HT with Alpair 10.2 and CHR70.3 - diyAudio
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Old 19th December 2012, 10:57 AM   #1
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Default HT with Alpair 10.2 and CHR70.3

OK, here we go. The idea of building a new HT system with Markaudio drivers has been in my mind for well over a year now, and two weeks ago I finally pulled the trigger: three Alpair 10.2 and two CHR70.3 were ordered. The Alpairs arrived a couple of days later and are breaking in without a cabinet, the CHR will be here sometime next year. So, what do I plan to do with them?

The main speakers will be a tqwt. I like very slim enclosures just because they look nice (mhm, and frankly there was a little bit of pressure to keep them as unobtrusive as possible ), so none of the designs here really fit. So I simulated an enclosure on my own. They have a linelenght of 1500 mm, the inner width is only 150 mm and the driver sits right at the top of the enclosure. The result looks like this:
Click the image to open in full size.
Right now I am building test enclosures out of cheap particle board. In a few days we will see how they perform.

For the center I am thinking about a pretty straightforward bassreflex box, but the final design still has to be "approved".

For the rear speakers I am thinking about a top firing micro tower with a sphere over it to get an omnidirectional speaker, inspired by this:
Click the image to open in full size.
I will of course build test enclosures before doing these in nice (and expensive) wood to verify they work for me.

I will try to document everything here, but I have to warn you: I only have very little spare time and only basic tools at my disposal, so the progress will be very slow. I am aiming for half a year to finish all of this, but will not pressure myself with a deadline. If I think that something is not quite how I like it I will simply start over. So don't expect daily (or even weekly) updates. Oh, and this is the first time I am really starting from scratch and not building a proven design, so theres much to learn and many mistakes to make for me.

What do you think?
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Old 19th December 2012, 07:01 PM   #2
chrisb is offline chrisb  Canada
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A few thoughts -

A full 5.1 HT set-up is a rather ambitious place to start designing your own enclouses from scratch.

I've heard most current models of Alpairs in a fair range of enclosures, and would suggest that the Pensil and Brines' M10-A10 are the simplest proven designs that will deliver great bang for the buck for the L&R mains, and not require stands.

There is also a very extensive series of enclosures in the Planet10 paid plan set for the Alpair10.2, including a center dual vented channel that could be morphed within reason to fit a shallow mounting depth.

150mm internal width is in my estimation far too narrow for this driver - the designs that I've personally built or drawings I've seen for this model range from minimum of 170mm for the compact center channel to approx 204mm for the Pensil and M10-A10.


The top-firing design for the surrounds is intriguing.

If you've not worked with Alpair metal coned drivers previously, be aware that the cones are more delicate than any paper or poly that you may have used before.
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Old 19th December 2012, 08:54 PM   #3
TiMBoZ is offline TiMBoZ  Australia
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Quote:
If you've not worked with Alpair metal coned drivers previously, be aware that the cones are more delicate than any paper or poly that you may have used before.
Yes, I learned the hard way. I have an A10v2 with a little wrinkle on the edge of it, left from where I dropped it onto my thumbnail. Dang. I 'nano' panel beat most of the dint out. But there's a still a little wrinkle/scar. So be careful, the metal membranes are very delicate.

I like the look of those Duevel omni 'executive novelty' speakers. Sculptural. Your mains will need to be impressive, because something like these will outshine them in terms stage presence, or in room static appeal.

My motto is for speaking building is when it stops being fun, and starts feeling like work and all consuming. Stop for a while. Consequently my deadlines are annual or bi-annual 'I'll finish by late 2013'. Going slow helps to smooth out all the daily whims of inspiration, and percolates, distills down your ideas. Hope you enjoy what looks/sounds like a great DIY project. I'll be interested to hear your impressions of the omni sphere wave guide treatment. If you go that way. Good luck.
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Old 20th December 2012, 08:38 AM   #4
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Quote:
A full 5.1 HT set-up is a rather ambitious place to start designing your own enclouses from scratch.
Maybe. But I see it like this: I am just designing the mains from scratch for the first time. Once i get to the center and surrounds I already have experience. Gotta start somewhere.

Quote:
150mm internal width is in my estimation far too narrow for this driver
Mhm, coming from you with all your experience that makes me a bit nervous.

Quote:
I ... would suggest that the Pensil and Brines' M10-A10 are the simplest proven designs ...
But they both look a bit "chubby" to me. Thats the reason it took me so long to actually start my project. Those two enclosures were the main candidates because they are both proven to work very well. Only I couldn't picture them in my livingroom. So I started to think about doing my own thing. I'll see how that turns out. Maybe I will build a pair of pensils just to have something to compare mine to.

Quote:
If you've not worked with Alpair metal coned drivers previously, be aware that the cones are more delicate than any paper or poly that you may have used before.
I am a frequent reader of this forum although I seldomly post, so I heard about this. I will simply not touch the cone and make really sure nothing and noone does.

Quote:
My motto is for speaking building is when it stops being fun, and starts feeling like work and all consuming. Stop for a while.
Exactly how I am thinking.

I will most likely build the rears the way I described. I already have the spheres. They are made out of fairly thin stainless steel, so I think I might have to fill them with something to keep them from resonating, but with what? I thought about concrete. Well, thats quite some time off still till I get to building them. I'll cross that bridge when I come to it.


My progress so far: the wood for the test enclosures has been cut and glued together.

Click the image to open in full size.
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Old 20th December 2012, 05:47 PM   #5
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Quote:
Originally Posted by Hilmar_G View Post
the inner width is only 150 mm and the driver sits
Mark warns about getting the side walls to close to the driver. Our experiences back that up. You are going to have issues caused by such a narrow baffle.

Click the image to open in full size.

dave
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Old 20th December 2012, 06:08 PM   #6
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Made some progress again today, the test enclosures are up and running:

Click the image to open in full size.

I really like the proportions. What I am a bit disappointed in is how they sound. I am sure that some improvement can be achieved by playing around with the stuffing. But maybe you are right with the narrow baffle not being ideal.

What exactly happens when the driver gets close to the side wall? How does that affect the sound?
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Old 20th December 2012, 06:41 PM   #7
zman01 is online now zman01  Bangladesh
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Hilmar_G,

As far as I know if driver gets too close to the side walls you might have the internal refelctions come back to the cone and distorting the sound and/or boxy sounding speakers.

I am sure Dave and other members can add more.

Have you broken in the drivers or are they fresh?

Last edited by zman01; 20th December 2012 at 06:58 PM.
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Old 20th December 2012, 06:49 PM   #8
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The drivers have around 70 hours on them, but only sitting in the cardboard box they came in.

I have been listening to them now for some time and experimented with the placement and I am not quite as disappointed as I was before. Maybe I just have to get used to them as they sure do sound different than what I had before.
I will build a pair of pensils though just to have a comparison. But that is going to take a while, tomorrow I have to do some last minute shopping and then I'm off to my parents for the holidays.
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Old 20th December 2012, 06:51 PM   #9
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Quote:
Originally Posted by zman01 View Post
...internal refelctions come back to the cone...
quickly and with little or no decrease in level before they hit the back of the cone.

dave
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Old 20th December 2012, 08:56 PM   #10
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What width would you say is the absolute minimum this driver can work with? Chris mentioned something about 170mm....
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