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tresch 12th March 2009 05:32 AM

My first build! MarkAudio CHR-70 in da house
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I'm back!

After weeks of research, reading thread after thread on this site, familiarizing myself with WinISD, going through a few different iterations of design, accumulating tools, etc etc.. I've finally completed my first set of speakers, and I love them!

I felt like experimenting, so I went out on a limb and picked up a pair of CHR-70s for my first shot. Everyone seems to highly regard Mark's Alpair series, so I was really curious how a "cheap" speaker from the same designer would perform. Since I'm playing around with getting a lot of great sound out of as little money as possible, the $70 a pair price range seemed pretty sweet.

These first boxes are fairly large. they're not the "mathematically optimal" size for deepest flat bass extension, but they're not much of a compromise. For my first boxes I wanted to see how the speakers would sound in an optimal box designed so the speakers could stand alone. Next I'm going to play with a much smaller enclosure and see how small I can go before they really loose their oomph.

I'd like to experiment with some really small boxes, and then use one of the Adire Extremis 6.8s that I have laying around to do a small subwoofer, and make a matched 5.1 system.

I'm mainly comparing these speakers to my roommate's B&W 602s, which are fairly badass speakers and cost $600 a pair. With current testing so far, I will say that the CHR-70s aren't quite as clean, but they're really not that far off. I need to get both sets of speakers in the same room running off the same amp to get a real objective test, but so far I'm VERY happy with the sound these put out. Considering these speakers cost less than $100 for the pair, I'd say I'm doing pretty well :)

tresch 12th March 2009 05:37 AM

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What really impressed me was their low end performance. They're no subwoofers, but in these boxes they sound decent for most anything short of whacky electronic ultra sub-bass. In the pictures I'm listening to some Yo Yo Ma (can't you tell?) and the deepest cello notes come through nice and strong

rcdaniel 12th March 2009 05:51 AM

Congratulations on your first build. Thank you for sharing. Keep us in loop as they break in and you make any further changes.


tresch 12th March 2009 05:59 AM

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If you guys don't mind I'll just babble here a bit about the construction or whatnot, as I'm a noob and all the basics are still interesting to me, plus, anyone else looking to build a cheap speaker with these fellas might be interested.

The box ended up being about 12.4 Liters, tuned to 45hz, with a 1 1/2" diameter port at 4 1/4" long.

I actually just used a bit of pillow stuffing along the back of the speaker for damping. I may try adding some more to see what effect it has on the sound at a later time.

Attached is the WinISD plot of the box as built!

Random anecdote: I was originally going to build the boxes at the "optimal" size as determined by WinISD's "Chebyshev" alignment, for deepest and flattest bass response. This meant that the 4.24" ports that I ordered were plenty long and, in fact, I'd have to cut them shorter to make them work. I then decided that the boxes were simply TOO big and I wouldn't be able to put them anywhere, and even though I'm experimenting it'd be nice to have something halfway usable, so I shrunk them down exactly as much as I could without having to order or build a longer port, so in a way, the size of the box was determined by the length of the port that I happened to have sitting around :)

Henkjan 12th March 2009 03:40 PM

Re: My first build! MarkAudio CHR-70 in da house
nice! do you have any BSC?


Originally posted by tresch
What really impressed me was their low end performance....
and how is the sound overall? midrange? high? tonal balance?


Originally posted by tresch
I'd like to experiment with some really small boxes, and then use one of the Adire Extremis 6.8s that I have laying around to do a small subwoofer
try 2 liters sealed with a 680uF capacitor

loninappleton 12th March 2009 05:46 PM

This models pretty well in the BIB calculator as well (though I was puzzled by FO vs Fs.)

For a surround setup, you could have BIBs as fronts and the smaller satellites for center and rears.

I like the Mark Audio. Anxious to hear more about it.

speakrsrfun 12th March 2009 07:48 PM

I think anyone who purchases these drivers with the knowledge that you are not going to get EJ sound out of a $70USD/PR driver you'll be pleasantly surprised at how well these little guys perform. I currently have a F.A.S.T. project going that contains two CHR-70's wired in series per side crossed at 200Hz to 4 Silverflute 5.5" midbasses in a separate cabinet wired in series / parallel and I'm telling you these little guys shine in OB or in a boxed design. I purchased these as a experimental replacement for an FF85K in OB because to be honest even though it does the top end superb, the mids so sweet the lower mids, well this little driver just couldn't do it for me and sounded like it was screaming for a box. So I decided to try out the CHR-70's and with two a side allowing better power handling the CHR-70's really do everything just as good as the FF85K up until 18k then that's where the FF85K excels (not that I can hear much higher than that), but the CHR-70 kills and I do mean demolishes the FF85K in the lower midbass registers. I can get good in room response to 50Hz with the two in a 12Ltr ported box tuned to 60Hz. Iíd say if your looking for really high output standalone these wonít fit the bill, unless you crossed above 200hz then your looking at 110-115db peaks in room with these little buggers in pairs.

All in all Iím happy, and itís nice to see someone else likes them as much as I do, Peace and happy listening.


tresch 12th March 2009 09:42 PM


nice! do you have any BSC?
Thanks! And no, no passive filters yet. My audio source is a computer, though, so I can use Winamp's built in EQ to shape the sound, and I've been experimenting with with that to tame the high end a little. It doesn't take much. In a lot of music I actually almost hate toning it down, just because the high end actually sounds quite pleasant!

That said, I've not actually objectively looked at the baffle step problem, I'll definitely have to do that today


and how is the sound overall? midrange? high? tonal balance?
Overall fantastic, I'd say. Forgive me as I am not exactly the worlds most seasoned listener, but I do think I have a taste for decent sound. My high-end listening experience is largely based around Grado SR-80s and the B&W 602s that I mentioned above. In that context, I really love listening to these speakers and I find myself digging for music just as an excuse to listen to them.

The midrange is just lovely, and the highs are suprisingly unoffensive. There are definitely a few frequencies that the speaker plays really strongly relative to others, but it doesn't sound distorted, just... louder at some high-mid frequencies. This could, of course, be due to the whole Baffle Step thing, so I'm going to have to look into that

tresch 12th March 2009 09:44 PM

My current dillema is that now I'm just thinking how these could make an awesome but inexpensive 5.1 system.. but they're 4ohm, and none of the less expensive surround receivers that I can find will deal well with 4ohm loads! I've been wanting to build my own amps, but then there aren't really many options for inexpensive standalone surround decoders. What is a guy to do?

There's that creative DDTS-100 (scratch that, seems to be no longer available), I could get a cheap receiver that had RCA pre-outs (also rare, it seems, unless someone can recommend one?) or I could just wire resistors in with the speakers to bring their impedance up to 6 or 8 ohms. Opinions?

human.bin 13th March 2009 12:12 AM

in the vendoor`s bazaar there was a guy selling out tripath based 7.1 or 5.1 amplifiers, i don`t remember anything else, but maybe it`s worth a look, e also had some kind of ebay shop...

@speakersfun: anypic of you project?

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