Revelator-44

The following is my diary over almost the last year, as it started when I began the Ellipticor-28. Hope you enjoy!

At the time I ordered the Revelator 28W/4878T01 bass driver for the Ellipticor-28 I also included two pairs of Revelator 22W/8851T00 drivers for an alternative bass section - and to find out first hand, which was best.
Actually the 28W did so well I thought I'd never get around to testing the 22W drivers, but staring at me from the shelf I eventually gave in and started making the cabinets - quite a lot of work, but I enjoy the woodwork.
So, what was meant to be an alternative bass section - and a fully passive version of the Ellipticor-28 - now became a new speaker offering a semi-active or fully passive speaker system. Or both actually.
And please DO NOT ask if you can combine something from Ell-28 with Rev-44! Not gonna happen.

Initially the ScanSpeak Ellipticor 18WE/8542T00 was meant for midrange, but testing some new midrange drivers from 18 SOUND, made me think twice, as these proved so good, I decided to make a new construction. So, this isn't a Ellipticor-44, rather Revelator-44 having both bass and tweeter from the Revelator family.
The midrange driver is the 18 SOUND 6NTLW2000-16 driver. A phenomenal driver featuring double magnet gab, interleaved sandwich voice coil (notice the voice coil is wound on both sides of the voice coil former!) and other features. Download specs below. Read a Technical Note on Dual Gap motor structure and Interleaved Sandwich Voice coil drivers here.

I have a 16 Ohm midrange driver of another brand with very similar properties. Exactly the same cone area and Fs, etc., but with a conventional voice coil and motor structure, and the thing is, this NTLW driver has a midrange transparency hard to beat. It can do stuff conventional drivers apparently have hard time doing. I'm sure you won't be disappointed. Only bad thing is the truncated basket, but this I can live with.

To sum up: As built here, there a several options for their use:
1: Fully passive run from one or two power amps, preferably with adjustable gain to match the MT section with regard to sensitivity in case different amps are used.
2: Fully passive from a single amp, albeit a really good amp delivering 100+ watt/ch, and ability to work in low impedances. Actually not that low, but a decent amp is required.
3a: Semi-active with the bass drivers run by the Hypex FA501 plateamp and high-input from MT terminals.
3b: Semi-active with low-level input from pre-amplifier (my own preference). And again I will emphasize, there is no sonic gain running the latter, but having double XLR output from my pre-amp, this is the convenient way for me.

Basics:
3-way speaker, 2-driver bass module.
Dimensions: 34 x 52 x ~116 cm, WxDxH.
System sensitivity: 91.5 dB/2.8V/1 meter.
Impedance: 4 Ohms. Minimum 3.3 Ohm @ 32 Hz.
Power requirement: 100+ watts/channel minimum when run fully passive. 20+ wpc if Hypex module is used. Maybe smaller amps can be used, I don't have lower than 30 watts from my EAR-861s.

18 SOUND 6NTLW2000-16 midrange drivers, 16 ohms.
Download specs here.
Technical Note on Dual Gap motor structure and Interleaved Sandwich Voice coil drivers here.

The midrange low-pass filter features an LR2 topology with impedance correction of lower impedance peak.
Bass passive crossover features an LR2 topology with LCR correction circuit smoothing upper impedance peak.

Cabinets were constructed entirely from 20.5 mm Baltic birch with solid oak fillets here and there. See workshop images.

Above and below, the final stage of gluing the last side panel.
I added some 5x30 cm bars to top and bottom to further reduce vibration.
Also on crossover rear panel, a 5x25 cm bar was added, see below.

4 pcs 31 x 20 cm upper side panels.
4 pcs 32 x 20 cm, middle side panels.
4 pcs 12.5 x 25 cm, rear crossover panel.

Use vinyl glue.

To make room for lower bass you have to make a small cutout in the lower brace.
Well, really much too early to unpack the bass drivers, but as always, these rubber surrounds need a little brush up to become nice.

I love the look, feel and smell of freshly sanded cabs, but they wouldn't last long. Time for lacquer.

