Sonab OA5 mkII
Contents
1. much better The coil in series with the 9710 is from pretty thin wire but we re not dealing with heavy loads of amperes here so not much would be gained from changing this one either Sonab OAS5 mkII cabinet 3av8 2010 05 01 11 16 Sonab OAS mkII http www troelsgravesen dk sonab htm 7 a iss 359 Sd Cabs are made from thin 12 mm particle board veneered on both sides to make an overall thickness of 13 mm Bottom and top are made from 16 mm particle board A number of fillets are placed inside to strengthen the cabinet and damp resonances Se photos above These cabs are lightweight Some 10 kgs in total incl drivers crossover and damping material and we may expect a highly resonant system but this doesn t appear to be the case The bass quality is anything but boomy Not reaching deep but short and fast undoubtedly due to overall construction and not least the special use of damping material ggg o SONAB AOS mkII LJ This is how the damping sheets are arranged in the cabinet The 9710 driver is placed to the left here Cross braces are placed symmetrically Sonab OAS5 mkII crossover 4av8 2010 05 01 11 16 Sonab OA5 mkII Sav 8 http www troelsgravesen dk sonab htm SONAB OAS mkII R2011 12011 C1011 Peerless MT 20 HFC lt source lt source 021 C1011 6 800 uF R1021 0 200 ohm L1021 0 510 mH R2011 0 200 ohm L2011 0 510 mH Philips 9710 OAS mkII crosso2. only varying 7 to 10 ohms from 20 to 1000 Hz Take that Consequently phase angles are modest not to say almost flat Overall sensitivity is around 90 dB 2 8 volts taken from the midrange with a response rising some 10 dB towards 3 5 kHz No surprise the 9710 only has a modest 0 5 mH coil in series not nearly enough to tame the terribly 9710 treble peaking However these speakers are not fortunately meant to be listened to on axis and a rising frequency response is expected from an omni directional speaker to balance the overall in room sound From setting up the speakers first time it becomes immediately clear that these speakers have a bright presentation Very bright indeed with way too much treble There will be a few recordings that will stay on the shelf for good No matter how the speakers are placed in the room this stays the final verdict I badly miss a pre amp with tone controls to tame the treble region as would have been the case back in the Seventies If I had to clone the OAS I d probably use a 2nd 3rd order filter to tame the treble range Based on modelling this would also allow the drivers to be connected with same polarity which may not be such a big deal due to the placement of the tweeters The tweeters were not the problem here The troublemaker is the 9710 treble peaking and only a higher order filter can tame this Having four tweeters allows a resonably low point of crossover and there s no point in not bringing down the 971
3. 0 treble peaking However these speakers were for loan not for tweaking I guess these speakers are high WAF modest size and exquisite veneering The speakers came with a black stocking around the 9710 driver Removed here for the photo shoot lav8 2010 05 01 11 16 Sonab OAS mkII http www troelsgravesen dk sonab htm Base plate covering two bottom holes of 54 mm diameter Apparently no feet was ever attached to these speakers Some small rubber or felt pads would do well in stabilising the speaker on the floor A DIN socket is seen at the end of the base plate for connecting to the amplifier I removed this a added a pair of heavy screw connectors 2av8 2010 05 01 11 16 Sonab OAS mkII http www troelsgravesen dk sonab htm Left Cabinet interior Right Two sheets of fiberglass placed as shown on drawing below Left Two renovated 9710 drivers 1 e cone suspension added a thin layer of flexible coating Right I rarely have to sew making loudspeakers but this calls for a stocking of front grille cloth as the drivers pointing upwards are true dust collectors a Right Crossover is simplisity itself 0 5 mH to the bass drivers and a 2nd order filter for the tweeters consisting of 6 8 uF cap and 0 5 mH coil I feel certain the crossovers are original as few diy ers would use wax for coating the coils The film capacitor polyester will probably last forever so no reason to change this with some PP that may not be
4. I Hi Nice to see that there is good response to your article I have also seen the article on the 9710 Actually been considering to build he cabinet with the two CT62 tweeters since I have all parts lying around So I just planned to make a few clarifications to my last mail The support was mounted on the baffle when you purchased the kit It s not something you add when assembling The idea with coating is perhaps incorrectly described it is not about coating the cone The idea is to glue back he cone to the basket On old MT20 it sometimes starts to come loose around the edges resulting in this terrible hissing sound If your tweeters are mint this shall not be done since nothing then will be gained Regarding the adjustment of the basket I tried to enclose it in the e mail but it only came back so now I have uploaded it on CarlssonPlanet under downloads instead Good luck By the way I just realised we have had this E mail conversation in English would Danish Swedish be better Best regards Martin My comments The speaker tested in this article seems more in accordance with the factory made OA5 mkII looking at the photos on the carlssonplanet website Apparently the kit OA 5 K had recessed drivers i e top panel was lowered into the cabinet making a flat top However the basket holding the damping material below 9710 driver looks home made I m pleased to see the bottom panel with the two holes being in accordance w
