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Lilmike's Cinema F-20 - Page 41

post #1201 of 1695
I'm a noob and all but I did read that section of the article posted and it was my interpretation that the amp required a min. of 1.4v (or whatever is listed on the amp).. I didn't take from it that you should bring that voltage down especially since the listed spec is a "max" of 4.6v and the article states that a more realistic output would be 30% less - in this case around 3.2v..

Sorry if I'm throwing a kink in the discussion.. did I misunderstand the article?
post #1202 of 1695
The thread provided a 60Hz sine wave that one could download and burn to DVD.
post #1203 of 1695
Quote:
Originally Posted by lilmike View Post

I even showed you the math....but I'll say it again.

There is not an appreciable difference.

Mike...I am never challenging your assertions. I only say "Lilmike would say" in order to qualify my reply. Who gives a crap what opinions are offered by "dutchswan0311"
post #1204 of 1695
For reference my onkyo sub pre-out voltage is so high i have to bump the mains 10db and set sub trim to -15db(min setting) to avoid clipping the BFD>>Amp. They both clip about the same time and the input sensitivity of the EP4000 is about the same 1.something volts.

IMO you should have PLENTY preout voltage on a sub out, maybe too much as is my situation.
post #1205 of 1695
Started construction and ran into a bit of a potential problem.
The circle I cut may be too big?
I have a Dayton Reference HF and it doesn't really have room to move around before the bracing hits the sides, yet the holes line up like this.


If I am careful will it be OK?


Another question I ran into. How exactly do I mount the driver. Do I drop it through on the horn side into the chamber (the rim on the horn side)? or do I mount it to the baffle from the chamber side(all parts of the driver on one side)?

Thanks.
post #1206 of 1695
@shinyav....the second image looks fine. That is where your mounting holes should be. The first image does not look circular and your mounting hole in that image looks off.

You will mount the woofer on the chamber side.
post #1207 of 1695
Alright thanks for the reply, going to look at it a bit more perhaps its sitting a little off.
post #1208 of 1695
Thread Starter 
Can also spin the driver around a touch, mounting hole orientation does not matter.
post #1209 of 1695
Alright pretty sure I was able to make it work. some of them were hanging off the edge a bit. I have seen others like that after googling and plan to just dremel them off. I used liberal amounts of PL, cleaned them very well and plan to tap them. I don't think this will be a point of failure.

Besides that all the wood is cut. I will probably bevel tomorrow morning and assemble sat night.
post #1210 of 1695
Mine were really close too. I actually had one of them split through when I drilled it for the hurricane nut. I just filled it with PL and used a wood screw in that hole.
post #1211 of 1695
I preseated the driver and it looks like I don't even need to trim them. The foam of the cone came no where near the overhang of the hurricane nuts.
post #1212 of 1695
Quote:
Originally Posted by Shinyav View Post

I preseated the driver and it looks like I don't even need to trim them. The foam of the cone came no where near the overhang of the hurricane nuts.

If the image below is what you are talking about, then you are fine. I put together a pretty thorough build thread for my first F20. You might find a couple of useful pointers in there.

post #1213 of 1695
here's what we did on my build.

post #1214 of 1695
Yep got mine to look pretty similar and covered them in PL
Gonna be finishing it up tonight/tomorrow morning. However, no amp till mid next week
post #1215 of 1695
Alright, all done, painted positioned etc.
Feels really awesome.
No where near calibrated but just turned it on at 2am.
Was able to blur my vision though with some test tones.

Only real problem I ran into was one of the nuts came out. Ended up being able to get it fixed. Then the second time I was mounting it one came out again... However it was basically fully tightened so it seems to be fine. Will be a pain if I ever want the driver out.
post #1216 of 1695
Quote:
Originally Posted by Shinyav View Post

Alright, all done, painted positioned etc.

pics, or it didn't happen. :P

Quote:
Originally Posted by Shinyav View Post

Feels really awesome.
No where near calibrated but just turned it on at 2am.
Was able to blur my vision though with some test tones.

and that's what I'm loving about this sub. dial it in, and it'll be that much better.
post #1217 of 1695
Alright just got home from work after only a few hours of sleep





There we go, sorry about the dirty room in the process of redoing everything.
It does look a bit big but wow it absolutely pounds
With audyssey calibration it only needs to be at about 7oclock(1 dash line) to require 0db of adjustment. So at half way it makes me feel like my walls are gonna fall down and my ears explode. I tried it all the way down to 17hz and I can certainly understand wanting to go lower. However, I am very happy.

