21NDS151U1 Subwoofer 21 inchs - NEODYMIUM SUBWOOFER TRANSDUCERS - hiwell speaker
You go first, measuring is believing.
You go first, measuring is believing.
1. Don't mix different subs! The phase will be different and that will cause more or less cancelling.
2. One of the 21" got 1750 cm² cone surface. Two of the 18" got 2x ~1200 = 2400 cm² cone surface. That means, you lose roughly 30% of cone surface. That's really bad, outdoors that's exactly what counts, cone surface. That gives you much less headroom instead of more!
3. Don't buy noname drivers from china which aren't sold anymore in a year. Why? Not because they might be bad. Okay, that may or may not be the case.. anyway. No, if you kill one, there are no recone kits, you are unable to get a replacement which usually means you have to throw the enclosure away too and a single one remaining is practically useless for you.
The best would be to buy more 18" (maybe 6) which are not too expensive.
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I don't know if the parameters of the driver are that different. I'll look into it.
E: Yes, it would be a very bad idea to mix them, the parameters are vastly different.
E2:
https://www.parts-express.com/pedocs/specs/294-2752--prv-audio-18sw2200-specifications.pdf
https://www.parts-express.com/pedoc...465s-18-inch-pro-subwoofer-specifications.pdf
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Lavoce SAN214.50 is apparently $470 and performs well. It has low Qes, high BL^2/Re so should be good in higher order designs:
dB v2
Ricci's Skram Subwoofer & Files - Bass Projects - Data-Bass Forums
however if you are building sealed or bass reflex you may get more output with two 18".
dB v2
Ricci's Skram Subwoofer & Files - Bass Projects - Data-Bass Forums
however if you are building sealed or bass reflex you may get more output with two 18".
I've had very good luck mixing subs with different drivers, and even different box types...... sealed, reflex, and FLH.
But I always use a crossover at 100Hz and wavelengths are long enough to accommodate phase variations and still provide good summation.
If crossover was higher I can see how different subs might not work so well together.
I also use the same crossover topology...that is, the same electrical LPF to the subs.
This seems to matter the most on the high end of the subs' band-passes, dominating driver/box differences.
On the low end, where the HPF's are in place, it sometimes takes a little juggling to get things right...but the savior is the really huge wavelengths that provide a lot of tuning room.
Bottom line imo, is how well do they sum... how close do they sum to +6dB through the pass-band when measured side by side outdoors, both separately powered.
Indoors? I'd mix drivers/subs in a heartbeat....
The second you put a sub indoors, you've already mixed multiple subs... with all the virtual subs created from room reflections.
This soooo dominates drivers, parameters, even box types etc, ime.
Below is a couple of different subs measured outdoors for an example...
green trace is a really high mass prosound single 18" in a FLH.
Red is a single 18", lower mass, in a bass reflex.
Blue is their summation.
Same linear phase HPF and LPF on both.
First plot is with no EQ on FLH sub or reflex
Second is with EQ on FLH sub to make judging summation easier.
But I always use a crossover at 100Hz and wavelengths are long enough to accommodate phase variations and still provide good summation.
If crossover was higher I can see how different subs might not work so well together.
I also use the same crossover topology...that is, the same electrical LPF to the subs.
This seems to matter the most on the high end of the subs' band-passes, dominating driver/box differences.
On the low end, where the HPF's are in place, it sometimes takes a little juggling to get things right...but the savior is the really huge wavelengths that provide a lot of tuning room.
Bottom line imo, is how well do they sum... how close do they sum to +6dB through the pass-band when measured side by side outdoors, both separately powered.
Indoors? I'd mix drivers/subs in a heartbeat....
The second you put a sub indoors, you've already mixed multiple subs... with all the virtual subs created from room reflections.
This soooo dominates drivers, parameters, even box types etc, ime.
Below is a couple of different subs measured outdoors for an example...
green trace is a really high mass prosound single 18" in a FLH.
Red is a single 18", lower mass, in a bass reflex.
Blue is their summation.
Same linear phase HPF and LPF on both.
First plot is with no EQ on FLH sub or reflex
Second is with EQ on FLH sub to make judging summation easier.
Attachments
The low-cut is an absolutely must-have for PA use anyway.
No, it isn't that easy. You have to compare and look very closely at the excursion. A correct sum does not say how much mechanical and aswell electrical (power) stress is on them. I've seen it several times at some firends event parties, they said "ah, that works suprisingly good" and an hour later half of their mixed subs died. Oversimplifying things isn't helping you at all. You often don't even recognize when the power compression on one of the sub types starts. That's actually the prototype on 'how to fry my subs'.
Well, how did you place the subs? How many subs? Just two? Monostack, 2 stacks r+l, tooth-row, end-fire, cardioid? How/where did you measure it?
The Chinese 21" clone is not equivalent to the 21SW152, not even close at least when it comes to motor force (especially after you figure in the Lossy Inductance) ....
If we are to believe their published parameters the Chinese 21" isn't even as strong as a 21DS115, so is a far cry from a 21SW152 ..
That Chinese neo motor would be ok on an 18" cone, and awesome on a 15" cone ...
If we are to believe their published parameters the Chinese 21" isn't even as strong as a 21DS115, so is a far cry from a 21SW152 ..
That Chinese neo motor would be ok on an 18" cone, and awesome on a 15" cone ...
Could you please explain? I thought motor force scales to BL^2 / Re.
Chinese 21NDS151U1: BL = 32 Tm, Re = 3.6 ohms --> BL^2 / Re = 284 T^2*m^2/ohm
B&C 21SW152 4 ohm version: BL = 32.5 Tm, Re = 3.3 ohms. --> BL^2 / Re = 320 T^2*m^2/ohm
B&C 21SW152 8 ohm version: BL = 39 Tm, Re = 6.0 ohms. --> BL^2 / Re = 254 T^2*m^2/ohm
Then the Chinese motor appears to be similar to the B&C.
