Revelation Two – Monitor

Concept:

 

Revelation Two – Monitor is a medium sized 2-way stand-mount loudspeaker for small  to medium sized listening rooms. It offers several tuning options like two different bass-reflex tunings as well as a closed box version. The tweeter can be fine tuned to five different levels according to personal preferences and taste.

Loudspeaker driver units:

 

Revelation Two – Monitor uses two driver units from ScanSpeak. The mid-woofer 15W/4531G00 and the tweeter D2608/913000. The 15W/4531G00 is one of the best mid-woofers available to the DIY market. It has a nice low extension and a remarkable mid-range presentation, a class of its own.

The D2608/913000 has an effortless vivid sound with a nice top-end sparkle without ever sounding exaggerated or harsh. The two drivers blend very nicely with each other.

For further details see:

15W/4531G00

D2608/913000

Cabinet:

 

Revelation Two – Monitor uses a 14 liter “Dayton Audio” enclosure. This is a very nicely built curved cabinet with a 25mm (1″) MDF front-baffle. The enclosure walls are made of 18mm MDF as well as a 15mm brace from the bottom to the top. The enclosure net volume is around 13 liters (enclosure volume – drivers, filter and port).

Cabinet drawing: Dayton 14 liters Curved Cabinet #302-721

The internal cabinet walls are taped with strings of bitumen pads to reduce resonances. The enclosure is lightly filled with sheep wool. All drivers are flush mount and in order to let the mid-woofer “breathe” properly, don’t forget to chamfer the baffle.

 

Baffle drawing and driver unit layout:                                                                          Chamfered baffle:

Box simulation:

 

There are three different box tuning options in order to satisfy different bass preferences and room tuning options.

Option 1:

13 liter closed box with Qt = 0,7 (anechoic response)

-6db = 51Hz

-12db = 34Hz

Option 2 (reference):

13 liter bass-reflex box with Fb = 39Hz (anechoic response)

-6db = 35Hz

-12db = 28Hz

Option 3:

11.5 liter bass-reflex box with Fb = 44Hz (anechoic response)

-6db = 39Hz

-12db = 31Hz

The closed box version has a surprisingly high bass performance when room gain is included. In my room the bass-reflex option 2 fits my taste best. It goes remarkable low and sounds almost like a much bigger floor-stander. For those who wants a bit more  bass punch at the expense of some low end extension, the option 3 is more suitable. In option 3 and when using Dayton Audio cabinets, it’s necessary to reduce the internal box volume by 1.5 liter  with something solid.

Cross-over design:

 

The cross-over is very simple and consist of a 12db/octave electrical filter for the mid-bass and a 18db/octave filter for the tweeter to achieve a 4th order acoustical (24db/oct) Linkwitz Riley cross-over slope. The tweeter has a simple L-Pad circuit in order to dampen the tweeter level. This L-Pad can be changed to adjust the tweeter level +/- 2db.

Tweeter level options:

The tweeter level can be adjusted by changing the R1 and R2 resistor values as follows.

+2db

R1 = 2.2Ω

R2 = 6.8Ω

Max linearity

 

 

 

 

 

 

 

 

 

+1db

R1 = 2.7Ω

R2 = 5.6Ω

 

 

 

 

 

 

 

 

 

 

0db Reference level

R1 = 3.3Ω

R2 = 4.7Ω

The frequency response is optimized around the 15 degree off-axis measurement. This results in a cross-over frequency of 2900Hz.

 

 

 

 

 

 

 

-1db

R1 = 3.9Ω

R2 = 4.7Ω

 

 

 

 

 

 

 

 

 

 

-2db

R1 = 4.7Ω

R2 = 3.9Ω

 

 

 

 

 

 

 

 

 

 

The phase integration between the two drivers are exceptional.

 

 

 

 

 

 

 

 

 

 

 

 

 

I personally use the 0db reference or the -1db tweeter level. On well made recordings the 0db setting really shines with a huge sound stage. With  bad recordings I prefer the -1db setting, but it all comes down to personal preferences and which equipment chain you using. The nice individual driver phase integration is maintained  through out all the tweeter level settings. The cross-over frequency shifts a bit between the different settings, but is nothing to worry about.

2700Hz = +2db

2800Hz = +1db

2900Hz = 0db “Reference”

3000Hz = -1db

3100Hz = -2db

 

Impedance measurements:

 

 Green = Left loudspeaker

Blue = Right loudspeaker

The impedance chart shows the bass-reflex option 2 with a Fb of 39Hz. The impedance minimum is 3.9Ohm at 200Hz. This is a 4Ohm system which should be a relative easy load for a 4Ohm capable amplifier.

Green = Left loudspeaker

Blue = Right loudspeaker

The impedance chart shows the bass-reflex option 2 with a Fb of 39Hz and using the system impedance compensation circuit. The impedance minimum is 3.9Ohm at 200Hz. The impedance is between 4-6Ohm through out the entire frequency response. This option is suitable for tube-amp users.

Green = Left loudspeaker

Blue = Right loudspeaker

The impedance chart shows the closed box option 1 with a Fb of 64Hz and using the system impedance compensation circuit. The impedance minimum is 3.9Ohm at 200Hz. The impedance is between 4-6Ohm through out the entire frequency response. This option is suitable for tube-amp users.

Frequency measurements:

 

If nothing else is noted in the comments, the following frequency measurements of the finished loudspeaker are made at a 2m distance at tweeter height and for the 0db tweeter reference level.

All frequency response charts are presented in a 50db scale and with 1/24 octave smoothing.

