Matt's Gedlee Summa Abbey Kit Build - diyAudio
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Old 9th January 2009, 10:05 PM   #1
pjpoes is offline pjpoes  United States
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Default Matt's Gedlee Summa Abbey Kit Build

Ok so I've only just received the parts and begun the build, so I thought I would start the thread, but this will not be a complete A-Z thread yet.

First, As many have commented, Dr. Geddes has been very responsive and put up with a lot of dumb and pointless Emails. For this, I applaud his patience and appreciate his willingness to openly communicate. After reading Dr. Geddes white paper, patents, and various publications, I began to think his speaker design was the perfect replacement for my Home Theater Speakers. After over 10 years with various Focal based speakers, some Infinity Emit based speakers from the 70's, and various other designs and projects, I was dissatisfied with the performance of these speakers in the dynamics department. Not just with movies, with good music I always felt like the speakers were holding back the performance, causing it to sound less than real, less than life sized.

I tried larger speakers with ever more drivers, but never found what I was looking for. When I had that "ah ha" moment, and realized that efficiency was what I needed, speakers of much greater efficiency, speakers which were working far less hard to achieve the spl levels I needed without entering into any sort of natural compression, I found Dr. Geddes speakers, and thought they might be just what the Dr. ordered. I was a little afraid, in fact, I'm still a little afraid that these may sound like every other horn speaker I have heard. That is, Bright, brittle, thin, nasaly, ear piercing, etc. However, one thing those speakers could do was dynamics, so if someone could get rid of that horn sound, and retain all the other good qualities, it seemed like the perfect speaker for me. Reading Dr. Geddes comments and work, he seemed to share many of my more recent opinions on speaker design, and was saying all the right things to attract me to his designs. While other designs have sounded good to me in different ways, few were in my price range (JBL Everests and K2's are just too expensive for me).

As for the construction, all I have achieved thus far is building the basic shell of the cabinet (the first step in his instructions). Next is to do the rough sanding and laborious fill and sand process. I hope to start that tomorrow. Then I will attach the braces and rear panel pieces.

I have no major complaints, but I would be remiss if I didn't comment on some issues I have had thus far with the kit. I want to make it clear however that none of this has deterred me recommending this kit to anyone else (based on the kit, not sound). Some of the panels were slightly damaged. I think this was the result of packing those thin strips against the top panels and shipping causing them to dig into the panels a bit. None of this caused fit issues, and it will be easily repairable when I do the fill and sand. None of the panels had any fit issues like I understand some past kits have had.

While a minor issue, one thing I wish had been done for me is predrilling the woofer mounting holes. One of mine appears to have had this done, but the other two did not. As anyone who has muscled a heavy 12" or larger woofer around can attest to, its never fun placing it in the hole, marking where you need to drill, and then removing it to drill the holes. A drill guide would also have been fine.

My one last gripe is that none of my kits had any instructions included as I had expected. There is a guide online which appears to be good enough, but it appears to be for building the smaller kit. I don't think there are any real differences in construction, so it should be fine, its what I have been using. However, I think the instructions are inadequate for completing the crossovers. While I have his preliminary crossover schematic, I only have that because I asked for it a while back. My guess is that Dr. Geddes forgot to include a copy, and I'm sure he will send me one later on (I don't have the crossover parts yet and still have many hours of other work to do first, so this is no big deal).

Oh I would also like to add that I really like the polymer mounting ring that was molded into the cabinet for the woofers. This is a great idea, again, as anyone who has mounted a large woofer into a recessed hole can attest to, these tend to get damaged quite easily.

I will try and get some pictures up of what I have completed so far, and keep a stream of photo's coming so people can see what the Abbey's are like. I am building 3 of them for my front 3 channels in my theater. These will be replacing Focal based speakers I made, as well as a set of Electra speakers I will be selling off once these are complete. They will be powered by an Acurus 200 watt amp or one of my DIY amps based on Aussieamps modules. I also have a 805 based SET tube amp I could try that I just picked up from my parents house (they have been storring it for me), but my guess is that the 40 watts won't be enough for movies. Based on discussions with Dr. Geddes and my own simulations of these speakers, they can easily handle 200 watts or more. In fact, I believe they need closer to 300-400 in order to reach their peak output. Oh and I will be finishing these in a Satan black finish for now. I had some idea's to do a wood veneer, but that will be very complicated on this cabinet, and right now I just want to get them going. I may revisit this idea later one though.
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Old 10th January 2009, 03:14 AM   #2
gedlee is offline gedlee  United States
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Hey Matt

The manual is never sent with the kits as I only have a PDF version, not a hard copy. I did include this in my last E-mail to you, but you seem to have not gotten it. I have not completed the manual for the Abbey, but it is virtually identical to the Nathan and I am not sure that there will ever be two different manuals for this reason. I think that you will agree that construction is pretty obvious.

