Questions on my John Krutke Seas L18/27TBFCG Project

[Ray Collins]

I am building the L18/27TBFCG Seas speakers that John Krutke designed and I have a few questions. This is my first build using a crossover--I have built a BIB 168EZ, Fonken 127 and a pair of Rythmik 15" subs.

Questions are:
1. I have a 2.25 mH steel core inductor from Madisound but the specs call for a 2.20 mH. Do I need to purchase an LCR meter to unwind it to specs?

2. When mounting the above inductor to the circuit board can I use steel nuts and bolts or should they be brass/non-ferrous?

3. How do I attach the crossover board to the inside of the enclosure...epoxy, velcro, screws that don't penetrate the outer wall or?? Do I use buttons or small pucks at the corners as standoff spacers--the back of the board has buss wire exposed.

4. I didn't purchase the port from Partsexpress that John recommends since it would be a single item order. I intend to use 1 1/2" PVC water pipe instead and use my 3/4" roundover bit to provide the needed flair where it exits the back of the box. I also intend to build a flare collar out of 3/4" stock to glue to the end inside the box.

That is all I can think of at the moment. The boxes are complete. The baffles will get the roundover treatment and have the driver holes cut tomorrow afternnoon.

Your input will be greatly appreciated.

John's build site is http://www.zaphaudio.com/audio-speaker17.html

Ray Collins

[peter_m]

Just curious, did you consider the SR-71 design? If so, what made you pic th L18?

1) If you were to keep your inductor as is, it will be off by 2.3%. That is generally not much. To give you some perspective, I've ordered a bunch of Solen air inductors and they all exceeded the label's value by 5-6%...

2) A hot glue gun is another option.

3) What ever works without ratling. I like hot glue gun as it can be removed if careful and it is very strong. Just choose the high temperature as it is stronger then the regular.

4) Have you considered finding some kinds of flange or adapter simply glued to the PVC tube and then router the plastic to make a flares?


Good luck,
Peter

[JonP]

Guess being up this late gives me first crack..

2.2 and 2.25mH... that's less than 3% difference, and probably too small to matter.

Steel nuts and bolts normally would be something to worry about near or especially thru an air core inductor (adds a bit of 'iron' to the core) but it might not be an issue with the iron core. I'd go with non-ferrous hardware anyway, just to be sure.

The mounting, you can go a variety of ways, main thing is a solid method. I did a temporary setup with screws into the box, tightening my pegboard masonite crossover boards down into the Whispermat foam on the walls. The screws would unwind from vibration. Even on my temporary front baffle with screws mounting from the inside... I found some of them loosening over a week or so... I'd go for something solid, like posts or standoffs, locked with epoxy to the cab side or bottom, with small bolts or screws going into them, and also wet with epoxy or other locking agent.

Look at the link page in the first page sticky links... find Bob Collo's subwoofer page and flare info.. great site with his calculators, and different flare construction ideas, including heating PVC pipe to flare it on a mold! Unless you're really moving air, the 3/4" roundover should be enough to do the job, though. Try to get most of the depth of the bit, maybe glue on a square of material to the inside of the back baffle to provide greater depth. I think the Precision Port (I used a 2" recently) radius is bigger, about 1-1.25".

Hope all that helps... good luck on the project, and post some pics!

[---k---]

Like others have said,

1) less than 5%, don't worry about it.
2) use zip ties and hot glue. drill a couple holes in the board and loop the zip tie through.
3) industrial strength velcro works great. if you can use velco and zip ties, it would be even better. you don't want to use anything that would prevent you from getting them out at some later date.
4) will work. bigger flares are better to prevent noise from the port, but you're likely won't notice. you may need to adjust the length a hair.

[servicetech]

Most people won't hear a 20% difference in component tolerance w/o doing A/B instant switch testing. Less than 5% will barely show on test equipment.

[Ray Collins]

Thanks fellows; I think I have a grip on it...for now.

Ray

Servicetech,
Guess I won't need that LCR after all...

