Vintage JBL for subwofer

[Fenalaar]

If you do not use any modeling software, you are shooting blind. A lot of the enclosure suggestions for car subs are not appropriate for home use.

Likewise, if you use a pro audio woofer, it will often run into headroom problems, and also may not give a lot of deep bass, while providing plenty of bass above 35-40Hz.

Get a modeling software. That will help you find a suitable driver much easier.

WinISD is free, and runs on a windows machines. If you have an iPhone or iPad, get Speakerbox lite.

The GTO1514D models very nicely. Here’s the result in a 90 liter sealed enclosure.

An externally hosted image should be here but it was not working when we last tested it.

Johan-Kr

 

[academia50]

The GTO1514D models very nicely. Here’s the result in a 90 liter sealed enclosure.


Johan-Kr

Thanks Fenalaar for the graphic !

But I think that for sealed box 250 watts rms is little power to work at its maximum performance.

Could you calculate it for ventilated including dimensions of the box (Total VA) and number of ports and dimensions of them ?

I thank you in advance, it will be very useful for me, two boxes of around 100 liters is what I need...

 

[academia50]

I have news.....
I could not buy JBL1514D, and I had an opportunity to 2 x Eminence Delta Pro 18 A that I could not refuse.
So I will need some advice to get the best out of them in the construction of one or two cabinets ...

I was enthusiastic about the construction box of the Eminence model :

https://www.eminence.com/pdf/Delta_Pro_18A_cab.pdf

Delta Pro-18A Two By 18 Subwoofer

, but I see that has an F3 of 48.75 hertz against F3 of 36.01 hertz of model :

https://www.eminence.com/pdf/Delta_Pro_18A_cab.pdf

Delta Pro-18A Large Subwoofer Cabinet

I have also seen Cube 18, but my question is whether monsters of that size would reach 20 Hhz - 3db of F3...

https://www.freespeakerplans.com/plans/14-plans/basscab/11-cubo-18

I understand that Cubo 18 has been built with Delta Pro 18 A successfully, but I can not find measurements on the low frequency response.

What do you think ? Suggestions ?

 

[Fenalaar]

The cubo18 is a horn construction, so it will not go very low. You can, however, put it in a corner and use the corner as a horn extension to get better low end response. This is the way a K-horn is normally used.

Johan-Kr

 

[freddi]

here's a quick sim for Delta Pro 18a based on a Russian site's scoop model for Cubo18 - there's probably a better TH hornresp model (?) Maybe Cubo will see your post

It also seems to do similar in a Karlson box about the bulk of the original 1951 Karlson cabinet. (~136l airspace)

a tapped pipe cabinet might be one way to make it closer to a subwoofer in function

look at this video
YouTube

and this thread Plan ! - D-20 (hz) Macro Sub ..tapped horn by moi. - Speakerplans.com Forums - Page 1

 

[freddi]

here's that simple tapped pipe. Delta Pro 18a has a fair amount of inductance. With tuning around 22Hz, power handling isn't very high in the 40Hz region

The aperture could be a round hole, rectangle- having it a bit larger would raise tuning a bit.

 

[freddi]

OOPS -Here's proper drawing for the sim above = "this" and about 240 liter internal volume - much more manageable . Nieleaves' thread was a bit messy

 

[academia50]

here's that simple tapped pipe. Delta Pro 18a has a fair amount of inductance. With tuning around 22Hz, power handling isn't very high in the 40Hz region

The aperture could be a round hole, rectangle- having it a bit larger would raise tuning a bit.

In a few days, I will bring the Eminence and I will have to make a decision ...... what to build?
Thanks Freddy for your contributions and graphics, they look very interesting, I did not know this model apparently based on the classic Karlson (I had one many years ago, with 12-inch RE driver and a PP valve amplifier with 6BQ5, it was a great sound) but it does not have the exponential opening that is supposed to make it auto-tuneable with different drivers. Here is a different design of the opening, is tuned according to the driver to be used? That I deduce from your sim.
A very attractive point is its easy construction, and its column shape that allows both vertical (standing) and horizontal (lying) use is another attractive point ....
To study more carefully!

 

[academia50]

OOPS -Here's proper drawing for the sim above = "this" and about 240 liter internal volume - much more manageable . Nieleaves' thread was a bit messy

Wow....2x 240 liters per box will be too much for my living room.

Remember that I must connect two 8 ohm drivers in parallel, so I am considering abandoning the idea of two separate cabinets and putting the two drivers together in a corner. The K-horn of fenallar looks good, two TH together and sharing the volume of the cabinet for the rear wave of the speaker. I think I should find out a little more about this option as well.
Of course I can not use them in stereo in the future, is that important? there are those who say yes and who say no ...

 

[academia50]

...............Of course I can not use them in stereo in the future, is that important? there are those who say yes and who say no ...

This was what i meant .........


Stereo Subwoofers: Why Every Man Needs Two

 

[Brian Steele]

I'll call this one the Big Bad Baby. A simple offset TL with a response that stretches from the low 20's to just above 80 Hz. Big box though - nothing comes for free, LOL.

Isobaric mounting of the drivers could reduce box size by half, and provide the additional benefit of reducing even order harmonic distortion.

