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Multi-Way Conventional loudspeakers with crossovers

Troels Gravesen high efficiency 3-way looks like a winner.
Troels Gravesen high efficiency 3-way looks like a winner.
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Old 24th January 2020, 04:57 PM   #1
Beatlejuiced is offline Beatlejuiced
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Default Troels Gravesen high efficiency 3-way looks like a winner.

Troels Gravesen recently published a speaker design on his website that looks like it could be perfect for those with low-wattage tube and Class A transistor amplifiers. The speaker is a 3-way unit built with a ScanSpeak tweeter and Faital pro PA woofer and midrange. The crossover is a simple LR2 design at 500Hz and 2400Hz, and the cabinet is a bass reflex box of Baltic Birch which appears to be fairly easy to build.

Mr. Gravesen claims a sensitivity of 93dB/2.8V/1 meter. His measurements show a very flat frequency response which appears to be plus or minus 2dB from 100Hz to about 15KHz, and off axis it deviates from that only slightly at 30 degrees. Based on the raw driver specifications and the box size of the speaker, it appears that bass extension should be about F3=48Hz and F6=42Hz, enough bass for most varieties of music. Mr. Gravesen rates it as an 8 ohm speaker, and the impedance never goes below 5 ohms at any point, so it should be an easy load for most amplifiers.

I am no expert, but I believe this to be a remarkable design and I think it shows Mr. Gravesen's expertise clearly. If I were in the market for a DIY speaker this is the one I would build. I think it is perfect not only for the low-wattage folks but also for speaker building Newbies that want to get their feet wet. It can be found at www.troelsgravesen.dk/Faital-3WC.htm.

Last edited by Beatlejuiced; 24th January 2020 at 05:24 PM.
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Old 24th January 2020, 08:55 PM   #2
ErnieM is offline ErnieM  United States
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Nice to see more prosound products in his designs, though I would've gone for a Viawave waveguided ribbon for tweeter use. Looks to be about the best tweeter for home use above 2.5khz at the moment.
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Old 25th January 2020, 12:00 AM   #3
Pygmy is offline Pygmy  Netherlands
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I think most of Gravesen's designs are winners, the issue for most people is the cost.

These seem to be actually affordable for the beginning DIY enthousiast for a change!
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Old 25th January 2020, 02:02 AM   #4
LineSource is offline LineSource  United States
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12" Faital 12PR320

...One designer's ported woofer -F3 ~ 50Hz in Troels Faital 3WC

...Is another designer's sealed midrange -F3 ~ 75Hz between a horn tweeter and a couple 24Hz sealed woofers
--------

"Back in the day" Acoustic Research - AR - built a two-panel front baffle with a fixed baffle for the 12" woofer, plus a separate baffle board for the tweeter+midrange which could be rotated 90-degrees for cabinet side placement in large bookcases. Just add a baffle step boost ckt + switch.

FOUR PLACEMENTS FROM BAFFLE ROTATION

M
T
W
---------1
T
M
W
---------2
TM
W
---------3
MT
W
---------4
Differences in baffle edge distances become less critical near walls, on desks, and in bookcases
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Old 25th January 2020, 11:27 AM   #5
jtgofish is offline jtgofish  Australia
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Yes it looks very interesting.I too have reservations about using a typical dome tweeter with those PA type mids and woofers but it might be OK.From what I have heard bullet or slot type tweeters tend to integrate better because their inherent sensitivity is a closer match.
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Old 25th January 2020, 11:14 PM   #6
Bigun is offline Bigun  Canada
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Troels Gravesen high efficiency 3-way looks like a winner.
looks like a nice project.

the woofer looks designed for mounting against the rear of the baffle, somehow the exposed paper gasket on the front isn’t ideal to my way of thinking

interesting that the tweeters were not offset from the centre-line
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Old 27th January 2020, 02:11 PM   #7
cph2000 is offline cph2000  Denmark
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Does this design use BSC? The system sensitivity is very high, i.e. close to the sensitivity of the bass driver...
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Old 27th January 2020, 02:47 PM   #8
5th element is offline 5th element  United Kingdom
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Quote:
Originally Posted by cph2000 View Post
Does this design use BSC? The system sensitivity is very high, i.e. close to the sensitivity of the bass driver...
I've always criticised Troels designs for their apparent lack of attention to BSC. Either his quoted sensitivity figures are erroneous or he doesn't compensate correctly. His measurements aren't usually detailed enough to see exactly what's going on and his crossover values are hidden.

With some designs such as with a floor loaded bass driver or 2.5way implementation mean that BSC doesn't need to be traditionally applied, but Troels sensitivity figures always tend to imply that very little attention has been paid to it.

He also tends to crossover way too high to tweeters for optimal off axis performance.
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Old 27th January 2020, 03:07 PM   #9
Bigun is offline Bigun  Canada
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Troels Gravesen high efficiency 3-way looks like a winner.
Interesting.

This latest design of his has the woofer not that far off the floor and this is not one of the trendy narrow-baffle types either so perhaps there's nothing to worry about here.

He does usually show more information on measured cross-over details, perhaps he has limited the information to prevent easy-cloning by folk who don't want to be forced to buy audiophool caps and coils.
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Old 27th January 2020, 03:22 PM   #10
Jonhny is offline Jonhny  Sweden
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I must have measured and developed close to a 100 speakers using the Clio now. BSC just isnt such a big deal. I have used all sizes of baffles, and very small speakers require some BSC, but nothing close to what people seem to belive. Big baffles like the Faital-3WC I would guess needs very little, if any.

This construction is one that I would stay away from though. Troels has many excellent designs to choose from. F6 at 42Hz in a box I would call big already. No, make it bigger and use two woofers for F3 of 32Hz.
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