Christmas Build - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #21 of 103 Old 12-24-12, 09:29 PM Thread Starter
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Quote:
zacjones wrote: View Post

Well it looks like you decided on the S4 version and to wire the four subs in series/parallel to a 4ohm bridged EP4000. That'll net you about 600w per driver. Risky with no SSF. Just be careful. All it takes is one big explosion on a movie you're unfamiliar with and CLANK pff pff... I'm all too familiar with this sound having reconed three 18" drivers in my HT over the last few years from overexcursion at < 15 hz.

Personally I would have opted for the S2 version and ran them two drivers in series to each channel of the amp. Easier load on the amplifier, better damping factor being unbridged, and more than enough power to take the drivers to overexcursion. This configuration would net about 325w per driver, and the Fi's reach Xmax in IB at just over 300w.

It sounds like your order's almost ready at Fi, so if you end up with the S4 version I would recommend wiring them in parallel pairs to a 4ohm stereo load on your amp. The EP4000 puts out about 820w/ch in 2ohm stereo, so you'd have 410w per driver which is plenty of power, and running the amp unbridged is preferable really unless you need every last drop of power.

BTW if you haven't gotten your EP4000 yet just cancel your amazon order and give Zzounds a call. They're an authorized dealer and will price match Amazon -5% with free shipping! I just bought two of them from Zzounds last month, and it came to less than $260 ea with no tax. I saved about $80 altogether vs Amazon because Amazon would've charged me sales tax in California.

Anyway good luck. Let's see some pictures!
Thanks for the advice, wish I had gotten it earlier. Already got the ep4000. No shipping and no tax, so I am ok with the deal.

I did get the s4 per advice of others.

I do have the MiniDSP and can implement any sort of parametric SSF curve or cut-off. What do you suggest? I REALLY want to enjoy explosions and not fear them. I would like to just enjoy the subs and not worry. Willing to live with a compromise to get that. I have lived in fear before and it is not enjoyable.

Also, I have decided on a line array. I am going to put the subs under the screen in a row. I will be able to nail it to the concrete floor and build a thick baffle which i will have decoupled from the wall. So I should have very little vibration in the front wall. The manifolds were just not working out as nice as a line array fits into the space.

Project will start when I get the drivers, unless someone can get me the exact measurements of the IB318 drivers.

-Brent


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post #22 of 103 Old 12-25-12, 02:09 AM
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Re: Christmas Build

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blitzer wrote: View Post
Thanks for the advice, wish I had gotten it earlier. Already got the ep4000. No shipping and no tax, so I am ok with the deal.

I did get the s4 per advice of others.

I do have the MiniDSP and can implement any sort of parametric SSF curve or cut-off. What do you suggest? I REALLY want to enjoy explosions and not fear them. I would like to just enjoy the subs and not worry. Willing to live with a compromise to get that. I have lived in fear before and it is not enjoyable.

Also, I have decided on a line array. I am going to put the subs under the screen in a row. I will be able to nail it to the concrete floor and build a thick baffle which i will have decoupled from the wall. So I should have very little vibration in the front wall. The manifolds were just not working out as nice as a line array fits into the space.

Project will start when I get the drivers, unless someone can get me the exact measurements of the IB318 drivers.
Well you need not worry. That's just how I would have done it. I think you're lucky I didn't talk to you first!

I just modeled them up both ways and I can definitely see the benefit of doing it the way you're setup to do it. You got good advice. You're going to get more output the way you're doing it. Especially if you already have a minDSP.

My recommendation was based mainly on appreciation for the Fi drivers by themselves. The are so perfectly suited to run without a SSF and still be protected that I would have tried to design the system to run without one, is all. That's not to say that you can't achieve almost exactly the same or even better results with more power and a SSF. The gain you'll see above 15hz with more power and a SSF at 10hz is probably going to be more significant than any gains you may have gotten below 15hz by running lower power and without a SSF. I'm accustomed to using subsonic filters up much higher than 10hz, where you're really losing some output. In this case, with a 6db butterworth HPF at 10hz, I really don't think you're going to notice the difference with it on or off. In fact your foundation may thank you.

I don't know if you've modeled them up in winISD yet, but here's an idea of various configurations with your four drivers, an EP4000, and a miniDSP. It's the least I can do after serving up some questionable advice.

RED is 500w per driver with the amp bridged and the drivers wired in series/parallel. This is really pushing the amp.
YELLOW is 410w per driver with the amp run in stereo and the drivers wired in series for a 2ohm load per side. Still pushing that amp pretty hard, but definitely getting a lot out of it. Probably the option I would choose with a SSF.
PINK (the crazy color) is 325w per driver which is the way I might have done it.



