The-Loudspeaker-4

Like the Ellipticor-28, what's below is my speaker diary over the last ~12 month constructing and fine-tuning this last speaker in the range of "The-Loudspeaker" speakers. There were no specific criteria for the range of "The-Loudspeaker" except that they were large - and well, kind of statement over the last 20 years of speaker building. I hope you enjoy!

Autumn 2025: As mentioned in my TL-5 file, The-Loudspeaker-4 was abandoned due to unavailability of the JBL 2123H midrange driver. No point in launching a speaker only a few could build. Also the intended JBL 15" bass driver was way off suggested specs.
So, the target here is really how do we get most of the TL-1-2-5 from a smaller footprint. Being more than happy with the performance of my Ellipticor-28 bass driver, why not try its larger sibling, the 32W/4878T01? This 4 Ohm version makes some 92 dB according to specs and with a little help from a Hypex FA501 we can boost the bottom end of ~94 dB. So, I ordered a pair.
To make it clear from the beginning: There will be no passive version of this speaker. Not possible.

For midrange a number of candidates came to mind, some new and some of them found here. One was the B&C 8PE21-8. I could have chosen this one for The-Loudspeaker-3 being in a tie with 18 SOUND 8NMB420 driver. Initially I used the 8 Ohm version, but later ordered a pair of 8PE21-16 to try that out. The 16 Ohm version will be more than sensitive enough - and we might save some uF in the high-pass filter.
Another candidate is the 18 SOUND 8NTLW2000-16. Being over the moon from the performance of its smaller sibling, the 6NTLW2000-16 in my Revelator-44, why not some of the same from the 8" version? These dual gab motor structures can do stuff I never heard from any other speaker driver! They have the ability to dig into the fabric of sound to an unprecedented level. Micro-detail some would call it. We'll see how things work out. I also ordered a pair of 8NMB420-16, the 16 Ohm version of the midrange driver I used in my Faital-3WC-15 speaker. It has a benign frequency response that makes crossover work easy, but how about the sound of this combination? Only time can tell.

For tweeter I didn't hesitate to order the ScanSpeak D2908/714000 and D2908/716000 tweeters. It's been quite a while since I used the 714000 (MUN-17) and Jantzen Audio has some in stock, so an option for those who come first. The 716000 (carbon) was new to me, but proved almost interchangeable with the 714000- and honestly, I couldn't tell the difference in sound.

So, a mockup was made with the D2908/716000, the 8PE21-16 and because I had to wait for the ScanSpeak 32W bass drivers - a JBL 2226H in some 83 liter cabinets. See pics below. After some crossover tweaking I could start listening and this proved so promising it was time to get some HDF sheets and fire up the table saw.
Later I tried an old - very old - SEAS 13" bass driver; not good! The SEAS was replaced with an ScanSpeak 28W similar to the one used in the Ellipticor-28 - this works and promised good for the larger sibling, the 32W. Eventually the 32W drivers turned out to more than fulfilling my anticipation. Deep and dry bass from its ~80 litre volume.
Below you can read about the many mid-drivers tested from numerous crossovers. I think I wired more than 20 crossovers to try out various topologies and combinations of drivers. Many more than it took for The-Loudspeaker-5 in fact. For the TL-5 I knew the midrange and compression driver/horn from previous versions.
I also had to take the TL-4 to the living room before I was certain I had the crossover right. Despite the enlargement of my workshop last year, still I needed the 24 sqm area of the living room to hear the 32W bass section to its full. It goes deep and I think you may ditch your subwoofer once the 32W is in place. F3 = ~32 Hz.
April 2026: The-Loudspeaker-4 has now been occupying our living room for some months and every time I fire it up, it delivers. I honestly don't think I can do better. The bass is deep and dry and there's a fullness to the midrange, a scale I hadn't anticipated almost a year ago. The Be-dome delivers a treble that makes you seriously question the rationale for compression drivers except for PA purposes.

ScanSpeak D2908/714000 and D2908/716000 tweeters.
The Be domes are discontinued, but Jantzen Audio still has some in stock.
They are equally good, period!

The crossover features a simple LR2 topology. The Hypex module delivers the low-pass section for the bass driver.

Cabinets were made from 19 and 25 mm HDF and the cladding from 20 mm Baltic birch. View images below and also check out The-Loudspeaker-3, as they share quite a few construction details.
19 mm HDF for all sides, top and bottom and internal bracings. Front (for bass) and back from 25 mm HDF. Front for mid and tweeter made from laminate of 2 x 19 mm HDF.

All constructions starts with a mockup to find out what works - and what doesn't.

Routing for the octagonal midrange driver was easier than expected.
Place the driver face down and draw out the outer lines.
Fasten a piece of mdf to slide the router against. Make sure you have plenty of light to see when to start and stop! A small LED in the router head would have been nice.

