RD vs Sundown?

[Electrodynamic 10+ year member]

Nick im confused on your statement.

Cone area of 2 12's is 226 sq inches. Cone are for a single 15 is 176 sq inches. Difference of 50.

Xmax is 16mm on the Alpha v2 however there is two 12's. Nightshade you said had 23mm and one 15".

"stock" Alpha will handle 1500rms

"stock "nightshade will handle 1500rms

Just my .02 cents

Cone area is larger on the Alpha's, but the NS still out-displaces the pair of 12's. But as Jacob pointed out, it's going to be tough to get either driver(s) to full Xmax.

 

[Electrodynamic 10+ year member]

So, if you are going by the amount of one way linear movement while maintaining 70% of the BL obtained with 1 watt of power as X-max, I guess according to you the RD Alpha is unable to move out of the gap and maintain a minimum of 70% Bl loss?

I never said the Alpha was unable to move out of the gap and maintain a minimum 70% BL loss. If RD is rating their Xmax by typical overhang, that is their rating. I was unable to find any data that would say otherwise. I haven't seen any FEA or Klippel data that would support the notion of the drivers having more linear excursion than what they are claiming. I was going off of data supplied by both manufacturers, nothing more.

If you add X-max to the Alpha's in your equation, then it might be possible for two 12" Alphas to have as much or maybe even more displacement as one 15" Nightshade? I really don't care for either driver, I just didn't see how your math was accurate in your displacement values. My opinion is go with the company that can and will help you in the future with their product or make sure you can find another company that can fix it before you buy it.

If you added Xmax without verification to either driver, then you would be correct that the displacement values would change. But if you're doing that, why not pad other data as well? Calculating linear displacement is pretty easy: convert all measurements to one common value (in this case, I converted to cm) and take cone area and multiply that times linear stroke.

For the Alpha, 490 cm^2 is a typical Sd for a 12" driver that does not have a wide surround. Xmax is rated at 16mm according to RD's web page. Xmax is in mm, and in order to convert it to cm, 1 millimeter = 0.1 centimeters, which makes linear excursion 1.6 cm. Multiply the surface area of 490 cm^2 times the linear stroke of 1.6 cm and you get 784 cm^3 of linear displacement for a single driver, or 1568 cm^3 for a pair.

 

[basebalz13 10+ year member]

Didnt the OP ask about SPL in the comparison between 2 12's and 1 15?

 

[Electrodynamic 10+ year member]

Didnt the OP ask about SPL in the comparison between 2 12's and 1 15?

You know you're right. Higher linear displacement doesn't always mean it's going to be louder...especially in the SPL lanes and especially in ported enclosures.

 

[t1990le 10+ year member]

My question still stands, would i see a good enough increase in db to be worth trading subs and making a new box.

 

[audioinformer 10+ year member]

Technically the two RD Alpha 12's don't out-displace the single Nightshade 15. See this quick comparison below:
Two RD Audio Alpha 12 D1’s (assuming he has two D1's since his final impedance is 1 Ohm):

Per Alpha 12;

Sd: 490 cm^2 (giving it credit because RD doesn’t list Sd)

BL^2/Re: 263 (assuming that RD's Re is correct with 1.3 Ohm with the coils wired in series)

Xmax: 16mm

Displacement for one Alpha 12: 784 cm^3 for one, so 1568 cm^3 for two.

One Sundown Audio Nightshade 15 D1:

Sd: 810 cm^2

BL^2/Re: 173

Xmax: 23 mm

Displacement for one NS15: 1863 cm^3

If you take the RD Alpha and the Sundown Nightshade v.1 as is with the coil over hang as X-max at 100% of the Bl value taken with 1 watt 1 meter T/S parameters, then two Alpha's have more displacement. If you continue on the 70% Bl as true X-max (as it really can't be because this value can change as conditions change while playing the subwoofer and moving the coil out of the gap) then the Alpha's still should have an advantage. The Nightshade has a 25mm top plate, and your claim is that the voice coil can move 8mm out of the gap and maintain 70% Bl and the Alpha has a 21mm top plate which, everything being equal, it should be able to move minimum 4mm past the gap and still maintain 70% Bl or better. So, the Nightshade has an X-max of 23mm and the Alpha's have an X-max of 20mm.

