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OldBlindJim
09-08-2007, 10:45 AM
OK, thoughts on a PA project.

Most of my 35 years involved in Pro Sound I have been with mid sized systems. From 2500 seat theaters on down. For some time I have been looking to make my own compacted PA for myself. Years ago I saw and heard a flamingo group playing at a outdoor mall in SoCal with a EAW JFX260. Great tone , lots of volume and fairly small. I looked into EAW and found the JF80z (2 x 6.5-inch woofer) then the LS832 (8 woofers, 3 tweeters) and started me thinking.

Back before anything I owned a pair of 4680 columns. Great for brutal volume but weighted a TON. The one thing I noticed was the coupling of drivers to the air. Tried the same thing a few times with (4) 2225a and 90x40 2441 and a pair of 2405 (LE's) (clears, many though they were lights) . It would fill the room and no phasing issue except for dead center, that's where the 90X40 crossed and couple up, but that was fine after a few beers.

Now I want to do the same concept again but smaller.
(got to fit into a Subaru Outback)

First product that came to mind was the 4680 until I remembered the weight and size plus how many have you seen lately?

Second was the 4612. There was a band that would show up with (4) 4612 and (4) dual D130 bass bins. Sounded real bad. No coupling, Phasing issues every where but enough volume for the room. Thinking back now, if the 4612s were stacked on their sides to form a column, things would have been better.

SO...with all the technology in power and front end gear I think it's time to fire up my project and give the 4612 another shot. They can produce plenty of volume and could be small and light. I just bought a pair of 4612 so they will be the project base.
Reconfigure the 4612 driver lay out.
Dual 8" column with the 2404 in between and ported in back, center.
Time alien the 2404 with the 8" if necessary.
Redesign the crossover if necessary.
Couple cabs together to form taller columns.
Add subs when necessary.
I know where a bunch of 2225a and h are and the guy owns me a favor!
3.5 cu ft or 5.0 cu ft for more puff.
I'm still not too nuts about the power plates so I'll pick up a Crown 300 II (Cheap to buy now and mixer has a sub send on board) I'll try and post as much as I can as I go along. I'll use LEAP to design with and LMS to test with and AutoCAD to draw with.

Tally Ho
OB Jim

OldBlindJim
09-17-2007, 07:37 AM
Volume is very much the same as the 4612 cabinet. Porting will stay the same and aligning drivers does not seem to be an issue. Grill will be perforated metal attached at cleat top and bottom and at side where a indention will be to allow grill to be flush with sides. This way reflections will not be a problem. 18mm ply through out. Speaker stand insert at bottom.

speakerdave
09-17-2007, 08:52 AM
If you are building this as an MTM, it's an idea I've considered and decided it would not work because of interference between the woofers. The spread between the woofer centers is too great for the crossover frequency required by that tweeter. Looking at the 4612 crossover I see that one of the woofers is a "helper woofer" with an inductor in front of it and the other is run full range. For an MTM using the 2118J I think it would be better to choose one of the PT waveguides of no more than 4" height and one of the modern small drivers (2417?) for a lower crossover frequency--about 1000 Hz. Z-man has experimented with that stuff and has posted some work using them.

David

OldBlindJim
09-17-2007, 09:52 AM
I also noticed that the 4612 and the 4612OK have slightly different high pass configurations. (Disregarding the l-pad) The OK looks to be newer with a bypass cap. You are correct that one of the 2118J is a helper.
What if the 2404 is move to the top of the cab (TMM) instead so that the helper would be nearest the 2404. The pattern would different but still not as bad as what it must be in the original cabinet.

OBJim

speakerdave
09-17-2007, 10:16 AM
I also noticed that the 4612 and the 4612OK have slightly different high pass configurations. (Disregarding the l-pad) The OK looks to be newer with a bypass cap. You are correct that one of the 2118J is a helper.
What if the 2404 is move to the top of the cab (TMM) instead so that the helper would be nearest the 2404. The pattern would different but still not as bad as what it must be in the original cabinet.

OBJim

I'm sorry if I've given the impression I can answer technical questions. I don't want this to become a case of the blind leading the blind. I was just sharing my reading-based thinking about a similar idea. I bought my 4612 components sans cabinet, so I have not heard the original. I had understood people to say it was a pretty smooth-sounding speaker.

With the tweeter at the top, I would think the full-range 2118 should be next, and then the helper below.

See RobH's MTM thread for more information about that layout.

http://www.audioheritage.org/vbulletin/showthread.php?t=17450&highlight=mtm


David

Zilch
09-17-2007, 12:15 PM
Minimum height PT-F "Compact" waveguides are 6.5" high. All dispersion patterns are the same, front dimensionally.