For two cabinets I used the following:
2 pcs 25 x 30 cm, bottom rear.
2 pcs 14 x 30 cm, bottom front.
4 pcs 11 x 34 cm, bottom sides.
4 pcs 21 x 42 cm, middle sides.
4 pcs 20 x 42 cm, top sides.
2 pcs 28 x 43 cm, top.
Total: 1.31 sqm. 1.5 sqm supplied with kit.

Left: Top section.
Right: Bottom section. No felt in middle section where the passive crossover will be.

Final lacquer coat. This oak goes well with the Baltic birch, I think.
Time for mounting terminals, Hypex and drivers. Passive crossover will wait until later.

Acoustilux. For two speakers:
2 pcs 50 x 50 cm, bottom cabinet.
4 pcs 20 x 50, fold next to port.
2 pcs 50 x 50 cm, top of cabinet.
Total 1.4 sqm. 1.5 sqm supplied with kit.

To the right: Here my backside with options for semi-active or fully passive operation.
See wiring at bottom of page.

For fun I programmed the Hypes with an 80 Hz LR2 low-pass filter and inserted a similar 1st order high-pass filter before the Parasound and ran the satellites inverted. Very well, albeit not fully integrated.

And here the final draft, my test cabs with the phenomenal 18 SOUND 6NTLW2000-16 midrange driver.

I enjoy digging up some old records from time to time - and except for the John Renbourn record, I hadn't heard these vinyls for decades! Tracked by my rejuvenated MSL cartridge, I didn't know the Vega and Jones records contained that much information. The magnificent 18 SOUND midrange driver certainly helped bringing out what I had missed before.
The Renbourn record has a story as I bought this album back in the Eighties and only a few years ago I leaned this re-issue was crap compared to the original pressing. Thanks to Michael Fremer. The original has the middle person's face in colour. After having read the review, I accidently found the original pressing one week later! I couldn't believe it - and MF was right. The re-issue sucks. The face of the knight in the middle must be in colours.

Competing against a coming The-Loudspeaker-5 is tough, but I didn't miss much going from TL-5 to Rev-44, the midrange dynamics and transparency and treble clarity maintained.

Patricia Barber's cafe blue is a phenomenal record - and a phenomenal recording. Side 3 contains an impressive drum sole and going from the TL-5 to Rev-44 didn't leave much to be desired. There is a difference having 440 cm^2 membrane area compared to the 1225 cm^2 area of the TL-5's bass driver. But if size is a matter, then the Rev-44 may be the answer. I hold the TL-5's compression driver/horn as an absolute reference in treble performance. I was surprised to hear how little difference, if any, it made in the midrange and treble ranges which points to the magnificent 18 SOUND midrange and phenomenal 7100 tweeter from ScanSpeak.
Only thing to do now is starting making the final MT cabinets.

Lots of records found their way to the spinning table, all shining through thanks to the Revelator-44s.
BTW, these STEP pressings are magnificent. The UHQR pressing of Sonny Rollins was an impulse purchase despite a horrific price and saxophone not being my first choice, but this "double-mono" recording is worth while. The sax is truly in left channel and bass and drums in the right channel - don't place the speakers too far apart, or do the "listen from another room".

Having been to the Musikverein in Vienna, I just had to have this Keith Jarrett recording and it turned out to be phenomenal. The solo concerts - left image - are interesting, but surprisingly not particularly well recorded.

To the right: Now, I already have a 45 rpm Kind of Blue, the MoFi - and it's great. The info doesn't tell cut from what.
This UHQR is an AAA cut from master tape and cut by Bernie Grundman - and costs a minor fortune. And it's worth it. I never get tired of Adderley's and Coltrane's sax solos on Flamenco Sketches. Never. I would buy a second copy for my desert island record collection.

MT-cabinet

The MT cabinet pretty much follows the "easy" MT cabinet suggested for the Ellipticor-28.
The 6NTLW2000-16 driver may look small due to the truncated basket, but it has the exact same cone area as the 18WE driver.
The cabinet, even here, is NOT a beginner's project, so if you have questions, please don't engage in the Rev-44.

