What is the best way to wire them Up?

[Mr Wizard]

Top Speaker,
JBL 4612OK

Bottom Speaker,
EV Sentry 500

My thinking was to use just the Sentry 500 12" inch woofer as low end fill and not use it's tweeter.
The Sentry 500 can be used in step down mode by plugging one port, which lowers cabinet from 40Hz to 28Hz.
The SEQ equalizer has a 6db boost at 32Hz to restore system flat.
The thing is, it is hard to find the SEQ box.
The Sentry 500 is bi-amp-able.
Any suggestion?

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[grumpy]

Do you have a second amp and electronic crossover?
Do you not like the Sentrys as they are?
Buy a powered subwoofer?
...

[Wagner]

I own a pair of those, the Sentry 500, recently posted a thread here looking for the correct surrounds for my woofers
A very very good speaker
They go PLENTY deep!

I couldn't locate a SEQ step down kit for mine for sale, even when I bought them back in 1991 or thereabouts (EV was unable to supply) I called them for the kit and a wall mount set
That said (and according to the EV service person on the phone as well) you won't miss it much without it
The person at EV also said that they sold very few of them to their end users as they weren't necessary (as in very little demand/few requests)

That box and woofer is very capable of some very good quality bass that you can not only hear but feel, "as is" (again, I know this from actually owning a pair)
I have never felt the need for more
It is more to help with the room and system integration than to help with the limitations of the system

In other words, the Sentry 500 was designed to work well without it (unlike more than a few of their consumer "Interface" models which requires it in order to produce it's rated response period/integral part of the systems's tuning); the "step down" kit is only required to augment things when needed in a poor environment/installation for bass response and to properly integrate the new response (boost) with the top end

I don't think you'll miss it and if you had it, probably wouldn't notice it that much (I have heard it installed at the shop where I bought mine) They just didn't have one for sale
At the time, the cost wasn't justified, even if they had
(although I do sort of wish I had sprung for it back then when it was still available, if I could have sourced one, just to have it now from a completest perspective)

The fact that you can't find one should tell you something; most users didn't install it or feel any need for it

I realize my comments don't "prove" anything and if you want it, you want it. I'm just trying to convey that you're not missing THAT much as far as performance (theoretical performance) so I wouldn't fret over it too much.

I have looked for a circuit diagram for the EQ box but have been unsuccessful; EV material is hard to come by. There are always some of those SEQ boxes up for sale for other EV systems and I am certain that they could be easily modified with a few parts value changes to work with the Sentry(s), the only challenge then would be to find a good fitting port plug (makes me think of Zilch, God Bless him) and the damn circuit diagram

I sold mine around 2002 and regretted it immediately. In January of this year I tracked them down and bought them back. Some sort of very weird swelling had occurred in a few spots on one of the cabinets (NOT water damage) and they were all dinked up. Don't know how the idiot managed all that. I bought them back anyway, found some edges that were close enough (they needed foam and are a hard one to fit) and am glad to have them back home.
That tweeter is amazingly good

I stupidly damaged one of my grille's cloth, so if you ever want to let one of yours go, or know where there's another, let me know
I only need the original cloth

Anyway, back on topic; I don't think you'll really need that step down kit and although I am not 100% certain (again, due to lack of spec sheets) if you plan to use the bi-amp-able mode for just the woofer section, as your new top end is in another box and being handled by another network altogether I assume

[badman]

You don't want vented mids crossing to the "sub" EV. Also worth considering putting some solid materials into the JBLs. This will reduce box volume and give you a higher Fc and Qtc, which will make the transition to the EV much easier.

As far as how to do the XO beyond that... that'll be... fun. You'll need to roll off the top of the EV somehow, and passives at sub freqs are pretty near out of the question, so maybe run 'em with a plate amp?

[Mr Wizard]

Do you have a second amp and electronic crossover?
Do you not like the Sentrys as they are?
Buy a powered subwoofer?
...Q1. At the moment I just have a old 35 watt per channel Technics receiver that was running the 4612OK's.

Q2. By themselves they do sound pretty good, but lack the clarity that the 4612OK's have.
The 4612OK's go down to about 80hz and the 500's down to 40hz in non step down mode.
The 500's internal crossover, crosses over the woofer at 1500hz.
Both pairs of speakers playing together sound kind of like they are stepping on each other.
The 4612OK's are 97db 1w1m 80hz to 16khz and the 500's are 96db 1w1m 300hz to 2000hz.
With both speakers in parallel 3.5 ohms, the 4612OK's are noticeably louder.
With both speakers in series 13.5 ohms, both pairs are fairly the same loudness.
Straight to 500's woofer in series with 4612OK's, 11.5 ohms, resulted in to much midrange from 500's woofer.