I later made a template for routing for the midrange drivers. Actually quite easy. Read here.
Also see this.

The rear of the MT cabinet. Preliminary crossover was made with Superior-Z for the midrange, but sound wasn't as expected. Alumen-Z solved the problem. Amber-Z for tweeter (D2908/716000). These B&C mid drivers are demanding!!

For bass I initially used some 2226H JBL drivers I had at hand. JBL promises Fs = 40 Hz. Not the case! These drivers have Fs = 65 Hz - and they stay there! But still, delivers some solid deep bass, even from 80 liter volume. But very disappointing, JBL!
With Alumen-Z for the midrange and some tweeter tweaking this proved a worthy setup, valid for further refinement - and time to order some 32W/4878T01 ScanSpeak bass drivers.

I used 19 mm HDF except for front and rear panels, here 25 mm HDF.
For midrange/tweeter front panel I used a laminate of 2 x 19 mm HDF.

Bass cabinets pretty much done. Have to wait routing for bass drivers until I have them at hand.
Routing for the Hypex box is done before gluing the rear panel.

MT skeleton shaping up. Remember routing for the venting hole in one side of the MT cabinet. See drawing. I did 14 x 100 mm. You can make holes to match the area, approx. 14 sqcm.
Actually I had to do new slots as these were too far back, they should be ~25 mm from the front edge.
On the inside add glue around the hole and add one layer of felt material. This makes aperiodic tuning, read here. Closed box can sound too dry and forward, aperiodic vent makes for more sense of depth due to the less restrained motion of the midrange cone. At least to my subjective experience.

MT section from front and rear. The rear panel behind the MT section will be attached with screws.

Bass cabs with MT section on top, ready for glue.
I added fillets because I wanted bass panel and rear upper panel detachable - for possible future tweaks.
Fillet for the MT front panel just to increase gluing surface.

Left: Felt on sides and top of rear compartment. The crossover will be placed on the lower part of the MT cabinet. Right: The entire cabinet, now bass and MT sections glued together.

Damping causes a few quite some trouble, so here was the plan I used.
2.5 sqm supplied with the kit. This should be enough.

Acoustilux damping:

1. Cover all internal panels of the MT cabinet with acoustilux.

Left is towards top.
a. 1 pcs 50x50 cm, fold and place on port top panel.
b. 1 pcs 50x50 cm, fold and place above bass driver (top panel of bass section).
c. 1 pcs 25 x 50 cm, place on rear panel.
d. Not shown. 1 pcs 50x50 cm and placed on rear panel in crossover section (behind MT section).

Having the cabs half finished I mounted the preliminary MT front and a preliminary bass front with a pair of vintage SEAS 33 F-WB bass drivers, probably some 50+ years old. Technically they're OK, but these drivers were snoring and buzzing and most of all, lacking dynamics. They're just too outdated and I took them to the recycling site. Things have developed over this half century.

As there would be at least a month until I would have the ScanSpeak 32W drivers, I mounted a spare pair of 28W/4878T01 drivers. Despite the cabinets being too large for this driver - dynamics, deep bass and surprisingly enhanced transparency from the midrange. It matters what's below the mid-driver! The better the bass, the better the midrange.
This I can live with for a month while making the final MT fronts and Baltic birch cladding of the cabinets. The midrange driver will have a detachable panel, as I want this to an experimental speaker, and who knows what may turn up in the future of 8" midrange drivers.

Baltic birch cladding and base panel in place. Now the speakers just need the 32W bass drivers - and the front grills.
Already now - with the 28W bass driver - wow... Did I say the TL-5 horns made the best treble ever? I admit I have to modify this statement. These D2908/716000 tweeters makes me miss - nothing! Honestly, as for the Revelator-44's D2904/710003 tweeters, paired with Amber-Z caps, I miss nothing. These ScanSpeak tweeters are phenomenal. If they sound bad, you made a poor crossover or used inferior crossover components - or you have some other bottleneck in your system.

Also some 12NTLW2500-8 bass drivers from 18 SOUND was tried. Took quite some equalisation in the Hypex module to get the deep end, but potent dry bass. I had plans for these in another classic 3-way construction. Eventually the were replaced by 12NTLS3500-8, but that's another story.

32W drivers in house. Time to do some front panel routing.
As always: NEVER rout for drivers before you have them at hand! All things have tolerances.

So, finally the 32Ws in place - and Oh-My....
The same feeling as with the 28W from my Ell-28s - only more of the same dry, dynamic and articulate bass.

I just had a new record with John Scofield and Dave Holland.

