SEAS projects
Copyright 2002-21 Troels Gravesen


Since I received the new W18NX003 drivers they'd been sitting in my CNO-25 speakers, so they were well broken in when I moved two of them to the CNO-4 cabs. I loved what they did in CNO-25, but it wasn't until the CNO-4 set-up that I could fully appreciate the qualities of this new driver. Installing the speakers in our living room I initially didn't think them as efficient as I had expected - only to find out I was playing them louder than normal! A very good sign of low distortion. The W18NX... has all the qualities I could ask for from a 6" driver. Utterly transparent and dynamic combined with an overall smooth response that doesn't make it selective on recordings, nor favour any musical genre.
Treble? I've had the question on some of my 1st order tweeter set-ups. Where's the tweeter? Is there really enough treble level because I can't "hear" the tweeter. No, we can't hear the tweeter, we only hear treble without phase distortion and the overall tuning as fairly linear. It can take some mental adjustment, because "1st order treble" sounds quite different to treble passed through any higher order crossover. Again, the T29 is a magnificent tweeter and does very well with 1st order filters.
With the BMS 12N630 driver in place and run by the powerful 500 watts Hypex 501 we have a full-blown full-range speaker delivering a solid foundation for all kinds of music.
There will be a fully passive options as I know some people will want this, but only for bi-amping. My recommendation is the Hypex FA501 to explore the CNO-4 to its full potential.


It's been quite a while since I last worked with the Nextel coated drivers from the SEAS EXCEL line - and I'd forgotten how good they are. I fact, I never heard how good they can be as my front gear is much better today that it was back then.
The W18NX001 driver is so smooth it can be run 1st order and my former 4th order series crossover did not fully reveal the potential of these drivers.
There will be three new CNO constructions, the CNO-mkIII, and up-date to the 2-way version, CNO-25-mkII and finally a new 3-way, CNO-GRANDE, from W18NX001 + W12CY003 + T29CF002. See below.


CNO-25-mkII is a logical extension of the virtues of CNO-mkIII. The extra midbass provides additional power handling and bass impact. Revised simple crossover and time-aligned drivers. Fitted with some of the best drivers from the SEAS EXCEL line of drivers and state of the art crossover components from Jantzen Audio.


CNO-GRANDE is the third speaker in a range of upgraded and new CNO constructions and icing of the cake from 2 x W18NX001 + W12CY003 + T29CF002. Amber-Z cap for the tweeter ensures absolut optimum performance from this SOTA tweeter. Edge-coated midrange driver ensures smooth and non-distorted midrange performance. 1st order crossover to midrange and tweeter.
The virtues of adding a small 4" midrange driver has been discussed in detail in the intro here.
The CNO speakers have been the best selling kits from the SEAS portfolio - and for good reasons. These nextel coated SEAS drivers just sounds great and have found their way into some serious high-end speakers as observed at the Munich High-End Show in recent years.

March 2015

Center speakers should be 3-ways! Many center speakers are made from the popular 2-way d'Appolito - and I've made a few myself - but from a center speaker we need a strong midrange projection and we need an even horizontal dispersion, something 3-ways are good at. We need everybody in a 4 seat sofa to get the same experience. The strong midrange projection makes understanding speech and vocals more easy and in this respect these center speakers are no different from the Classic 3-ways (SEAS and ScanSpeak) recently introduced. The same goes for Ekta, Ekta Grande, SP44, SP38, all featuring 2-4 inch midrange drivers. 

SEAS 3-Way-Classic mkII
August 2014


Given the size*, this is a speaker that might please a lot of people and annoy a few - if any! Smooth is what is - and efficient too. With a healthy 90-91 dB sensitivity it's 1-1 dB more sensitive compared to the mkI - and an easy load for even fairly low wattage tube amps. I recommend minimum 15-20 watts to get some of the dynamics. More power always means better grip on cones and better low-end punch. My 50 wpc GlowMaster KT88 loves it. If you never play very loud, 5-10 watts will obviously do too - in particular PP designs having better bass grip.

