Exactly like that Dave. 🙂
You're right Cal. Calhoun & Shadow were the genesis of all these boxes (I still call it the Calhoun range). When I was fiddling around in MathCad a few months back, I decided to see what other types I could come up with & did five or six. The box now known as Chang started as an idea for the 207 -I had it kicking around on my HDD and when Greg Chang mentioned he had a pair of B20s gathering dust, I plugged their specs into it & found they worked fine. Double & single mouth versions are possible for all of them, assuming the slot-vent length allows it.
You're right Cal. Calhoun & Shadow were the genesis of all these boxes (I still call it the Calhoun range). When I was fiddling around in MathCad a few months back, I decided to see what other types I could come up with & did five or six. The box now known as Chang started as an idea for the 207 -I had it kicking around on my HDD and when Greg Chang mentioned he had a pair of B20s gathering dust, I plugged their specs into it & found they worked fine. Double & single mouth versions are possible for all of them, assuming the slot-vent length allows it.
Attachments
Is that graph for the single mouth? What could I expect with a little room gain? Im thinking of building a suzy chang for the B20 and completely removing my subwoofer, If I can reach 30hz with some authority I will be happy. The speakers will be getting around 15-20 watts. The room is relatively small, at around 10 x 15 feet.Scottmoose said:
Your thoughts sir?
-Serg
The Half Chang is almost exactly what I've been looking for in terms of form factor for my living room. I'd like to move up to a much more efficient driver than the TangBand in my Needles and get a bit more authoritative bass. I'd dive into this fairly quickly if I could get a little help on a few questions:
1 - Of these three drivers which would you all recommend - FE206E, FE207E, or Hemp FR8C? How do they plot?
2 - Scottmoose, please explain
3 - What form would you recommend for bracing? Something that went the full vertical length of the slot-vent, just in the upper region behind the driver, or perhaps 2 horizontal pieces spaced evenly?
Bob
1 - Of these three drivers which would you all recommend - FE206E, FE207E, or Hemp FR8C? How do they plot?
2 - Scottmoose, please explain
for me. Do you mean at the vertical mid-point of the slot-vent?
3 - What form would you recommend for bracing? Something that went the full vertical length of the slot-vent, just in the upper region behind the driver, or perhaps 2 horizontal pieces spaced evenly?
Bob
Fast1one said:
Yes.
With room-gain? A flattening of the LF response, so more gain at the bottom end.
Don't chuck the sub, if it's halfway decent -extra LF help never goes amiss. Get another one while you're at it. Stereo bass makes more of a difference than people think. Remember though your room is actually too small to support sub-bass wavelengths.
I doubt the speakers will need 15 - 20w to go loud. About 10 would be more than sufficient to cause deafness in a room of that size, even though I gather the B20 likes some power.
Beyond that, I have no thoughts. Dangerous thing, thinking, and best avoided.
bobtrancho said:
1) I'd go with the 206 with ~4ohms series resistance. Robs it of some efficiency, but you get the usual positive attributes of a big magnet and ~91db 1w / 1m isn't too shabby. 2nd choice would be the 207 (no resistance needed). Personally, I'd avoid the Hemp Acoustics units -irrespective of their sporadic availability, from the comments made thus far, they appear to need a zobel and shelving network slapped across them to get their midrange & treble in line, without which even a huge BIB has had complaints about weak LF (!). The 207 & 206 with series resistance will have the same response trend as the Pioneer, but go about 3 - 5Hz lower before starting to roll off. Some people find the 206 a bit hot over the midband, but it's LF performance is excellent, and a set of phase plugs sorts out the midrange if its found to be a little enthusiastic.
2) No, I mean as an alternative driver position, it can go in the middle of the cabinet front panel, i.e. 375mm from each end.
3) Don't place bracing perfectly evenly -that's a gift for potential resonances. I'd use a couple of window braces with a vertical brace off-centre clamping the rear of the driver magnet against the inside of the cabinet's rear panel.
- I'll go with the 206 and see how the midrange sounds once they are together and broken in. What wattage should I use for the series resistance? My Amp10 is rated at 50W @8ohms.
- Using the alternative driver placement results in the center being only @32" off the floor - perhaps a bit too low? I'll go with the 7.5" from the top.
- I no longer have any access to CAD software but will hand draw some bracing ideas and post them.
