Help with Vintage Woofer

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maLx

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Joined 2018
Maybe someone can help me.

Looking to build a set of Vintage Spekears out of a set of Heil AMTs and the 12" woofer out of JBL L100s (JBL 123A-1). The woofer is going to handle around 800 and down to about 200 or 100 (will be pairing this with an active Sub). I am considering mounting these open baffle, but I have no idea how to figure out what kind of performance I can get out of them.

I found this article where someone gave SPL curves on the driver in a 1.5cf sealed enclosure JBL L100 Century which looked promising. In the L100s they were used as the low-range driver, in my application, I will be using them as the midrange driver from 100 or 200 and up.

Can someone give me any help as to how to figure out how these will perform open baffle and how big the baffle needs to be and how far from the wall? Otherwise, I can go with the sealed enclosure.

Thanks!
Joey
 
M

maLx

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Joined 2018
H

hweb

Member
Joined 2011
The 123 will probably be OK on almost any size baffle for 200-800Hz. Just be prepared to EQ. This will be necessary for just about any open baffle project. If you make the baffle very narrow (almost the same size as the 123) you'll have the least lumpy response, but need lots of EQ throughout your passband (200-800Hz in this case). With a wider baffle you should place the driver in a non-symmetric manner (offsets left/right and up/down). Response will be lumpier, but more output in the passband. In every case. EQ will be your friend.


BTW - I used a 12" on a 3 way with a 24" wide baffle for ~80-350Hz and it worked very well. I could have gone somewhat narrower without giving up anything (just a touch more EQ).
 
M

maLx

Member
Joined 2018
GM said:
123A T/S specs here: http://www.jblproservice.com/pdf/thiele small parameters/theile parameters.pdf


In its simplest form, a 30" wide baffle is sufficient, but in various shapes can be narrower: OB Theory

GM
Click to expand...

GM Question for you. Did you get your 30" number from information similar to this? http://www.jdbsound.com/art/frequency wave length chart 2013.pdf

If I go to 100hz, there's a column that says Wavelength to Trap in Inches, 33"

If my hunch is correct, that means that I need to make sure that a 100hz wave has at least 33" between. Does that include the driver size?

And, if it does, if I drop the baffle width down to 24" I could possibly EQ the driver 160hz - 800hz and have a smaller baffle. And if that includes the driver size, and I can have 6-7" of space left and right side of the driver, also top and bottom, I'd be golden!

I'm still going to read the documents you linked, but just want to confirm.

Thanks,
Joey
 
M

maLx

Member
Joined 2018
hweb said:
The 123 will probably be OK on almost any size baffle for 200-800Hz. Just be prepared to EQ. This will be necessary for just about any open baffle project. If you make the baffle very narrow (almost the same size as the 123) you'll have the least lumpy response, but need lots of EQ throughout your passband (200-800Hz in this case). With a wider baffle you should place the driver in a non-symmetric manner (offsets left/right and up/down). Response will be lumpier, but more output in the passband. In every case. EQ will be your friend.


BTW - I used a 12" on a 3 way with a 24" wide baffle for ~80-350Hz and it worked very well. I could have gone somewhat narrower without giving up anything (just a touch more EQ).
Click to expand...

Thanks!

Note this is going to be a completely analog system, so I was thinking to get a good amp/DSP that I can EQ, and then once I find all of the sweet spots, build the circuitry for it manually.

Not sure how to EQ an analog signal, but I am going to figure it out! If you have suggestions surrounding that let me know. I'm thinking the baffle width to be 26" wide with the speaker offset about 2" on each one opposite if that makes sense.
 
P

puppet

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Joined 2011
Hi maLx,
I've got a couple big heils and used them in OB. Great driver and will go down to 800hz with at least a 3rd order xo. I used an older 15" woofer myself for the low mid with no baffle. I'd give that a shot first with your jbl 12". No baffle. Make a stand to hold the woofer and use one of the holes on the jbl's perimeter to attach the heil. A block of 1x, flat under the heil, is used to hold the heil to the woofer with one screw through the blocks edge. Bolt the heil to the block through the holes provided in the heils housing. Roll off the response of the woofer to your sub(s).



Nice thing about the jbls is you can box 'em if OB isn't your cup of tea and go for a nice retro stye CD speaker set. A win win either way.


Have fun.
 
