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Lilmike's Cinema F-20 - Page 10

post #271 of 1699
Thread Starter 
Quote:
Originally Posted by NicksHitachi View Post

that's good to know, although is it relevant to compare 1w spl behavior when most instances at those frequencies the power will be at the thermal rating of the driver? what does the horn do at 12hz 250w and no high pass? where do the lines cross on that comparison? Wouldn't it be making all kinds of bad sounds by then?

All the above are posed as questions, and based on possible misconceptions

In real life use - the sub might see 100W transients, most of the time the power applied will be under a watt.

In a nutshell, the numbers all get bigger, but the relationships do not change.

Here are the same comparisons as presented above, except done at 250 watts.

Excursion:



SPL:



The SPL lines still cross at 12 Hz. The horn is 10 dB louder at 20 Hz.

At 12 Hz, the model suggests that the driver in the horn will be moving +/-17 mm, which is over xmax, but still within the driver's xmech. Same power into the sealed box has the cone moving +/-27 mm. While the driver in the horn would certainly be distorting, the driver in the sealed box would be complaining audibly, possibly even experiencing mechanical contact (coil into backplate), because that is 7 mm over the 20 mm xmech on this driver. Clanking is FAR worse than a bit of harmonic distortion.

Clearly - I made the sealed box too large. Oopsies....

Let's try again, with a smaller sealed box, just to be fair.

250 watt comparison, 118 L sealed box vs. the F-20.

Excursion:



SPL:



OK, now when we feed it 250 watts, we can't clank the driver above 10 Hz in the sealed box. As before, we can clank the driver in the horn at a few select frequencies..... Still, the horn's excursion for the great majority of frequencies below 80 Hz is still equal to or lower than the sealed box, even when we get below the horn's corner. The horn excursion is lower than the sealed box below 14 Hz, and continues to decrease as frequencies get lower, while the sealed box excursion rises slightly as frequencies decrease.

But....look what has happened to the SPL....

The lines don't cross at 12 Hz anymore. In fact - they don't cross at all on this plot. The spread at 20 Hz is now 12 dB. It takes a single driver in a sealed box over 10X the power (over 2500 W!!!) to equal the horn's SPL at 20 Hz, or it would take 4 drivers in sealed cabinets, each at 250 W. 4X the drivers, 4X the power.

Sealed boxes have a resonance and roll-off too. When you make the sealed box smaller to control the driver's excursion, you also raise the resonance of the enclosure, which reduces the low frequency SPL.

Sure - there is still the out of band distortion issue as I discussed earlier. I just wanted to show a comparison of the two to try and clarify things. Sealed boxes may go "low" but they do not do "low" and "loud" all by themselves.

Clearly, there are lots of ways to get to reference level at 20 Hz. This time, I chose to get there with a single 15" driver and 2.25 4X8 sheets of plywood.
post #272 of 1699
Quote:
Originally Posted by turdlepoker View Post


I'm trying to get another MFW from Erich ASAP to start building on a second.

I got your message. I will take it up to FedEx today.
post #273 of 1699
Thread Starter 
Quote:
Originally Posted by Rob Flanery View Post

This is a strictly theoretical question as my wife would probably put rat poison in my meat loaf if I added a second box.

Having said that, how would you orient the mouth of two horns side by side in the front of the theater.

...

Mmmmm, d-Con.....

I'd try a pair with the mouths separated, near the side walls first. Spreading the mouths may result in a null due to the distance between the sources, but you don't know till you try. This was actually the smoothest setup in my room when I was running dual subs. Centered may yield a smoother response, but gives up the corner loading. All I do know is that every room will be different.

"Honey,? Please pass the......"

Thud. /body hits floor....
post #274 of 1699
I was eating meatloaf as you said that, unfortunate. Luckily it wasnt home-made

I will have a spare MFW once the tempest gets here Monday so if anyone is interested in either one of mine, I can part with it. Also perhaps the second one should i decide to rock another tempest and the second cab.
post #275 of 1699
Thread Starter 
Quote:
Originally Posted by turdlepoker View Post

I have done some placement experimentation in my room and found with the mouth facing into the room rather then corner loading it's less localizable. However, corner loading gave me a 6-7db gain (Once, I build a second for the other corner it will fix the localize issues and balance the room).

