Driver polarity in a Dipole Woofer

[Victor]

…I have not posted anything in quite sometime, - been busy finishing up my Home Theater…Oh, well, - it seems it is a never ending story…

Some perhaps remember that I built a rather large dipole 3-way speaker system; here is what it looks like.



It occurred to me that I have no idea what is the proper way of wiring up my dipole woofers. They are standard Phoenix dipole stacked arrangement, - that is each woofer cabinet has 2 Peerless XLS 830500 12-inch drivers wired in parallel. The cabinets are facing in the opposite direction.

The question is, should I wire the upper woofer in phase with the lower or should they be out of phase?

Vic

[Bing Fung]

I don't know the answer, but WOW! Nice Job! Those look beautiful :T

[Dennis H]

I'd think out of phase looking at your picture. The easiest way for me to keep it straight is you want all the drivers to push air toward the listener when you apply a +DC voltage. If you are using 4th order crossovers, that would also include the 10" stack and the ribbon.

Dang, I still love the looks of those babies!

[Victor]

Bing Fung,
Thank you, - it was a HUGE JOB to put it mildly...NEVER to be repeated again or my better half threatens to change the address...

Dennis,
I am using DCX2496. So far I am doing 4th order L-R filters everywhere. So, you feel that the upper woofer must push forward at the same time as the lower woofer pushes back? Woul dthis cause teh stack to vibrate?

Thanks
Vic

[JonMarsh]

Hello Victor!

Beautiful cabinet work; I enjoy seeing pictures of these every time you post.

With your adaptation of the W woofer, (and assuming active networks that require nominal in phase connection to the midbass panel) the upper box should be wired electrically in phase, and the bottom cabinet should be connected in the reverse manner.

Is the sytem up and running and "dialed in"? I'm hoping to start working on my RD50 based system by late December or January, if I get the other projects finished first in time.

~Jon

[Dennis H]

Vic, it looks to me like the woofers in each W-frame are moving sideways, toward each other, so the forces due to moving mass will cancel. The thrust of the air moving forward and back is tiny. Just think in terms of airflow so all the drivers are pushing the air toward the listener at the same time and it will okay. You can test it with a 1.5V battery to make sure you have it wired up right.

[robertwb70]

what the hell just happened here? are ThomasW and JonMarsh the same person? :lol:

[Dennis H]

Thomas is Jon's evil twin.

[Victor]

Jon,

Beautiful cabinet work; I enjoy seeing pictures of these every time you post.

They do look good indeed, but, hell, they are huge,- and my shrink thinks that this project was a manifestation of my midlife crisis. …Little does she know, - wait till you see the rest of my theater…

With your adaptation of the W woofer, (and assuming active networks that require nominal in phase connection to the midbass panel) the upper box should be wired electrically in phase, and the bottom cabinet should be connected in the reverse manner. 

Yes, there is a phase correction of woofers to midrange. In fact, I dialed in a 1.45 mS delay to the midrange relative to the woofers. I do use active crossovers throughout. It is a combination of DEQ2496 digitally connected to DCX2496.

Here is a short description of my system. The DEQ is used for RTA only and the DCX does all the filtering, the necessary notch and the upper frequency boost for the RD-75 and the 6db/oct open baffle compensation for the midrange only. For the midrange I use the low-pass shelving filter from 35 Hz (+12 dB) to 560 Hz (-12 dB). I construct this filter in the DCX software from two filters, - one low pass and one high pass.

For the woofer, unfortunately, I had to build a stand-along analog processor. The DCX simply does not have the required headroom. Those woofers need about 25 dB of boost at 15 Hz, so it is a ‘no-go’ with the DCX. I simply have an analog shelving filter picking the signal from the DCX.

My volume control is built around 2 Alps motorized 4-gang pots. They are 10k log. I use IR remote that works with a circuit that controls those pots. This volume control comes just before the power amps. I am currently reevaluating this volume control set-up and I am leaning to the VCA implementation. This way I can control more then just my front speakers, as I can have more channels with near perfect tracking. My rear speakers are Carver Platinum Mark IV’s, also actively crossed. Anyway, modern VCA chips are getting quite good.

Is the system up and running and "dialed in"? 

