All,
Having heard a pair of these big BBC LS 5/8 monitors about a year ago, I was quite impressed. Now I'm wondering whether it would be worthwhile to attempt making a clone.
That is, I have several Quad 405/2 amps and a friend has spare Audax TWO34XO tweeters, so I "only" would need to build the electronic crossover, the cabinets (12mm birch plywood dampened with bitumen) and decent stands. At least for electronics and woodworking, I think I can deliver a decent job. That doesn't guarantee good sonic results, of course.
Now I don't have the polypropylene woofers, somebody of my acquaintances suggested the Monacor SPH-300KE (kevlar cone). But the LS 5/8 has vents (if the design info I have is correct) -- not sure if these Monacor woofers would be the prime choice.
In the worst case, I end up with active speakers consisting of a Monacor woofer/midrange and an Audax tweeter and I will have learnt from the experience.
Some info sources, like the Harbeth users forum or Mark Hennessy's pages don't attempt to suggest replacement woofers, or at least not that I've found.
I also read about peaks in the frequency spectrum and adjustments in the electronic crossover to flatten these out. With different drivers, all this has to be re-considered.
I can, of course, go for a pair of those big monitors like Harbeth M40s which claim to be the descendants of the big BBC boxes (and they are much better according to the leaflets!), but the price tag is probably at least 20 times as high and they are less fun to get.
Or should I consider other designs? My preferred music is all sorts of "classical" music (from the 16th century to the 20th) and many jazz recordings (often from the 30s - 40s), to give an idea of what I expect to drive through those speakers.
Thank you for any thought and/or advice!
Jacques
Having heard a pair of these big BBC LS 5/8 monitors about a year ago, I was quite impressed. Now I'm wondering whether it would be worthwhile to attempt making a clone.
That is, I have several Quad 405/2 amps and a friend has spare Audax TWO34XO tweeters, so I "only" would need to build the electronic crossover, the cabinets (12mm birch plywood dampened with bitumen) and decent stands. At least for electronics and woodworking, I think I can deliver a decent job. That doesn't guarantee good sonic results, of course.
Now I don't have the polypropylene woofers, somebody of my acquaintances suggested the Monacor SPH-300KE (kevlar cone). But the LS 5/8 has vents (if the design info I have is correct) -- not sure if these Monacor woofers would be the prime choice.
In the worst case, I end up with active speakers consisting of a Monacor woofer/midrange and an Audax tweeter and I will have learnt from the experience.
Some info sources, like the Harbeth users forum or Mark Hennessy's pages don't attempt to suggest replacement woofers, or at least not that I've found.
I also read about peaks in the frequency spectrum and adjustments in the electronic crossover to flatten these out. With different drivers, all this has to be re-considered.
I can, of course, go for a pair of those big monitors like Harbeth M40s which claim to be the descendants of the big BBC boxes (and they are much better according to the leaflets!), but the price tag is probably at least 20 times as high and they are less fun to get.
Or should I consider other designs? My preferred music is all sorts of "classical" music (from the 16th century to the 20th) and many jazz recordings (often from the 30s - 40s), to give an idea of what I expect to drive through those speakers.
Thank you for any thought and/or advice!
Jacques
Driver technology, understanding of issues like center distances and diffraction, and materials have come a long way in 35 years. Good for us, but it does leave "vintage" system like that in the dust. Please go listen to some more contemporary well executed speakers. Then, with your competency in construction, build an established documented design or kit.
Speaker design is not slapping some drivers into a box and hooking up an active crossover.
Speaker design is not slapping some drivers into a box and hooking up an active crossover.
Technology may have advanced a lot (it certainly has, generally speaking), but many listening tests seem to indicate that you need to go to rather expensive areas of speaker offerings in order to get something similar in terms of convincing midrange rendition like the ugly, hyper-directional, position-critical Quad ESL 57 or even that other pièce de résistance, the AR3a. And even other boxes from an era long gone by.
When I listen to a recording of Andreas Staier playing a Conrad Graf pianoforte from 1824, I want it to sound similar to his live concert on the same instrument which I was happy to attend.
