Cornwall 1 cabinet build, looking for advice

[Onebean]

Over a year ago, I bought components for a pair of Cornwall 1's. Time slipped away from me last summer, and I did not get the cabinets built. My plan was to start on these as soon as the weather turned this spring, but graduation, quarantines, and some other stuff popped up, knocking me off my game a bit. I am close to starting this project though, and I've been thinking through the build process, mentally preparing myself. I got a copy of the the cabinet plans from the Crites site, and now I have some questions. In no particular order, here they are:

 

Cabinet bracing? - The plans don't show any bracing. I think bracing would help keep my plywood panels stay straight, and square (seems like I always fight plywood warp). What can I add for bracing, and what should I add?

 

Support for the mid horn? - Again, nothing on the plans, but I assume that horn needs a support board under it.

 

Base riser? -  The plans show a riser 1-3/4" tall. Should modify this height at all? 

 

Ports? - when I initially joined the forum, I mentioned the build, and some folks recommended round ports along the sides of the mid horn, instead of the slotted ports at the bottom. I believe the reason was the slots are too close to the floor, and the floor can cause turbulence. All things equal, the round ports are much easier for me to build and install. I would need to know the size, length and quantity. 

 

Mounting the drivers in front of, or behind the baffle? - I know these were rear mounted originally, is there any reason not to front mount them? Front mounted might look better????

 

Mid range position on the baffle? The other thing suggested to me, was mounting the mid range above the tweeter? Any thoughts or opinions on this? Mid range at ear level?

 

K-33-E rebuild? One of my K-33-E's has a rubbing voice coil. Should I send both out for rebuild, or replace them with Eminence Kappa 15C? 

 

What about cabinet damping?- I've used R-13 insulation on some other speaker builds, and i've seen material like sonic barrier from Parts Express. Should I cover the top, sides and back in this stuff to help damp the cabinet?

 

Modifying the cabinet size? - Is there any documented benefits to changing the size or shape of the cabinet? 

 

What else should I be considering for this cabinet build? Let me know if there are other documented improvements I should be considering.  

 

I'm less concerned with making an exact replica of Cornwall 1. I'm more focused on making these the best performing speakers that they can be. I'll also be rebuilding the crossovers, and rewiring the speaker as I put it together. 

 

Thank you for any help, guidance, or advice. 

[OO1]

36 minutes ago, Onebean said:

 

 

Thank you for any help, guidance, or advice. 

 keep the same dimensions but use 1 inch  plywood or MDF  as that increases the stiffness , a1 brace is all that is needed  - in the center above the woofer front to the  back  panel ----make no changes --front mount the drivers is easier , route out   about 1/4 inch for the woofer-tweeter -mids for a flush  clean look , damping is needed on the side walls ----rear -and front , but use acoustical foam -    that's it

[Onebean]

1 hour ago, RandyH said:

 keep the same dimensions but use 1 inch  plywood or MDF  as that increases the stiffness , a1 brace is all that is needed  - in the center above the woofer front to the  back  panel ----make no changes --front mount the drivers is easier , route out   about 1/4 inch for the woofer-tweeter -mids for a flush  clean look , damping is needed on the side walls ----rear -and front , but use acoustical foam -    that's it

@RandyH thanks for the reply. I already have 3/4" plywood, and I have some 1/4" too, so I'll laminate them for 1" thick. I assume you maintain internal dimensions for the same internal volume as the original.

 

Flush mounting the horns and woofer is no problem.

 

Is there a design for the a1 brace I can copy?

 

Can you elaborate on the acoustic foam recommendation? Like the Parts Express Sonic Barrier, the Owens Corning stuff used for room treatments, or something else? 

 

Any input on the round versus slot ports?

[Dave A]

Fight plywood warp with Baltic Birch which is superior to regular plywood in every way. The advice you have been getting regarding driver placement. Is it from someone who has actually built that way and liked the results? You have a TON of variables in there and you have to decide what your goal is. A Cornwall, a re-engineered Cornwall or something entirely different. The DIY forum  http://www.hificircuit.com/community/forums/diy-speakers-and-subwoofers.13/  is dedicated to what you seek to do. Now there are plenty of builders here too but you have a really big laundry list of questions.

 

 I think I would start asking around to find examples of what you want to do and go listen first.

[Onebean]

@Dave A thanks for the response. I'll have to do some looking for 1" BB ply. I've never noticed it at the cabinet / wood shops. I agree, I don't want to re-engineer / design a speaker, that's why choose my words carefully, and asked for documented improvements. I'm not looking to mess with success, I'd just hate to hear there was a better design after I completed my build. I live in the middle of nowhere, so auditioning a set of stock Cornwalls is nearly impossible, and auditioning a pair with modifications is completely out of the question. 

 

The port is my biggest concern / question. Is there a round port design that will give identical results tot he slot port? The slot is certainly not impossible, but again, if there is a documented better way, I'd like to have the option. 

 

I did get an opportunity to listen to a new pair of Cornwalls at a high profile dealer while I was on vacation in Southern California last year. They about ripped my head off with some crazy bright tracks cranked up to obscene SPL. By the time I got to select my demo track, the owner was rushing the salesman to meet another client. It wasn't a great experience to say the least, especially since I had called ahead to make sure they had time for me, and drove an hour each way. I guess my rental car wasn't fancy enough to get a real demo. 

 

The reality is, I should stick with the existing design, or roll the dice on the outcome.   

[Dave A]

You stick with the existing design there are things you can do that are reversable or won't alter the cabinet in ways that kill future sale of them if you are reworking an existing set of CW's. I think the vast majority of Klipsch owners move to other Klipsch over time and so resale probably is an important thing to consider in that case. Recapping the crossovers and front to back bracing would be #1 in my book and then I would have a listen. #2 would be tweeter replacement and #3 if those did not make me happy I would move on down the road to a Chorus type or a complete new build.

 

  Of course this is personal opinion based on numerous speakers that have gone through my hands. Others will make different choices due to personal preferences. It is darned hard to find a simple single recognized as best answer to what you want to do and the variations never end. Decide what your goal is first. A pair of really nice sounding CW's with those limitations or a complete new build and live with those limitations + the risk of experimenting. The very best set of speakers I have is from experimenting so if you are willing to gamble the payoff can be huge. I also have a growing speaker graveyard on the ridgetop for things that did not work so well and old speaker cabinets from Klipsch not worth rebuilding.

 

  I am lucky in central Tennessee I can drive to Nashville and get 25mm 4' x 8' BB for $77 a sheet. It is a lot more for that in other places if even available.

  I doubt port shape is critical but port volume in total opening surface area and length is. Now if the port is one of your main questions ask that specifically here and you will get answers from people who can tell you.

[Onebean]

Thank you Dave. I agree on all the items you mentioned.