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questions about the f-20

post #1 of 25
Thread Starter 
hey guys , i work in a gym in a small town , twice a month we hold 2 partys/dances

one for the school kids 18 and under
and another for 19-22 lil older , most of the music they want is dubstep techno. our system consists of 2 seismic audio enforcer 2 18's , each driven by a bridged ab international 600a amp which is 750 w rms.

the subs are loud but lack anything below 40hz , they do sound great with rock/metal music though , but for dubstep they just arent cutting it .

originally i was looking at the lab sub , unfortunately i have minimal wood working tools, im a welder by trade, so building it would be a lil hard trying to make all those beveled cuts with a circular saw.

then i came across the f20 easy to build cheap drivers etc etc, im wondering how well u guys think this would work for my application

the room is around 2,600 sq ft and it fills with aprox 80-100 ppl
im looking for about 115-120db average with peaks in the 125 range, im getting about 112/113db average out of the sa 18's now

or would u guys suggest a different sub enclosure
post #2 of 25
As the guy that conjured up the F-20, I'll chime in.

You'll need more than one of them, I would start with 4.

I have another option that will do 20 Hz, and is actually a bit louder at a watt than the F-20 is. I'd still start with 4 in your situation.
post #3 of 25
Thread Starter 
Quote:
Originally Posted by lilmike View Post

As the guy that conjured up the F-20, I'll chime in.

You'll need more than one of them, I would start with 4.

I have another option that will do 20 Hz, and is actually a bit louder at a watt than the F-20 is. I'd still start with 4 in your situation.

thanks i was hopping u would reply, been reading a bunch of the threads on the f20, 4 is out of the budget for the time being , i have enough cash on hand today to build 2, am actually making the 120 mile trip to my nearest home depot tomorrow to pick up wood and supplies

in order to save money what do u think about 3/4 mdf with extra bracing inside the box?, this will be a permanent install so i wouldnt have to worrk about cracked corners etc ? the savings may allow me to build 4 instead of 2 at a time ?

what is ur other option besides the f20 i am all open to ideas
post #4 of 25
Thread Starter 
hmm dont see a way to edit my previous post so i forgot to mention size of the enclosures is pretty much a non issue
post #5 of 25
I hate MDF.

It is heavier than ply, and not as stiff as ply. You'd be better off with OSB than MDF, and I prefer plywood.

2 would be a decent start. Remember - these are not PA subs, and will be a bit lower efficiency that typical PA tops, which is why I suggested 4.

The other option is what I have called the MicroWrecker. It is still a 20 cubic foot cabinet, it does 20 Hz, but it is a tapped horn, not a front-loaded horn.

Though I used a Kicker CVX 15, the MicroWrecker can be loaded with an Alpine Type S 15, which delivers a lot of SPL for the $$. Mine will blow out a candle at three feet.

The F-20? If you jumped today (and I mean like right now) the Ultimax 15 from PE is a decent fit. The driver isn't on sale after today though. Other than that? The Reference HF 15 works well.

Do you have a way to highpass or provide sub EQ? Both these cabinets benefit from highpassing and EQ.
post #6 of 25
Thread Starter 
Quote:
Originally Posted by lilmike View Post

I hate MDF.

It is heavier than ply, and not as stiff as ply. You'd be better off with OSB than MDF, and I prefer plywood.

2 would be a decent start. Remember - these are not PA subs, and will be a bit lower efficiency that typical PA tops, which is why I suggested 4.

The other option is what I have called the MicroWrecker. It is still a 20 cubic foot cabinet, it does 20 Hz, but it is a tapped horn, not a front-loaded horn.

Though I used a Kicker CVX 15, the MicroWrecker can be loaded with an Alpine Type S 15, which delivers a lot of SPL for the $$. Mine will blow out a candle at three feet.

The F-20? If you jumped today (and I mean like right now) the Ultimax 15 from PE is a decent fit. The driver isn't on sale after today though. Other than that? The Reference HF 15 works well.

