Mark Audio CHR-70 Application Thread

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Here is the final version.
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MA chr-70 Semi F.A.S.T question

Hey guys, I'm not sure if I should post this here or start a new thread.

I have a pair of Chr-70 gen3's that I have had in a 9L BR. I am thinking of combining them with a small woofer in what may be termed a FAST system. My goals for doing this are to maintain or improve upon the extension that i get from the chr-70 while adding a bit more weight or impact from the larger sd of the new driver. I also want to relieve the chr from producing bass to see what comes of that. I would like to try the chr in sealed or an open back tunnel on the enclosure.

I envision the total enclosure increasing to ≤15L with about 10L for woofer and 5L for chr. After much searching and consideration, the drivers I have in mind are The Madisound Speaker Store and Visaton W130S-8 5" Woofer with Treated Paper Cone 8 Ohm 292-564

They each show decent extension and roll off characteristics in 10-11L in WinIsd. (I am trying to get acquainted with all the FRD Consortium stuff, but there is a learning curve:rolleyes:) The price is about where I want to be for this experiment and the numbers look right. If I'm correct the increased sensitivity should provide a built in 2.5db baffle step?

I plan on crossing them around 200hz first order. Large coil on woofer and large cap on CHR. Not sure if I should cross higher, say 500hz for that built-in baffle step to work. I don't want to run a separate amp for each speaker, I want to keep it more like a typical 2-way.

Am I on the right track for meeting my not to lofty goals? Way off? Out of my mind?
Any help would be appreciated.

Thanks,
Evan
 
CHR-70 gen3 Boombox

Hi

I just wanted to show you my experimental project of using a pair of MarkAudio CHR-70's in a Boombox. This was my 3rd Boombox I have built.

Both elements are in 6,5 litres BR. I calculated vents with the winISD. The Box has a 5 Ah Lithium battery, but also possibility to use 230 VAC.

I think it sounds very good and the little T-amp ensures (2x12W), that the xmax of CHR's will not be exceeded.

(The heart blinks by the music.. ;))
 

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Hi All. I just finished these CHR-KEN's with the Enabled Planet_10 Hi-Fi CHR-70.2's ;). I've been breaking them in and they've been playing at low levels for around thirty hours. This project was my second speaker build and my first with the Mark Audio drivers. They sound great with my Helder Hi-Fi TA2020 amp! Guitars and vocals are excellent and I was pleasantly surprised with the quantity of clean bass these boxes produce. I haven't had a chance to mitre the corners so the ports are currently 198mm long in lieu of 191mm. I hope that doesn't adversely affect the box tuning. I routed out the ports into the 18mm marine ply outer side panels & also made the boxes slightly narrower and slight deeper than the Planet_10 design but maintained the nominated cross sectional area and height. I also installed a 12x18mm wide strip of plywood to the back of the outer side panels to allow for the wool felt lining attached to the rear plywood panel (see last photo). This helps to keep the slot before the ports clear. I hopefully will get around to installing the internal bracing but I'm soooo enjoying listening to the speakers I'm afraid I may never do it! :D

A BIG THANK YOU to Dave and Chris (Planet_10 Hi-Fi) for your efforts and for supplying the design (and anyone else who helped)!

Regards, Richard.
 

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Richard,

Took you awhile :D

Longer vents will tune a bit lower.

dave

Hi Dave.

It took a long time for me to decide which box to build the CHR-70's into with the many designs available and then even longer to start building. I'll chamfer the corners soon to get the correct port length. Would there be any benefit in slightly angling the internal bracing panel to help reduce the standing waves between the parallel vertical surfaces?

Thanks, Richard.
 
Richard,

Took you awhile :D

Longer vents will tune a bit lower.

dave

Hi Dave.

It took a long time for me to decide which box to build the CHR-70's into with the many designs available and then even longer to start building. I'll chamfer the corners soon to get the correct port length. Would there be any benefit in slightly angling the internal bracing panel to help reduce the standing waves between the parallel vertical surfaces?

Thanks, Richard.
 
Hi guys,

I plan on building PC Speakers as my first DIY project. I came across the CHR70 as they seem to offer very good value for money. Being a fairly tall person I need the driver to be roughly 45-50cm higher than my table but the speakers should be much higher than 60-65cm. An online simulation told me that the speaker would work "best" in a 15-17 liter bass reflex box in my situation.

After searching for a while, this design is the one that comes closest to my requirements.

- Do you think I can increase the height of the box and reduce its depth without reducing the quality of sound?
- Do you happen to know any other plans that meet my requirements?

As a rock and metal fan who likes bass but does not want to use a sub I also found the Cube Audio F155 to be a very appealing alternative, especially because of its much lower resonance frequency.

- Do you have any thoughts on how to decide between the CHR70 and the F155?

Your help is much appreciated :)

Regards

Florian
 
Florian - while it's normally considered feasible to adjust the ratio of dimensions in a conventional BR box while retaining the net internal volume and vent tuning, there are a couple of things to consider:
- the plastic frame bezel on the CH series are approx 123mm, so there's a practical limit to how narrow you can go with your baffle and avoid constriction of the side panels - the narrowest I've ever used for this driver is 140mm internal width ( FH3)
- compressing the WxD ( CSA) and extending the height can transition the operation of the box from a theoretical BR to quarter wave action ( MLTL), wherein driver and port placement become more significant

The Mark9 designs looks like a fairly straightforward BR which should perform quite well with the CHR70, but if you read further up in this thread, you'll note there are quite a range of enclosures for this driver, from smaller desk top to floorstanders. If your application can accommodate something like the Pensil or FH3, I'd wager you'll get much better bass extension and dynamics than any of the smaller designs.
 
Thanks for the quick reply! I enclosed a small sketchup of my listening situation. I entirely agree that a Pensil or Tuby would increase bass extension and dynamics compared to smaller designs noticeably. As you can see on my room plan I have space to accommodate bigger designs but I am concerned about two things:
a) the stereo-triangle would not be optimal, because the speakers are far away from each other but I am rather close to them and
b) the desk I am sitting at is massive - so there is no straight line between the end of the tube near the floor and my ears.

Given a) and b) I thought going for speakers on the desk would be necessary.

When you look at the room plan, what are your thoughts on that?

Regards

Florian
 

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First thought would be to suggest a narrow profile floorstander such as Pensil, but that would place the driver centre at approx 740mm from floor - most likely right at work surface height. You could raise them with a false bottom or separate stand, but Scott would no doubt say some thing like "at the risk of sacrificing some of the floor boundary coupling that is part of the design calculus" . Neither can the driver location or internal height be "stretched" to suit aesthetics - that is, without turning it into something else that may or not sound fine.

Any of the smaller desk-top enclosures would be a reasonable alternative. Of course they wouldn't develop the same bass extension, but a separate woofer could always be added should that prove to be a major shortcoming. FWIW, In both my "desk-top" set-ups, I like to raise the enclosures at least 6"
 
Florian,

If you have not got the CHR-70, then you might consider picking up the CHP-70 Gen-1 if still available with one of the dealers in Europe. The paper is softer and probably will be more suitable to listen to in semi-nearfield setup.

But then, we would not be discussing a "CHR-70 application", would we? :D
 
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