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Lilmike's Cinema F-20 - Page 6

post #151 of 1695
Not sure if I read this anywhere, but will this build need a HP filter?
post #152 of 1695
Quote:
Originally Posted by beastaudio View Post

Not sure if I read this anywhere, but will this build need a HP filter?

I'm not 100% sure on this but I believe you can run without one. You could use one and set to 20hz aswell.
post #153 of 1695
Quote:
Originally Posted by beastaudio View Post

Not sure if I read this anywhere, but will this build need a HP filter?

If you don't run a HP filter you will run out of Xmax extremely quickly below the 20Hz tune of the horn. You don't absolutely need a HP filter if you only listen at very low levels but it is a must if you plan to push it at all.
post #154 of 1695
Total NOOB question, what is a HP (high Pass) filter? Is there a link you point me to so I can read up on this? I am considering making two 20 horns and want to make sure I am educated on the amplification side before I get in too deep. I think that I can get the building side down.
post #155 of 1695
was looking at the crown xls402 as an amp option but it shows on site that its freq response is 22hz-20khz @ +/- 1 dB. Will this be a problem?
post #156 of 1695
Quote:
Originally Posted by dsully444 View Post

Total NOOB question, what is a HP (high Pass) filter? Is there a link you point me to so I can read up on this? ...

Wiki is your friend; redirects rumble filter as well. Scroll down to audio section.
http://en.wikipedia.org/wiki/High-pass_filter

The idea is that the driver is supported by the air in the horn, but that air is only supported by the horn walls and it's own mass in the throat. As driving frequency drops below tune (20Hz here), 2 things happen.
- the mass of air in the throat now has time to escape, so air pressure at the driver drops, reducing cone support and allowing greater excursion.
- the driver impedence falls from a peak at horn resonance toward DCR at 0Hz. Look at the impedence charts in post #1 to see what I mean.

So, below Fc, current to the driver increases but acoustic loading is reduced, so there's nothing to prevent overexcursion at power levels much lower than you might want to drive them.

The fix is a simple electrical filter that reduces amp output below the tuning frequency. It allows frequencies above, say, 15Hz to pass. It's a "high-pass" filter because it lets through higher frequencies. Many sub amps have one built in. Here's an example (see Chart 1 on page 12).
http://www.oaudio.com/docs/manual_v1_6.pdf

You also use a high-pass filter in a tweeter crossover circuit, but at a very different frequency.

Make sense?
Frank
post #157 of 1695
Thread Starter 
Quote:
Originally Posted by tsloms View Post

If you don't run a HP filter you will run out of Xmax extremely quickly below the 20Hz tune of the horn. You don't absolutely need a HP filter if you only listen at very low levels but it is a must if you plan to push it at all.

Actually, in this design, excursion peaks at 19 Hz, then decreases. This is not a tapped horn.

As a rule, I recommend high pass filters when the amp has greater bandwidth than the sub (read - in most cases). I already posted this somewhere, but perhaps it bears repeating.

When you're operating below a horn cabinet's passband, you're operating in an area where distortion, specifically the 2nd harmonic, can be louder than the fundamental. Even if you're within the driver's mechanical and thermal limits, your distortion levels are through the roof and things sound bad as a result. In my opinion, it is FAR BETTER to amplify the signals that your driver/cabinet combination can reproduce than it is to waste power amplifying things below the cabinet's passband that lead to high levels of distortion or possibly even driver damage.

Admittedly, I do tend to turn things up to 11 from time to time, so mechanical limits are a concern as well.

For the F-20, a highpass at 20 is suggested for these reasons.
post #158 of 1695
Quote:
Originally Posted by beastaudio View Post

was looking at the crown xls402 as an amp option but it shows on site that its freq response is 22hz-20khz @ +/- 1 dB. Will this be a problem?

so as I stated before on this amp, it would be just fine to fly solo without the HP?
post #159 of 1695
Thread Starter 
If you're gonna play that....

Quote:
Originally Posted by lilmike View Post

......

Highpass at 20.

Quote:
Originally Posted by lilmike View Post

.....but it would not be a bad idea to run a 20 Hz highpass.

Quote:
Originally Posted by lilmike View Post

......Any of these amps will need a separate highpass, something like a MiniDSP can do that as well as loads of EQ to correct the room response issues.

Plate amps? There are a few options. I ran the test mule with a BASH 300 and had no problems at all. The Dayton 240 might also be a good option, but I don't have any experience with those. You would probably want one amp per cabinet. Most plate amps will need a filter modification for the highpass. This is usually as simple as swapping a pair of resistors.

