My opinion is that resonator systems of any kind are bad. But I understand their effect (net benefit) is ok with passive 3-way woofers and subwoofers. PRs have more radiating area but are bad with high excursion, it is a good rule to use double number of passives to active(s). Location of the port or radiator should be on the backside or downside towards floor.
My simple measurements above have only anecdotal value, but give reason for further studies.
My simple measurements above have only anecdotal value, but give reason for further studies.
There is something 'in-between' a passive woofer and a passive radiator >
It is what I call an "Actively Assisted Rear Radiator". ( a form of bass reflex )
The basic concept is that of using a decent quality 4ohm Car Sub. of low Fs driven by a very high mH + high DCR inductor.
The 3 or 4 ohm DCR of the inductor raises the very low frequency impedance and renders the 'rear sub' as semi-driven. ( assisted )
Apon experimentation, I have found it extremely effective at producing VERY LOW FREQUENCIES. Rear mounting appears to be key.
Experimental tuning IS obviously required.
PS. High value inductance but also high DCR keeps cost low.
You could think of an ordinary sub driver too… since passive radiators seldom are very cheap, the price jump to a driver isn’t that big. But the expenses for X-over components make the BC worse of course.
So you don't like speakers at all? 😉😁
With PR's you quickly run into budget issues as well.
Especially with consumer prices, it's often as easy to go for two woofers instead.
Even more so when a active or active-hybrid system is being used.
A PR system often rolls off steeper as well compared to a ported system.
I personally find them only useful in very small compact systems.
Where a port will just be simply to large.
Or systems that have a very low tuning.
Still, you often run into the excursion limits of the PR.
We don't even take the predictability into account.
A closed box is far more predictable and tolerances etc are not nearly as bad compared to any higher order system.
So you don't like speakers at all? 😉😁
Yessir! Live music and singing without any aplification is what like best 🙂
Yessir! Live music and singing without any aplification is what like best 🙂
Yes.
Looking a SB17NBAC35-8 driver in a BR enclosure the port depending on diameter will be in the range of 24 to 36 inches long.
Another thing about the SB17NBAC35-8. The ceramic version of the SB17 has a very limited X-Max and very high IMD. Without the bass frequencies included in the IMD testing the mid frequency IMD is much lower. As measured by Erin's Corner.
SB Acoustics SB17CAC35-4 6 Inch Ceramic Midwoofer Review
The Purifi 6 1/2 inch is looking much better for a smallish speaker. It has a much better X-Max and IMD.
Thanks DT
This is not really all that hard to understand. The coil across the assisting woofer will increase attenuation of the driving current with increasing frequency, leaving the bottom end with the least resistance. My guess would be 6-12mH, depending on your goals. This could help with peaking above the passive rolloff to keep it flatter if the used woofer has substantial Q or higher than average ripple.
By contrast, a cap across the assisting woofer would open with increasing freq, and cause a braking effect as frequencies decrease.
Almost,
The only thing that isn't great about the SB17 woofers (same for NBAC etc), is the Kms(x).
But as we can see from Klippel;
https://www.diyaudio.com/community/...l-x-for-mid-ranges.376164/page-7#post-7703832
A non-linear Kms mostly results in HD distortion, and even just for the low-end.
It doesn't affect IMD and/or multitone distortion that much.
The difference you're seeing in Erin's review, is probably mostly coming from BL(x)
Unfortunately Erin never tested mutlitone with a 100-120Hz HP (only 80Hz).
I have a strong feeling that the SB will do extremely well in that case!
Even with 80Hz HP, it's not that far off from Purifi and ScanSpeak.
Btw, high-excursion small drivers are actually a very good example of a bit of a strange compromise.
To keep up with the high driver excursion, you basically need two well made PR's, as well as a bigger cabinet.
Which forces people in a very odd choice, because a cabinet with a truncated 5 inch woofer will be roughly the same size.
I also think the PR's will run out of cone excursion before the high xmax driver does.
Or will be just (very) expensive.
The cone excursion of a 5 inch woofer can be about 87/50 = 1.7 times less.
So instead of a whopping 8.5mm we only need about 5mm
Which is no big deal for a average 5 inch woofer.
Or you need to go for a double 4 inch active closed box.
But in that case a truncated 5 inch driver is also much cheaper.
The only use case I can come up with, is when things just really have the look small.
So tons of excursion might sound cool with a small driver, in practice you just run into all sorts of compromises.
