Category Archives: geeking

Reconing a speaker

geeking, , ,

My son Elliot got some old Carvin speakers. A pair of TRx218N woofers and a pair of TRx153N for a complete 4 way system. The 218’s have no filters so the signal must be filtered before or after amplification.

The speakers in one of the TRx218N were busted : no resistance, while the unit is 4 ohms (two 8 ohms 18 inches speakers in parallel).

According to the website:
The TRx218N is our finest and lightest dual 18-inch subwoofer. The high power, lightweight Neodymium 18-inch woofers feature 4-inch voice coils. Not only does it provide thunderous bass, but the system weighs 22 lbs. less compared to similar ceramic systems.

The TRx218N is the ideal match to the TRx153N for a 4-way system. Stack two TRx115’s, TRx215’s, or TRx153’s side by side on a side stacked pair TRx218’s for 120 degrees of uninterrupted coverage at optimum head level placement.

System Type: Dual 18″ Subwoofer, Bass-Reflex
Speaker: Dual Heavy-Duty Neodymium 18″ Woofers
Dual 4″ voice coils
Power: 1600W Cont. / 3200W Program / 6400W Peak
Recommended Amp Power: 1200W – 2400W
Connections: Two Neutrik™ NL-4 Speakon
Dimensions: 23.5″ high x 40″ wide x 22.75″ deep
Weight: 49.5 kg

Those speakers are expensive. The coils are massive at 4 inch diameter. The neodynium magnet is supposed to be lighter and stronger that regular ferrite magnets.


I removed the dust cap on one of the speakers and found some spaghettis!


I read a bit about how speakers work, using copilot and wikipedia.

After wondering whether to get replacement or repair them I found some reconing kits at https://reconingspeakers.com/products-page/carvin-ne18-8-18-aftermarket-recone-kit/

This company offers a reconing service or parts kits to recone your own speakers.

They offers printable instructions as well as videos to explain the whole process. It’s not difficult but one has to be patient and take their time to get good results.

I checked with them to confirm the parts I was ordering were the correct ones, ordered it online and received it a few days later.

Reconing

The cone and spider (the yellow accordeon disk that holds the coil at the base of the cone) were in good condition but as everything is glued, they recommended replacing everything. After cutting the old cone and spider, and desoldering the wires, I could remove the whole coil assembly and was left with the frame and magnet.

The second step is to put tape over where the coil goes around the magnet to keep the area clean: any debris left at the end would rub against the coil; remove all the old adhesive, clean inside the slit where some old coil may have fallen.

Then the new coil and spider can be glue. The part that I found the most confusing was to find the best position for the coil. It must be set not too high (or it could come off the magnet) and not too low (so it will not bottom out and touch the back of the speaker.) The Speaker Exchange provided some shims of varying thicknesses to put around the magnet while gluing to ensure that when everyting is done the coil can move up and down without touching the sides. The instructions call for adjusting the height looking at the outside of the coil but in my case the coil had windings both inside and outside up to the same height so I found it more practical to slide the spider (it was a tight fit) around the top of the coil and do some dry fit. In the general case, the coil but must set so there is about the same height below the coil than the height of the windings. In my case it was not possible, Gene from the Speaker excahnge explained an alternate way to get a appropriate height. When I was happy about the height of the coil in its resting position, i started gluing. The job requires different glues: contact cement to glue the frame to the spider and the cone, epoxy glue to glue the coil to the spider and cone; some pva glue is also used to glue the dust cover to the cone.

So i put a bead of contact cement on the frame then lowered the spider with the coil already in but not glued and turn it a bit to ensure a good bond. I made sure the wires aligned with the speaker terminals! I followed the instructions but typically contact cement is applied to both surfaces, left to dry then the part and put together and bond on contact; here the glue was applied only on the metal side (like I had learnt in school: put the glue on the side that is the least porous.)

After letting it dry, I dry fitted the cone. it needed a little trimming, maybe a couple mm so it would fit tightly around the top of the coil assembly. Once I was happy with the cone position, I checked again the height of the coil in the magnet (I needed the windings to extend 12 mm from the top plate) and glued the spider to the coil with epoxy glue. After letting it set, checked again the cone, applied contact cement to the top of the frame and put the cone in. The wires from the coil are inside coming out on the cone. I also glued the gasket on top of the edge of the cone so the speakere assembly can be attach ed to the case later. I put some blue masking take and put the speaker upside down over night. The next day I glued the inside of the cone to the coil with epoxy glue.

Almos there. I punctured the cone so the pigtails can penetrate through. Soldered them to the thin wires, solder them on the other side to the speaker terminals with enough slack so the speaker can move in and out but not so much that they could short. Applied a small amount of glue on the wire so it does not move.

Tests

Finally I could remove the shim and test.

I tested with Thievery Corporation Shadow of Ourselves. It had good bass and did not require too high volume to test (I was testing with a hifi Denon high fi amp that worked with 8 ohms) https://open.spotify.com/track/6Yf2RvEtvZbOsXsR4602qn

One of the speakers works fine but the second one was vibrating unpleasantly: the coil seemed to be out of alignment and to rub against one side.