5. Sonab OAS mkII http www troelsgravesen dk sonab htm Sonab OAS mkII July 2009 Copyright 2009 Troels Gravesen One of my neighbours daughter threw a party and cranked up the volume of daddy s stereo and fried the voice coil on one of the Philips 9710 drivers in these vintage Sonab OAS speakers Poul Erik had bought these speakers at the local second hand market he was there before me and had come to like the vivid presentation of these high efficiency easy driven speakers of the Seventies So he googled Philips 9710 and the connection was made From eBay Poul Erik bought a pair of 9710s from Germany and one of the drivers was suitable for restoration The other had had some surround repair too much white PVA glue and a resulting Fs of some 90 Hz Too bad but that s how goes buying on eBay from second hand dealers knowing nothing about loudspeakers The Sonab range of speakers from the Seventies are speakers I ve long been looking for in order to find out what the 9710 could do in an omnidirectional set up and this OA5 mkII did call for a few surprises First of all I assume this is a Sonab OA5 mkII from reading the excellent website on these speakers http www carlssonplanet com oaSii php The technical data suggests the following Volume 47 liter Dimensions 24 x 61 x 43 cm Weight 10 kgs Principle Omni directional bas reflex loaded speaker although it does not have port tubes see later Impedance 7 ohms Frequenc
6. e to the speaker they are of coarse very bright since you then also get the direct radiating sound from the speaker 9710 The tweeters are often hissing producing terrible sssszzzssz noise and the bass is not too bad With good tweeters they are nice with Dire Straits and similar music If the tweeters are in working order but hissing you can fix them somewhat see http www carlssonplanet com renovation php lang sv amp Scroll down to Coata gamla diskanter and read on So my question is really if you have tuned the damping basket before listening measuring There is a method to tune the basket for the correct damping using a tone generator a volt meter and an amp If the damping basket and its material is too tight you would get poor bass If you check out the download area of CarlssonPlanet you ll find three documents that might be of interest if you have not already seen them http www carlssonplanet com downloads index php act viewall OA 5K Broschyr Popboxen original article from 1964 Carlsson Ortho Acoustic loudspeakers Design and Performance principles Some are in Swedish but I think you ll manage I hope you will find something of interest in these ramblings because I found your study interesting When somebody does something like this about something that interests me I m glad about it So I try to respond with some input of my own Would you like a copy of how the damping is to be adjusted Can the damping basket be adju
7. istening to the ever lasting Jazz at the Pawnshop all the usual details of rattling glasses and people speaking is pretty much gone Overall the sound lacks bass and the middle and upper treble is dominant and prevents you from turning up the volume which again will make the sound even slimmer as we do need a certain loudness level to energize the room A drummer seriously hitting his cymbals let s be honest about the treble coming from 5 drivers in different locations it just isn t good from these speakers This may all sound a bit negative but I still think omnidirectional speakers are interesting and I may well give it a shot some day The later Sonab models with tilted midbas and quarter circle of tweeters may sound differently and seems more like something that did address the issues discussed above Stig Carlsson s persistent work on speaker and room integration is admirable to say the least but this OA5 wasn t the final answer to this most troublesome area Response to article Hi Troels Firstly thanks for your web site I have really enjoyed reading your articles over the past few years The first thing Ido each day as I logon to my PC is to check and see if there are any additions to your web site You have provided a great resource for the DIY community Secondly your article on the Sonab speakers is very interesting Iam hoping you continue to look into omnidirectional speakers the audio community seems very divided on their merits h