My 4612Bs measured kinda nasty bright, as I recall, when Hamilton and I were designing his MTM centers using 2342 horns a couple of years ago.

I forget how they sound. They're here, is all.... :dont-know

OldBlindJim
09-17-2007, 01:15 PM
I've just checked out some of the thread on some MTM projects.
The idea was to maintain the 4612 to avoid a cost run away.

Issues with 4612 as the project components are:
Distance from both 2118 will be too great for 3K support with 2404
4.52 inches centers = 3K
7.125 inches now with 2404 = 1.9K "Too Low"
Network configured for low, mid, high operation (helper 2118)
Will probably present a problem if used.
They are a bit bright! (I forgot too)I could start buying more JBL drivers and horns but now we're talking money.
So instead of beating myself up I'll put them back together and "Away They Go!"

Thanks for all the links and info. It saved me from a lot of time and effect.

OL Jim:D

OldBlindJim
10-08-2007, 08:09 AM
I can't seem to let it go!

The 2404 are cute but I've decided to swap them out for a 1".

(anyone looking for a set of 2404 and xovers?:))

The 1" I think would be a good choice would be the 2407H and the horn will be the Renkus Heinz CBH1600 metal horn. Only 9" wide and control down to at least 2K.

I could have both the 2118 in parallel with the same slop. I could also offset the horn to remove any possible phasing issue.

Anyone with crossover suggestions or idea?

Earl K
10-08-2007, 08:35 AM
I can't seem to let it go!

The 2404 are cute but I've decided to swap them out for a 1".

(anyone looking for a set of 2404 and xovers?)

- I agree that a mylar diaphragmed 1" driver is a much better way to go ( more natural sounding ) .
- The Klipsch corner horn crowd have a thing for these 2404 tweets , so selling them is rarely that big a deal .


The 1" I think would be a good choice would be the 2407H and the horn will be the Renkus Heinz CBH1600 metal horn. Only 9" wide and control down to at least 2K.

The 2407H / or BMS equivalent / or the B&C de10 ( or de25 ) are all good performers . Your choice can be based on the desired crossover point vs power handling, mounting style, availablilty & price .
- Horns ?? There are lots of nice small horns. 18 Sound make an elliptical ( mini paragon horn ) that has caught my eye / though I haven't heard it yet. B&C has a nice inexpensive CD style project horn .
- My advice is to design in a removable baffle area using T-nuts , etc. ( for around the horn itself ). This allows for a changing out different horns ( based on different coverage requirements ).


I could have both the 2118 in parallel with the same slop. I could also offset the horn to remove any possible phasing issue.

- The 2118J does have the capacity to be great for voice reinforcement.
- I agree with earlier suggestions that when using twin 2118s / one needs to dedicate one as a helper woofer ( Low Bass only )


Anyone with crossover suggestions or idea?

- Evolve the original crossover to suit your needs ( for sound reinforcement usage, I'd go with 24 db slopes between both, the 8" that runs up to the comp. driver and the hipass on the comp. driver ) . You'll likely need to include some form of HF, EQ filter on the horn driver to flatten the natural falling response .

- Another approach, offer Zilch some money ( or some gear traded in kind ) to help you design something usable for your DIY project ( or be willing to spend a couple of years here or at the DIY forum learning something about the craft of crossover design).

<> :)

ps; nice CAD work !

macaroonie
10-08-2007, 09:34 AM
The removeable baffle for the horn area is sound but personally I do have reservations about T Nuts. Complete pain if they dislodge before you get the bolt out. See if you can find these little guys once you get started. They work really well and if you are mad keen you can add in some cryo glue just for good measure.:)

OldBlindJim
10-08-2007, 10:10 AM
The removeable baffle for the horn area is sound but personally I do have reservations about T Nuts. Complete pain if they dislodge before you get the bolt out. See if you can find these little guys once you get started. They work really well and if you are mad keen you can add in some cryo glue just for good measure.:)When I had my wood shop I was buying them by the thousands. Pretty neat stuff.

OldBlindJim
10-08-2007, 11:02 AM
- I agree that a mylar diaphragmed 1" driver is a much better way to go ( more natural sounding ) .
- The Klipsch corner horn crowd have a thing for these 2404 tweets , so selling them is rarely that big a deal .Should be a breeze.

