HT with Alpair 10.2 and CHR70.3

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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 :rolleyes:), 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:
An externally hosted image should be here but it was not working when we last tested it.

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:
An externally hosted image should be here but it was not working when we last tested it.

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?
 
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.
 
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.
 
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. :sly:

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.

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.

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.

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.

An externally hosted image should be here but it was not working when we last tested it.
 
frugal-phile™
Joined 2001
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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.

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dave
 

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Made some progress again today, the test enclosures are up and running:

An externally hosted image should be here but it was not working when we last tested it.


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?
 
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?
 
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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.
 
What width would you say is the absolute minimum this driver can work with? Chris mentioned something about 170mm....


That's the "height" figure on the small center channel enclosure in the Planet10 plan-set for Alpair10.2. For mains, I'd certainly look at going even wider - such as the approx 204mm quoted earlier as seen in both Scott's Pensil and Brines' MLTL.

From my experience, these two designers often target their designs to different goals/compromises - for example the above named enclosures have quite different CSA & aspect ratios, but the fact that they are within a cm or so from the same width is probably worth noting.
 
I just had a discussion along the lines of "baby, I have to make them wider, they don't sound so good like this" ... insert heated argument here for a couple minutes, then... "ok, but then you have to make them less deep" . Seems like I can go ahead if I keep total volume about the same :D.
I think I will go for 180 mm and see how that works. The simulation for this does not look that different from the first I did. Well, new test enclosures will be built beginning next year. Thats what they are meant for, learn and verify.

Merry Christmas to you all,

Hilmar
 
I just had a discussion along the lines of "baby, I have to make them wider, they don't sound so good like this" ... insert heated argument here for a couple minutes, then... "ok, but then you have to make them less deep" . Seems like I can go ahead if I keep total volume about the same :D.
I think I will go for 180 mm and see how that works. The simulation for this does not look that different from the first I did. Well, new test enclosures will be built beginning next year. Thats what they are meant for, learn and verify.

Merry Christmas to you all,

Hilmar


Depending on the enclosure architecture, adjustments to aspect ratio* of CSA are generally not a problem (at least as far as modeling would suggest), but line lengths, driver placement, and vent/ports for MLTLs. BIBs etc should be retained.

*Some of us have our own thoughts on shapes and ratios of "standard rectangular" boxes or "pipes" - as well as types of materials and bracing schemes;) - you indicated earlier this is planned to be a learning experience, so no doubt you'll be able to test some of those for yourself - after the first couple of dozen pairs of enclosures, you'll be able to focus in on what works for you.
 
...after the first couple of dozen pairs of enclosures, you'll be able to focus in on what works for you.

I hope it does not take me quite as many tries to arrive at a funktional solution :rolleyes:
I will propably never achieve the same level of experience you have, but thats one of the things this forum is for, isn't it: so people like me can benefit from the knowledge of experienced veterans like you (even if we do not always heed your advice ;) )
 
I am still trying to save my concept with the 150 mm baffle width. If the early reflections of higher frequencies is the problem then maybe this can be solved with proper lining? In the frugal-phile box library I found a ML-TL by Jim Griffin that also uses an internal baffle width of 150 mm. Has anyone ever built one of those? There is only a stuffing density specified, nothing about where to put it and if the walls should be lined with something.

Even if lining the walls does not make it possible to stay with 150 mm it should reduce the needed width, correct? What should I use? My first thought was carpet, then I searched around and found Bonded Logic Natural Fiber Acoustic Pads recommended. I would not feel comfortable using fiberglass since its a ported enclosure. What do you think?
 
I am still trying to save my concept with the 150 mm baffle width. If the early reflections of higher frequencies is the problem then maybe this can be solved with proper lining? In the frugal-phile box library I found a ML-TL by Jim Griffin that also uses an internal baffle width of 150 mm. Has anyone ever built one of those? There is only a stuffing density specified, nothing about where to put it and if the walls should be lined with something.