I am using a Behringer a500 amp right now and it is sufficient power with just one channel. However, I can clip the amp at exactly -0 (reference level on my receiver) so maybe a little more power would be nice or when I build the second it will give the extra headroom needed. I can peg my RS SPL meter at 126 DB at 21hz test tones. I haven't used any EQ yet and by ear it is pretty darn flat. I am gonna try and get some REW measurements this weekend.

I'm trying to get another MFW from Erich ASAP to start building on a second.

Great design LiLMIKE!

Btw, I've heard both the THT and now the F-20. The tonal quality seems alittle more
solid with the F-20. I dunno if this is due to the design or the room differences or the sub itself. But I can definitely detect a different tone.

Thanks. Looking forward to seeing your in-room measurements.

Just wanna clarify....you're metering 126 at your LP? at 21 Hz?

If so.....NICE!
post #276 of 1699
Yes, when corner loaded I was able to peg the digital RS meter at 126 DB. At that point I didn't hear any distress with the sub but was on the last LED before clipping. Not quite at my listening position. About 9' from the subs mouth. I had the meter sitting on a tripod in sight from where I was at the amp to adjust gain. I can test at listening position later, that's at 14' from the subs mouth.

Keep in mind I have a medium sized room at about 2,900 cubic feet, with windows duck taped and doors weather stripped. It's about at sealed as I can get it.
post #277 of 1699
Thread Starter 
That's excellent.

You shouldn't stress the sub with that amp. According to the model, you don't have enough power to hit the driver's 20 mm xmech, except right at 19 Hz. Keep in mind - the models are inherently conservative, as they are lossless, non-resonant, and are based on low-level Thiele-Small parameters.

It did not complain with all 300 of the watts my BASH 300 could deliver.

So - I'll try the BASH 500 tomorrow.....
post #278 of 1699
Quote:
Originally Posted by turdlepoker View Post

Yes, when corner loaded I was able to peg the digital RS meter at 126 DB. At that point I didn't hear any distress with the sub but was on the last LED before clipping. Not quite at my listening position. About 9' from the subs mouth. I had the meter sitting on a tripod in sight from where I was at the amp to adjust gain. I can test at listening position later, that's at 14' from the subs mouth.

Keep in mind I have a medium sized room at about 2,900 cubic feet, with windows duck taped and doors weather stripped. It's about at sealed as I can get it.

You were getting that with NO EQ as well as no HPF? I am too nervous to run that hard without the high pass in place!

ALSO, what gauge wire are you all running to the f-20? Im currently using 12 but was thinking perhaps 10?
post #279 of 1699
Quote:
Originally Posted by lilmike View Post

That's excellent.

You shouldn't stress the sub with that amp. According to the model, you don't have enough power to hit the driver's 20 mm xmech, except right at 19 Hz. Keep in mind - the models are inherently conservative, as they are lossless, non-resonant, and are based on low-level Thiele-Small parameters.

It did not complain with all 300 of the watts my BASH 300 could deliver.

So - I'll try the BASH 500 tomorrow.....

Oh cool.... Let us know the details with the 500 watt amp. I'm curious to see when she complains.
post #280 of 1699
Quote:
Originally Posted by beastaudio View Post


You were getting that with NO EQ as well as no HPF? I am too nervous to run that hard without the high pass in place!

ALSO, what gauge wire are you all running to the f-20? Im currently using 12 but was thinking perhaps 10?

Yes, no EQ and no HPF. I didn't do any crazy tests below 20hz. Once I get the measurements done I will set a HPF in place according to my discoveries.

