Renovation & Restoration

Most Carlsson speakers are a pleasure to restore. Most aspects of the speakers are well designed and the choice of materials is often first-class. Each one of the models has its own unique characteristic that will be addressed under its own headline on the main page. Most of the hints however applies to all models or series:

Rubber parts
Internal wiring




Boxes / cabinets
Always start the restoration of a Carlssonspeaker by cleaning the cabinet thoroughly. Vacuum the speakers both outside and inside. Wash the speaker, use a mild detergent or soap the first round. Dry off the speaker. If you need stronger agents we normally recommend using an ethanol-based solvent. After the cleaning let the cabinets dry out. Should this cleaning not be sufficient you might need to use white spirit. Veneered enclosures On the veneer white spirit makes the fibres stand on end. Afterwards they need to be sanded lightly with a very fine (000) paper. Colourstains etc is to be scraped of with a dull knife in the direction of the fibres. Smaller damages to the veneer can be repaired with a ”marker pen” of the right colour. Bigger damages to be repaired with wood-filler.

Ordinary scratches are normally filled in in the following step. During this step small scratches are to be filled in. The veneer shall be treated with oil in very thin layers, preferably three treatments with at least 24 hours between each. Use a rag only, no brush. Always wipe of excessive oil immediately. Wipe of the veneer once more after approximately one hour or so. The best result will be obtained from using wood oil, a mixture from equal parts of cold-pressed linseed oil and vegetable turpentine, this smells a lot, so see to that you have good ventilation or do it outdoors. In between each application of oil restore the other parts of the speakers. When the veneer is too badly damaged there is one more option to get a good result. Paint the veneer with a watered down / diluted black paint and suddenly you have changed the speakers to original black ash.

Painted enclosures shall be cleaned in the same way as veneered enclosures. However if they are damaged they are more difficult to restore. Sometimes the only way to get a good result is to have them re-painted. One option is to use a cleaner for carpaint. Damages to the paint are repaired by sanding down the edges around the damage before applying touch-up paint in the right colour. Avoid the use of coloured ink that has a tendency to shine through for years to come. After a good paint-repair the application of carwax might give a good shine. Alternately use polish for furniture.

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The baffles (where the speakers are mounted) are most sensitive and the speaker-cones hardly can take any cleaning at all. If the cones are ”sticky” it might be necessary with a light spray of water mixed with soap or detergent, just enough so that the cone darkens a bit. Afterwards wipe it of CAREFULLY using a Q-tip or a soft fibre cloth. When dust is the only problem vacuum the cones using the lowest power of the vacumcleaner and the softest brush. A perforated cone equals a destroyed speaker.

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The renowned fullrangespeaker from Philips, 9710 is used in all Carlsson speakers from the fifties- sixties- and into the seventies in the Mk II editions of OA4/5/6. The 9710 with its high-quality AlNiCo-magnet a sturdy and for its time a truly wellsounding speaker that sounds best upwardsfiring or in some other way directed away from the listening-position, otherwise it might sound a bit obtrusive. The number one weakness of the speaker is the surround that after decades of use often is totally worn-out. The speaker then must re-edged or scrapped. If the suspension is good vigour enough you can help the speaker to a new life with a few small actions.

Start by removing the speaker from the enclosure. DO NOT touch the screws outside the speaker-rim, these are fixing the acoustic-damping device behind the mid-bass woofers. This acoustic damping device has been impedance adjusted at the Sonab factory to give each speaker correct bass-reproduction and the correct transient response. Just unscrew the four screws going through the rubber suspension into the speaker perimeter. Hold the screwdriver tightly so that you don’t slip and perforate the speaker thus destroying it. Cut or de-solder the cables away after marking plus and minus (red or blue cable is plus). Untie the knots on the cloth around the speaker, remove the cloth and wash it.

Vacuum the speaker very carefully all around using the softest brush. Be very careful with the pleated surround. This is a very sensitive part on the 9710. When the speaker is held to the light you can see light shining through the paper surround as through a veil. Gently brush away all the dust gathered between the two cones. If cones are ”sticky” it might be necessary with a light spray of water mixed with soap or detergent, just enough so that the cone darkens a bit. Afterwards wipe it of CAREFULLY using a Q-tip or a soft fibre cloth. Avoid doing this if it’s not absolutely necessary.

