Jim Griffin's JX92S designs

[navin]

Re: JX92S designs - Line Array?

Wondering if anyone has modeled or built a line array with the JX92S?

I've built a slightly modified version of GM's 48 mltl. They perform well in my office. However, not as well in my living room. I've been considering building a line array of 2 to 3 JX92S for the much larger space.

when you say they dont perfrom as well in the living room is it only the bass that you find lacking. a small driver like the JX92 will have limitations in the bass no matter how well itis designed.

options:
2 x JX92 push push
or
JX 92 mated to a larger woofer so in fact acting as a wide range from say 100hz+

using 2 or more JX92 in a ine array might lead to losses due to lobing.

 

[rlrohlfs]

Re: Re: JX92S designs - Line Array?

when you say they dont perfrom as well in the living room is it only the bass that you find lacking. a small driver like the JX92 will have limitations in the bass no matter how well itis designed.

options:
2 x JX92 push push
or
JX 92 mated to a larger woofer so in fact acting as a wide range from say 100hz+

using 2 or more JX92 in a ine array might lead to losses due to lobing.

The speakers aren't lacking in frequency range on the bottom. I'm looking to expand on the overall performance in scale. I'd like to have a larger soundstage vertically.

Wouldn't the lobing be negated by having the drivers placed together vertically on the baffle?

Perhaps this is not a good idea...however I'll have several sets of JX92S soon and will try some experimentation.

 

[Colin]

This might do the trick.

 

[GM]

Re: Re: Re: JX92S designs - Line Array?

I'd like to have a larger soundstage vertically.

Wouldn't the lobing be negated by having the drivers placed together vertically on the baffle?

Actually, the problem is comb filtering due to acoustic path-length difference with frequency which for most folks becomes audible at around 1 WL of the driver's c-t-c spacing and increases with increasing frequency until they separate into multiple point sources (lobing).

Since the JX92S ideally needs to be heavily toe'd in, this increases the problem, so if you want a taller presentation, either mount it well above your head and angle it as required or add a horizontally mounted ribbon tweeter to what you have.

GM

 

[EUVL]

Perhaps a very dated question, but I searched through many threads and no one seemed to have made a clear remark :

The Jordan site recommends a 3 litre enclosure for closed box, but most people seem to be using something around 7-9 litres. What difference does it make going from 3 to 7 litres, sonically (I know that the Qts goes from something around 0.9 to 0.707).

Suppose I want to use a subwoofer in any case, would I be better off with a smaller closed box ?


Thanks in advance,
Patrick

 

[Colin]

The larger box gives more bass extension (an extra 20Hz or so) and less of a 'hump' in the bass. The 'hump' may be useful, however, if you want to give the impression of bass. The BBC LS5/3A used this technique. I would have thought the seven litre box would work best with a sub, allowing you to go a little lower (80Hz).

 

[GM]

........(I know that the Qts goes from something around 0.9 to 0.707).

FYI, Qts is the driver's quality factor. What you're referring to is the sealed cab's alignment quality factor, or Qtc.

GM

 

[A Sanchez]

Hi,

Sorry if this question is too basic.

Jim Griffin's minimonitor crossover diagram in principle is not a biwire design.

Is this is for a reason or this is just the way to do crossover diagrams and then anyone decides whether to biwire or not?

And, if biwire is an option, can I just separate the tweeter and woofer netwoks by making separate input paths without any change in configuration, values, etc?

Many thanks

Antonio

 

[GM]

Greets!

Normally folks have no interest in bi-wiring, or if bi-amping, using passive networks, so no need to add the extra wiring, terminals.

Right, just separate the high pass network from the low pass network if you want to bi-wire.

GM

 

[wct]

Jim

Quick question just before I start building these.

Going to build the mini monitor version first.
I have everything now except the caps and inductors.

Just wondering where you sourced these parts from (especially the inductors).

Figured I would buy the same brand and type that you did so that I can be assured they will fit on the filter board that you showed in your design pack instruction set.

Thanks Jim and best regards

Curt

 

[Jim Griffin]

I sourced my components from Parts Express. It has been several years ago so specific suppliers and sizes may have changed. You can use the dimensions listed in the P-E web pages as a guide to determine if the parts fit the board outline. The most important factor is to be sure to orient the inductors as I did on my layout. The capacitors I selected aren't the most expensive but not the cheapest either.

Let me hear if you need more help.

Jim

 

[audiosteve]

FWIW I used this one and it seems to work well. A pretty beefy piece so I doubt there will be any saturation issues. The mounting holes make it easy to install but I also glued it down as well.

http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=266-900

 

[Jim Griffin]

Audiosteve,

Normally I would recommend an air core inductor but I'm willing to listen how your project worked out. I suggest that for applications below 1000 Hz you can use cored inductors but I haven't done an A/B test to confirm whether I would be happy with the laminated coil in this design.

Jim

 

[audiosteve]

Yes, I understand the conventional wisdom against iron cores and I understand the theory behind it. But this is a pretty beefy inductor and I doubt I will ever listen at levels where the core could matter. But I wanted to hear for myself so I prototyped the design with the BSC external to the box and tried both a heavy gauge air core and the iron core. I couldn't hear any difference so I opted for the slightly smaller and easier to mount iron core. But of course just because I could tell no difference doesn't mean that someone else might not hear a difference.

 

[wct]

Hi Jim

Thanks for the reply.

So let me make sure I have it right on the inductors.

Air core inductors are preferrable for both inductors if they fit.

Also I note that there is a 5.1uf cap on the tweeter network.

Is it critical that it be 5.1 uF as opposed to 5.0 uF?

Should I parallel a 0.1 to get there if I cant find a 5.1uF ?

Thanks again Jim

Best regards

Curt

 

[Jim Griffin]

Curt,

Using a 5.0 uf in place of a 5.1 uf is close enough. This is well within manufacturer's tolerance for most electronic parts.

Good luck and let us hear how they sound.

Jim

 

[Bill poster]

Its a great read but this thread has me all confused.

To add a super tweet or not?
Would the Jordan then require a crossover or component in the signal path?
Also those of us on a tighter budget, which cheaper tweeter would suit the JX92?
ebay seems to have a good selection of ribbon tweeters all the time.

 

[human.bin]

hey guys, it's been a while Jim Griffin is not responding i also tried to PM him a couple of weeks ago, is he doing alright, someone knows?

 

[Jim Griffin]

Yes, I do really exist. I've been away today so I could not reply earlier.

To answer tweeter or not with a full range driver: You need to consider the dispersion of the full range driver. Off axis data on the JX92S shows that it starts to beam (narrows its directivity) beyond 3000 Hz. Hence, a tweeter like a ribbon acts to maintain a wide dispersion (well beyond 45 degrees) without appreciable beaming. I cross to the ribbon in my design at 3000 Hz and the results are very nice.

 

[human.bin]

fine to hear from you Jim, hope my post didn't seem unpolite please take a second to respond my PM about the alpair mltl internal depth when you have time