 

[freddi]

FWIW Delta Proi18a makes a nice looking plot if the Lossy Le feature is not invoked. Of course a reflex would work but tapped pipe could be tall and not much footprint

Delta Pro 18a 2 pi ~100 watts

 

[academia50]

What do the two curves 1 Pi or 2 Pi mean?
Because those differences?
And what is an isobaric configuration, two speakers as a Däpolitto?

 

[freddi]

here's a couple of resources - one for boundary conditions, the other to explain "isobarik" speaker configuration which uses two speakers but only the cone area (and displacement) of one

True Audio Speaker Topics: Spatial Loading

Isobaric subwoofer box design - Advantages and disadvantages

you did pick up the Eminence Delta Pro 18a (?) - Brian can figure out a good cabinet for you.

 

[GM]

Wow....2x 240 liters per box will be too much for my living room.

Of course I can not use them in stereo in the future, is that important? there are those who say yes and who say no ...

FWIW, based on my understanding of how a T/S spec optimal TH is designed results in ~282 L net with > 120 dB/m above ~25 Hz, so either choose a driver that has a much lower Vas AND ideally with an even lower Qts or go 'clam shell' isobaric to 'shrink' it at the expense of lower peak power capability.

FWIW, historically, recordings were mono below ~150 Hz, but some years ago it was pointed out to me that some more recent recordings were in full stereo, though AFAIK if I have ever heard some I didn't notice it for whatever reason.

For sure, DVD/BD music, movie soundtracks are mono per the 120 Hz THX spec, so all things considered would personally run a <120 Hz sub system in mono regardless of the source.

GM

 

[academia50]

here's a couple of resources - one for boundary conditions, the other to explain "isobarik" speaker configuration which uses two speakers but only the cone area (and displacement) of one

True Audio Speaker Topics: Spatial Loading

Isobaric subwoofer box design - Advantages and disadvantages

you did pick up the Eminence Delta Pro 18a (?) - Brian can figure out a good cabinet for you.

I've read the links, thanks.
I think that although I reduce the size the efficiency decreases (if I understood correctly)

Today I removed the speakers of the trade, I proceeded to control them and they are ok, as it should be for being new, but better not to find surprises when I install them, there are still a few months left. .

wow, they are really big!

You can see the corner where I have thought and almost decided to place a single cabinet subwofer. From 40 hertz down I think the stereo bass does not make much sense, DTQWTII also take care of it. This subwofer is only to give that "body" and "volume" to the music by playing the lower octaves, as I have already mentioned. I do not need to feel explosions or earthquakes (effects of HT movies), but I would like to feel in the body the artillery of the 1812 Overture or the lower notes of Bach's Tocatta and Fuga.

I'm thinking almost exclusively about choosing some vertical design to locate in that corner. The construction of Eminence with two drivers attracts me, it is easy to build and could even make a prism to take better advantage of the corner.

But ..... if I could go down to 20 kz without so much slope, ~ -15 db falls in 20 hertz ... it seems too much to me, it's almost losing the first octave or I'll have to use EQ, something that for now is not foreseen and sincerely, I would prefer not to have to resort to DSP. I hope this step is the last in the search for my musical nirvana .... (never say never, haha)

Will it be possible to simulate something like that? If Brian or someone else of you who masters the use of simulation programs to perfection did it for me, I will thank you here for eternity!

 

[academia50]

The above is for GM, fenalaar and Brian too, thanks for all !

And for all those who are helping me overcome this dilemma!

 

[freddi]

guess you could just make a dual 18 corner reflex with 200+ liters per Delta Pro18a and tuning around 20Hz

here's a sim for one Delta Pro18a

 

[academia50]

Hi freddi


I like that ! Thank you !

~ -9 dB of slope from 40 hertz to 20 hertz is much better than the graphics I've seen before of Eminence !

I suppose that the slope (bold) plus abruptly by the inductance that the VC presents will not be audible in the practice.

I am learning about HornResp, to assimilate new concepts and thus understand many things about graphics, but I admit that it is not easy, there are many variables .....

Horn resp for beginners - Page 2 - Free Speaker Plans

The doubts that are presented to me are:

This sim that you have done is for the two speakers in a single cabinet as I wish?

Is it a cabinet with a horn ? (I think the HR program is for that kind of boxes ) or is it a BR cabinet?

If so, you should find a box with port dimensions, right ?

 

[academia50]

I've been reading Brian's page about subwofers.
I clarify many concepts. It is very detailed, and it is not necessary to be an acoustic engineer to understand the concepts, but I did not find recommendations on what software to use ..
I have begun to simulate using WIN ISD.
The Eminence Delta Pro 18 A driver was not in the database, so I have already incorporated it, although there are some values that I have not found, the software has worked well, although a red warning (!) Alerts me that it is incomplete , I hope this is not critical .....

My final goal is very simple, take Eminence modeling with 2 drivers and try to lower the tuning of it. I imagine that to achieve this I will have to increase the volume of the box and change the dimensions of the ports.

I want to tune in below the speaker's FS, which is 28 hertz.

I think 25 hertz will be fine.

What do you think, am I on the right path?