Are the papersurround damaged? A possible way to fix this is to paste some small pieces of rice paper on the backside. This has to be done with glue that remains flexible after setting. Measure the DC resistance of the speaker. It should be approximately 5 – 6 Ohms on this 8 Ohms speaker. Use the fingers of both hands to test the suspension of speaker. Do not touch the surround at all when you do this. If the suspension is vigorous and gives some resistance when the suspension is tested the speaker can be restored. If the cone is wobbly and gives little or no resistance the speaker needs to be re-coned or replaced.

Vigorous speakers without larger defects can be restored by the use of coating. Use the water-soluble type that does not become stiff. (Carlssonplanet has today no knowledge about retailers for coating, if you do, please let us know). Should you not be able to find any you can use the type of solution used for repairing flats on bicycles. Use a very soft brush with short hairs. Carefully apply coating or solution around the pleated paper surround, from the cork-gasket onto the very top of the cone, covering every part of the pleated surround. Inspect the surround and see to that there are no holes left not even holes in the size of a needle-tip. To inspect the surround, hold it to a strong lamp and look through the surround. You shall be able to see the light but it shall be hazed. If you can see white light shining through then some part has been missed. The coating shall, if it’s correctly applied, cover every small perforation of the paper. Too thick coating makes the cone heavy and the sound reproduction is heavily reduced. After coating the cone will remain useable over the foreseeable future. Those that have seen a woofer from OA6-MkI from the sixties know what we mean! After this you have a good fullrange 9710 and you can see that the coating has many advantages. The stickiness of the pleated surround supports and helps the cone move in the voice coil gap as it once did when the speaker was new.

If the 9710 shall be used as a woofer in an OA6-MkII it might need an extra modification to be able to do the job. Coat the entire cone and the wizzer-cone with water-soluble coating (we have used ”Visaton”). This results in a tighter and drier bass-reproduction.

A last desperate solution to save a 9710 with destroyed surround is to fit in a foam-surround on the speaker. Before you do this check that the spider is OK. We have done this with good result but it is not an easy thing to do, as you can not cut away the dustcap on the 9710. When fitting foam surrounds on the 9710 you should start by cutting the old surround away using a pair of scissors. DO NOT cut away all of the surround, leave four small parts, approximately a centimetre or two, of the old surround in place in the four directions left, right, up and down. The purpose of leaving these is to keep the voice-coil centred during the whole process. After this fit the new surrounds with water-soluble glue. When the glue of the new surround is completely hardened use a pair of scissors to cut away the remaining parts of the old surround from the backside. If you are not comfortable with this seek help from Carlssonplanet. The 9710 is no longer in production. CarlssonPlanet and the Stig Carlsson trust has so far not been able to find a replacement for the 9710, we would very much like to see a new production-run.

6,5 and 7 INCH WOOFERS
The Peerless SC165 (6.5 inch) speaker is used as woofer or midrange unit in the models from the seventies (OD11, OA12, OA14, OA116 and OA2212). They are also used in the OA50 and OA50.2 The speakers from the seventies and eighties are by this time defect from foam-rot. It is possible that they look OK but the surrounds are dried-out. The aged surround does not give the cone the needed support resulting in problems with the air gap in the voice-coil. DO NOT USE OLD DAMAGED SPEAKER UNITS. This may result in one of two problems. 1. The voice-coil gets stuck in the airgap resulting in a totally destroyed speaker. 2. You destroy the amplifier

There are four different models of the 8 ohm SC165 speaker:

Mk I (1973 – 75)
It has an AlNiCo magnet and paper cone with foamsurround. There is a Sonab logo on the dustcap. There are no more markings than the serial number on the magnet and info about the impedance. Available in 5.3, 8 and 16 ohms.

Mk II (1975 – 78)
The only difference compared to Mk I is that Mk II uses a Ferrite magnet. There is no distinct audible difference between Mk I and Mk II. Available in 5.3, 8 and 16 ohms.

