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Old 15th July 2012, 05:02 PM   #1
chops is offline chops  United States
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Talking Wanting to go OB again...

Rolling Back

A short while back I was planning on building my version of the GR-Research V-2's. I had purchased four of the Eminence Acoustinator N2012 drivers used in that speaker as well as the two SA-1 plate amps from Danny. However, instead of using the coaxial drivers that Danny used in that system, I had a pair of Mark Audio Alpair 10.2's that I was going to use.

Some unforeseen events came up and I had to abandon that project which also meant selling off the items I had bought. The amps sold but no one would bite on the N2012 drivers. I never tried selling the Alpair's.

I'm now in the process of selling off a few more items. Once they sell I'll be able to really get this new project going.


The Plan

So the new plan is to go a little different on the OB design. I've been doing a lot of searching around on the net and getting ideas on how to go about designing these new OB's.

I've already decided on using a pair of Hawthorne Audio 15" Silver Iris speakers for the top end. I want these speakers to cover as much of the audio spectrum as possible on the given baffle size, hence going with the 15's. I've read that these start rolling off around 60Hz or so, so I'll most likely just let them run flat out and roll off on their own.

I've also decided to go ahead and use the N2012 drivers instead of trying to sell them again. They have fairly decent specs for use on an OB, but I'm hoping I can improve on that with the next thing I'm going to talk about, which is...

"Aperture Bass Propagation technology", adopted from Emerald Physics. Basically, this increases the effective width of the baffle, thus increasing the ability of the driver to reach lower before cancellation starts. It is said that it also increases frontal output by up to 4dB starting around 40Hz vs the sound coming from the rear of the driver. Of course, that goes for the Eminence Alpha 15A drivers that Emerald Physics uses in their design. Those numbers will probably be slightly different with the N2012 drivers I'll be using. I don't know if they'll be higher or lower numbers, but should still have the same effect more or less I imagine.


The tricky part of this whole project is that I want to run the entire setup off of one amp, my Monarchy Audio SM-70 Pro. It's Class A and rated at 25w x 2 @ 8 ohms and 40w x 2 @ 4 ohms.

I would like to simply run an inductor across the woofers for a 50-80Hz crossover point. I figure the N2012's will have a combined efficiency of roughly 98dB @ 1w/1m (at 1kHz). Add to that the extra 4dB from the Aperture Bass Propagation technology, so possibly around 102dB efficiency. However, at the frequencies these will be operating at, I'm probably looking closer to around 97-98dB, maybe less.

The Silver Iris 15's are rated at 95.8dB (96dB for all practical purposes), so if the bass section is operating in the 97-98dB area, they should be a pretty good match to the SI 15's at that point, not needing active crossovers and dedicated amps. I don't want to use any extra equalization either, except for the auto-EQ in my HT receiver. If I need more bass below these OB's, I still have a pair of Polk subs that are good down to 25Hz or so.

I'm shooting for a simple, minimalist design and only using the one amp which has loads and loads of woofer control.


Any thoughts, ideas, suggestions?

Many thanks in advance!
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Old 16th July 2012, 01:11 AM   #2
chops is offline chops  United States
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Wow... Eight hours and over 100 views, but not a single response. Hmm...


Anyway, also considering the Audio Nirvana Super 15 Cast Frame fullrangers as well. Actually, those are even more preferable since there's no crossovers involved.

Hopefully someone will pitch in here eventually.
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Old 16th July 2012, 01:15 AM   #3
Pano is offline Pano  United States
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I vote for the Manzanita Ultra. 3" FR and 15' GRS woofer. Simple crossover. Great speaker. You can spend a ton more money and get much more complicated for no more results.
Fast, fun, Inexpensive OB project
Some as the original Manzanita, but with bigger woofer and baffle.
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Old 16th July 2012, 01:48 AM   #4
chops is offline chops  United States
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Hate to say it, but that has absolutely nothing to do with what I'm doing here.
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Old 16th July 2012, 02:12 AM   #5
ScottG is offline ScottG  United States
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Quote:
Originally Posted by chops View Post
Hate to say it, but that has absolutely nothing to do with what I'm doing here.
..it's a loudspeaker, right? And even one that is open baffle!