Coil Overhang

Two Alpha's 980cm x 1.6cm = 1568cm^3

Nightshade 810cm x 1.5cm = 1215cm^3

OR

70% of Bl for X-max for the Nightshade (8mm) and half for the Alpha (4mm)

Two Alpha's 980cm x 2.0cm = 1960cm^3 (4mm past the gap)

Nightshade 810cm x 2.3cm = 1863cm^3 (8mm past the gap)

OR

Half of the Top Plate plus coil overhang

Two Alpha's 980cm x 2.65cm = 2597cm^3

Nightshade 810cm x 2.75cm = 2227.5cm^3

These two driver are to close for the Nightshade to over come the cone area with cone movement. But, if I were asked which I would chose, I would go with which every company would help me more in the future. I will not state my opinion here but, I just can't see where your math adds up is all......

 

[Electrodynamic 10+ year member]

If you continue on the 70% Bl as true X-max (as it really can't be because this value can change as conditions change while playing the subwoofer and moving the coil out of the gap) then the Alpha's still should have an advantage.

Xmax is the one thing that does not change while playing the speaker. Other parameters shift and change as BL changes/drops the further the coil moves away from the center/rest position, but the point at which the driver loses BL to 70% does not change. Whether the enclosure is sealed, ported, or how much power is applied does not change Xmax.

And yes, I will continue on that 70% of BL is Xmax as Klippel and DUMAX both agree. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[audioinformer 10+ year member]

Xmax is the one thing that does not change while playing the speaker. Other parameters shift and change as BL changes/drops the further the coil moves away from the center/rest position, but the point at which the driver loses BL to 70% does not change. Whether the enclosure is sealed, ported, or how much power is applied does not change Xmax.
And yes, I will continue on that 70% of BL is Xmax as Klippel and DUMAX both agree. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Well, I understand what Kippel is saying in his test but, I don't fully agree. Here is why I say that, I have taken a subwoofer and tested the T/S parameters in an infinite baffle firing horizontal with an LMS with 1 watt of power with the mic 1 meter from the subwoofer. This was in an enclosed room with climate control, no noise and no air moving and got a Bl of 24.94086 Tm (the Vas was configured with a sealed enclosure for the Bl). Taking everything the same and firing the sub upward the Bl droped to 17.8562 Tm (the Vas was configured with a sealed enclosure for the Bl). The Bl dropped just short of 30% of the total value the subwoofer had firing a different direction.

So Bl does not adjust is what you say but, just changing the direction the sub is firing during the T/S parameter test changes the Bl 30%. This by itself would mean the the sub was at full X-max firing up since it was 70% of the Bl it had as firing sideways both in a infinite baffle for the small parameters and a sealed enclosure for the Vas reading.

My only point was you could not compare the RD Alpha with its X-coil parameter to the Sundown Nightshade with its X-max parameter for total displacement of the drivers to say that one 15" sundown nightshade is louder than a pair of 12" rd alphas.

For the record, I really don't like either driver that much and think he could do better with something else but, that was not the question and I was only trying to help make your statement accurate. My opinion is if these are his choices, since they should be pretty close, I would go with which every sub company could and will help you more in the future. Customer service is more important than the sub itself because you should be able to build an enclosure that will take most of the advantage away or for a different setup.

 

[sundownz Pro Seller]

Just curious what don't you like about either sub ? Input appreciated //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Electrodynamic 10+ year member]

Well, I understand what Kippel is saying in his test but, I don't fully agree. Here is why I say that, I have taken a subwoofer and tested the T/S parameters in an infinite baffle firing horizontal with an LMS with 1 watt of power with the mic 1 meter from the subwoofer. This was in an enclosed room with climate control, no noise and no air moving and got a Bl of 24.94086 Tm (the Vas was configured with a sealed enclosure for the Bl). Taking everything the same and firing the sub upward the Bl droped to 17.8562 Tm (the Vas was configured with a sealed enclosure for the Bl). The Bl dropped just short of 30% of the total value the subwoofer had firing a different direction.

It looks like your measurements were taken with a few errors then. BL should never shift that much simply from the orientation of the loudspeaker, especially with a suspension as stiff as an LMS is equipped with. Do you honestly believe that the voice coil position or motor topology changed that much from firing the driver in a different direction? Also, what measurement system were you using? It takes far less than 1 watt, and no mic, to obtain standard T/S parameters.

Take a look at any Klippel report and you'll see the complete list of T/S parameters at different power levels. Xmax is the one variable that does not change.