Mk III (1983 – 89)
Improved speaker with ferrite magnet. No Sonab logo on the dustcap. Dustcap made from textile. Marked with Peerless labels indicating the model, date for quality inspection and impedance. Mk III is somewhat ”softer” in its sound probably due to the textile dustcap. It may appear a little ”slower” and less responsive to transitions. Only available in 8 ohms.

Mk IV/B65oa (1996-)
This is the best model of SC165/b650a. It has a rubber surround and a short circuiting ring The cone is coated with a darker coating compared to its predecessors. The dustcap is textile and it has a Peerless label on the magnet.

Note: Some old replacement speakers for the 5,3 ohms woofer have been known to have an incorrect impedance, 7 instead of 5,3 ohms, check before purchase. If this element shall be used the filter has to be modified. The coil in series with the bass driver needs to have lower resistance by approximately one ohm. The speaker named “W65oa” is absolutely correct and can be used without modifications to the filter. Sometimes 2nd hand speakers are available from Carlsson planet. If so these are with new surround and tested. Please contact [email protected]

Two models have been used in the OA-51 and OA-52 over the years. Both types are at present in production.

18W8542 (OA-51 and OA-52)
With paper cone and foam surround.

18W8545 (OA-51.2/3 and OA-52.2/3)
With carbon fibre/paper cone and rubber surround.

Both models are at present available on the market. If you have speakers with ”foam-rot” you should consider upgrading the speakers to the latest standard. It is also OK to replace the 18W8542 with the newer 18W8545 without changing the filter?

New speaker-elements can be purchased through: The Carlsson factory in Skillingaryd, Sweden: John Larsen HiFi +46 370-70 900 or http/

Always start with checking the DC resistance on the speakers. Before measuring remember to disconnect one lead. The resistance reading should be the specified impedance minus 10-20% i.e. for an eight ohms speaker you should have reading in the region of 6,4 – 7,2 ohms. If they have this reading you might consider restoring them. Check with Carlsson planet for advice or assistance.

The Peerless cone-tweeter MT20HFC is almost always OK on the speakers from the fifties, sixties and seventies. The cheapest solution is to keep the original tweeters. They are however not by today’s standard wellsounding. In their time they were amongst the best but compared to the best tweeters today they have a tangible distortion that pushes a surge of noise in front of the reproduced sound. If You keep the original tweeter first check that the DC resistance is OK. The DC resistance should be roughly the specified impedance minus 10 – 20%. I.e. an 8 ohms speaker should read something like 6,4 – 7,2 ohms. If this is not the case the tweeter is not OK.

The cones are often very dusty and sometimes sticky. The cones are very delicate and can hardly take any cleaning at all. Sometimes however the cone is so dirty that it has to be cleaned. When doing this just give one light spray of a mild detergent mixed with water, just enough so that the cone gets a bit darker. After that wipe off the cone with a Q-tip or a fibre-cloth, be very gentle. If there is only some dust on the speaker vacuum the cone gently using the lowest power setting and a soft brush.

If you really want your Carlssonspeakers, which are designed with the MT20HFC to give their best, you should think about up-grading them with new tweeters. The Peerless CT 62 is an excellent replacement with only a fraction of the distortion of the old tweeter. The CT62 is almost a direct replacement, no modification to the crossover is necessary but the physical dimensions are not exactly the same. PROS:
1. They fit under the grill of all Carlssonspeakers using the MT20HFC 2. The have a very clear and distinct sound that transforms old Carlssonspeakers to the most realistic reproducers of music (If you also have seen to the woofers) 3. They are available in the specified impedances 8 and 16 Ohms. 4. They are cheap! CONS:
They are a bit cumbersome to install, as they are slightly bigger than the old tweeter. They are 61mm instead of 50; they have another type of magnet and do not have a square front. Therefore they are not easy to mount ”standing” on the baffle. It is also impossible to use the old bracket from the MT20HFC.

Prior to installation of the CT62 remove the blue and white sticker on backside of the tweeter. The glue tends to dissolve the adhesive on the sticker and the tweeter might come loose. Depending on the model there are three possible ways to install the tweeter.

