Half Chang build

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Jump to Latest
Jim Shearer

Jim Shearer

Member
Joined 2007
Scottmoose said:
Given that, if I'm reading the post correctly, the tops aren't even glued on & the MDF enclosures are completely undamped, I think it might be a trifle premature to be contemplating Eq circuits.

Before anything else, they need the required damping adding & the tops gluing in place. MDF is not an especially stiff material so it too will currently be resonating right where you don't want it to -the damping & brace should take care of that. Once that's done, & assuming they're near a wall, I'd be surprised if they needed any correction. In your case Jim, IIRC, you're using the 206, which isn't ideal for this kind of load -low Q, high mass-corner, rising response over ~1.2KHz; the circuit you're using will likely be dealing more with that than step-loss itself. The 168ESig. has a higher Q, lower mass corner & a slightly flatter overall response trend so needs less adjustment for this sort of box.
Click to expand...


Good points Scottmoose. I had not paid attention to the 'not glued up yet' and have no experience with MDF. (I already have enough problems w/ my lungs that I don't want to take unnecessary chances to find out how much different MDF would sound.)

And you are correct that I used the FE206 rather than the recommended FE207. That decision was based on the prior listening to FE206 and fear (perhaps unfounded) that the 207 would give up enough on the top end to make me regret using it. Despite corrupting your design, I'm still VERY pleased w/ the end product.

With continued thanks for your help, Jim
 
knightsound

knightsound

Member
Joined 2006
Half-Chang for Audio Nirvana Super 10in.

Regarding the Audio Nirvana Super 10 (stamped frame), in a previous thread ScottMoose noted, "In the case of the AN10in, given it's considerable size, my personal preference would be to either use it in an MLTL, or, a BVR type of cabinet (BR or MLTL with short horns, rather than a regular port-tube or slot). YMMV as always."

It's been driving me nuts! I've got to try the Audio Nirvana Super 10's in a Half-Chang cabinet. A recent house move helps. The main room is 12.5m x 4.5m x 3.2-7.0m ceiling. Space for low bass to unfold.

While I've been using WinISD I don't know how to model Half-Changs for the AN10. Can someone help me with the dimensions? I need to adjust the cabinet dimensions specified in "Half-Chang – Descendant of Calhoun – Fostex FE207e / Pioneer B20 / HA FR8c Moose-BVR Horn 1v01".

I'm also curious to know what level of bass below 35Hz might result.

The room will require some work to kill reflections (marble floor). The driver's specs are below.

Four sheets of 18mm ply are in the garage ready and waiting. :)

Thank you for your help and advice.

James

8 Ohm
Min.Freq.Response: 36Hz
Repro.Freq.Response: FO~18K
S.P.L. 96.254 dB/W(m)
Rated Input: 30W
Equiv.Diaphram Radius: 110mm
Equiv.Mass: 19.01g
Magnet Weight: 1400g
Net Weight: 3835g
Fs: 36.01Hz
Re: 7.2 Ohm
Mms: 22.84 g
BL: 11.981 TM
Qts: 0.286
Qms: 2.975
Qes: 0.316
Vas: 102.055 Ltr
Xmax: 1.0mm
no: 2.70%
VC dia.: 1.3"

PS Why no BVR or full Chang? Cabinet heights of 2m + = 0 WAF!
 
Q

quadtech

Member
Joined 2007
Hi All, I should be getting my Fostex FE206E drivers in a couple of weeks
and am looking at suitable cabinet designs.

What's important for me -
decent bass (my music is mostly soft rock or classical. No heavy metal stuff),
good/faithful reproduction across the range, Tube amp friendly - high
sensitivity and a uniform impedance curve, and of course, a
high WAF (which rules out the BIB and Sachiko due to their size).
My amps are a DIY Dynaco-ST70 type tube amp, and a LM3886 Gainclone.

So the choice is down to the Half Chang, the Singular and Ed's VOFO.

The Half Chang appears to be the easiest one to build.

I haven't read much about the Singular and it's performance vis a vis
other designs I am considering.

The Vofo has a couple of curved pieces which might be a bit
challenging, but I might be able to pull it off. Scott Moose had some
nice things to say about this design on the World Designs Forums.

The Half Chang and the Singular each recommend a suitable correction circuit.

At this time, I am leaning towards the Half Chang (inspired by good reports on
this thread).

Appreciate any inputs from the folks here to make my decision.

- Prasad from Hyderabad, India
 
Scottmoose

Scottmoose

Member
Joined 2005
wodendesign.com
quadtech said:
The Half Chang and the Singular each recommend a suitable correction circuit.
Click to expand...

Can't speak for the Singular, but WRT the former box, only because people do keep putting drivers into it that I didn't design it for. ;) It's designed for the 207, not the 206. The latter will work, but with its upward tilted balance, it needs a shelving filter to prevent it sounding over-bright.

