Lilmike's Cinema F-20 - Page 4 - AVS Forum
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DIY Speakers and Subs > Lilmike's Cinema F-20
lilmike's Avatar lilmike 03:36 PM 04-26-2011
The Behringer A500 is decent, but leaves a little bit on the table power-wise, and won't do a 4-ohm load bridged. A small pro-amp like the little Crown, Peavey, or Marathon might be a decent option too.

beastaudio's Avatar beastaudio 03:44 PM 04-26-2011
Quote:
Originally Posted by lilmike View Post

The Behringer A500 is decent, but leaves a little bit on the table power-wise, and won't do a 4-ohm load bridged. A small pro-amp like the little Crown, Peavey, or Marathon might be a decent option too.


The crown 202 http://www.crownaudio.com/amp_htm/xls.htm seems to fit the bill, although it wouldnt be bridged either. Do you just pick a channel and have the AVR send it the LFE signal as usual?
lilmike's Avatar lilmike 04:20 PM 04-26-2011
That does not look bad at all. Might be hard to find brand new though - I think that model has been superseded by the XLS 1000. The new one has some nice features, but they sort of missed the boat on the DSP crossover functions.

Yup, wiring it up is simple as that. Adjust gains properly and you're good to go.
lilmike's Avatar lilmike 11:13 PM 04-26-2011
Updated the Cutlist in Post 1 to match the instructions I'm working on.
Erich H's Avatar Erich H 11:23 PM 04-26-2011
Quote:
Originally Posted by lilmike View Post
Updated the Cutlist in Post 1 to match the instructions I'm working on.
Both side panels can be cut from 1 sheet of Baltic. Can the rest of it be cut from 1 other sheet?

The Anarchy was cut from 1 sheet of 1/2" and packed up it weighed 36lbs. That didn't take the full sheet though, but a good chunk of it. Average shipping was between $18 - $28.

This bigger one.......shipped in two boxes?????? Maybe $200 max to your door?


I should shut up.
turdlepoker's Avatar turdlepoker 12:52 AM 04-27-2011
Quote:
Originally Posted by Erich H View Post
Both side panels can be cut from 1 sheet of Baltic. Can the rest of it be cut from 1 other sheet?

The Anarchy was cut from 1 sheet of 1/2" and packed up it weighed 36lbs. That didn't take the full sheet though, but a good chunk of it. Average shipping was between $18 - $28.

This bigger one.......shipped in two boxes?????? Maybe $200 max to your door?


I should shut up.
Don't shutup!!!!

Lots of people would love a sub that can be shipped to them ready for assembly.
lilmike's Avatar lilmike 12:59 AM 04-27-2011
Quote:
Originally Posted by Erich H View Post
Both side panels can be cut from 1 sheet of Baltic. Can the rest of it be cut from 1 other sheet?

The Anarchy was cut from 1 sheet of 1/2" and packed up it weighed 36lbs. That didn't take the full sheet though, but a good chunk of it. Average shipping was between $18 - $28.

This bigger one.......shipped in two boxes?????? Maybe $200 max to your door?


I should shut up.
Nope - it is ~2 2/3 60X60 sheets. 22 3/4" X 60 left as scrap from the last sheet
beastaudio's Avatar beastaudio 01:21 PM 04-27-2011
Is there anything else i will need to run in the signal path? necessary EQ or DSP or whatever? I am unfamiliar with in-line stuff like that but will get something and learn...
exojam's Avatar exojam 02:34 PM 04-27-2011
LM,

Sorry to go back to this, but those steps you outlined for me in post 23, would either a 3 or 5 ohm resistor work? I have some little Vishays in 3 and 5 but no 4 ohms ones lying around.

The 3 would be closest to the re of my sub(s) which is 2.7 (AV15-H).

Thanks again.

James
lilmike's Avatar lilmike 07:52 PM 04-27-2011
Quote:
Originally Posted by exojam View Post

LM,

Sorry to go back to this, but those steps you outlined for me in post 23, would either a 3 or 5 ohm resistor work? I have some little Vishays in 3 and 5 but no 4 ohms ones lying around.

