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Multi-Way Conventional loudspeakers with crossovers

Help figuring out the Silent Speaker
Help figuring out the Silent Speaker
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Old 26th May 2016, 09:11 PM   #1
EmuMannen is offline EmuMannen  Sweden
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Question Help figuring out the Silent Speaker

Hi everyone. I have been into vintage hifi for a while, currently running a pair of B.I.C SoundSpan TPR-600 that I got in mint condition from a friend. I personally love the look of these speakers but my wife claim that they “take over the room”. Her wish list is for something small that “blend with the walls” (white by the way).

Our house is an open floor plan acoustic nightmare where the omnidirectional qualities of the SoundSpan really shines. I was therefor thinking about swapping them for something like a pair of white Sonab OA-5 (type II). It was while surfing for alternatives I stumbled across the Silent Speaker II by Direct Acoustics (reviewed here and here). This speaker really intrigues me. I really like the look of it but I would need it in white so I started to play with the idea of building something like it myself. Building them will be no problems but I doubt I got the skills to reverse engineer them or designing something close to it. That's why I am asking for your help and feedback.

I have gathered as much information as possible about the Silent Speaker, here's a summery:

Frequency Response
40Hz to 10,000 Hz ± 2 dB
30 Hz to 17,000 Hz ± 4 dB
20 Hz to 20,000 Hz ± 6 dB

Dimensions
13½” wide (34.29 cm); 9” deep (22.86 cm); 22” at front (55.88 cm), 25” at rear (63.50 cm)

Power Maximum: 50 watts continuous
Power Recommended: 200 watts recommended for handling transients

Rated Impedance: 6 ohms
Minimum Impedance: 4 ohms

Crossover
The woofer is designed mechanically and electrically to roll off naturally, no additional filtering is necessary from the crossover. A two pole network adds to the natural rolloff of the tweeter, additional components equalize the tweeter response to achieve maximum flatness in the prescribed room location.

Frequency: 1600Hz,
Woofer Slope: 24 db/octave
Tweeter Slope: 24bd/octave

Driver Complement
Woofer: 6.5” with ±¼” linear travel
Tweeter: 1” soft dome type with magnetic cooling fluid

Bass Enhancement
The complex internal cabinet chambers extract the bass frequencies from the low frequency driver and feed them out through a slot in the bottom of the cabinet.

Woofer
For deep bass, the woofer is designed with a long voice coil and a soft suspension. It is relatively small in diameter, in order to provide good dispersion at the crossover frequency to the tweeter.

Tweeter
The tweeter is of the soft dome style. It uses a European design and includes magnetic cooling fluid for the voice coil.

That was all from the manufacturer, the following I got from one of the reviews:

Quote:
The SS2s use a bass slot (that runs along the bottom of the front of each speaker) that’s coupled to the the woofer through an inverted horn configuration.
I measured the slot (pixel counting from pictures) to be roughly 32 x 3 cm. It equals an Effective Piston Area of ~ 96 cm2, a circular port diameter of ~ 11 cm.

Given this information I started my guesswork about the design of “the complex internal cabinet chambers”.

Attached are six different drawings I did to visualize what the Silent Speaker might look like internally:

A. This picture is just the cabinet itself to get a feel for the overall volume. I got it to just above 30 liters.

B. This picture plays with the idea of a tapped and folded inverted horn. I have never seen a tapped horn where the speaker has been mounted on the top like this but I guess it would work. The line seems quite short and the terminus quite slim but I don't know much about T-Lines or Horns.

C. I started to play with the idea of a MLTL while reading up on T-Lines and Horns. Picture C is my initial response. I guess it could pass as a MLTL but its not an inverted horn and I don't know if the design makes sense.

D. This is an attempt to bring it back to an inverted horn again. Would this qualify as an MLTL? I guess not but it looks quite cool and the line is longer than before.

E. This is another take on the MLTL but I don't know if its better or worse than C.

F.
This is me giving up on Horns, T-Lines, MLTL etc and throwing together a ported enclosure in the shape of the Silent Speaker.

Now to my questions:
  1. Any thoughts about B-E or what are your guesses about the internal design of the Silent Speaker?
  2. Any suggestions for speaker elements based on the original ones, B-E or your own design?
  3. If I give up on exotic ideas and opt for F, any suggestions for speaker elements, tuning and cross frequency based on a 2-way, slot ported 30 liters enclosure?

