External LSiM703 crossover modification

blehmbo

I've learned so much from this forum and this is an attempt to contribute a little back, a few photos follow the lengthy write up.

I started planning this project over a year ago and I barely finished about a week ago (life happened). I’ve done internal crossover mods for four other speaker models, but after seeing VR3’s LSiM703 internal mod I decided it would be best to go external due to the capacitor and inductor component count. I decided to fabricate my own enclosure for cost and size flexibility. Fabricating and painting the enclosure took up nearly 90% of my build time since I haven’t worked on a wood project since middle school, this was my first time working with MDF, and I initially did not have all of the tools needed to complete the project the way I wanted it.​ Tools that I acquired to complete this project: router, drill press, bar clamps, 90 degree corner clamps, LCR meter, and 4wire low ohm meter.

Neotech OCC copper in Teflon insulation was used for all wiring. 18ga wire was used inside the crossover enclosures. 16ga wire was used inside the speakers and terminated with gold plated copper fastons/quick disconnects. 4 pole speakon connectors, with litz braided 16ga wire, were used to attach the crossovers to the speakers. Vampire gold plated copper binding posts were used.

Metalized polypropylene capacitors were used all around: Sonicaps in the highs and mids (exception of a larger value Erse cap that was placed in an LCR filter). In the woofer section a Dayton capacitor was used due to size. The woofer capacitor would have been from Erse, but they removed the cap from my order (without notifying me) since they were out of stock of the desired value, and would remain out of stock for a while.

Air core inductors from Erse and Jantzen were used in all positions. Some needed to be unwound to closely match stock values. Care was taken to keep the inductors at 90 degree angles or to keep them distant, in the case of the smallest inductors. Measurements were made with an LCR meter and a low ohm meter.

Run of the mill Mills non-inductive resistors were used all around. One of the resistor leads had a faulty weld and snapped off when it was slightly bent to be in line with the body, the deviation was only 10 degrees or so. The good folks at Sonicraft replaced it free of charge! They said they’ve only heard of it happening one other time.

Crossover components were mounted with zip ties and silicone to a 0.25 inch lacquer coated MDF board. Standoffs were made with cut pieces of half inch oak with brass threaded inserts, threaded with glue. The enclosure was made of 0.5 inch MDF, held together with butt joints and Titebond II. External edges were shaped using a 1/8th inch router bit. Rear panels for the crossover enclosures and speakers were made of 0.25 inch oak panels, A 1/4 inch round over bit was used on the four corners of the panels, the panels were then sprayed with lacquer. Recesses for the panels in the crossover enclosures were created with a 1/2 inch router bit. The lid was secured in a similar way as the crossover board, MDF pieces were glued to the top internal corners with threaded inserts for the lid fastening screws.

The original paint/finish for the enclosures was high gloss black lacquer. The edges were filled with Titebond II and sanded smooth, surfaces coated with multiple layers of Rustoleum filler primer, with sanding in between, resulted in a smooth surface with few imperfections. Rustoleum gloss lacquer in the spray can was then applied with unfavorable results. I was unable to attain a consistent smooth glossy finish throughout using the Rustoleum lacquer. I ended up sanding down to bare wood and just moving to a hammered finish (I become impatient). The hammered finish turned out pretty well. It required very little prep, just a coat of primer and two coats of paint. Surface imperfections and joint seams disappeared, it is to be determined if they will show through when the weather changes.

All screws, nuts, washers, and threaded inserts were non-magnetic (brass and stainless steel).

Since completion they have been burning in with my new amplifier and LSiM706c (it dwarfs the LSiC it replaced, it even dwarfs my LSiM703s). I have a little over 215 hours on the modded LSiM703s now, but I still haven’t done any critical listening yet, but I am definitely happy with what I have heard so far (even prior to the amplifier change). I would have to do a side by side with the stock crossovers for a true comparison.

With stock crossovers flash and no flash photos:



With the lids in place:


The rear speaker panels, sitting in the recesses for the original binding post plates, with my DIY speakon cables are in place:


My cluttered suboptimal set up, excuse the mess. The LSiM706c's cloth bag is under the speaker, for the time being, until I place proper feet:


Without grills:



Next project, new speaker stands sized for the LSiM703s.

drumminman

Nice work - moving the Xovers outboard seems like a nice touch given the size of the speakers and the number of components. I've used the hammered finish paint on a large drum hardware case- that stuff is forgiving and very tough.

