[Anthony]

I posted something like this over at diyaudio, but I figured I'd cross it here for your all's perspective.

I have a Magnepan 4.1 HT now.  10.1's in the front and MCMC1's in the rear.  Sealed sub.  Mains and rears go down to about 80 Hz.  I love the airy dipole sound, but the Maggies are power hungry and lack a bit of midrange punch for movies.  Plus I have the problem that they collapse to the nearest speaker when you aren't in the sweet spot (but that sweet spot is magical).  So at worst, I need a center channel.

The Maggie center is $1k, so for that price, I figure I can build a full HT of dipoles and possibly get some of the mid-punch back.

First thought was the Adire Extremis, but those are not available anymore.
Second thought was one of the GR-Research models (M-130, M-165X)
A friend of mine had a couple of others in mind that I can't remember now, but they are similar in size.

For the tweeter, I'm torn between the Neo3 and Neo8 -- run without back cups for the full dipole effect.

For the LR design, I'm debating an MTM with the Neo3 or an offset MTM with the Neo8.

Since the baffles are easy to prototype, I'll probably play around with a bunch of different widths and measure the output in-room (sorry no anechoic chamber for me).  Once I decide on a tweeter, then it's off to the center channel, which will have several design choices.

I'm pretty much stuck with a horizonal alignment, but will keep the tweeter vertical.  Then I'll play with three baffle designs: straight, curved in, curved out.  I know Martin Logan and Magnepan curve their center channels, so there must be something to it (although ML curve in and Maggies curve out).

So, lots of trial and error until we get it right.  Figure I'll start out with a handful of drivers (and a buddy of mine has some extras to play with from other projects) and build one speaker to measure.

So, sorry for the long post.  Any thought on this or recommendations of drivers to try?  I'm going to try to model as much as possible before buying anything, so I have some time.  I imagine this project will go all summer.

Thanks for any and all help!
AC

[dewar]

Hi Anthony.

I cant be much help, but want to put in a word of encouragement, and request to keep us updated.

I've got a 4.3 setup with B200 in the front and fostex in the rear. Will go all B200 soon, and have been thinking about a centre, most likely a single B200(with phase plug of course). But will set it back against the wall and use for movies only - music staying 4 channel.

I'd be interested to know what size rectangular horizontal baffle would be needed to reach down to 80hz. Might have to have it floor standing as suspending it bellow a screen might cost too much bass.

That said, I think the Hawthorn SI might be a very good choice and easy to implement, from what I've read (havent heard them).

Also, I wonder if a MTM might be unnecessarily complicated and a MT or just M might suffice? Let us know what you find.

cheers

Bevan

[Bob in St. Louis]

Hey Anthony, ditto what Bevan said about the Hawthornes. Five of the Silver Iris Coaxials and a couple of the Augies to take it a bit lower and BLAMO, instant wonderfulness.  aa
And...your right at the price you wanted to be.
Ultimately, this is my goal..

Here's the 15's, but more drivers/sizes are in development/testing.
http://hawthorneaudio.com/drivers.htm

Bob

[Anthony]

Thanks for the encouragement.

My only concern with the Hawthornes is the dispersion pattern.  The MTM, or D'appolito alignment beams the vertical, while allowing the horizontal to remain wide.  In the Coax configuration, I would imagine the pattern would be more circular in 3D space.

For some rooms, I can see that being fine, but I have a hard ceiling (1/2" drywall) and a really hard floor (linoleum on concrete with a big area rug/pad).  So floor and ceiling reflections are a big issue.  The coax alignment would probably be okay for a shag or floating floor with an acoustic drop ceiling.

One of the ideas my friend had (BoomMCT -- I think he's around here, I know he's over at the Shack and diyaudio), was to do the MTM down to 200 Hz or so and bulid a transmission line cabinet with some bass drivers to fill in the low end.  Again, this is probably going to be more of a research project than anything else, so we'll see where it takes me.

thanks again,
ac

[Bob in St. Louis]

Hey Anthony, I've chatted with Boom on the Shack about OB, relatively recently. I had started an OB thread over there a while back. Looked like a cool place since there wasn't much OBing going on there.
He joined in the chat and build himself some cool looking 8" OB's.

No problems with dispersion pattern for a Hawthorne coaxial center channel, just a single 15" or (soon to come) 10" center. No MTM necessary. That'd be silly huge besides!
I'm not sure if they're still for sale or not, but a fellow on the Hawthorne forum was selling just the SI's midwoofer. No XO and no tweet. That'd be a good start for a MTM center, maybe add a verticle planar and EQ/XO to taste. That way it would keep the size down to something resonable. I think that would be fun to play with.

I don't see too much problems with your treatments, the rug will help a lot. Maybe lay a layer below your existing rug?? Another cheap rug, or a piece of carpet pad if needed.

Do you have pics of the room?

Bob

[Anthony]

Okay, the OB-HT experiment is underway.

With the help of BoomieMCT (who is great at designing crossovers, BTW), we came up with a plan to test:

BG Neo3 PDR tweeter with 2, 8" Part Express Reference Series drivers in an MTM vertical or M-T-M horizontal (for center).
http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=264-735
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-366


Crossover will be a 4th order at 1800 Hz.  We are also copying Dan Wiggins' notch filter on the Neo3 to roll off the rising frequency response.  One thing we noticed on the Adire DDR white paper was that Dan specified a 20 Ohm resistor in the schematic, but that would kill all the high freq's pretty bad.   What models better is a 2.0 Ohm resistor, so we think it's a typo.  Not that anyone can build these anymore, but FYI . . .

