Lilmike's Cinema F-20 - Page 3 - AVS Forum
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post #61 of 1740 Old 04-24-2011, 12:37 PM
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Thanks for the prompt response/explanation lilmike.

Sounds like a great design portfolio is about to be unleashed on the community.

How would the TC LMS-R 15" driver work in the F-20/F-24? Would gain a little more xmax, bl and power handling.

Thanks Again.
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post #62 of 1740 Old 04-24-2011, 04:13 PM - Thread Starter
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Quote:
Originally Posted by 04FLHRCI View Post

Thanks for the prompt response/explanation lilmike.

Sounds like a great design portfolio is about to be unleashed on the community.

How would the TC LMS-R 15" driver work in the F-20/F-24? Would gain a little more xmax, bl and power handling.

Thanks Again.

The LMS-R has a little too much motor, not a good fit if you're after a flat response.

I am nearly done with the F-24. While the result looks like a simple stretch of the F-20 fold, it is not. It was essentially a refold to get the details right.

It turns out that the MFW is power-limited above the horn tuning frequency in either cabinet. Only reason to go to a "bigger" driver is if you need more SPL due to power handling.
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post #63 of 1740 Old 04-24-2011, 05:15 PM
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Quote:
Originally Posted by lilmike View Post

The LMS-R has a little too much motor, not a good fit if you're after a flat response.

I am nearly done with the F-24. While the result looks like a simple stretch of the F-20 fold, it is not. It was essentially a refold to get the details right.

It turns out that the MFW is power-limited above the horn tuning frequency in either cabinet. Only reason to go to a "bigger" driver is if you need more SPL due to power handling.


What differences should be expected from the F-24 utilizing the MFW driver vs. F-20?

I assume it will be 4 cubic feet larger? I guess from wrapping the horn length more?
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post #64 of 1740 Old 04-24-2011, 05:33 PM - Thread Starter
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Originally Posted by turdlepoker View Post

What differences should be expected from the F-24 utilizing the MFW driver vs. F-20?

I assume it will be 4 cubic feet larger? I guess from wrapping the horn length more?

No extra wraps - just stretched it a foot taller, which messed everything up.....but I said I would, so I did. It just took me a little more work to get it right than I thought it would.

Here is a comparison. You give up a few dB and get a few Hz of extension.



I'll take the dBs personally. When comparing the two, I doubt anyone would notice the addition of 3 Hz of extension unless they were playing sine waves or posting their response plots on the interwebz, while a few dB of headroom is a big deal. Neither one will do the super low stuff all that well, the driver simply runs out of gas. It is only a single 15" driver.
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post #65 of 1740 Old 04-24-2011, 06:16 PM
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Quote:
Originally Posted by lilmike View Post

I'll take the dBs personally. When comparing the two, I doubt anyone would notice the addition of 3 Hz of extension unless they were playing sine waves or posting their response plots on the interwebz, while a few dB of headroom is a big deal. Neither one will do the super low stuff all that well, the driver simply runs out of gas. It is only a single 15" driver.

Sounds like something to consider. I am pretty much locked into the MFW since it is sitting downstairs in the floor waiting for a home. If there is no notable improvement from the added volume and a drop in spl I think perhaps I will get to work cutting an F20 this week and see where it all shakes out.

What the hay... I can always buy more wood and do it again .
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post #66 of 1740 Old 04-25-2011, 11:17 AM
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I have a friend coming from HTIB and wants some bass. With the shortage of good IB drivers I was wondering if you could put 2 of these shooting down from the attic. He has 24" OC spacing so they would fit between the joists no problem.

This does put the driver in the horizontal position tho. Would this create any problems? It might help with bass going thru the entire house as an IB does, since it doesn't open up to the attic.

Thanks
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post #67 of 1740 Old 04-25-2011, 12:09 PM - Thread Starter
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Compared to HTIB, this might be a little bit more than "some" bass....

It should work, but personally, I'd avoid that driver orientation. Cone sag will become an issue. Fortunately, this is not that hard to do.

Seal the end and cut the mouth through the side. Set the cabinet on the rafters, and extend the mouth as needed to get into the room. This way the horn can rest across several rafters and there is no weight on the mouth section. The longer horn might lower the tune by 0.42 Hz too.

Shoot me a PM if you want details.

Of course, getting these into the attic might be an interesting process.....they are not small.
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post #68 of 1740 Old 04-25-2011, 12:18 PM
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Thanks Mike. That sounds like the best plan. Would the new opening be the same dimensions as the original?

He is coming to my house Friday for a demo (I have multiple subwoofers). So I am sending him into the deep end. He also may be interested in my speakers (JTR T8's). If he buys mine I want Danley's.

