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-   -   New forum member, new OB project (http://www.diyaudio.com/forums/multi-way/210837-new-forum-member-new-ob-project.html)

siruis815 16th April 2012 01:01 AM

New forum member, new OB project
 
*** Most recent updates (9-1-12) are found here. ***


Hello everyone.

I am a new-ish member to this awesome site and since the wife has just ok'd a new project, I thought I'd start a thread for the build and of course comments and suggestions. But first a background.
I've always been interested in audio, starting first with car stereo systems in high school and venturing into home audio once my car was complete. Some years ago, I set out to create a large 3-way tower which I never saw to completion due to my work schedule.

I became increasingly interested in open baffle designs early last year and decided to take the three way system I had laying in the garage and place them into an open baffle. More research revealed the lack of low-end common in these setups so I decided to include a 12" car audio woofer (MB Quart) in a U-frame, effectively creating a 4-way.

http://farm8.staticflickr.com/7251/6...68ece888_z.jpg

I'm using a Behringer EP2000 for the amplifier and running a 50Hz high pass - equalization is done via a +10db bass boost on the home theatre receiver - yes I know not the best solution, but it doesn't sound too bad. And sadly I don't have the equipment to measure the output.

For the very bottom end, I built two sonotube towers tuned to ~20Hz - also running 12s, low passed at 50Hz.
Back to the present:

I've been eyeing the countless projects on this site, as well as others, and the bug keeps biting at me to build :D. I'm pretty set on staying with open baffles, however I also want to work with some FR drivers. So here's what I'm looking at.
2x MCM 21" woofers (@119 each!)
1x Audio Nirvana Super 12
1x some tweeter, possibly a LPG 25NFA mounted above the AN 12 cone as in the Hammer Dynamics Loudspeaker

http://farm6.staticflickr.com/5116/6...722f97fe_z.jpg
I'm planning on running a 30Hz high pass on the woofers via the EP2000 and using the receiver for a 50-70Hz lowpass to the "subwoofer", then adjust gain to compensate for bass-drop along with using the bass boost on the receiver. Once again, not the most elegant solution, but until I decide to either get an ultracurve or a mini-dsp, this'll have to do.

I may run the Super 12 with only a highpass at ~100-150hz and no low pass. The tweeter will come in between 5 and 10k (will have to experiment with my ears).

So, with all that said, how's it look? Also, anybody know what the efficiency of the AN12 is? Hopefully the 92dB of the tweeter will complement the AN12 well.

Cheers,
Ben K.

Edit: I should mention this project may take a few months to come to completion. The MCM woofers are on order, but work is keeping me from diving right in. Plus it gives me time to adjust plans if necessary.

zmyrna 16th April 2012 04:47 PM

How big is your room?
Those 21"ers may be an overkill.
Consider exchanging them for 15".
On a recent forum discussion most experienced diy'ers agreed that the upper limit for musical woofers were 15"
If you decide to keep them, at least consider putting them on a separate baffle.
Otherwise your main baffles will rattle like crazy.
On another note, you should keep the woofers close to the floor for bass gain.
Are the AN drivers low qts? I remember so.
In that case, you would be better of with a 8-12" driver of around 0.7 qts.
And no whizzer cone please.

siruis815 16th April 2012 06:35 PM

My room isn't overly large, but I do like my music on the louder side. 21s were my choice to mainly further low end extension without going H-frame. I looked long and hard at the alpha-15s, but decided on the MCMs instead. And I understand the 21s won't be as musical, but to play up to maybe 150hz at very low extension they should be alright.

My original plans called for putting both woofers below the FR, however that would put the FRs center at ~52 inches off the floor - a bit high for the sitting position. I'll have to draw up some more plans. Do you think a 3" baffle would still rattle too much? I plan on using 3 1" layers.

I believe the AN12 has a qts anywhere from .26-36. A little on the low side, but should be fine down to 100ish Hz with it being a 12. I also had the 15 in mind, however I don't know for sure about the 150 dollar price increase. I haven't 100% settled on which AN driver yet.

What do you mean by no whizzer cone? As I understand, the ANs all come with whizzers.

For reference, my current baffles are ~40 inches tall.

EDIT: Anybody in the Raleigh area want to come by and measure my current system?

jim1961 16th April 2012 06:57 PM

If this intended to be a full range speaker, I wouldnt recommend running a 12" woofer up to 5-10k at all.

siruis815 16th April 2012 07:05 PM

The AN are full rangers no? I figured they should be good up to at least 5k. I do plan on having the tweeter in there for the very high end.

chris661 16th April 2012 09:37 PM

Quote:

Originally Posted by zmyrna (Post 2987565)
On a recent forum discussion most experienced diy'ers agreed that the upper limit for musical woofers were 15"

Citation needed please: I've heard good and bad both sides of that border.

A pair of 21"s a side may well be considered overkill (call it headroom ;) ). But I'm sure that none of your friends/family/whatever have seen woofers that big before: I'd go for it for the wow factor.

I'd consider going for a 12" coaxial for the midrange and up.

Chris

jim1961 17th April 2012 02:27 AM

Quote:

Originally Posted by siruis815 (Post 2987759)
The AN are full rangers no? I figured they should be good up to at least 5k. I do plan on having the tweeter in there for the very high end.

My concern was the off axis response mostly.

siruis815 17th April 2012 02:59 AM

Off axis response is partly why I am swaying towards using the Super 12 with a 1" tweeter to cover 5k+ freqs.

I am 100% set on using the 21s as they are already purchased. Do you guys think the upper 21 will be okay above the FR?

Thanks for all the reply's so far. Keep them coming! Pics of the drivers will hopefully be uploaded by Saturday night :D

siruis815 17th April 2012 03:24 AM

I've also been eyeing the 8" L Cao fullrange driver that popped up on the forums.

zmyrna 17th April 2012 10:53 AM

Sirius,
Yes the AN driver is indeed a fullranger.
It is designed to be a point source/fullrange in a big box.
If you are having a 3 way design there is not much point in AN.
And yes they all have whizzer cones and there is also no point in a wc if you are going to add a tweeter. If you have to use the AN12 then perhaps you can remove the wc.
But then I haven't seen successful OBs using AN drivers. That says sth. It is probably better to use a 8" with 0.7 qts rather than a 12" with lower qts.
My suggestion for bass:
Use one 21" per side with a plate amp if necessary. Put the 21" on a separate baffle.
And then build a 3 way main baffle:
Tweeter
8" mid with qts around 0.7
and one or two filler 12" woofers below the mid.
I can't remember the forum reference for the musicality comment. But the argument is that over 15" two things happen:
1. cone gets too heavy
2. cone breaks more easily because of large surface
So it is probably best to use such big drivers for only under 50Hz with a steep crossover.


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