[Licinius]

Those 3m command strip things work well, they're like velcro, but plastic and the same on both sides, so they just kind of click together, without the annoying tearing and wobbling of velcro...

http://rvtravel.com/blog/rvnow/uploaded_images/command-strips-740460.jpg

They've held an 18x24 poster mounted on 1/2 mdf to my wall for two years, so they're probably strong enough =)

[Ray Collins]

Licinius,
Thanks, I will check it out...it may be just the "ticket".

Another question for the group:
Should I attach the crossover to the wall of the enclosure and cut an opening in the Sonic barrier to accommodate it?

OR

Should I install the Sonic barrier and attach the crossover to it?

Ray

[---k---]

You're going to have a hard time getting the croosovers to mount to the Sonic barrier. You're going to need wood standoffs. This is how I did it in the Khans:

Works real well. More lining the better.

But if it is a small box, you may not have this luxury and have to attach the crossover to the sides of the box. Won't hurt too much. You can always add some poly fill to the box too.

[Ray Collins]

Ryan,
Thanks, you have given me several usefull ideas.

Ray

[Ray Collins]

My plumber is going to drop off some scrap 1.5" PVC pipe for me to use as the ports. Can I cut this to length with my friend's compound sliding miter saw? It has a new 96 tooth Freud blade($$) and I certainly don't want to damage it.

John's port is 1.6" in diameter with a length of 4.4". He suggested using WinISD to calculate the new port length if a different diameter is used. Since I am using a 1.5" tube I did and got a length of 4.26". Since he measured his port tube end-to-end including flares I thought I would do the same--with a 3/4" flare on each end produced with my router. Sound reasonable (pun intended)?

Ray

[Dennis H]

Sure, the saw will cut PVC just fine.

[servicetech]

Power miter saws are "the bomb" when cutting PVC pipe. IMHO it's the only way to get a straight clean cut.

[ThomasW]

Just be prepared for the fact that the PVC 'sawdust' has the opposite electrical charge of everything else on the planet.....This means it sticks to everything...

[Ray Collins]

Sort of like packing peanuts, eh!?

Any comments on my port tube?

Ray

[peter_m]

Make it the same as your STARBOARD tube! 8O

[Ray Collins]

Ahoy and thanks Peter_m...

Ray

[Ray Collins]

Well there is progress and a problem.

First the good news:
The boxes are complete and the crossovers mounted. The birch exterior is finished in cherry stain with a coat of wipe-on poly. All appears solid with tlhe sonicbarrier called for in the Zaph's plans lining the boxes. The baffles are MDF and have a 3/4" roundover. All driver holes rebated as required. The mouth of the box and the back baffle edges are rabbeted...nice snug dry fit...but the baffle has not been mounted yet...

The bad news:
I put a sealer coat on the MDF baffles using shellac. The next day I sprayed 5 coats of oil based primer purchased from HD(behr brand). The following day(today)I tried sanding to begin the leveling process and the primer just rolled up into little balls. I specifically requested sandable primer. I tried wet sanding with better results but they were pathetic at best.

My plan is to pick up some sandable primer at an automotive paint store and try that. I hope it will work over what I have created.

Any experience with this MESS?!

Ray

[Dennis H]

Yikes. Sounds like, for whatever reason, the primer didn't stick to the shellac. If that's the case, adding more stuff over what you have probably won't work. Bummer.

[Ray Collins]

Dennis,
Yes, it is a pretty crummy deal. The primer is not separating from the shellac; rather, it is "pilling"...just rolling up into little balls. It may be that it has not completely hardened. I will give it a couple of days and see if it sorts out--if not I guess I will use a stripper or lacquer thinner to remove it. Everything else is ready to go...

Ray

[Finleyville]

Ray,

I am sorry you are having problems with the finishing. We all know that how a speaker sounds is the most important part. But the final finishing is almost as important. It can be a real bugger to get a creation to look great let alone exactly how one envisions it. Good luck with this step. I cannot wait to hear how you enjoy this fantastic design of a speaker. They put a smile on my face every time I just think about them let alone actually listen to them.

