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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 28th January 2020, 10:33 PM   #21
scholl is offline scholl  United States
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I use the 12PR310 with good results. Nice punchy sound.
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Old 29th January 2020, 06:51 AM   #22
mbrennwa is offline mbrennwa  Switzerland
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Troels Gravesen high efficiency 3-way looks like a winner.
Quote:
Originally Posted by Beatlejuiced View Post
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. ... Mr. Gravesen claims a sensitivity of 93dB/2.8V/1 meter.
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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...
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Originally Posted by Jonhny View Post
...BSC just isnt such a big deal...
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Originally Posted by 5th element View Post
I don't really see how a phenomenon caused by the law of physics isn't such a big deal. It's present in every stereotypical loudspeaker design in one way another and needs to be accounted for.
We recently developed a speaker in a similar format with similar design goals (the Open Source Monkey Coffin, see here). We used the same Faital 12PR320 woofer, tuned to a slightly higher F3, corresponding to slightly higher SPL. Since the overall sensitivity / efficiency of the whole speaker system is limited by the woofer, and I know the ins and outs of tuning the 12PR320 bass response, I can say that the the 93 dB / 2.83V / 1m number is a bit optimistic. I'd guess it's closer to 90 dB / 2.83V / 1m if the baffle step compensation (BSC) was done right. And yes, cheating with the BSC does give very unbalanced, "thin" sound.

Note how the bass reflex ports are at the rear. These speakers will therefore not work well if they are placed directly against a wall. This means they need to work well in a 4pi environment and therefore full BSC is required.

On his website, Troels shows the SPL curve of the woofer in the box, without the x-over. The curve extends down to 200 Hz, where the SPL is about 94.5 dBSPL. Using a baffle step calculator, the baffle step loss is about 1 dB at this frequency (but it will reach 6 dB at (much) lower frequencies), whereas the final system SPL curve shows about 92 dBSPL at 200 Hz. This means there is at least some BSC, but it's hard to say how much. It would be useful to see low-frequency SPL curves for the woofer with / without the x-over, or a curve showing the transfer function of the woofer x-over.
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Last edited by mbrennwa; 29th January 2020 at 07:03 AM.
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Old 29th January 2020, 08:30 AM   #23
Jonhny is offline Jonhny  Sweden
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Quote:
Originally Posted by 5th element View Post
I don't really see how a phenomenon caused by the law of physics isn't such a big deal. It's present in every stereotypical loudspeaker design in one way another and needs to be accounted for. Whether this means less or more of it needs compensating for depends on the design and intended application but to say it isn't such a big deal is very dismissive.

To me the final steps in balancing a loudspeakers tonal balance involve tuning the BSC and tweeter levels. If either are off by as little as 1dB it can make a design quite unpleasant to listen to. At least to my ears. Now I do have hyperacusis and that makes me more sensitive to speakers that are lacking. An overly forward sound, indicative of too little compensation, hurts to listen to.
I agree with you.

BSC is one of the tools to get frequency response right. It is just a tool. There are others, equally important.
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Old 29th January 2020, 10:22 AM   #24
Joseph Crowe is offline Joseph Crowe  Canada
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Originally Posted by ErnieM View Post
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.
I'm not sure a tweeter like this would keep up with the SPL output this speaker is capable of. The RT850 is only 92.5dB sensitivity and only 12 watts rms power handling. It would quickly go into double digit % distortion especially if the speaker was used in a larger listening space.
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Old 29th January 2020, 11:02 AM   #25
phase_accurate is offline phase_accurate
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When I fist saw the Faital 12PR320 that is used here I was tempted to use it for a louder HiFi application. Does anyone know how it fares in terms of THD and IMD since it doesn't have any shorting ring ?

Regards

Charles
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Old 29th January 2020, 11:09 AM   #26
mbrennwa is offline mbrennwa  Switzerland
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Troels Gravesen high efficiency 3-way looks like a winner.
Distortion data here Open Source Monkey Box
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Old 29th January 2020, 01:39 PM   #27
phase_accurate is offline phase_accurate
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Thanks Matthias.
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Old 29th January 2020, 06:11 PM   #28
mbrennwa is offline mbrennwa  Switzerland
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Troels Gravesen high efficiency 3-way looks like a winner.
Quote:
Originally Posted by Joseph Crowe View Post
I'm not sure a tweeter like this would keep up with the SPL output this speaker is capable of. The RT850 is only 92.5dB sensitivity and only 12 watts rms power handling. It would quickly go into double digit % distortion especially if the speaker was used in a larger listening space.
Here are some test data for the tweeter used in Troels speaker:
http://www.audiocomponents.nl/downlo...i%202017-6.pdf

While this might not be the tweeter with the lowest distortion ever, it certainly does not "quickly go into double digit % distortion". Nothing wrong g with choosing this driver.

Edit: Whoops, just realised you were referring to the Viawave tweeter. Sorry for the confusion.
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Last edited by mbrennwa; 29th January 2020 at 06:13 PM.
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Old 30th January 2020, 11:02 PM   #29
jtgofish is offline jtgofish  Australia
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The appeal of this design to me is that it exhibits a remarkably flat impedance .It measures between 5 ohms and 9 ohms from about 40hz to 20,000hz.That together with its 93 db sensitivity seems to indicate it would work very well with a wide range of tube amps including relatively low powered SETs as well as other current drive high output impedance amplifiers.And there are plenty of users of those types of amplifiers that have not found their ideal speakers and have been pushed into using ridiculous things like a single full range/wizzer coned driver in an even more ridiculous back loaded horn.
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Old 30th January 2020, 11:04 PM   #30
Bigun is offline Bigun  Canada
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Troels Gravesen high efficiency 3-way looks like a winner.
hey careful now, we like our full range wizzers
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