Moto
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post #69 of 1740 Old 04-25-2011, 01:29 PM
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what is the final weight of the f-20?

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post #70 of 1740 Old 04-25-2011, 01:40 PM
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Quote:
Originally Posted by beastaudio
what is the final weight of the f-20?
I haven't built one yet but I would guess in the range of 150-175lbs with driver.
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post #71 of 1740 Old 04-25-2011, 02:31 PM
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good deal, how is the actual sub mounted inside there? looks a little tight... more I think about it, I would be able to fit one of these laid flat in front of my screen so I am now considering it strongly. will more than likely be better than a dual opposed MFW setup. how will the enclosure do with music though? rock,rap style stuff.

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post #72 of 1740 Old 04-25-2011, 03:14 PM - Thread Starter
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good deal, how is the actual sub mounted inside there? looks a little tight... more I think about it, I would be able to fit one of these laid flat in front of my screen so I am now considering it strongly. will more than likely be better than a dual opposed MFW setup. how will the enclosure do with music though? rock,rap style stuff.

Mine weighs 148 pounds. I built it with the cheap imported "birch" 13-ply from Home Depot that I've been looking to get rid of for a while...what better place to put it than into a test mule that might not work out.... Arauco might be a bit lighter, true Baltic birch might be a bit heavier.

The sound? Simply put, it is a horn, and horns sound clean because distortion is lowered. They don't seem as loud as a result, but I can assure you, they are plenty loud. I've not listened to music with mains through it yet (not enough daylight....and no help to move it....) but it measures and sounds better than what I am listening to now.... Well, that and I know if I did get it inside, I'd wind up dragging my other sub out instead....and I have not painted this cabinet yet.

Compared to a dual opposed MFW in a sealed box? While a pair of 15s makes for a capable sub, I doubt you could get 21 Hz at 115 dB with 300 watts into one dual-opposed MFW cabinet at less than 10% THD. I ran out of amp at 114 dB and ~5% THD.....

The sub mounts against the cutout inside the back chamber. The cutout and chamber are sort of visible in the picture of the insides in Post #1. There is plenty of room, I can fit a Tempest X2 in there with room to spare. I use Hurricane nuts and allen screws to mount the driver. Since I've started properly installing hurricane nuts, I've not had problems.

Here's how I install hurricane nuts:
Drill the right size hole in the right places (with a backer board to avoid chipout),
slightly countersink the flange side (opposite the driver),
clean the hurricane nuts with acetone or brake cleaner,
start a hurricane nut in the hole,
apply PL to the shank with a bent wire,
drive it in place with a hammer,
repeat as necessary,
then chase the threads with a tap when the PL is dry.

Here is a pic with a few notes about what goes where.



Here's a view (sort of) looking inside the chamber through the baffle. Pardon the messy shop.

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post #73 of 1740 Old 04-25-2011, 05:04 PM
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ok so the 20" tall I can work with. Only about 3 inches to spare before it reaches the bottom of my screen. so laying it in the orientation the the pictures show, I wont have a problem. the 29" deep might cause a little disturbance to the walking path with the coffee table pushed out for reclining, but this seems a decent compromise for the distortion measures you state above vs two sealed how is the planned design walkthrough coming Mike?

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post #74 of 1740 Old 04-25-2011, 05:15 PM
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only thinking along the terms of placement of the interior panels here. Did i mention this will be my first horn build?

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post #75 of 1740 Old 04-25-2011, 05:22 PM - Thread Starter
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@ beastaudio

I have lots of diagrams, I'm still working on the text though.

It would actually help me improve the assembly instructions if I can work with someone that has not built a horn before. Would you be interested in reviewing the directions once I get them put together? I'd really appreciate your input.
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post #76 of 1740 Old 04-25-2011, 05:37 PM
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Quote:
Originally Posted by MX48 View Post

Thanks Mike. That sounds like the best plan. Would the new opening be the same dimensions as the original?

He is coming to my house Friday for a demo (I have multiple subwoofers). So I am sending him into the deep end. He also may be interested in my speakers (JTR T8's). If he buys mine I want Danley's.

Moto

You will DEFINITELY be sending this guy off the deep end. With IB, THT, and MadMax churning out clean sonic brutality, pandora's box will have been opened....off topic, but did you ever measure the big horn outside?

JSS
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post #77 of 1740 Old 04-25-2011, 07:27 PM
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Can't wait to build a pair! I'm not ready just yet but hope to be soon enough.
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post #78 of 1740 Old 04-25-2011, 08:28 PM
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Just picked up 3 sheets of 3/4" plywood from Lowe's. I hope to start the build this weekend.
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post #79 of 1740 Old 04-25-2011, 08:35 PM - Thread Starter
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Open call to all potential builders.