April 2014

Smooth when music is smooth, harsh when music is harsh. Read about the latest and best SEAS speaker I've ever made. 

SEAS CURV mini two-way
October 2012

Try out the un-coloured sound of woven PP.

Jenzen NEXT
October 2011


The Jenzen NEXT comes at roughly twice the price of the Jenzen SEAS ER kit, so what do we get for the money besides gorgeous looks of nextel coated drivers and silver phase plugs?
To my ears we get an overall more refined sound with reduced colouration and subjectively reduced distortion as these excel drivers can handle a bit more power before detail smearing becomes apparent. 
I was anxious to hear if NEXT would prove a significant step up compared to SEAS ER, and it did. It's smoother, it's more transparent, it's easier to listen to. The Superior Z caps do their thing for the midrange and the tweeter's Silver-Z cap is the icing on the cake. The cherry on the icing is the Crescendo tweeter and I'm almost sorry to say it does a bit better than the T25.

Jenzen SEAS ER
September 2011

The Jenzen series of speakers are meant to offer high-end sound for low-end price, even for the constructions to come with expensive drivers. As discussed in Speakers' Corner; what we diy people can do at modest price the speaker manufacturers cannot, is this: Spoil our drivers with the best of cabinetry. 
MDF is cheap and it's no problem making 30-50 mm panels, adding solid bracing to produce low-resonance enclosure that is often a significant part of high-priced speakers. I recall Eggleston speakers and the knuckle tap test suggests a solid log of wood. No problem. Laminate 2 x 22 MDF; add bracing and we have the same thing. And it pays off. Cabinet resonances add more to the sound than we may think.

The first speaker in the Jenzen series comes with modest priced drivers, yet delivers a significant soundstage. Size matters and using drivers with a decent membrane area means they don't have to move much. In particular for the midrange this is important and releasing it of the tedious task of pumping bass, things start developing. Drivers we may have found delivering harsh upper mids in the common two-way set-up may all of a sudden deliver crystal clear sound in all of the midrange.

April 2010

These SEAS CA18RNX drivers hold the classical coated paper cones, but here with a 39 mm voice coil former allowing greater power handling compared to CA18RLY's standard 1" voice coil. Overall frequency response is better for the CA18RLY, but despite a somewhat whobbly midrange they sound smooth, detailed and throw a punchy bass. Read more by clicking heading or image.

CNO-25, 2-way CNO
February 2009


Setting up the finished CNO-25 revealed a fully grown-up CNO. Sensitivity is increased by 4-5 decibels and the overall bottom end weight is significantly enhanced. Comparatively it goes louder with less distortion due to doubling the amount of bass drivers. Upper mid and treble is the same as for the CNO and this was what I wanted: Maintain CNO qualities, but increase power handling and bottom end capability.

CNO, revised Jan.09


These drivers were not only made to look good, but also to provide a sound clearly distinguishable from the average. High-end drivers built on classic virtues. As always we apply to the law of diminishing returns when we buy expensive stuff. Small improvements may cost small fortunes. I think these nextel units are the best sounding drivers SEAS has ever built.

A slightly modified crossover delivers an overall balanced sound that will suit any kind of source material. My absolute favourite 24 liter floorstander.

January 2009


The CNO mkII modified for SEAS T25C003 tweeter.

June 2008

Mini transmission line from
SEAS W15LY001 nextel midbass + Peerless HDS tweeter

If size matters, here is a neat mini-TL that will deliver potent bass,
highly transparent midrange and smooth balanced treble.
Construction made in collaboration with John Eekels/Holland.

