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Vintage JBL for subwofer
Vintage JBL for subwofer
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Old 8th July 2018, 11:26 PM   #141
phivates is offline phivates  United States
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500 volt - that should handle whatever comes its way.
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Old 8th July 2018, 11:28 PM   #142
freddi is offline freddi  United States
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Vintage JBL for subwofer
here's your 137 liter box sealed with capacitor and vented with typical active EQ which peaks around tuning and rolls off below cutoff, both in 0.5 pi

when using the filter wizard of hornresp, I first set the highpass filter at 20Hz/2nd order then applied the peaking to get the composite response


Click the image to open in full size.
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Old 10th July 2018, 04:43 PM   #143
academia50 is offline academia50  Argentina
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Very thanks freddi !

The conventional blue line looks very good (very similar to WinIsd, that's good for me, it gives me peace of mind) I do not like the red line with capacitor, because it levels the response from 50 to 100 hertz, and DtqwtII already has a lot of weight there . Troels designed a passive divider that gives a lot of weight to the second and third octaves. The Dayton plate amplifier that I will use for now has a subsonic filter at 20 hertz 12 / db per octave, which is fixed, not switchable ... So I look for a soft roll off between 40 and 20 hertz.

I think that people who are fond of HT systems will think that this project is a waste, two huge cabinets with 18 inch drivers and are limited below 20 hertz ?

Well, this is to listen to music, again. I'm not interested in a subwofer that moves the furniture in its place, nor for the windows to vibrate when there are earthquakes in the movies....

Tocatta and Fuga de Bach (original work conceived for pipe organs) has a musical note that is a "natural Do" of organ that corresponds to 25 hertz. I'll be fine there. I will miss notes of 16 hertz? (see post number 14) Well, I think you can not have everything in life, you live better accepting this ...
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Old 10th July 2018, 06:09 PM   #144
academia50 is offline academia50  Argentina
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" Every choice of a transducer / box is always a commitment ..."

Could not been more easy ?


Next step :
External dimensions of the box calculating the cushioning material ....

(just to be sure ...)



Speaker Box Volume Calculator / Designer Help
Attached Images
File Type: jpg Calculadora on line sealed or vented.jpg (124.7 KB, 66 views)
File Type: jpg calculator in line sealed box.jpg (92.1 KB, 66 views)
File Type: jpg Calculator in line vented box.jpg (92.3 KB, 64 views)
File Type: jpg F3 a 61 hertz.jpg (124.6 KB, 65 views)

Last edited by academia50; 10th July 2018 at 06:19 PM.
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Old 10th July 2018, 06:33 PM   #145
academia50 is offline academia50  Argentina
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I'm sorry it came out repeated sealed, missing vented....
Attached Images
File Type: jpg Ported box calculator in line.jpg (104.8 KB, 12 views)
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Old 10th July 2018, 06:52 PM   #146
academia50 is offline academia50  Argentina
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I think this site can help many in its design, here a very complete and easy to understand tutorial....

Designing and Building a Speaker Box Example
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Old 11th July 2018, 10:55 PM   #147
academia50 is offline academia50  Argentina
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bjorno:

As I mentioned before, the graphics provided by you are excellent but I have to admit that they surpass me in knowledge.

In the attached graphic I see two of my simulations with WinIsd.
One is from a sealed cabinet and the other from a ventilated cabinet.

A red line with the square root symbol on it, which means? That sign replaces a cross, that is, not viable, crossed out ?

And the OK in green, to which of the two systems does it refer?

I think your answer will be for me the strawberry that is missing the dessert, please allow me to enjoy it properly....

Thank you !
Attached Images
File Type: jpg Sims Eminence-DeltaPro-18A by bjorno.JPG (867.7 KB, 17 views)
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Old 11th July 2018, 11:18 PM   #148
academia50 is offline academia50  Argentina
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I have a new concern for everyone:

The calculations for a cabinet are made trying to be as accurate as possible, because we want to achieve the best sound.
If we already have the exact volume of the cabinet, but then we add buffer material inside it, the virtual volume will increase, as freddi pointed out earlier.

But, there are no exact formulas here, how much will it increase? 10%? 15 % ? And this percentage will also vary depending on the type of material used.
The bracing and the volume occupied by the tuning tube will be easy to add to the overall volume, but not the influence of the absorbent material.
In short, is it worth taking risks using material in my particular case, with large drivers and boxes?

I leave a study here:


Data-Bass

What do you think ?

Last edited by academia50; 11th July 2018 at 11:20 PM.
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Old 18th July 2018, 03:09 PM   #149
academia50 is offline academia50  Argentina
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Hello

I've been reading a lot and the conclusions I've reached are:
I go for sealed by the undoubted advantage of better transients in the low frequencies of work that I look for.
It will not be necessary to place any type of absorbent material inside the cabinet, because in fact it does not have the least effect on the quality of the sound, again, in the first two octaves.
There would only be an increase in virtual volume and that is unnecessary if we do not have space problems in the room, as my case fortunately.
But if the virtual volume changed the magic number Qtc = 0.707. Has no sense....

New readings that I have made with respect to the group delay seem to show that the high pass filter to protect the speaker at very low frequencies,
it can be counterproductive in the low frequency spectrum ...
(since it is permanently incorporated - it can not be switched ON OFF - on the Dayton SPA250 plate amplifier ...)

I think these high pass filters are important if we use ventilated cabinets, due to the "hanging effect" of these systems below the frequency of tuning (Fb), but this does not happen in the sealed ones, so it would be unnecessary and also counterproductive. .
But I must investigate more deeply about this...

Ps: The final choice is the boxes will be sealed.
It remains to define if there will be two, with a speaker in each one, or if it will be one with two speakers, which interests me again by saving material and work, only the excessive weight of the creature scares me ....
Attached Images
File Type: jpg sealedenclosure.jpg (33.6 KB, 8 views)
File Type: jpg Ported vs. Vented.jpg (117.4 KB, 3 views)
File Type: jpg Delta Pro 18 A Calc. line.jpg (152.5 KB, 3 views)
File Type: jpg Delta Pro 18 A Solution parameters.jpg (164.0 KB, 4 views)
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Old 18th July 2018, 03:39 PM   #150
bentoronto is offline bentoronto  Canada
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Vintage JBL for subwofer
Quote:
Originally Posted by academia50 View Post
But if the virtual volume changed the magic number Qtc = 0.707. Has no sense........It remains to define if there will be two, with a speaker in each one, or if it will be one with two speakers, which interests me again by saving material and work, only the excessive weight of the creature scares me ....
Sealed boxes have only a single parameter and the bigger the better. The ideal Q is no Q at all and the less ringing the better.

Simple so far. Too bad those three-decimal-places sims bear so little relationship to bass sound in your room. Now you are getting into the important challenging questions of room acoustics. Two boxes allow you to locate them so as to have the best possible final mixed-bass result.

Learn to use REW to tune your systems. Now the work begins.

B.
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HiFi aspirations since 1957. Currently working on motional feedback again... the final frontier in audio (also, see recent post with data on a 17-foot labyrinth sub)

Last edited by bentoronto; 18th July 2018 at 03:42 PM.
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