I've picked up a cheap pair of Monitor Audio R352s to play with. The tweeters were blown so I've ordered a replacement pair, but the bass/midrange units seem to be OK.
Looking inside I see the crossover isn't on a circuit board, nor the kind of components I'd expect from a circa 1980s loudspeaker. Also the cabling to the bass/midrange looks like an 'improved' type. Oh yes, and each speaker featured a white tee shirt stuffed into its reflex port....a variation on the straw-damped ProAc etc ports I'm familiar with!
I'd appreciate any information about the 'stock' MA R352 crossover. Also, does anybody recognise the layout? I'm assuming the original parts have been replaced in an attempt to make an improvement, but the socks suggest the last owner found the new arrangement to be unbalanced in the bass department.
Looking inside I see the crossover isn't on a circuit board, nor the kind of components I'd expect from a circa 1980s loudspeaker. Also the cabling to the bass/midrange looks like an 'improved' type. Oh yes, and each speaker featured a white tee shirt stuffed into its reflex port....a variation on the straw-damped ProAc etc ports I'm familiar with!
I'd appreciate any information about the 'stock' MA R352 crossover. Also, does anybody recognise the layout? I'm assuming the original parts have been replaced in an attempt to make an improvement, but the socks suggest the last owner found the new arrangement to be unbalanced in the bass department.
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Hi,
I rather think the crossover has not been touched and is in its original condition. It is a single coil for the woofer and a classic second order high-pass filter for the tweeter. This is a fairly standard crossover for a commercial speaker from that time. The use of 3/4" tweeters was widely spread back then.
I rather think the crossover has not been touched and is in its original condition. It is a single coil for the woofer and a classic second order high-pass filter for the tweeter. This is a fairly standard crossover for a commercial speaker from that time. The use of 3/4" tweeters was widely spread back then.
Agree with Dissi, of course.
For fun, replace the tweeter cap with a 4uF Mundorf MKP, around $7, replace resistor with 5 or 12 watt Mills. Should be under a $25 experiment for you. Again, this is just experiment, if you want to learn about whether good film caps / resistors sound different for yourself.
Best,
E
For fun, replace the tweeter cap with a 4uF Mundorf MKP, around $7, replace resistor with 5 or 12 watt Mills. Should be under a $25 experiment for you. Again, this is just experiment, if you want to learn about whether good film caps / resistors sound different for yourself.
Best,
E
These are a familiar Robin Marshall design.
I had a lot of fun with the later R300/MD:
http://www.diyaudio.com/forums/multi-way/203461-restoring-monitor-audio-r300-bookshelf-speakers-4.html#post4990630
It became part of my loudspeaker education. I currently use this circuit:
The original is below. To address your issue, the smaller bass coil should improve the bass balance towards lighter. The tweeter is possibly a Vifa D19, interchangeable with the 94mm SEAS 19mm units. I had to put fresh ferrofluid in mine.
TWEETERS
I had a lot of fun with the later R300/MD:
http://www.diyaudio.com/forums/multi-way/203461-restoring-monitor-audio-r300-bookshelf-speakers-4.html#post4990630
It became part of my loudspeaker education. I currently use this circuit:
The original is below. To address your issue, the smaller bass coil should improve the bass balance towards lighter. The tweeter is possibly a Vifa D19, interchangeable with the 94mm SEAS 19mm units. I had to put fresh ferrofluid in mine.
TWEETERS
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Yes, I do in sim. It's interesting to see what the new one does that the old one didn't. I used 1.5mH for both here, because bass level is such a matter of taste.
More driver rolloff so less breakup, flatter frequency response with a 2dB lift from 500-2000Hz in the vocals range. Tweeter gets an easier ride. The 7.5R/0.68 Zobel reduces the high end a bit and improves amplifier load.
It's actually close to a KEF design. If I was PMK145, I wouldn't give up on the old tweeters until DC tested. They should read 6 ohms if voicecoils intact. I'd suspect dried out ferofluid stopping them working.
It's also not hard to unwind coils to reduce values, but a multimeter with mH scale is needed.
More driver rolloff so less breakup, flatter frequency response with a 2dB lift from 500-2000Hz in the vocals range. Tweeter gets an easier ride. The 7.5R/0.68 Zobel reduces the high end a bit and improves amplifier load.
It's actually close to a KEF design. If I was PMK145, I wouldn't give up on the old tweeters until DC tested. They should read 6 ohms if voicecoils intact. I'd suspect dried out ferofluid stopping them working.
It's also not hard to unwind coils to reduce values, but a multimeter with mH scale is needed.
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Thanks for the replies and information. I'll give this some thought and because this is a side project while I do work on the house I'll bide my time and do a bit more reading. I've measured the components and the inductors are more than 10% higher in value than the 'stock' items suggested in your diagram Steve, but the meter I'm using isn't a precision bridge so it may be reading high. The 4MFD capacitor is different from the 3.3MFD of course.
To kick things off I'm trying 2nd hand tweeters but the ferrofluid may need some TLC.
To kick things off I'm trying 2nd hand tweeters but the ferrofluid may need some TLC.
Steve, thanks for the suggestion on the tweeters. I did test them with my meter though and they are both open circuit. One looks like an original and the other is a replacement. For the moment I'm going with second hand replacements via ebay to give it a go because that way I can check the overall sound without podding out a fortune.
My long-term plan for these speakers is a re-design using the professionally produced cabinet but I can do some listening in the mean time and practise my microphone measurement skills etc.
My long-term plan for these speakers is a re-design using the professionally produced cabinet but I can do some listening in the mean time and practise my microphone measurement skills etc.
I'm sure you'll end up with a good speaker. The MA 352 was well-enough liked.
I mostly adressed the issues I could hear with my similar model. I even had a good time with a little cheapie cone tweeter. A monacor HT-22/8 which cost about £7.
The SEAS 19TAF/G is about £30 these days, and it's pretty good:
Seas 19TAF/G H0414-08 Tweeter - Prestige Series
Wilmslow have a good range of accessories too:
Components and accessories
The cheaper 250V monacor capacitors are small and easy to work with. Maplin Tag strip and cable ties and are useful:
5 Way Tagstrip | Maplin
Large Cable Tie Base White 100 Pack | Maplin
Self Locking Cable Tie 203x2.5mm 100 Pack | Maplin
BTW, this design is possibly just about right for an upgrade:
Bass level intrudes where midrange is weak, and small changes are very audible.
I mostly adressed the issues I could hear with my similar model. I even had a good time with a little cheapie cone tweeter. A monacor HT-22/8 which cost about £7.
The SEAS 19TAF/G is about £30 these days, and it's pretty good:
Seas 19TAF/G H0414-08 Tweeter - Prestige Series
Wilmslow have a good range of accessories too:
Components and accessories
The cheaper 250V monacor capacitors are small and easy to work with. Maplin Tag strip and cable ties and are useful:
5 Way Tagstrip | Maplin
Large Cable Tie Base White 100 Pack | Maplin
Self Locking Cable Tie 203x2.5mm 100 Pack | Maplin
BTW, this design is possibly just about right for an upgrade:
Bass level intrudes where midrange is weak, and small changes are very audible.
Those are some real subtle changes, not sure I could have gone that far, but you must have a very discerning ear. 🙂
Did you notice an improvement off-angle?
Did you notice an improvement off-angle?
TBH, Erik, some of the trade-offs become too difficult. This 94mm SEAS 19TAF/G tweeter is quite a fragile device. It can't be pushed too far or too low. The third order KEF filter is a bit of a classic, IMO.
Here's something I tried while building the current version. A second-order design with a bit of bass voicecoil damping. It looked good on FR, and good off-axis. But a strangely hollow and disembodied sound. The problem was in the terrible phase. And flipping polarity then led to a poor frequency response.
My current wheeze is these BBC BW3 designs which have great impedance due to the passive RL bafflestep, and that familiar recessed woofer and negative polarity.
Rogers Loudspeakers › LS5/9
It solves a lot of problems. And maybe explains what you are seeing in the new Harbeth 40.2! 😀
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These R352s had blown tweeters so I thought I'd take the chance to practise cleaning out the old ferrofluid. It was interesting to find that the original MA tweeter had fluid present but the replacement D19 was dry with no residue either. I wonder if the original owners thought the speakers sounded strange with such a mismatch?
The ferrofluid in the original wasn't too sticky and soaked happily into the corner of a sheet of kitchen towel.
The ferrofluid in the original wasn't too sticky and soaked happily into the corner of a sheet of kitchen towel.
I suspect I have put a bit of ferrofluid business Blue Aran's way.
Sonitus Audio Ferro Fluid (ferrofluid) for Speakers and Compression Drivers 0.5ml from Sonitus Audio 5.00 IN STOCK (13 Mar 2017)
It's something people with old speakers need to know about. 🙂
Bit of a mystery with the D19 tweeters.
Peerless by Tymphany D19TD-05 3/4" Poly Dome Tweeter
Some seem to be soft domes, some polydomes, but should have ferrofluid according to the spec sheet.
I tried 1.5mH coils in my speakers last night.
Sounds bassier, of course, but RUINS the sound! All boom and tizz! When I looked at the modelling, the 1mH coil actually gives +3dB more midrange and vocals. Which is the bit I like.
TBH, I don't think anything but 3rd or 4th order tweeter works well with an 8" bass. And I've tried all sorts of things. Terrible time-alignment problems that need negative polarity on the tweeter.
Sonitus Audio Ferro Fluid (ferrofluid) for Speakers and Compression Drivers 0.5ml from Sonitus Audio 5.00 IN STOCK (13 Mar 2017)
It's something people with old speakers need to know about. 🙂
Bit of a mystery with the D19 tweeters.
Peerless by Tymphany D19TD-05 3/4" Poly Dome Tweeter
Some seem to be soft domes, some polydomes, but should have ferrofluid according to the spec sheet.
I tried 1.5mH coils in my speakers last night.
Sounds bassier, of course, but RUINS the sound! All boom and tizz! When I looked at the modelling, the 1mH coil actually gives +3dB more midrange and vocals. Which is the bit I like.
TBH, I don't think anything but 3rd or 4th order tweeter works well with an 8" bass. And I've tried all sorts of things. Terrible time-alignment problems that need negative polarity on the tweeter.
Thanks for the ferrofluid link - it will be interesting to hear the state of the used tweeters.
Regarding the dome material, some information sources imply the R352s have metal dome tweeters - perhaps that was just a couple of batches?
Regarding the dome material, some information sources imply the R352s have metal dome tweeters - perhaps that was just a couple of batches?
I have a pair of R652/R1200 bastard clones.
They started out as a variant of the 652, wit original woofers, a copy of the cabinet and crossover and Scanspeak 2010 3/4" tweeters.
I lost one of the woofers, and got a pair of replacement R1200 woofers. This plays very nice.
X/O is one 1.1mH coil, a 2.2 ohm resistor and a 3.3uF cap.
Johan-Kr
They started out as a variant of the 652, wit original woofers, a copy of the cabinet and crossover and Scanspeak 2010 3/4" tweeters.
I lost one of the woofers, and got a pair of replacement R1200 woofers. This plays very nice.
X/O is one 1.1mH coil, a 2.2 ohm resistor and a 3.3uF cap.
Johan-Kr
As far as I know, PMK, yours and mine bass driver has a small cardboard voicecoil and a rubber dustcap, made by Elac and also used in the KEF Cara. Below looks familiar, doesn't it? Magnet size controls the bass damping from the amp. Big magnets for reflex, small ones for closed box, just how it works.
Tweeters are tweeters IMO. These ones are 88dB 94mm 3/4" domes. I've probably read too much of MA's old designer Robin Marshall, who thought metal domes were way better than soft dome or IMO, slightly better plastic (mylar or polyamide) ones on detail. So it's your pick really, and TBH, the art has come on since his day with ring-radiators like the Vifa XT25 and SB acoustics designs.
