Author Archive

The Jordan Watts loudspeaker sales brochure.

Saturday, August 2nd, 2008

I’m posting a copy of the sales brochure of the Jordan Watts loudspeaker company.  The module was first introduced at the Audio Fair at the Hotel Russel, Holborn, London in 1961.  It held a strong niche market, especially in the Far East for twenty years.


Here is a recording of an interview with Leslie Watts, conducted by Dr F. Mark Carter in 1976.

Here are the Thiel/Small parameters for an 8 ohm Jordan Watts Modular loudspeaker Mk II.

I have taken some photographs of the Jordan Watts module.

The module is an under slung driver with a very light aluminum cone, spun to form a geometric tractrix.  The moving mass is 6.5 Gm.

The module was available in 4, 8 and 16 ohm versions.  Most modules in existence are Mk II speakers.  The Mk II has a wide lossy foam surround, and the Mk III has a very thin rolled rubber surround.  The surrounds absorb the edge reflections.

The voice coil is suspended on three Beryllium cantilevers, two of which carry the signal to the voice coil.

The Jordan Watts module is a full range driver.  Despite the light cone, the Fs is 41 Hz.  These allows for a quite remarkable bass response, especially with transmission line loading.

There are no prominent break up modes.  The driver is a bend driver by design.   Response extends to 20 kHz with slight roll off above 6 kHz.  The driver does not need to be cut off via crossover.   All that is required to extend response is one capacitor and two resistors.

Power handling is 15 watts RMS and because of the powerful magnet sensitivity is 88.85 db 1 watt 1 meter.  If two 8 ohm drivers are used in parallel then sensitivity rises to 94.85 db 2.83 volts 1 meter.

If you look at the impedance curve you will note that there is a ripple at 275 Hz.  This is a resonance from the cantilever suspension.  There is a lower intensity ripple at the second harmonic of this resonance.  This results in some lack of clarity in the lower mid range.  The rest of the spectrum has an electrostatic like quality, but without the beaming.

I have built drivers for mid range use only that damps this resonance.

The biggest problem with the driver is limited power handling and therefore spl, together with frailty due to the very thin light cone.  It is easily oil canned by a sudden impulse.

The foam does not rot, and if used sensibly within their limits, they give years and years of trouble free service.


Saturday, July 19th, 2008

Here is a speaker design for novice builders.  I have called it NASP (Noob Audiophile Speaker).  It is built round the SEAS: –

29TFF/W (H1318) Fabric tweeter, price $43.9 each, and the Peerless PPB-6.5″ Polycone woofer PPB 830874.  This woofer is now renamed, so there is a discrepancy in the name on the simulations, however it is the same woofer. Price is $57.9.  The drivers are available from Madisound

This is a good beginner’s project.  The impedance is very uniform at 8 ohms and will be an easy load for ANY amp.

I designed this for an experienced builder for his brother in law to do his first project.  Results were highly favorable.

The crossover consists of a third order Butterworth low pass filter, formed by L2, L3 and C2.  The Zobel network that corrects the impedance rise, so the low pass filter can work correctly is formed by Req and Ce.  Rm, Cm and Lm can be omitted, they just flatten the impedance curve.

The high pass filter is a second order Linkwitz-Riley formed by C1 and L1.  Level matching is accomplished by the L-pad Rp1 and Rp2.

The crossover is nice and smooth.  Time and phase aberrations are minimal and very acceptable.

The box is a fourth order BB4 0.5 cu.ft. ported reflex enclosure.  The F3 is 51.5 Hz.  There is no ripple and QL is 7 so the bass will be tight without being over dry.  The box though small should be well braced.

Here are the pdf. files of the box and crossover.



Please note that this is a beginner’s project.   It should be straightforward to build.  All crossover parts can be obtained from Madisound.

The design, in order to have a very flat 8 ohm impedance curve, is not diffraction compensated.  In most rooms best results will be achieved of the speaker is not too far from room boundaries.

Sub woofer pdfs for JL Audio 8W7-3 and Kappa VQ perfect 10 VQ low and mid insert vented and other assorted sub drivers.

Wednesday, July 2nd, 2008

Here is the JL Audio 8W7-3 in vented alignment. JL Audio 8W7-3 vented sub

Here is the Infinity Kappa Perfect 10 VQ low insert vented alignment

Here is the Infinity Kappa Perfect 10 VQ mid Q insert vented alignment

Infinity kappa Perfect 12 VQ low insert vented.

Infinity kappa Perfect 12 low Vq slot vent.

Infinity Kappa Perfect 12 VQ mid insert vented.

