Lilmike's Cinema F-20 - Page 6

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.

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.

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.

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?

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

so as I stated before on this amp, it would be just fine to fly solo without the HP?

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.

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.

Awesome, I have enough clearance in my build then

Sweet Beans! Let me know if you need anything else.

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.

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

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.

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.

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?

MIC2200 would also be a great option.

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.

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

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.

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.

Thank you, lilmike. It's very kind of you to answer that thoroughly.

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?