Cheap dipole system from Davey

[Davey]

You fellas might be interested in this:



1. Good, but not excellent drivers. 2 Peerless 850146, 2 Seas CA18RLY, and 1 Seas 27TDFC per side. Total driver cost approximately $500.00.

2. Easy construction. All panels are the same size except the two woofer ends. A single sheet of MDF or plywood will suffice.

3. Only four channels of minimal amplification required. Gainclones, etc.

4. Passive crossover between mid/tweet. Seven components total (per side) and none of them (need to be) expensive. Approximately $50.00 total.

5. Active crossover/EQ for woof/mid with (relatively) simple topology. Dedicated circuit board design in the works. Active crossover/EQ/power-supply parts approximately $100.00 total.

6. Terrific performance considering the amount of dollars invested. (These don't sound like box speakers.)

Total cost approximately $650.00 and a bit of sweat equity.

Cheers,

Davey.

[RonS]

Davey, this looks like an excellent starter dipole system. I can't seem to find the Seas Mid at either Madisound or Solen though.

I'd be curious to see both the passive and active crossover schematics. I'm currently working on my own dipole design that should be fairly inexpensive, except that I've chosen the HiVi M8A woofers, which need a fairly steep and low crossover point.

Ron

[JonMarsh]

Looks like a lot of value there, Davey!

How do you like those CA18RLY's? That's a relatively newe one for Seas, and the on axis curve looks pretty good. What are your crossover points and slopes? Do you plan to publish the finished design?

~Jon

[Davey]

All the drivers are available from Madisound, but the CA18RLY is really new so it isn't listed yet in their catalog page.

I'm fairly impressed with the CA18 driver. The response is nice and flat with no crazy breakup mode like the metal cone drivers have. The basket is the same as the W18 drivers so it's fairly open and vented on the back, but the motor is not an Excel. They have a very natural sound although not quite as detailed as the W18 drivers....of course, they're waaaaaaay less expensive.

I'm still fiddling a bit with the crossover design but the xover points are 130Hz and about 2000Hz for the mid/tweet. A second-order electrical filter on the low-pass and third-order electrical filter on the high-pass creates LR24 slopes. No pad required on the tweeter. There's nothing fancy here.

I'll publish all the information when I get finished. I have a bunch of photos also...some of which show the backside of the midrange baffle and how I mounted everything.

These are fairly compact....more compact than the photo makes them appear.

Cheers,

Davey.

[Al Garay]

I will be ready to take the ferry ride over to lend an ear.

Al

[Davey]

Al,

I'm diddling with the crossover a bit more (some components on the way from Madisound,) but when I get it pretty well sorted you fellas should come over. I'll be in touch.

Davey.

[Davey]

I did a little more work/listening this weekend and have posted some further information. It sounds pretty darn good.

https://web.archive.org/web/20110125024439/http://home.comcast.net/~dreite/Davey/Davey.htm

Davey.

[Hank]

Davey, lookin' good. Glad to hear they sound like a great value. Some of us might be interested in the circuit board, as it could be applied to different driver compliments. Might do a group buy to have it fabbed at a PCB shop.

[Jerry Pease]

nice job,

[Davey]

Hank,

Yep, the circuit boards could be multiple-usage. I have the pcb design finished already.

I'm not sure how much interest there would be, but of course, the-more-the-cheaper.

Thanks Jerry,

Davey.

[Davey]

Gents,

I've done some further work on the speakers and updated the page with more information.

https://web.archive.org/web/20110125024439/http://home.comcast.net/~dreite/Davey/Davey.htm

I think $650.00 is an accurate number for the total cost. The only thing I didn't include was the price of the wood and the enclosure for the active crossover/EQ.

They sound pretty darn excellent for the price. If you know someone who might be interested please pass along the weblink.

Happy New Year.

Davey.

[RavS]

Looks like a great design Davey. I may build a set even though I haven't finished the last dipole project I'm working on.

So what do you think of the TDFC tweeter as compared to the Millenium? I really like the Seas paper drivers, but I'm curious of this tweeter. Does the TDFC crossover low nicely just as the Millenium is able to? BTW, my current unfinished project uses the Millenium.

Thanks.

P.S. Just thinking out loud, wonder why the TDFC is much more oft used as compared to the TDC. I suppose because the TDFC has much less time-domain distortion, but just guessing.

[Davey]

Take it from me....you should finish one project before starting on another.

I think the 27TDFC tweeter is excellent. I'm working it pretty hard in this instance with the second-order filter and lowish xover point, but it sounds fine unless I get carried away with the volume control. But, in that case the woofers are starting to run into trouble too, so it works out well.

Cheers,

Davey.

[RavS]

Yeah, I know I think I'll take your advice and finish what I've started.

Slightly OT, but what is your favourite tweeter that you've used so far?

I've used the Morel MDT20, Hiq OW1, Audax(forget the model), and Seas Millenium. I haven't heard my Milleniums yet, but I would say the OW1 is probably my favourite out of the others.

[Saurav]

Hi Davey,

I have a bunch of questions.

* What XO frequency did you use between the woofers and the mids? I'm too lazy to calculate it from the schematic

* Also, I'm looking at the schematic, and it looks like the woofer has a straight 4th order low pass with a level control, and the mids have a 4th order highpass followed by... U3A and U4A, is that the dipole EQ function? Could you describe how you settled on the EQ values? Was it just calculation, or did you measure the panel's response and then implement a complementary curve?

* Do you have any PCBs? I built my active XO on a generic PCB, and the wire dress is quite messy. And it's in a Tupperware box I've been thinking of re-doing that for a while and putting it in a proper shielded enclosure. I also noticed that you went with separate pots for the woofer level control. That's what I have now, and it's a pain to keep them balanced, and I'm thinking of a stereo pot for the next build. Would a linear or audio taper pot be better?

* The little caps around each opamp in the photo - are those PS pin bypass caps?

Let's see... I have all the opamps I'd need, so I should be able to build this. If you're building/selling PCBs that would be a big help, but it's not impossible to do this with a general purpose PCB either.

Thanks,
Saurav

[Davey]

The crossover between woof/mid is 120Hz. There is dipole EQ following the filters on both the mid/tweet and woofer sections. The mid/tweet section also contains a notch filter. I measured the panels response and created the EQ from that....that's the only way to do it.

I used separate pots for the woofer level control only because I didn't have a 1k dual control in my parts bin at the time. It's not a problem to keep them balanced because the adjustment range is reduced greatly with the addition of the other divider resistors.

Yes, the little caps are for local bypass.

I don't have any of the circuit boards left. (I only had a dozen made.) But, it's easy to get more.

Cheers,

Davey.

[tktran]

You've probably been asked this a dozen times, but

a) Is it possible to turn the woofer section 90 degrees, so that the system has a more compact footprint?

[Saurav]

I thought that looked like a notch filter. OK, now I see the EQ sections. Thanks. I have a long list of projects piling up, and this will be one of them.

[Davey]

Well, probably.
The mid-baffle positioning front/back would be a concern since there is no facility for time alignment on the active crossover board. If the baffle were positioned flush with the front edge this would result in the centers of the woofers being behind the mid drivers by a bit. With the current setup a seated person is the same distance from the mids and the woofers, and the mid-panel is not in close proximity to the woofer enclosure.

Davey.

You've probably been asked this a dozen times, but

a) Is it possible to turn the woofer section 90 degrees, so that the system has a more compact footprint?