Looking forward to your feedback / Rob

Ps. I am willing to play a bit with dimensions etc as long as the look and function of the original is somewhat maintained.
Attached Images
File Type: png SilentA.png (35.4 KB, 290 views)
File Type: png SilentB.png (49.2 KB, 285 views)
File Type: png SilentC.png (51.1 KB, 281 views)
File Type: png SilentD.png (50.1 KB, 286 views)
File Type: png SilentE.png (51.1 KB, 284 views)
File Type: png SilentF.png (29.8 KB, 51 views)

Last edited by EmuMannen; 26th May 2016 at 09:26 PM. Reason: Adding the ps.
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Old 26th May 2016, 09:47 PM   #2
EmuMannen is offline EmuMannen  Sweden
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Default Another question about MLTL in general...

I don't know much about MLTL in general and I have never built a Horn, T-Line or MLTL before. I read up on classic T-Line and thought that the 1/4 wave and the length on the line was crucial. I ended up with a length around 2 meters for ~ 40Hz. It seems like the Silent Speaker might have a line length of only 1-1.25 meter (40-50 inch) and that seems way to short (if it got a line at all there is).

But the The Invictus MLTL for example claims to be a MLTL and it seems to be only 42 inch in length (as I see it). What am I missing here?

Last edited by EmuMannen; 26th May 2016 at 09:50 PM. Reason: Clarification
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Old 26th May 2016, 10:17 PM   #3
sreten is offline sreten  United Kingdom
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Hi,

Not the sort of thing you can work out on paper or in normal
simulators. E.g. different bassmids will have different optimum
baffle angles and some of them will be entirely unsuitable.

The point of a MLTL is the length does not determine tuning.
Probably simpler and more sensible to simply go vented.

Noting the taller you make the speaker the worse it will be,
as you ears will be more off axis the higher the cabinet top.

Its a difficult ask, but I'd recommend this tweeter :
https://www.intertechnik.de/Shop/Lou...,en,4842,48646
Due to its excellent of axis performance and probably this :
https://www.intertechnik.com/Shop/Lo...en,3630,115048
Due to its excellently smooth upper range rolloff.

Good luck, its a big ask. Up against a wall and not too tall, you may be able
to get away with a 1st order series x/o @ 3KHz + L-pad on the tweeter. *
I'd suggest about 30 degrees above horizontal for the baffle angle.

rgds, sreten.

* Pure guesswork on my part, don't hold me to it at all.

Last edited by sreten; 26th May 2016 at 10:45 PM.
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Old 26th May 2016, 11:04 PM   #4
EmuMannen is offline EmuMannen  Sweden
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Quote:
Originally Posted by sreten View Post
Good luck, its a big ask.
I know and that's why I had to call for help. Thanks for taking the time, I will go through your answer and see if I can come up with something.
Quote:
Originally Posted by sreten View Post
* Pure guesswork on my part, don't hold me to it at all.
I totally understand and promise not to hold you to it in any way
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Old 26th May 2016, 11:08 PM   #5
wesayso is online now wesayso  Netherlands
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I was pretty sure I had seen those speakers before on this forum.
Perhaps the thread might be an entertaining read for you, as it's mainly about up firing speakers like the "Silent Speaker": http://www.diyaudio.com/forums/multi...ml#post3355294
Click the image to open in full size.

Lot's more variations in that thread.
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Old 26th May 2016, 11:31 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

Wow that is a monster sized thread. 112 pages, 3000+ posts, I don't have the time.

rgds, sreten.

Last edited by sreten; 26th May 2016 at 11:44 PM.
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Old 27th May 2016, 01:01 AM   #7
eriksquires is offline eriksquires  United States
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I'd look up the works of Allison, both his speakers and his papers.

It's not that complicated until you add the TL effects, but as for the angled upward firing, um, just say no. It reminds me a lot of some of the M&K surround speakers. Meh, if they were that good they would have taken off.

You can create a good wall placed loudspeaker, the trick is properly measuring and adjusting for the support the rear wall will give you, and picking a suitable narrow dispersion tweeter, that will minimize side wall reflections.

Of course, a more simple option is to create great, small monitors and use an invisible sub.

Best,


Erik
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Old 27th May 2016, 01:12 AM   #8
eriksquires is offline eriksquires  United States
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Also, keep in mind that the WAF varies with sound quality. If you build spectacular sounding speakers, they'll forgive a lot more than crappy one's even if they can't see them.

Best,

Erik
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Old 27th May 2016, 04:23 AM   #9
Old'n'Cranky is offline Old'n'Cranky  Australia
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throw a sheet over your current speakers ??????
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Old 27th May 2016, 07:57 AM   #10
Lojzek is offline Lojzek  Croatia
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Quote:
Originally Posted by EmuMannen View Post
...I personally love the look of these speakers
but my wife claim that they “take over the room”.
Her wish list is for something small that
“blend with the walls” (white by the way).
Think about in-ceiling and in-wall speakers.
Attached Images
File Type: gif dyn_ip24_front.GIF (145.5 KB, 34 views)
File Type: jpg dyn_ip24_back.jpg (90.6 KB, 34 views)
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