EndersShadow

MAN that looks CLEAN! The size difference is by no means subtle lol.

As a though, have you looked if the 706 is wallmountable? If not what plans do you have for feet? I ask because these puppies are fairly cheap and would help you out, though wallmounting would be the better option IMHO.

Mikey081057

nice

Mikey081057

very nice work

gce

Very cool...can't wait to hear your final thoughts after burn in.

F1nut

Beautiful crossover work, well done sir!

If I may, to obtain a proper high gloss finish you have to finish the finish regardless if it's applied from a rattle can or pro spray gun. This involves wet sanding and polishing compounds. The other thing I'd like to mention, never use silicone. The out gases are corrosive as it cures.

blehmbo

Thanks for the feedback folks.

EndersShadow wrote: »

As a though, have you looked if the 706 is wallmountable? If not what plans do you have for feet? I ask because these puppies are fairly cheap and would help you out, though wallmounting would be the better option IMHO.

I was considering just sticking on some regular 3M rubber feet, but the product you listed is interesting. I will look more into it. Do you have experience with their foam isolation pads?

As for wall mounting, I'm sure it can be done with the proper mount, but it lacks mounting holes in the power port backing like the LSiC.

F1nut wrote: »

If I may, to obtain a proper high gloss finish you have to finish the finish regardless if it's applied from a rattle can or pro spray gun. This involves wet sanding and polishing compounds. The other thing I'd like to mention, never use silicone. The out gases are corrosive as it cures.

Thanks for the input. I assumed it should have looked somewhat glossy after four coats, certain areas were and others were dull. I may have been mistaken for assuming it would turn out as smooth as the Deft spray lacquer I used elsewhere, which is a nitrocellulose lacquer. I'll have to do more testing on scrap MDF.

I was concerned about the corrosiveness of the silicone during curing. I did a test on a few of the inductors by applying a thin layer to the side that would mate with the board. I didn't see any discoloration through the clear silicone after 48 hours (cure time is listed as 24, but it still smelled like vinegar). I suppose it's possible that it still could have affected the wiring of the inductors. I wasn't too concerned about the resistors or caps since they have thicker insulation. The crossover boards sat outside of the enclosures for over a month before installation, for ventilation and due to the boxes not being finished.
Is it something I should still be concerned about? I would have went with hot glue, but I wasn't confident that it would be able to hold the heavy inductors over time.

F1nut

I don't know that exact chemical nature of the Rustoleum lacquer, but since it says the valve can be cleaned with mineral spirts, it is not nitrocellulose lacquer. At the same time Deft isn't really nitrocellulose lacquer either as it contains additional chemicals. I hate the smell of that stuff. Whatever the Rustolem is I would say you'd need 10 coats minimum to build up the finish.

As for the silicone, once it has finished gassing out any corrosion concern is gone.

ken brydson

F1nut wrote: »

Once it has finished gassing out any concern is gone.

That's what my wife said...

Moose68Bash

Nice project and well done!

Congratulations!

How do you like the sound?

VR3

Those turned out great!

Good job!

blehmbo

I'm not much for leaving detailed reviews, so I'll keep it short. After having about 350 hours or so on the crossovers and tweaking speaker placement, I finally had some time to sit down and really listen to them. All I will say is, in my far from perfect room, I'm very impressed by the improved detail and soundstage of the modded 703s.

Maybe the next project will be room treatments rather than new speaker stands.

F1nut

I'm thinking you should do the center channel next.

DarqueKnight

Excellent. Thanks for sharing.

asuslover

hello, I know this is an thread , but do you have the values for capacitors and coils?
Maybe the schematic ...Thank you

dromunds

OP hasn’t been active since June 2016

Viking64

dromunds wrote: »

OP hasn’t been active since June 2016

*June 1968

benbvan

Beautiful crossover work. I'm curious, does anyone know if VR3 has a new email, or still doing crossover upgrades? I'm trying to find out if anyone has had great success upgrading 707's.

sgmsmg

Excellent work! Do you plan on keeping the leftover stock parts?
If not I might be interested in some of them.