I'd say that having heard the LS3/5a design in work, i wanted to replicate it. It does not necessarily need to be a perfect clone, but something that looks the same and sounds similar.
The hard part has already been done for me with the woofer notch filters, as the stirling broadcast woofer and crossover combo is designed and built to match the monacor driver not the B110. The HF section of the crossover is still set up for the T27 in that particular version, it might just require a bit of experimentation to get another tweeter to integrate with the rest. (the seas tweeter seemed like the ideal choice as i've used it in place of a T27 once already, it sounds excellent and it is cheaper than most others.
I've tried to model the speaker in boxsim but even with the kef original drivers and the original crossover i can't get a plot anything like the ones i've seen for the design, so either i've made an error drawing up the crossover or boxsim doesn't like how complicated it is. (probably an error on my part as i had difficulty fitting the x-over into the design window)
The hard part has already been done for me with the woofer notch filters, as the stirling broadcast woofer and crossover combo is designed and built to match the monacor driver not the B110. The HF section of the crossover is still set up for the T27 in that particular version, it might just require a bit of experimentation to get another tweeter to integrate with the rest. (the seas tweeter seemed like the ideal choice as i've used it in place of a T27 once already, it sounds excellent and it is cheaper than most others.
I've tried to model the speaker in boxsim but even with the kef original drivers and the original crossover i can't get a plot anything like the ones i've seen for the design, so either i've made an error drawing up the crossover or boxsim doesn't like how complicated it is. (probably an error on my part as i had difficulty fitting the x-over into the design window)
I think then the pair I listened to must have been faulty or old and tired, to me they sounded thin and reedy with practically no bass. seeing how they were originally used in small vehicles the lack of bass would not have been noticed too much.
Possibly too I was already conditioned to big R&R speakers with the typically big hump in bass response, but at the time my home listeners were IMF compacts with a B-110 as the midrange ( or they were until my drunken sister blew them up)
Possibly too I was already conditioned to big R&R speakers with the typically big hump in bass response, but at the time my home listeners were IMF compacts with a B-110 as the midrange ( or they were until my drunken sister blew them up)
Missed this post (took me to the one about wilmslow aduio), this is the plan, but so far i've not even managed to get a decent simulation with boxsim using all original parts, so i must be doing something wrong. (it simulated my chorale design ok so i at least know that i can use it properly)
Moondog55, can't say for sure how good they really are as i've listened to harbeth's modern version of the original. I've never listened to a true LS3/5a, but i imagine it isn't going to be far off seeing as the BBC now use the harbeths. Opinions do seem to be quite divided as my dad doesn't like them and also refers to them as thin (but he has ditton 25's which like to shake the house) They have 6 of them in work, 2 of them in a small room and 4 in a gallery which is a long thin room. The LF is surprisingly good, even in the gallery. (there is a dividing panel between the sound and vision sections, with a pair of speakers in each section) My room where they would be is only 2.8M x 2.7M. (slightly smaller than the small room in work)
The LS3/5A is a specialised speaker for voice reproduction in broadcast vans.
The Continuum is very close.
The Arpeggio with the Fostex driver (see the projects on this forum) is another one that can replace it.
Don't even try to mimic it yourself with drivers etc, you finish spending much more with experimenting than buying a kit.
You are in the UK - see if you can score on eBay the Kef 101 or a KEF constructor series CS1 or CS1A, all three very close to the LS3/5A (I prefer the CS1 above the LS3/5A) for a lot less money. Althernatively consider this: trying to sell something even as the Kef CS1 brings in less money than that the drivers on their own are worth - guess what happens a lot?
As with anything you may look at it differently: total cost of ownership. You can buy something like the drivers for the Continuum and put it together all yourself and spend how much? Or you can buy a modern Harbeth version of the LS3/5A. The 10 years down the track you can still sell the Harbeth for a respectable figure whereas your homebuilt brings in next to nothing. How much is the cost per year?
At this moment I like my metronomes with the FF125WK better than the KEF CS1 (my daughter has them). Cheaper and easier - no hard work with a crossover.
The Continuum is very close.
The Arpeggio with the Fostex driver (see the projects on this forum) is another one that can replace it.
Don't even try to mimic it yourself with drivers etc, you finish spending much more with experimenting than buying a kit.
