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Outdo B&C 21DS115 and upgrade to modular subs
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gen0me View Drop Down
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Originally posted by Crashpc Crashpc wrote:

Sorry to "disturb you", but how is DS115 and IPAL not suitable for BR enclosure?
Speakers with very low qes show on sims much stronger bump from a port. So to make response relatively flat they should be enclosed in small rear chamber. Obviously port size has to stay big for such speaker which leads to stupidly huge vents in comparison to rest of the enclosure. Unless ports are flared.
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I meant what are ports lengths in your box from the photo
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Elliot Thompson View Drop Down
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Originally posted by Crashpc Crashpc wrote:




Elliot: I haven´t seen any better suited drivers around, before even thinking about my wallet. So, that is empty claim for me at this moment.

 

Faital Pro, Beyma, RCF, Eighteen Sound (Which is a spin off from RCF) There are so many companies that cater for reflex enclosures on the Pro Audio scene.   

 

 

 

Originally posted by Crashpc Crashpc wrote:

"Once you understand what the TS Parameters means" is not even funny. How do you think did I end up with 21DS115 driver in my hand, developing my own enclosure for it? C´mon. :-)


 

That is your first large driver so you are going to be bias towards it. We have all been there. However, as you start to explore different drivers from different manufactures you will realise there are better suited drivers for the job when you are trying to achieve frequencies your current driver is lacking.

 

 

Originally posted by Crashpc Crashpc wrote:

I don´t need to pick two. I need to pick best compromise of all three. Otherwise I would end up with some extreme. Like EAW BH760, or M-Force, or something along the lines.

 

Then you can kiss 25 Hz goodbye and settle for a flat response to 40 Hz with a -3 dB @ 35 Hz. That is pretty standard on a pro audio reflex box.  

 

 

You had the right frame of thought at the beginning of using multiple small drivers per 180 litre enclosure. Such a concept would lead you more towards your goal. A 180 litre enclosure is humongous for a pair twelve’s as opposed an 18 inch driver. This will allow you to reach your goal (25 Hz) easier than living on your equaliser and forcing the driving to produce sub frequencies in an inadequate enclosure and/or using a driver incapable to produce such frequencies.  


Around 10 years ago I designed two subs for my Mum. Each cabinet is 4 cubic feet housing a single 8 inch woofer (car speaker). The end result is -3 dB normalised gain @ 28 Hz. While 4 cubic foot would be extremely small for a 15 more so 18 inch driver, in which you would be flat to around 60 Hz, it is gigantic for a 8 inch woofer.  





Best Regards,




Elliot Thompson
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gen0me: I see. This is the approach used for conventional designs.
We don´t really need that as a goal any more in age of cheap superior hardware, DSPs and such.

What happens with high motor force low Q driver is, that the driver doesn´t get dampened by the imposed accoustical impedance (caused by the resonator) that much. The driver simply "doesn´t care" and feeds the circuit efficiently. You get the bump. And so what, you can dial it down, right?

Same as user corell wrote: "In a given volumen and port size and with equalizing available, TSP do not matter in the lowest octave. Max SPL is simply determined by Sd * Xmax."

It works both ways. EQing weaker driver output up, or tuning stronger driver down.

You are spot on, on the port size though. That is a real problem here, when one really needs to go down in frequency response. But not really, for the same SPL. It only shows its ugly head, when you need adequate port for the beasty driver, in expectation of significantly more power output.
And that is not issue of the Qs alone at least. It´s rather unrelated. You don´t need squared 500cm of port area for weak driver, right?

I´m trying to achieve some "exceptional niche stuff". Otherwise I would not need to ask anything. Just slap the Q 0.4 driver in a box volume that sims nicely, and we´re done.
No, we´re pushing some boundaries here! :-)
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Elliot:
Quote Faital Pro, Beyma, RCF, Eighteen Sound (Which is a spin off from RCF) There are so many companies that cater for reflex enclosures on the Pro Audio scene.

Yes, except for Eighteen Sound (to my knowledge), I could have these drivers available to me.
Yet I fail to see how these are better suited for my project. Can you explain?

Quote That is your first large driver so you are going to be bias towards it.

Ufff.
No, it is not my first large driver. Owned 18NW100, 18TBX100, 18SW115, RCF 18G401, I have handled and built and listened bootload of 18"s, and thanks to very nice local companies promo, I got to listen to various (dozens) of other solutions, even open air. Single driver subs, multiple driver subs, stacks, cardioid stacks, LAs, all kinds of enclosures. From 8"s to 21"s and double 21"s.
How do you even classify large driver?
Seems that people are wanting 21DS115, measurements are awesome, outcomes are awesome, front-line builders and developers/DIYers use it, if they are in the market for the class. Everybody is totally biased to a point that I don´t know what I´m doing. Like, really, not to bash anybody, just grab on something technical, usable. All this is of no use for anybody here.

Quote
We have all been there.


Doubt so. The hardware is much evolved now, and quite different.

