Hi all. I’m looking into a diy speaker project-looking for a stand mount to upgrade from my Harbeth P3esrs. I quite like the look of the seas bifrost-off exis response seems great up until 7000 hz or so, then a 15 db drop between 20 and 40 degrees after that. How consequential would this be for practical listening do we think?
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Seas bifrost
- Thread starter Phorize
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Sorry, cannot help you with your question. Just curious, because I'm planning to make the Bifrost project too. Have you checked some alternatives? Maybe, you found something nice. All what I can find that the Seas Excel woofer and tweeter are excellent. Also, I found some videos on YT and this sounds good, especially for vocal. Thanks!
Done.
OP
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Many thanks!
OP
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I guess that’s the root of my question. I’ve looked around at various measurements of speakers, including uniform directivity designs with wave guides. Im not concerned that the bitfrost design is suboptimal. To the contrary actually. I’m not an expert on speaker design though so was seeking casual opinions on the measurements and design,
Honestly, WRT the response, I would call the midrange a bit forward from 600-2k, emphasizing vocals. I might increase some component values on the lowpass to avoid this, but not the 2.7mH. Maybe a resistor addition as well of about 1-2 ohms added to the cap to help damp that rise in the mids. Also of note- that 1mH in the highpass is likely too large to do the right job. This also contributes to the emphasized lower treble.
Honestly, I feel this could have been done better.
Honestly, I feel this could have been done better.
OP
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Yes, it looks like it may one of those things where the premium cost of the drivers prevents DIYers iterating the design to work out flaws. There aren’t many testimonials out there around these suggesting these get built much.
I concur with the above. The whole thing looks kind of amateurish.. This is the raw response of the driver. The crossover is at 2.2 kHz, right before the nastiness starts. I would have picked an x-over well before 2 kHz, also due to the woofer beaming at that point. There also nothing in the filter to tame the woofer resonance at 4 kHz.
The PDF mentions the sensitivity being low due to baffle step compensation, but in reality, the filter does not include a baffle step compensation network. It's however clear from the frequency response that it needs one.
IMHO this design would need a few things to succeed:
- baffle step compensation for the woofer, might not be needed depending on real-world measurements due to the lower x-over point.
- a notch filter for woofer breakup
- a waveguide tweeter that can be crossed at 1.5 to 1.8 kHz
On the other hand, Troels has a comparable design using a 1st order crossover for the brother of this woofer: http://www.troelsgravesen.dk/CNO-mkIII.htm . At least he addresses the baffle step. Still, 2.2 kHz crossover would be too high for my liking.
The PDF mentions the sensitivity being low due to baffle step compensation, but in reality, the filter does not include a baffle step compensation network. It's however clear from the frequency response that it needs one.
IMHO this design would need a few things to succeed:
- baffle step compensation for the woofer, might not be needed depending on real-world measurements due to the lower x-over point.
- a notch filter for woofer breakup
- a waveguide tweeter that can be crossed at 1.5 to 1.8 kHz
On the other hand, Troels has a comparable design using a 1st order crossover for the brother of this woofer: http://www.troelsgravesen.dk/CNO-mkIII.htm . At least he addresses the baffle step. Still, 2.2 kHz crossover would be too high for my liking.
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BSC does not have to be a separate filter from the lowpass. More often than not, the main lowpass coil tilts the response down until it's flat, and voila(!) there is your BSC.
While I would likely use a notch filter to tame the resonance, they did use a 3rd order electrical that could push it down almost to the point I'd think it was suppressed enough. Remember -25dB is minimum, -40dB is acceptable in most cases, and -50dB is no longer to be concerned with. The Freq Response is the main offender here, breakup present or not.
As to the xover freq, waveguides aren't everyones' cup of tea, and I've been perfectly happy with 2.2kHz in 7" 2-ways before. A lot of tweeters are good to 1.8kHz without one, and this one is no exception.
While I would likely use a notch filter to tame the resonance, they did use a 3rd order electrical that could push it down almost to the point I'd think it was suppressed enough. Remember -25dB is minimum, -40dB is acceptable in most cases, and -50dB is no longer to be concerned with. The Freq Response is the main offender here, breakup present or not.
As to the xover freq, waveguides aren't everyones' cup of tea, and I've been perfectly happy with 2.2kHz in 7" 2-ways before. A lot of tweeters are good to 1.8kHz without one, and this one is no exception.
True that, but one look at frequency response makes it clear that they failed. It’s really not that different from the data sheet.
Yup, I would say it’s optional. Sadly no waterfalls present to actually see how bad it is. It’s a paper like cone, so probably could be fine without notch.
If it is, that should work okay then. Fs is 500 Hz, so from that point it’s probably fine.