Just some safety questions before I really start messing around..
I am using a Dayton Audio RSS390HF-4 15" and a Bash 300w.

Is there any possible way I can damage this sub/driver/amp with those two? Anything I should avoid doing?
Is running sine waves OK? at all frequencies? etc etc.
For an amp the volume dial, are they linear for how much watts they supply?
For say 300w, half of the max on the dial gives it 150w? a quarter 75w?

I ran it once at about 75% and with sine waves from 17-50 and didn't hear anything that sounded bad. But only for a few seconds and then I thought I should make sure I have a decent understanding first.

Thanks everyone for all the replies in this thread which I read several times.
and especially thanks to lilmike for helping a huge newb have an amazing sub.

Edit: Watched a couple movies and listened to some music and feels its fairly boomy. Going to move it under my TV perhaps and use it as a stand of sorts.

Edit 2:
post #1218 of 1695
Quote:
Originally Posted by Shinyav View Post

Edit: Watched a couple movies and listened to some music and feels its fairly boomy. Going to move it under my TV perhaps and use it as a stand of sorts.

i ran into this as well, but because of its size i wasn't able to move it around. instead, I moved my primary listening spot forward to where the bass was no longer boomy.

your room itself plays just as much of a role in the sub's sound. I have a BFD to further eq the sub, but just haven't had the time to mess with it yet.
post #1219 of 1695
That BFD got rid of any "boomy" in my DTS10's. You likely have some excited frequencies in your room that need knocking down.

Shiny, are you using that box fan to suppliment the F20 and get you down into single digits.
post #1220 of 1695
Quote:
Originally Posted by tony123 View Post

That BFD got rid of any "boomy" in my DTS10's. You likely have some excited frequencies in your room that need knocking down.

Shiny, are you using that box fan to suppliment the F20 and get you down into single digits.

What's a BFD?

Also, that fan comment had me laughing out loud!
post #1221 of 1695
Behringer Feedback Destroyer

A nice inexpensive parametric EQ. There are a vast array of BFD guides on usage etc, because it's a bit counterintuitive due to us HT enthusiasts using it instead of it's intended use in Proaudio.

BFD

Here's a very good, step by step guide,... on it's usage



Good luck
post #1222 of 1695
lol@box fan sub, will be replaced with blackout curtains soon.

The new setup with it laying down in the middle improved.. at least to my ears.. the bass a lot. I went with a AV receiver with multieq xt. Seems to help as well.

Anyone get a chance to look at the questions in my previous post? I really want to demo the sub pretty aggressively tomorrow for Easter (isn't that how everyone celebrates?) but still do it without risk of damage.
post #1223 of 1695
Mine was a little boomy at first too. I upgraded to a Denon AVR1912 (From a 15 year old Yamaha HTR-5220 with no equalizer) and ran Audyssey Multieq and it improved it a lot. My main goal with the Denon was to help out the raspy center channel and it fixed both problems. The F20 really is a great horn. I am still amazed by it everyday.
post #1224 of 1695
Quote:
Originally Posted by Shinyav View Post

lol@box fan sub, will be replaced with blackout curtains soon.

The new setup with it laying down in the middle improved.. at least to my ears.. the bass a lot. I went with a AV receiver with multieq xt. Seems to help as well.

Anyone get a chance to look at the questions in my previous post? I really want to demo the sub pretty aggressively tomorrow for Easter (isn't that how everyone celebrates?) but still do it without risk of damage.


Do NOT use Dynamic EQ, and use the Audio Test DVD (sticky on this forum), with the -0.5dB LFE tones, and monitor voltage to the F20. Turn it up until you reach 18-20 Volts with the tones. I would not put more than 20V into it, unless you are above 23Hz, then you can push to almost 30V. the difference between 20 and 30V is about 3.5dB. You will impress the hell out of people with 12V going through this thing, far away from Xmax or any bad noises, and with plenty of clean headroom.

JSS
post #1225 of 1695
Quote:
Originally Posted by maxmercy View Post

Do NOT use Dynamic EQ, and use the Audio Test DVD (sticky on this forum), with the -0.5dB LFE tones, and monitor voltage to the F20. Turn it up until you reach 18-20 Volts with the tones. I would not put more than 20V into it, unless you are above 23Hz, then you can push to almost 30V. the difference between 20 and 30V is about 3.5dB. You will impress the hell out of people with 12V going through this thing, far away from Xmax or any bad noises, and with plenty of clean headroom.