Quote:
Originally Posted by lilmike View Post

......

For the F-20, a highpass at 20 is suggested for these reasons.

Honestly, I think I've covered this. I've even kept it consistent.

-1 dB at 22 Hz is not a highpass. You'll probably be OK at reasonable levels, but with the XLS402, you've got plenty of power on tap to clank coils into backplates.

I've clearly stated that I recommend a highpass at 20 Hz. I've even explained why.

They're your drivers. Do as you wish.
post #160 of 1695
didnt mean to upset you mike, I have read through the whole thread, and saw each suggestion that you just posted, I just thought it might be different with an amp that had a range of 22hz^ as opposed to others than run 10hz^. My main concern was actually more along the lines of the amp rolling off at 22 as opposed to 10 and what effect that would have in conjunction with a HPF set at 20. I guess I just didnt go into enough detail. Ive never heard bass that low the way it should be heard and dont want to buy an amp that will in the end, screw it all up. mounting the amp is the easiest part after all Once again my apologies.
post #161 of 1695
Quote:
Originally Posted by turdlepoker View Post
No problem, I have one just sitting here waiting to go into the F-20 so it was no big deal. :-)
Wait, does the 7" thickness count the magnet?
post #162 of 1695
Quote:
Originally Posted by diaz View Post

Wait, does the 7" thickness count the magnet?

Yes, that is from the gasket to the base of the magnet. The whole height of the woofer.
post #163 of 1695
Quote:
Originally Posted by turdlepoker View Post

Yes, that is from the gasket to the base of the magnet. The whole height of the woofer.

Awesome, I have enough clearance in my build then
post #164 of 1695
Quote:
Originally Posted by diaz View Post

Awesome, I have enough clearance in my build then

Sweet Beans! Let me know if you need anything else.
post #165 of 1695
Quote:
Originally Posted by beastaudio View Post

I just thought it might be different with an amp that had a range of 22hz^ as opposed to others than run 10hz^. My main concern was actually more along the lines of the amp rolling off at 22 as opposed to 10

1) It's not going to roll off any more than most other amps do.
2) Rolling off cannot be a substitute for a high pass. It just doesn't work that way.
post #166 of 1695
Got it! going to go find a mini DSP to do the job One concern I have so far that I noticed last night is that where my sealed MFW 15 is currently sitting, in the front of the room between the mains (where the f-20 is going), the bass response up close is decent, tails off a bit for the second row seating, but then on the back wall it is rediculously bassy. Im hoping the f-20 will correct some of this as its really the only place I can locate the cab...fingers crossed
post #167 of 1695
Just looked through some of the mini dsp thread, that thing sounds like it is way more in depth than I can comprehend. is that what is best to use to HP and eq the f-20? what are the other options?

This perhaps? http://www.marchandelec.com/xm9.html
post #168 of 1695
Thread Starter 
Quote:
Originally Posted by beastaudio View Post

Just looked through some of the mini dsp thread, that thing sounds like it is way more in depth than I can comprehend. is that what is best to use to HP and eq the f-20? what are the other options?

This perhaps? http://www.marchandelec.com/xm9.html

At 6X the price? I'll take a MiniDSP and the change please.

Really - nothing comes close for the money, otherwise, we'd use/recommend it instead.

For highpass, all you really need is the XM-1, but that still requires a case and power supply, hence the MiniDSP suggestion, as it costs about the same when it is all said and done, and does considerably more for the money spent. Another option is the Behringer Mic 2200, they also cost ~$100, but only have a 12 dB/octave highpass and a few EQ options, but they do have a tube.....
post #169 of 1695
Quote:
Originally Posted by beastaudio View Post

Just looked through some of the mini dsp thread, that thing sounds like it is way more in depth than I can comprehend. is that what is best to use to HP and eq the f-20? what are the other options?

This perhaps? http://www.marchandelec.com/xm9.html

Some people have had good results with an "Elemental Designs EQ.2" it has a Filter on it aswell. Price is $100.
post #170 of 1695
a tube? of toothpaste? that is good cause im almost out

which one of those suggestions is the easiest to just set the HP? I guess depending on room response to the f-20, it would help to have some eq, but doesnt seem to me that I would need much, not near as much as the mini offers! if once I have it, it is easy to program and leave set, i dont have a problem with that, I just got swamped by revA vs revB and quad whatever etc etc.
post #171 of 1695
Thread Starter 
The Reckhorn is probably easiest, the eD is up there too. Plug it in, turn the knobs till you've got what you need, then let it sit.

MiniDSP is probably not the easiest, but there are no knobs to mess with either....