Great relaxing recording and the 32Ws giving full credit to Dave's upright bass.
Hard to believe these guys played with Miles Davis some 50 years ago.

Having a great time with these drivers' sibling, the 6NTLW2000-16 in my Revelator-44 speakers, I had great hopes for these 8" midrange drivers. In terms of measurements and simulation, not as easy as the B&C drivers, but the sound....

Looking at the frequency range where this driver has to operate, the 300-2000 Hz range, it doesn't look bad at all. A little wobbly, but no sharp dips or peaks. The sound is smooth and transparent; this is what matters. Where the B&C driver can appear phenomenally fast and at times snappy, which suits some kind or records, this driver is smooth and resembles the sound of my Revelator-44, only a bigger sound.

Front panel sections were prepared (much easier than the 8PE21s) and measurements and simulation could start.

Initially a low-pass LR4 crossover was used for the 8NTLW midrange due to the dip around 2 kHz and this proved very good indeed.
My preferred LR2 filter proved at little more difficult due to the 8NTLW's dip at 2 kHz, but apart from this the roll-off is very nice and a LR2 was tried and proved sonically superior to the LR4 crossover. I guess I made more than a dozen wired crossovers for these two drivers to get where I wanted. This takes time and I call in my first-to-hear buddy to have his response.
In addition to the LR2 filter I raised the system sensitivity to around 94 dB as the Hypex has no problems with that and the tweeter sensitivity is really what sets the limit here. The 8NTLW could even manage more despite its 16 Ohm impedance. This means very small amps can run this speaker. For the time being I don't have less than 30 watts from my EAR-861s.
Now, going from 4th to 2nd order brought back the music. LR4 is just so technically right, but I've always found it to be less engaging compared to LR2 filters, at least for smaller 2-4-ways. You may argue the TL-1-2-3-5 all have LR4 between mid and horn, but a 10" mid and a compression driver take other measures.

Left image: My first-to-hear body brought a rum from Thailand (!) to celebrate the 32W occasion: Really good, not too sweet, not too dry, just right.
Right image: Don't forget to make slots in the grill frame to allow ventilation from the mid cabinet.

Sometimes we have to try go side roads to get back on track. Testing the n^th crossover for the 8NTLW2000-16 and D2908/714000 combo I got stuck and things just didn't turn out the way I wanted. Thus the 8NMB420-16 was purchased, because it's an easier driver - crossover wise - but it just didn't have the magic of the 8NTLW2000-16. So, the NTLW was back in place. Next I wanted to try a soft dome and the D2904/710003 was inserted, which actually caused a lot of trouble as the front panel was prepared for a 110 mm dome. Anyway, some crossovers were tried and eventually I ditched a slightly complex low-pass section for the NTLW and made a very simple one:

Despite a less nice roll-off of the midrange driver, this all of a sudden started sounding right. Thus, the 7140 Be dome was back in place and I started listening. Minor adjustment of treble level and I could lean back and say YES! This is it! Sometimes we have to overlook the visual beauty of things and start trust our hearing. Linear distortion can be deceptive and it certainly all depends on where and how much. Dips and peeks can very well be good-natured.

HYPEX PROGRAM

Go to Hypex page here.

More programming info here.

I guess only a few have balanced output from their pre-amp, thus high-level input may be preferred.

There are two files for The-Loudsepaker-4:

1: Driving the Hypex module in balanced mode from your preamplifier and your main amp for MT section has a gain of ~25 dB. In this situation I use preset 2 (10 dB additional gain).
Program is TL4-XLR

2: Driving the Hypex module with high-level input (you take the signal from the speaker binding posts).
Program is TL4-HLI (high level input)

Download files HERE.
Unfold zip file and place the two folders in FilterData folder in Documents on your PC.

