Troels Gravesen high efficiency 3-way looks like a winner.

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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.

Does this design use BSC? The system sensitivity is very high, i.e. close to the sensitivity of the bass driver...

...BSC just isnt such a big deal...

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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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.
 
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.
 
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/download/scan-speak/D2608-913000 - Hobby Hifi 2017-6.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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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.
 
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.


Yes but it seems to me the Monkey Coffin project just turned into a competition to see who could squeeze the biggest number of crossover components into one speaker.When what many of us want is the minimum number.
 
Yes but it seems to me the Monkey Coffin project just turned into a competition to see who could squeeze the biggest number of crossover components into one speaker.When what many of us want is the minimum number.
Oh, I too was really excited about the Open Source monkey coffin, but the designer(s) priced themselves out of 99% of diyers ($3k per pair BOM), and asked for financial suppprt for the project, in the end making it quasi-financially backed near-one-off, with awesome documentation along the way. I am curious about the BSC in Troels design, but it is far and away a more accessible project, and closer to what I wish OSMC would have been.
 
open source works best if one person with a vision creates and releases th3 first version. too many folk vying to contribute rarely works, you know the story of the committee set up to design a horse and produced the two hump camel.... anyhow this thread is not about some monkey coffin debacle.

Anybody planning to build Troel’s speaker ?
 
The remarkably flat and benign impedance curve[red line].It is within 4ohms from 30Hz to 20000Hz and has a minimum of 5 ohms.That sort of result is extremely rare and arguably as close to perfect as you are likely to see.

Faital-3WC_sin-imp_v1.png
 
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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...

The remarkably flat and benign impedance curve[red line].It is within 4ohms from 30Hz to 20000Hz and has a minimum of 5 ohms.That sort of result is extremely rare and arguably as close to perfect as you are likely to see.

I couldn't agree more! Even not-so-weak amps would benefit from such speakers! Troels design looks great, and I would certainly like to hear it with my own ears.

Yes but it seems to me the Monkey Coffin project just turned into a competition...

Oh, I too was really excited about the Open Source monkey coffin, but the designer(s) priced themselves out...

Don't be shy and post your comments in the OSMC thread so the right people will see them.

That said, Troels Faital-3WC and the OSMC are similar in some ways, but they are also very different in others. Nothing wrong with that.
 
The remarkably flat and benign impedance curve[red line].It is within 4ohms from 30Hz to 20000Hz and has a minimum of 5 ohms.That sort of result is extremely rare and arguably as close to perfect as you are likely to see.

Faital-3WC_sin-imp_v1.png

green line doesn’t look too shabby either...
 
Interesting. I have been looking at exactly the same drivers (except for the woofer).
Have come to the conclusion that the ScanSpeak D2608/913000 tweeter is one of the best (cost no object) to be used in a waveguide and crossed really low at around 1 kHz.
Have been wondering if the Faital mid will actually be better (sound better) than a SB SATORI MW19P-4 as a mid/low-mid in a cardioid design?
 
I don't have any 3-way speakers. My commercial speakers are all 2-way (or 2.5) and my DIY speakers are all 1-way. I'm quite interested in this 3-way project but I have some questions I'm still mulling over

a) why is the tweeter on the centre line of the baffle and not offset for better diffraction pattern ?
b) the woofer has a paper gasket that looks a bit meh when mounted on front, can the woofer be mounted behind the front baffle for better looks ?
 
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