Acapella NEXT
December 2007

Semi-dipole from state of the art drivers
SEAS W22NY001 + W18NX001 + T29CF001

My Autumn sale was a goodbye to my Acapella SEas speakers. Drivers, crossovers, vents, terminals, damping material, wires, everything but the cabs. You don't ship these caps to Portugal unless you make huge crates with loads of absorbent material. So, the cabs stayed and having the W18 and T29 drivers the only thing left to do was ordering the W22 bass units - and see if a fairly high efficient Acapella could be made. The W22 comes with a huge 134 mm magnet and promises 90 dB sensitivity. Not bad at all. Maybe the W18 could even be run without any attenuation.... So, the Acapella NEXT was born.
This is not a cheap speaker, but the quality of the mid and mid-tweeter integration is something special. Can be driven from even 20 watts SET.

SEAS 5INCH projects
December 2007

Three minis for every pocket from SEAS' 5" range of drivers, CA15RLY, W15CY001, W15LY001.
SEAS 19 mm 22TAF/G tweeter used.
Paper cones, nextel coated paper cones and magnesium cones.

Mini-mini with Nextel coated SEAS drivers
October 2007

This project is realised in collaboration with John Eekels, Holland.
John was asking for a substitute for the no longer available
and after some search we decided to give the new SEAS W12CY003 a try.
This driver features a classic paper cone with standard coating on the
rear and Nextel coating on the front, giving it a nice appearance as can be seen below.
I have previously done a two-way from SEAS CA18RLY+22TAF/G (not published) from which I've had some
good times, thus the SEAS 22TAF/G tweeter was the one I wanted to try out in this construction.

Poor Man's Strad
2006 project.

The "Poor Man's Stradivari" made from SEAS CA22RNX + MCA15RCY + slightly modified 27TFFC have been finished. Various tweeters (Vifa DX25TG and Scan-Speak D2905/9700) have been tried and the crossovers have been added to the website.
Having made an EXCEL version of this speaker (read below) I returned to the "paper" drivers and this is how it's going to be. They may not be as neutral as the EXCEL drivers but they just have "something". Sensitivity and transient attack to point out two things.
Feeding these speakers from my old Garrard 401/modified Rega RB300/Dynavector 10x5/Copland CTA 505 power amp provides lots of good moments and secondhand vinyl is available in truckloads for nothing these days. Click heading to go to PMS.
I have to say the PMS is a hit in terms of feedback from builders. A lot of people have had fun making 3D drawings of the cabs and I have feedback from 20+ people building the PMS. A few have reported back with
pics and comments and I hope to have some more photos of finished projects this year.

SEAS Classic 3-way
2006 project

The SEAS CA22 was tried in a classical 3-way and it turned out so well that I have launched the project. The MCA12 is doing excellent and provides a fine midrange with a wide dispersion and a speedy presentation that leaves most 6-7" midbass drivers behind. These paper-coned drivers take some burn-in before delivering the goods. The tweeter is the 27TFFC, an fine tweeter at a modest price. Sensitivity is 90 dB/2.8 volts and it's an easy load on the amplifier. The crossover is a simple 2nd order topology and the overall cost for drivers and crossover components is around 535 €. I have to admit I have had very little feedback on this speaker. I know that MDF cabs have very little appeal* and the classic cab is out of fashion. Maybe some gorgeous veneer would make a change. I'd pick this speaker any time over the 2.5 clone/Amish 45-95 and others.

*When I first launched the TJL in MDF test cabs there was absolutely no response at all. I then made a digitally manipulated image of the drivers in a very nice looking yew veneered cabinet - and then things started rolling. So, do we choose speakers by ear or eye?

TJL, 2-way floorstander
SEAS W18E001 + Fountek JP3
2002-3-4 project


The following project describes a 2-way floorstander slightly smaller than the 2.5 clone. Overall dimensions are: 19 x 98 x 26 cm (W x H x D). This project is targeting a better midrange, better treble, bass comparable to the 2.5 clone and a more moderate-sized cabinet. Well, can all these requirements be accomplished in a smaller-size construction? And from what drivers?
From the Point75 and Acapella projects, the use of the SEAS W18E-001 drivers seemed an obvious choice for a 2-way floorstander. The Fountek JP3 tweeter was chosen for treble, giving great results in the Acapella construction. What I also wanted to try in this construction was the use of a passive radiator, and SEAS provides suitable PRs for 6" drivers. Next to the PMS, the TJL2W is probably the most popular construction from these pages. And I would pick the TJL-T25 any time over the 2.5 clone. Same sensitivity, deep bass like the clone from an even smaller cab. The TJL is 556 € and the 2.95 "clone" is 478 € for al drivers at e.g.