I hope to start this within a week or so and will start a new thread with photos once I get going.
its mostly for music, so anything too low isn't really needed, I'll give it a try without a sub. As far as power, I like things loud, trust me 😀Scottmoose said:
Thank you sir!
Regards,
Serg
gychang,
Very nice, just as the rest of your projects. You just go from one project to the next. I'm Jealous!
The 1/2 Chang seems to be good for those of us with a little less room to play with.
Is there going to be a Curvy 1/2 Chang?
Thanks,
Josh
Very nice, just as the rest of your projects. You just go from one project to the next. I'm Jealous!
The 1/2 Chang seems to be good for those of us with a little less room to play with.
Is there going to be a Curvy 1/2 Chang?
Thanks,
Josh
Scottmoose said:
Hmmm.... "Massive end correction." Could you elaborate? Are we simply helping the slot output to boost the LF? Or is there something more complicated going on?
They look sweet GY, I think I may go for them instead of the half built metronomes, for bedroom speakers. They'd also make nice rear speakers for a Chang based cinema system.
When all the Chang variants are built you'll have to do a family photo.🙂
When all the Chang variants are built you'll have to do a family photo.🙂
marce said:
I may have built several but your attention to detail and flair for style make me envious.
I have run out of rooms in my small house and all my friends have their speakers for now, no more big speakers until we move probably next month... Indeed big speakers sound better.
gychang😀
>>> even though I gather the B20 likes some power.
It works great with a SI stock amp... the $30 version. I use it with a sealed box B20 so i do not notice the bass roll off of the stock SI amp. To my ears the B20 is about as efficient overall as the older Fostex 168S (rated at 94 but probably closer to 91db per watt). The B20 is rated at 94 due to a peak in its response but overall it's probably closer to 90 - 91 db per watt.
Thanks for building the Chang Greg! It's inspired additional designs for the B20 - one of my favorite wide range drivers of all time! With a helper tweeter it's such a great driver overall for not too much money. Love its full warm bass. The Chang and Half Chang must sound full and warm... lovely.
Thanks Scott for the Chang and Half Chang designs! Since i have a very tall BIB for my Fostex 165k (which is amazing as you know) a shorter Half Chang may be my next project. I could use an upgrade to the sealed B20 boxes i've been listening to for the past couple years in my office.
Excellent thread with some excellent new designs for drivers that don't break the bank!
Thanks Dave for the Half Chang drawing!
Btw, Greg, do you notice any efficiency decrease when going from the Fostex drivers to the B20? I don't notice much worth mentioning.
Godzilla
It works great with a SI stock amp... the $30 version. I use it with a sealed box B20 so i do not notice the bass roll off of the stock SI amp. To my ears the B20 is about as efficient overall as the older Fostex 168S (rated at 94 but probably closer to 91db per watt). The B20 is rated at 94 due to a peak in its response but overall it's probably closer to 90 - 91 db per watt.
Thanks for building the Chang Greg! It's inspired additional designs for the B20 - one of my favorite wide range drivers of all time! With a helper tweeter it's such a great driver overall for not too much money. Love its full warm bass. The Chang and Half Chang must sound full and warm... lovely.
Thanks Scott for the Chang and Half Chang designs! Since i have a very tall BIB for my Fostex 165k (which is amazing as you know) a shorter Half Chang may be my next project. I could use an upgrade to the sealed B20 boxes i've been listening to for the past couple years in my office.
Excellent thread with some excellent new designs for drivers that don't break the bank!
Thanks Dave for the Half Chang drawing!
Btw, Greg, do you notice any efficiency decrease when going from the Fostex drivers to the B20? I don't notice much worth mentioning.
Godzilla
End-correction? It's not really about trying to extend the bass. These boxes are just regular BR or MLTL cabinets, and I design them as such initially, then replace the usual small vent with a larger flared one (or more than one) that gives the same Fb. The rapid decrease of pressure you get from the flare reduces noise and any peaking at Fc, should either exist. As you've coupled to more air you get a larger scale to the presentation & they help act as waveguides to an extent so they sound a bit like BLHs, albeit a heck of a lot smoother most of the time as they operate over a much narrower passband.
Interesting. Cheers for that Jeff. Glad you like the box designs BTW. I reckon they should work well.
Scottmoose said:
It also seems to make the box more dominating than the driver parameters... Just look at the wide range of drivers that work in Harvey for instance.
dave
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