I think that starting with the Silver Iris is sort of a "eh"..or at least that's why I didn't respond when I first read your post.

(..your large format horns + pro drivers were more interesting - at lest conceptually to me.)
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Old 16th July 2012, 02:16 AM   #6
chops is offline chops  United States
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How does either one of those posts have to do with the components and design I'm talking about?
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Old 16th July 2012, 02:21 AM   #7
ScottG is offline ScottG  United States
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Originally Posted by chops View Post
How does either one of those posts have to do with the components and design I'm talking about?
He is suggesting that you can get more for less in an open baffle design..

Same reason I look at the use of the silver iris and go "eh".
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Old 16th July 2012, 03:08 AM   #8
chops is offline chops  United States
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Well I'm not building these to impress anyone on the internet, so the "wow factor" to others isn't really a concern of mine. I'm looking at it from a price point/performance perspective. The Hawthorne's or AN's can get me there at a decent price. Another factor for me is overall size of the speakers as I'm working on some limited space.

I've already got $600 invested in bass drivers. In order to get proper compression drivers for the 511B horns (which I still have and already thought about) is gonna be another $500 from GPA. Not to mention, with the horns, I have no choice but to use more amplification, DCX2496, and whatever else needed. Plus, I don't know how well those N2012 drivers would perform up to the crossover point of 600-900Hz to blend into the horns.

Why are the Silver Iris drivers just "ho hum"? It's not like a little cheap 3" wide-range driver is overly exciting.


And keep in mind, I'm planning on these speakers to be fullrange all the way, not needing extra bass support from subwoofers.
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Old 16th July 2012, 03:50 AM   #9
ScottG is offline ScottG  United States
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Originally Posted by chops View Post
Well I'm not building these to impress anyone on the internet, so the "wow factor" to others isn't really a concern of mine.

..I've already got $600 invested in bass drivers. In order to get proper compression drivers for the 511B horns (which I still have and already thought about) is gonna be another $500 from GPA. Not to mention, with the horns, I have no choice but to use more amplification, DCX2496, and whatever else needed. Plus, I don't know how well those N2012 drivers would perform up to the crossover point of 600-900Hz to blend into the horns.



..I'm looking at it from a price point/performance perspective. The Hawthorne's or AN's can get me there at a decent price. Another factor for me is overall size of the speakers as I'm working on some limited space.


Why are the Silver Iris drivers just "ho hum"? It's not like a little cheap 3" wide-range driver is overly exciting.


And keep in mind, I'm planning on these speakers to be fullrange all the way, not needing extra bass support from subwoofers.

I was just suggesting *a* reason why there hasn't been more interest in the thread. I'm not sure garnering responses is about impressing people (though for some it might be), but rather will they find it interesting enough to respond?


However looking at it from a price-point perspective is EXACTLY what Pano and I are suggesting. In other words we don't think the design you have out-lined is going to net you better performance for the price then something like the little Manzanita. *Different* performance, yes. (..and who knows, performance you might find more meaningful.)

Surprisingly that little 3" driver is excellent (measurably) - probably quite a bit better than the Silver IRS - at least at lower spl's. Still, the Manzanita isn't a design that particularly captures my interest either.


As for what might be more interesting?

Perhaps an open baffle line array, or at least open baffle for the mid-bass drivers - crossing over to your N2012 drivers (also open baffle).

Maybe an MTM open baffle, or an MMTMM (or MMMTM)?

Just some ideas, and the Silver Iris isn't a bad idea it's just not a great one with either objective performance or even subjective performance over a broad group of listeners. (..lots of user's like it, but only a few seem to love it. I'm sure Pano has heard it several times from LSAF alone.)

BTW, this isn't meant to be a "downer" though it reads that way, just something to consider before moving forward.

Note: your proposed bass section does sound interesting to me - and a lot more so than an Alpha-based version.
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Last edited by ScottG; 16th July 2012 at 03:57 AM.
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Old 16th July 2012, 04:00 AM   #10
Pano is offline Pano  United States
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Sorry, I thought you were looking for other OB ideas, not analysis or refinement of your ideas. That was not clear to me from your first post (it should have been.) My mistake.

I've offered you ideas and comments in years past and you steadfastly refused to consider them. So I don't think I can offer much help this time, either. Have fun, looks like quite a project!
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