We can see it here: the gap around the magnet is a little larger at the top.

After putting back the shim for a few hours and pulling on the cone on one side to try to get it more centered, the vibration has stopped but I am not sure how long the trick will last. I am considering applying heat with a reflow station, using solvent to reset the spider or cone to the frame (contact cement should come off in acetone, epoxy glue would be much harder to remove chemically but may soften with heat to be adjuste by a mm)

Update: Gene suggested shimming on the side that is too close and add more epoxy glue, He recommended using solvent as a last resort. He also recommended to check there were debris in the gap. As the base of the speaker is vented, stuff could have fallen inside (but also could fall out of it too). I will try with some compressed air.

Conclusion

This is a work in progress. I still need to figure out how to get rid of the vibration on one of the speakers reliably, put the dust cover, put the speakers in the enclosure, configure the low pass filters and test. We got a Carvin X-Drive and we still need to figure out how to use. As it’s rather ancient, it may need some convincing to be able to run the setup software on windows 10!

18 inch speakers are not cheap. This kind of power handling with neodynium magnets and large coils are not very common. Replacement from unknown sources are selling around $230 so reconing can make sense. The speaker exchange proved to be a great friendly source. They have been very helpful along the process to figure out how high to set the coil in this unusual driver. The experience was very refreshing compared to the usual Chinese sellers on ebay or Amazon who don’t care or are willing but unable to help due to the language barrier.

Negative scanning

geeking,

In a previous post I wrote about going back to black and white film; i got a new old film camera, shot a few rolls of Ilford HP5+ and processed them.
A crude way to get a better idea of the photo i learned when i was spending lots of time in the darkroom is to look at the negative from the emulsion side at an angle so the silver halides are mat and the rest of the film is shiny and you can kind of see a positive image.
Without a darkroom, my options are to bring them to a lab to print or to scan them and handle them as digital files.

There’s an app for that

My first attempt was to take a picture of the negative with my phone and to use an app to reverse the black to white. It proved difficult to find a correct opaque background and be perfectly horizontal to the film so the result, although it allows to see the image better, is not usable for anything else.

Film scanner

I had a film scanner a long time ago. A Minolta dual scan. it uses a scsi adapter with a DB 25 connector. Modern computers do not have scsi, and the scanner has a 220 V AC power input, also it scans at 2700 dpi one exposure at a time, 3 in one direction, then one needs to flip it to do the other 3. So i was on the market for a new film scanner. I had used a plustek in the past but I found that people were reporting good results with epson V series scanners. After an unsuccessful attempt to buy one on amazon (scanner arrived damaged with missing accessories and no power adapter so i could not confirm it worked) i found another one on ebay for $80. Note that shipping can break the deal on these as many listing read $40 or more for shipping costs.
The scanner I got is an Epson V500. Physical resolution is 9600×9600 dpi so at highest resolution it would output a 13,606 x 9,070 pixel bitmap from a 35 mm exposure (24x36mm). It also has dust removal, and Digital ICE (infra red channel to remove scratches; I don’t think it can work on black and white film though). It comes with holders for 35 and 6 x 6 cm negative and one can find other formats or alternate ways to hold the negative on ebay (some of them 3d printed). It seems they use a series of holes on the holder so the scanner software can recognize which holder is being used.
Epson driver scanning software in available on Epson’s website and works well with windows 10 64 bits. With the proper film holder, the scanner can convert 12 exposures unsupervised, each cropped, rotated (you need to select than manually but all before starting the scan) and exposure-adjusted. I scanned at 4800 dpi as it seems sufficient based on the size of the silver grains and going to 9600 would produce really big files and would take a really long time to perform.

I had to cut the film is strips of 6 so I had to get some binder negative sheets. To make a contact sheet, I used ACDSee that can easily compose all the images in a grid and put the file name (which is the exposure number) below. It does not show the film spockets but is perfectly usable.

Next step

I have read mixed reviews of VueScan vs Epson scanning tool for the Epson V500.
I may try a demo version to see which I prefer.
I will also spend time on Paint.NET, photoshop and lightroom.

Back to Black and white photography

geeking

Twenty years ago, I was doing a lot of photography with Nikon cameras and was spending a lot of time in the dark room.

Then I got married, had kids etc. Around 2000, I moved to digital and got an Olympus E-10, an SLR (it used a semi transparent mirror so it could take a picture while the view finder was still usable.) then went back to nikon cameras, this time digital, first DX, then FX.

Because of the lack of time and darkroom, I gave up black and white photography and my equipment sat quietly in a box in the basement. I gave my film camera (Nikon F70) to a cousin and kept my other older cameras: Nikon FA and FG and abunch of older lenses. I had a few rolls of film that I forgot to put in the fridge or freezer that are now 20 years old (I read somewhere that i should expose 1 stop extra for every 10 years), some chemicals that are probably not very effective anymore either and some 25 years old paper that is probably also going to be very slow now.

At the end of last year I found that I could get an F4 on ebay for fairly cheap (around $130) and over Christmas I shot 3 films.

