Any currently produced drivers for LS3/5A? - Page 2 - diyAudio
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Old 4th February 2012, 05:17 PM   #11
gfiandy is offline gfiandy  United Kingdom
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If you are interested the original white paper by the BBC is still available:

http://downloads.bbc.co.uk/rd/pubs/reports/1976-29.pdf

Before people believed speakers were a black art and data was actually published.

Regards,
Andrew
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Old 4th February 2012, 05:43 PM   #12
system7 is offline system7  United Kingdom
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I enjoy reading articles by BBC engineers, and studied that BBC LS3/5Aarticle in detail. They really know their stuff and apply a few old radio frequency techniques when appropriate. Morgan Jones was a BBC sound engineer, and his little Arpeggio loudspeaker is a masterclass in optimising a design for a high source impedance SET valve amp.
Arpeggio Loudspeaker

Modern is done very well by Troels Gravesen, and he tells you ALL about it:
DIY Loudspeaker Projects Troels Gravesen

The Vifa section is interesting for this affordable reflex mini speaker, for instance, albeit impedance plummets to 4 ohms at times:
Vifa PL14WJ-

Just bear in mind these tiny speakers are great on vocals, but really don't have much bass, though you could fiddle with that a bit.
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Old 4th February 2012, 08:34 PM   #13
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by fructose View Post
Any suggestions for a 2-way bookshelf for roughly under $1000 USD in parts?
Hi,

IMO the best 5"/1" design available is :
Zaph|Audio - ZD5 - Scan Speak 15W8530K00 and Vifa XT25

Note that high quality small speakers don't belong anywhere near bookshelves,
they must be stand mounted away from walls, consequently the floor standing
version makes a lot of sense given the cost of high quality good speaker stands.

Its not the highest value, but I reckon it is the best for a no sub set up.

One could go somewhat more OTT on the cabinets, depending on skills,
time, patience and cost. These two sites take cabinets very seriously :

DIY Loudspeaker Projects Troels Gravesen
Humble Homemade Hifi

A boat shaped cabinet is an obvious improvement to be made.
Maintaining the front baffle specifications as stated of course.

rgds, sreten.
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Last edited by sreten; 4th February 2012 at 08:36 PM.
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Old 4th February 2012, 09:07 PM   #14
Mr. dB is offline Mr. dB  United States
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Quote:
Originally Posted by system7 View Post

Modern is done very well by Troels Gravesen, and he tells you ALL about it:
DIY Loudspeaker Projects Troels Gravesen
Which, of the very many projects on Troels' site, are we looking for in the context of this thread?
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Old 4th February 2012, 10:07 PM   #15
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Originally Posted by sreten View Post

Why would you want to clone drivers, especially the B110
that have known issues and known consistency issues ?
Why would you build drivers you know you have to correct
in the x/o ? (This applies to most bextrene cone drivers.)
and why build drivers with low power handling ?

You can get 3/4" tweeters that easily outperform the T27.

Although it has a cult following, the LS3/5A is not a particularly
good domestic loudpeaker*,...

* for its cost.
i have a friend who always wanted a set of LS3/5A (his main speakers are a set of stacked quads, and his second srting areSpendor BC1 he bought new).

He bought a set from the local emporium, that turned out to have dented tweeter (with no covers), the wrong woofer, the wrong crossover, the wrong grills and not all the binding posts the same... the boxes and grill frames original.

I restored them, new tweeter (thanc Jeff), proper B110 (matched) and XOs from Falcon that i got in the UK. I had the proper grill material salvaged frm some Tangets, i swapped a set of working VIFA tweeters for a set of grills off of dead Celestion HF2000, and upgraded the binding posts.

Restored head to head against a set of mFonken, they trailed badly for domestic use (can'tcomment on their use in a BBC broadcast van). There are any number of my milliSize boxes that should be more suitable for the given use and at a fraction of the cost.And if i can do it, there have to be lots of other candidates for better value & performance, i'm sure many alteady linked qualify.

dave
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Old 4th February 2012, 11:09 PM   #16
gfiandy is offline gfiandy  United Kingdom
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If you liked the sound of the LS3/5A my guess would be that the Zaph Audio design would be more of a modern take on that than the MFonken (Which is based on a full range light weight driver). Zaph's designs are very well researched and it is well worth looking through his website to see his thought on speaker design.

