Vintage JBL for subwofer

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It is my intention to use this jbl speaker to add to my system as a subwofer. The idea is to cover the first two octaves, that is, bass response is cut at 80 cycles.

It's a vintage speaker, JBL LE14C, bass sector is identical to the LE14A, I think it has good potential for it.
Here you can see a link where your T / S parameters have been measured. Fs is 24 hz, not bad ...



I've been looking for calculators to build a first order filter, or maybe a second one? Will I need to add a zobel network to compensate impedance to it? .

Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)



Or it would be more effective and with the possibility of regulation if I built an pasive filter, to deliver the signal already filtered and with possibility of regulation before entering the amplifier ?.


Filtro pasa bajo pasivo para subwoofer



(It would be an independent and dedicated amplifier just for this task, the NAD 3020, 20 watts rms per channel, the speakers are 80 db at 4.6 meters - I calculate 95/96 DB at 1 watt 1 meter)
In short, many doubts and few certainties.
I will appreciate opinions on this.
 

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Here there is an improvement of the previous circuit, in this case it is an active low pass circuit. I think it will be less costly and less work to build this than making a huge coil of a value ranging from 15 to 20 mH

Filtro pasa bajo activo para subwoofer


What do you think ? Some experience ?
 

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Here's my 2 cents. When building a sub go with the most power you can afford (old Crown DC300a is a great amp for low end and is 610 watts in mono, you can find good buys on eBay)

An active crossover is the only way to go. A passive crossover for low frequency gets too big and sucks power away from your amp.

I have found if you go much bigger than needed the system can do normal listening levels without breaking a sweat.
 
Here's my 2 cents. When building a sub go with the most power you can afford (old Crown DC300a is a great amp for low end and is 610 watts in mono, you can find good buys on eBay)

An active crossover is the only way to go. A passive crossover for low frequency gets too big and sucks power away from your amp.

I have found if you go much bigger than needed the system can do normal listening levels without breaking a sweat.


Thanks for your appreciations.
100% are shared.
I will go for an active filter and if necessary I will use another amplifier of more power.
I have a classic RCA that I built years ago, is 75 watts per channel, would be raising almost 6 db compared 20 watts to the NAD ....
But I should not exaggerate because the vintage JBL LE14C speaker is at a lot of risk with the power you suggest.
It was not recommended to use it with more than 75 watts.

But in an 80-liter bass reflector cabinet, this speaker delivers basses that go deeper than the DTQWT I've built recently, I just want to boost the SPL in the first two octaves.

I found this filter that cuts in 73 HZ, has good answers from buyers.


Filtro Pasabajos Para Subwoofer - Preamplificado C/volumen - $ 349,00 en Mercado Libre




Thanks again.
 

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I was reading several threads in this subswofer section.
Is it only possible to achieve sub bass tones with large Xmax and tremendous powers?
Of course, class D helps, now it is fashionable to use these amplifiers in the subs when for years it was considered a bad circuit because of its excessive distortion .....
Well, never mind, I will follow my humble project , I'll tell you my news ..

As I mentioned in post 7, this is to complement this:

http://www.diyaudio.com/forums/multi-way/276238-dtqwtii-argentina.html

I'm thinking that instead of a classic cut of 6 db in a first order filter, it would be better 12 DB in the second order. The reason ? If there is too much bass overlap around the 80 Hz cut, I can invert the phase by 180 degrees (to compensate) by reversing the speaker connection)

Thanks for any comments
 
It's complicated.

You are limited by the maximum thermal limit of the old driver, that's more or less the power spec on the JBL spec sheet.

Then depending on the enclosure and "tuning" you choose, the next limit is the XMAX, also found in the JBL spec sheet. So you will have to use a simulator to compare excursion for the specific "tuning"/alignment vs. power vs. Xmax. You can't exceed Xmax as a limit (not by much anyhow). This will also tell you the max SPL out vs. freq.