As to the woofer holes, I can practically guarantee that all three of your baffles have woofer holes (if not then something went wrong since as a rule I do this to all the baffles - if I missed yours then I am sorry, I have a jig and usually do this). I only do pilot holes, but this should be enough as all you have to do is drill them through with a 1/4' drill, or personally I just use dry wall screws when I build them. I don't bother with the T-nuts.

One thing that surprises me is that you made no mention of the waveguide itself. This is the single most important part in the entire kit and I think that the cast polyurethane is an ideal solution. The wavegiudes are so strong that you could hit them with a sledgehammer and they won't break (been there - done that). The one thing to note is that the acrylic plates bend when mounted UNTIL they are attached to the driver. When the driver is mounted, this creates a solid plate that does not bend.

As to shipping damage, I'm still learning here. Shipping is something entirely new to me and I am appreciative of any thing that you can tell me to help in understanding how this damage occurs. The parts are carefully placed so that no damage to an outside surface should occur in any case. Was the damage to an outside surface, and which one?

Caution: Peak output of those speakers in a small room WILL BE unhealthy for your ears.

Thanks
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Old 10th January 2009, 12:58 PM   #3
pjpoes is offline pjpoes  United States
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Ok first thing, I'm really sorry I didn't mention the waveguides. When I was thinking through this post, that was something I intended to mention. The cast waveguides are amazing. In fact, if I could line the inside of the cabinet with an inch of that stuff, I think I would have one of the most dead and inert cabinets ever made. They also have an impeccable finish to them. I need to get some pictures up including some detail pics of the back of the waveguides. The professionalism of their execution is impressive, given that you are making them on your own in the basement.

Ok I'm going to rehash an old comment I made to you once before about the cabinets. Having now completed the cabinets, they still seem quite lively to me. The brace isn't in yet, but I notice that the top and bottom panels seem to be quite resonant when you give em the old knuckle tap. I haven't taken any measurements, but I will be surprised if this is a very dead cabinet. Do you think their could be any benefit to adding further bracing (such as strips across the top and bottom panels)? What about some dampening material such as an asphalt or vinyl material (like dynamat)? I have some 1" thick constrained layer foam (generic black hole) I could try.

I'm going to look for that email you sent with the PDF, I don't remember this, but you may be correct.
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Old 10th January 2009, 11:33 PM   #4
gedlee is offline gedlee  United States
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On the Abbey there could be some benefit to further damping the panels, (I seriously doubt that on the Nathans) but that's up to you. I just have not found damping the panels to be very important. I am trying to keep the costs down and adding things that don't make much difference is not good value added. But go right ahead and add some if you like. I'd just add a stiff 1/2" panel in the inside wall glued down with a 1/4 - 1/8" layer of liquid nails. That will kill any vibrations - whether or not it will make an audible difference is TBD.
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Old 11th January 2009, 12:12 AM   #5
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Click the image to open in full size.
Here is two of the speakers sitting in my extra bedroom to dry over night (garage is too cold). I have now fully assembled the enclosures and begun sanding and filling. I expect another day or two of this, then sealing, sanding, sealing, sanding, priming, sanding, priming, and finally painting. Did I mention I would be sanding?

Click the image to open in full size.
Internal shot of the enclosure showing the brace and waveguide. Note the detail work on that waveguide. This has an excellent finish to it, and I agree with Dr. Geddes, it's a great material. I want to coat my enclosure in it, its so nice.
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Old 11th January 2009, 03:54 AM   #6
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Very cool. Thanks for sharing your experiences with the kit and especially the pics! Please keep them coming.

What kind of paint are you going to use?

Can't wait to get mine.

