Tony
I would spray the speakers standing upright with spray cans. Biggest problem will be runs. Use many thin layers, don't try and load up the paint for coverage it won't work very well. Spray cans tend to work best on vertical surfaces.
I would get a can of shellac sealer from Zinser and just brush this on, sand, brush again. Just use a brush until you get a good foundation. Its far easier to brush on a thick foundation than to spray it on, even if you do use a gun (I hand do the first three or four layers.)
I would spray the speakers standing upright with spray cans. Biggest problem will be runs. Use many thin layers, don't try and load up the paint for coverage it won't work very well. Spray cans tend to work best on vertical surfaces.
I would get a can of shellac sealer from Zinser and just brush this on, sand, brush again. Just use a brush until you get a good foundation. Its far easier to brush on a thick foundation than to spray it on, even if you do use a gun (I hand do the first three or four layers.)
gedlee said:
Thanks. Coincidentally I already have this can of shellac for other projects.
Is the shellac just for the mdf, not the waveguide or for both?
And I still apply the primer after the shellac, correct? You are not saying just use the shellac and not primer?
Also, I was planning to use "gluesizing" (I believe its called, using wood glue thinned with 50% water) to seal the pores on the MDF ends, which also would get sanded before being sealed. Any concerns with this? I had done the gluesizing on my other diy project, with success. However it was just a simple bedliner finish, so I think it was less sensitive to problems.
-Tony
Hi,
I've just both a pair of 15" waveguides with B&C drivers and crossover from someone who gave up on building them.
Now I see that assembled Summas on Earl's website are being described to have a plastic/composite enclosure?
Is that correct? Would making a MDF (or whatever wood material is recommended) make a performance inferior?
Also, is this a Summa in kit or something different - anyone?
Thanks!
I've just both a pair of 15" waveguides with B&C drivers and crossover from someone who gave up on building them.
Now I see that assembled Summas on Earl's website are being described to have a plastic/composite enclosure?
Is that correct? Would making a MDF (or whatever wood material is recommended) make a performance inferior?
Also, is this a Summa in kit or something different - anyone?
Thanks!
Last edited:
Without seeing what you have, I don't think any of us could tell you if it's a kit from Dr. Geddes or not. 15" round waveguides are available from other sources. However, a good clue would be if it's made of a white cast polymer material that is very very thick, and I believe it would have come attached to a piece of MDF. I know Dr. Geddes also had a run made out of fiberglass that he intended for users to backfill with resin, foam, etc. However, I still believe these would have no mounting holes and would need to be glued into the enclosure and made a physical part of it.
Dr. Geddes typically sold the kits as complete kits, enclosures and all, so unless this came with everything else, I don't think it was one of his kits. They also don't come with assembled crossovers, the kits just comes with parts and a schematic. Again, without knowing the schematic of the crossover you have, it would be hard to know if this is one of Dr. Geddes kits. It's possible that if you told Dr. Geddes who you bought it from, he would be able to tell you if that is someone he sold these parts too.
Now as for the Summa construction. They are made out of a cast polymer material, like urethane. I believe he adds fillers to improve dampening and reduce weight, but maybe not. While one of the reasons is because it offers improved performance over wood (takes a finish better, is more stable, has great dimensional stability, makes a more rigid enclosure, etc), I know he has mentioned that a main reason for choosing this was that in order to create the necassary diffraction minimizing roundovers on the front baffle, he needed to cast it, as it couldn't be reasonably done with MDF.
However, the Abbey on down in the kit line had been traditionally MDF, and Dr. Geddes claimed that the enclosure change did not significantly reduce performance. That wood could be used to make a perfectly acceptable enclosure. I would infer from his various comments that the cast enclosure was better, but that the difference one would hear in a comparison of the two enclosure types was fairly minimal, and that other factors were of greater importance in choosing to make a composite cast enclosure. For instance, the ability to apply a more flawless finish.
Dr. Geddes typically sold the kits as complete kits, enclosures and all, so unless this came with everything else, I don't think it was one of his kits. They also don't come with assembled crossovers, the kits just comes with parts and a schematic. Again, without knowing the schematic of the crossover you have, it would be hard to know if this is one of Dr. Geddes kits. It's possible that if you told Dr. Geddes who you bought it from, he would be able to tell you if that is someone he sold these parts too.
Now as for the Summa construction. They are made out of a cast polymer material, like urethane. I believe he adds fillers to improve dampening and reduce weight, but maybe not. While one of the reasons is because it offers improved performance over wood (takes a finish better, is more stable, has great dimensional stability, makes a more rigid enclosure, etc), I know he has mentioned that a main reason for choosing this was that in order to create the necassary diffraction minimizing roundovers on the front baffle, he needed to cast it, as it couldn't be reasonably done with MDF.