TJL-3W, 3-way floorstander
SEAS W18E001 + W12CY001 + HIQUPHON OW1
2005 Project


I do think I've been writing quite a lot about the TJL 3-way. The experiences gained from the Ekta and Zahra made me even more anxious to get started. If the latter two constructions hadn't come along, I would have done the TJL3W a long time ago. But events took their own course and I have been pleased with the results of the former constructions and the TJL3W was very much next. The TJL is my favourite among a number of 2-way floorstanders and you always ask how to make a good thing better. The TJL shares the limitations of most other 6" + tweeter two-ways: Lack of dispersion in the upper midrange/lower treble due to the bass driver having to handle everything up into the treble area despite the low point of crossover around 2500 Hz. When a single driver has to pump the deep bass and at the same time handle the delicate upper midrange and lower treble there are limitations to the loudness we can expect from such a design. Suitable for most, but it can't play excessively loud. However, the TJL3W wasn't made to play excessively loud, rather to play low.
May 2006: Finally got the front panels finished. "Finished" may often mean another half year before the final oil rub. The OWI tweeter was the original set-up and so it ended. Now the front panels (solid cherry wood) only need some daylight to darken like the veneer. If you want deep bass and un-coloured sound from a modest sized speaker, take a look.
I do NOT consider the TJL3W a project for beginners.

Read full text and construction details on TJL3W

W17EX001 + Scan-Speak D2010/8513
2002 Project


This speaker, building on a well-known commercial floorstander, is an easy project in a modest 24 litre cabinet.
SEAS drivers no longer available.

Point75 (pdf file)
ScanSpeak 18W/8535 + SEAS W15CY001 + Expolinear NDRL81
2002-3 Project


Despite having a ScanSpeak bass driver, this construction is placed in the SEAS section due to the SEAS W15CY001 middriver and a later upgrade with an 8" SEAS alu driver.
The Point75A&B describes a loudspeaker project utilising the same Scan Speak 18W/8535 bass driver as used in the 2.5 clone project. A SEAS W15CY-001 magnesium midrange driver and an Expolinear NDRL81 aluminium ribbon tweeter complete the driver selection. Points of crossover are 300 and 3000 Hz. Main feature of this construction is the midrange working in dipole fashion, creating an impressive soundstage, and the ribbon tweeter with its weightless presentation of upper registers. The bass driver works in a 24 litre bass-reflex cabinet with a 28 Hz port tuning giving a more lean and well controlled bass compared to the 2.5 clone with its somewhat “one-note” bass presentation. Fine-tuning and “voicing” has taken considerably longer than expected due to the midrange working as dipole and the overall sound being a mix of direct and reflected sound. Furthermore, some easy tweaking of the ribbon tweeter was necessary to open up the sound and a minor equalisation to smooth the upper treble.
Download Point75A&B pdf file, 2.2 MB:

Point 75i, Point 75 upgrade


Point75A upgrade by using SEAS L22RN4X/P (H1208) for bass. Modified crossover. New construction can utilise Fountek JP3 or Aurum Cantus G2Si ribbons as well. Read up-grade of Point75A to Point75i

Acapella LT & LWJ (6 MB pdf file)