A few comments on MEASUREMENTS before you start interpreting the readings below.
First of all, if we think measurements will tell us how a speaker sounds, we're wrong. The perception of sound is way too subjective to be reflected in any measurements we can perform. A loudspeaker system is meant to give us a satisfying idea of an acoustic event and for some people a pair of 5 USD ear-plugs are enough, others spend 200 kUSD on a truly full-range pair of speakers - and the latter may not be happier than the former.
Measurements may give us an idea of tonal balance of a system, i.e. too much or too little energy in certain areas, although dispersion characteristics play a vital role here. A two-way 7+1 and a three-way 7+4+1 may display similar horizontal dispersion, yet sound very different. Measurements may tell us about bass extension if far-field measurements are merged with near-field measurements. In addition to this, ports may contribute to bass extension. Most of we diy'ers do not have access to an anechoic room for full-range measurements from 20-20000 Hz.
What cannot be seen is what kind of bass performance we get in a given room. Bass performance is highly dependent on in-room placement of your speaker and the same speaker can be boomy in one place and lean in another. Actual SPL level at 1 meter distance and 2.8V input is useful for en estimate of system sensitivity and combined with the impedance profile may give an idea of how powerful an amplifier is needed to drive the speaker to adequate levels.
What measurements do not tell is the very sound of the speaker unless displaying serious linear distortion. The level of transparency, the ability to resolve micro-details, the "speed" of the bass, etc., cannot be derived from these data. Distortion measurements rarely tell much unless seriously bad, and most modern drivers display low distortion within their specified operating range.
Many people put way too much into these graphs and my comments here are only meant as warning against over-interpretation. There are more to good sound than what can be extracted from a few graphs. Every graph needs interpretation in terms of what it means sonically and how it impacts our choice of mating drivers, cabinet and crossover design.
What measurements certainly do not tell is the sonic signature of the speaker, because speaker cones made from polypropylene, aluminum, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of adding spices to the stew. Nor do measurements tell what impact the quality of the crossover components add to the sound, from state of the art components to the cheapest of coils and caps, they all measure the same if values are correct, yet sound very different.

One version of the crossover gave this response from the 8NTLW setup. Initially from a LR4 crossover between mid and tweeter. Response at 0, 10, 20 and 30 deg. off-axis.

Final response from a LR2 crossover of 8NTLW2000-16 and 6640 tweeter.
This sounds better, much better.

Final impedance of MT section.Green is minimum phase.
This is pretty unusual! Minimum impedance of 8.7 Ohms @ 10kHz and up. It should be a wet dream for any tube amp.
I even tried running the MT section from the 16 Ohm tabs on my EAR-861 tube amp. Well, not better than from the 8 Ohm tabs.

Horizontal dispersion @ 0, 10, 20, 30 and 40 deg. off-axis. Measurement taken at a height between midrange driver and tweeter. Very even dispersion in upper-mid and the most important treble range.

To configure a DIY kit and get a written offer including shipping cost, please use the DIY kit configurator in the Jantzen Audio website:

https://jantzen-audio.com/diy-kits/

Remember to add terminals when ordering at Jantzen website. No longer included in kit.

Layout for D2908/716000 and D2908/714000 version.
For D2908/714000 (Be-dome), the values of R1 are different.

Here full size.
My C1 Amber-Z are bigger than the ones you have. Just a matter of the tube it is embedded in.

Placement of crossover.
Notice inverted polarity of midrange driver!!
I added a connector bar between the crossover and drivers in case I later wanted to make changes. You have to order these separately if you want them too. 2 pcs 012-0362.

Be dome version. I'll stick to these as I have them and they need to be used.
The carbon tweeters I can use elsewhere.

Having listened to the TL-4s for months now, I can only say this is it.
Not small, but they fit the living room well and have the scale and dynamics if its larger siblings.

Copy paste from elusive Disc: "...crank it up and enjoy this not-so-guilty, below the neck retro-pleasure fest. Yes the CD layer sounds pretty good and the SACD even better, particularly in the air and atmosphere department but for the full effect, do insist upon the double 45 rpm version. It's the biggest and the best bang for your (extra few) bucks!" - Michael Fremer, Music Angle, rated 8/10 for music, 9/10 for sound!

I'm a long time fan of Anthony Wilson and got most of his records, but this is my favourite. My rating would be 9/10 for music. Never do 10/10, we never know what may come next. The recording, mastering, etc., everything seems to come together here and this is 45 rpm vinyl at its best. From the TL4s I can play this record insanely loud with no distress to my ears. The dynamics are astonishing.

I have had electrostatic speakers (QUAD 2812) and good electrostatic speakers can do stuff few other speakers can. I've always been hesitant to use the term "electrostatic" because you have to be really good to be "electrostatic". Listening to 45rps from Anthony Wilson and Patricia Barber's Companion, I couldn't help thinking "electrostatic"! But here including deep bass and dynamics. I couldn't be more happy.

The rear panel fillets are there to allow placing the speaker on its back without damaging the Hypex volume knob.
The 4-pole bar is not included in kit. I just needed it for access to the drivers during crossover development.

The front grills

No details will be given on the construction of the front grills. This can be done in numerous ways and I suggest you look at the TL-3 for ideas. I made mine from 19 mm HDF and I had to add a brass bar across the frame where the bend is as the fabric would otherwise bulge in and hit the bass rubber surround, something I hadn't foreseen. The grills are held in place by 12 neodym magnets, 8 x 8 mm. 6 in the cabinets and 6 in the frame.
Making the grills wasn't easy! I used a combination of double adhesive tape and some staples at the corners.
My take on front grills: http://www.troelsgravesen.dk/Front-Grills.htm

The final speakers in our living room.