I am just running 12 gauge and I think that is more then fine. Only reason to go larger is if your running strands more then 50ft and even then it might not be needed.
post #281 of 1699
Quote:
Originally Posted by turdlepoker View Post

Yes, no EQ and no HPF. I didn't do any crazy tests below 20hz. Once I get the measurements done I will set a HPF in place according to my discoveries.

I am just running 12 gauge and I think that is more then fine. Only reason to go larger is if your running strands more then 50ft and even then it might not be needed.

with a box in the rear location, it would be pretty close to 50ft, I was just curious
post #282 of 1699
Thread Starter 
Quote:
Originally Posted by beastaudio View Post

You were getting that with NO EQ as well as no HPF? I am too nervous to run that hard without the high pass in place!

ALSO, what gauge wire are you all running to the f-20? Im currently using 12 but was thinking perhaps 10?

I use 14 gauge for a 30 foot run.

12 gauge is plenty big.
post #283 of 1699
Thread Starter 
Quote:
Originally Posted by turdlepoker View Post

Oh cool.... Let us know the details with the 500 watt amp. I'm curious to see when she complains.

Me too....

I'm expecting that I'll have excursion troubles with high power sine waves between ~18 and ~22 Hz. The driver did not complain during a sine wave sweep that started at 10 Hz at 300 watts, but the SPL plot did show a hint of compression, so I think I was getting close.

I expect some movies will make bad noises happen too.

With music? I don't expect any issues at all, but I don't typically listen to things that are mixed to destroy subs like Opus Dei.

I just hope that I don't melt the voicecoil former. The house will stink for a week.....
post #284 of 1699
Quote:
Originally Posted by beastaudio View Post

Im currently using 12 but was thinking perhaps 10?

10 gauge is more trouble than it's worth, trust me. I use it. Cost me $75 for a hundred foot spool, and it was a waste of money. My QSC amp barely takes the stuff on the binding posts, my Speakons are a pain to wire up with the stuff, and in general it's totally unnecessary for most applications.
post #285 of 1699
lilmike,

Not sure if you have heard a DTS-10 but, you've probably seen some numbers. I was curious to know what your thoughts about two of the F-20's vs. one DTS-10, not in extension but, from say 20Hz up output wise? I could build two of these on the cheap and I could potentially shrink my screen wall depth in the dedicated room I am building in the basement. I already have a Yamaha XP3500 with 450w x 2 and it has a 20Hz 12db hi-pass filter. Not sure of the driver I could use with my power but, you said different ones could work well. Thoughts? Thanks!
post #286 of 1699
Thread Starter 
Quote:
Originally Posted by Tom Bley View Post

lilmike,

Not sure if you have heard a DTS-10 but, you've probably seen some numbers. I was curious to know what your thoughts about two of the F-20's vs. one DTS-10, not in extension but, from say 20Hz up output wise? I could build two of these on the cheap and I could potentially shrink my screen wall depth in the dedicated room I am building in the basement. I already have a Yamaha XP3500 with 450w x 2 and it has a 20Hz 12db hi-pass filter. Not sure of the driver I could use with my power but, you said different ones could work well. Thoughts? Thanks!

I've not heard a DTS-10 yet, but I'd like to. I've definitely seen some good measurements, and there have been plenty of discussions.

Hmmmm. One DTS-10 vs 2 F-20s...

From 10 Hz to 20 Hz? Not a fair fight. The F-20s will make noises, sure, but it is mostly going to be distortion. I did not design it for use below 20 Hz.

The DTS-10 has a claimed 2.83 V sensitivity of 100 dB from 15 to 70 Hz. Bear in mind that the 2.83 V is being delivered into two 4 ohm drivers that are wired in parallel, or essentially a 2-ohm load, so that is a 4 watt number. The F-20 measured 94 dB at 2.00 volts into 4 ohms, so it would also be 100 dB at 4 watts. Adding one more F-20 fed with the same power? Add another 6 dB, or 100 dB at a watt to each.

