My simple CHR-70a Desktop Speakers

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Just a quick picture of my new desktop speakers. I just installed the drivers this evening and gave them a first listen. Even with only a few hours of break in, I can tell I will really enjoy these. I'll probably keep them at home over the weekend, and get a little time under their belt, before I take them to work.

The boxes are just a smidge larger than the suggested box, and tuned just a bit deeper/flatter. I'm not super happy with the finish on my boxes. I originally intended to do stain/poly on the 3/4" ply The stain was blotchy, so I hit them with green Hammerite. The paint looks great with the alimunum cones, but I should have spent a little more time filling/sanding.

All of my source material at work is either streaming, or from an iPod. I thought hard about getting the paper cone, but that aluminum just looks so dang cool. I might need to build a little SE EL84 amp to go with them.

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Nice build Chad. Before you get the tube amp, you can try out the inexpensive TPA3116D boards - folks seem to be pretty happy with them.

http://www.diyaudio.com/forums/markaudio/244540-alpair-10-2-amplifier-suitability-3.html

There's a separate discussion on the Class D section too.

I've never had a big interest in peicing togther a T/D amp from a board. It just seems like there's a lot of reasonably priced finished amps out there. Right now I'm using an older Dayton DT-1, which sounds fine for my purpose - it's just junky looking.

I'm probably over ambitious talking about building a tube amp for work. I already have a couple DH-SET amps at home that need maintainance, and I haven't had a chance to get them back on-line. Tubes at work would certainly be cool though.

Those look nice! What is the round-over size you used?

I used a 1/2" roundover. Actually, I posted a slightly fuzzy picture on purpose. My roundovers + sanding on the end grain of the plywood turned out less than perfect. If I had planned on painting them from the start, I would have built these with MDF, so I could get a better surface before painting.

The new speakers are at home, getting the FM radio break in - probably not much better than white noise. At least my dogs have something to listen to today.:)
 
MDF can provide a very nice surface for painting on unbroken faces, but once you machine the edges with radius, chamfers or any other profile ( ogee, etc) , it can easily take as much prep with numerous coats of fill, heavy solid primer, and lots of sanding to achieve paint readiness (particularly with glossier finishes) as does plywood.
 
MDF can provide a very nice surface for painting on unbroken faces, but once you machine the edges with radius, chamfers or any other profile ( ogee, etc) , it can easily take as much prep with numerous coats of fill, heavy solid primer, and lots of sanding to achieve paint readiness (particularly with glossier finishes) as does plywood.

Being that these will be 18-inches in front of me for 40 hours/week, I'll probably wish I made the effort. Every time I look away from my monitor, I'll see every imperfection. Of course my desk is such a mess, they'll probably be covered with mounds of paper in a week.:p

One of the days, I want to do an automotive urethane color & clear coat on a speaker. I've done a little DIY bodywork and painting, so I know it is a lot of effort to get the surface perfect prior to painting. I just haven't had the gumption yet to try it on a speaker.
 
Just a quick update - I've had these at work all week, I'm probably only about 50-hours into break-in, but the speakers are starting to smooth out nicely and sound really good. The slot port seems to couple well with the top of my desk, and with just a little bass boost, the bass is very tonal and surpisingly punchy at low volume (4/10 on the knob - how many dB, I don't know).

When I first hooked them up, I had to toe them out to tame the treble, as Mark suggests. After just a few days, I have them square and the balance is nice.

I had a number of co-worker that thought I bought them, and several asked what they were made of - so I was probably was overly self conscience about the finish.

I doubt I could have found a more suitable driver - and know I'll get many years of enjoyment from these.
 
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Just a quick update - I've had these at work all week, I'm probably only about 50-hours into break-in, but the speakers are starting to smooth out nicely and sound really good. The slot port seems to couple well with the top of my desk, and with just a little bass boost, the bass is very tonal and surpisingly punchy at low volume (4/10 on the knob - how many dB, I don't know).

When I first hooked them up, I had to toe them out to tame the treble, as Mark suggests. After just a few days, I have them square and the balance is nice.

I had a number of co-worker that thought I bought them, and several asked what they were made of - so I was probably was overly self conscience about the finish.

I doubt I could have found a more suitable driver - and know I'll get many years of enjoyment from these.

Hello Chad,
Many thanks for using Markaudio drivers and for your feedback.

You've well illustrated my design efforts over recent years to extend usable output from a single cone full-ranger. On-off axis adjustment to control the high range is an easy set-up on Markaudio CHR and Alpair drivers; And these drivers deploy "long throw" power-trains offering bass load extension.

Enjoy your system.

Cheers
Mark
 
Hello Chad,
Many thanks for using Markaudio drivers and for your feedback.

You've well illustrated my design efforts over recent years to extend usable output from a single cone full-ranger. On-off axis adjustment to control the high range is an easy set-up on Markaudio CHR and Alpair drivers; And these drivers deploy "long throw" power-trains offering bass load extension.

Enjoy your system.

Cheers
Mark

Cool. You know, having the owner/designer taking an interest in the end result of even a little project like mine makes me like these even more. :)
 
MDF can provide a very nice surface for painting on unbroken faces, but once you machine the edges with radius, chamfers or any other profile ( ogee, etc) , it can easily take as much prep with numerous coats of fill, heavy solid primer, and lots of sanding to achieve paint readiness (particularly with glossier finishes) as does plywood.

A lot of people (in non-speaker applications) swear by moisture resistant MDF which is a green colour. It gives a much better machined edge than the fluffy brown stuff. A quick sand of the machined edges and a couple of coats of thinned pva to seal. I final quick sand and it's ready for primer.

I've used it myself and have been able to get a very high quality finish which would be appropriate for something subject to close scrutiny (eg desktop speakers).