Many modern speakers are harsh, don't reproduce well the subtle harmonics from such instruments. Recordings of a Streicher pianoforte from around 1820 sound on most modern speakers like some mean out-of-tune honky-tonky piano.
OK, I must be getting old (I actually am) and from a certain age, strong high-frequencies start to hurt the ear, it seems. I'll have to live with that.
That was never my intention, having access to test facilities and the possibility to rely on the competence of several others with strong technical background. I just want to experiment and if the result is worthless, so be it. In the end, not much more than some panels of plywood will be spoiled, I suppose. There are worse activities to keep a retired person off the street
I have built several kits, the first one was a Wharfedale Unit 5, drivers from the Dovedale III, more than 40 years ago. Results usually were good enough (compared to equivalent ready-made speakers), all that may have given me too much confidence.
Thanks for the advice!
Cheers,
There is more to loudspeaker design the deeper you dig. I don't think you will be able to build a true competing speaker without years of research and experience.
As a project and a learning exercise I think you will be able to build something reasonable as you have access to measuring equipment. But as sreten has said, finding a suitable 12 inch drive unit could be hard these days and you might have to pay a lot and buy something from a professional range. A quick look at the Monacor SPH-300KE and it doesn't look that bad though...
Have fun! I'm sure you'll enjoy it.
As a project and a learning exercise I think you will be able to build something reasonable as you have access to measuring equipment. But as sreten has said, finding a suitable 12 inch drive unit could be hard these days and you might have to pay a lot and buy something from a professional range. A quick look at the Monacor SPH-300KE and it doesn't look that bad though...
Have fun! I'm sure you'll enjoy it.
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Well Jacq, I think you have not heard the right speakers. Some out there are really terrible. Might go find something like Vanderstein 2ce's. Not at all harsh. My last Seas based set are not at all harsh.
If you listen to a lot of vintage recordings, you may consider doing some filtering as what you are hearing now may be a result of the truth of the recording, where the vintage speakers did not have the bandwidth to reproduce the upper harshness. Listen on some good cans to get a baseline. Even the baby Grado's are far more accurate than the best speakers.
My wife has hyper critical sensitivity to harshness, i.e. tweeter distortion. Horns & strings would cause actual pain, but when we heard it live, no problem. After 30 years of building speakers, I discovered it is all about the tweeter quality. Once I moved up to the Seas 27tbfc/g level, the problem was solved. Suddenly we could use my Parasound amps rather than the Rotels and got an entire level of detail added with the same balance and smoothness. The problem was nothing but harmonic distortion caused by breakup IM producing sub-harmonics that were objectionable.
You have an advantage with competence in construction, now find an established modern design to put the effort into. I would love to do the Santori build being worked up over in the ventor's forum.
If you listen to a lot of vintage recordings, you may consider doing some filtering as what you are hearing now may be a result of the truth of the recording, where the vintage speakers did not have the bandwidth to reproduce the upper harshness. Listen on some good cans to get a baseline. Even the baby Grado's are far more accurate than the best speakers.
My wife has hyper critical sensitivity to harshness, i.e. tweeter distortion. Horns & strings would cause actual pain, but when we heard it live, no problem. After 30 years of building speakers, I discovered it is all about the tweeter quality. Once I moved up to the Seas 27tbfc/g level, the problem was solved. Suddenly we could use my Parasound amps rather than the Rotels and got an entire level of detail added with the same balance and smoothness. The problem was nothing but harmonic distortion caused by breakup IM producing sub-harmonics that were objectionable.
You have an advantage with competence in construction, now find an established modern design to put the effort into. I would love to do the Santori build being worked up over in the ventor's forum.
I often look at a design and ask myself what is GOOD about it.
Rogers Loudspeakers › LS5/8
In this case it is the big Audax TW034 tweeter crossed low around 1-2kHz with the big woofer. This is quite a common idea if you look at the Devore Orangutan or SEAS A26 designs. It crosses over below the bass cone breakup.
They sure don't make polycones with PVC surrounds anymore. In fact PVC was a bit of a disaster in the long run, tending to deform.
You mention Spendor and Harbeth. They do keep the tradition alive in passive speakers.
