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Vintage JBL for subwofer
Vintage JBL for subwofer
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Old 18th February 2017, 09:49 PM   #1
academia50 is offline academia50  Argentina
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Default Vintage JBL for subwofer

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.
Attached Images
File Type: jpg JBL LE14C Especificaciones.jpg (190.2 KB, 794 views)
File Type: jpg LE14H-3 #1 brek in 10 hs noise pink.jpg (69.5 KB, 778 views)
File Type: png 01_esp_circuito_filtro_pasivo.png (4.7 KB, 767 views)
File Type: jpg Blanco inmaculado .JPG (542.5 KB, 765 views)
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Old 18th February 2017, 10:01 PM   #2
cbdb is offline cbdb  Canada
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probably not enough power
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Old 19th February 2017, 01:14 PM   #3
academia50 is offline academia50  Argentina
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Quote:
Originally Posted by cbdb View Post
probably not enough power
Is more than enough, has been my system for many years
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Old 19th February 2017, 01:28 PM   #4
academia50 is offline academia50  Argentina
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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 ?
Attached Images
File Type: jpg 07_esp_foto_filtro_pasa_bajos.jpg (76.0 KB, 729 views)
File Type: png 01_esp_circuito_filtro.png (3.4 KB, 133 views)
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Old 19th February 2017, 01:35 PM   #5
academia50 is offline academia50  Argentina
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Another one that seems more elaborate



Filtro pasa-bajos para Sub-Woofer activo
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File Type: gif Pablin - circuito pasa bajos.gif (6.8 KB, 145 views)
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Old 22nd February 2017, 03:10 PM   #6
jjccoutcher is offline jjccoutcher  United States
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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.
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Old 22nd February 2017, 07:43 PM   #7
academia50 is offline academia50  Argentina
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Quote:
Originally Posted by jjccoutcher View Post
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.
Attached Images
File Type: jpg Potencia RCA 035.jpg (57.6 KB, 146 views)
File Type: jpg 004.JPG (539.9 KB, 165 views)
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Old 6th March 2017, 07:46 PM   #8
academia50 is offline academia50  Argentina
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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:

DTQWTII from Argentina

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
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Old 14th March 2017, 07:20 PM   #9
academia50 is offline academia50  Argentina
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No comment ? Come on, men of little faith ......
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Old 14th March 2017, 10:51 PM   #10
bear is offline bear
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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.

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