-Tony
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Old 11th January 2009, 02:38 PM   #7
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Rust-o-leum water based satin black. Same brand and type as Earl uses, but in a satin black finish. They make gloss, semi-gloss, flat, and satin. Satin has a slightly softer feel to it than flat. In reality, its better to use flat for theaters, but I feel that Satin is more durable, easier to clean, and a bit more attractive. I will be spraying it on.

I'm using Zinser shellac sealer, which I will also spray on, inside and out, then black primer, and finally the paint.

My original plan was to use glue and wood putty to seal those pocket holes for the clamping screws. The glue doesn't really fill it, and I now need to rough up the surface to get the putty to stay. I'm thinking of just ordering the finishing putty Dr. Geddes recommends. It appears to be something sold for finishing boats, and thus isn't available around me, but I should be able to order some.

I'm not sure even I will bother with this, for now I will just build it as it came, but I do think it could benefit from further baluns and bracing. We shall see, when I do cabinet measurements, if I find there are a lot of resonances, I may add some more hardwood baluns. I may also attempt to connect the top panel to the center brace. In the end, it may be a lot of work that nets no real gains.

For a more perfect finish, some of you may want to use cheap veneer, like poplar as the painted surface. I'm starting to debate this idea again. You can simply finish the mdf, but veneer will absorb less, cover imperfections in the mdf, and is more durable. Simply apply it around the bottom, sides, and top in a wrapping style, and then sand the edges to blend into the rounded corners. Putty will need to be used for final blending and finish, but that then gives you 4 surfaces that are far more perfect to paint than raw mdf. It could also be applied to the rear panel for further strength, dampening, and better finish. This same basic method was how I planned to do a wood veneer finish. I was going to apply it to the sides, top, and bottom, then blend in the edges. Spray paint all the surfaces black that had no veneer, slightly overlapping the veneer. Then finishing the veneer as desired, and finally spraying a clear coat over everything to give an even finish. A lot of manufactured speakers are done this way.
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Old 11th January 2009, 02:54 PM   #8
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You are going to create more problems with the veneer then it's worth unless you own a vacuum press and have a good deal of experience with veneer. For example, what are you going to do with rounded corners? MDF is usually painted with catalyzed type finishes like 2k Uretains or epoxy type coatings.
I would also recommend some type of mechanical joint on the brace-side connection. Even a small corner block would do. Butt joints aren't very strong and given the fact that speaker sides will be the subject to strong vibrations and pressure, I'd reinforce it.
I don't mean to butt in to your thread.
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Old 11th January 2009, 03:42 PM   #9
gedlee is offline gedlee  United States
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You are correct that butt joints are not very strong. In the manual I suggest using a screw through the sides, and maybe even the front. The thing is that the braces don't really carry any load at all so they don't really need to be that strong.

I also agree about the veneer. However, catalized finishes are not required on MDF, although you absolutely cannot use anything water based as the primer/sealer. But from what I have read and tried, the Shellac primers are the strong recommendation. On top oif that you can use anythuing that you want, but the MDF MUST be sealed and smoothed well first.
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Old 11th January 2009, 05:57 PM   #10
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I don't have a vacuum press, but have used veneer quite a bit. I typically use paper backed or wood ply veneer. I use a contact cement or epoxy to hold it down, and I have never had a problem. The speakers I finished for my brother were done with contact cement, are now 4 years old, and there are no issues.

The method I suggested was not a rogue idea, but rather a commonly used one by manufacturers and DIYers alike. I know of quite a few major manufacturers that use a smooth adhered surface to paint over. In more expensive speakers, such as those from Wilson, poplar wood veneer is used.

However, I won't disagree that it will likely be more work than I expect. I've never used it to paint over, just seen it suggested. I was not planning on veneering the rounded edges, just the sides. As I said in the post, it would only give me 4 good sides, the rest would need to be blended in. The advantage is just less sides that require the extra detail work to get right. My original veneer idea was simply to veneer those sides with a nice wood, and only paint the rest, matching the look that Focal does on a lot of their speakers. I think they do it to save money, but I thought it was nice looking, and could be applied easily enough by me to these cabinets.

Again, as suggested and mentioned, I will be sealing with Shellac and thoroughly sanding.
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