The Vofo was designed by my friend Ed. Not the easiest of builds, but it works very well indeed.
 
fwater

fwater

Member
Joined 2007
Hey guys, got a question about the total size of the vent mouth on a half-Chang. I'm bevelling the edges on the front at 45 deg. This decision was made after most of the build was completed (afforded by using two layers of 1/2" MDF), so a sharp 135 deg. corner will appear along the edges of the vent mouth. I don't want to double the wall thickness on the inside of the mouth, but could I put a 1/2" lip around the inside perimiter? In my estimation, this shouldn't cause too much of a negetive impact on tuning, since I'm preserving the vast majority of volume in the vent, just diminishing the area slightly at the exit. This idea is solely for continuity of (visual) flow along the front corners, so it is of course defeatable. Thoughts?
 
gychang

gychang

Member
Joined 2005
fwater said:
along the edges of the vent mouth. I don't want to double the wall thickness on the inside of the mouth, but could I put a 1/2" lip around the inside perimiter?
Click to expand...


Discussion regarding the mouth reminds of me of this type of design. No dimensions anywhere....

gychang
 

Attachments

  • mouth.jpg
    mouth.jpg
    25.7 KB · Views: 1,139
B

Bob Brines

Member
Joined 2003
[rant]

The whole reason for the big double BVR's like Chang is to get a "big" sound that is generally lacking in single driver speakers. It's not bass that is lacking, but the grunt frequencies -- 60-100Hz -- where the 6-8"ers run out of excursion. Why one would expect to get useful results out of a 3-5" driver is beyond me. No Sd means no air movement.

I'm still trying to find a cabinet for FE127E's. Yep, I get bass to 60Hz -- at 60 dB @ 1m, but I can't get 80dB average at 2m without horrendous distortion. And I'm talking baroque music where the biggest instrument is a theorbo. Sure, huge horns would probably work, as might corner horns, but I don't have usable corners.

I remain steadfast in my opinion that drivers smaller than 6" are midrange drivers and need to be rolled off below 200-300Hz.

[/rant]

Bob
 
lykkedk

lykkedk

Member
Joined 2002
I don't barely dare to ask my quistion, but the matter of fact for me, in my setup, is that after some 200+h ((breakin)) / getting used to time, my halfchang Fostex207E really sound's great. But but but, my livingroom is pretty big, so mostly modern music, sometimes sound a littly tiny, espcially when played loud.
Good :) female aka' Nora Jones / Celine etc... sound very very good on them, so the idea was to make a sub, witch could be turned on/off, so that i don't have to use it all the time when listning.

I really like the idea, trying them off, with a sub, but as i have no clue, what such a sub (diy ofcause) need's to go along with mine halfchang, i would like to know if any have some idea/projects.

I also would like to know about Crossover freq. and the size of the amp, which should drive the sub('s).

Jesper.
 

Attachments

  • severalm1.jpg
    severalm1.jpg
    91.7 KB · Views: 1,032
L

loninappleton

Member
Joined 2004
Bob Brines said:
[rant]

The whole reason for the big double BVR's like Chang is to get a "big" sound that is generally lacking in single driver speakers. It's not bass that is lacking, but the grunt frequencies -- 60-100Hz -- where the 6-8"ers run out of excursion. Why one would expect to get useful results out of a 3-5" driver is beyond me. No Sd means no air movement.

I'm still trying to find a cabinet for FE127E's. Yep, I get bass to 60Hz -- at 60 dB @ 1m, but I can't get 80dB average at 2m without horrendous distortion. And I'm talking baroque music where the biggest instrument is a theorbo. Sure, huge horns would probably work, as might corner horns, but I don't have usable corners.

I remain steadfast in my opinion that drivers smaller than 6" are midrange drivers and need to be rolled off below 200-300Hz.

[/rant]

Bob
Click to expand...

This is a good rant and like Fighting Bob La Follette said, "is this a private fight or can anyone join in?"

;)

I am curious to hear what the nature of the distortion at low frequencies you are getting with the FE127e? I played tones with them and yes Have heard some anomalies but on music they perform great and my main listening is classical. I had made a BVR Harvey (yes one) but was never happy with it. That small BR cabinet with the fancy bends gave poor effect. Looks great in SketchUp though.

The FE127e has the long master thread on design for it which has had scant attention of late (last 6 months or more.)

The BIB has provided a lot of satisfaction up until I made a double baffle to accommodate flush mounting of the driver (not required but I wanted to try it.)

But I always return to the MLTL for those pure string bass and guitar solos.

Maybe there is a prospect in a wide baffle BIB (wide as the MLTL) with compression chamber (discussed elsewhere)?
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Top Bottom