 

[audioinformer 10+ year member]

The sub was a pro audio subwoofer and I was using the LMS program to perform the T/S parameters. Bl is the energy in the magnetic gap times the length of wire in the gap. As you heat up a coil of wire the inductance rises and creates an electrical loss. As a voice coil moves in the magnetic gap of a driver and the center of the voice coil moves from the center of the gap, you are having a loss of the Bl in the gap due to less wire that is effected by the gap. If part of the coil completely leaves the gap, your loss is increased greatly. If the coil of wire is effected by heat and it has an electrical loss, how does this not effect the X-max of a subwoofer? The Bl is being greatly effected by the electrical loss and X-max is the range of a driver with 70% loss of Bl but, X-max is the one variable that does not change? Since there is a possible Bl loss due to heat, then X-max can change and the length of a coil overhung from the top plate will not, voice coil length minus top plate height divided by two is a better and more permanent parameter for X-max since it can not change (unless the spider is sagging so bad that it is moving the voice coil too far out of the gap to be effective).

Honestly I have spent too much time on this topic, I have to get back to work and get a project shipped out of China this week since Chinese New Years starts the 10th. and you are right if you like. X-max is what you want it to be and a single 15" nightshade has more displacement than a pair of 12" alphas because the nightshade has 23mm X-max (figured with maximum cone movement with 70% of total Bl) and the alphas X-max is 16mm (figured with coil length minus the top plate height divided by two for X-max) so what ever.... blah blah blah,./.,./., Ohh, and the nightshade is 102dB SPL (2.83 volts) and the alphas are 89dB (1 watt 1 meter) so the nightshade wins again,./.,./.,

Ohh and Jacob I have nothing against you or your products. The sub that I re-coned seem to have bad glue joints or bad glue as that was the issue and the spiders, coil, cone, and the motor were all pretty close to IA DP but, I could be wrong. At the time i did not have the two subs side by side and i was going off of memory and I have been wrong many times beofre going off of memory so, maybe not. This was a while ago and there is nothing wrong with that and this was the only experience I have ever had with any of your subs. I have also heard that there is no issue with the glue or the joints at the present time. I know where your amps come from and they are a very good quality company. I know Mr. Park and Mr. Frank very well and I have been to their factor as well as meeting with them at CES many times and at the Hong Kong Electronics show once. (If you want to go to a great Korean restaurant in Vegas, go with Mr Frank to Seoul BBQ off of Sahara Ave., that is if you like Korean food.) I don't know either of you that well (Jacob or Electrodynamic) but I do know a lot of other people in the industry and I have been around a day or two my self.

 

[slam 5,000+ posts]

my head hurts from reading this thread

 

[Johnny Law.Lulz 5,000+ posts]

So, if you are going by the amount of one way linear movement while maintaining 70% of the BL obtained with 1 watt of power as X-max, I guess according to you the RD Alpha is unable to move out of the gap and maintain a minimum of 70% Bl loss? If you add X-max to the Alpha's in your equation, then it might be possible for two 12" Alphas to have as much or maybe even more displacement as one 15" Nightshade? I really don't care for either driver, I just didn't see how your math was accurate in your displacement values. My opinion is go with the company that can and will help you in the future with their product or make sure you can find another company that can fix it before you buy it.

Just curious what don't you like about either sub ? Input appreciated //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Id like to hear this as well.

To the OP, I would go with the NS simply because i am a fan of single sub set-ups and i know that Sundown subs are some of the best in the industry. I wish i could have the pleasure in using a Nightshade but i have 3" of spacers on the front of my box now to fit my Warden which is 8.25" deep. ( Jacob, make a slim NS lulz ). As a former Sundown sub runner, i love the performance and ability of all of their drivers. Now granted, i have not ran RD audio subs, i have an RD 3250 V.1 and it is an excellent amp. I belive anyone who has real experience with their equipment can say that it is top of the line as well but over shaded by the scandals of the owner.

I believe the NS will put 3K to use better. We all know "stock" ratings on a NS are 1500 RMS and we all know that with clean power in a proper box, they can easily handle double that, and if not, jacob can do a 3K version. Comparison wise, i think the TL gains or drops would be minimal because of the fact that your going from 2 12"s on 3K at rated to 1 15" on 3K at double rated. JAcob has done 150+ with a single nightshade on that same power i believe.

 

[T3mpest 10+ year member]

Thought I would chime in. Anyway xmax does NOT change as xmax is a large signal parameter that is based upon the changing of other parameters. The point that audioinformer is missing is that BL is defined as a drop of below below 70.7% of it's RESTING VALUE. Whatever amount of BL product you have with the coil essentially resting in the gap is defined as 100%. As you begin to lose BL as the coil moves, once you've lost more than 29.3% of it, you've reached xmax. However far the coil could move from it's centered position and still maintain over 70.3% of it's magnetic strength will determine your xmax. Xmax cant' increase or decrease with drive levels as it's parameter that's based soley on the shifting of another parameter.