 

Frequency response 15deg off-axis, reference tweeter level  (80db) scale :

Blue = Left loudspeaker

Red = Right loudspeaker

In the higher frequencies they are a close, but not a perfect match due to the  frequency differences between the two tweeter samples. I personally can’t hear the difference between the left and right speaker so I guess when the room interaction is added the frequency response difference evens out.

System frequency response 15deg off-axis, reference tweeter level :

Right loudspeaker. Smooth driver roll-offs and a nice extended high frequency response. A small baffle diffraction is noticable at 3.5kHz. The dip between 6-9kHz is a characteristic of the ScanSpeak D2608/913000 driver unit.

System frequency response 15deg off-axis, reference tweeter level :

Right loudspeaker connected with a tweeter reverse polarity indicates a nice phase integration between the drivers and shows a approximate cross-over frequency of 2900Hz.

System frequency response 15deg off-axis, reference tweeter level :

Blue = Without front grill attached

Red = With front grill attached

I would recommend listening to this loudspeaker without the front grills attached even though it doesn’t affect the frequency response to badly.

System frequency response reference tweeter level :

Blue = On-axis

Red = 15deg off-axis

Green = 30deg off-axis

Left loudspeaker. Nice extended off-axis response.

System frequency response reference tweeter level :

Blue = 15deg off-axis

Red = 30deg off-axis

Green = 45deg off-axis

Left loudspeaker. Even at a 45deg off-axis the tweeter reaches 15kHz.

Distortion measurement:

 

Measurement setup:

  • Tweeter-axis near-field measurement at 20cm
  • Frequency Range: 200-10000Hz

 

The distortion measurements are done in near-field and the amplifier output level was adjusted for the loudspeaker so that the fundamental is 85dB at 1m and 90dB at 1m. This setting simulates normal to medium-high listening levels.

Left loudspeaker:

85dB at 1m

 

 

 

 

 

 

 

Left loudspeaker:

90dB at 1m

 

 

 

 

 

 

 

 

The Revelation Two – Monitor has very low distortion in the critical upper-mid and lower-treble area (1-3kHz).

Overall the loudspeaker has a very low odd-order harmonic distortion, but relatively high distortion below 1000Hz of the harmless 2nd order harmonic with peaks at 475Hz and 900Hz.

I think the elevated 2nd order distortion is a part of the unique mid-range sound characteristics of the sliced paper cone used in the ScanSpeak Revelator mid-woofers.

The ScanSpeak Revelator mid-woofer has a very nice presence and clarity and with a very open sound characteristics.

For further details see:

Distortion measurements Revelation Two – Monitor

Component list:

 

At an approximate cost of 1150 US$ a pair it’s not exactly a super cheap stand-mount loudspeaker , but it can be built cheaper if not using premium cross-over parts, binding posts and prefabricated enclosures. However I can strongly recommend Mundorf cross-over parts which sounds very good with these drivers.

It might be possible to save about 200$ by building the enclosures by yourself, but in my opinion the Dayton cabinets are well worth the money.

Summary:

 

The Revelation Two – Monitor is a medium sized stand-mount loudspeaker using two very high quality loudspeaker driver units from ScanSpeak. The design offers several tuning options in order to satisfy personal preferences and sound characteristics.

At a price of 1000-1200 US$ a pair it’s not exactly a cheap DIY design, but the sound and performance delivered from this loudspeaker usually costs several times more on the commercial market.

Sound description:

It is very hard to describe how a loudspeaker sounds like since it always will be a subjectively opinion, but here is my perception of the sound.

Despite the name “Monitor” the Revelation Two – Monitor isn’t a “Studio Monitor” used for near-field listening, but it brings out the details from recordings just like a “Studio Monitor” and it do so without ever sounding analytical cold, harsh or edgy.

The loudspeaker sounds bigger than its size indicates and it has a nice low end extension which reaches to the low 30:ies when room gain is added. The mid-range is  wonderful natural  and has an open character that doesn’t sound compressed or hard even on less good recordings. The tweeter is soft sounding with a nice vivid presentation and top-end sparkle.

When playing a well made recording the loudspeaker really shines up and present you with a very nice 3D perspective with a generous width, height and depth.

Recommended loudspeaker placement:

• No or little toe-in. Let the speakers play straight forward.
• >0.5 meters from back wall.
• 2 meters apart.
• 2.5 meters listening distance

The loudspeaker is optimized for a listening distance of 2.5m, but everything between 2-3.5m works fine depending on the room. As always it pays off to test different loudspeaker placements and see what fits the room and personal preferences the best.

Technical Specification:

 

RevelationTwo – Monitor
Type: Two-way medium sized stand-mount loudspeaker
Enclosure type: Bass-reflex or optional closed box
Woofer driver unit: 5,5” Sliced paper cone. ScanSpeak 15W/4531G00
Tweeter driver unit: 1” Soft dome. ScanSpeak D2608/913000
Cross-over frequency: 2900Hz.
Cross-over function: LR fourth-order acoustically, second-order electrically (wo) and third-order electrically (tw)
Frequency response: 35-25000Hz -6/+0 db (on-axis)
Sensitivity: 87db 1m/2.83v
Impedance: 4 Ohm
Enclosure volume: 13 liter internal net volume
Weight: 10,5kg (23,15lb)
Enclosure dimensions (height x width x depth): 356x216x317mm (14″x8.5″x12.5″)

 

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Thank you!

/Göran

Author of the “AudioExcite Loudspeaker Design” website