The 2407H / or BMS equivalent / or the B&C de10 ( or de25 ) are all good performers . Your choice can be based on the desired crossover point vs power handling, mounting style, availablilty & price .2407H first BMS second and B&C third
- Horns ?? There are lots of nice small horns. 18 Sound make an elliptical ( mini paragon horn ) that has caught my eye / though I haven't heard it yet. B&C has a nice inexpensive CD style project horn.TX1086 from 18 Sound (http://www.eighteensound.com/index.aspx)
The TX120 was just a bet small and lost control at 2.5K The TX1086 has control down to 1.4K. I could make the cab wider.

- My advice is to design in a removable baffle area using T-nuts , etc. ( for around the horn itself ). This allows for a changing out different horns ( based on different coverage requirements ). Noted

- The 2118J does have the capacity to be great for voice reinforcement.
- I agree with earlier suggestions that when using twin 2118s / one needs to dedicate one as a helper woofer ( Low Bass only )
- Evolve the original crossover to suit your needs ( for sound reinforcement usage, I'd go with 24 db slopes between both, the 8" that runs up to the comp. driver and the hipass on the comp. driver ) . You'll likely need to include some form of HF, EQ filter on the horn driver to flatten the natural falling response .The offset of the comp driver and the 2118 in the original xover presented an issue with phasing. With the added efficiency of the comp driver and a lower crossover point that I could run the 2118 in par with a lower xover point to smooth out the hump from the focus of the cone above 1K (3db slope). Plus mechanically the 2118 might take a dive at 2K with such a xover. The comp driver would have to come in around 2K at 24db. Crossovers became easier to tackle after I got LMS and LEAP. Before that it was a note pad and a HP hand calculator.



ps; nice CAD work!My first CAD was in the late 80's before then it was paper and pencil since 1970.

OldBlindJim
10-08-2007, 11:23 AM
Here's with the TX1086 horn. Looks like I won't have to make the cab wider.

Earl K
10-08-2007, 11:57 AM
The offset of the comp driver and the 2118 in the original xover presented an issue with phasing. With the added efficiency of the comp driver and a lower crossover point that I could run the 2118 in par with a lower xover point to smooth out the hump from the focus of the cone above 1K (3db slope). Plus mechanically the 2118 might take a dive at 2K with such a xover. The comp driver would have to come in around 2K at 24db. Crossovers became easier to tackle after I got LMS and LEAP. Before that it was a note pad and a HP hand calculator.

- I have a preference in making cabinets as tiny as possible / therefore ( if my project ) , I'd be trying to "get away with it", by using horns as small as possible. As such, I'd force myself to make a higher point work ( in the 2 to 3K region ) . Alas, by the same token, I'd be jettisoning the 2118J(s) for an 8 ohm ( 8" ) woofer with a less obtuse basket ( ie ; something with cut sides ). Both RCF and B&C make very reasonable candidates / with 1.5" & 2" voice coils , respectively. ( FWIW, I also prefer , one woofer to one horn driver for these "mini-upe" designs ) .

Having said all that ( & mostly excused myself from giving anymore advice ;) ) ;
- I wouldn't let an existing "bump" ( say in the area of 1K to 3K ) deter me from going with the higher crossover point. Bumps can easily be handled by LCR notch filters. I believe this site now has enough info in it about LCRs , to help you design your own.
- A series LCR ( paralleled across the driver ) can also be made to work ( ie; offer attenuation ) as long as the filters' Fo point is higher than the F3 point of the lowest pole ( element ) in the lowpass filter .
- I somewhat walked Zilch & RobH through the process of how these filters "work" ( or don't ) in that position, sometime ago. I don't remember if that particular exercise registered . Anyways, JBL uses series LCRs in this way in a few of their SR products / therefore one can see that it's a viable approach for addressing response anomolies that might exist around the preferred crossover point .

<> :)

Zilch
10-08-2007, 12:36 PM
For "Baby Cheeks," seems like 2342 would fit.... :yes:

OldBlindJim
10-08-2007, 12:58 PM
For "Baby Cheeks," seems like 2342 would fit.... :yes:Just barely.:) The big issue would be it stick out a bet far.

OldBlindJim
10-08-2007, 01:33 PM
- I have a preference in making cabinets as tiny as possible / therefore ( if my project ) , I'd be trying to "get away with it", by using horns as small as possible. As such, I'd force myself to make a higher point work ( in the 2 to 3K region ) . Alas, by the same token, I'd be jettisoning the 2118J(s) for an 8 ohm ( 8" ) woofer with a less obtuse basket ( ie ; something with cut sides ). Both RCF and B&C make very reasonable candidates / with 1.5" & 2" voice coils , respectively. ( FWIW, I also prefer , one woofer to one horn driver for these "mini-upe" designs ) .
Would be cute!