Nice work to check the crossover, Johan, and interesting. Below is the Monitor Audio R852. AFAIK, the R652, R852 and R952 and R1200 used a well behaved 6" polycone or plastic bass with a 1" metal tweeter with long tinsel leads to allow some excursion.
6" polycones can be as well behaved as some 8" paper cones. All a question of natural cone-damping.
Apparently, this 6" SEAS U18RNX/P will work well enough off a single coil:
H1571-08 U18RNX/P
And here's an 8" I would take on:
H1471-08 CA22RNY
Long tinsel lead tweeters can be like this for a single capacitor crossover:
H1318-06 29TFF/W
Below, also, is the well-behaved classic 6" Vifa PLWJ-00-08 polycone. Another very easy driver, IMO. But, TBH, I've heard too many simple crossover designs to be really impressed by them. They don't go loud without shredding your ears. 😀
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What this bastard 652 of mine does, is sing absolutely wonderfully with a high quality amp.
A $3000-$4000 tube amp isn't over the top on these. I used them for many years with a Cary SLA70B signature/SLP50B combo.
Johan-Kr
A $3000-$4000 tube amp isn't over the top on these. I used them for many years with a Cary SLA70B signature/SLP50B combo.
Johan-Kr
Yes, the bass/mid looks like an old Kef B200 basket with a paper/cardboard cone and what looks like a black plastic dustcap. On one driver the dustcap looks a bit askew so I'll be interested to hear what the whole speaker sounds like when the replacement tweeters arrive. The only metal tweeters I recall from when I last dipped my foot into audio (around 35 years ago) were a Celestion speaker with a copper dome and the Yamaha NS1000 with beryllium(?). I didn't take to either of those, although because I was trying to make money from audio at the time the Celestions were good to me because they sold a bit like hot cakes - against the Celefs and ProAcs that took an evening of demonstrating to move.
Regarding these MAs, I recall a couple of people in the industry remarking that the company was making good cabinets with half-decent materials - nothing exotic, but a good platform for listening, and for people to adjust and tune.
Regarding these MAs, I recall a couple of people in the industry remarking that the company was making good cabinets with half-decent materials - nothing exotic, but a good platform for listening, and for people to adjust and tune.
Ferrofluid
Just an update....the ebay Tweeters from a Mission speaker arrived as did the ferrofluid. Cleaning out the gap was pretty easy using a combination of printing paper, paper towel etc. The ferrofluid then flowed nicely into the hole, I removed a small amount of excess and clicked the front back in place. At first I forgot to push the face plate home fully, but then remembered and did so - one required a small amount of help using pump pliers.
The speakers are now complete and I did a small amount of listening. I found them OK at low-ish SPLs but louder they don't sound as clever - a little hollow to my ear. But because the enclosures are intended as the basis for a new speaker that's fine.
In a couple of months I'll get round to the next phase and hopefully will eb able to sell the drivers via ebay - I see people are still after drivers either as spares or to replace blown units.
Just an update....the ebay Tweeters from a Mission speaker arrived as did the ferrofluid. Cleaning out the gap was pretty easy using a combination of printing paper, paper towel etc. The ferrofluid then flowed nicely into the hole, I removed a small amount of excess and clicked the front back in place. At first I forgot to push the face plate home fully, but then remembered and did so - one required a small amount of help using pump pliers.
The speakers are now complete and I did a small amount of listening. I found them OK at low-ish SPLs but louder they don't sound as clever - a little hollow to my ear. But because the enclosures are intended as the basis for a new speaker that's fine.
In a couple of months I'll get round to the next phase and hopefully will eb able to sell the drivers via ebay - I see people are still after drivers either as spares or to replace blown units.
Hi all, ive been reading your comments I have a pair of Monitor Audio speakers that the tweeters have both gone on. I am looking into buying a pair of tweeters to replace the old one. To be honest I am not great at DIY and reading your comments Im well out of my comfort zone. Does anyone know a pair of tweeters I could buy that will be the easiest like for like replacement I could simple screw in to replace the others? Im in the UK.
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