The primary issue here is power handling. The DTS-10 can handle a lot more power than the F-20 with an MFW. 300 watts per MFW means you'll see ~25 dB of headroom from the 1 watt number of 100 dB for the pair, or a theoretical max SPL of ~125 dB at 20 Hz. The DTS-10 with 2KW applied? I calculate 127 dB, which is generally in line with Danley's specs.

If you go with the Tempest X2 or the AE 15 you can definitely increase the power handling, but the driver costs go way up. Seems like a lot of cost and effort for 2 dB, especially when power compression will likely negate half the difference.
post #287 of 1699
Got a Crown 402D amp on the way. I think 400 watts x2 should be fine. Going to get to work on the F-20 boxes this weekend
post #288 of 1699
Thanks everyone for the input on the wire gauge, I have a plethora of 12 gauge so I wil just stick with that! I didnt have a chance to get anything done last night but I did get to listen to some good tunes, order the behringer mic, and a few more speaker box terminals (I didnt have one so right now the wire is just coming through the access panel with a load of PL to seal it up) I plan today on getting the flat paint to finish it, anyone have suggestions? I was just going to go with valspar flat black as Ive used it on some other areas of the theater and it would match up nicely
post #289 of 1699
Quote:
Originally Posted by blackoper View Post

Got a Crown 402D amp on the way. I think 400 watts x2 should be fine. Going to get to work on the F-20 boxes this weekend

I was between that and the 1500, figured I would give the class D Tech a try for a few more bucks! That amp will match up nicely tho!
post #290 of 1699
What version of minidsp plugin do I need for this anyway? I'm thinking two way advanced. I'm going to have two F-20s and then maybe later adding a Clark Synthesis Platinum Transducer or two to a platform
post #291 of 1699
Quote:
Originally Posted by blackoper View Post

Got a Crown 402D amp on the way. I think 400 watts x2 should be fine. Going to get to work on the F-20 boxes this weekend

This amp I believe to be perfect for this application. If I could pick one up cheap I would.
post #292 of 1699
I am building 4 F-20's for my theater.
post #293 of 1699
Quote:
Originally Posted by MKtheater View Post

I am building 4 F-20's for my theater.

Your ears will love you but your friends will love you even more! Where you putting all of them?
post #294 of 1699
Quote:
Originally Posted by MKtheater View Post

I am building 4 F-20's for my theater.

Are you really? :-) I plan to have 4 at some point.
post #295 of 1699
Quote:
Originally Posted by turdlepoker View Post

This amp I believe to be perfect for this application. If I could pick one up cheap I would.

How cheaply? $239.90 +20ish to ship from midwest pro sound and lighting is what I went with. http://www.midweststereo.com/Crown-A...n-xls-402d.htm
post #296 of 1699
Quote:
Originally Posted by blackoper View Post


How cheaply? $239.90 +20ish to ship from midwest pro sound and lighting is what I went with. http://www.midweststereo.com/Crown-A...n-xls-402d.htm

Dang that's a good price.... I'll look into that. Thanks for the link.

I was going to run my EP4000 to power 2 on each channel but that's about 300w per driver. The 402 would give just a touch more headroom.
post #297 of 1699
Quote:
Originally Posted by MKtheater View Post

I am building 4 F-20's for my theater.

I'd be very interested to hear how they sound compared to the two DTS-10's you had. Not the below 20Hz I understand but, from 20Hz up.
post #298 of 1699
Quote:
Originally Posted by Tom Bley View Post

I'd be very interested to hear how they sound compared to the two DTS-10's you had. Not the below 20Hz I understand but, from 20Hz up.

I wil measure them for response and distortion and create a new build thread. I am curious how much low end I will miss because I was used to reference to 10hz and below.
post #299 of 1699
Quote:
Originally Posted by MKtheater View Post

I wil measure them for response and distortion and create a new build thread. I am curious how much low end I will miss because I was used to reference to 10hz and below.

What happened to the 18.2's?
post #300 of 1699
Quote:
Originally Posted by louisdamani View Post

What happened to the 18.2's?

Gone.
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