I am not sure this system will EVER be dialed in! It seems every time I look at it I change something. Thank you for clearing up the phase issue for me.

Let me see if I got it straight. Each woofer cabinet houses 2 drivers. I wired those 2 drivers in parallel, so the nominal impedance is about 4 Ohm for the pair. Now, at the moment, I am thinking to connect the upper cabinet woofers in series with the lower cabinet woofer so that the total impedance is back to 8 Ohms, as it will keep my amplifier happy. If I do this, I guess, I simply reverse the wires to the lower woofer, so that the wiring looks something like this:

(amp output)---(+ driver -)-------(- diver +)----(amp ground)

Alternatively, I might decide to wire the upper woofer in parallel with the lower woofer, with resulting nominal impedance dropping to 2 Ohm. Assuming that my amp can handle that, the wiring will look like this:

I reverse the leads of the lower woofer and connect the woofers in parallel, - so that the positive lead connects to the negative lead.

Did I get it right? Now, other that increased efficiency, are there any benefits of parallel connection to the series connection?

I'm hoping to start working on my RD50 based system by late December or January, if I get the other projects finished first in time. 

Yes, I remember the drawings you posted. They looked good. The RD-75 I use is a great driver, - the best I heard to date. With simple high frequency EQ you can get it to about 17 kHz, which is at lest 500 Hz above what my ears can hear. I am sure that the RD-50 will do the same.

Victor

[Victor]

Vic, it looks to me like the woofers in each W-frame are moving sideways, toward each other, so the forces due to moving mass will cancel. The thrust of the air moving forward and back is tiny. Just think in terms of airflow so all the drivers are pushing the air toward the listener at the same time and it will okay. You can test it with a 1.5V battery to make sure you have it wired up right.

Thanks Dennis, I think I get it...

[ThomasW]

what the hell just happened here? are ThomasW and JonMarsh the same person?

Jon's in Denver for a week of vacation. He type a post on my PC, but forgot that I was logged in.. :roll:

[JonMarsh]

I could always just create another personna for those awkward times to avoid identity conflicts... what would we call it?

Evil Twin? (for me)

Resident Evil (for Thomas... this is his house, you know)


Hopefully we'll figure out some way to minimize the confusion, like me NOT posting when I've had a Margarita, and forgetting to log Thomas out, and log in myself!

~Jon

[Hank]

He type a post on my PC, but forgot that I was logged in..

Yeah...RIGHT.

Hopefully we'll figure out some way to minimize the confusion, like me NOT posting when I've had a Margarita, and forgetting to log Thomas out, and log in myself!

Way too complicated. It's vacation (overdue), so forget the rules, listen to some music, have more maragaritas, go chase some women, have some more margaritas and good food, listen to more music, discuss the next speaker project, have some more....... :T

[JonMarsh]

Hank,

You must be reading my crib sheet for vacation!

Had the "folks" over this afternoon for Fajitas and margaritas arty:

(our own secret reciepe and just got back from some industrial class grazing at Costco- I picked up some new jean and and sweat tops. Vacation clothing for November in Colorado.... :T

We also got the wireless router setup today, so I'm back on my own laptop. No more identity confusion! :B


Next I'm going to be mulling over panel layouts and driver arrangements in AutoCAD for the Saint-Saens. :banana:


We did some listening last night, and considering your desires for a realistic output level speaker, I'm really convinced we should pool our resources and get you up here to listen to Thomas's big rig, especially after I re-tune the IB woofer array since he's upgraded to DPL12's. :righton:

Of course, once that's settle out, I'm probably going to start whispering in his ear about getting TC2's in it, but I'd better wait on that till he sells me the few extra ones I want for my current projects. I think ThomasW is the Rocky mountain stocking distributor for OAudio, given the number of TC2+ he has in his basement.

Seriously, we are going to tune up the Arvo's this week, since he's gotten the TC2+ installed, and we're pretty much ready to rock and roll.

I'm just wishing I already had the LspCAD 6 upgrade. :sn Soon....


~Jon :later:

[Brian Bunge]

Jon,

With all your project ideas I've missed something. What is the Saint-Saens?

[ThomasW]

What is the Saint-Saens?

