Jim Griffin Jordan/Aurum Cantus in a PE Box - diyAudio
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Old 1st December 2007, 11:29 AM   #1
bluegti is offline bluegti  United States
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Default Jim Griffin Jordan/Aurum Cantus in a PE Box

Jim's design and the Parts Express 0.25 ft³ cabinet have the same front baffle dimensions - 12" H x 7.5" W. However the PE cabinet's volume is 25% larger - 536 in³ vs. 432 in³.

What effect would the larger volume have if I were to use the PE cabinets? Generally larger cabinets mean more bass. Specifically, would I need to adjust any of the crossover values to compensate in some way?

I guess I could always fill in the cabinet a bit (more bracing), but I wanted to hear others opinions.
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Old 1st December 2007, 06:41 PM   #2
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You will be just fine with the P-E cabinets. A little more volume and perhaps a few Hz lower F3 which is OK.
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Old 2nd December 2007, 04:36 PM   #3
Corloc is offline Corloc  United States
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I'm useing the box form of these cabinets with a single Jx92s. They work great. The boxes just need a little prepping to get them to set well. Mine had a little masking tape and paint build up were the baffle seats. Half hour work tops, and you just need a sharp implement.
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Old 22nd January 2008, 12:26 AM   #4
bluegti is offline bluegti  United States
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Default Wow!!! :-)

I finished cutting the holes in the baffles last weekend and mounted the drivers. I did have one semi-disaster that I'm still kicking myself about. While preparing to mount the tweeter I dropped it on the Jordan. Dented the dust cover and there is a slight dent in the cone.

My crossovers are not complete so I just hooked up the JX92S and left the G2si disconnected. Upon initial listening I cannot hear any difference between the drivers. I am very surprised about how big a sound stage these speakers throw. My room is pretty small (12x14 feet) so it doesn't take much to fill the room. However, the speakers are able to convey the size of the recording space really well.

However, after listening for about 30 minutes I am suffering from fatigue. The high frequencies are fairly harsh. Again, these have no break-in what so ever. I'm hoping that giving them some time will mellow them out a bit.

Also, I have them hooked up to my Denon receiver using a Oppo DVD player as my source. It could be that the amp and dvd combination is the issue. I'll let you know how things proceed.
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Old 22nd January 2008, 12:58 AM   #5
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Bluegti,

If you wish to listen to just the JX92S speaker without the ribbon and crossover for a few days, let me suggest a baffle step compensation circuit for you. Take a 4 ohms resistor (10 watts or so power handling) and a 1.5 mH inductor and connect them in parallel (you'll need one of these circuits for each speaker in the pair). Then place that circuit in series with the positive lead to each driver and listen. What this circuit does is to reduce the upper frequencies by 3 dB which will cure the fatigue. The drivers will loosen up a bit as you use them but the baffle step circuit is needed regardless. The crossover has baffle step built in so you don't have to worry about the above circuit except when the JX92S is used alone.

The slight increase in box volume will not impact the crossover at all. You'll have a slightly lower bass output with the larger volume.

Enjoy,

Jim
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Old 22nd January 2008, 10:46 AM   #6
Colin is offline Colin  United Kingdom
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Arghh. I keep posting about the need to protect the drivers as you work with them - just a screw can cause a dent. Been there, done that. Sorry to hear about the accident but you may find it has little effect on the sound. It's just that you KNOW it's there ...

When you work with them further, make a cardboard mask, the same diameter as the driver chassis, and cut out holes for the screws/bolts so you can fix everything in place before removing the mask. Oh and start thinking of some protection for in use. I use a pair of perspex circles which attach to the driver fixing bolts by magnets, removing them for listening (unless I want everything to sound like it comes off a 78rpm record). I got mine from www.markaudio.com but he doesn't have them listed on his site so they may have been samples.

Re the harsh sound, first make sure they are turned in correctly. They need to cross well in front of the listening position for the best imaging and sound. Second, Jim's baffle step will help a lot. I used to prefer my Jordan MLTLs without but ten minutes with Ted Jordan and the CORRECT baffle step sorted that. The sound is a lot rounder.

When you have the ribbons connected, the sound will be different again, I'm sure. Be sure and report back.

It may be worth trying another amp, if you can borrow one. I found the JX92 and the Sonic-T is a horrible match, for example, and was glad I had something else on hand to run them.

Have fun.

BTW, there's no real consensus on whether the drivers need break in. Ted says not (he's measured them on spec out of the box) and I haven't found any need but others quote up to 50 hours. I suspect it's the ears that get accostomed.
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Old 24th January 2008, 12:43 AM   #7
bluegti is offline bluegti  United States
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Default I have the crossovers completed

I completed the crossovers and installed them now. What a difference. All the grain is gone. These things sound so smooth and fill the room in an amazing way. The sound seems to be coming from a much larger space than my 12 by 14 room.

I'm using them with a Sonic Impact amp. Colin doesn't like the combination, but the sound is so much better with the crossovers that I'm not really finding any faults right now. I'm looking forward to hearing them once I get my amp project finished (a diytube st-35).
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Old 24th January 2008, 02:43 AM   #8
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Bluegti,

I'm glad that you like the sound. Your next project needs to be the 'Jordan with a Ribbon MLTL'. You'll get an extra half octave or so of bass on the low end.

Have fun.

Jim
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Old 24th January 2008, 04:34 PM   #9
Colin is offline Colin  United Kingdom
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Good to hear that you're enjoying the design. I think the Sonic-T conflicts with the unadorned JX92S above 3k. Used with the JXR6 it sounds really sweet, so I'm not surprised Jim's design clears up the problem. A shame the ribbons aren't available in the UK.
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Old 24th January 2008, 04:51 PM   #10
t-head is offline t-head  United States
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Hi,

I have JX92Ss in Ronnie Thackerys' Jordan Lean Monitor (approx 6"x6"x36") transmission line cab. Using the infamous Panasonic SA XR55 for power. After 1000 hrs, my ears have broken in nicely and I get 40hz up in room. Ted did good...I am sure Jims design modded for the PE box will be fine...might suggest changing amps, though.

Ronnies design might be the finest HT speaker in existence, YMMV. I have not heard Jim's MLTL but methinks it should be tried...and heard.

t
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