Improving the CHN-70

[Bigun]

I have not finished breaking in this driver but I have had some experience with breaking in drivers and find that a lot of the inherent nature of the driver becomes clearer after the first tens of hours. I'm at that point now.

These are nice drivers, they sound pretty neutral to me, plenty of clarify. I have my copy (one only) in a 6 lite onken-type box and driven from a hollow-state spud amp there is no shortage of bass, mid or top-end. Final application is t.b.d. but probably small-space or desktop (not that they are limited to this).

I have noticed a tendency to be a little bright at the top-end. At the limit of my hearing (somewhere near 14kHz) there is a tendency for narrower dispersion but I wouldn't call it beaming.

More break-in will tell more. But whilst I'm looking at this driver I was curious whether there have been any eNable or similar treatments and observations ?


http://www.diyaudio.com/forums/full-range/138195-my-moon-onken-4.html

 

[Godzilla]

Very cute driver and box. It looks like the paper coned version. I just coated the back of a similarly sized Dayton PS95 - with paper cone - in hopes of reducing excessive treble with dammar - $8 plus a small brush for $1.49. I'll let you know how it works out.

Bottom line, many of the current high-value full range drivers have personalities all their own. You either love them, hate them or live with their flaws and enjoy the music.

 

[chrisb]

Maybe it's safe to come out of the closet re this one - while not my favorite Mark Audio driver (that honor goes to the MAOP7) - I quite don't mind their quirky FR tailored by Mark for a particular demographic, and AFAIC their budget price certainly makes them worth playing with.

What Jeff said about personalities - we all have them, which thankfully for the most part our loved ones have acclimated 😉 - or maybe I'm just a lucky sunovabitch



Out of the box, they'll have that small FR driver break-in period typical of Mark and Fostex's drivers for that matter, and after a couple of hundred hours will settle in.

I have a pair of them per side running in another variant of one of my favorite enclosures- the Castle Microtower, and they can definitely use a little help at the deep end, but are otherwise quite a fun listen. I'm not at home right now to confirm, and as I've built at least a dozen pair of different enclosures so far this year, I can hardly remember what degree of treatment they might have, but suspect I'd find polka-dots.

 

[xrk971]

I made some measurements of the CHN-70 in another thread (link here) and the measurements were later independently confirmed. The CHN-70 has quite a lot of "character". Most notably a large plateau from 600Hz to 6kHz that is about 9dB high and it starts falling off above 8kHz. To me, it doesn't sound pleasant at all - being very far from a flat response. I don't think any amount of break-in will change the mid and HF behavior. I also did the measurement in an OB and got similar results to the Nautaloss sealed TL enclosure with a trapezoidal baffle.

There is also an unusually high 3rd harmonic distortion peak at 700Hz:

Here is a comparison of the CHN-70 with a TC9FD which measures very flat:

I am told that the CHN-70 was designed for the Japanese market and they prefer this sound signature.

 

[Godzilla]

I wonder if sticky, icky, ooey, gooey dammar will work as polka-dots too?

 

[Godzilla]

I wonder if the Wild Burro Betsy has a similar sound to the Mark Audio drivers. Attached is the Betsy WOW (without whizzer) frequncy response. It reminds me a little of the CHN-70.

If so, my review of the Betsy is here:

https://speakerprojects.wordpress.com/2015/08/22/236/

 

[planet10]

The CHN was designed specifically to have a tailored FR requested by the Japanese distributor.

Despite that we found them quite pleasant, with good DDR (detail+). We listened in both stock & EnABLed form. We ended up putting them into a set of microTower Castles.

I got a lot of flack about their FR as the EnABLed CHN were the 1st thing available when we needed something to compare to the VIFA TC9 -- the CHN just killed them.

I am always careful using damar on drivers, as it drys stiff which can exacerbate resonance issues. I usually prefer PVA or acrylic compounds which are more flexible when dry.

dave

 

[Godzilla]

Yes Dave, I'm concerned the dammar may not work as hoped but was willing to make the modification with the DIY spirit of improving drivers. Fingers crossed but hopes not up too high. I expect it will sound similar to the un treated driver. Perhaps the sibilance will remain or be even worse. I'm curious to listen tonight.

 

[xrk971]

Try Permatex liquid gasket (stays tacky) along the interface of the cone and surround - that is one of the sources of the sibillance peak I think. I want to try that on my PA130-8.

 

[planet10]

Yes Dave, I'm concerned the dammar may not work as hoped but was willing to make the modification with the DIY spirit of improving drivers.

Me too. I have had quite a few drivers that i've had to give away, sell cheap, or just toss, from less than favourable results 🙂

I love the smell of damar.

dave

 

[planet10]

the interface of the cone and surround

ZIG 2-way glue does similar. All the Fostex FE & FF drivers we do have 2 coats on the back at the interface. That and an extra 1/2 row of spots really help clean up the FFs.

dave

 

[Bigun]

The FR plots and alike are very handy - I couldn't find a decent data sheet for the driver and one that I did find had a rather uniform looking FR that didn't make sense to me. What you have measured may or may not match what Mark Audio would measure but it does at least make sense to how they sound to me. The FR is high in the 'presence region' but still not that hilly, unlike a resonance peak.

I may try a smear of silicone on the backside near the surround, it stays flexible and rubbery which is what is needed to be a lossy aborber of nasty things.

 

[planet10]

..data sheet for the driver and one that I did find had a rather uniform looking FR that didn't make sense to me.

It looks smooth because, despite requests, it is an a huge vertical scale. Properly adjusted it looks much the same as XRK's measures.

dave

 

[planet10]

I may try a smear of silicone on the backside near the surround

Make sure it is very thin... can it be diluted?

dave

 

[Bigun]

When it comes out of the tube it's very slimy and easy to smear on a thin layer, carefully using a finger; one way to describe - it feels like rubbing grease into newspaper.

 

[planet10]

I have used silicon before, i often found it hard to control, and without thinning i don't know that i could get it as "skinny" as is required.

Michael's has ZIG 2-way glue.

dave

 

[Godzilla]

Years ago I saw someone selling a driver loaded up with silicon all over the front of the cone including the surround. They claimed it improved the sound. I wish I could find the pic. It really cracked me up.

 

[Squeak]

A peak at the upper range of 14-16 KHz is contrary to the measurements we have seen so far and even MAs own data sheet. Interesting if it is true and not just single weird driver (or listener ;-).

Regarding controlling HF peaks, why not make a concave cylindrical foam lens?
It will both spread out frequencies that are the same wavelength as the thickness of the lens and take the edge of the top.

A very easy way to do it is with two 3 cm thick foam wedges put vertically in front of the driver with a small gab between them. Pointy edge towards center.

Also this is of course completely reversible and adjustable.

 

[Godzilla]

I pressed a nickle sized wad of plumbers putty on the PS95s phase plug and it sounded worse. The treble became more fizzly. Fortunately that's a tweak that can be reversed.

 

[planet10]

Years ago I saw someone selling a driver loaded up with silicon all over the front of the cone including the surround.

I have seen a number of those… all tossed (big ones actually stripped them down, screwed to a wall and used as a screwdriver holder)

dave