8. ith the kit design despite to speaker support looking homemade too The crossover looks OK being two coils and a cap The placement of damping material seems OK All things equal I believe that what I heard here has been well in accordance with what an OA5 mkII customer heard back in the Early Seventies Having properly working drivers correct crossover and cabinet with correctly placed damping materials it can t go much wrong Thanks to all for contributing with comments and pics on this interesting design Regards Troels And thanks for your second mail Martin Having the Service Manual for the OA5 mkII is great Lots of details here Download manual from this link Service Manual OA 5 Type 2 Loudspeaker Best regards Troels The Carlson Sonab Speakers you came across are not DIY but genuine I came across an identical pair in the mid 90 s working in a London 2nd Hand HiFi Shop Ciao T o 0 0 Believe it or not My neighbour has picked up another pair of Sonabs This time the OA 14 To be reported later this year 2010 05 01 11 16
9. n overbevisning at du har tenkt disse tankene og jeg har et hap om at du skal prove ut en modernisert verson av OA 5 mk IL Igjen takk for mye intressant lesning Mvh Johan Hi It s fun to read when somebody really looks into to something In your piece of the Sonab OA 5 there are a few things that strike me as odd I think as you already suspect that these are not the same as original factory built units Some things look correct others don t Correct looking The box the four side walls The damping material and it s position inside the box Incorrect looking The support for the net between the tweeters is not there see picture 1 below The baffle it self looks strange but perhaps it is just repainted The crossover looks like some I have seen on kits for the Pop boxen except for the capacitor which is much newer than that Pop boxen DIY version of OA 5 This damping basket looks like nothing I have seen from Sonab either it looks like picture two below or it s made of plastic on the ones I ve seen The bottom of the speaker is not as it normally is perhaps the chipboard under the speaker has been replaced The DIN plug is also not original Perhaps this is a speaker that has been refurbished with home made parts Listening When you talk about your listening impressions they don t sound to me as the numerous pairs I have had at home They are normally not so bright rather the opposite If you are standing up clos
10. owever it seems that good omnidirectional speakers have some very passionate supporters I found these reviews of the Shahinian Arc speakers which may interest you I think the Arcs use SEAS CA22RNY and 27TBF G drivers The slope of the Arc front panel is consistent with your comments about the later versions of the Sonabs Anyway thanks for the great work Regards Campbell A Response from Johan Norway suggesting this OA5 mkII is indeed a kit version which explains the missing badge Furthermore there should have been a mesh support on top of the speaker and the 9710 basket for the damping material was made from plastic in the original Thanks Johan for your comments jeg er ogs glad for det at du har pr vd ut Sonab OA 5 mk II og som Carlssonentusiast vil jeg bemerke f lgende De svake punktene gjengivelsen henger sammen med to ting foreldede elementer og manglende avstemming av kassen Bade Philipsbassen og Peerlesstweeterene har sine svakheter og de kan med fordel byttes slik dt er anbefalt p Carlssonplanet og Faktiskt Man kan ogs sette inn et bassrefleksrgr slik enkelte entusiaster har gjort med godt resultat Det ser ut som du har f tt en kit modell av OA 5 mk 2 alts et hjemmebygg Det gar frem av dempekurven som er av plast i orginalen og av den manglende runde pinnen som skal stikke opp mellom diskaneten p orginalen Hvis det mangler emblemer pa fronten ogsa sa er det nok temmelig sikkert et kit som noen har laget Jeg er av de
11. speaker positions during measurements Position B not shown here MLS Frequency Response 27 07 00 114001 180 0 CHA dBSPL Unsmocthed 1 A 16K Rectangular Stat 1 23ns Sto S1ms Ee a File sonab_AOSmil_0 Smib _97 10 onads 28 208 mis Here a measurement on axis 0 5 meter distance normalised for 2 8V 1 meter System sensitivity is around 90 dB 2 8V 1m valued from the response 500 Hz MLS Frequency Response 25 07 09 21 53 16 MLS Step Response 27 07 09 11 2641 Ht a p jj TTS ai T f mi 0 1800 20 1 Me 20 000 100 20 39 40 CHA Onm Unsmocthed 1 2Hz 16K Rectanguar Alias Stop 319 98ms FrequO 3 13 50 60 70 80 ms 90 t00 CHA dBSPL Unsmoothod 1 2kKHr 16K Rectanguiar Stat 3 0ims Step 6 66ms FreglO 273 S0Hr Pile sonapd_ren_m s imp misi Pile sonab_AOSeia_side_ Tegip_ 22 205 mis Left Impedance of left and right speaker showing decent bass tuning i e placement of damping material Right Step response measured from position C side The last four graphs are from various measurements with speaker against a wall with different distances to side wall 6av 8 2010 05 01 11 16 Sonab OAS mkII http www troelsgravesen dk sonab htm Left 9710 side against wall and 0 5 m to sidewall blue and 1 5 m to side wall red Right Tweeters against wall and speaker 0 5 m to side wall and 1 0 m to side wall red With the 9710 not