Working on the rear side of the MT cabinet. Odd angles all over!

Countless notes on cutting angles were made during construction.

Gluing the center brace.

Midrange front panel shaping up.

Bitumen pads

Add bitumen pads before final assembly.

Bitumen pads. Left from front, right from rear, pay notice wide angle photo.
You can leave out the small triangle on top to the rear.
The kit supplies 2 x 50x50 cm bitumen pads. This is enough for bottom and sides.
Remember to mirror the side panel cuts!!
The front, top and rear are made from 25 mm HDF and do not need bitumen pads.
And remember, bitumen pads don't have to fill the space 100%. Leave 3-5 mm to all boundaries.
http://www.troelsgravesen.dk/tips.htm#Glue_for_Bitumen_Pads

Start making the midrange front panel. Takes some time due to the truncated driver.
Remember to chamfer midrange driver hole, 45 deg. some 12-13 mm depth.

6NTLW2000-16 driver during testing.

Testing front panel for drivers. Not too bad for a truncated driver.

Gluing front panels for middriver.

Cabs finally ready for drivers...
Sides had lacquer like the bass cabs and the black HDF had beewax.

Acoustilux for the MT cabinet:

Cut the following sheets:

2 pcs 80 x 14 cm: front part of cabinet.
2 pcs 80 x 18 cm: rear part of cabinet - cut something like this:

4 pcs 25 x 14 cm: fold and place towards top in rear compartment. Fold and place below port.
2 pcs 10 x 25 cm: fold and place on top of front compartment (behind tweeter)

2 pcs 10 x 30 cm, roll and stuff the port (aperiodic tuning):

Connect drivers and enjoy!

HYPEX programming:

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 Revelator-44:

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 Revelator-44-XLR

2: Driving the Hypex module with high-level input (you take the signal from the speaker binding posts). Program is Revelator-44-HL (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.

SPL of 6NTLW2000-16 from actual MT cabinet. Smooth - smooth in the overall midrange.

Response from the two bass drivers normalised for 2.8V/1 meter. Merged with nearfield response @ 200 Hz.
The dip at ~32 Hz indicates the port tuning.
These bass drivers in parallel can manage around 91.5 dB sensitivity, perfect for the MT section.

Impedance of bass drivers in parallel, no crossover. Port tuning is where I wanted it, around 34 Hz.

Impedance of bass and MT sections with passive crossover.
The high impedance of the MT section makes it an easy load for any tube power amp. Very much an 8 Ohm MT section.

Final impedance of complete system with bass and MT section run in parallel from passive crossovers.
Minimum impedance 3.3 Ohms when all run from a single amplifier.

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

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

There will be a third option, which is the kit including components for both passive and semi-active version, which includes the Hypex 501 and connector blocks for the "switch board" seen below.

I'm sure I'll have the question why on earth building both versions. Well, it's interesting comparing the various options and it may give you the opportunity of trying out various amps in particular for the MT section as it has high impedance and equally well suited for low-wattage tube amps. And with a high-level input to the Hypex the Rev-44 can be run by almost anything.

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

MT section layout. As the crossover was first designed for 18WE driver, some C4s had to be removed and it didn't look good, thus the plywood on top of C4. Reworking a crossover never makes it look nicer...

Initially a C-coil was tried for L1, but this cored coil did as well being made from 1.6 mm wire.

Several options:

1: Fully passive. Connect 1-2 to C-D and bi-amping. Preferably amps with variable gain.
2: Fully passive. Connect 1-2 to C-D and use one amp for all (minimum impedance 3.2 Ohms). Use jumper on terminals.
3: Semi-active: Connect 1-2 to A-B and have Hypex run from balanced pre-amp.
4: Semi-active: Connect 1-2 to A-B and have signal from MT terminals.

Should you want to have both options of fully passive and semi-active, you have to ask Jantzen Audio to add these items, the terminal blocks:

High-level input. I guess most will use this. Easy - and sounds exactly as good as taking the signal from your preamp. Some will say the high-level input preserves the sonic signature of your power amp, but this is not my experience. They sound the same.