You might consider this H1659-08 U22REX/P-SL woofer with a E0055-06 T35C002 that will cross low. Quite a design job, but it's fairly familiar territory.
Rogers Loudspeakers › LS5/8
In this case it is the big Audax TW034 tweeter crossed low around 1-2kHz with the big woofer. This is quite a common idea if you look at the Devore Orangutan or SEAS A26 designs. It crosses over below the bass cone breakup.
They sure don't make polycones with PVC surrounds anymore. In fact PVC was a bit of a disaster in the long run, tending to deform.
You mention Spendor and Harbeth. They do keep the tradition alive in passive speakers.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
You might consider this H1659-08 U22REX/P-SL woofer with a E0055-06 T35C002 that will cross low. Quite a design job, but it's fairly familiar territory.
I look at these boxes and see sharp front edges, crossovers too low for the tweeter, and drivers that have been surpassed by the cheapest no-names on the market with cabinets made from PB that vibrated all over the place. They were the best we could buy back then. They are not worthy of a big-box store now.
Hi,
FWIW IMO building a classic BBC style 2 cuft speaker would
worthwhile and that Seas 8" mentioned by S7 would be on
the top of my list for such an endeavour.
The 35mm tweeter would not be, nor would the 34mm Audax.
Tweeters have come on leaps and bounds since the days
http://downloads.bbc.co.uk/rd/pubs/reports/1979-22.pdf
the above report was written, also see : TW034
Power handling, distortion and SPL of modern drivers
goes way beyond the drivers of 35 years ago and IMO
a 2cuft BBC style speaker would be very worthwhile.
Seas make some entirely suitable high quality modestly
priced 25mm dome tweeters that will do the job well :
http://www.seas.no/index.php?option=com_content&view=article&id=81&Itemid=105
http://www.seas.no/index.php?option=com_content&view=article&id=80&Itemid=104
The latter more suitable for the active route than the former.
Active arrangements like the LS 5/8 are very possible,
and a 405 for bassmid with a JLH10 for treble would
be a very nice contemporary amplifier combination.
(Or a Death of Zen for the treble, similar to JLH.)
Active x/o should be based on contemporary 5532
op-amps, which surprisingly are still very difficult
to better with any real significance nowadays.
Quick modelling indicates the Seas bass driver
its well suited to a vented box of 42L tuned
to 35Hz (my sort of room friendly alignment).
Actively correcting the bass-mid to nominally the equivalent of 87dB
will give a lot of clipping headroom in the midrange, and the tweeter
run off 10-20w class A unattenuated at 91-92dB/W will also be fine.
For the cabinets read up on the BC1, and its clones, typically
front baffle 3/4" flooring garade chipboard, all sides 3/8" ply,
rear 1/2" ply. Cabinets edge battened and screw on front
and back. All sides and back bitumen damped. I'd also
do the front. Thickness the same on all I reckon.
Add a cross member to the baffle between the drivers.
Properly off set the tweeters in mirror image pairs.
(That isn't typical BBC style though ....)
rgds, sreten.
FWIW IMO building a classic BBC style 2 cuft speaker would
worthwhile and that Seas 8" mentioned by S7 would be on
the top of my list for such an endeavour.
The 35mm tweeter would not be, nor would the 34mm Audax.
Tweeters have come on leaps and bounds since the days
http://downloads.bbc.co.uk/rd/pubs/reports/1979-22.pdf
the above report was written, also see : TW034
Power handling, distortion and SPL of modern drivers
goes way beyond the drivers of 35 years ago and IMO
a 2cuft BBC style speaker would be very worthwhile.
Seas make some entirely suitable high quality modestly
priced 25mm dome tweeters that will do the job well :
http://www.seas.no/index.php?option=com_content&view=article&id=81&Itemid=105
http://www.seas.no/index.php?option=com_content&view=article&id=80&Itemid=104
The latter more suitable for the active route than the former.
Active arrangements like the LS 5/8 are very possible,
and a 405 for bassmid with a JLH10 for treble would
be a very nice contemporary amplifier combination.
(Or a Death of Zen for the treble, similar to JLH.)