Q3. My initial thought was to try a powered subwoofer but because of my space restriction,
the depth of the 500's at 13 inches is ideal and the 4612OK's depth are 10 inches so they fit on top great.
I also wanted to keep the low frequencies stereo.
Far as I know no one makes a stereo subwoofer plate amp.
I might have to use two subwoofer plate amps to accomplish stereo.

Idealy would be a stereo 50-100 watt per/ch subwoofer plate amp.
With a variable 60hz-150hz crossover 12db or 18db slope.
And for 28hz step down mode a Built-in EQ with variable select frequencies 24hz-36hz, 6db boost, 12db slope.
All I then would need is one port plug for each EV 500.

[Mr Wizard]

I have looked for a circuit diagram for the EQ box but have been unsuccessful; EV material is hard to come by. There are always some of those SEQ boxes up for sale for other EV systems and I am certain that they could be easily modified with a few parts value changes to work with the Sentry(s), the only challenge then would be to find a good fitting port plug (makes me think of Zilch, God Bless him) and the damn circuit diagram

I sold mine around 2002 and regretted it immediately. In January of this year I tracked them down and bought them back. Some sort of very weird swelling had occurred in a few spots on one of the cabinets (NOT water damage) and they were all dinked up. Don't know how the idiot managed all that. I bought them back anyway, found some edges that were close enough (they needed foam and are a hard one to fit) and am glad to have them back home.
That tweeter is amazingly good

I stupidly damaged one of my grille's cloth, so if you ever want to let one of yours go, or know where there's another, let me know
I only need the original cloth

Anyway, back on topic; I don't think you'll really need that step down kit and although I am not 100% certain (again, due to lack of spec sheets) if you plan to use the bi-amp-able mode for just the woofer section, as your new top end is in another box and being handled by another network altogether I assume Wagner, Here is a EV schematic to build the EQ box.
The easiest way would be to find a EV interface A,B,C EQ box and change the four resistors as noted in schematic.
The EV interface A,B,C EQ boxes seem to be easier to find, the SEQ are hard to find.
The other option would be to build one from scratch.
The Sentry III, Interface D & Sentry 500-505 EQ boxes all use 32hz, 6db peak boost frequency.
The Sentry 505 uses the same components but uses a wall/ceiling mounting cabinet.
EV made a single channel EV XEQ-2 electronic Crossover/Equalizer step-down that would work, but you need two for stereo.
Problem with the EV XEQ-2 crossover is it only goes down to 100hz, I need it to go down to 80hz.

At these locations put in these resistors for 32hz boost.
R8 & R24, 13k ohms + - 2%
R10 & R26, 220K ohms + - 2%

The grills were replaced with black cloth by previous owner.
I do say they look nice because they match the 4612OK's black cloth.

As for port plug, a piece wood and a long threaded rod with two wing nuts.
The rod front to back through the center of the port.
Wing nut holds the round piece of wood covering the port.

Documents Attached:
Sentry 505 EDS
Sentry 500 EDS
SEQ EDS
JBL 4612OK
EV EQ Step Down Schematic

[Mr Wizard]

You don't want vented mids crossing to the "sub" EV. Also worth considering putting some solid materials into the JBLs. This will reduce box volume and give you a higher Fc and Qtc, which will make the transition to the EV much easier. As far as how to do the XO beyond that... that'll be... fun. You'll need to roll off the top of the EV somehow, and passives at sub freqs are pretty near out of the question, so maybe run 'em with a plate amp?I'll probably not use 500's tweeter and just use the woofer.

Ideally would be a stereo 50-100 watt per/ch subwoofer plate amp.
With a variable 60hz-150hz crossover 12db or 18db slope.
And for 28hz step down mode a Built-in EQ with variable select frequencies 24hz-36hz, 6db boost, 12db slope.
Know anyone that makes the above?

I did this same thing years ago but I stacked two 4612OK's on top of a Sentry III custom built 2 inch thick cabinet.
Using only the Sentry III's 15 inch woofer.
Never use it in step down mode, but it sure did sound sweet.
Didn't use one nail, just carpenter's grade glue (blue).
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Multiply by two for Stereo.
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