The aim of this project is to use the experience gained from the Point75 to produce a speaker with greater power handling and SPL capability. In other words, it has to be able to play loud - and retain all the qualities from the Point75. In addition to this, some more weight/warmth in the lower/middle midrange would be appreciated.
The 8535 bass driver is the limiting factor in the Point75 design, and in case you know the 2.5 clone you know how loud this one goes. A lot of drivers have been tested before settling on a range of drivers that eventually turned into three speaker constructions:
Acapella LT95:
SEAS L22RN4X, SEAS T17RE, Scan-Speak D2905/9500. Unfortunately the T17RE is no longer available.
Acapella LWJ
SEAS L22RN4X + SEAS W18EX001 + Fountek JP3

Download all Acapella files, 6 MB pdf

Acapella SE (3 MB pdf) and SEas (htm)
SEAS W22EX001 + SEAS W18EX001 + Fountek JP3 ribbon tweeter/SEAS T25

This is the speaker that is the steady back-bone in my hifi set-up. Not a particularly complicated speaker, a standard 3-way with an 8" bass driver working up to 350 Hz. A 6" midrange working from 350 to 2500 Hz and a ribbon tweeter taking over from here. Recently a SEAS T25 dome tweeter is taking the place in replacement of the ribbon. Some day I'll make a four-way of this construction just to hear if it is possible to fully integrate four drivers. Not an easy task. The ribbon version is a tolerable set-up where the T25 version has an extra 1-1 dB in the 1-3 kHz region providing a more forward presentation.

The Acapella SE is the result of almost one year's work on semi-dipoles and a lot of experience is build into this construction. Going from 120 wpc solid state to 50 wpc valve amplification during this period made an extra 2 dB sensitivity appear on the wish list and numerous 8" and 10" drivers have been through the simulation programme. There is no way around a larger cabinet if this wish has to be fulfilled with an equivalent bass extension. The SEAS W22EX001 with almost half the membrane weight compared to the L21/L22 and a 42 litre bass cabinet volume comes close to an extra 2 dB sensitivity and the Copland valve power amp is pleased I should tell.
I also wanted to make the cabinet from only 6 MDF outer panels, thus an overall increase in height to some 120 cm. The cabs are slim like the Point75 when seen from the side. All these changes meant a new 3rd order bass LP crossover section and reduced middriver and tweeter attenuation.
Drivers, drawings, crossover, pictures:
Download all Acapella files, 6 MB pdf
Download cab drawings here. 121 KB, zip file.


7.5 litre vented construction - a fabulous mini-monitor. This construction was made before I started my diy-loudspeaker website, and I never found the time to write anything about it. The drivers here are among my favourites and the W15CY001 drivers were acquired for the Point75 dipole speaker and the HIQUPHON OWI was bought only because I wanted to own a pair of these - probably - best ever made 19 mm domes. Some people find the OWI tweeter hard to find, but it's not. The OWI and other magnificient tweeters are made by Oskar Wroending here in Denmark and his website is here. You cab buy all types directly from Mr. Wroending or find a distributors list here.

W15CY001 + Fountek Neo3
2005 project

I recently had a pair the Fountek NeoCD3 ribbon tweeters and have compared them to the JP3 true alu-ribbon tweeters. The new tweeters have a ribbon made from laminated material and will probably be less fragile compared to the JP3 pure alu ribbons. The easiest way to try out the Neos was to set up a small monitor and the SEAS W15CY001 midbass was an obvious choice. You don't find a much better upper midrange and from a 7.5 litres cabinet you get a surprisingly deep bass. I also tried adding a subwoofer from two push-push Dynaudio 21W54s with a crossover around 60-70 Hz/12 dB and it worked fine.



One of my friends needed a mini for his home studio and I suggested the SEAS T14RCY having the XP membrane material giving an ear-friendly midrange with excellent transparency. The ScanSpeak D2010/8513 tweeter in this company is sweet and gently, nowhere near how it performed with the 18W/8535 driver in the 2.5 Clone. The 8513 tweeter must never be mated with an even slightly harsh midrange. An even better tweeter option may be the HIQUPHON OW1. The T14 is getting hard to find and a replacement system is planned from SEAS CA15RLY + 22TAF/G.

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