[Jeff G]

Do you know if the shellac is waxed or is wax free? adhesion could be an issue with a waxed shellac.

[Ray Collins]

Thanks for the replies fellows...I am about ready to clamp the baffles on and give a listen regardless of the appearance.

Jeff G: The shellac is not wax free but the primer is not de-laminating from it; the primer is just pilling,i.e.,rolling into little balls as though it is a non-sandable primer. I am giving it a few more days to dry/harden and hopefully I can level it and switch to a different (?) primer.

The primer situation has me confused even after reading several different posts on painting. What do most of you use? A one part primer for wood or one of the two part primers for autos? Lacker primer, water based primer(MDF doesn't like this but my baffles are now sealed), one of the "...thane" sisters...??

Ray

[Ray Collins]

I tried a new two part primer today. It is from PPG Auto Paint and seemed to work well. The day was so damp that the normal flash time was significantly extended. I sanded with wet/dry very lightly and it shows promise. The boogers were almost fully covered with the second coat. I will try leveling it tomorrow and MAYBE get the base coat on. The gun is a cheap loaner from Harbor freight...it is a touch-up gun with a very small cup but it works...

Ray

[Ray Collins]

This is a picture of the bottom of my crossover and also my first picture post. Hope both of them work!?

Ray

Yikes!!! It worked!!

Here is a picture of the tops of the crossovers and the homebrew ports.

I am still struggeling with the finish on the baffles. I have tried yet another primer and it seems to be working. I put three light coats of black on this morning and no wrinkles. I will know when I get home.

[Ray Collins]

These are the problematic baffles and a picture of the back of the enclosures.

Ray

[JonP]

These are the problematic baffles and a picture of the back of the enclosures.

Ray

Looking good Ray...

Missed the whole primer problem. Sounds like the coats didn't have enough drying time between layers, so trapped solvent inside and a soft coat. Waiting it out a week probably would have worked. It's always tempting to charge on to the next stage, and frustrating when somthing like this slows you down.

Seems like you've got it under control now.

[Ray Collins]

Hi JonP,
I tried a third primer with the same results--wrinkles. Saturday I finally stripped the baffles down to the MDF and started over. During the stripping process I noticed that the first primer coat was soft--it appears you are correct. I primed everything Sunday and it seems to be fine. Primer instructions said to wait 6 hours before sanding so I should be able to tell this afternoon when I sand and paint them if all is well. I am PAST ready to hear these!

A little better picture of one crossover and the inside of an enclosure.

Ray

[Ray Collins]

Finally Finished!

Well I finally finished these Saturday. I struggled painting the baffles to the point of being a cliche'....I learned by making every mistake possible and then a few. Time is your friend...just leave them alone a little longer than you think you should and most of the problems don't occur. Oh well.

The results are very rewarding...by far the best per dollar speaker I have heard. Smooth and effortless with plenty of bass; however, when John Krutke says don't place them against the wall he means it. Best results are obtained with them about 2 1/2 feet from the back wall. I stuffed a sock in each port and really tightened up the bass but lost the robust bottom end. Everything is a compromise.

Sorry about the crummy pictures. I took them instead of waiting for my wife to do it.

[owdi]

The results are very rewarding...by far the best per dollar speaker I have heard. Smooth and effortless with plenty of bass; however, when John Krutke says don't place them against the wall he means it. Best results are obtained with them about 2 1/2 feet from the back wall. I stuffed a sock in each port and really tightened up the bass but lost the robust bottom end. Everything is a compromise.

Funny, I stuffed socks into the ports of mine just this last weekend :-) On top of that, we have the same TV. You have great taste!

In my living room, my Zaph Audio L18/27TBFC/G measure about +3db between 40 and 70hz. I have them 2 feet from the back wall, and the tuning is a little high, since I haven't finished the ports. Stuffing socks into the ports allowed me to raise the level on the subwoofer without making the midbass overpowering. Works fine for everyday HT, and I pull them out and apart for music.

Dan

[Ray Collins]

Hi Dan,
Post a picture of your build if convenient. I don't understand your statement "since I haven't finished the ports"; could you explane please?