It's Jon's newly coined name for the RD50 dipole speaker.

[CraigJ]

Hank,

You must be reading my crib sheet for vacation!

Had the "folks" over this afternoon for Fajitas and margaritas arty:

(our own secret reciepe and just got back from some industrial class grazing at Costco- I picked up some new jean and and sweat tops. Vacation clothing for November in Colorado.... :T

We also got the wireless router setup today, so I'm back on my own laptop. No more identity confusion! :B


Next I'm going to be mulling over panel layouts and driver arrangements in AutoCAD for the Saint-Saens. :banana:


We did some listening last night, and considering your desires for a realistic output level speaker, I'm really convinced we should pool our resources and get you up here to listen to Thomas's big rig, especially after I re-tune the IB woofer array since he's upgraded to DPL12's. :righton:

Of course, once that's settle out, I'm probably going to start whispering in his ear about getting TC2's in it, but I'd better wait on that till he sells me the few extra ones I want for my current projects. I think ThomasW is the Rocky mountain stocking distributor for OAudio, given the number of TC2+ he has in his basement.

Seriously, we are going to tune up the Arvo's this week, since he's gotten the TC2+ installed, and we're pretty much ready to rock and roll.

I'm just wishing I already had the LspCAD 6 upgrade. :sn Soon....


~Jon :later:

Did Jon just mention Saint-Saens? Ah, the year was 2004, "the good old days". :W Be careful, we're going to run you ragged with your new found free time. :conveyer:

Craig

[JonMarsh]

Geez, was 2004 only 5 years ago? Seems more like 10!! Still waiting for LspCAD 6? Imagine! and TC2+ were pretty close to state of the art, then...

Ah, what a simpler time and age.... :B

Victor's dipoles seem just as pretty to me now as they did then- hope he's doing well!

Did Jon just mention Saint-Saens? Ah, the year was 2004, "the good old days". Be careful, we're going to run you ragged with your new found free time.

:conveyer:


Craig

You have no idea....

Woke up about 4 AM this morning thinking about the front panel fabrication... went back and checked my not so secret spy shots.... did a bit more head scratching, had what might have been a couple more minor epiphanies, but then they might have just been micro strokes.... :rofl:

This front panel will be a work of art, structurally and otherwise, and I'll have to bite the bullet and have ET develop some detailed step by step instructions for how to do it-

My new precision taper jig came in yesterday, as well as a new roller bearing out feed table...



and some other tooling bits... also took a close look at solid maple veneer at Woodcraft, including figured and curly, so if my NOS Rosewood won't cover this project, I have what will probably be a very nice fall back plan- should figure that out by this weekend and if needed order the new veneer.

This is gonna be wild....

[Victor]

Geez, was 2004 only 5 years ago?
Ah, what a simpler time and age.... :B

Victor's dipoles seem just as pretty to me now as they did then- hope he's doing well!..

Thank you Jon...I am fine and my dipoles are still kicking. I keep tweaking the x-over points and the x-over electronics also keep changing.

At the moment I am using the DCX2496. However, the only thing that is left of the original unit is the DSP board and the display board. The rest is all new. I got rid of the output board with all those funky op-amps and replaced it with a passive balanced filter. Also the digital input is new, with functional digital input receiver and Asynchronous Sample Rate Converter from Analog Devices. The electronics is ugly in implementation, so I am looking at some boards that do pretty much the same thing, but they are a lot nicer then what I have and better implemented.

The problem with my fully digital x-over approach is that the Volume Control becomes truly a nightmare. I need at least 11 fully synchronized channels! Potentiometers are out of the question here, although I am using them now, but it is a pain. I do not want to go with electronic pots, so I have been really thinking about the relay-based designs. There are some around, but they do cost and it is a major project to implement nicely with display and remote.

On the other hand, I might just scrap my digital x-over and go with an analog implementation of the same. This way a nice motorized 6-channel pot is all I will ever need.

I am also still building my ExtremA class ‘A’ amplifiers. I have 2 stereo units in progress that I am hoping to finish sometime next fall. And in the middle of this I am also learning how to measure the dipoles. Looking at Arpa at the moment. So it’s a busy life!

Victor