Chances are you want a 4th order filter.

Consider just buying a premade "plate amp" intended for sub use, probably the cheapest easiest way.

_-_-
 
Is it only possible to achieve sub bass tones with large Xmax and tremendous powers?
In general the lower the frequency the more driver xmax and amp power is required to reproduce it. How much power you need is directly related to the listening SPL you usually run at and your subwoofer design. If your design can reach the SPLs you need with only 20-70w then there is no need for more.. simple as that.


I'm thinking that instead of a classic cut of 6 db in a first order filter, it would be better 12 DB in the second order. The reason ? If there is too much bass overlap around the 80 Hz cut, I can invert the phase by 180 degrees (to compensate) by reversing the speaker connection)
Here is my 2 cents on that. You will want at least a 3rd order filter at 80hz because anything shallower allows too much midrange into the subwoofer, and same goes for your satellite speakers, at least a 3rd order high pass filter there too to eliminate the low bass that will just push those drivers to xmax even if they cannot reproduce any meaningful output at those frequencies. Because of this it's often easier to use an active crossover before the amplifiers and if you go that route get one with 4th order LR filters for best summing response.
 
Bear, and Conanski, thanks for your responses.;)

I have been reading and I see that each of the different topologies of the basic circuits of active filters have their pros and cons, there are no free lunches here .....:D

I understand that you have to go through some more elaborate commercial design with the possibility of controlling and adjusting the different variables, roll off, phases, gain, etc.

Any recommendations on this?
 
Buy a plate amplifer with the built-in xover.

.......there's nothing down there unless ur running LP or some extraordinary CDs... maybe some video DVDs...


You have hit the nail ...... :) , this LP has very low frequencies .......


16 hertz are not audible but modulate to the lowest tones that we can hear ... also speak of using a subwofer to perceive in all its dimension the fantastic sound of these 6791 tubes.

Well, here I go then, DTQWTII exceeds in all audible parameters (they are excellent !) to these vintage JBL, less in the very low notes.

I think it's because the cabinet is a bass reflector. FS of the LE14C speaker and FB cabinet is much smaller than Eminence 2510 II.
 

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You have hit the nail ...... :) , this LP has very low frequencies .......
Be skeptical (esp for LPs) until you've actually seen those low notes on a real-time analyzer such as included in REW (free or honourware).

The real low freq music you want to reproduce is the side drum as in Mahler's and Copland's 3rd symphonies. That's where the low note is to be found.

Exaggerated power and low freq requirements routinely pontificated on this forum without empirical basis.

B.
 
When that filter is as much as $350, I'd use a MiniDSP 2x4 instead. It is much more flexible...

Johan-Kr


350 $ argentinos are 22 u $ s at this time. Not a great investment, but I will look for a better option, I have been convinced, it will not do much .......
I have this Yamaha 5.1 receiver, also the Prima Luna valvular amplifier that I use with DTQWTII, it has a bypass for HT ...... humm, and if I use the low level output of 5.1? This is for an active subwofer, I could use this option to go to the NAD 3020 / JBL, but I do not know how often the cut will be, nor the slope ....
I have to study this to see if it's possible

Any suggestions are appreciated! :)

RX-V520 - Stereo Receivers - Hi-Fi Components - Audio & Visual - Products - Yamaha United States


DiaLogue Two ? PrimaLuna USA
 
For home use, just get a Behringer iNuke amp with built-in crossover and EQ.

That is good news, Beringher is a very present brand here...

But they are products for PA, and something expensive for the investment I want to make at the moment ...


Behringer Inuke Nu-6000 Dsp Potencia Digital 6000w Usb - $ 17.990,00 en Mercado Libre



Friends, another question, class D (I do not know anything about the topology of these circuits :( ) admits to raising the loads in the output stage? I can use the JBL 8 Ohms as in a amplifier SS class AB without problems (losing power, which would be good for me ..... :D ) ?

Thanks in advance ! ;)
 
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