Active x/o should be based on contemporary 5532
op-amps, which surprisingly are still very difficult
to better with any real significance nowadays.
Quick modelling indicates the Seas bass driver
its well suited to a vented box of 42L tuned
to 35Hz (my sort of room friendly alignment).
Actively correcting the bass-mid to nominally the equivalent of 87dB
will give a lot of clipping headroom in the midrange, and the tweeter
run off 10-20w class A unattenuated at 91-92dB/W will also be fine.
For the cabinets read up on the BC1, and its clones, typically
front baffle 3/4" flooring garade chipboard, all sides 3/8" ply,
rear 1/2" ply. Cabinets edge battened and screw on front
and back. All sides and back bitumen damped. I'd also
do the front. Thickness the same on all I reckon.
Add a cross member to the baffle between the drivers.
Properly off set the tweeters in mirror image pairs.
(That isn't typical BBC style though ....)
rgds, sreten.
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Those speakers has a baffle step that is at least one octave below all those deep narrowfaced moderns speakers with woofers consisting of two or three 5" or 6.5" woofers. This baffle step is also in the range were the most energy content is. For cabinet look on my "Dorspen" that is a Spendor inspirated design. Troed Gravesen DIY site also describe the BC 1 with its 12mm plywood cabinet no braces but lightweight bitumenloaded fibre board lamination
You will find this interesting I think, DrBoar.
It was always the BBC tradition to NOT time align drivers, but do flat baffle.
In fact the woofer was often recessed, as in this Harbeth model:
If you know your filters, you will know that 4th order acoustic Linkwitz-Riley should be time-aligned on the drivers' acoustic centres and WIRED IN PHASE for good lobing and phase alignment. So this arrangement really looks hopeless. But it isn't.
Interestingly, with real world filters (like second order electrical bass and third order electrical tweeter), if you move the tweeter half a wavelength forward, which is about 5cms at 3kHz, and WIRE OUT OF PHASE, you can get some very good phase alignment too. My PREDICTION would therefore be that your own splendid Dorspen speaker is wired out of phase. Along with the BBC LS3/5A and the Rogers LS5/9. And they ARE!
It was always the BBC tradition to NOT time align drivers, but do flat baffle.
In fact the woofer was often recessed, as in this Harbeth model:
An externally hosted image should be here but it was not working when we last tested it.
If you know your filters, you will know that 4th order acoustic Linkwitz-Riley should be time-aligned on the drivers' acoustic centres and WIRED IN PHASE for good lobing and phase alignment. So this arrangement really looks hopeless. But it isn't.
Interestingly, with real world filters (like second order electrical bass and third order electrical tweeter), if you move the tweeter half a wavelength forward, which is about 5cms at 3kHz, and WIRE OUT OF PHASE, you can get some very good phase alignment too. My PREDICTION would therefore be that your own splendid Dorspen speaker is wired out of phase. Along with the BBC LS3/5A and the Rogers LS5/9. And they ARE!
I feel the basic idea is to add some mass and damping to the sides and top and bottom of the cabinet.
I was lucky enough to be working with some acoustic engineers who were improving room acoustics. They laid down some stuff called Regupol stuck with aerosol carpet adhesive, made from old car tyres and glue if I understood correctly. They gave me a load of offcuts too.
It's about 1/4" thick and quite easy to apply. You then lay a thin wooden floor on top of it.
Must do the same thing really? Glue went everywhere though!
I was lucky enough to be working with some acoustic engineers who were improving room acoustics. They laid down some stuff called Regupol stuck with aerosol carpet adhesive, made from old car tyres and glue if I understood correctly. They gave me a load of offcuts too.
An externally hosted image should be here but it was not working when we last tested it.
It's about 1/4" thick and quite easy to apply. You then lay a thin wooden floor on top of it.
An externally hosted image should be here but it was not working when we last tested it.
Must do the same thing really? Glue went everywhere though!
There are serveral Regupol types according to the manufacturer:
Regupol | BSW Company Profile
Which is the one you use ?
Regupol | BSW Company Profile
Which is the one you use ?
Adding mass lowers the panel resonance. Adding bracing raises the panel resonances, but makes it harder to excite. Some mass treatments also do absorb some of the resonances ( conversion to heat).
