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Old 5th August 2008, 05:12 PM   #111
GM is offline GM  United States
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You're welcome!

Indeed you are, ribbons aren't known for tolerating much overdrive.

So, how do they sound now?

GM
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Old 5th August 2008, 05:44 PM   #112
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GM,

I cannot really say yet as I only connected one ribbon and it is placed at the top of the speaker.

In principle what I immediately noticed is the much wider dispersion provided by the ribbon. Actually, this was the reason why I decided to try them. While I frequently sit down at the right place to listen "properly" to music, a lot of time I am all over the room and the linearity of the Jordans above 3000hz was annoying. So, yes the sound is more present and airy all over the room.

Also, the fact that the tweeter is placed high helps when standing.

I still cannot say much about the quality of the sound but I will later put switches to compare the sound with and without the tweeters.

My only problem is that I just realized that the vertical bracing will not allow me to place the ribbon immediately above the Jordan but maybe 3 to 5 inches above. I hope this do not mess up the imaging and coherence too much.

Regards

Antonio
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Old 5th August 2008, 07:34 PM   #113
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Antonio,

You really need to try to use the JX92S to ribbon driver spacing that I recommend. It is important to do this so that the crossover will be optimized and the best sound will result. The specified few mm is one thing but a few cm distance isn't good.

Jim
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Old 5th August 2008, 08:40 PM   #114
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Quote:
Originally posted by Jim Griffin
Antonio,

You really need to try to use the JX92S to ribbon driver spacing that I recommend. It is important to do this so that the crossover will be optimized and the best sound will result. The specified few mm is one thing but a few cm distance isn't good.

Jim
Thanks Jim,

Unfortunately, when I designed the bracing I did not think about adding the ribbons, so I'm in trouble here. I will see if I can make room for the tweeter with the router even if I remove a bit of the bracing. Otherwise I will have to build new boxes, which will have to wait for next year.

Regards

Antonio
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Old 22nd September 2008, 04:49 PM   #115
wcchuk is offline wcchuk  Hong Kong
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Can I use 0.33mh instead of 0.3mh? Does it affect the sound much?

Moreover, will foil inductor be better?

I have ordered most parts and want to build a 48" one by using 6/8" MDF. Please do give me your valuable advice. I am from Hong Kong. Thank you.

Winston
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Old 22nd September 2008, 10:02 PM   #116
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Winston,

Likely a 0.33 mH inductor will be close enough to the spec'ed 0.3 mH to be acceptable. I have never used foil inductors but they should be acceptable in this design.

The MDF used in my prototypes had 0.75 inch thickness. Be sure to maintain the external front baffle width. The crossover was developed for a 7.5 inches wide front.

Best of luck on your project.

Jim
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Old 24th September 2008, 05:00 PM   #117
wcchuk is offline wcchuk  Hong Kong
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Jim,

Which part of your crossover belongs to the BSC circuit? How do you switch between full range with BSC and two-way?

Thanks.

Winston
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Old 24th September 2008, 09:13 PM   #118
bluegti is offline bluegti  United States
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Quote:
Originally posted by wcchuk
will foil inductor be better?
The DCR of the foil inductor will probably be different than the DCR for the Air Core inductor that Jim originally used.

I am working on building upgraded crossovers with foil inductors for my monitors and will be using two 2.5Ohm resistors in parallel in place of the 1 Ohm R3.

This will give a total resistance of 1.332 Ohm (1.25 + 0.082) whereas the original recommended parts had a total resistance of 1.26 Ohm (1.0 + 0.26).
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Old 25th September 2008, 12:57 AM   #119
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Let me address Wcchuk's question on the baffle step compensation internal to the crossover. The BSC is inherent in how the woofer crossover circuit was implemented. Clearly, one component impacted would be the inductor in the woofer circuit. But keep in mind that the design software optimized the entire circuit based upon in-box measurements so you can not just separate out a portion of the circuit solely for the BSC function. In conclusion, it is an all or nothing result--the circuit was derived to optimize the in-room woofer's performance vs. the measurements of the actual speaker.

In my prototypes I used a switch and a dual set of terminals on the rear of my speakers to select either the crossover with the JX92S/G2si combo or a baffle step comp circuit with just the JX92S run full range.

Finally, yes it doesn't make much sense to me to use a foil inductor with a very low dcr in the tweeter circuit and then add a small resistor in series to maintain the specified resistance in that branch of the circuit. Just use the specified inductor wire size and small resistor in series.

Jim
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Old 25th September 2008, 12:04 PM   #120
wcchuk is offline wcchuk  Hong Kong
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I think I will go for foil inductor as I believe the DCR does not affect much.

Say, for the 1.5mH one, it is on the low frequency path, thus the DCR should be as low as possible.

While for the 0.3mH one, the working frequency is 3000Hz or above, giving out reactance of value 5.7ohm or higher, the difference of DCR should not be that significant.

Jim, thank you for your advice. Due to my budget, I will only try the two-way first, but I will use separate terminals in the meantime and play bi-wiring.

Winston
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