Do you have a way to highpass or provide sub EQ? Both these cabinets benefit from highpassing and EQ.

yes i have two 31 band 2 channel eq's in the rack , along with a 2/3way x over

do u have a link to plans for the microwrecker?
post #7 of 25
No link yet, haven't done a formal thread.

Between work and my remodel, I barely have time to sleep...

PM me an email address, I will send you the layout and cut list. No fancy plans for the Microwrecker either, just another thing I have not finished...
post #8 of 25
Thread Starter 
thanks sending u a pm now
post #9 of 25
Thread Starter 
thanks lilmike im curious which one do u think would be better for me the f20 or the lilwrecker
post #10 of 25
Thread Starter 
im sorry micro wrecker or the f20

somehow i ende dup with the cutsheets for the lilwrecker lol
post #11 of 25
LiLMike- what do you consider to be the best of all your designs for someone wanting strictily the best home theater performance with regards to 1.) extension and #2.) output?

Can the UM15 be used in the F20, and if so, would that be an upgrade over the Alpine Type S, or the Kicker CVX-15?
post #12 of 25
Well, to answer the "which is better" question, I guess it all comes down to personal preference.

I liked the F-20, but I like the MicroWrecker more. The F-20 is a decent horn, and the MFW is a decent driver. Nothing at all wrong with it.

I am listening to the MicroWrecker now, and I plan on building it a partner as soon as my schedule permits.

I have one driver that works in the F-20, I have a pair that work in the MicroWrecker.
The F-20 did not fit into the space I had, the MicroWrecker does.
The F-20 was not a design for me, the MicroWrecker is, and is a design I have been working on for years.
post #13 of 25
Quote:
Originally Posted by Martycool007 View Post

LiLMike- what do you consider to be the best of all your designs for someone wanting strictily the best home theater performance with regards to 1.) extension and #2.) output?

Can the UM15 be used in the F20, and if so, would that be an upgrade over the Alpine Type S, or the Kicker CVX-15?

As far as what's best? Not my call, don't know your room or your preferences. As far as extension and output, both these designs (F-20 and MicroWrecker) don't quite go as deep as I'd like in my theater. The LilWrecker or Housewrecker might be a better fit if you have the room.

Re the driver discussion - You're mixing apples and oranges here.

The F-20 is a well-documented front-loaded offset-driver horn. In addition to the recommended drivers discussed in the thread, it can also use the Dayton UltiMax 15. The UltiMax was discussed in the design thread.

The MicroWrecker is a completely different tapped horn design that has not been fully documented as of yet, but seems to work well so far. That one was designed for the CVX, but the Alpine Type S works in it too.
post #14 of 25
Regarding the F20, couldn't a person effectively increase the length of the horn if putting it in the corner? For example, if you had one F20 along the North wall facing East and another F20 along the East wall facing North, you have added a column from floor to the top of the F20 which should drop the tuning point another couple Hz, right?
post #15 of 25
Quote:
Originally Posted by Looneybomber View Post

Regarding the F20, couldn't a person effectively increase the length of the horn if putting it in the corner? For example, if you had one F20 along the North wall facing East and another F20 along the East wall facing North, you have added a column from floor to the top of the F20 which should drop the tuning point another couple Hz, right?

So - you're talking about adding an area between the F-20s that is 5 feet tall and 20" square, but would have no taper. Certainly - if effective, that change in horn length should change the tune. Effective is the key here, as typical walls are lossy, and some walls are worse than others. Also, the area of this column is smaller than the combined area at the mouths, and it lacks any taper. An initial (and somewhat limited) hack at a model doesn't look too pretty - there is a sizeable peak at 16.5 Hz. Remember though - models are just that - perhaps things work better in real life.

I guess I should have tried to measure that when I was running an identical pair of OD horns. Simple impedance sweeps of each arrangement would verify that "corner loading" as described actually changes the horn's tune.
post #16 of 25
Yeah I have just a tiny bit of knowledge about horns, so it seemed like an effective way of lengthening the horn...but I didn't think about mouth area and tapering.