But if you really liked the very controlled sound of the LS3/5A the kit from Sterling is probably the closest you will get with easily available parts.

Regards,
Andrew
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Old 5th February 2012, 07:12 AM   #17
system7 is offline system7  United Kingdom
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The LS3/5A was a tiny 5L of birchwood ply closed box, bringing the benefit of low distortion due to low cone excursion and an undemanding high load impedance. One of the things to consider is what you will be driving a modern clone with. Presumably a low output impedance transistor design. I see signs that the BBC design is optimised for this in the asymetric capacitor values in the high pass:

Click the image to open in full size.

Spendor builds opted for 1.5uf/0.3mH/5.03uf for C2/L3/C4 with a standard inductor in the 3rd. order highpass filter and a resistive pad on the tweeter. The autotransformer was a tricky item to build within spec. R3 of 82 ohm goes without the auto, it was just to stop a HF ringing.

The 500Hz baffle step compensation on the lowpass will actually slightly modify the values in the lowpass filter, but that is simply a matter for calculation using older radio techniques where source impedance is a consideration.

The Zobel network on the tweeter is something you can take or leave, it has little affect on the HP filter, but IMO smooths the HF performance. The R2/L2/C5 trap is rather specific to the peaky B110, and would be simplified on a modern design.

Where this is leading, is if you want to clone this design in a modern context, I'd say go infinite baffle with modern drivers. 2nd order with baffle step on the LP, 3rd. order on HP with attenuation pad and Zobel impedance matching. It would be fun to analyse that HP filter and see if it's nearer butterworth or bessel slope. But I'm not gonna do it, it's your baby!

I'd certainly use a bigger cabinet for a bit more real bass. Mainly deeper, keeping the same front dimensions.

Ooh, FWIW, that Zaph audio design has the weirdest bandstop filter on the treble and some highly specific total Vifa XT impedance matching. What's that all about? Good or just unusual?
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Old 5th February 2012, 07:41 AM   #18
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by system7 View Post
Ooh, FWIW, that Zaph audio design has the weirdest bandstop filter on the treble and some highly specific total Vifa XT impedance matching. What's that all about? Good or just unusual?
The delay circuit on the tweeter (XT25) of the ZD5? I don't like such circuit. If you had access to a lot of drivers, why not choose drivers combo that doesn't require complex filter? Best speaker always start with best matched drivers.
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Old 5th February 2012, 08:22 AM   #19
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by Jay View Post
The delay circuit on the tweeter (XT25) of the ZD5? I don't like such circuit. If you had access to a lot of drivers, why not choose drivers combo that doesn't require complex filter? Best speaker always start with best matched drivers.
Bit off-topic, but, a strange beast really!

Click the image to open in full size.

Zaph is introducing a midpass or midstop filter around 2kHz into the high pass element. L11, R12 and C10 are just correcting impedance for the Fs resonance at 500Hz, which is no bad thing, and will improve power handling. The midpass is a nice touch in 2nd order active filtering and might get you an overall allpass response with inevitable group delay, if you know your transfer functions which have 1, s and s^2 elements in the numerator and denominator where s is the midpass element, but must do HORRIBLE things to impedance and matching with non-ideal loads in passive filtering, which is why he's put 5 ohms at the HP input. Wouldn't fancy it myself, but will mull it over.

Last edited by system7; 5th February 2012 at 08:35 AM.
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Old 5th February 2012, 09:41 AM   #20
Jay is offline Jay  Indonesia
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Originally Posted by system7 View Post
Wouldn't fancy it myself, but will mull it over.
Imagine that if all out of phase response between woofer and tweeter can be solved using the delay circuit without ill effect, then it will make speaker designers life a lot easier. But I have tried it and decided not to use it. Prefer to find the in-phase response without the delay circuit.

Well, I know, a first order on the woofer will give a very good sound, and you may want to "sacrifice" the tweeter for that
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