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Author Topic: JTR releases new 2x18 Subwoofers - info here  (Read 1676 times)

Steve Litscher

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JTR releases new 2x18 Subwoofers - info here
« Reply #10 on: August 19, 2018, 12:58:33 pm »

Answering a couple of questions from above:

- I like the direct radiating design over the OS. The OS is amazing with what it can achieve from a single 18Ē driver, and it sounds darned good. But the extra delay and some node cancelation challenges in certain environments and configs had me wanting to go direct radiating. Granted, direct radiating isnít a magic wand, but itís a little less fussy in specific situations.

- The amps have full DSP, including limiting. Jeff programs them and thoroughly tests them prior to shipping. SpeakerPower has pretty decent processing in their active units - weíve been using the C212Pro for about a year; they have the SpeakerPower amps with DSP as well - no complaints.

- Output at 27Hz; I rarely run anything below around 35-36Hz, but knowing Jeff, if he says 27Hz, I trust that the speaker has usable output at that frequency. If Jeff does anything, itís over deliver and under promise. :-) Iím not a gambling man, but my bet would be that 27Hz is +/- 3dB. Jeff would know for sure.


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Lance Hallmark

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Re: New JTR subwoofer - 2x18 HO
« Reply #11 on: August 20, 2018, 03:34:04 pm »

The following is a general statement, and is not inferring or referencing any of the products in discussion, It is for general information and consideration.

The useful output of any loudspeaker is a combination of extension and sensitivity and power handling.

A simple number ( goes 10Hz lower) doesn't tell anything about how loud it is at that freq.

The -3dB or -10dB etc MUST be referenced to SOMETHING or else it has NO meaning.  It should be referenced to the sensitivity to have any valid meaning.

But sadly, there are plenty of examples of top manufactures whos own graphs and simple number spec sheets are VERY wrong.  I have some that are more than 20dB off.  that is only a factor of 100.  What if your pay check was off by 2 zeros?  I bet you would care THEN.  HA HA

ANY loudspeaker EVER made, including soft dome tweeters, can EASILY reproduce 1Hz.  So every loudspeaker goes down to 1 Hz.

Now how LOUD they are at 1 Hz is a TOTALLY different story.

You MUST know more information than a simple number.

Simple numbers will get you trouble every time.

My bad, it is listed on the web site

Frequency +/- 3db
27-190hz (tuned to 27hz), active version
Sensitivity (half space)
103db, 1 watt, 1.41 volt, 2 ohm (half space)
Usable Output
138db (Calculated peak 141db Ė 3db compression)

I sometimes put an answer out quickly without attention to detail - too much time on about every other dumbed down social media site & forum. It is that attention to detail and how important those details are for true knowledge and understanding that I love about this forum, I apologize for lowering the bar sometimes which is why I am here mostly to learn.
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Lance Hallmark
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Chamsys, Crown, Danley, EV, JTR, Powersoft, Yamaha

John Schalk

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Re: New JTR subwoofer - 2x18 HO
« Reply #12 on: August 20, 2018, 04:56:47 pm »


Sensitivity (half space)
103db, 1 watt, 1.41 volt, 2 ohm (half space)

I am considering driving each speaker separately so how do I translate the single 2 ohm sensitivity spec into two 4 ohm loads?  I understand 2.83 for 8 ohms, 2.00 for 4 ohms, and now 1.41 for 2 ohms but I'm lost when it comes to going from a single load to dual loads.
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Art Welter

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Re: New JTR subwoofer - 2x18 HO
« Reply #13 on: August 20, 2018, 08:02:04 pm »

I am considering driving each speaker separately so how do I translate the single 2 ohm sensitivity spec into two 4 ohm loads?  I understand 2.83 for 8 ohms, 2.00 for 4 ohms, and now 1.41 for 2 ohms but I'm lost when it comes to going from a single load to dual loads.
Increasing from one to two "loads"  (driver/enclosure) increases sensitivity by 3dB.

Two drivers/enclosures each of 100 dB sensitivity would be equal to one dual driver/enclosure of 103 dB sensitivity. The one watt one meter sensitivity, (2.83V into 8 ohms, 2.00V at 4 ohms, 1.41V for 2 ohms) for the pair of drivers remains the same whether driven by one or two amplifiers.




« Last Edit: August 20, 2018, 08:07:51 pm by Art Welter »
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John Schalk

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Re: New JTR subwoofer - 2x18 HO
« Reply #14 on: August 20, 2018, 10:58:07 pm »

Increasing from one to two "loads"  (driver/enclosure) increases sensitivity by 3dB.

Two drivers/enclosures each of 100 dB sensitivity would be equal to one dual driver/enclosure of 103 dB sensitivity. The one watt one meter sensitivity, (2.83V into 8 ohms, 2.00V at 4 ohms, 1.41V for 2 ohms) for the pair of drivers remains the same whether driven by one or two amplifiers.

Thanks for trying to help me Art, but I'm still not sure I understand.  I would like to know what the calculated output of this sub will be if I power it with two amp channels that produce 1250 watts @ 4 ohms.  Can I simply add the two channels together (2500 watts) and then use the supplied 103 dB sensitivity spec and do the math?  If so, I come up with an output of ~137 dB which is pretty close to Jeff's usable output spec of 138 dB.  Did I do that correctly?
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Art Welter

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Re: JTR releases new 2x18 Subwoofers - info here
« Reply #15 on: August 20, 2018, 11:24:38 pm »

Yes, an output of ~137 dB would result at the frequencies that reach the 103 dB sensitivity specification with each 4 ohm driver powered with ~1250 watts, same as an amp capable of 5000 watts into two ohms for the pair.


« Last Edit: August 20, 2018, 11:53:24 pm by Art Welter »
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