Even if lining the walls does not make it possible to stay with 150 mm it should reduce the needed width, correct? What should I use? My first thought was carpet, then I searched around and found Bonded Logic Natural Fiber Acoustic Pads recommended. I would not feel comfortable using fiberglass since its a ported enclosure. What do you think?

a few thoughts:

I'm not sure about the enclosure of Jim's - with the hundreds of designs by various folks, it's hard to keep track of how many of which may have been built. Go ahead with the narrow width and see what you think.

If the Bonded Logic is the same as Ultra-touch recycled felted denim cotton fiber that we've been using for a couple of years, it's excellent to work with - although some enclosures still benefit from additional fill

If you're worried about loose fibers from the FB, then a simple trap of cheese-cloth or pantyhose at the internal aperture of vent should deal with that.

I would definitely not go any narrower than 150mm - I think that would place the side walls too close that wall lining wouldn't adequately control the LF energy, a good degree of which would be reflected back into the cone. This is not necessarily a huge issue with 1/8" thick car subwoofers, but with delicate cone full range drivers can mess things up substantially - which I've also found to be a problem with very shallow enclosures.
 
I had to find out that I can't get Ultratouch here in Germany. What I can get is "Nadelfilz", which apparently translates to "needle felting" and looks like this:
nf10.jpg

This is available in 10 and 20 mm thickness.

Also there is something called "Damping 10", which is recycled something (most likely cotton like ultratouch, but they don't specify what exactly). It has an adhesive on one side already but is only available in 10 mm and looks like this:
damping30.jpg


Does anyone know this stuff? What should I use?

With the 150 mm internal baffle I could only use 10 mm lining, there just would not be enough room for more. When I go 180 mm or more I can easily fit the 20 mm stuff.

Oh, and how would I fix the needle felting to the enclosure? For the test enclosure I would just nail it to the wall. Is that the way to go for the final enclosure too or is there a more elegant solution? Would glue be ok, or would it just hold the first layer and the rest rips off and falls down? I guess I will find out once I have it in my hands, but if anyone has prior experience...
 
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I had to find out that I can't get Ultratouch here in Germany. What I can get is "Nadelfilz", which apparently translates to "needle felting" and looks like this:
nf10.jpg

This is available in 10 and 20 mm thickness.

Also there is something called "Damping 10", which is recycled something (most likely cotton like ultratouch, but they don't specify what exactly). It has an adhesive on one side already but is only available in 10 mm and looks like this:
damping30.jpg


Does anyone know this stuff? What should I use?

With the 150 mm internal baffle I could only use 10 mm lining, there just would not be enough room for more. When I go 180 mm or more I can easily fit the 20 mm stuff.

Oh, and how would I fix the needle felting to the enclosure? For the test enclosure I would just nail it to the wall. Is that the way to go for the final enclosure too or is there a more elegant solution? Would glue be ok, or would it just hold the first layer and the rest rips off and falls down? I guess I will find out once I have it in my hands, but if anyone has prior experience...



The product with self adhesive backing looks interesting (provided it doesn't get stuck too early)

The UltraTouch (Bonded Logic) product we have available here is nominally 1/2" (12.7mm) and comes with a fabric backer. It's dense enough that with careful cutting you can get a pretty good friction fit, but for security's sake I find a quick tacking white PVA glue for melamine ( Rooglue.com) works great.
 
To help me decide what thickness I need I did a quick calculation. Maximum sound absorption in a damping material occurs where the air velocity of a soundwave is highest. That is at 1/4, 3/4, 5/4, .... wavelength, since the velocity on the wall is 0. Now you can calculate what frequencies will have 1/4 of their wavelength inside the damping material or the other way around, how thick your damping material has to be if you want to optimally dampen a certain frequency (and all higher frequencies).

When I want everything above 1000 Hz optimally dampened I would need a damping material that is at least 86 mm thick.
With the 20 mm material optimal damping would start at 4300 Hz, with 10 mm at 8600 Hz and with 1/2" at 6750 Hz.

Mhm :scratch1:

I guess I will go for the 20 mm ...
 
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