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Wow! Some of the best measurements we’ve seen.
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ASR Directiva Open Source Speaker Review
- Thread starter amirm
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So it sounds like expensive drivers are unavoidable when it comes to certain minimum performance metrics after all?
That about fits, but only if a high pass is used to protect against too much excursion at low frequencies.
The Purifi woofer has a linear excursion of +-10mm and the mechanical limit is +-14mm.
The passive radiator from SBAcoustics has a mechanical limit of +-11mm.
This fits quite well, because at frequencies below 50Hz the PR reaches the limit of maximum mechanical deflection before the woofer and thus protects the expensive woofer (by making itself heard with "agonizing" noises).
Max bass SPL - with HP BW fourth order at 30Hz
The simulation refers to the half-space (2pi), for the full-space we have to subtract 6dB.
This results in a maxSPL@50Hz of about 95dB free-field.
Max bass SPL - with HP BW fourth order at 40Hz
As above, we convert maxSPL to full-space and get about 98dB maxSPL@50Hz free-field.
As I said, this is about what two "normal" 6-6.5'' drivers can do at maxSPL.
But of course the limits set by physics apply here as well.
For such a small loudspeaker the result is very good and with some support of the listening room's boundary surfaces you can add another 3-8dB depending on the speaker position.
Well, the speaker's low bass behavior was tuned rather neutrally. Nothing should stand out there.
In addition, the final fine-tuning is still missing. This usually changes the impression in the low bass range too.
I'm talking about a commercially available speaker pair. How much does it cost to get the same performance? What would those speakers be? Anyone got any great ideas?
Ah, I used the 6 mm Xmax version for my sim. That would mean a bit more output indeed, but still a bit of a compromise in the end. A good one though I think. In the end, you want a small design with a relatively big low end, which this will give. Add a few subs, and this combination will do massive dynamics if needed.
H-713
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Well done guys, very impressive. Pretty much blows every other 6.5" 2-way out of the water.
One thing that I think might be really worthwhile, however, is to do this same process, but use a more economical woofer. Nothing really wrong with the tweeters, but the use of $370 woofers limits the market for this to some degree. It might be interesting to explore a similar project using a Seas or SB Acoustics woofer, sacrificing some bass distortion performance for cost. Perhaps the ER18RNX or the equivalent size SB / Satori woofer.
The Purifi woofers are probably the best on the market... but they're still really, really expensive for a 6.5" driver.
One thing that I think might be really worthwhile, however, is to do this same process, but use a more economical woofer. Nothing really wrong with the tweeters, but the use of $370 woofers limits the market for this to some degree. It might be interesting to explore a similar project using a Seas or SB Acoustics woofer, sacrificing some bass distortion performance for cost. Perhaps the ER18RNX or the equivalent size SB / Satori woofer.
The Purifi woofers are probably the best on the market... but they're still really, really expensive for a 6.5" driver.
As mentioned in a previous reply not long before this, I'd built a similar box and been running it for 8+ months now using the same Purifi 6.5" mid/woofer. Mine used a sealed design so it has somewhat less bass volume but had at least some response extending even lower.
I saw the numbers even before it was built and assumed that it would need a real subwoofer to get excellent low bass and sub-bass, and as the saying goes, I was Not Wrong. I have a 15" Rythmik sealed sub that is in my setup, and the whole stack sounds Glorious.
Frankly, even with EQ, unless you have a dedicated driver for the very low frequencies of less than 20 Hz up to about 100 Hz, you'll lose some of those low frequencies even if you don't miss them due to not being used to getting them.
From looking at the available high-quality drivers and the levels of distortion you get in each range, I wasn't able to make a formula which would work across the whole human hearing/experience range of < 20 Hz (Note I say this because we can perceive less than 20 Hz, just not as directly with our ears) up to ~20kHz without using at least 3 drivers:
- < 20 - ~60-120Hz
- ~60-120Hz - ~1-2kHz
- ~1-2kHz - > 20kHz
EDIT: I'm not talking about "full-range" drivers here of course, but that's a wholly separate discussion...
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You could buy two JBL 308p Mkii speakers (£300 for a pair when on sale) and use my Anechoic EQ, I think it might have better directivity even but not sure, following is a link to my post showing the effect of my anechoic EQ on the Listening Window & On-Axis, along with directivity plots from Amir:
ASR Directiva Open Source Speaker Review
Thanks for the write-up, Rick! So your starting point was already chosen so that the budget goal was already hard to reach? Luckily the excellent tweeter is budget-friendly :) Also, this budget does not include the active parts, does it? Amir's amplifier already costs $999, and you need two of...