Get brackets, bend them to the correct angle and screw the to the baffle in the original places (alternately in the ”Y-configuration). Drill holes in the brackets and the baffle for fixating the tweeters. This will later prevent the tweeters from twisting due to strong magnets. Hold the tweeter in place and mark on the baffle where the front will meet the baffle. Remove the tweeter and cut a groove in the baffle to support the frontplate of the tweeter. See to that you will get the right angle of the tweeter. Apply strong glue to the groove, the brackets and the magnet. Screw the tweeter in place and allow the glue to set. Solder the leads in place. The wider tag is plus, the smaller minus.

2. PLASTIC BAFFLES (OA-12/14/116/2212)
Here the slots give the correct angle from the old tweeters. Make some blocks of hardwood or some other type of ”dead” material. They shall be 9-10 mm thick, 25mm wide (max) and the height between 25 and 35 mm. Glue the blocks in the right angle in the recesses for the magnets of the old tweeters. See to that you get the right angle for the blocks. Remove the sticker from the tweeter as mentioned in last section. Apply glue to the blocks and press the magnet in place. This should result in a perfect angle for the tweeter.

Carlssonplanet have developed brackets specially for the Carlsson speakers but we have not yet managed to get them in production and therefore they are not yet available.

On the OD-11 the tweeter is mounted in a recess in the baffle. To be able to fit the new tweeter you have to cut grooves on booth sides of the recess. The plastic is fairly thick but do watch out so that you do not cut through the plastic. Instead of cutting you can use a piece of sheet metal shaped as the frontplate. Heat the metal on the stove and slide it in to the right position. The plastic melts resulting in perfect grooves for the new tweeter. Seal the old screwholes with glue. Remove the sticker on the tweeters as described in section 1. Glue the new tweeter in place. For extra stability you can drill two holes at the back of the recess. The old screws are to short so replace them with new and longer screws. See to that the angle is correct. Also take the opportunity to change the wiring to the tweeters. Put the grill back and enjoy.

It should be noted that some breaking in of the tweeters is needed before the speaker gives its best. The sound does not ”open up” immediately.


Peerless 115DT26 25 mm textile dometweeter
Used in OA-50, OA-51 and OA-52.
Still available but you should consider an upgrade.

Vifa D25AG-35-06
25 mm alu-diaphragm. dometweeter
Used in OA-50.2, OA-51.2 and OA-52.2.
Still available but you should consider an upgrade.

Carlsson T-11oa
25mm silk dometweeter
Used in OA-50.3, OA-51.3 and OA-52.3.
Available through The Carlsson factory in Skillingaryd, Sweden:

John Larsen HiFi +46 370-70 900

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To open a Carlsson speaker takes time. There are a lot of screws, mainly in the speakers from the seventies; this contributes to the soundquality due to the high stability of the box. Use the correct screwdriver and booth hands so that you do not slip.

The models from the sixties (V-1, OA-4, OA-5 and OA-6) are usually assembled with glue. This means that you either have to use a saw to get to the filters (OA-4/OA-5) or as in the case with OA-6 Mk II you can get access through the woofers hole on the bottomside and poke around through there. This is no fun. On the OA-6 Mk I it is easier to get access to the filter, as they are located in the cavity for the midrange. It can however be a problem to replace the internal wiring with new wiring. The solution is the same as for OA-6 Mk II, go from the underside.

Note: In some productions of these speakers they have been screwed together, this makes the above mentioned problems easier to solve. Check this prior to starting disassembly of your speakers as it affects your planning.

The smaller models, OD-11, OA-12 and OA-14 can only be opened from the topside. Unscrew all the screws around all sides of the speakers and place them in a small jar with oil to prevent rust. On the OA-12 and OA-14 also remove the two screws in front of the woofer. Get a good grip on the standing support between the tweeters and twist and pull the baffle out. Be careful so you do not damage the wiring and the filter. Remove the wiring from the filter.

