Jordan with a Ribbon MLTL

[Doug Kim]

Originally posted by pikkuj??


If you are talking about the ribbon mltl's in question.The crossover point is 3000hz,so the Jordan does the work from about 35hz to 3000hz ,I wouldn't say it's used for mid bass!?

Yes I was talking about ribbon MLTL.
I'm by no means an expert for DIY speakers, so I'm just curious what will be the benefit of using Jordan and crossovering it at 3kHz, not something like 8kHz.
So are there very few woofers that can be crossed at 3kHz?

Thanks for kind info.

Doug

 

[pikkujöpö]

Yes I was talking about ribbon MLTL.
I'm by no means an expert for DIY speakers, so I'm just curious what will be the benefit of using Jordan and crossovering it at 3kHz, not something like 8kHz.
So are there very few woofers that can be crossed at 3kHz?

Thanks for kind info.

Doug

Hi Jim Griffin has explained it well in his second post (post #6).

 

[A Sanchez]

Hi,

I have added AC G2si ribbons to my 31' MLTL (using Mr Griffin Crossover design) but the tweeters sound disproportionately louder than the Jodans.

I am using brand new decent quality caps (ClarityCaps PX) and, provisionally, very cheap wirewound resistors.

I wonder if the problem could be that the caps need to burn-in or the fact that I'm using cheap resistors with slightly different values- 8.2 and 3.3 Ohms instead of 8 and 3 Ohms?

I do not have measuring equipment so I cannot check actual numbers.

Any help on what could be the problem would be appreciated.

Regards

Antonio

 

[DaveM]

If they seem too bright, try increasing the value of the series resistor. That will drop the tweeter level 1 db per ohm.

 

[A Sanchez]

If they seem too bright, try increasing the value of the series resistor. That will drop the tweeter level 1 db per ohm.

Dave M,

Thanks I will try that. However, the Jim Griffin's crossover design, which is the one I'm using, is supposed to include BSC already with a 3-4 db drop, so that's why I thought there was something wrong with my crossover in particular.

Actually, the tweeter is so loud that it almost seem as if it was playing alone without the jordan, so I do not know if 1db would make a difference.


Regards

Antonio

 

[Nardis]

Hi Antonio

If you can get someone with a Behringer Digital Xover to visit, you can quickly see if the tweeters are at too high a level. You can use an On line L-Pad calculator like the one at
http://www.lalena.com/Audio/Calculator/LPad/
to work out values provided you remember that Jim Griffin has included BSC in his original design. I’m sure that Jim will have advice on this.

In my experience the quality of resistors is very important. I switched to from cheap wire-wound to Mills 1% fimported rom Parts Express, and it made a big difference to the sweetness of the sound.
These cost USD3.50 each and are a little cheaper (3.25) if you buy ten. The minimum order value for international shipping is USD50. If you are going to order some please contact me privately as I may want some things myself.

 

[A Sanchez]

Thanks Nardis,

You are right, I will try to have the speakers measured to really know what's going on.

I'll send you a PM.

Regards

Antonio

 

[GM]

I wonder if the problem could be that the caps need to burn-in or the fact that I'm using cheap resistors with slightly different values- 8.2 and 3.3 Ohms instead of 8 and 3 Ohms?

Actually, the tweeter is so loud that it almost seem as if it was playing alone without the jordan...........

Not really.

Hmm, does the Jordan play fine without the ribbon and BSC connected? Clearly, something major isn't right, like a wire connection, wired wrong, amp unable to drive the Jordan's low impedance, etc..

GM

 

[A Sanchez]

Thanks GM,

Yes, the Jordan was playing fine without the ribbon and crossover. And it was also playing fine as a full range with BSC.

I really think you are right. I beleive there is a problem with the crossover construction. This morning I only had time to try it but this evening I will carefully check all the wiring.

Regards

Antonio

 

[A Sanchez]

Not really.

Hmm, does the Jordan play fine without the ribbon and BSC connected? Clearly, something major isn't right, like a wire connection, wired wrong, amp unable to drive the Jordan's low impedance, etc..

GM

Problem solved: wrong connection in the tweeter network and as a result I believe there was no cut off for the tweeter. I'm lucky I did not blow it.

Thanks again.

 

[GM]

You're welcome!

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

So, how do they sound now?

GM

 

[A Sanchez]

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

 

[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

 

[A Sanchez]

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

 

[wcchuk]

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

 

[Jim Griffin]

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

 

[wcchuk]

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

 

[bluegti]

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).

 

[Jim Griffin]

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

 

[wcchuk]

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