Dave
 
On this side of the pond, Sierra Pine Medex is a popular trade brand - note that even though "moisture resistant" their finishing instructions advise slight radius (3/16"), to all exposed edges and avoidance of any latex (water) based sealers, primers or top coats, as well as the use of automotive type paints unless fully sealed and primed first.

but then, I don't paint many of my speakers, and avoid MDF for speakers not for issues of weight or ease of finishing
 
Thanks for the replies. I don't think I've ever seen anything other than the plain 'ol MDF they sell at Lowe's/Home Depot - But then again I've never really looked for anything different.

Now that I've been bitten by the FR bug, It probably won't be long before I want to tackle a big/fancy horn. I've seen horn designs on the 'net using stacked construction that are pretty darn cool.

I have a freind with a CNC router who cut the peices I used to build a stacked construction subwoofer box for my car. I think with his help and a little more patience, stacked construction of a horn would be do-able. Of course, getting my horn modeling mojo up to par is a big leap, so I'm probably just dreaming right now.

Here's the result of about 16 hours of cad modeling, and 8-hours of construction. If I stepped up the finish work, I think I could do a really nice speaker. Sorry, I'm rambling and getting a little off topic, but it's a quarter to 5 before a holiday. ;)

An externally hosted image should be here but it was not working when we last tested it.
 
Love them. What are the dimensions of the boxes?

The outside dimentions are 7" wide, 10.75" deep, 11.75" tall - using 3/4" plywood.

They're just a tad larger, and tuned a tiny bit deeper than the Markaudio plan on Madisound. My quick-n-dirty model in WinISD showed the Markaudio tuning had a a few db bump at the bottom of the bass. Being anal, I tuned mine flatter. In hindsight, I probably should have used the suggested tuning, since it provides some of the low bass boost that I ended up adding with the bass tone control.

http://madisound.com/pdf/markaudio-enclosure-plans/CHR70-BR.pdf
 
Well, time to dig up an old thread. My trusty TEAC PowerMax 1300 died today after 15 years of exploatation on 5 different PC over their lifetime. I could buy something small to fit in but I thought it's time to test the CHR-70. So, my question is: can a pair of MA CHR have enough bass output to equal or best the minisystem I had? It was rated at 70W rms, but of course have nowhere near that as they say the woofer has 35W but in reality upon opening them there was a 30W woofer inside. Still, they were good enough and I kind of used to their midrangeless sound :). But time to move on and try the CHR.

I cannot make a huge enclosure because desktop space is small, so I am limited to the 15cm width and 18cm depth. And also would like to stay at 45cm height maximum. In that space there seems to be ~8-9 liters. So, would the CHR be able to equal my ex 5" subwoofer on their own, or I have to help them? I would use them 90% at nearfield and ocasionally a little loud music so there would be the need to have some punchy bass. Not deafening, as it is a small box but... It would be nice to have a round, full sound.

If help is needed, there are 2 options I could think of.

One would be to put another miniwoofer in the same enclosure. I have heard that HiVi B4N can make a lot of bass in small spaces and because it has the same colour it would be estetically pleasing to put it under a CHR Champagne. WAF stuff... Use CHR in a sealed 3l and let the B4N in the remaining 5l vented to take care of the bass. I would biamp them with a 2x50w tripath amp, and let the CHR fullrange and the B4N lowpassed with this at probably 300Hz or about.

Option 2 would be to reuse my sub enclosure and fit there a Tang Band minimonster W5-1138smf lowpassed and let the CHR vented in 8l fullrange

What would be the better option? Or another one if you can help. Many thanks
 
My first feeling is to go with option 1. This will give you a little more power handling, though I would consider going with an active 2 way crossover. The main reason being the CHR70 is a bit gutless in the midbass in an approximately 8l BR, IMO. However, option 2 should work too. It's really impossible to tell what will be better without building both, unfortunately.

My CHR70 are currently residing in mini Karlsonators, and those do everything you ask for - no extra drivers required, but the depth exceeds your requirements. Width is 15cm but depth is about 24cm IIRC. For nearfield use, probably direct radiating is better anyway.
 
Yeah, I read today here about Karlsresonators but they would be too close to me and get in front of the monitor which is not wanted. So I have to go with something more classic. Initially I thought maybe the CHR would suffice, and I am sure they will for the 90% when used for light gaming and music listening from the chair. But there are those moments when you want to get loud and I am afraid CHR can't handle that very well. So a woofer helper might let CHR breath in mid bass and upwards, and the Hivi might take care of the bass. I am fully aware they won't make rock concert loud, but in my 4x5m room I want to hear the bass, not really feel it :)

I just don't know if the space is enough for hivi to get their job done. That's why I am asking the experts here, I'm just trying to learn something, else I could have taken the easy way out and buy another PC speaker set and be done with it, but I want to diy and am sure the sonic results will be much better than any pc speaker if planning and execution goes well
 
5l should be fine for the HiVi, since their Vas is 4.5l. I suggest tuning them to Fs. It's not max flat and you'll get a slight (2db) rise in the midbass, but that is OK. (commercial PC speakers often have a grotesque rise in the midbass)

You can always lower the tuning slightly and/or add some light filling if they are boomy.

Efficiency of the B4N is lower than the CHR70, not even considering baffle loss. Since you would be biamping this doesn't really matter.
 
Yes, my thoughts exactly. Biamping takes care of sensitivity and because I would use a low pass active filter, the boominess might be taken care somewhat. I could also use a active filter for CHR but thought that the sealed box might act as a high-pass filter at 2-300Hz depending on volume used.

As an alternative I could even use a MIVOC WAL 416, which has somewhat similar Vas, 11mm Xmas p-p and 60W RMS. But doesn't look so pretty :))
 
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