{"id":59,"date":"2011-10-12T15:03:58","date_gmt":"2011-10-12T13:03:58","guid":{"rendered":"http:\/\/localhost\/wordpress\/?page_id=59"},"modified":"2020-11-28T14:42:46","modified_gmt":"2020-11-28T14:42:46","slug":"revelation-two-monitor","status":"publish","type":"page","link":"https:\/\/www.audioexcite.com\/?page_id=59","title":{"rendered":"Revelation Two – Monitor"},"content":{"rendered":"

Concept:<\/strong><\/span><\/h3>\n

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\"\"<\/a>Revelation Two – Monitor<\/strong><\/span> is a medium sized 2-way stand-mount loudspeaker for small\u00a0 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.<\/p>\n

Loudspeaker driver units:<\/strong><\/span><\/h3>\n

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Revelation Two – Monitor<\/strong><\/span> 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.<\/p>\n

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.<\/p>\n

For further details see:<\/p>\n

15W\/4531G00<\/a><\/p>\n

D2608\/913000<\/a><\/p>\n

Cabinet:<\/strong><\/span><\/h3>\n

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Revelation Two – Monitor<\/strong><\/span> 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).<\/p>\n

Cabinet drawing: Dayton 14 liters Curved Cabinet #302-721<\/a><\/p>\n

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.<\/p>\n

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Baffle drawing and driver unit layout:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 Chamfered baffle:
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Box simulation:<\/strong><\/span><\/h3>\n

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\"\"<\/a>There are three different box tuning options in order to satisfy different bass preferences and room tuning options.<\/p>\n

Option 1:<\/strong><\/p>\n

13 liter closed box with Qt = 0,7 (anechoic response)<\/p>\n

-6db = 51Hz<\/p>\n

-12db = 34Hz<\/p>\n

Option 2 (reference):<\/strong><\/p>\n

13 liter bass-reflex box with Fb = 39Hz (anechoic response)<\/p>\n

-6db = 35Hz<\/p>\n

-12db = 28Hz<\/p>\n

Option 3:<\/strong><\/p>\n

11.5 liter bass-reflex box with Fb = 44Hz (anechoic response)<\/p>\n

-6db = 39Hz<\/p>\n

-12db = 31Hz<\/p>\n

The closed box version has a surprisingly high bass performance when room gain is included. In my room the bass-reflex option 2<\/strong> fits my taste best. It goes remarkable low and sounds almost like a much bigger floor-stander. For those who wants a bit more\u00a0 bass punch at the expense of some low end extension, the option 3<\/strong> is more suitable. In option 3<\/strong> and when using Dayton Audio cabinets, it’s necessary to reduce the internal box volume by 1.5 liter\u00a0 with something solid.<\/p>\n

Cross-over design:<\/strong><\/span><\/h3>\n

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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)\u00a0Linkwitz 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.<\/p>\n

Tweeter level options:<\/strong><\/span><\/p>\n

The tweeter level can be adjusted by changing the R1<\/strong> and R2<\/strong> resistor values as follows.<\/p>\n

\"\"<\/a><\/p>\n

+2db<\/strong><\/p>\n

R1 = 2.2\u03a9<\/p>\n

R2 = 6.8\u03a9<\/p>\n

Max linearity<\/p>\n

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+1db<\/strong><\/p>\n

R1 = 2.7\u03a9<\/p>\n

R2 = 5.6\u03a9<\/p>\n

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0db Reference level
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R1 = 3.3\u03a9<\/p>\n

R2 = 4.7\u03a9<\/p>\n

The frequency response is optimized around the 15 degree off-axis measurement. This results in a cross-over frequency of 2900Hz.<\/p>\n

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-1db<\/strong><\/p>\n

R1 = 3.9\u03a9<\/p>\n

R2 = 4.7\u03a9<\/p>\n

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-2db<\/strong><\/p>\n

R1 = 4.7\u03a9<\/p>\n

R2 = 3.9\u03a9<\/p>\n

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\"\"<\/a>The phase integration between the two drivers are exceptional.<\/p>\n

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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\u00a0 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\u00a0 through out all the tweeter level settings. The cross-over frequency shifts a bit between the different settings, but is nothing to worry about.<\/p>\n

2700Hz = +2db<\/p>\n

2800Hz = +1db<\/p>\n

2900Hz = 0db “Reference”<\/p>\n

3000Hz = -1db<\/p>\n

3100Hz = -2db<\/p>\n

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Impedance measurements:<\/span><\/h3>\n

 <\/p>\n

\u00a0\"\"<\/a>Green = Left loudspeaker<\/p>\n

Blue = Right loudspeaker<\/p>\n

The impedance chart shows the bass-reflex option 2<\/strong> 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.<\/p>\n

\"\"<\/a>Green = Left loudspeaker<\/p>\n

Blue = Right loudspeaker<\/p>\n

The impedance chart shows the bass-reflex option 2<\/strong> 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.<\/p>\n

\"\"<\/a>Green = Left loudspeaker<\/p>\n

Blue = Right loudspeaker<\/p>\n

The impedance chart shows the closed box option 1<\/strong> 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.<\/p>\n

Frequency measurements:<\/strong><\/span><\/h3>\n

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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.<\/p>\n

All frequency response charts are presented in a 50db scale and with 1\/24 octave smoothing.<\/p>\n

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\"\"<\/a>Frequency response 15deg off-axis, reference tweeter level\u00a0 (80db) scale :<\/strong><\/p>\n

Blue = Left loudspeaker<\/p>\n

Red = Right loudspeaker<\/p>\n

In the higher frequencies they are a close, but not a perfect match due to the\u00a0 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.<\/p>\n

\"\"<\/a>System frequency response 15deg off-axis, reference tweeter level :<\/strong><\/p>\n

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.<\/p>\n

\"\"<\/a>System frequency response 15deg off-axis, reference tweeter level :<\/strong><\/p>\n

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.<\/p>\n

\"\"<\/a>System frequency response 15deg off-axis, reference tweeter level :<\/strong><\/p>\n

Blue = Without front grill attached<\/p>\n

Red = With front grill attached<\/p>\n

I would recommend listening to this loudspeaker without the front grills attached even though it doesn’t affect the frequency response to badly.<\/p>\n

\"\"<\/a>System frequency response reference tweeter level :<\/strong><\/p>\n

Blue = On-axis<\/p>\n

Red = 15deg off-axis<\/p>\n

Green = 30deg off-axis<\/p>\n

Left loudspeaker. Nice extended off-axis response.<\/p>\n

\"\"<\/a>System frequency response reference tweeter level :<\/strong><\/p>\n

Blue = 15deg off-axis<\/p>\n

Red = 30deg off-axis<\/p>\n

Green = 45deg off-axis<\/p>\n

Left loudspeaker. Even at a 45deg off-axis the tweeter reaches 15kHz.<\/p>\n

Distortion measurement:<\/span><\/h3>\n

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Measurement setup:<\/strong><\/span><\/p>\n