Quote
However, as you start to explore different drivers from different manufactures
I can see how you proceeded with that expectation and imagination. That is not where I am.
Doesn´t work on my person.

Quote
you will realise there are better suited drivers for the job when you are trying to achieve frequencies your current driver is lacking.
Not any I would know about. Noone even suggested a thing really.
The driver is not lacking really. It was just built for certain goal and purpose. That changed. As I listed through other drivers, it looks like the other drivers are lacking the same way, so to speak.

For the original mindset - it is very easy to just say. But when you try to cound, draw and sim, you will realize that there is no "escape" to better solution in the given "accumulated" box volume.
I have been trying to simulate multiples of 8"s and 10"s from Dayton, Peerless, Sundown and others, and it ends up very "inadequate" in sizes, amounts, prices and so on, compared to larger, powerful drivers. One needs 8  10" Daytons to match the 21DS115, or barely overpower it (insignificantly), and 10 pieces to start the upgrade. That is $1000 without postage from USA to EU, for matching one $580 driver. $1250 to outgun it. So much for "suitability" and better drivers.


Edited by Crashpc - 11 December 2018 at 4:49pm
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Elliot Thompson View Drop Down
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Originally posted by Crashpc Crashpc wrote:


What happens with high motor force low Q driver is, that the driver doesn´t get dampened by the imposed accoustical impedance (caused by the resonator) that much. The driver simply "doesn´t care" and feeds the circuit efficiently. You get the bump. And so what, you can dial it down, right?

Same as user corell wrote: "In a given volumen and port size and with equalizing available, TSP do not matter in the lowest octave. Max SPL is simply determined by Sd * Xmax."

It works both ways. EQing weaker driver output up, or tuning stronger driver down.




If you encounter a bump in the frequency response over 0 dB  (+3dB to +5dB) normalised gain it could be due to the cabinet being too small. Under those conditions the speaker will always ring at that particular frequency regardless of equalisation. That is a common trait when you put an under damped loudspeaker in an inadequate box.    

The over damped driver has its issues as well as you will need to live on your equaliser to increase the loss of the desired frequencies which in turn, relies on xmax to make up the loss.

The under damped driver would have a peak at a particular frequency not needing xmax in order to  achieve the SPL at that particular frequency.

So you would have one driver at a stand still producing a lot of bass, and the other moving erratically trying to produce a lot of bass  due to heavy equalisation .

Best Regards,


Elliot Thompson
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Elliot: 
Quote If you encounter a bump in the frequency response over 0 dB  (+3dB to +5dB) normalised gain it could be due to the cabinet being too small. Under those conditions the speaker will always ring at that particular frequency regardless of equalisation. That is a common trait when you put an under damped loudspeaker in an inadequate box.
Could. That is the magic word.  I have good reasons to believe it is not the case here, with overdampened low Q driver with so much restoring force that it is not even funny....
It doesn´t ring here really. It comes from (different than port tuning frequency) "I have so much force, but I don´t have how to transfer it to the air" to "I have so much force to use on this accoustical circuit (impedance) that it doesn´t stop me, so the output will be great."
That what happens to a strong driver. Sure, it needs corrections and EQ, but It is quite far to call it simply ringing. I would attribute weak driving potential and "being pushed by circumstances of the circuit" to ringing word.


Edited by Crashpc - 11 December 2018 at 4:57pm
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Originally posted by Crashpc Crashpc wrote:

 

 

Not any I would know about. Noone even suggested a thing really.

The driver is not lacking really. It was just built for certain goal and purpose. That changed. As I listed through other drivers, it looks like the other drivers are lacking the same way, so to speak.

 

For the original mindset - it is very easy to just say. But when you try to cound, draw and sim, you will realize that there is no "escape" to better solution in the given "accumulated" box volume.

I have been trying to simulate multiples of 8"s and 10"s from Dayton, Peerless, Sundown and others, and it ends up very "inadequate" in sizes, amounts, prices and so on, compared to larger, powerful drivers. One needs 8  10" Daytons to match the 21DS115, or barely overpower it (insignificantly), and 10 pieces to start the upgrade. That is $1000 without postage from USA to EU, for matching one $580 driver. $1250 to outgun it. So much for "suitability" and better drivers.

 

 

Two Eminence LAB 12’s in a 180 litre box tuned to 28 Hz gives you = 3 dB @ 26.13 Hz Normalised Gain.  Since you said multiples I would imagine you would have a minimum of 4 bins. I cannot see how one B&C 21 DS115 can keep up to four Double Twelve’s just based on the Vd alone.

 

B&C 21 DS115 = 2483 cc Vd

Eminence LAB 12 (QTY 8) = 5220 cc Vd

 

The above is not even taking the coupling effect in the equation for no simulator offers a coupling effect.

 

As I have no idea the size of the enclosure you utilised the B&C 21 DS115 in, I used a 180 litre enclosure as well. Bear mind, the best response I got from this speaker was – 39.03 Hz (Tuned at 40 Hz)in a 180 litre enclosure.