However, the Abbey on down in the kit line had been traditionally MDF, and Dr. Geddes claimed that the enclosure change did not significantly reduce performance. That wood could be used to make a perfectly acceptable enclosure. I would infer from his various comments that the cast enclosure was better, but that the difference one would hear in a comparison of the two enclosure types was fairly minimal, and that other factors were of greater importance in choosing to make a composite cast enclosure. For instance, the ability to apply a more flawless finish.
Many people have thought that all they needed to make a Summa was a waveguide - not quite correct!! I never sold crossovers so those can't be mine and I never made 15" waveguides in poly. For a short time I sold 15" fiberglass "skins" which have the shape of the correct waveguide, but are nothing like the Summa or any other kits in terms of construction. People are trying to pass off the waveguides as "kits", but they aren't. Bottom line is that unless you know exactly what you are doing its best NOT to buy "parts" and try and make one of my systems. A bag of parts does not a Summa make.
Mr. hornperfect can confirm, but I suspect that these are the ones in question: Waveguides for sale.
That pair has been making the rounds over the last year...
That pair has been making the rounds over the last year...
yes, this is the pair - it's black fiberglass flares with foams, B&C drivers and crossovers (900hz i think)....
dr.geddes, i'm wondering if it is still possible to have schematics you provided buyers of these?
also under what circumstances these were sold - what was your intention, were they sold as some sort of a poor man's summa or just a completely different design with (coincidentally) a similar 15" waveguide.
my intention is not to build summas but a pair of decent speakers with OS waveguides for not too much money. this is a DIY fora anyway and i think it's a right place to discuss it.
i'm afraid the fully assembled summas are out of my reach money wise. in my defence i can add i'm not based in the US and you can only imagine what shipping costs of fully assembled boxes of this size would add - with 40% custom taxes on the top of their value plus shipping. it's mad to even think about it. i'm sorry for mentioning this but this a strong reason why some form of dr.geddes 15"-based boxes should exist at least for overseas buyers, it just doesn't make any sense to throw so much money on shipping & customs. if we would be allowed to source drivers locally and build our cabinets locally, it would be perfectly fair to pay more money to dr.geddes for his intelectual property - flares, design and crossovers (or plans).
would be interested in knowing more, thanks - especially if there's any known issues.
My intent was to allow an experimenter the option to try waveguides. But people wanted to build Summas, and that wasn't my intent. To buy the waveguides alone you would have to be an extremely capable designer with loads of experince with horns, otherwise they would be very difficult to use.
I don't believe that I ever sent out a Summa crossover schematic, but I know that I never made one for anybody. At any rate it became clear to me that people were buying them that really did not have the knowledge to make them work and then they wanted a little more help from me than I was willing to give. That's why I stoped selling them.
It's simply nieve to think that buying waveguides gets you a competent design, or that I am willing to do a competent design with the purchase of a pair of waveguides. Everyone who has bought my full kits have been elated, everyone who only bought some waveguides has been disappointed. You get what you pay for I guess.
I don't believe that I ever sent out a Summa crossover schematic, but I know that I never made one for anybody. At any rate it became clear to me that people were buying them that really did not have the knowledge to make them work and then they wanted a little more help from me than I was willing to give. That's why I stoped selling them.
It's simply nieve to think that buying waveguides gets you a competent design, or that I am willing to do a competent design with the purchase of a pair of waveguides. Everyone who has bought my full kits have been elated, everyone who only bought some waveguides has been disappointed. You get what you pay for I guess.
But no form of the 15" exists that meets your requirements - what do you suggest? There is an option for overseas buyers of all the others, but not the 15". You should consider one of those.
I don't think you would make any harm to your business if you would sell - for good money - your 15" waveguides, crossovers and schematics, leaving customers to source wood and drivers locally. You should get yourself the similar profit on this as if you would sell the fully assembled boxes and the overseas customers would be happy to save of ridiculous costs of overseas shipping and custom taxes which in many countries are not small at all (20% plus around 20% VAT - on value of the goods plus transport).
Not sure I understand the point why your best achievement would only be practically available to the US customers...
Its simply a business decision thats all. I just don't see the business case.
OT, but strange concept, if you think about it. Denaturants are added to make the alcohol unsuitable for drinking. We can't stop people from drinking, but we can tax them when they do. The penalty for not paying the tax is pretty severe in this case - blindness or failed liver, or even death. Kinda like using a trip gun to protect your garage.
Amusing that one would use denaturants in shellac. I'd think that the shellac itself would be sufficient deterrent. I suspect that the denaturant is there to prevent unauthorized upstream use of the alcohol.
Sheldon