The bigger models OA-116 and OA-2212 are somewhat more complicated. You have to unscrew the baffle (the baffle on top is actually in two halves) and the bottomside to get full access to the inside, when you do this there will be a lot of stuffing around and it is easy to pull out the internal wiring by mistake. So when you start on these you should always first lift the baffles. Mark all the leads from the filters and remove them. After doing this you can start on the baffle for the woofer (bottomside). These can be difficult to get out, start by using a carpetknife around the sides.

The OA-50, OA-51 and OA-52 do not have as many screws as the earlier models. Here you might instead run into problems due to damaged screwholes, be gentle. The inside of these models can only be reached through the holes for the woofers. The boxes are braced with internal walls that are perforated only with 7 cm holes. To replace all of the internal wiring on the OA-51 is a nightmare.

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The rubberparts are as in so many other areas a critical issue. There are many rubberparts that prevents vibrations from spreading and other that works as gaskets. All rubberparts should be treated with glycerol in order to once again become soft.

Replace with Neoprene seal. Purchase material for making O-rings by the meter. Use glue to set it all around before setting the baffle.

This is easy to obtain, check auto-parts or a glazier.

The speakers often use a rubber part to prevent vibrations spreading to the baffle. These can also be replaced with standard parts on the market. For the rings on the models from the sixties look for grommets in your electrical store. Still, most of these can be salvaged with glycerol.

The suspension of the filters on the models from the seventies is usually OK but give them a treatment with glycerol anyway.

These are made of massive rubber. Use the glycerol again. If the feet are damaged or missing contact Carlssonplanet, there are ways to repair them or to make substitutes.

The rubber is peeling off from the wheels and there are no direct replacements that we know of. A suggestion that we have heard of is to use self-amalgamating tape on the wheels. Alternately putting the wheels on soft feet.

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There is usually a lot of oxide on the internal wiring. To replace some or all of the internal wiring on speakers older then 10 years often leads to a better soundreproduction. The most critical one is the one leading from the terminals to the filter. The terminals are on the older models not of the best sort and should be replaced with new and better ones. Use bindingposts on the bottomside The wiring from the filter to the speakers can also be replaced but the improvement from this is not normally as big as with the other lead but it feels more proper. Preferably use teflon-insulated solid wire. You can make your own from OFC, Oxygen Free Copper, wire with a diameter of 0,5 mm and put in a 0,7 mm Teflon sleeve. There are also three “off the shelf” alternatives to this:

1 Use ordinary solid wire with two leads, “EKUA”.

2 Use “equipmentwire”, a coloured solid wire that is used in many domestic application such as lamps etc. It is available in different colours and thicker than the EKUA. The fact that it is thicker makes it better suited to use from the terminal to the crossover.

3 Supra-Ply cable in suitable dimension. This is a hi-fi cable that is available at better hi-fi stores. It is closer to Stig Carlssons ideas about minimising the impedance. The downside is that it is normally impossible to fit between the speakers and crossover and it is also expensive.

The new wiring can be connected with crimp terminals but it is better to solder them if possible. By this you avoid future oxidation, better still to use solder containing silver, but this is more difficult to solder.

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The usually blue or red jumpers on the baffles on all the models from the seventies are used to adjust the frequency response of the speaker in the actual listeningroom. On the OA116 and OA2212 there is also a jumper on the bottom of the speaker. The jumpers are used to adjust the tweeters to zero, -one or -two dB. On the bigger models also mid- and bassrange can be adjusted the same way. Today they mostly cause problems as they become oxidised leading to problems in the signal path. The signal path also becomes unnecessary long. A good upgrade is to remove them. Step one is to determine the best position for the jumpers according to your listening room. Step two is to disconnect the wires going to the jumpers and back from the crossover. Step 3 is to take some short wires and connect to the right places on the crossover thus replacing the jumpers. The “Zero” positions of the jumpers are left/counter clockwise for the tweeters and the position closest to the back on the bass-range. If you have an amplifier without tone controls you can of coarse consider keeping them if you check the connections and remove any oxide. Leave the jumpers in place even if you disconnect them. Try to keep the look close to the original.