What about doing what BFM calls "V-coupling"?
post #17 of 25
Quote:
Originally Posted by Looneybomber View Post

Yeah I have just a tiny bit of knowledge about horns, so it seemed like an effective way of lengthening the horn...but I didn't think about mouth area and tapering.

What about doing what BFM calls "V-coupling"?

Same sort of thing, except with a taper it is a bit easier to simulate.

Seems to me that done right, it can't hurt. Not sure how sturdy the plate would need to be though.

Wouldn't use that approach with a tapped horn unless I designed the cabinet to be V-plated, because adding length after the driver tap can really mess things up.
post #18 of 25
Cool. I have 4 MFW's that I'm trying to figure out what to do with. I was going to go sealed, but I no longer have a WAF to deal with and I want good extension into the teens.
post #19 of 25
Quote:
Originally Posted by lilmike View Post

As far as what's best? Not my call, don't know your room or your preferences. As far as extension and output, both these designs (F-20 and MicroWrecker) don't quite go as deep as I'd like in my theater. The LilWrecker or Housewrecker might be a better fit if you have the room.

Re the driver discussion - You're mixing apples and oranges here.

The F-20 is a well-documented front-loaded offset-driver horn. In addition to the recommended drivers discussed in the thread, it can also use the Dayton UltiMax 15. The UltiMax was discussed in the design thread.

The MicroWrecker is a completely different tapped horn design that has not been fully documented as of yet, but seems to work well so far. That one was designed for the CVX, but the Alpine Type S works in it too.


Well I wasn't asking what is best, per se, but rather which one goes the lowest and has the most output at both the low end, (ie 25hz & below) and output at the high end, (ie 40hz+ and up)?
How would the F-20 perform with the UM15 as opposed to the MFW-15?
Also, how would the F-20 with the MFW-15 driver compare to the actual stock MFW-15 in its original cabinet powered by an EP4000?
post #20 of 25
Also, lilmike, do any of your horn designs go down below 20hz with decent output? I would love to have a 10hz or 15hz capable subwoofer
& being that I do not have any WAF issues, I could go with as large of a cabinet as is necessary. I already have a pair of UM15's and a pair of
HO15's as well. Currently, I only have 1 of the UM15's in its cabinet and hooked up, the other will come later and the HO15's will likely go in my
vehicle.
post #21 of 25
For 15Hz, you want this one: http://www.avsforum.com/t/1451519/lilmikes-lilwrecker

No comment on those driver's suitability in the design, but if they're not in the driver list in the first post they're probably not suitable.

For 10Hz, forget it. Horns aren't at all practical with an F3 that low.
post #22 of 25
Both the UM15 and the HO15 lack enough motor force to be effective in a typical tapped horn.
They are better suited to use in an offset-driver/front-loaded horn if you want them in a horn, otherwise, they both work fine in sealed boxes.
post #23 of 25
Quote:
Originally Posted by Martycool007 View Post

Well I wasn't asking what is best, per se, but rather which one goes the lowest and has the most output at both the low end, (ie 25hz & below) and output at the high end, (ie 40hz+ and up)?
How would the F-20 perform with the UM15 as opposed to the MFW-15?
Also, how would the F-20 with the MFW-15 driver compare to the actual stock MFW-15 in its original cabinet powered by an EP4000?

Discussed the UM in the F-20 here.

It models well, reports back from builders are positive, but I've seen no measurements.
post #24 of 25
Quote:
Originally Posted by lilmike View Post

Discussed the UM in the F-20 here.

It models well, reports back from builders are positive, but I've seen no measurements.

Mike, just got a UM15 today. I have some house type projects to work on but will get going in a couple weeks on building an F20. I have no way of measuring but you could always come up for a day with your gear if you felt so inclined biggrin.gif
post #25 of 25
Quote:
Originally Posted by cogeng182 View Post

Mike, just got a UM15 today. I have some house type projects to work on but will get going in a couple weeks on building an F20. I have no way of measuring but you could always come up for a day with your gear if you felt so inclined biggrin.gif

Count on it. I'd love to get impedance, 1W SPL and some distortion measurements.

I'll have my calibrated mic situation sorted out by then if all goes as planned.
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