Right now I bought the stuff from PE to build one test unit, which we will try in several baffle arrangements (12", 10", 15", odd shapes, U baffle, H baffle, curves).  Between the two of us, we have 7 routers and a lot of spare MDF

Plan is to use Room EQ Wizard to do listening position sweeps using a M-Audio MobilePRE and Behrninger ECM8000 mic.  I'll baseline against the Magnepans for listening location and try to keep everything fixed.  Once I come up with a design (baffle and crossover) I like, we'll order the parts to build a full run.

If the experiment fails miserably, I'll buy another Neo3 and make some bookshelf speakers

I still have a bathroom floor to grout and a wedding next weekend, but hopefully construction should begin after Memorial Day.

[ssabin]

Anthony,

You could try two GR M130-16 drivers along with your NEO3 to complete your MTM.  It would be interesting to see how this setup compares to the RS drivers.

The GR kit speaker uses this proposed MTM on top of a bass bin which also uses two M130-16 drivers.  Of course, that bass bin could be easily changed.
http://www.gr-research.com/kits/ob-5.shtm

Are you planning on a passive crossover network?

[Anthony]

Yes, a passive crossover network.

I get a dealer discount from PE (I buy lots of connectors and wire from them for my installer business), so the prices were too good to pass up, especially if I end up buying a whole HT's worth of drivers from them   Plus if this works, I'll probably offer some custom speakers or built-in options for customers -- not planning on going that way, but it never hurts to diversify.

I've also read good things about their reference series on a bunch of forums.  So for about $100 I'll have a pretty good testbed to play around with.

I like the OB5 design and I may end up going that route.  For now, though I want to play around and see if I can come up with a center channel design that works well.

[BoomieMCT]

Hey Anthony, I've chatted with Boom on the Shack about OB, relatively recently. I had started an OB thread over there a while back. Looked like a cool place since there wasn't much OBing going on there.
He joined in the chat and build himself some cool looking 8" OB's.

Thanks Bob.  I know Anthony from way back - he actually got me into building speakers and then I kinda went nuts with it.  I would lend him my 6.5" OBs but they don't reach down to 80 Hz well without some augmentation.  I have some cheap Audax drivers on order that I'm going to swap out the Pyle drivers with and see how they do.  At the very least they won't have a stupid sticker on the front. 

[Bob in St. Louis]

Ahh, that sticker didn't look that bad. It gives the driver some visual character! 
Spl a bit low, but the Qts on the Audax looks good, you might be on to something there. You definitely can't beat the price!
(Mr. subliminal is thinking of an "Array" of those aa)

You still liken OB Boom?

Bob

[BoomieMCT]

You still liken OB Boom?

In general I do but the bass issues don't work well for me.  I don't have space for big drivers and bigger baffles!  Also, I'm way more of a bass-head then Anthony.  We'll see what I can squeeze out of my Audax tests. . .

I'm very interested in Anthony's ideas for mains - OB tweet and mids with some sort of enclosed drivers for the low end (similar to an OB7 with no subs).  Right now this seems ideal to me.  I'm jealous as I've wanted to make something similar but don't have room for it anywhere but my office.

[Bob in St. Louis]

Yea, I'm a big bass head too. Hence my array of 15" Augies. OB bass is an amazing sound dude, you've gotta hear it, you'd be impressed. But space is consuming for sure. IB's a possiblity but brings it's own set of logistical problems too.....

Bob

[Anthony]

Well the order is here.

The Dayton Reference drivers are incredibly well built.  I like the look of the phase plug as well -- no grills for these things.

The BG tweeter looks nice, especially with the flush mount face.

If all goes well this weekend, I should build the test crossover and a simple baffle to start some tests.

I'm also going to try a W baffle sub design using the drivers, just to see how they perform (plenty of spare MDF around).

Anthony

[ccappe]

Hi Anthony, did you get forward with your project? May you post your result? Did you try to use the neo 3 as a coaxial bi pole? thanks for your kind reply

[Anthony]

I have the baffle made and cut out some blanks for the crossover stages.

I'm hoping to wire it up tonight and play around with it tomorrow (I have two crossover designs to try).  Right now the baffle is an MTM setup, as tight as I could get it.  I'll also try some other baffle shapes made out of drywall or cardboard to find an optimum.

Pics and results are forthcoming!

[ccappe]

Thanks and...please do, I'm very anxious to see the pic and read your comment on how it sound!      Have a good time

[markC]

Yes, I'd like to know as well. I'm currently running mt visatons and would like to try mtm for a little extra power handling. They go plenty loud for my listening sessions as is, but every once in a while I like to show off.
I've got the x-overs built on the puter, just a little hesitant to shell out for the parts in case ob and d'appalitto don't get along.

[Vapor Audio]

Just wondering, why would you choose the RS225's for running up to 1800hz?  They're going to sound very harsh crossed that high ... I've built an MT with them crossed at 1350hz 8th order, and they STILL sound harsh.  They work well up to about 500-600hz in a 3 way though.

[markC]

8th order? Sounds like a pretty extravagant x-over. Have you checked out the phase plots? Not that I know what they would look like-just curious.

[mcgsxr]

MarkC, you could borrow my b200's, if you want to try that MTM out...

I won't even bother to offer to come visit, since I have failed to live up to that SO many times!