I find well braced ( no panel larger than about 40 sq inches) lined with 1 inch OC 407 compressed FG t work well for me. It has been 30 years since I mixed undercoat and sand to mass load my boxes.
Look in the car audio suppliers. I have used a generic ( cheap) form of Dynamat in very small boxes.
I find well braced ( no panel larger than about 40 sq inches) lined with 1 inch OC 407 compressed FG t work well for me. It has been 30 years since I mixed undercoat and sand to mass load my boxes.
Look in the car audio suppliers. I have used a generic ( cheap) form of Dynamat in very small boxes.
I just have it because I was given some offcuts. So I really can't say it's the most suitable.
It looks like Cork and Rubber bonded together. I'd guess it's the Regupol K225:
Regupol Underfloor Impact Sound Insulation - BSW GmbH
Sorry I can't be more helpful. Just 1/4" thick rubbery stuff to me. I have doubled it up on occasion on the smaller top and bottom panels. The BBC did that on the LS3/5A.
Dear All,
Thank you for your advice and opinions so far. Everything said here (and, often by the same people, in other threads) certainly needs to be considered. I will have to calculate the WAF in to some degree as well.
Yesterday, I had the opportunity to "slam" one of those Audax TWO34 tweeters into a box and nothing could better demonstrate what tvrgeek and others said about loose experiments and advancing technology. Wasn't my idea, my friend Fred wanted to replace a blown 'pink' Wharfedale tweeter (in an old Dovedale 3 box). Cross-over at 5 KHz, 2nd order if I'm not mistaken. The lack of both balance and smoothness was remarkable, to say it politely. At least the hiss from that old tube amplifier was now clearly audible.
So, I realize I better do a lot of homework first, then invest my efforts in something not too deceiving. Maybe a BBC-style speaker, but not necessarily an active one along the lines of the LS5/8 (and I always had my doubts about the somewhat veiled, "behind the curtain" character of the Quad 405, even after refreshing it's circuits).
For now I'm tempted by the Seas offerings (also considering the Seas Mimir as an exercise, my son keeps requesting a reasonable speaker set while his girlfriend insists on a cabinet in the same colour as their walls), but I could also fall for one of Troels Gravesen's open baffles (tribute to Gilbert Briggs -- aah!, again suffering from nostalgia). Definitely low WAF, this one.
It's definitely going to be interesting. Thank you all so far for your valuable thoughts.
Thank you for your advice and opinions so far. Everything said here (and, often by the same people, in other threads) certainly needs to be considered. I will have to calculate the WAF in to some degree as well.
Yesterday, I had the opportunity to "slam" one of those Audax TWO34 tweeters into a box and nothing could better demonstrate what tvrgeek and others said about loose experiments and advancing technology. Wasn't my idea, my friend Fred wanted to replace a blown 'pink' Wharfedale tweeter (in an old Dovedale 3 box). Cross-over at 5 KHz, 2nd order if I'm not mistaken. The lack of both balance and smoothness was remarkable, to say it politely. At least the hiss from that old tube amplifier was now clearly audible.
So, I realize I better do a lot of homework first, then invest my efforts in something not too deceiving. Maybe a BBC-style speaker, but not necessarily an active one along the lines of the LS5/8 (and I always had my doubts about the somewhat veiled, "behind the curtain" character of the Quad 405, even after refreshing it's circuits).
For now I'm tempted by the Seas offerings (also considering the Seas Mimir as an exercise, my son keeps requesting a reasonable speaker set while his girlfriend insists on a cabinet in the same colour as their walls), but I could also fall for one of Troels Gravesen's open baffles (tribute to Gilbert Briggs -- aah!, again suffering from nostalgia). Definitely low WAF, this one.
It's definitely going to be interesting. Thank you all so far for your valuable thoughts.
Just heard a pair of the LS5/8s in Lodgesound's reel to reel tape recorder room at the Hifi wigwam show. I am of course perplexed and troubled (by all that 70s/80s opamp electronics and retro plastic drivers etc) but they did sound good, and some including myself would say they were one of the better sounds at the show…
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