With a pro amp? You could use the balanced version of the MiniDSP. I use the kit version, as I can select "A" or "B" with a jumper. I use an old cell phone charger for power currently, but I am making a separate cabinet for it.

The MiniDSP requires some effort, true. It also does a lot.
post #172 of 1695
knobs seem a little more up my alley since my laptop sucks and I would rather twist knobs than hook everything up through the pc everytime I wanted to adjust. seems that both the reckhorn and the Ed are out of stock so i will have to start scouring to find one somewhere... ill probably go with the ED, looks most like my speed...

Know anywhere to buy one other than direct from Ed?
post #173 of 1695
MIC2200 would also be a great option.
post #174 of 1695
Quote:
Originally Posted by beastaudio View Post

knobs seem a little more up my alley since my laptop sucks and I would rather twist knobs than hook everything up through the pc everytime I wanted to adjust. seems that both the reckhorn and the Ed are out of stock so i will have to start scouring to find one somewhere... ill probably go with the ED, looks most like my speed...

Know anywhere to buy one other than direct from Ed?

I did a little hunting for you and found a Reckhorn S-1 (their top of the line model) for $95+ Shipping. Here is the link: http://cgi.ebay.com/Reckhorn-S-1-Ele...item35a305a63f

Also... Here's a link to the owners manual so you can see just how easy it is to use. http://www.reckhorn.com/manual/manual_s1.pdf

If you would rather have the ED send me a PM as I have a EQ.2 here I might be willing to part with.
post #175 of 1695
Quote:
Originally Posted by turdlepoker View Post
Also... Here's a link to the owners manual so you can see just how easy it is to use. http://www.reckhorn.com/manual/manual_s1.pdf
I have a B-2... it will be replaced by a MiniDSP before too long. The EQ on it can have some rather interesting side effects on the highpass:



10Hz highpass, 20Hz 50% boost. I'm surprised this didn't clank the drivers of my 16Hz tapped horn. The B-2's highpass is otherwise pretty reliable without the EQ. This is how I learned to measure these things with REW before letting them process LFE at reference levels
post #176 of 1695
You cannot properly set the Reckhorn or eD devices without REW, in my experience. The dial-it-knob isn't accurate and may not even be labeled properly, in some instances. You MUST use REW to experiment with knob settings to see what you're actually getting.

So this means, IMO, that both the Reckhorn and eD are not easier for a beginner than the MiniDSP, which actually does what it says it's going to do.

Sure, you can frack around with an SPL meter & test tones, but that's still a PITA compared with the MiniDSP for people who just want to set a high pass filter.
post #177 of 1695
lilmike, do you think it would be possible to make the box slightly narrower, i.e., to make the shortest side even shorter?

I would really welcome 2 and perhaps even 1 inch for where I would need to put a beast like this.


EDIT: I'll be wanting to use an MFW-15 driver.
post #178 of 1695
Thread Starter 
Maybe, but let me run the model to be sure. Minimum is 17" external, or the driver will not fit.

EDIT:

At the absolute minimum width (15.5" internal/17" external), the valleys increase in depth by a few dB, so the response is not as flat, but it is still acceptable in my opinion. The low corner is essentially unchanged, as length is unaltered.



Construction should be similar, it will still require more than two sheets of plywood. Internal panels that are 15.5" wide will likely make installation of the driver a bit more challenging due to limited space in the chamber, but it should be possible.
post #179 of 1695
Quote:
Originally Posted by lilmike View Post

Maybe, but let me run the model to be sure. Minimum is 17" external, or the driver will not fit.

At the absolute minimum width (15.5" internal/17" external), the valleys increase in depth by a few dB, so the response is not as flat, but it is still acceptable in my opinion.

Thank you, lilmike. It's very kind of you to answer that thoroughly.
post #180 of 1695
Quote:
Originally Posted by CZ Eddie View Post

You cannot properly set the Reckhorn or eD devices without REW, in my experience. The dial-it-knob isn't accurate and may not even be labeled properly, in some instances. You MUST use REW to experiment with knob settings to see what you're actually getting.

So this means, IMO, that both the Reckhorn and eD are not easier for a beginner than the MiniDSP, which actually does what it says it's going to do.

Sure, you can frack around with an SPL meter & test tones, but that's still a PITA compared with the MiniDSP for people who just want to set a high pass filter.

so you wouldnt need the use of REW with miniDSP? I thought this, as well as a mic was necessary to do any type of eq'ing in general? If just setting the HP filter as I stated is all that is necessary, then the miniDSP is a piece of cake?
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