Infinity Kappa Perfect 12 no insert sealed

The JL audio 8W7-3 is very promising and so is the Infinity Kappa Perfect  10 VQ with the mid Q insert.

The Kappa perfect 12 VQ mid insert vented is the king of the hill.  After that the JL 8W7-3 just beats out the Kappa perfect 10 VQ mid insert vented.

The Kappa perfect 12 VQ low insert vented is also a very respectable sub, and you can get away without a slot vent.

The sealed 12 VQ is also respectable, but ideally should have a little EQ in the last octave, (12db) which will require more power and limit total acoustic output.

As the Kappa 12 VQ is NLA here are the optimal sealed and vented alignments for the Creative solutions Trio 12.

Creative Solutions Trio 12 sealed.

Creative solutions Trio 12 Vented optimal box.

I’m have added data on the Dayton RSS315HF-4 12.  This driver could make an impressive sub.  However the unit requires a large volume enclosure, around  5 cu.ft.  This driver is not suitable for sealed alignment, as the F3 is in the mid forties, well above sub range.

Here is the modeling for the Dayton RSS315HF-4 12 with slot Vent.


Here is the dayton-rss315hf-4-12 in sealed alignment.

Because of the problem of discontinued drivers I have done a couple of isobaric designs for the above driver.  The first is a box around 4 cu.ft. suggested  by WmAx (Chris).  Note that bracing and the volume of the isobarik driver tunnel is not allowed for.  I would think this would add a cu. ft. or more to the total volume.  There is a small amount of ripple.

Here is a smaller enclosure of under 2 cu. ft. for these drivers in Isobarik configuration.  I suspect that the volume of the tunnel, volume displaced by the rear driver and bracing will come pretty close to doubling enclosure volume.  So the final volume I suspect would be around 3 cu. ft.

I have been asked to add three more sub drivers.

First the Dayton RSS390HF-4 15? in an enclosure ported with a slot vent.

This is not very promising as it requires an impractically large enclosure.  The final volume of this enclosure would be around 10 cu.ft.  Obviously this driver is intended for sealed cabinets.

Here is this driver in an optimal sealed enclosure.

This is actually quite a good sub and would require 12db per octave boost Eq starting at 40 Hz.

Here us the Dayton RSS 390HF-4 in a vented Isobarik configuration.  This requires two drivers and halved VAS so enclosure size is halved as far a tuning volume, but additional volume will be required for the speaker tunnel, so Vt will not be reduced by 50%.

Here is a capable driver the Dayton Titanic 320C-4.  It is primarily intended to be in a sealed enclosure.  It has sufficient xmax to tolerate some Eq.  It would require 12 db per octave starting at 50 Hz, with second order bass filter 12 db per octave at 25 Hz.

Here is the sealed alignment of the Dayton Titanic 320C-4

This driver can be ported.  It requires a large enclosure and a long port.  The tuning volume is 5 cu.ft, port and driver add around a cu. ft. Damping is included in Vt but brace and amp volume will have to be added.

Here is the vented alignment of the Dayton Titanic 320C-4

Second we have the Shiva-x 12? in an enclosure ported with a slot vent.

It is clear that this driver is also primarily intended for a sealed enclosure.  However Vb is 6 cu.ft. so this sub could be built, and the F3 is 17 Hz!  The vent resonance is a very acceptable 160 Hz.

This Shiva-X 12? is also an excellent sealed sub.

Again this sub would require Eq, starting a boost at 12db/octave starting at around 40 Hz.

Now the cheapest of the bunch.  The Torrent XO-12 DVC, first in a ported enclosure with slot vent.

The enclosure size is a very acceptable 3 cu.ft.  The F3 is 24 Hz, however I consider any f3 below 25 Hz acceptable.  The vent is on the long side at 50.6 inches.  It will fit round the sides of the cabinet, and will require a couple of turns.  The vent resonance is 130 Hz, so the crossover should be no higher than 80Hz with fourth order slope.

The Torrent XO-12 DVC in an optimal 1.5 cu.ft sealed enclosure.

The F3 is 58.5 Hz.  In my view this is only suitable for car use.  For HT it would need a boost of 12db/octave starting at 60 Hz.  So this would consume a lot of amplifier power and limit deep bass acoustic output.

I think of these three the most promising are the Shiva unit sealed or vented, and the Torrent vented.  For the individual seeking advice, since he will be in dorms I would recommend building the Torrent vented enclosure.  That is also the most cost effective (cheapest).

Here is a pdf for the old Infinity Kappa perfect 12.1 single voice coil 4 ohm subwoofer driver.

I have now added a vented alignment for the Infinity Kappa perfect 10.1

IDMAX Car Sub: –

This seems a potent sub, even if it requires a large cabinet.