Not to speak about the sub-optimal parameters for some of the smaller PR's.
Because you need a relative high Vas, otherwise the response with a PR won't be that great.
With PR units it is very easy to go to extreme excursion (Xmech), because there is no motor controlling oscillation. Around Fs they perform rather linearly in and out, but other than sine waveforms like transients are difficult (I guess). This is not so promlematic with movie effects and subwoofers, but smaller and higher tuned and higher lowpassed speakers are questionable.
Aresent thesis of PRs https://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=9148050&fileOId=9148052
The project findings brought about a selection of important parameters to be considered when developing products with passive radiators. The project also resulted in defined test methods for measuring these parameters and detailed procedures for analysing the collected data information. Furthermore, the comparison between measured values and simulations led to reflections regarding tuning adjustments and the trustworthiness of above-mentioned test methods.
Aresent thesis of PRs https://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=9148050&fileOId=9148052
The project findings brought about a selection of important parameters to be considered when developing products with passive radiators. The project also resulted in defined test methods for measuring these parameters and detailed procedures for analysing the collected data information. Furthermore, the comparison between measured values and simulations led to reflections regarding tuning adjustments and the trustworthiness of above-mentioned test methods.
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The same Kms(x) problem also counts for PR's.
I wouldn't actually mind a PR with just a dead flat Kms(x) curve, or very close.
Wait, I did not think that last post completely through. Shorting the voice coil brakes it. Therefore movement will be minimum.
Of course, I may be understanding @Mister Audio incorrectly about how the assisting woofers are wired, but in terms of PRs, they are normally not connected to signal wiring at all. If they are wired up, and the coil is in series with the secondary woofer, then it is only a very low passed cascaded x.5way assistant. This would make sense as the assistant would only play very low bass.
However, if used like I proposed in my last response with the coil connected across the terminals of the assistant woofer, this won't work in the lower regions at all. My theories were backwards before. A coil will pass connection in lower frequencies, and the coil will then brake. Adding resistance and going up in frequency reduces the effective braking system.
A capacitor would therefore be the better suggestion in this configuration. As the frequency decreases, the current will conduct less and allow travel.
Of course, I may be understanding @Mister Audio incorrectly about how the assisting woofers are wired, but in terms of PRs, they are normally not connected to signal wiring at all. If they are wired up, and the coil is in series with the secondary woofer, then it is only a very low passed cascaded x.5way assistant. This would make sense as the assistant would only play very low bass.
However, if used like I proposed in my last response with the coil connected across the terminals of the assistant woofer, this won't work in the lower regions at all. My theories were backwards before. A coil will pass connection in lower frequencies, and the coil will then brake. Adding resistance and going up in frequency reduces the effective braking system.
A capacitor would therefore be the better suggestion in this configuration. As the frequency decreases, the current will conduct less and allow travel.
I believe the Vandersteen 2C speaker used a bass concept similar to post #222 and #228. For those who are unfamiliar, the 2C was a 3 way speaker with an 8" woofer. It used a 12" passive radiator, but this PR was a woofer with a motor. I believe it was connected to a network of some kind, but the network was isolated from the rest of the speaker crossover. The PR/woofer was not driven electrically.
If anyone has detailed knowledge of the Vandersteen 2C bass alignment, I would be interested in hearing your thoughts. That speaker was in production for a very very long time.... a very successful design.
If anyone has detailed knowledge of the Vandersteen 2C bass alignment, I would be interested in hearing your thoughts. That speaker was in production for a very very long time.... a very successful design.
Jim,
Unfortunately I don't have detailed knowledge of the 2C's bass alignment. But many moons ago, I did get to listen to this at a hi-fi retailer. I think this was in the late C20, or early C21 in a large well upholstered and carpeted room. It was a bit of an anti-climax, I suppose, having read all the magazine reviews about it.
I was very pleased when I found out our dear @bikinpunk reviewed this speaker here
I'll leave your analysis/interpretation to you..
Unfortunately I don't have detailed knowledge of the 2C's bass alignment. But many moons ago, I did get to listen to this at a hi-fi retailer. I think this was in the late C20, or early C21 in a large well upholstered and carpeted room. It was a bit of an anti-climax, I suppose, having read all the magazine reviews about it.
I was very pleased when I found out our dear @bikinpunk reviewed this speaker here
I'll leave your analysis/interpretation to you..
Passive radiator or port is supposed to work around Fs only, to compensate spl roll-off. I can't give extra spl capacity. It reduces distortion around Fs compared to sealed too.