- I wouldn't let an existing "bump" ( say in the area of 1K to 3K ) deter me from going with the higher crossover point. Bumps can easily be handled by LCR notch filters. I believe this site now has enough info in it about LCRs , to help you design your own.
- A series LCR ( paralleled across the driver ) can also be made to work ( ie; offer attenuation ) as long as the filters' Fo point is higher than the F3 point of the lowest pole ( element ) in the lowpass filter . I have work LCRs before and they can make a big difference. 18 Sound (http://www.eighteensound.com/staticContent/applications/kits/18Sound_kit8.pdf) has some kit info and use a LCR in there kit lit. I could pop the circuit into LMS and sweep a 2407 or whatwever I end up with and adjust it until I can get them to flatten out.

subwoof
10-08-2007, 01:33 PM
Stay away from the thin-paper 2118 types as they will only crumple and fold with any real signal below 100hz. Same for the ring radiator familybelow 4K. The 2416/17/18 suffer from heat buildup failure unless the duty cycle is very low.

I built a handful of nearfield monitors that had to be wall mounted on the sides of a small stage in Kwest.

I ended up using the automotive GTI1000 10" 4ohm highpower LF and the 2426 on the 2373 ( MR ) horn. To make the cabinet real narrow, I cut about 1.25 off each side of the horn. They are biamped with a DSP at 1.2K

That box kicks butt and can be eq'ed up real close. Another advantage is that it serves as a backup to the house mains should they fail and that has been done a few times...!

If I remember the box is 12 wide, 10 deep and about 17 tall.

My portable system speakers are clones of the 4892-90 ARRAY series that use the 2217H ( ferrite mag ) that is inbetween the 2226 and 2206 in performance / size but it has a squared off frame that is only 12.75 wide!

JBL had a bunch on the tent sale at 145 each last spring but they went fast.

sub

OldBlindJim
10-08-2007, 01:50 PM
Stay away from the thin-paper 2118 types as they will only crumple and fold with any real signal below 100hz. Same for the ring radiator familybelow 4K. The 2416/17/18 suffer from heat buildup failure unless the duty cycle is very low. The 2118 will be in good hands. I have 120hz filters on the mixer channels and I could add subs if need be. I was also thinking about the heat issue and going to a 2426 style driver would be much safer.

OldBlindJim
10-08-2007, 02:52 PM
Might be returning to the MTM setup.
Use 2426 type drivers.

subwoof
10-08-2007, 05:16 PM
Well depending on your budget, a pair of 2012H 10" cones will give you the output and handling ( 250ea ).

9.25" square frames means a thin box...and the frames are black ( required for cool ).

But then I suggest a pair of 2452's .

THAT would kill on vocals.

sub

Earl K
10-08-2007, 06:19 PM
Well depending on your budget, a pair of 2012H 10" cones will give you the output and handling ( 250ea ).

9.25" square frames means a thin box...and the frames are black ( required for cool ).

- I designed up a minitrap that uses 2012s' paired up with 2426H drivers on cutdown RCF 9041 cd horns. Subs are 18" Transparence ( Quebec ) somethings . These 10" minis are head & shoulders the favourite choice of my clients ( from the Corporate side of the business ) .

- An 8" based mini could be usefull / though a lot more limited in overall applications ( even when used in multiples ). I tend to build up inventory in multiples of 8 ( if I like a design ).
- After doing a few industrials with only EAW JF50S / one begins to realize just how small a box, one can get away with / when there are some subs to do the heavy lifting. ( JF50s are a ferro fluid soft-dome tweeter over twin 5 1/2" drivers )

- OBJ was looking for ( the last time I checked ) something to fit nicely into his Subaru ?? station wagon ( if I remember the car correctly ) to support semi-acoustic acts ( such as flamingco acts ).

- ( IMHO ) Dedicating 30" of height to a twin 8" anything is a waste of space . That's generally the standard height of an enclosure with a 15" & a horn ( in some sort of trapezoidal enclosure ). A fifteen or twelve based design will always walk all over anything achievable from two 8 inchers .

- I think I've said enough now / so I'm bowing out .

<> Earl :)

OldBlindJim
10-08-2007, 06:30 PM
Back to the drawing board.
I'll put the 4612 back together, put them on block and start the hunt for a pair of 12" 2 ways.

OBJ

Zilch
10-15-2007, 12:25 PM
-- I somewhat walked Zilch & RobH through the process of how these filters "work" ( or don't ) in that position, sometime ago. I don't remember if that particular exercise registered .I certainly got that they're a shunt, and require source impedance to function.... :thmbsup: