DIY 9.4.6 Build

[trevordj]

And now the final step. It is always very satisfying to see so much work come together.





And now they will bake in the garage overnight, I have a heater and can crank it up to about 90 degrees in the garage. RIP my electric bill. After they have sat for a couple of days I can color sand, polish, install the feet, tape off the bottoms, and start painting what you will actually see, the top and sides of the cabinets.



Tomorrow I will start prepping the LCRs for paint on the bottoms.


I am going to have to name these subwoofers as that seems to be the thing to do. I’ll have to think about some kind of kick ass name for them.

[trevordj]

Some more progress today. I am working on sanding the clear flat with 500 grit wet. Rather than polish I am going to do a glow coat of clear over the top. Usually just one or two coats of thinned clear coat does the trick.



I turned my attention to the LCRs.

I had to modify the internal port flair so I could fit it between the braces. Not too big of a deal, I mostly just cut off the mounting flange (I actually am using what was supposed to be the internal port as the external. The external port had mounting holes and a larger flange that I don’t need.



Barely got it in there (that’s what she said)



I laid the 3m panel bonding adhesive down on the baffle then applied the ABS cement to the port, glued the internal flair to the external flair, and then laid the port in the epoxy.



Then I built up the epoxy on the outside of the port. I will sand this flush to the baffle after it cures for 24h.



Unfortunately I won’t get much done today because I am waiting for epoxy to cure. It’s Friday so I guess I will take it easy... and keep sanding the clear coats.

[trevordj]

Some more progress today. I am working on sanding the clear flat with 500 grit wet. Rather than polish I am going to do a flow coat of clear over the top. Usually just one or two coats of thinned clear coat does the trick.



I turned my attention to the LCRs.

I had to modify the internal port flair so I could fit it between the braces. Not too big of a deal, I mostly just cut off the mounting flange (I actually am using what was supposed to be the internal port as the external. The external port had mounting holes and a larger flange that I don’t need.



Barely got it in there (that’s what she said)



I laid the 3m panel bonding adhesive down on the baffle then applied the ABS cement to the port, glued the internal flair to the external flair, and then laid the port in the epoxy.



Then I built up the epoxy on the outside of the port. I will sand this flush to the baffle after it cures for 24h.



Unfortunately I won’t get much done today because I am waiting for epoxy to cure. It’s Friday so I guess I will take it easy... and keep sanding the clear coats.

[trevordj]

I am figuring out the process for flushing in the ports to the baffle. I always thought it looked cool to do it this way as it adds that extra little bit of perceived value. I am sure there is a fraction of a percent performance advantage as well. I think I got it down so I can finish this step now for the rest of them.

I sanded down the panel adhesive epoxy I applied yesterday.



I made a 3” radius jig for spreading body filler.





Sanded then re-applied filler a few times until it is perfect.






I’ll start spraying paint again when the weather cleans up.

[cwmcobra]

The attention to detail is off the charts on this! You deserve for them to sound spectacular as well!

Thanks for the updates!

[trevordj]

Jun 7, 2020 11:09:39 GMT -5 cwmcobra said:

The attention to detail is off the charts on this! You deserve for them to sound spectacular as well!

Thanks for the updates!

Thanks a lot! Sometimes I am tempted to just slap some duratex on and call it a day but I enjoy the process of trying out new techniques. Hopefully I can get the subwoofers done in the next week or two though, I want to hear them!

[trevordj]

More incremental progress. I got the rest of the ports shaped and ready to go.



The subwoofer bottoms are sanded flat at 600 grit and are ready for final flow coat of clear.



Let me know if I am posting too much. I post daily so I can document everything that is going into these. I don’t want to spam the board too much though so I can knock it off if it is too much.

[siggie]

Keep ‘em coming. Awesome project!

siggie

[cwmcobra]

Not too much at all. Keep them coming!

[butchgo]

I agree!!!!!

[trevordj]

Thanks guys! I’ll keep the updates coming.

I caught some nice weather today so I sprayed the bottoms of the LCRs. The procedure was the same as for the subs although I was able to simplify it. With the subs I block sanded at this stage and had to re-coat with primer. This time
I just hit them with the DA and I think that will be sufficient.

The KD3000 was sanded with 360 grit.





Ready to spray



Sealer



Sealer 2



Base coat



Clear coat



With the LCRs I am going to simply cut and buff without spraying a flow coat to see if there is any difference compared to the subs. If that step can be eliminated, great.

[trevordj]

I got the final spray step done for the sub bottoms. They have been color sanded and cleaned.



Clear coat on with an extra ounce of reducer as a flow coat per House of Kolor technical recommendations. I will still cut and polish these but it should go pretty quick



Shiny!




-Trevor

[cwmcobra]

I'm really enjoying watching these speakers come together. Envisioning finishing the paint, installing drivers, crossovers, terminal plates, plate amps (?), etc. And final placement in the theater. The final "enjoy" will be your review of how they sound. Lots of work, but lots to enjoy!

Kudos on your patience!

Chuck

[megash0n]

Jun 10, 2020 21:09:32 GMT -5 trevordj said:

I got the final spray step done for the sub bottoms. They have been color sanded and cleaned.



Clear coat on with an extra ounce of reducer as a flow coat per House of Kolor technical recommendations. I will still cut and polish these but it should go pretty quick



Shiny!




-Trevor

I'm not much for the gloss, but those do look very nice. You do exceptional work my friend. I appreciate it because I understand how much effort and talent it takes to get that shine.

[trevordj]

Jun 10, 2020 21:40:20 GMT -5 megash0n said:

I'm not much for the gloss, but those do look very nice. You do exceptional work my friend. I appreciate it because I understand how much effort and talent it takes to get that shine.

I am actually with you on that. I am normally a flat black fan. This is a compromise between me and my wife. She is letting me build these monstrosities but she wanted them to have a gloss finish.

[megash0n]

Jun 10, 2020 22:17:31 GMT -5 trevordj said:

Jun 10, 2020 21:40:20 GMT -5 megash0n said:

I'm not much for the gloss, but those do look very nice. You do exceptional work my friend. I appreciate it because I understand how much effort and talent it takes to get that shine.

I am actually with you on that. I am normally a flat black fan. This is a compromise between me and my wife. She is letting me build these monstrosities but she wanted them to have a gloss finish.

Yeah, I'm definitely a flat black... Disappear in the darkness person. At least they are pretty and she's happy. 😂😂😂
You can always throw a flat black sheet of burlap over them when it's time to watch a movie. 😉

[trevordj]

Jun 10, 2020 21:32:56 GMT -5 cwmcobra said:

I'm really enjoying watching these speakers come together. Envisioning finishing the paint, installing drivers, crossovers, terminal plates, plate amps (?), etc. And final placement in the theater. The final "enjoy" will be your review of how they sound. Lots of work, but lots to enjoy!

Kudos on your patience!

Chuck

Thank you Chuck! I am getting really close and I can't wait to actually just enjoy these in the room.

No plate amps for me, the subs will be running off of a couple rack mount SpeakerPower SP2-8000s.

www.speakerpower.net/store/p24/SP2-8000-DP.html

These are the same amplifiers used by JTR and Seaton, super nice stuff.

[markc]

Wow! A real labour of love and cabinet making!

How do you learn the design so that what you end up with actually sounds good and balanced and as good as something you could buy?
Is it a design you downloaded or is it trial and error?

[trevordj]

Jun 11, 2020 0:05:47 GMT -5 markc said:

Wow! A real labour of love and cabinet making!

How do you learn the design so that what you end up with actually sounds good and balanced and as good as something you could buy?
Is it a design you downloaded or is it trial and error?

Great questions!

There is a lot of work that goes into designing something like this. I have some experience building subwoofers in car audio applications which translates well to building home subwoofers, in fact it is much easier, but designing hi fidelity speaker enclosures is much different and more complicated.