You are in the UK - see if you can score on eBay the Kef 101 or a KEF constructor series CS1 or CS1A, all three very close to the LS3/5A (I prefer the CS1 above the LS3/5A) for a lot less money. Althernatively consider this: trying to sell something even as the Kef CS1 brings in less money than that the drivers on their own are worth - guess what happens a lot?
As with anything you may look at it differently: total cost of ownership. You can buy something like the drivers for the Continuum and put it together all yourself and spend how much? Or you can buy a modern Harbeth version of the LS3/5A. The 10 years down the track you can still sell the Harbeth for a respectable figure whereas your homebuilt brings in next to nothing. How much is the cost per year?
At this moment I like my metronomes with the FF125WK better than the KEF CS1 (my daughter has them). Cheaper and easier - no hard work with a crossover.
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Had a fiddle with the inductor resistance values in boxsim which seems to have sorted the problems i was seeing. (don't know the actual resistance values so i've put in values that seemed to iron out the response) All the other component values are original.
I've added the -3.5dB L-pad to the tweeter. (I've now summed the adjustable tweeter attenuation so it takes up less space)
I've attached the response plot i get with the crossover design above.
I've added the -3.5dB L-pad to the tweeter. (I've now summed the adjustable tweeter attenuation so it takes up less space)
I've attached the response plot i get with the crossover design above.
Attachments
Kei, your sim isn't right at all. The two 6.8uF caps in the bass trap are shorted out as it stands. 
What you've got there is a bass trap (1.059kHz RLC: 15.8uF, 1.43mH, 16.5 ohm) on a second order with about 2.53mH total bafflestep. Notice the 9uF rolloff capacitor has 2.2 ohm resistor to avoid peakiness.
Alan Yates' Laboratory - VK2ZAY's Engineering Calculators - LCR Resonance
The tweeter is third order with a pad and a 2.2uF/8.2 ohm Zobel impedance correction. In fact a modern ferrofluid tweeter really shouldn't need the Zobel in the presence of a shunt resistance of low value around 8 ohms. FWIW, I found second order tweeter actually worked best on phase here. I simmed a nearfield (standmounter) response on a paper bass/dome tweeter, and the last phase response is second order filter where you just lose the second 27uF tweeter capacitor. I'd say that is using all the BBC techniques on the filter.
All that remains is the light damped plywood box with screws holding the front baffle and light battening and you've got a BBC derived Spendor or Harbeth! OK, I didn't use polypropylene bass, but the W130S IS lowish inductance at 0.6mH.
What you've got there is a bass trap (1.059kHz RLC: 15.8uF, 1.43mH, 16.5 ohm) on a second order with about 2.53mH total bafflestep. Notice the 9uF rolloff capacitor has 2.2 ohm resistor to avoid peakiness.
Alan Yates' Laboratory - VK2ZAY's Engineering Calculators - LCR Resonance
The tweeter is third order with a pad and a 2.2uF/8.2 ohm Zobel impedance correction. In fact a modern ferrofluid tweeter really shouldn't need the Zobel in the presence of a shunt resistance of low value around 8 ohms. FWIW, I found second order tweeter actually worked best on phase here. I simmed a nearfield (standmounter) response on a paper bass/dome tweeter, and the last phase response is second order filter where you just lose the second 27uF tweeter capacitor. I'd say that is using all the BBC techniques on the filter.
All that remains is the light damped plywood box with screws holding the front baffle and light battening and you've got a BBC derived Spendor or Harbeth! OK, I didn't use polypropylene bass, but the W130S IS lowish inductance at 0.6mH.
An externally hosted image should be here but it was not working when we last tested it.
Attachments
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I've re-done the sim with just a single L, C & R value based on your info, steve and it doesn't work quite as well, but i know that the values in the crossover are not right anyhow as stirling have adjusted their crossover to suit the monacor SPH-135AD woofer that i'm modelling with. What we do know is that the woofer section is correct for the woofer that i'd be using, i'm just modelling the lot to get an approximate idea of how the tweeter will integrate with the rest of the system. The crossover integrates + & - 1dB adjustments with 0.5dB steps to make fine changes. Problem is, I'd have to build it and listen to it in order to get a good idea as to whether it really works or not.
Changing the values to this seems to flatten out the response again. I've attached a schematic of the changes. Increasing the 9uF rolloff capacitor to 12uF drops the small peak at 2.5-3k back inline, but i've left it as is.
Changing the values to this seems to flatten out the response again. I've attached a schematic of the changes. Increasing the 9uF rolloff capacitor to 12uF drops the small peak at 2.5-3k back inline, but i've left it as is.
Attachments
Doug (brisso57),
Interesting option to go active
Thanks in advance
Regards,
Michiel
Hi Michiel
I was proposing an option. I haven't actually done it.
cheers
Doug
I'll suspend my disbelief that this can be done at all while sharing some investigations of a modern equivalent of the LS3/5A. Problem as I see it is you need accurate modelling files of the Monacor SPH-135/AD and SEAS 22TFF to get an accurate result.
The Spendor SA1 is a good place to start. This is light years ahead of the LS3/5a in driver technology with a crossover at 4.8kHz and a polypropylene rather than bextrene driver. But has the same sealed plywood cabinet style, and by luck uses your SEAS 22TFF tweeter. By the look of it, it doesn't need the bass trap and looks like simple 2nd/3rd order filter. FWIW, the bass driver looks like a SEAS special not dissimilar to the U16RCY/P . If you want to read how GOOD this little SA1 is, here you go:
6moons.com audio reviews: System Review 2
I enclose a picture of the original LS3/5A, a Spendor SA1 and its drivers and very lightweight cabinet construction. Bear in mind the LS3/5A had all the adjustments because it was built to a tight BBC studio spec. Hardly necessary these days. The cabinet is interesting too. I think it becomes almost aperiodic at low frequency with its ability to flex in a damped way.
The Spendor SA1 is a good place to start. This is light years ahead of the LS3/5a in driver technology with a crossover at 4.8kHz and a polypropylene rather than bextrene driver. But has the same sealed plywood cabinet style, and by luck uses your SEAS 22TFF tweeter. By the look of it, it doesn't need the bass trap and looks like simple 2nd/3rd order filter. FWIW, the bass driver looks like a SEAS special not dissimilar to the U16RCY/P . If you want to read how GOOD this little SA1 is, here you go:
6moons.com audio reviews: System Review 2
I enclose a picture of the original LS3/5A, a Spendor SA1 and its drivers and very lightweight cabinet construction. Bear in mind the LS3/5A had all the adjustments because it was built to a tight BBC studio spec. Hardly necessary these days. The cabinet is interesting too. I think it becomes almost aperiodic at low frequency with its ability to flex in a damped way.
Attachments
Most of it was to ensure that any LS3/5A would work well with another model. I believe the tweeter was the worst offender for manufacturing tolerances. But I doubt it allows you to use entirely different tweeters.
I had a recall of an affordable polycone speaker that Troels did:
Peerless HDS PPB 830860
He's done the hard work on the bass notch. It uses the Peerless 830860 and Vifa XT25TG-30-04 in 8L reflex.
Peerless 830860 HDS 134 PPB MidWoofer Speaker
Peerless Vifa XT25TG30-04 Tweeter
I'd think you could damp the port with straws and add stuffing and damping for a more closed box sound too. Nice. Cheap too.
Spendor pride themselves in making their own midbass drivers.
FWIIW, when i recently restored a set of LS3/5A, a number of similar size single driver boxes outperformed them.
dave
Don't know why but there's something about the LS3/5a that i like. I don't really like modern speakers very much, something about the way they look. (i know i can style a cabinet how i like) I'm not after building one because of its reputation or the association with the BBC. Theoretically speaking i could build anything into the same cabinet provided it fits, but following the old design just seems easier as it'll all fit together nicely and is proven to work well. A lack of LF is of no concern as the speakers are likely to be used for a fair amount of speech rather than music which is what they were designed for. The chorales that i built are my music speakers.
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In Italy:
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
And in the last issue of Klang+Ton have a project called LS 5/19 that are a clone of the LS 3/5a:
Klang+Ton | Lautsprecher-Selbstbau fr HiFi, Heimkino und Beschallung
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
Audiocostruzioni - Il Portale dell'alta fedelt amatoriale
And in the last issue of Klang+Ton have a project called LS 5/19 that are a clone of the LS 3/5a:
Klang+Ton | Lautsprecher-Selbstbau fr HiFi, Heimkino und Beschallung
An externally hosted image should be here but it was not working when we last tested it.
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