Let me tell you how it went, what I used, the results and what I am going to do next.

Getting ready

So, I had most of the equipment but I needed some film and chemicals.

Film: I got a 100 ft roll of HP5+. it’s Ilford film rated at 400 that I have used a lot in the past. Nothing fancy but I could compare to past results. I also got 10 empty cassettes ( $1.25 each). I could have just purchased 36 exposure rolls but i though if I am serious about it, I will save money soon going this way. A 36 exposure roll is about $7, 100 ft was $75 and I should be able to do a lot more than 10 rolls and also, it allows me to make shorter rolls if I want. I also had to get a black bag to roll the films ($12 amazon). I did not bother with a daylight loader.

Chemistry:  I had some old chemicals leftover: almost a gallon of fixer but it felt gritty, a bottle of ilfosol S and some old tetanal developer as well as a box of emofin, a 2 stage powder developer. I had a bottle of kodak stop bath; i think i got this one on craigslist about 20 years ago. I assumed it does not go bad.
I wanted to start fresh so I got a pint of ilfosol 3 (film developer $10) and some rapid fixer (liquid concentrate. 1 liter $10), a couple of empty liter size bottles ($4 each). I got it from BH as amazon or ebay shipping costs were horrendous for these chemicals.

Other equipment: I already had a 300 ml graduate, a film squeegee, a thermometer and a developing tank.

Rolling the films

I started by rolling a few films. I bought new cassettes as I was not sure the 20 year old felt would still be light tight. I used to roll film in a dark room; rolling them in a black bag is very possible but it was a little cramped and difficult to measure. I taped the film to the spool and rolled until I thought i had a reasonable length. It ended up being about 22 frames on the first roll. I am not packing it a little more.

Exposing the film

I loaded the F4 and the FA with some HP5+ and shot family and landscape in the sequoia national forest over christmas. For some reason my Yongnuo flash was not recognized by the camera. Shooting at 400 (without Auto-sensitivty) takes some getting used to. I used a 50 mm f/1.4 and a 28-70 f/2.8 lenses. I had not taped the first film enough and in the FA, i wound it too hard, so I had to take the film out from the camera in the black bag.

Development

Back home I processed the films.
I found the technical notes for the dev and fix on ilford’s website.
In the black bag, I cut the end of the film, loaded it on the developing reel, put the second empty reel on top and closed the tank.
Mixed rapid fixed 1+4 (60 ml +240 ml water) and put it in a bottle.
Mixed stop (label reads 16 ml per liter. i used a teaspoon per 300 ml.
Prepared ilfosol s at 1+14: 20ml developer+ 280 ml water at 20c. the developer will not be reused so i mix it last and leave it in the graduate.
Poured dev in tank and start counting 11 minutes. 4 inversions during the first 10 sec of each minute followed by a tap to get rid of bubbles.
At 10’50 mark started draining dev in sink, poured stop, shake, pour stop back into its bottle
Add the end of the film that had been cut from the roll in the opening of the tank to check fix action; poured fix and same 4 inversions in first 10 seconds of each minute for 2 minutes only. Checked that the piece of film is clear after the first minute.
Poured fix back to bottle, rinse with water. rotate 5 times, replace water, rotate 10 times, replace water, rotate 20 times. Added a drop of wetting agent, and water, final rinse and finally open the tank and breathe.
Ran wet squeegee over the film, and put it to dry in the shower with a cloth pin at the top and at the bottom (as a weight)
Wash and dry everything.
Look at the film from the underside at an angle to see it in positive.
Repeat with the other films. For the other two films, i got more daring and processed them together (so I had to make 600 ml total of stop and fix)

Scanning

The film is now waiting to be scanned. I tried to take a photo of the negative with my cell phone and use a negative filter. the quality is clearly not there. I have ordered an Epson V500 scanner. I bought an olympus film scanner 25 years ago but it uses an SCSI interface and i don’t have the computer i used then nor the SCSI adapters or drivers. The Epson flat bed scanner has a led lit back and scans at 6400 dpi which should work fine.
I will update this post when I have had time to scan the film and will post some pictures.

 

Conclusing

Getting back to black and white was fun and brought many fond memories.

Taking the photos required a slower process than using a phone or even a DSLR as you only have so many exposures per roll. The F4 can do something like 5.7 frames per second, so the film would last 5 seconds. The FA does not have a motor. I used them in P mode most of the time; I want to try the S (speed) and A (aperture) modes. I also scored a Nikon FM on ebay for $40. The meter does not work but i think i can fix it, and the FM has a mechanical curtain so it can still work with no battery.

Processing the film was as I remembered it. Quiet alone time, when one has to pay attention to not miss any step or miscount the processing time. Seeing the processed film for the first time is still a great feeling.

I am not sure if it will be happy with scanning and printing the photos as a digital file or if I will want to convert the basement into a darkroom (or if my wife will let me.) There is a great lab not far from home that does black and white printing. There is also a camera store that has a darkroom one can rent by the hour. The question is will I have time to do it.

To be continued…