The 3 would be closest to the re of my sub(s) which is 2.7 (AV15-H).

Thanks again.

James

I don't worry that much. I use 2.00 volts into 4 ohms for a 4-ohm nominal speaker and 2.83 volts into 8 ohms for an 8-ohm nominal speaker.

I also use at least 10W power resistors. Not sure if the Vishay's you're referring to are 10W. The pic is a 120W 4-ohm power resistor like I use, and I've warmed it up pretty well.
LL
exojam's Avatar exojam 09:13 PM 04-27-2011
LM,

Thanks for the information. Both the 3 and 5 ohm ones are 25W.

James
lilmike's Avatar lilmike 10:34 PM 04-27-2011
Quote:
Originally Posted by exojam View Post

LM,

Thanks for the information. Both the 3 and 5 ohm ones are 25W.

James

Hmmm. Wire in the 3 ohm, set your voltage to 2.00, then try the 5 in its place, see if there is any variation. If the amp voltage behaves, you might be OK. Picking up a pair of 8 Ohm 20 W resistors at Radio Shack next time you drive by will have you set for 4, 8, and 16 ohm drivers, they're $2.50 each.
exojam's Avatar exojam 05:21 AM 04-28-2011
Thanks again LM.

James
Hawkson's Avatar Hawkson 05:49 AM 04-28-2011
How does this compare to the THT?
If a more powerful driver was installed, would this produce below 20hz? What specs in the driver are desireable in this design to produce sub 20hz?

Thanks!
Maxjr's Avatar Maxjr 12:51 PM 04-28-2011
lilmike, do you recommend screws to hold the boards in place while the PL dries, or is it ok to use 18 gauge brads?
lilmike's Avatar lilmike 07:18 PM 04-28-2011
Quote:
Originally Posted by Maxjr View Post

lilmike, do you recommend screws to hold the boards in place while the PL dries, or is it ok to use 18 gauge brads?

With 3/4" material, I use screws. I leave them in place. A little bondo on the screw heads, then sand and paint....

18 gauge brads might work, but 1 1/4" is probably too short, I'd suggest 1 3/4" minimum. I've not tried brads in horn construction with 3/4" material, but have used them successfully for years when building conventional cabinets out of MDF and ply.
lilmike's Avatar lilmike 07:28 PM 04-28-2011
Quote:
Originally Posted by Hawkson View Post

How does this compare to the THT?
If a more powerful driver was installed, would this produce below 20hz? What specs in the driver are desireable in this design to produce sub 20hz?

Thanks!

Both are offset-driver horns. The THT is big, the F-20 is bigger still, but is a different shape, which may fit some rooms better. While the THT is a touch smaller, the F-20 plays a touch lower. Both get plenty loud. The F-20 is fairly flat without a corner, the THT needs to be placed in a corner for the flattest response. The MFW driver works in both, as do more expensive drivers. In both cases, a more powerful driver will not lengthen the horn, which is what is needed to make the horn play lower. Horn length is what sets the low corner.

The wavelength of 15 Hz is about 23 meters, 20 Hz is about 17 meters. Admittedly - we're using quarter-wavelength designs here, but still - you would need 1.25 meters of additional horn length (which equates to about 2X the cabinet volume) to get to 15 Hz, as well as a driver that works to 15 Hz.

The 12-step program (Assembly instructions.... ) has been added to Post 1.
BruceD's Avatar BruceD 06:40 AM 04-29-2011
Say lilmike, I know you said you use the neutrik speakon connectors, so hopefully you can shed some light on the installation of the connector into the sub box itself.

I'm using the 2-pole version and have measured the plastic cylinder of the connector body that fits into the sub cabinet with a caliper and get close to 59/64inches (0.9219inches).

So, I'm considering a forstner bit of 15/16inches (0.9375inches) to drill the hole througth the sub cabinet and use some kind of glue/caulk in the hole/on the inside cabinet to seal the speakon connector airtight.