This is the model for the 6/8 ohm IDMAX

A new driver has come to my attention, the Lambda acoustics AV-15-H    Price $229 each.  This 15″ aluminum coned driver on face value does not look promising.  Conventional sealed and ported alignments give F3 of 70 and 45 Hz respectively.

However a passive radiator the PR18-1600 is available for this driver.  Two are required at a cost of $100 each.  So the cost of the driver and radiators is $429.

In an enclosure of 5 cu. ft. volume, Vb, the following response curves have been simulated.

Broad ripple of 4 db starts at 50 Hz.  In the range below 50 Hz 4 db of driver sensitivity is sacrificed.  There is slight ripple below 27 Hz.  As is typical of passive radiator systems response falls rapidly just above the tuning frequency of 18 Hz.  Until then cone displacement is well controlled.  QL is an acceptable 6.854, so bass should be reasonably tight, however time delay is off the chart.  An spl os 118 db is achievable.

The web site does not explain that for this driver to be a subwoofer, the use of the passive radiators is mandatory.  That seems obtuse.

The companion AV 15-X requires a 10 cu.ft enclosure.  This driver has more promising T/S parameters, with optimal Qts for ported enclosures.

This is the modeling of this driver in a 10 cu. ft. cabinet with a 6? X 16? X 49? slot vent.  This gets the vent velocity to an acceptable 10 m/sec.

This alignment produces an F3 of 21 Hz without ripple.

With use of the two passive radiators, response can be extended to 15 Hz.  However this comes at the expense of 5 db spl and ripple.

You can also use a suboptimal slot vent, of 2″ x 15″ x 33.5″.  This gives these responses.

Now you can see there is no free lunch.  The F3 of a driver really does determine the low frequency extension of a driver within three Hz or so.

The optimally tuned box has an F3 of 21 Hz.  The vent that appears to give an extended response is an illusion.  There is roll off below 100 Hz with an f3 of 44 Hz.  this is gradual until 16 Hz.  However the output of the two is virtually identical at 16 Hz.  However the optimal tuning has 6 db greater output at 21 Hz.

To help a member I’m adding another sub: – the JL audio 10W1V24.  This makes a nice sub, with no ripple and an F3 around 22Hz in a box of only 2.5 cu.ft.

I’m adding some alignments for the ACI SV 10.  Here are three alignments.  The 4″ dia. tube vent is too small.

First two drivers vented optimal box.

Two drivers 2.85 cu.ft. box vented.

Same box as above with 4? dia vent that is too small.

Two drivers sealed, optimal box.

Here is the JL audio 12W3V3-4 in a sealed enclosure, which seems mainly aimed at the car audio market to be used in a small sealed box.

Here is the Infinity Kappa 12.1 in sealed alignment.

There has been an interest in the TC 2000 driver.  This is definitely a driver for sealed use.  The frequency response is not acceptable and the enclosure is large.

Here is the TC 2000 in the optimal sealed box of just over 1.6 Cu. ft.  Cone excursion is better controlled and spl with Eq will be greater.

Here is a car audio sub that has come to my attention.  The DLS Audio OA 12.  This makes a fairly decent sub.  F3 is a little on the high side, and power a little limited as xmax is only 9 mm.  An Fs of around 30 Hz can be achieved in a box of around 2.75 cu.ft. The driver displaces 0.14 cuft, which needs to be added.  Bracing and amp volume will also have to be added.  Two 3″ tube vents with one  end flared can  be used, with vent lengths of 14″.  Here is the vented model of the DLS Audio OA 12.

Now a couple of JL audio drivers.  Both of these are primarily intended for car audio use in small sealed enclosures.  Neither of the drivers has sufficient linear motion for substantial Eq, without limiting overall level.  Therefore for home HT use they need to be in ported boxes.  Both are limited to about 200 watss at 30 Hz because of xmax limitations.  However response is smooth with very useful spl of 114db.

First the JL Audio 10W3V3, in an optimal vented box.  A slot vent is required.  This makes a good sub with a modest footprint of around two and a half cubic feet, with F3 close to 20 Hz.  This is a very attractive sub.

As you can see the JL Audio 10W3V3 in a sealed enclosureis only suitable for car use.

Now the very low profile JL audio 13 TW 5 in an optimal vented box.   The F3 of the two drivers is comparable, but the 10W3V3 has 6db greater output at 15 Hz.  The footprint of the enclosure for this driver is also smaller.

In sealed alignment the JL Audio 13 TW 5 gives its optimal performance in a half cubic foot box.