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EDIT: updated this post with my own distortion measurements in my room of my 308p speakers after anechoic EQ:
74dB for 2 speakers at 2 meters (my normal listening level):
80dB for 2 speakers at 2 meters (my max listening level):
Other louder measurements up to 88dB:
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It's mention in the review it'd be in the 4-5k range,
H-713
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Not entirely. Revel uses SB Acoustics drivers (~$70) for their woofers, and a tweeter that costs about $50. I'm sure they're getting them a bit cheaper than that too. You lose some performance dropping down from the Purifi, but you do NOT need a $370 woofer to get pretty great performance.
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Thank you!You could buy two JBL 308p Mkii speakers (£300 for a pair when on sale) and use my Anechoic EQ, I think it might have better directivity even but not sure, following is a link to my post showing the effect of my anechoic EQ on the Listening Window & On-Axis, along with directivity plots from Amir:
Distortion of the JBL 308p Mkii is a lot higher though as seen in following pics, but if you don't listen at loud levels then I think it's ok and when I measured my speakers in my room I got lower distortion than that pictured here.ASR Directiva Open Source Speaker Review
Thanks for the write-up, Rick! So your starting point was already chosen so that the budget goal was already hard to reach? Luckily the excellent tweeter is budget-friendly :) Also, this budget does not include the active parts, does it? Amir's amplifier already costs $999, and you need two of...
View attachment 157153
That should be ok. How about back wall and what is distance between speakers?
This is kind of my point. You're paying a lot for miniaturization. For me, it makes more sense to just use subwoofers, or build a larger speaker (traditionally this is where DIY becomes a good value)
After reviewing the measurements more carefully, I think I'm actually impressed by the DI more than anything. The DXT is doing a fantastic job.
Can someone put the bass performance in some kind of reference for me? Better than a Revel f206? Better than a 708p? If it beats either of those, that is a huge win for a speaker of this size.
Also, what is the limiting transducer here? What runs out of juice first, the tweeter (a conventional dome in an odd waveguide), the woofer (a monster) or the PR (which doesn't strike me as that big)?
I'd love to hear some comparitive descriptions of this speaker as it really is a unique design. Is it atmospheric or very focussed? Does the low bass distortion make it sound big or small? Etc.
feel like I'm taking crazy pills
"Genelec 8040s" and "cheaper woofer" throughout the thread... does nobody look at the frequency response? This thing's LF extension is absolutely exceptional, and that is largely because of the expensive woofer. The distortion measurements are absolutely spectacular. It is +/- 2dB, starting at the exact frequency where the 8040 is down 6dB!
These ideas to replace the woofer with a cheaper one to get the BOM down... okay, I guess??? It becomes a completely normal, unexceptional speaker in that case. Dozens if not hundreds of those designs have already been done.
If anything, I want to see this same design with the newer, presumably even more expensive, Purifi 6.5 woofer that has even more excursion... the only cheaper alternative woofer mentioned in the thread so far that stands any hope of maintaining this level of performance would be the XBL^2 woofer from Misco.
"Genelec 8040s" and "cheaper woofer" throughout the thread... does nobody look at the frequency response? This thing's LF extension is absolutely exceptional, and that is largely because of the expensive woofer. The distortion measurements are absolutely spectacular. It is +/- 2dB, starting at the exact frequency where the 8040 is down 6dB!
These ideas to replace the woofer with a cheaper one to get the BOM down... okay, I guess??? It becomes a completely normal, unexceptional speaker in that case. Dozens if not hundreds of those designs have already been done.
If anything, I want to see this same design with the newer, presumably even more expensive, Purifi 6.5 woofer that has even more excursion... the only cheaper alternative woofer mentioned in the thread so far that stands any hope of maintaining this level of performance would be the XBL^2 woofer from Misco.
I would argue that absolute output level and extension are more important than distortion. I'm not sure how this speaker performs in that respect; it seems like the PR and the tweeter would run out of steam before the purefi, but I await comments from the designer.
Let's not compare this to a Genelec. This is a DIY project, and it is a unique value proposition.
FYI, I direct-ordered Purifi's newest sampling X-series aluminum mid/woofer for the similar reason of "why not". My existing build of using Purifi's 6.5" X-series mid/woofer plus a Raal 70-20XR is likely already at or beyond the limit of anything I can detect with my ears, but I'm doing another build with their newer mid/woofer plus a full Raal 140-15D, which also has greater frequency extension and lower distortion.
Again, I doubt I will be able to tell the difference, but it's about doing it for Fun at this point anyway.
I'm not the one comparing it to a Genelec - there are many posts in the thread doing exactly that, though, and I agree with you. They are completely off base.
To be honest I myself, don't particularly care about headroom once you get up past 90dB or so. It has more than enough as is. This looks like it'd make for an absolutely exceptional studio monitor, vastly superior to anything else in its price range or even well above. Has extension almost equivalent to my KH310s, in a much smaller cabinet, with better directivity - although the vertical notch is a bit of a bummer. Not sure how that factors in nearfield but a monitor that doesn't need a ceiling cloud would be great.
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