Extra woofers' main purpose is to give more spl capacity by having larger radiating area, and with dsp or LT circuit some more low freq extension. With extra capacity also distortion at normal levels is lower. By using eg. twin 8" units directivity and cone resonance problems are easier than with a single 12" unit,. In subwoofer application this is irrelevant.
Passive radiator = woofer without motor assembly. It has same spider and cone edge surround as active unit. I don't believe that many commercial producers desings them from blank paper on.
Normal woofer with some specific circuit as assisting unit is interesting idea, but not cost-effective.
Double units in series is best, safe with impedance. You can save a bit by choosing units with less Xmax. Most are in parallel to get more spl, at the expence of impedance. .5 principle is rather easy but large coils are expensive. In closed box twin actives can go with moderate box volume ( I have done and measured three double serial woofer systems)
With dsp it is easy to use own channel for second active woofer, and you can do tricks with delay. But it's expensive...
Many desingers like heavy non-resonant cabinets, me too. This is the basic reason for me to hate passive radiators. I couldn't find measurements of eg. Focal Shape series monitors. 2-way with passives is a catastrophe in my eyes, but reviews are good https://www.soundonsound.com/reviews/focal-shape-65
Extra woofers' main purpose is to give more spl capacity by having larger radiating area, and with dsp or LT circuit some more low freq extension. With extra capacity also distortion at normal levels is lower. By using eg. twin 8" units directivity and cone resonance problems are easier than with a single 12" unit,. In subwoofer application this is irrelevant.
Passive radiator = woofer without motor assembly. It has same spider and cone edge surround as active unit. I don't believe that many commercial producers desings them from blank paper on.
Normal woofer with some specific circuit as assisting unit is interesting idea, but not cost-effective.
Double units in series is best, safe with impedance. You can save a bit by choosing units with less Xmax. Most are in parallel to get more spl, at the expence of impedance. .5 principle is rather easy but large coils are expensive. In closed box twin actives can go with moderate box volume ( I have done and measured three double serial woofer systems)
With dsp it is easy to use own channel for second active woofer, and you can do tricks with delay. But it's expensive...
Many desingers like heavy non-resonant cabinets, me too. This is the basic reason for me to hate passive radiators. I couldn't find measurements of eg. Focal Shape series monitors. 2-way with passives is a catastrophe in my eyes, but reviews are good https://www.soundonsound.com/reviews/focal-shape-65
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How about that for a state of the art speaker 😳
https://www.monoandstereo.com/airpl...zxqTsBWMNiSNRl7m0g_aem_rW4BPei9Oj6c9rlfUf2TMg
https://www.monoandstereo.com/airpl...zxqTsBWMNiSNRl7m0g_aem_rW4BPei9Oj6c9rlfUf2TMg
What is different from what I said?
The SB17 drivers have limited X-Max. Keep in mind X-Max for a woofer means 10% distortion. In the case of SB17 mid-bass drivers high bass distortion translates to much increased mid-range IMD or amplitude modulation ... what ever you want to call it, it is very much auditable.
"With the relatively high sensitivity, low linear excursion and the various distortion data I have provided (HD, IMD and Multitone) all indicating high levels of low frequency distortion at higher volumes, it seems evident this drive unit is more suited for midrange duty as opposed to being crossed low (roughly an octave above Fs) in a 2-way system. The midrange distortion numbers on this speaker are incredible. Though, as the IMD data indicates, a high-pass filter nearing Fs (44Hz), the midrange “cleanliness” goes out the window. So, cross this appropriately. The typical 80Hz would be a starting point but I think even higher (100Hz) might make more sense, especially if you plan to listen at loud levels. Cross your subwoofer higher to make up the difference."
From Erin's review
Thanks DT
We were talking about the Kms(x), but the Kms(x) is not responsible for the IMD.
See Klippel information of link shared above.
The Kms(x) is the limiting factor the SB drivers.
That being said, all other parameters are obviously also less compared to Purifi.
But what's really interesting to see, is that if we remove excursion component, the SB isn't doing so bad after all. It actually performs very similar.
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Depending how they are being used, but I often advice against putting them in series, because the same BL(x), Le(x) and Le(I) will influence them.
You also very quickly run the the risk of running against the max voltage capabilities of the amplifier.
8ohm in parallel is for most amplifiers no problem.
Can be a bit tricky with passive filters sometimes