The Chinese woofers do not look like clones to me. Their magnets look unlike the B&C woofers except the 21IPAL, but then the basket is different. The pole plate also is different. If the woofers really are clones, I would not buy them. That would be sending money to thieves instead of to the company that put effort in designing them.
Chinese 21NDS151U1: BL = 32 Tm, Re = 3.6 ohms --> BL^2 / Re = 284 T^2*m^2/ohm
B&C 21SW152 4 ohm version: BL = 32.5 Tm, Re = 3.3 ohms. --> BL^2 / Re = 320 T^2*m^2/ohm
B&C 21SW152 8 ohm version: BL = 39 Tm, Re = 6.0 ohms. --> BL^2 / Re = 254 T^2*m^2/ohm
Then the Chinese motor appears to be similar to the B&C.
The Chinese woofers do not look like clones to me. Their magnets look unlike the B&C woofers except the 21IPAL, but then the basket is different. The pole plate also is different. If the woofers really are clones, I would not buy them. That would be sending money to thieves instead of to the company that put effort in designing them.
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TBTL,
BL^2/Re is an oversimplified method when it comes to drivers with high relative inductance like the Chinese driver, because using BL^2/Re alone to compare a driver with high relative inductance to a driver with much lower relative inductance (like the 21SW152) gives the driver with high relative inductance an unfair and misleading advantage when in fact it may have less motor force in the real world (as is the case here).....
For drivers with high relative inductance like the Chinese driver you can use the "Lossy Inductance" feature on Hornresp to adjust the BL down for you and then use that adjusted figure in the BL^2/Re formula in order to give you a better idea about how much "effective" motor force the driver really has ...
The community of builders/designers i have been working with lately have used the "Lossy Le" feature many times with drivers that have high relative inductance and our results do correlate well with the models (in term of predicted curve shape and damping behavior) .........NOTE: The feature is not required with most PA drivers (only certain ones like the iPALs , DS115 series and that Chinese driver...............High Excursion Car Audio subwoofers and Home Theater style subwoofer drivers will require the "Lossy Le" feature in most cases .. )
With Lossy Inductance feature applied (so the BL adjusted accordingly) the Chinese driver ends up with a BL^2/Re of around 150 ....
The 21SW152-8 (for which the feature is not required) has a BL^2/Re of up around 250 as you pointed out .... So in reality the 21SW152 is considerably stronger than the Chinese 21" .. .
To me 'separately powered' means all the concerns you mentioned have been addressed....that is, amps are sized appropriately for each sub, limiters are in place if needed.
I take all that as a given when combining subs, but you do make a good reminder for those who might not.
How placed/how measured ? Really ??
I placed two banks of 8 subs of each type in a inter-weaved hyper-cardiod mobius array, with antimattermerretmerizer phase processing
Or should I say one sub of each type out on the driveway, each alone, and then the pair side-by-side. 8m using Smaart as previously shown.
Well, limiters are a very good tool to keep your subs alive. It depends on the dsp but most limiters aren't RMS limiter but just peak limiter, which doesn't care about how much the average. On ~47Hz you've EQ'd +3dB. That doesn't sound much but it still is double the power. It looks like you really know what you are doing but that 'bit' EQing is something someone else with less experience will very likely overlook. That frequency is well 'populated' and low enough to not notice the distortion, double the power there can very quickly mean exceeding the xmax. The twice the power is bad for someone with less experience because a peak limiter won't catch that, it's simply not possible for it, especally at music genres like dubstep, raggae or others with long duration, low attack, low frequency tones because it will not trigger. Because it likely doesn't even show the limit led you don't have any feedback on the actual power.
How placed/how measured ? Really ??
I placed two banks of 8 subs of each type in a inter-weaved hyper-cardiod mobius array, with antimattermerretmerizer phase processing
That's bad. You obviously didn't use a laser aligned non-phase impacting measurement microphone, only the Binford 9000 hyperlinear GTS-X Mk II mic can do that correctly.
Or should I say one sub of each type out on the driveway, each alone, and then the pair side-by-side. 8m using Smaart as previously shown.
So outside with low to no reflections and the same distance. I was asking to exclude room influence on the measurement or a phase difference because of close mic placement and high runtime difference of a longer row of subs. Sorry for asking that offensively, I wanted to avoid a chat-like series of posts, asking in each for more additional informations because x or y are missing, annoying each other more and more while doing so.
Dang ! Gotta get me one of those Binford 9000's
Thx for the kind explanation re questions.
Yep, regarding RMS and Peak limiting. I routinely keep both in play on all drivers.
And I'm beginning to play with side-chain triggered limiting. I'd like to emulate a sliding frequency high-pass filter for subs, that I've seen in the Linea Research dsp's.
@ Matthew Morgan J
I second TBTL's thank you!
I agree with most of this, especially throwing money away at a product with questionable quality control, no support. What happens when you get a driver with a coil rub, the Qes is way out to lunch, and a coil that isn't centered?
Multiple drivers are always a better idea than one or two good drivers, especially outdoors.
(6) 18's would be a good start for outdoors, and placing the boxes together in a center cluster would give you some forward directivity.
If you bought 6 at a time, the B&C 18TBW100 could be had for around ~ $ 320 street price, maybe a bit less. Sure, it's more boxes, and more money, but the efficiency and headroom gained by running 6 enclosures will offset that somewhat. Perhaps you can sell off your existing set up once you have replacement boxes built and running, which would lower the cost of ownership.
There are less expensive, less capable drivers out there and it all comes down to your choice.
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