There are various levels of DIY when it comes to this. There are websites like madisound, parts express, and diy sound group where you can purchase “kits” of speakers that come with various options of building (my atmos speakers were a kit purchase, I just had to assemble the crossovers and make the enclosures but there was no "design" involved per se). Some are just a pile of parts and a schematic with plans for the cabinet and crossover that you have to build, some come with everything pre-assembled and with the cabinets already cut needing to just be glued together and finished. Then there are also forum groups where designs are shared in less formal matters.

In my case this is at the very far end of the DIY spectrum (true DIY one may argue rather than assemble yourself kits aka AIY), I have designed the cabinet and will design the crossover myself without any pre-existing kits or schematics to go by. Others have used my combination of drivers, however, so it is definitely a viable combination there are just no available schematics.

Digging into how these are designed as you asked is complicated. It starts with choosing drivers that have similar sensitivity and directivity at the anticipated crossover point. In this case the acoustic elegance driver is very efficient and needs paired with an equally efficient tweeter. The directivity matching typically comes in the form of some type of waveguide for an application like this (two-way with large woofer). When a large woofer is paired with a tweeter it will necessarily be crossed over high enough that the woofer will be beaming to some extent at the crossover point (this is a physical phenomenon, as the wavelength of the sound produces becomes smaller than the cone diameter the sound emitted will narrow in three dimensional space). Using a horn or waveguided loaded tweeter in this circumstances is common for two reasons, 1) it narrows the dispersion of the tweeter and 2) it increases the acoustic efficiency of the tweeter. There are arguments on both sides about having a speaker, such as the one I designed, which will have a relatively narrow dispersion pattern vs. one having a broad dispersion pattern. I personally ere on the narrow side of this argument as it reduces the effects of the room on the speaker response but does so at the expense of having a narrower "sweet spot" of the speaker response.

With some of this in mind, and with a general size constraint in mind drivers are modeled using one or several enclosure modeling programs. These modeling programs range from simple (such as Win ISD) to complex. I used two programs to model the enclosure, one was an excel spreadsheet based program designed by the late Jeff Bagby, and the other is a very powerful and complex program called vituixcad. I like to use Jeff's software for initial exploration as it is easy to enter driver parameters and get some ideas about which speakers will meet the design goals. REgardless of the program used, the speaker's driver electrical parameters are entered into any of these programs and various sizes, alignments, box types, etc can be modeled until something that looks decent, is practical, and suits the goal of the project is found. When I say "looks decent" I mean the proposed frequency response looks smooth and extends as deep as you need it to, in this case about 60hz is as low as I want these to play as I will be using subwoofers. There are ways to predict whether a speaker is more suited to a vented vs. sealed enclosure but really any speaker can work in any enclosure type depending on your physical constraints and goals.

Enclosure design and crossover design are very much linked. The dimensions of the box and location of the driver in the baffle will affect the sound of the final product. This affect can be modeled and taken into affect when designing the crossover.

This is getting long so I won’t keep rambling. With modern modeling software hopefully there isn’t a lot of trial and error when it comes to the actual cabinet design but models and real world results can vary. It is usually safe to build the cabinet too big and tune the box too low, the port can easily be shortened and the box reduced in volume if necessary. In this case my ports are now fixed in place so I am relying on my box model being accurate. My box design is based on my actual measurements of the speakers electrical properties so it should be good. If you build a cabinet based on published, rather than measured T/S parameters tweaking is identical needed because the law parameters can vary compared to published by quite a margin.

I learned most of this from a couple books, Speaker Building 201 and the Loudspeaker Design Cookbook. Both excellent comprehensive reads on this very complicated topic. The parts-express forum is also a source of a wealth of information. I have only been digging into this stuff for about 5 years and I am still very much a novice.

[trevordj]

Jun 11, 2020 0:05:47 GMT -5 markc said:

Wow! A real labour of love and cabinet making!

How do you learn the design so that what you end up with actually sounds good and balanced and as good as something you could buy?
Is it a design you downloaded or is it trial and error?

Here are the enclosure simulations I came up with for this design.