And the cone excursion without SSF



Now SPL only marginally impacted with a 6db/octave butterworth HPF at 10hz on RED and YELLOW



And cone excursion under control with the 6db/octave HPF at 10hz on RED and YELLOW.



So it looks like you've gotten some good advice and chosen well. With a 6db/oct HPF at 10hz you'll have plenty of output and won't have to worry about bottoming out your drivers. The miniDSP allows SSF control all the way down to 10hz, so you're OK there.

I think your choice to run the drivers in an array below the screen is a great choice. It's really nice to be able to see the drivers doing their thing when you're listening to music. You may want to ask them at Fi if they can do anything about the white logos on those dustcaps though! Nice maybe for the trunk of a car, not so great for HT.

From the Fi website on the IB318 page:

Sub OD: 18.500”
Cut ID: 16.750”
Mounting depth: 9.500”

What they don't tell you though is the screw hole spacing. Are you going to be using hurricane nuts? http://www.parts-express.com/pe/show...umber=081-1084

Last edited by zacjones; 12-25-12 at 02:27 AM.
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post #23 of 103 Old 12-30-12, 01:42 PM Thread Starter
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Re: Christmas Build

Fantanstic Advice. I had made one lame attempt to setup winISD. You inspired me to try again and after Googling a bit and got the same graphs you did. Funny how winISD does not agree with the manufacture's specs and insists on using it's own theoretical ones. I was insisting on using the specs from FiCarAudio and winISD would not work for me.

I liked your earlier points about sound quality and damping. I will experiment with different setups to see if I can even tell the difference. I am sure this will be extreme overkill, so there is plenty room to play and adjust.
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post #24 of 103 Old 12-30-12, 05:56 PM
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The reason WinISD has problems (in many cases) is due to round-off that leads to numerical inconsistency with some of the formulas. That's why it is best to enter the most important ones and let the program calculate rhe rest. There is a sticky thread here somewhere that details the correct order for entering parameters
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post #25 of 103 Old 12-30-12, 09:38 PM Thread Starter
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Re: Christmas Build

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vann_d wrote: View Post
The reason WinISD has problems (in many cases) is due to round-off that leads to numerical inconsistency with some of the formulas. That's why it is best to enter the most important ones and let the program calculate rhe rest. There is a sticky thread here somewhere that details the correct order for entering parameters
Makes sense, but it could not even deal with the TS settings from the manufacturing.
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post #26 of 103 Old 12-30-12, 09:39 PM Thread Starter
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Re: Christmas Build

I am trying to decide on the orientation of the subs. Which to you prefer?



I expect the reaction to the cones will be disbelief and astonishment and the reaction to the baskets to be confusion as to what it is. SO many people have never seen the back side of a speaker. So maybe I need to decide if I want people to be amazed or confused(until I show them the cones in the other room). The baskets have a decidedly sci-fi look, which may be cool.

Having the baskets in the room also reduces the chance of damage as I do have an 8 year old boy...

Thoughts - anyone have first hand experience?

I had envisioned something like this guy did:

Last edited by blitzer; 01-20-13 at 06:34 PM.
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post #27 of 103 Old 12-30-12, 11:18 PM
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Re: Christmas Build

I like both looks, and I like the extruded baffle. The Fi drivers have a nice backside, every bit as attractive as the front to me if not more. A couple issues that may be of some concern with the reverse mount: The wires are exposed so if you have small kids or cats I would think that could be a problem. Careful installation with heat shrink would reduce the likelihood but you'd still have the tinsel leads with current. Another issue is you'd be more subjected to mechanical noises from the motors of the subs having them rear mounted. I don't know how noisy these Fi IB subs are. My IXL's have really quiet motors. At seating distance for you it's probably not a significant issue though. Benefits from the reverse mount are less likelihood of damage to the cones and dustcaps from stray feet, bouncing balls etc. Stuff will probably get stuck to the magnets once in a while, but I don't see a problem there. I think a push-pull setup would look pretty sweet with the middle pair oriented one direction and the outside pair oriented the other.

In your IB array there might be some benefit to doing a push pull system where two of the subs are front mounted and the other two are reverse mounted. You would likely get some of the benefits of cancelling mechanical forces on the baffle wall as long as the drivers are arranged properly on a slightly oversized, very stiff baffle. There are other acoustic benefits of push-pull driver setups as well, that a push pull array might qualify for.

