rating consistent, especially if I buy the 8ohm versions of the AE's? I really hate the idea of a BFD. Also noticed that Rythmik is working on a servo driven 15" for IB, that would be nice... |
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| Tweeker |
To drive 4 with a plate amp wired series/parallel youd want to use the 4 ohm drivers. 1000 watt plate amp would work fine. Youd need a pro amp to drive the 8 ohm ones, even adding the BFD it wouldnt cost any more, though possibly noisier.
BFD tuning guide, rather involved, but much finer granularity.
It might be better to mount the drivers 2*2 like so:
OO
OO
Makes them closer together so that you dont have sound from one speaker ariving at the listener a different time from another. |
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| Tweeker |
| The advantage of line array for subwoofer IB application is not so much that they are in a line, but that there is absolutely no restriction on the woofer outlets, which can act as a bandpass. |
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| bri1270 |
That's a configuration I was thinking about also...that might work out, but I could be closing in on my center speaker which is mounted on the wall. More measuring.
According to this http://www.bcae1.com/
seires/parallel keeps the ohms the same, so why not go with 8ohms, wouldn't they be "easier" to drive? |
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| Tweeker |
| Its easier on them amp, runs cooler etc, but the 1,000 watt plate amp from PE only gives 512watts at 8 ohms. |
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| bri1270 |
| Duh - I guess I should have looked at the specs...thanks |
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