Any recommendations from users who have done this before would be appreciated.
lilmike's Avatar lilmike 08:51 AM 04-29-2011
Quote:
Originally Posted by BruceD View Post

Say lilmike, I know you said you use the neutrik speakon connectors, so hopefully you can shed some light on the installation of the connector into the sub box itself.

I'm using the 2-pole version and have measured the plastic cylinder of the connector body that fits into the sub cabinet with a caliper and get close to 59/64inches (0.9219inches).

So, I'm considering a forstner bit of 15/16inches (0.9375inches) to drill the hole througth the sub cabinet and use some kind of glue/caulk in the hole/on the inside cabinet to seal the speakon connector airtight.

Any recommendations from users who have done this before would be appreciated.

I use a 15/16" Forstner bit, works great.

A little bit of PE speaker caulk or duct seal under the flange and around the barrel has worked as a sealant so far. The F-20 has a speakon through the access cover, and it sealed up fine using this method.
Maxjr's Avatar Maxjr 07:43 PM 04-29-2011
I've been thinking about the access cover a bit lately and have been wondering if there is a secure way of making it flush mounted with the rest of the side panel? This will give users the flexibility to lie the cab on its side on either of it's largest panels without having the access panel in the way. It will also add a bit to aesthetics. However, the speaker terminal will also most likely be mounted on the access panel, so maybe the point is moot? What do you guys think?

On my anarchy build, I skipped the access cover all together and ran the speaker wires straight out through the mouth of the horn. This made a simpler build and skipped me having to buy and mount terminals. However, this being a front loaded horn (instead of a tapped horn), I don't have that option anymore.
lilmike's Avatar lilmike 08:11 PM 04-29-2011
I made it like this:


I used the cutout for the access panel to fill the hole, and added a flange inside to fasten it to.

Sorry if the instructions are not clear enough on this, guess I could have added pictures.
lilmike's Avatar lilmike 08:33 PM 04-29-2011
Quote:
Originally Posted by Maxjr View Post

I've been thinking about the access cover a bit lately and have been wondering if there is a secure way of making it flush mounted with the rest of the side panel? This will give users the flexibility to lie the cab on its side on either of it's largest panels without having the access panel in the way. It will also add a bit to aesthetics. However, the speaker terminal will also most likely be mounted on the access panel, so maybe the point is moot? What do you guys think?

On my anarchy build, I skipped the access cover all together and ran the speaker wires straight out through the mouth of the horn. This made a simpler build and skipped me having to buy and mount terminals. However, this being a front loaded horn (instead of a tapped horn), I don't have that option anymore.

Lots of options.

Drill a hole in the bottom of the chamber, wire it out the mouth.
Drill a small hole in the chamber where it is needed, run the wire through, and put the input wherever you want.

I'm lazy. That's the only reason it is where it is...
Maxjr's Avatar Maxjr 08:49 PM 04-29-2011
That's exactly what I was thinking about! Looks great. Thank you for the picture! It's worth a thousand words. I think I may go with your suggestion and drill a hole through the chamber and run the wire out of the mouth. What do you recommend to use to patch around the speaker wire in the hole area?

Also, this question may not be the best posed here, but I just thought of it and haven't read the answer in any other horn thread. What is the life expectancy of the driver in a horn? Is it expected to be less or significantly less than the same driver in a sealed or ported enclosure? I'm just thinking out loud here and wondering how the effects of the horn loading affect the driver's life.
Hawkson's Avatar Hawkson 06:04 AM 04-30-2011
Quote:
Originally Posted by lilmike View Post

You're welcome.

As it looks currently, I'll have 4 designs in my Cinema series, each with a variation or two. I have models and ideas for folds for a large tapped horn with a single 15" driver, and an F3 below 20 Hz, but I don't have a dimensioned fold yet, nor do I have a driver to work with.

Here's the remainder of the Cinema Series (as I see things now):

Cinema F-20 (this thread) with a stretched variant that's in the works. The stretched one (F-24) will play a little lower, but might need a more capable driver.