Here is the alignment for the JL_Audio_12W7_vented

Here is the alignment for the JL Audio_12W7AE_ventedPro

Here is the alignment for the JL Audio 12W7AE sealed

These drivers are much better performers sealed.  This latter in a sealed box 1.5 cu.ft with Eq at 12 db peroctave starting at 60 Hz will be required.

These two drivers are really designed for a sealed alignment.  However if you are prepared to build the large enclosure and vent required they are good performers.

Here are the vented and sealed alignments for the DVC Infinity Reference 1262w driver sealed and vented.  This driver is a high Q driver and intended for sealed alignment.  It is another in a long line of “car thumper drivers.”  It’s sensitivity is 96 db 2.83 volts 1 meter, however with the VCs in parallel and a 2hom impedance it is only 86 db 1 watt 1 meter.  So it is quite an inefficient driver.  Here are the alignments.

Infinity Reference DVC 1262w_Sealed

Infinity Reference DVC 1262w_Vented

Here is a Patent for a so called ?embedded transmission? line sub.  This is a most disorganized rambling document.  When you cut through the drivel, this is actually a second order coupled cavity sub.  The so called “transmission line” is closed at both ends, so therefore is redundant and useless.  I have modeled this within the sparse TL specs provided.  The F3 is around 40 Hz, and roll off starts second order just above 60 Hz.  Roll off becomes fourth order below F3.  This is dressed up to look like something new, but it is not.  I do not think this worthy of a patent.

Here is a Dayton Audio RSS460HO-4 18 inch slot vent.  It is a big box, but makes a powerful sub.

Crossover Circuit

Tuesday, June 24th, 2008

Here is a circuit for you to look at.  NFM-1 crossover circuit

Here is the crossover and service manual for the JBL PRO III AW ts.pdfb

Barack Obama’s Speech on Race

Tuesday, March 18th, 2008

Here is a link to Barack Obama’s speech on race in America today:

John Edwards . . . This is what I’m talking about . . .

Sunday, February 17th, 2008

I mean, you just knew this was the kind of thing this guy was into:

CD Download of Grand Forks Master Chorale Concert May 1984

Friday, December 28th, 2007

This is a link to download a CD of a recording of the Grand Forks Master Chorale recorded at Holy Family Catholic Church, Grand Forks ND. on May 12, 1984.

Here is the order of works:

  1. Te Deum K. 141. W.A. Mozart.
  2. Vere Languores . Tomas Luis de Victoria
  3. Ave Maria. Tomas Luis de Victoria.
  4. O Heiland Reis Die Himmel auf. Johannes Brahms.
  5. Beautiful Saviour. F. Melius Christianson. Jane Solberg, alto.
  6. Magnificat. J.S. Bach.

The Grand Forks Master Chorale and Orchestra is conducted by Dr Terry Eder.

Donna Rohrer, soprano. Carol Irwin, mezzo soprano. Kathy Murphy, alto. Bradley Almquist, tenor. Paul Boese, baritone.

Original recording by Dr. F. Mark Carter for radio broadcast on KFJM FM. Digital re mastering and CD compilation by Dr. F. Mark Carter.

If you click on the hyperlink below, a zip file with the Flac encoded wav. files, cue file and instructions for burning the CD will download. You can also play theWav. files with a player that supports Flac such as Winamp. This is a large file and will take about 30 minutes or so to download depending on connection speed.

Here again is the hyperlink to the 1984 concert.

The Magnificat was recorded on a Revox A700, the other items on a bespoke Brenell Mk 610 with Brenell Stereo tape link. To make the edited analog master the tapes were played back on the Brenell Mk 610 and dubbed to the Revox A700 for razor blade editing. The tape was Ampex Grand Master running at 15 ips. DBX 1 noise reduction was used and there was no dynamic compression at any stage. I could just master this to CD using all the bits. The microphone was a Neumann SM 69 FET auditorium microphone. Subtle use was made of AKG microphones on the soloists. The Monitor loudspeakers were CARTER NFM-1. Two and a half way sealed enclosure with two Dynaudio W-75 EX and Dynaudio D 28.

Here is a picture of the Brenell 610 (link to gallery). It is the top brushed aluminum machine:

Here is a picture of the Revox A700:

Here is a picture of a CARTER NFm-1 loudspeaker.

Link to Peter Apps interview on BBC World Service.

Thursday, December 27th, 2007

Peter Apps is my nephew.  He was the corespondent for Reuters News Service in Sri Lanka.  He was badly injured covering the civil war there in September 2006.  Despite being rendered quadriplegic, without even arm or hand function, he has returned to work for Reuters.  Here is an interview he gave for BBC World Service “Outlook.”

Here is a link to Peter Apps BBC Interview.