First 2-way build: Peerless 830869 8" and Seas 27TFFC in waveguide - diyAudio
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Old 25th July 2013, 04:59 PM   #1
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Default First 2-way build: Peerless 830869 8" and Seas 27TFFC in waveguide

Hi everyone,

this thread is to document my first multi-way build: a 2 way with the aforementioned drivers in a MLTL cabinet. I'm really looking forward to the challenges of designing the crossover and building the cabinets, which will also be one of my first woodworking projects. Below is a sketchup model of the cabinet I'm planning to build: many thanks to IG81 for sharing details of his own 830869 MLTL for me to use as the base for my design.

I already have the drivers, ports, and other related equipment in hand so the next big project is to get started on the cabinets. But I would like to share how I modified the waveguides because I've not seen this done, and it seems to me to be a very sensible way to approach a project like this.

The waveguide I'm using is the Denovo DW-62S from DIY sound group (the same one that was used by Zaph for the waveguide TMM). I was inspired to go the waveguide route after studying Zaph's project, but I never much liked the idea of clamping the drivers from the back. I wanted the waveguide and tweeter to be a single unit for convenience and aesthetics. So I bought some casting resin, made a mold around the edges, and filled in the waveguide with resin as you can see in the pictures below. Just in case the resin didn't adhere to the plastic I drilled holes through the center rib so that the resin would pass through and stay in. Overall I think the finished product is attractive and it has the added benefit of being much more inert than the original. The waveguides gained an extra 5-6oz of weight.

If you go this route, each waveguide requires exactly 2/3 cup of resin. I used castin' craft easycast to make mine.

Next: some preliminary work on the crossover. While I haven't yet been able to take my own frequency response measurements, I've made FRDs of the peerless datasheet and zaph's Seas/waveguide combination to use for preliminary experimentation. While my tweeter is not the same as Zaph's, the frequency response should be very close, so I think it's safe to use that data until I make my own. The best, and simplest, result I've managed to get so far requires only 3 components: a 1.8mH coil and 10uF cap on the woofer, and a 3.3uF cap on the tweeter. The result is a smooth transition around 1.6k with a deep, symmetrical reverse null and 2db of built-in BSC. I've tried all sorts of configurations including mixtures of 3rd- and 4th-order slopes, zobels, notch filters and BSC circuits, but nothing else has worked this well on paper. One thing that baffles me is that I have not been able to get any more BSC than 2db, even with fairly aggressive BSC filters. But my room is pretty small so I hope 2db will end up being enough. One last note: according to the baffle diffraction and room boundary simulator, the cabinet I'm building will produce a slight ~1db bump around 700-1.5K that corresponds precisely with the dip in FR.

That's all I've got so far! Any feedback would be appreciated, and I'll be sure to post updates as they come.
Attached Images
File Type: jpg 830869 MLTL updated.jpg (163.4 KB, 581 views)
File Type: gif 830869 27tffc 2nd order 1st order.gif (26.7 KB, 553 views)
File Type: jpg Waveguide with drill holes.JPG (734.7 KB, 562 views)
File Type: jpg Waveguides being cast.JPG (795.4 KB, 539 views)
File Type: jpg Finished product.JPG (760.2 KB, 509 views)
File Type: jpg Waveguides with tweeters.JPG (902.8 KB, 180 views)
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Old 25th July 2013, 06:35 PM   #2
Juhazi is online now Juhazi  Finland
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You should take measurement of the midbass in your cabinet and the tweeter too. Measure outdoors on solid ground from 5-6 fet diatance with the real cabinet to get precice effects of baffle and floor effects.

Simulations are fine for preliminary outlines of the design, but just that. Real life is different and sometimes it hels you, sometimes not.

I like Zaph's designs a lot, you should get a really fine speaker!
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Old 25th July 2013, 07:42 PM   #3
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Yes, I'm certainly waiting to do in-box measurements before I make any purchases toward the crossover! I did run baffle diffraction/boundary simulator so I have an idea of what to expect there, but who knows what box artifacts there will be to deal with.
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Old 26th July 2013, 03:05 AM   #4
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Nice project. I'd try to lower crossover point (increase values of both capacitors). There will be less sound "coloration" from woofer.
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Old 26th July 2013, 05:10 AM   #5
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Good advice: 4uF on the tweeter and 2.2mH/15uF on the woofer controls the woofer breakup considerably more.

On the other hand, here's a simulation with 24db slopes. Again very good phase alignment, reverse null, etc, but this crossover requires 9 components instead of 3. Is it worth it? Only if the breakup on the woofer is really obvious, I suppose.
Attached Images
File Type: gif 4uF 2.2mh 15uF.gif (27.3 KB, 194 views)
File Type: gif 4th order 3rd order mixed.gif (28.6 KB, 122 views)
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Last edited by chazdrumzalot; 26th July 2013 at 05:15 AM.
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Old 26th July 2013, 05:19 AM   #6
Jay1111 is offline Jay1111  United States
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Does the tweeter fit right into the opening of that waveguide, or does it still need to be milled down like Zaph describes?

Very nice for a first project!
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Old 26th July 2013, 05:47 AM   #7
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Thanks, I've got high hopes! Yes, the waveguides did need modifying just like Zaph described, however I cut them on a vertical band saw rather than milling. just eyeballed the depth and it only took one pass. So at this point the tweeter/WG combo is all set.
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Old 26th July 2013, 06:09 AM   #8
jlaakso is offline jlaakso  Finland
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Interesting project! I was going to get 830869 to mate with Seas 27TDC in waveguide. I made the waveguides from POM plastic (with helpful diyer and CNC machine). (Un)fortunately I got a pair of CA22RNY's for a decent price and will try to come up with something around CA22RNY and 27TDC + wg. But I will most propably try out 830869 in the future. I have been fiddling with 5.25" and 6.5" drivers in the past and now I want to try 8" for a change.

Keep us posted with the progress.
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Old 26th July 2013, 03:30 PM   #9
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Wow jlaakso, it sounds like we had exactly the same idea! As for me, I'm making the leap all at once from a 5" full range to this so I'm jumping over 6.5" entirely. Although I appreciated the "purity" of a no-crossover, point-source speaker, I got tired of all the compromises I had to make musically. Since I've never really minded listening to two way speakers, I decided to go with a two way for my next project. It took a lot of thought to come to the decision to make this particular speaker, and in fact, it was mostly due to finding a good deal on the 830869 woofers that I ultimately went this route. (I had originally intended to make a "budget" version of zaph's WGTMM with 6.5" drivers.)

Troels' TQWT was also an inspiration for the 8"/waveguide floorstander configuration:

Click the image to open in full size.

I'm even planning to overlap the woofer flange with the waveguide slightly to improve CTC spacing, although not THAT much since I don't want to route into the waveguide.
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Old 26th July 2013, 08:16 PM   #10
jlaakso is offline jlaakso  Finland
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You could mount the Peerless sideways so that the truncated frame would face the tweeter.

I'm also considering spacing them overlapping. Not sure yet if I will. I'll propably try them without the overlap and try to measure if there is lobing. And I have always wanted to try dipoles, so I will also place them in a narrow baffle as well. This will be my first own design, if it ever gets finished or succeeds propably end up with a simple two way in ported box.

Or three way.. Or dipole.. Or omni.. Errr... anyhow, I will propably have a lot of fun and a lot of four letter words. And propably learn something on the side.
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