 

At 26 Hz, the B&C 21 DS 115 is –17 dB Normalised Gain whereas, the Eminence LAB 12 is -3 dB

 

At 3200 watts, A single B&C 21 DS115 offers the same output as four Double Twelve’s (Eminence LAB 12) from 100 Hz – 37.5 Hz. Below 37.5 Hz,  Four Double Twelve’s maintain a constant output until 25.7 Hz. Bear in mind you have a -21 dB loss @ 25.7 Hertz all courtesy of a single B&C 21 DS 115 compared to four Double Twelves.  

 

Four Double Twelve’s (Eminence LAB 12) 131 dB @ 25.7 Hz

One B&C 21 DS 115 110 dB @ 25.7 Hz

 

From an amplifier standpoint you would need feed the B&C 21 DS115 400,000 watts to achieve the same output of four Double Twelve’s (Eminence LAB 12) getting 3200 watts (400 watts per driver) to achieve the same SPL @ 25.7 Hz.  

 

That is not taking the coupling effect in the equation so you can expect four Double Twelve’s to surpass a single B&C 21 DS 115 bin in terms of SPL overall.

 

I understand the issue of price. I would suggest finding twelve inch drivers very close to the Eminence LAB 12 TS Parameters within your vicinity.At least you have an idea what parameters will give you 25 Hertz in a 180 litre box.

 

Best Regards,  
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Originally posted by Crashpc Crashpc wrote:

Same as user corell wrote: "In a given volumen and port size and with equalizing available, TSP do not matter in the lowest octave. Max SPL is simply determined by Sd * Xmax."
It is irrelevant. Even if mechanical boundaries dominate thermal ones:

You want maximum of displacement to cover your point of maximum excursion available to driver.
this leads to >>
Tuning frequency of the enclosure being dictated by driver Xmax.
than >>
Size of enclosure is dictated by the spl characteristics you want to achieve for processing or without.
So with processing what in this case matters is the reasonable size of the port and rear chamber volume. You can build oversized box on low qes driver and flat process it. But you can achive the same resault just using higher qes driver in the same size enclosure. What you cannot do is use low qes driver full potential of puting it in small enclosure because fart noise wont allow you.
I dont see why not use this bump as your advantage either. The guys from a PD2150 topic seem to enjoy it.


Edited by gen0me - 11 December 2018 at 8:09pm
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Simulate a medium Qes driver versus a 0.14 Qes driver and see how many dB you'll have to compensate for.
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Elliot: 
Yes, one 21DS115 cannot keep up with horde of other drivers. That is established math. But that approach is a joke, as it loses on all aspects. Volume - much larger. Price - much larger. Efficiency - much lower. Again, I struggle to see how anything of it is any better. I can only get "up to" two pieces of Eminence Lab12 for one 21DS115 for the price. It has more motor force than two, hell three or four of these, more cone area, more displacement volume than two/three of these. Labs are a joke compared to this driver. I did fast sims, and two labs are no match, three labs still not much better, four is not much of an upgrade, so yes, we need eight pieces for significant upgrade. That is $2400 worth of drivers, $1000 worth of enclosures, and 720l of box volume to mock one $580 driver in a single 180l box. All I can say is BRAVO. I'm going to jump on this solution in a heartbeat. :-D
If you compared those speakers with the same tuning (because we are after SPL first), you would find that two labs are not going deeper than one 21DS115 in the same box. But the DS will have upper hand in top range and in cone excursion and displacement volume. That is not very happy outcome.

Gen0me: I don't follow this.
The speaker displacement always covers cone excursion. That's what happens when the cone moves, and it doesn't have just single  static consequence to anything. Tuning frequency is not dictated by the speaker Xmax. Not at all. Only if you throw many other requirements and restrictions at it, which we don't do here. Size of the enclosure partially is dictated by the SPL one wants to achieve,  but not completely. One driver can achieve the SPL with 100l, and another driver will achieve it with 150l. And another driver will not achieve it at all.

I can build oversized box for low Q driver, push it, and get the same response with high Q driver. Sure. But I can throw the low Q driver in a small box, which I ask for, but high Q driver will not match it in this small box no matter how much EQ you throw at it. And the low Q driver will approach or match the high Q driver in the large box, while working in the smaller box. 
Fart noise is function of many things. You can do that to any driver/box combo. And obviously, as I'm looking for compact solution, this would be the case for any used driver.



Edited by Crashpc - 11 December 2018 at 8:26pm
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Originally posted by mobiele eenheid mobiele eenheid wrote:

Simulate a medium Qes driver versus a 0.14 Qes driver and see how many dB you'll have to compensate for.


Did it before. What should I do with the number then? Like, what is the purpose of that comparison? Keep in mind that decibels are not watts.... For many drivers, you compensate 3db, but the input power is the same, as the defficiency in the SPL was caused by damping and high impedance in that frequency.
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