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The capacitors in the crossovers from the seventies are of the timestable variety and do not need to be replaced. Stig Carlsson, as opposed to most other designers in the seventies, was particular about that his designs should work properly for decades to come. Therefore he always used timestable plastic film capacitors in his crossovers. So far we have not come across any of these capacitors that have deteriorated; this shows Stig Carlsson cared about the listeners. However capacitors have evolved since the seventies and many of the polypropylene capacitors of today are superior to the polyester capacitors from that time. Thorough listeningtest has been carried out and this leads us to specially recommend the black/red SCR/MKP capacitors. These are available from and similar places for a couple of Euros each. On the speakers from the fifties and seventies the capacitors usually needs to be replaced as these have dried out resulting in incorrect performance.

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The Inductances on a Carlsson speaker does not need to be replaced, if the glue has not melted. The are always made with an air-core and we have never seen any that has oxidised. The inductor can however come loose if the glue is too old. If they have come loose glue it back again with strong glue or attach it with silicone to prevent vibrations. It is not inconceivable that an inductor can short-circuit if the isolation deteriorates. If that has happened they must be replaced to make the crossover work properly. If so take the OK inductor from the other speaker and bring to your local dealer to have the inductance measured. If this is not possible contact Carlssonplanet and we will help you with the correct data. If you have to replace the inductor get one with the same thickness of the wire. Stig Carlsson thought of the use of oversized inductors as ignorance. If you do replace them it is possible to use copper-foil inductors instead as used in the later models of OA-52 (Mk II and Mk III). Just see to that you get the same impedance, otherwise the crossover will not be the same. Fitting copper-foil inductors is difficult in some models due to their size and it is hard to say if it is an improvement or not.

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There are almost never any problems with the resistors. We do not recommend any specific brand but as with all components different people have different idées…

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All speakers benefit from the use of soft-feet such as ”SD-Feet” that de-couples the speaker from the floor. These feet stop the vibrations emanating from the speaker to reach the floor. Most people that have used soft feet for their speakers first get the impression that the volume has been reduced. But when the volume is increased you realise that what happened was that the distortion is gone! The sound becomes softer and more dynamic and you will not become tired from listening to the music.

OA-52 The Mk I was not delivered with soft feet as opposed to the Mk II and Mk III. If you have a Mk I you can order the correct feet. They are available through : The Carlsson factory.

OA-50 For this model soft feet has been available, as extras, since the Mk II was introduced. They can be purchased from: The Carlsson factory.

If you are thorough when installing the soft feet you should do it as it is done in the factory:

1 Turn the speakers up-side down to get comfortable access to the bottom.

2 Get a 32 mm circular holemaker and make a one centimetre deep hole in the corner under the pyramid were the speakers are. Make another hole like this in the corner facing the listener.

3 Switch to a 40 mm circular holemaker and make a one centimetre deep hole in the two remaining corners of the speaker.

4 Pry loose the round parts of wood in the holes that you have cut to make room for the feet.

5 Sorting the feet: The feet are marked with A, B, C and D and shall be installed like this. A. Small brown one under the speakers. B and C. Big green ones in the two bigger holes. D. Small green one in the hole facing the listener.

6 Mounting the feet. Put strong glue in the holes and put the right foot in the right place.

7 Flip over the speaker to put the glue under pressure while it sets.

Feet for both models can be purchased from the Carlsson factory:

Carlssonfabriken i Skillingaryd, Sweden:
John Larsen HiFi +46 370-70 900

The prices for eight feet (for one pair of speakers) are: Fitting the OA-50: 550SEK Fitting the OA-52: 350SEK.

The use of the slightly cheaper “vibrafeet” is an improvement but as the speakers are not symmetric these feet are not perfect. The weight varies greatly in the different corners of the speaker.

We strongly recommend you not to use spikes under the Carlssonspeakers.

OA-12 AND OA-14 These are from the beginning equipped with soft feet.

OA-116 AND OA-2212 These are equipped with soft rubber wheels from the beginning. These are most likely ruined by now, see hints for restoration.

For all other Carlsson and Sonab OA/OD speakers we recommend the use of soft feet such as the “SD-foten”. It is the best solution for all speakers.

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Martin Dellstig – Co-Editor

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