There's a lot of info out there on this subject and it's way over my head, but here's a thread with an interesting discussion regarding an install similar to yours --

http://www.hometheatershack.com/foru...#axzz2GbJsGLys

I think you could even make the recessed cutouts on the fronts of the baffle as if you were going to flush front mount all the drivers, then play around with different combinations until you find a solution you're happy with. You could easily fabricate some very attractively profiled trim rings with a router to fit in the recesses on the front if you decided to rear mount any of them. You could also put trim rings on the recessed subs that are front mounted as well for a nice look to cover up the woofer frame and all the mounting screw holes. You could use small neo magnets glued into recesses on the back of the trim rings to attach them to the frame of the woofers. If you got tired of a certain look and wanted a change it would be easy enough to reorient them for a new look. I would definitely consider running a router along the outside lines of your extended baffle to give it a little more style as well. It looks like you're going to be stacking layers of MDF or plywood to get your baffle super thick. You could also route a groove into the sides of the baffle every few layers or so as you build it up for additional style points. 96" x 24" seems like an efficient use of wood and a good size for your baffle.

Edit just reread your post and see you have an eight year old boy. I think reverse mount and custom speaker grilles made out of hardwood would be sweet.

Last edited by zacjones; 12-30-12 at 11:57 PM.
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post #28 of 103 Old 12-31-12, 12:26 AM
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Re: Christmas Build

I prefer the front mount. I wouldn't want to see the wires unless you did something really fancy like copper tubing (saw pictures of a sub someone did once like this and it looked really cool, of course it could be hazardous if exposed). I also think you could save yourself a lot of effort that way and use the time to make a cool looking grill, which you'll probably need anyway.

I think it would be difficult to see the stroke of the cones in a reverse mount configuration, which is always cool to see at ultra low frequency.
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post #29 of 103 Old 01-01-13, 04:40 PM Thread Starter
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Re: Christmas Build

Ok, I will need to make a decision when I get the drivers in a few days. I need to play around with them.
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post #30 of 103 Old 01-01-13, 07:05 PM Thread Starter
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Re: Christmas Build

Ok, getting more serious about the build. I have a pretty humble space for the home theater. The only thing a really have going for me is there is no WAF factor in my basement and can do what I wish as evidenced by the large speakers I currently have. But, I will not truly fire up the IB with her in the house. Similarly, I have never shown her how fast my car goes as I go slow with her in it.



I finished the basement myself and have no issues with modifying the walls. The wall that is to contain the IB is a 6 inch staggered stud wall - so a lot of 2x4 cutting.

The small space I have for the home theater has a number of problems. If I had any sense I would just stay with my current sub, but I have gone ahead even with the issues with the space.

Here is a model of the basement:


There are at least 4 issues with my space - could use opinions and advice on how to best handle:

1. I have a drop ceiling. It does not make much noise at all with my current sub. But, I may have to do some serious work to control any noises with the IB.

2. The room for the back of the IB opens up above the drop ceiling. I think that that will cause tiles to jump around, reduce the output of the sub, and cause sound quality issues. I am currently working on sealing it up, but there is a lot of duct work that crosses the 2 rooms. I have no idea what is going to happen with that. At the minimum I will need to dampen the ducts.

Here is the opening to the space above the drop ceiling of the home theater.


My start at boarding up the opening.


I am planning on putting a bunch of gap sealing foam and also caulk to make sure it is as sealed as possible.


3. If you look at the following picture you will see that there is a concrete wall at the end of the drywall where the back of the last IB318 will go. Unfortunately, this means 2 things: I will have to show the drivers to the home theater room(I was trying to decide which way to orient the woofers in earlier posts, just realized the decision has been made for me. Also, I will need to hammer out a notch for the basket to fit so that the subs are aligned under the screen. I have never done this with this type of concrete and don't know what to expect or how to do it with the confines I have.



4. The door! I have a door that will be right next to the sub. It is a very heavy solid core door and I will seal it up. But I do not know what to expect. I can add a bunch of MDF to the back of the door if needed. There is already a deadbolt near the top of the door that locks in in place. Hoping the this is not a deal breaker.



5. One more issue I have is the balanced MiniDSP I ordered has a serious mismatch in gain between the pre-amp and the MiniDSP. I am going to need get something to insert to pump up the gain.

Things I *think* I have going for me:

1. I can brace the sub against the concrete and decouple from the wall in order to reduce to a minimum the mechanical forces on the wall.

2. If the door or ceiling issue are too big to overcome, I can easily turn this into a super giant ported SLLT sub as Rodny did in the "IB makeover" thread - check out page 11. This could raise the output of the sub considerably.

Last edited by blitzer; 01-18-13 at 09:03 PM.
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2ohm , 4ohm , behringer ep4000 , build , christmas , ib , ib subwoofer , ib318 , magnepan , manifold , minidsp , subwoofer

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