M

maLx

Member
Joined 2018
puppet said:
Hi maLx,
I've got a couple big heils and used them in OB. Great driver and will go down to 800hz with at least a 3rd order xo. I used an older 15" woofer myself for the low mid with no baffle. I'd give that a shot first with your jbl 12". No baffle. Make a stand to hold the woofer and use one of the holes on the jbl's perimeter to attach the heil. A block of 1x, flat under the heil, is used to hold the heil to the woofer with one screw through the blocks edge. Bolt the heil to the block through the holes provided in the heils housing. Roll off the response of the woofer to your sub(s).



Nice thing about the jbls is you can box 'em if OB isn't your cup of tea and go for a nice retro stye CD speaker set. A win win either way.


Have fun.
Click to expand...

Thanks for your input! I guess I'll understand more about mounting the drivers when I see them physically, (they are in transit). What crossovers did you use? I really want this system to offer as much detail as possible and sound exceptional, so I'm not willing to cheap out on the cross over.

With this new info I'd like a good crossover that can do 800 and up for the Heil, and 800 - 160 for the woofer.

Other question I have is this.. did you have to add any series resistors to the Heils so they don't out SPL the mids (is this the correct thing to say?)
 
P

puppet

Member
Joined 2011
I used a couple digital active xo's for my set-up. Have no fear though, there are many people on this site that are passive wizards.



Basics though, you'll be looking to match driver directivity. That means that at xo frequency, the woofers "beam width" should closely match that of the tweeter ... in this case the heil. A 12" driver (piston diameter of about 10") will begin to throw a 90* pattern at around 1300hz. Around that frequency the heil has about a 120*+ polar so I'd start with a xo frequency in the 1100hz range give or take for personal taste.


Think of xo orders as degrees of slope steepness. The higher the order, the steeper the slope.
 
M

maLx

Member
Joined 2018
Puppet which digital active XO did you use? I actually asked in another thread what people recommended to buy digitally. I want to use passive xos, but I do want to buy a Digital Amp and DSP or XOs so I can play with the signal in pink noise to understand exactly what frequencies I need to remove peaks from.

My thread for that is here. What kind of Amp?
 
P

puppet

Member
Joined 2011
You can use whatever xo you'd like. Best way to learn IMO. To really dial in a xo for a couple drivers will require measurements. After all of that, a pleasing sound rules the day.



Personally, I find a LR4 rings at xo. I hear it and don't care for it. The heil may enhance this, don't know. My personal preference is for shallower slopes, if the drivers play nice together.
 
M

maLx

Member
Joined 2018
Hi, Everyone.

So in an effort to pair an active subwoofer with this two way system, I think I found the sub that will fit nicely with this. I'm wondering if you guys can check my math here.

My goal is for a nice smooth and flat response around 100db, this way I can just tune it down and tune the left and right channel up a bit, mess with the volume until the music is about 95db at 1m.

This is the sub I chose:
https://www.parts-express.com/pedocs/specs/295-206-dayton-audio-dcs385-4-specifications-46581.pdf

Here's me entering the parameters: https://www.screencast.com/t/LJJd5LGkRkNi

Here's the SPL curve I'm getting with 5 watts in a 2.5L enclosure: https://www.screencast.com/t/2LVAht8WyI

That enclosure has an external diameter of of 22 x 22 x 16 with about 1/2 ft^3 of bracing: https://www.screencast.com/t/WR5ENC4S0tPf

Let me know if my math all looks good here and if you guys think this sub is a good match?

Cheers,
Joey
 
GM

GM

Member
Joined 2003
maLx said:
GM Question for you. Did you get your 30" number from information similar to this? http://www.jdbsound.com/art/frequency wave length chart 2013.pdf
Click to expand...

No, from experience based on the driver's published specs, but there's the room to consider and how the baffle are placed in it plus the driver's effective upper mass corner [Fhm], which can have a huge impact on baffle width/area, so with the right driver in the right place, a driver suspended in free air could be all the 'baffle' required and why I pointed you to where you can learn all this [at least that's my impression, I haven't actually studied these particular docs] plus use a powerful simming program to 'fine tune' your app if you have an older MathCad program.

Yes, in today's world, digital EQ solves a lot of design shortcomings, but down low and especially with low Xmax vintage woofers like yours, even a little boost can drive them beyond its low distortion limits, so may need to XO higher than desired if the baffle is too small.

Fhm = 2*Fs/Qts'

Qts' = Qts + any added series resistance: mh-audio.nl - Home

GM
 
M

maLx

Member
Joined 2018
Thanks @GM. I'll do some more reading about that but since these are vintage woofers, I think a real test is going to be the best test. When they come, I plan to mount them in free air, and then make a few baffle sizes and test to see what kind of frequency results I get.
 
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