Jamo D830 (Concert 8) crossover

Concert 8/D 830 has very good bass but it is sounding imbalanced for explicit reasons.It's a well designed bass-reflex,with a poorly designed crossover.Personally,I like Steve's schematic but I have made some modifications( parts numbers as in Jamo's original schematic): L1=1.5/0.5, L2=0.25/1.3, L3=0.22/0.4
C1=14.7, C2=5.6, C3=10, C4=6.8
R1=1, R2/R3=3.3 and 10R+2.2μF zobel

L values in mH/ohm,C in μF, R in ohms
What do you think of?
 
I'm not sure that works better, but it's your project. I got a hole in the midrange there, and a 0.25mH with a resistance of 1.3 must be rare as hen's teeth. Really, "if it's not broken, don't fix it" is the engineer's motto! Fixing the notch was the main event. The idea is to get the rolloff as straight a line as possible. :D

Original:
689675d1530454119-jamo-d830-concert-8-crossover-jamo-concert-8-crossover-2-png


Mine:
690603d1530968339-jamo-d830-concert-8-crossover-kimon-final-jamo-circuit-png


690602d1530968339-jamo-d830-concert-8-crossover-kimon-final-jamo-fr-png


You should post your frequency response if you want someone to check it.

Couple of Boxsim settings which matter. Boxsim needs to know the (minimal phase) frd measurement was made in "the box which is simmed". Acoustic centres (SEO) I guessed at 50mm for the bass and 17mm for tweeter. I used medium settings of 126 data points. I usually import over similar Visaton drivers to keep some factors similar. The AL170 and the SC10N here.

I did find my original sim was not very accurate due to some poor guesses. But I'm getting the same as Dissi now. And I think the phase is a bit butterworth, ie not precisely aligned.
 
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I have never used in the past Boxsim or any other simulator,so I did sims with Dissi's set up, from his post.The tweeter circuit you called "disastrous" (4mF cap in series, shunted by 0.74 mH and followed by a series 12 ohm resistor) works (curiously) fine.Sadly I don't know yet how to extract and post images of the simulations.L3 coil exists in Jamo's high pass (R=1.3ohm),of teethed hen I have never heard!
 
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Better late than never!
After a year and a half,I want to express my sincere compliments, for their invaluable help, to system7 for his patience,dlr for his benevolence and Dissi for providing an easy path to the solution.May God bless you all three and give you a happy new year!

Glad to hear you were successful. Please share the details of your final solution.
 
Glad to hear you were successful. Please share the details of your final solution.


I will,but I haven't figured out yet how to extract crossover diagrams etc. from Boxsim.The loudspeaker in discussion has a much better tonal balance (to my ears) now and the modification is cheap and easy to do.(System 7's solution is a good one too).If found secondhand in good shape,it really worths a try.
 

radule

Member
2006-08-06 11:05 pm
With original d830 I found bass roll-off problematic. There is a notch at 4.9kHz
in cross over, but at 7.4khz there is a peak extended in time.
At 7.4khz its only around -18dB.


Brake up on tweeter is also visible.

Some pictures of original speaker measurements in attachment.
 

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Hello Radule.
I am glad to see that other people also are meddling with this excellent speaker (in terms of cabinet construction and speakers selection) ,"amputated" (in its performance) by the crossover.
Yes,the measurements you are providing are similar to the ones at posts #55 and #56 by Dave and Dissi respectively,and proove that the crossover needs redesign.I used Boxsim of Visaton,which looks very accurate for this purpose.
Woofer's resonances after 4kHz aren't difficult to be reduced.
 
I would also add that, if I recall correctly, this particular tweeter is much the same as the Seas T25C003 that I treated, the second link on the page at kimon's link for "Another Commonly Found Tweeter Problem and Fix". Having never opened the 001 version, I can't say if it needs the same treatment.

In looking back, for the lambs wool insertion, I no longer wrap it before stuffing it in, but it can help with some tweeters I suppose.

I also noticed that there is a typo on the T25C003 page. It says 100" wool, but should be 100% wool. It only took me 15 years to notice that.

Dave
 
The section on Tweeter Tweaks is one of the oldest at my site. I've fixed a couple of typos and made small changes to update to the latest HTML standards (not everything of course). Most of it is internal and not noticeable by someone viewing the site. There are too many pages to update all of the site, but I'm doing that periodically when I feel like tweaking some of the pages. Some of the code is so old that some of it is now deprecated and may not display properly in the newer browser versions, though I avoided using most of the "fancier" coding techniques and mostly use plain old HTML/CSS.

Dave
 

lmaobrah

Member
2020-11-30 8:20 am
Hello from Dec 2020!

I happened to buy a used pair of these seas excel w17e-jam.
Thinking about building a very budget speakers, starting from having only the woofers.

- Also I plan to use the crossover provided by System7 from #68
- What's the good alternative tweeters for Seas T25CF001, it's a lot over my budget. Will the cheap Vifa works, for example D25AG-35-06
- All other recommendation would be appreciated.

Cheers,