Countdown - NeoPro5i / PR170M0 / Dipole12

My Lambda Dipole12's arrived Wed but I had to leave town Thurs morning for vacation (car camping with friends in Lewiston, ID).

As soon as I got out of the car yesterday, much to my gf's dismay, I dragged out my saws and attacked the pile of leftover wood, pretty much winging it. I knew the general dimensions I wanted, 14" baffle and 8" wings.

My wood selection pretty much dictated the construction, hence my particle board "braces" which are really there to keep the wings from getting snapped off.

Today, I decided to add a top and bottom for added looks and strength and another layer of MDF to the baffle so I can flush-mount the Dipole12s with their 5/8" thick rim.

[IMGDEAD]http://www.brainwatch.us/images/dipole_back.JPG[/IMGDEAD]

Here are all the drivers sitting on the uncut baffle.
[IMGDEAD]http://www.brainwatch.us/images/dipole_mockup.JPG[/IMGDEAD]

Tomorrow will be the tedious job of cutting the driver holes.

I have a 2" straight router bit but it's a tiny bit too long for both of my plunge routers so I have to cut the rebate with 1/4" (Jasper jig) and then drill a starter whole for the 1/2" diameter 2" straight bit so I can cut through the baffle. Fun.

I also need to make a template for the NeoPro but if I run out of time, I may just surface mount it. I will be listening to this speaker tomorrow night.
 
Brian,

Congratz Bro, looking good!

Glad to see your project is progressing. You'll love the Fountek/PR170 sound... I wish I could hear the sound of your sandwich ribbon to compare vs my pure aluminum one...

What did you end up using for a crossover?

BTW: I've had mine mocked up in cardboard for about 4 weeks and I can't stop listening to them long enough to actually build the real baffles :(

Did you run BDS to see how your layout will affect the FR, with only a 15" wide baffle, you'll get a lot of Bass rolloff and will need alot of EQ to make it work...

I was going to move forward using TC2+ woofers but now I've been sidetracked with promises of better. The only problem is I have to wait :(

--Chris
 
My effective baffle width is 33" when considering the 8" wings butted against the 1.5" thick baffle.

The dimensions were influenced by Larry Selmer, an associate of Sigfried Linkwitz. John Janowitz @ AE practically insisted that I talk to him before ordering the Dipole12 woofers. I'm glad I did.

I have the Behringer as a crossover for the moment and that's as far as I've gone. Although I will soon need to rewire my output cables and possibly do the high gain mod on my grounded grid pre to hopefully elminate the hiss that has seemed to increase in level since I upgraded to the latest firmware.

Although, I'm starting to realize that maybe the Behringer isn't the ideal solution for dipole. You have to use two low pass crossovers with the woofers to 1) deal with rolloff and 2) crossover to the midrange. With the DCX2496, I'm forced to use the EQ in conjunction with the single low pass crossover. Which should be fine for the short term.

What's BDS? Do you mean that dipole.xls spreadsheet by Brian Steele? I've modeled it and well, rolloff happens. It's really an issue of how big I want my baffle to be and right now this is as big as I want it. But this is only a "test baffle."
 
I didn't either until Thylantyr started pushing the TD series woofers. I then found the dipole series and heard that Acoustic Elegance could build these from leftover parts that they bought when Lambda shut down.

It has a single copper Faraday ring. The Dipole woofers were the only ones that could not be upgraded to Apollo status which provided an additional pair of aluminum Faraday rings.

Thanks. They remind me of those big speakers from the 70s.
 
Brian,

BDS = Baffle Diffraction Simulator. BDS can be used to model the interaction of baffle on the speaker's response...

get it here : http://www.pvconsultants.com/audio/diffraction/downloadbds.htm

BTW: here is some of my work on the mid/tweet panel that I designed. I tried alot of geometries and offsets before settling on one that produced the smoothest FR response effect...

baffle2.jpg



Some previous work similar to what you are planning?? I had to place the tweeter below the midrange in order to get a decent response with a square baffle :

baffle1.jpg



If you tell me what offsets and heights you are planning for the drivers I can run the simulation for you so you can get a quick idea of the Baffle effect... I found out pretty quickly that BDS has a pretty steep learning curve but its really powerfull once you learn how to use it...

--Chris

[EDIT:] Notice the reduction in ripple on the high frequencies of the ribbon tweeter when I went to a non-square Baffle? I also offset the midrange 1.5" to smooth out the dip around 1Khz ...
 
Yes, I did play with that. I also played with Edge which has dipole support. Toggling dipole on and off made a significant difference to the midrange reponse. Significant enough to make me feel that neither programs were going to be great for modeling a dipole with wings.

In the end, I decided to just go square with the mid and tweet offset by 2".

Attached is a drawing of the enclosure.
 

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My back is aching, my driveway is carpted in saw dust. Problems uncovered. Some solved, some put off. 11:40pm I had music!

I backed out all the DCX settings from my TB/Audax/MCM experiment. Crossover is 300 and 3k, LR 24. Adjusted the levels per memory of the datasheets. Added some EQ the woofers.

About 5 minutes invested with amazing results. I can't wait to get some time to measure and tweak.

Btw, the big ribbon isn't as beamy as I expected. Standing up doesn't completely kill the highs.

Didn't get the ribbon flush mounted like I had hoped. Turned out that I didn't have a 1" collar for my router. Will get that fixed shortly.

[IMGDEAD]http://brainwatch.us/images/dipole_firstplay.JPG[/IMGDEAD]
 
very cool. Let us know how it sounds when the dust settles. Did you put a cap on the ribbon below the xo point? I stripped out the xo in my current retail speakers and when my DEQX arrives I am going to play with it actively. They use a AC G2si and have heard it is best to use a cap a little below the xo point to protect the ribbon in case of pops, DC or other stuff inadvertently coming through to them.
 
Harder question to answer. I've only logged about 20 minutes of listening time. Initial sound quality is many steps ahead of my TB/Audax/MCM test mule which I spent significant time tweaking with the DCX2496.

Once I wired it up, I zeroed all my EQ and gain settings and did some quick tuning by ear. I added gain to the woofers due to their lower efficiency and I recycled the shelf EQ setting from my test mule to deal with dipole losses. And that's it.

This is my first speaker design so I am heavily managing my expectations.
 
ultrachrome said:
Harder question to answer. I've only logged about 20 minutes of listening time. Initial sound quality is many steps ahead of my TB/Audax/MCM test mule which I spent significant time tweaking with the DCX2496.

Once I wired it up, I zeroed all my EQ and gain settings and did some quick tuning by ear. I added gain to the woofers due to their lower efficiency and I recycled the shelf EQ setting from my test mule to deal with dipole losses. And that's it.

This is my first speaker design so I am heavily managing my expectations.


question about a previous statement

"Btw, the big ribbon isn't as beamy as I expected. Standing up doesn't completely kill the highs."

what kind of sweet spot does this design give you? I'm assuming since you can hear the highs 20-30 inches above a direct shot with the tweet it's quite large...

how far away was your listening position?