Basic cutting and assembly instructions will be posted at the bottom of post one in the next day or so - please review and comment if you think I can improve things. It is probably best to keep the comments and feedback to PMs to keep the thread cleaner.
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post #80 of 1740 Old 04-25-2011, 09:22 PM
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Today it rained, so I double boxed 35 of the MFW's in case anyone needs any.
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post #81 of 1740 Old 04-25-2011, 10:15 PM
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Today it rained, so I double boxed 35 of the MFW's in case anyone needs any.

Just sent u a PM :-)
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post #82 of 1740 Old 04-25-2011, 10:28 PM
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Quote:
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Open call to all potential builders.

Basic cutting and assembly instructions will be posted at the bottom of post one in the next day or so - please review and comment if you think I can improve things. It is probably best to keep the comments and feedback to PMs to keep the thread cleaner.

One thing I noticed that would help is if you could add the required angles of the cut on the boards it is necessary with. Being familiar with Sketchup I was able to figure them out but to the novice builder I'm sure it would be beneficial to them.

I also believe some cuts could be made straight as long as your using an expanding adhesive. (PL premium which is readily available is great for just that.)
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post #83 of 1740 Old 04-26-2011, 08:43 AM
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@ beastaudio

I have lots of diagrams, I'm still working on the text though.

It would actually help me improve the assembly instructions if I can work with someone that has not built a horn before. Would you be interested in reviewing the directions once I get them put together? I'd really appreciate your input.

PM sent to you Mike, Id be happy to take a look. I have two MFW's coming hopefully by the weekend so perhaps I will be able to embark on at least gettting the wood cut! The extra MFW perhaps will either be set in the back of the theater for response evening or something similar
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Is this thing going to be "Dog-safe?"

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post #85 of 1740 Old 04-26-2011, 10:46 AM - Thread Starter
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Is this thing going to be "Dog-safe?"

I dunno. My dog went and hid while I was testing. What aspect are you worried about?
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I dunno. My dog went and hid while I was testing. What aspect are you worried about.

Just dog's low freq. sensitivity issues, prbably why yours went and hid. I would probably make mine leave the room just to be safe... Not like this will deter me from building perhaps Ill make a set of ear plugs for the old bish

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post #87 of 1740 Old 04-26-2011, 01:28 PM - Thread Starter
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Just dog's low freq. sensitivity issues, prbably why yours went and hid. I would probably make mine leave the room just to be safe... Not like this will deter me from building perhaps Ill make a set of ear plugs for the old bish

Really - this does not do that much below 20 Hz. It is not designed to, the driver is the limit here.

I certainly wouldn't worry too much about it.

My dog has an aversion to loud noises, (4th of July is not a fun time....) and she is a bigger klutz than I am, so she gets tangled in and trips over the cords and cables, which can really mess things up during testing. Best for everyone if she just hides....
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I HEAR that. To be perfectly honest, im not sure if I have ever heard 20 hz properly before My dog is afraid of gunshots, other than that for the most part fearless. just didnt know if even at 20hz, their sensitive ears would take a hurting. she has been fine through all other bass testing so I cant imagine it will be too bad.

How do you think that this setup will run off my NHT ma-1a (about 120 watts @ 4 ohms) just temporarily until I get a better amp and what are the suggestions?

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post #89 of 1740 Old 04-26-2011, 03:16 PM - Thread Starter
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I HEAR that. To be perfectly honest, im not sure if I have ever heard 20 hz properly before My dog is afraid of gunshots, other than that for the most part fearless. just didnt know if even at 20hz, their sensitive ears would take a hurting. she has been fine through all other bass testing so I cant imagine it will be too bad.

How do you think that this setup will run off my NHT ma-1a (about 120 watts @ 4 ohms) just temporarily until I get a better amp and what are the suggestions?

If there is no boost in the wrong place, the NHT amp will be fine. It is only 80 watts, so it leaves about 6 dB on the table. I used a BASH 300 I had sitting around, it was about the right size. The BASH 300 is around $150, there are also some other options in the same price range, like the Apex Senior and the Dayton SA240. 300 watts into a 4-ohm load is all you need with the MFW driver.
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post #90 of 1740 Old 04-26-2011, 03:30 PM
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If there is no boost in the wrong place, the NHT amp will be fine. It is only 80 watts, so it leaves about 6 dB on the table. I used a BASH 300 I had sitting around, it was about the right size. The BASH 300 is around $150, there are also some other options in the same price range, like the Apex Senior and the Dayton SA240. 300 watts into a 4-ohm load is all you need with the MFW driver.

ok how about rack mountable options then? gotta stick with that if at all possible...

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