The plasma is great; it replaced a 25" 1985 Mitsubishi CRT--a little overdue?! What are you using for a center and surrounds in your HT?

My perception of their best attribute is low distortion; I listened to them for five hours Sunday afternoon with no fatigue. Impressive assembly of parts--definately the whole is greater than the sum of the parts...

Ray

[Dave Bullet]

Congrats Ray and thanks for posting the pictures. They look great.

Nice to see another one roll off the production line as they say. Assuming you have a better half - hope she now appreciates all those hours in the workshop.

Now only if I could get all these jobs around the house done.. and start my Seas all metal 3 ways .....

[Ray Collins]

Thanks Dave. Please start a thread with your build; I also am very interested in a Seas all metal three way since these turned out so well. I may pick another John Krutke design; however, I need to do a 5.1 HT build and the Statements have been well received. Who knows...this has become addictive!

One more stab at a decent picture. Oh well...
My wife is the photographer but she is playing in our Ladies Golf Club Championship. Maybe tomorrow after it ends she can give a try.

[phisch]

Very nice looking. Great job Ray!

[Ray Collins]

Thanks Phisch.
Well, my wife finished the golf tournament (third place) and took a couple of pictures for me. A little better but still doesn't show the detail I had hoped to get.

[Ray Collins]

End of a Sad Tale

I am reluctant to post this but thought it might help others so here goes. On January 5th while building these speakers I severely damaged my right hand. I was cutting a rabbet on the edge of my baffle when a kickback occured. The saw threw the piece of 3/4" plywood I was cutting back across my palm at the base of my thumb. The wood cut the tendon and both nerves and almost severed my thumb. The surgeon was able to repair the damage but I will regain only 50% of the feeling and hopefully 100% of the use. The physical therapy is very painful and arduous. Please be careful...

[chubby chaser]

:cry:
Ray I am reallly sorry to read/see you have injured yourself. Your surgeon did a good job stitching you back up. I can see you really had a jagged gouge. I was the saftey manager for a 55 gallon steel drum manufacturer for years. Ive seen allot of that type of injury unfortunately. I hope this doesnt slow your speaker building down to much. Ill spare you smart comments and just say safety pays.
By the way you did a good job on your build. I enjoyed the postings. thanks

[Dave Bullet]

Gee Ray, I'm amazed you got the speakers finished... well I suppose it's sort of like falling off a horse (only this one was a saw horse ) - you just have to get back on.

I hope you are making recovery progress as you had hoped. At least you have something very nice to listen to whilst your thumb recuperates between physical therapy sessions.

On a much lighter note... you know my 3 way all metal Seas design? - we'll most of it went up in smoke when I did something silly to my laptop. I've got some xo models on my old measurement Win98SE machine, but the lovely Google Sketchup models have all gone.. Ah well, I can only improve the design redoing them, right?

Take care,
David.

[jkrutke]

Hi Ray, great job on the speakers, they look nice. I noticed the woofer is now $86 and the tweeter is $40. I think they were $65 and $30 when I originally posted that design. I still like them and both have remained consistent all these years, but the price hurts a bit and has inched out of the value category.

My regrets on the injury. With all the speakers I've built, I'm lucky enough to not have a major injury like that.

[Ray Collins]

Chubby,
Safety is the most important element in using power tools and, in my opinion, knowledge is its foundation. I am self taught...

Dave,
I am fortunate to have a good friend who let me use his shop and did the balance of the cutting for me. I am also fortunate to still have my thumb!
Sorry about your data loss on the seas 3 way--I assure you, based on my new two way all metal Seas, you will LIKE them when you finish!! Keep us posted on your re-do progress.

John,
I assure you the extra $31 was forgotten the instant the speakers began to play. Don't be too hard on yourself regarding value; the bang-for-the-buck factor is still incredible....they outplay my LS3/5A's which I sold for $1300 to an audophile in Hong Kong. Glad he didn't hear these first.


Stay Safe everyone,

Ray