What exactly are you looking for? I think the Troels design with similar drivers shows more promise, but it might not be everybody's cup of tea. Also, he never shows any off-axis measurements, so he's missing a fair bit of the puzzle. Doesn't mean it's bad, just that we can't know.
I looked at this for a bit last night, and ended up sort of on the fence about it. In spite of that broad plateau in the response 600 Hz to 1.2 kHz, the response stays within about +/- 2 dB. That's better than an awful lot of speakers, however it will still color the sound slightly, and the emphasis is in a frequency range that would annoy me. If it were a broad -2 dB dip in the same range, it would not bother me.
If I were wanting to build one of the Seas kits and not spend a whole lot, I would given the Idunn consideration. It uses the DXT tweeter, which is the same tweeter used in a number of highly-regarded speakers and is what ctrl and rick are using in the Directiva they are building. ctrl might have some advice to share on how to get more from the tweeter. The woofer used in the Idunn also seems to be much better behaved vs. the one in the Bifrost. Another possible advantage of the Idunn is that you might be able to find a suitable enclosure read made or knock down. I know that this was once true, but I'm not certain whether this is still true. But if it happens still to be true that you can find a suitable enclosure off the shelf, then it should be easy to assemble and the total cost for a pair (buying parts including crossovers from Madisound) will be about $550 + cost of two enclosures. It could make for a nice pair of speakers for not a whole lot of money.
If I were willing to spend more and do something a little more ambitious, I would consider the KingRoy mk III. My only reservation about it is that whereas it is a sealed enclosure speaker, the driver is excellent for ported subwoofer application and not ideal for sealed enclosure application. Were I to build this speaker, I would either go the route of the taller version using dual passive radiator as they suggest, or else make it a ported speaker, with a larger enclosure as needed for a proper ported design using that driver. This is covered adequately somewhere in suggestions and plans for a building a subwoofer using this driver. This would surely be an amazingly good speaker, although not a budget-friendly speaker.
If I were wanting to build one of the Seas kits and not spend a whole lot, I would given the Idunn consideration. It uses the DXT tweeter, which is the same tweeter used in a number of highly-regarded speakers and is what ctrl and rick are using in the Directiva they are building. ctrl might have some advice to share on how to get more from the tweeter. The woofer used in the Idunn also seems to be much better behaved vs. the one in the Bifrost. Another possible advantage of the Idunn is that you might be able to find a suitable enclosure read made or knock down. I know that this was once true, but I'm not certain whether this is still true. But if it happens still to be true that you can find a suitable enclosure off the shelf, then it should be easy to assemble and the total cost for a pair (buying parts including crossovers from Madisound) will be about $550 + cost of two enclosures. It could make for a nice pair of speakers for not a whole lot of money.
If I were willing to spend more and do something a little more ambitious, I would consider the KingRoy mk III. My only reservation about it is that whereas it is a sealed enclosure speaker, the driver is excellent for ported subwoofer application and not ideal for sealed enclosure application. Were I to build this speaker, I would either go the route of the taller version using dual passive radiator as they suggest, or else make it a ported speaker, with a larger enclosure as needed for a proper ported design using that driver. This is covered adequately somewhere in suggestions and plans for a building a subwoofer using this driver. This would surely be an amazingly good speaker, although not a budget-friendly speaker.
OP
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- #17
A 2 way design that’s good down to under 45/50 hz, flat on and off axis (my p3esrs aren’t great in that regard) and sufficient vertical tweeter dispersion to avoid having to stare right down the tweeter to hear higher frequencies (the harbeths are annoyingly narrow vertically). The more I read about the purifi drivers the more I’d consider a 2 way passive along the lines of the March audio speakers but I haven’t come across any diy designs. Re: Troels not giving off axis measurements-that’s a put off for me.
As I implied before, you cannot have both flat on-axis and off-axis responses. If you want flat off-axis, there is usually a rising or peaky response when measuring on-axis. I can understand wanting broad horizontal dispersion, as I prefer that as well.
You might want to look for a design with the midbass above the tweeter. Usually, these designs will fare better above the tweeter axis as the blend is still occurring with the midbass above the tweeter. A lot of designs with the midbass below the tweeter get worse vertically as you stand up. It has mainly to do with the lobing of such designs and how they work.
You might want to look for a design with the midbass above the tweeter. Usually, these designs will fare better above the tweeter axis as the blend is still occurring with the midbass above the tweeter. A lot of designs with the midbass below the tweeter get worse vertically as you stand up. It has mainly to do with the lobing of such designs and how they work.
A variant using a larger (wideband) woofer can be found in the A26 kits.
The link below modifies the original cap only crossover.
https://www.vandomburg.net/audio/seas-a26-improving-the-stock-kit/
The link below modifies the original cap only crossover.
https://www.vandomburg.net/audio/seas-a26-improving-the-stock-kit/