Cinema T-6 (coming very soon - fold is done, plans are done, multiple suitable drivers in hand, my initial beta was a fail, but the current refold's beta results are great) Tapped horn with an 8" or 10" driver, cabinet is 6 cubic feet, F3 of ~28 Hz, single 4X8 sheet of 1/2" plywood. Widths will vary based on the driver used, 11.75" internally is about the limit for an unbraced cabinet, no point in going wider, the aspect ratio of the throat (width/depth) gets too large IMO.

Cinema T-12 (coming soon, model is done, fold is sketched, scaled plans are started, drivers are in hand and need a proper home) Tapped horn, 12 cubic feet, F3 of 20 Hz, 10" or 12" drivers, two sheets of ply. Widths will also be varied on this one, and it might get a stretch, all of this depends on the results of the beta build.

Cinema T-16 (a little further out, model is done, fold is sketched, but I currently have no suitable drivers to test with, though I am working on that too...)
Tapped Horn, 16 cubic feet, F3 ~17 Hz, 15" drivers, less than 3 4X8 sheets of ply. As with the T-12, widths will be varied on this one, and it might also get a stretch, this all depends on the results.

My design goals for these?
Capable of at least 115 dB in a groundplane setting within 1/2 octave of F3.
No more than a 6 dB drop from 2 octaves above F3 to F3.

Can you comment on what will happen with your T-12/T-16/F20s etc when placed in a corner? Will the attainable flat frequency drop?
Hawkson's Avatar Hawkson 06:14 AM 04-30-2011
Also, whats the sound quality difference between a Tapped horn and a FLH?
NicksHitachi's Avatar NicksHitachi 07:17 AM 04-30-2011
Heeey Mikey lookin good!


psgcdn's Avatar psgcdn 07:24 AM 04-30-2011
Quote:
Originally Posted by Maxjr View Post

What is the life expectancy of the driver in a horn? Is it expected to be less or significantly less than the same driver in a sealed or ported enclosure? I'm just thinking out loud here and wondering how the effects of the horn loading affect the driver's life.

I openned up 1973 Klipsch La Scala and 1978 Klipschorns and the drivers were immaculate and still sound great. No foam surrounds here though.
lilmike's Avatar lilmike 10:41 AM 04-30-2011
lilmike's Avatar lilmike 10:50 AM 04-30-2011
Quote:
Originally Posted by Hawkson View Post

Also, whats the sound quality difference between a Tapped horn and a FLH?

There is a difference. Some prefer tapped, some prefer front- or back-loaded horns.

For subs - which IMO, is all tapped horns as I currently design them are really good for, the sound of a PROPER driver in a PROPER tapped horn is hard to beat, when you weigh the remainder of the compromises. I've listened to both, but I am no golden ear. I listen to music and movies, not cables, op-amps, and capacitors...I've been known to play MP3s.....and vinyl is what my rain gear is made of....

I like a capable system, which requires a capable sub, I like my dynamics. I do listen at 100 dB or more on occasion.... Horns (tapped or otherwise) deliver the dynamics when I get them right.

I'm willing to sacrifice bandwidth to DC and go through the effort of a complex cabinet design and build to get the dynamics I desire in the rest of the bass spectrum out of fewer drivers and fewer watts of amplification.
lilmike's Avatar lilmike 11:34 AM 04-30-2011
Quote:
Originally Posted by psgcdn View Post

I openned up 1973 Klipsch La Scala and 1978 Klipschorns and the drivers were immaculate and still sound great. No foam surrounds here though.

I opened up an old Karlson K15 cabinet I found when I bought my place a few years back. The Altec Biflex driver was still in fine shape. While not exactly a horn, it is a sort of bandpass, and loads both sides of the cone. That cabinet was older than I am, and judging by the stories, it had seen some use over the years.

Only driver I've killed in a horn thus far was a thermal failure, and was clearly a result of operator error....that pic is posted over in one of the Anarchy threads.

I've not torn a cone or ripped a surround yet. I've pushed the drivers fairly hard too. I'm not exactly setting out to kill drivers, but I do want to know where the limits are. Things typically sound bad or smell bad before they break, so I tend to turn it down before the bad stuff happens.
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