BL product as Klippel is using it isn't truly a measurement of motor force so much as motor force product... The key different being as you pointed out, current. Klippel worries about simply B*l in order to do this they test the driver at fs where current demands and therefore impedence shifts will be minimized. This truly doesnt' give you a competely accurate picture of what's going on, obviously, but impedence irregularties usually only account for 10% distortion at best. Coincidentally that's also where distortion is usually audible in the sub-bass region. However, BL irregulaties generally cuase 30% of the distion within a driver, so overall just doing B*L is probably the safest bet. If we were truly concerned with actual SPL potential and distortion we would need to know BLI and look at things three dimensionally, with current being the third. However this creates different levels of xmax at different frequencies and various box arrangments, so we would get useless value unless we knew exactly how it was derived. Anway the last interesting thing to note about the various T/S parameters is that given 2 drives with the exact same T/S, xmax values can be drastically different.

 

[sundownz Pro Seller]

Ohh and Jacob I have nothing against you or your products. The sub that I re-coned seem to have bad glue joints or bad glue as that was the issue and the spiders, coil, cone, and the motor were all pretty close to IA DP but, I could be wrong. At the time i did not have the two subs side by side and i was going off of memory and I have been wrong many times beofre going off of memory so, maybe not. This was a while ago and there is nothing wrong with that and this was the only experience I have ever had with any of your subs. I have also heard that there is no issue with the glue or the joints at the present time.

Comparison of NS motor to DP motor :

FYI... NS does not = DP - Car Audio Classifieds

There have been lots of changes to the NS v.1 along the way as well. The newest ones had the spiders bolted down with steel rings, aluminum pole plugs, etc. Glue joint strength has improved quite a bit as well as I figured out better ways to do it.

In any event... the newest version of the NS motor is totally different all together -- should be available in a few months :

Nightshade v.2 Teaser Picture - Car Audio Classifieds

Same goes for the Z v.2 which is now available -- quite a bit updated from my older stuff :

Z v.2 15" Production Unit - Car Audio Classifieds

---

The NS v.2 is a good example of why I really am not a big fan of the Overhang x-max standard. It has a 71mm long coil and a 40mm tall top plate so you get 15.5mm by overhang -- 70% BL you get 27mm. Which do you think is more accurate for a driver with a huge magnetic gap and extremely long coil ?

Same could be said for the Z v.2 with a 50mm long coil and a 32mm tall top plate -- 9mm isn't a realistic x-max figure for a driver like that. FEA predicts 20.5mm by 70% BL method.

Overhang IS pretty close on LCSG designs, though -- something like a JL 13W7 with a 75mm long coil / ~12-15mm top plate comes out much closer to FEA / Klippel / DUMAX excursion with overhang. LCLG designs tend to be way off, though. Then you have XBL^2 designs (which is what Nick - Electrodynamic - deals with now) where a physical measurement is all but useless.

It can be said, though, that no system is perfect because so much changes dynamically in a loudspeaker... but to me the Klippel / DUMAX standard come closer to a "universal" system than the overhang standard which cannot even be used to describe some motor topologies.

At least we can say we talked about something other than, "Which is louder ?!?! BTL or HDC3 ?!?!" *laughs*

 

[audioinformer 10+ year member]

The only point I had was Nick was using 70% method for X-max and comparing it to coil overhang for X-max of a different sub and proclaiming that one driver had more displacement over another due to the difference in X-max. Same as comparing RMS power to peak or SPL at 1 watt 1 meter to another that used 2.83 volts. That is all....

 

[Electrodynamic 10+ year member]

You are correct - I did use the Xmax rating from both manufactures. Saying that the comparison was erroneous due to the latter would have merit if I would have taken peak excursion for one driver and xmax for another driver. Maybe RD Audio should post a more accurate Xmax specification on their drivers then. And as Jake pointed out, besides LC/SG topologies, coil overhang isn't a very solid method for calculating Xmax.

 

[Johnny Law.Lulz 5,000+ posts]

lulz, you guys with all your technical bickering. A pissing match over ratings wont help this topic.

 

[sundownz Pro Seller]

We like pissing - it is America's past time. Like baseball... but less boring.