JSS

I guess I don't fully understand.
Dynamic EQ basically boosts bass? I can understand not using that for this purpose.
The voltage from the receiver going to the amp? use a multimeter on the RCA cable from the sub preout?
What about the vol knob on the amp itself?

Thanks.

Perhaps I should make a new post as these questions are not really directly related to the f-20.
post #1226 of 1695
What is max safe power with high pass 24db/oct @20hz?

Mostly concerned with excursion not thermal as its for HT.
post #1227 of 1695
Thread Starter 
Quote:
Originally Posted by NicksHitachi View Post

What is max safe power with high pass 24db/oct @20hz?

Mostly concerned with excursion not thermal as its for HT.

Which driver?

Your 24 dB highpass would cut power at 10 Hz by 24 dB, which essentially cuts 300 watts down to ~2 watts. 15 Hz would be cut by 12 dB, which turns that same 300 watts into about 19 watts.

Things should be fine excursion-wise. I'd personally worry more about the thermal limits, cause there is plenty of content above 25 Hz that will send a lot of power through that voice coil.

Are you planning to listen to 15 Hz sine waves or just watch movies? You can force any driver in any cabinet to make bad noises if you try hard enough.

There really is not an excursion issue with a reasonable amount of power and the proper driver in this cabinet, save for the peak right at the cabinet's tune. That peak is from 15 Hz to 22 Hz or so. It is no different than the other home-theater front-loaded sub horns out there in that regard, DIY or pro.

I'm not worried about displacement, I recommend the highpass primarily because I prefer not to send signals that are out of the sub's operating bandwidth to the sub - no sense increasing the distortion for no meaningful increase in SPL or extension.

I fed my MFW 300 watts with a 12 dB/oct highpass at 20 Hz and had no issues, even with 20 Hz sine waves at over 115 dB 1m groundplane. That's more than 20 volts.....
post #1228 of 1695
Quote:
Originally Posted by lilmike View Post


Which driver?

Your 24 dB highpass would cut power at 10 Hz by 24 dB, which essentially cuts 300 watts down to ~2 watts. 15 Hz would be cut by 12 dB, which turns that same 300 watts into about 19 watts.

Things should be fine excursion-wise. I'd personally worry more about the thermal limits, cause there is plenty of content above 25 Hz that will send a lot of power through that voice coil.

Are you planning to listen to 15 Hz sine waves or just watch movies? You can force any driver in any cabinet to make bad noises if you try hard enough.

There really is not an excursion issue with a reasonable amount of power and the proper driver in this cabinet, save for the peak right at the cabinet's tune. That peak is from 15 Hz to 22 Hz or so. It is no different than the other home-theater front-loaded sub horns out there in that regard, DIY or pro.

I'm not worried about displacement, I recommend the highpass primarily because I prefer not to send signals that are out of the sub's operating bandwidth to the sub - no sense increasing the distortion for no meaningful increase in SPL or extension.

I fed my MFW 300 watts with a 12 dB/oct highpass at 20 Hz and had no issues, even with 20 Hz sine waves at over 115 dB 1m groundplane. That's more than 20 volts.....

thanks mike, duh yes the Dayton DVC which has a bit more thermal capacity.......

thanks that answers my question as far as excursion, looks like PE quotes 600w RMS(maybe) for the thermal rating so id be inclined to think as far as burst content(HT) 500w would be ok? Forget sine waves at tuning, thats ridiculous! :P Since your pretty comfortable with the excursion i might recommend a 12db slope to leave a little sub 20 on the table......
post #1229 of 1695
Thread Starter 
Issue with a horn (any horn) is that distortion will rise below Fc.

That's the fundamental reason why I highpass.

500 watts into the DVC with a 12 dB highpass at 20 should be OK, but I don't have one to test, so I can't be sure.
post #1230 of 1695
I had the gain at one dash from max.
Receiver volume at 0db and sub 6db hot.
Played a bunch of stuff from movies to dubstep to short sine waves.
Could see it in peoples faces that this was a new experience.

All is well and I did not hear a single thing that sounded questionable(anyone have a link to what bad things would sound like?).
I really need to buy a spl meter. Extremely curious what numbers I am getting.
I feel like it could take more
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