The Quad thread

[JimL]

I published the design for this subwoofer in Speaker Builder 6/89.  Briefly, the Hartley has a Qts = 1.3 and Fs = 28 Hz.  The baffle is calculated to roll-off below 100 Hz or so, but because of the boost with the Qts = 1.3 (maximally flat being Q = 0.7), the EQ boost starts at 80 Hz, rising down to 20 Hz, which gives a relatively flat overall response down to 28 Hz.  I also put in a 12 dB/octave roll-off below 14 Hz.  For the last few years I have also used a Symmetrix parametric equalizer with an Infinity R.A.B.O.S kit to get a frequency response of +/- 2 dB between 20 and 60 Hz. 

 

For the bass crossover I used a 24 dB/octave Linkwitz-Riley roll-off above 60 Hz, using TL075 and 4136 quad op amps. For the Quads I used a 6 dB/octave passive RC filter at 60 Hz, which in combination with the 18 dB roll-off of the Quads gives roughly a Linkwitz-Riley 24/octave crossover.  

[Craig Sawyers]

Sounds very nice indeed.  It is only when you listen to dipole subs you realise how boxy conventional speakers sound.  Currently using dipole everything http://www.linkwitzlab.com/LX521/Description.htm .

[Pars]

Is that your quote on this page Craig?

http://www.magiclx521.com/

These seem interesting; I'd love to hear some sometime.

[luvdunhill]

I published the design for this subwoofer in Speaker Builder 6/89.  Briefly, the Hartley has a Qts = 1.3 and Fs = 28 Hz.  The baffle is calculated to roll-off below 100 Hz or so, but because of the boost with the Qts = 1.3 (maximally flat being Q = 0.7), the EQ boost starts at 80 Hz, rising down to 20 Hz, which gives a relatively flat overall response down to 28 Hz.  I also put in a 12 dB/octave roll-off below 14 Hz.  For the last few years I have also used a Symmetrix parametric equalizer with an Infinity R.A.B.O.S kit to get a frequency response of +/- 2 dB between 20 and 60 Hz. 

 

For the bass crossover I used a 24 dB/octave Linkwitz-Riley roll-off above 60 Hz, using TL075 and 4136 quad op amps. For the Quads I used a 6 dB/octave passive RC filter at 60 Hz, which in combination with the 18 dB roll-off of the Quads gives roughly a Linkwitz-Riley 24/octave crossover.  

JimL: I am working on a project that you might be able to teach me a good deal on. If I sent you a "dumb question" or two and a large LTSpice schematic and some beer money, could you see if you could enlighten me a bit on why I have DC offset the world's most complex active crossover circuit?

[Craig Sawyers]

15 hours ago, Pars said:

Is that your quote on this page Craig?

http://www.magiclx521.com/

These seem interesting; I'd love to hear some sometime.

Yup.  In fact the pair I built (starting with sheets of baltic birch ply) are the fifth pair down http://www.linkwitzlab.com/LX521/PhotoGallery.htm .

Because they are pretty expensive to build (by the time you have the drivers, crossover and power amps) there is a thread here http://oplug-support.org/viewtopic.php?f=28&t=2787 that is people seeking auditions.  Because there are now many hundreds (or even thousands) of pairs worldwide it is usually possible to find someone within striking distance so you can get a listen.

In a shoot out between the LX521's and the LXmini http://www.linkwitzlab.com/LXmini/Introduction.htm that I did a week or so ago, the conclusion was that the mini sounded a little more forward and clearly lacking bass by comparison with the 521 - but the imaging was astounding.  The advantage of the mini is that they are not only smaller, but a factor of several cheaper.  This is the physical comparison and the comparative in-room response of L and R for both the LXmini and LX521 at the listening position (equilateral triangle).  Frequency response irregularities at low frequency are room resonances.

 

LXmini frequency response and LR match

LX521 and LR match

Edited November 23, 2015 by Craig Sawyers

[JimL]

One clarification on my last post, the Speaker Builder issue that I published my article in was the 6th issue of 1989, corresponding to Nov/Dec.

 

luvdunhill, I'd be happy to take a look at the schematic.  If it's that complex, I assume you have electronic bits scattered all through it.  I assume you checked the offset in the interim electronic bits?

[lkong]

Scored a pair from a local collector.

 

[spritzer]

Nice!!!   

A word of warning, those stands have been reported to be very, very bad for the speakers so super careful when moving them. 

[Craig Sawyers]

I had a pair of 57's on stands - and my wife knocked one over.  It was saved from damage by the speaker cable, but the super expensive silver connectors got trashed.

But those 63's were responsible for my obsession with high end audio - visited a room at the Heathrow show in the early days of Meridian when they were importers of Mark Levinson.  Meridian CD player into dual mono ML pre, class A power into a pair of 63's on stands.  Brothers in Arms was playing - and it sounded so completely different to what I was used to hearing.  I left that room determined to aspire to that sort of sound quality.  Little did I know where that go....

[Hopstretch]

Has anyone tried Quads in a near field application? Guess I'd need a bigger desk ...