12. sted on your speakers Thanks a lot for the interesting reading Martin 7av8 2010 05 01 11 16 Sonab OA5 mkII Sav 8 http www troelsgravesen dk sonab htm My comments in bold Hej Tack for din intressanta genomg ng av Sonab OAS Tyvarr ar det nog ingen kit byggsats utan ett DIY Flera detaljer talar mot t ex Pinnen mellan diskanterna saknas Det ska vara en tygpase original fjernet af mig da den var i darlig stand Det ska vara tatningslist under basen original fjernet af mig og erstattet med gummiliste Basen ska var fast med gummibussningar Det ska vara fastbyglar till diskanterna Baffeln ska vara forsankt flera cm Delningsfiltret ser inte ratt ut Kondensatorn r f r modern filmkondensatorer fandtes l nge f r Sonab sa Joda det ska finnas ett Sonab marke Dampkorgen har fel metalln t Detta fann jag vid en snabb genomgang Kan precisera om du vill Jag har n gra bilder fran kitet till Typ 1 om du r intresserad mvh Rolf Hej det har ar vad jag har om OAS kit Obs att det ar typ1 men den stora skillnaden ar baffelns lage och ett h gre galler Bilderna ar scannade ur en tidning TfA nr 18 1968 Konstigt att inte n gon enda m nniska tycks ha n gon byggbeskrivning i original kvar Det s ldes ju massor mvh Rolf Da tt u m n A YNY gt Let or le Z a Click image to download 4 kit files zip file 3MB Pics 2 and 4 from left taken from carlssonplanet website on OA5 mkI
13. up against the wall and 1 meter to side wall makes a decent smooth albeit seriously rising response This is against most recommendations I can find that will suggest the 9710 being close to the wall but this seems to consistently produce a serious dip in the 130 200 Hz range something that will add to the thinness of sound It lacks weight as most music has a lot of energy in this range By the way These speakers do not say much below 50 Hz where the 37Hz claimed low end extention seems fairly optimistic The heavy cabinet damping is partly responsible for this The 9710 can do better but not at the same time produce an impedance profile like seen here Final comments Taking the Sonabs to our living room I tried all possible speaker placements From our sofa some 2 2 meter to the speakers I found the speakers placed flat against the rear wall to produce the best sound Having the speakers standing out from the wall with either the 9710 or the tweeters against the wall just didn t work Phase tracking between drivers is fairly good when I measure the response on axis i e like measuring a conventional speaker data not shown but despite treble coming from all over the place having the drivers on line appear to compromise driver integration thus flat against the wall with a 20 cm distance between cabinet and wall These speakers are quite good at making music in a room if you get my meaning Forget about pin point imaging and the like L
14. ver design simplicity itself 1st order to the 9710 and 2nd order to the tweeters All tweeters are 8 ohms SONAB OAS mkII plus 9710 minus 9710 plus in minus in Crossover layout The PCB looks like the very first PCBs I made many years ago with a marker directly on the copper side before etching That s what made me wonder if this speaker is a cleaver clone or the real thing Measurements How on Earth do we measure an omnidirectional speaker spewing sound in all directions Definitely not an easy task and what s shown below is with every possible reservation except for the impedance measurements At least these can t be argued MLS Frequency Response 27 07 06 11 24 455 MLS Frequency Response 27 07 00 112641 CHA dBSPL Unsmocthed 51 2kHz 10K Rectanguter Stat 2 ims Stop 615ms FreqlO 290 91THz Pile sonab_ AOS Imit 22205 mis Left Conventional gated measurement meter distance at 20 cm above top panel height Speaker placed like A see below Blue minimum phase Right Red position A Blue position C CHA dBSPL Unsmocthed 51 2kKHzr 16K Rectanguer Stat 2 ims Step 6 1 5ms FreqlO 29091THz Pile sonab_ADSimea side Trip_ 22 205 mis 398 0 Deg 288 0 2010 05 01 11 16 Sonab OAS mkII http www troelsgravesen dk sonab htm A FREE FIELD f MICROPHONE B FREE FIELD f MICROPHONE C FREE FIELD f MICROPHONE Various
15. y range 37 18 000 Hz Crossover frequency 2 700 Hz Bass mid Philips 9710 Treble units Peerless MT 20 HFC This is all fully in accordance with my findings except for the 37 Hz bass extension The speakers have no Sonab badges and taking them apart made me wonder whether this is really a commercial product or some cleaver cloning of the same I believe this is a true Sonab product from the cabinet work but the 9710 basket and the crossover PCB suggests amateur work The principles of these speakers can be found on the carlssonplanet website and I won t get into details with this but the cabinet calls for some comments Take a look a the photos below What is this A 47 liter cabinet with the 9710 driver placed in a metal mesh basket with some heavy glassfiber material between driver and mesh making a low pass filter that can be adjusted due to the basket being suspended on three screws that allows you to increase or decrease the acoustic resistance of the fiber material An acoustic vent sort of Something similar can be found on some Lowther drivers Next we have a cabinet divided into two compartments by two heavy fiberglass sheets The lower compartment is open to the outside by two 54 mm holes at the bottom no tubes here In reality I guess we can call this a two step aperiodic system with progressively diminishing acoustic resistance towards lower frequences What is sure is this I have never seen a more valve amp friendly impedance than this
Download Pdf Manuals
Related Search