[sorenb]

why not bolt a pair and use it as the desk ...

[spritzer]

5 hours ago, Craig Sawyers said:

I had a pair of 57's on stands - and my wife knocked one over.  It was saved from damage by the speaker cable, but the super expensive silver connectors got trashed.

But those 63's were responsible for my obsession with high end audio - visited a room at the Heathrow show in the early days of Meridian when they were importers of Mark Levinson.  Meridian CD player into dual mono ML pre, class A power into a pair of 63's on stands.  Brothers in Arms was playing - and it sounded so completely different to what I was used to hearing.  I left that room determined to aspire to that sort of sound quality.  Little did I know where that go....

On this note, I just bought a ML-2/JC-3 clone from China.  Stereo amp but just 500$ delivered so it will be a nice platform to build something nice.  I also got a JC-2 preamp (150$ shipped) which I'll completely gut and put some of our circuits in there. 

[Dusty Chalk]

1 hour ago, Hopstretch said:

Has anyone tried Quads in a near field application? Guess I'd need a bigger desk ...

I believe Duggeh had a pair in nearfield (I.E. right on the other side of the desk) for a while.  He seemed quite happy with the setup.

[Craig Sawyers]

The JC-2 is a nice box for sure to put something in.  Has a nice two gang Penny & Giles pot in there too.

[spritzer]

Ahh it's a JC-2 clone as well.  One like this:

http://www.ebay.com/itm/2016-Finished-JC2-preamplifier-with-R-core-transformer-ALPS-potentiometer-CL-166-/111581666488?hash=item19fac91cb8:g:n7EAAOSwy4hUSNB6

The real one goes for way too much these days. 

[Craig Sawyers]

Aha - I thought you had struck lucky!  The one I'd like to get my paws on is the Vendetta phono stage.....hey, maybe it is cloneable.....

[spritzer]

We can clone anything...    Well that and make it better than the original. 

[Dusty Chalk]

5 minutes ago, spritzer said:

We can clone anything...    Well that and make it better than the original. 

So you're OSI?

[spritzer]

No comment...   

[lkong]

I've been toying the idea of using minidsp or hypex dclp to integrate a (pair) of sub into the system. E.g. http://www.rythmikaudio.com/GRci.html 12" OB baffle 

Any recommendations?

[Craig Sawyers]

The miniDSP's seems to be well thought of, and astonishing value form money for the 2x4 (available either single ended or balanced), which is all you will need to integrate subs with whatever.  The miniDSP range are the ones that Linkwitz now uses for all his current speaker designs - he has discontinued support for the analog active crossovers.

I don't know what the Hypex one is like, but their class D power amps seem to have a strong following.

[bjarnetv]

I would stay away from hypex dclp.

There was a group buy here in Norway, and many lost their magic smoke for no reason.

Hypex haven't been much help in solving the issues as far as i can understand.

The software is also quite bad.

 

I used a 2x4 when integrating dipole woofers with my esl63's and that worked great.

GR servo subs are supposed to be quite good, and i was tempted to buy some a few years back, but shipping to Norway was too expensive.

Right now i am using a DIY LAB12 Tapped Horn sub and 4x10HD with my dipoles, and if you have the space it's a pretty good solution.

Easy to integrate, and very effortless big sound.

 

[lkong]

3 hours ago, bjarnetv said:

I would stay away from hypex dclp.

There was a group buy here in Norway, and many lost their magic smoke for no reason.

Hypex haven't been much help in solving the issues as far as i can understand.

The software is also quite bad.

 

I used a 2x4 when integrating dipole woofers with my esl63's and that worked great.

GR servo subs are supposed to be quite good, and i was tempted to buy some a few years back, but shipping to Norway was too expensive.

Right now i am using a DIY LAB12 Tapped Horn sub and 4x10HD with my dipoles, and if you have the space it's a pretty good solution.

Easy to integrate, and very effortless big sound.

 

I think minidsp 4x10HD will be sufficient if not overkill in this case.

Unfortunately being broke and living in the bay area I have to choose smaller subs.

 

Edited April 26, 2016 by lkong

[bjarnetv]

On 26.4.2016 at 0:54 AM, lkong said:

I think minidsp 4x10HD will be sufficient if not overkill in this case.

Unfortunately being broke and living in the bay area I have to choose smaller subs.

 

yeah, a 2x4HD should be sufficient for integrating some subs, but the 4x10HD is more future-proof

just think about the future possibilities!

subs from 20-80hz, some dipole woofers from 80-150 and then the esl63 on top of that 

my old setup of esl63's and 4x15" OB woofers crossed over with a 2x4

didn't go any deeper than 45hz, but it had lots of slam!

would have been perfect with the TH sub filling in the bottom (currently disguised as a bookshelf)

to bad i could never get the rebuilt ESL panels to operate reliably.

 

[mypasswordis]

Sad to hear about the ESL63s, what did you end up doing with them? My Acoustats are still going strong without any tinkering, which is honestly pretty surprising. Hvordan har du det?