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matjolic 12th June 2006 06:54 AM

EV vintage three-way system design
Hi all,

I'm new around here, but my passion for sound has lead me to ask for your help. My dad just gave me the components to the sound system he had built for himself back in the 70s. All components are from Electro-Voice and consist of the following:

2 x T35 VHF Compression Drivers
2 x MC8 loudspeakers
2 x SP12C loudspeakers (designed to work as woofers also)
X8 800Hz crossover
X36 3500Hz crossover
AT38 8ohm level control

I have all the original technical spec sheets as well as a technical bulletin with guidelines to building a bass reflex enclosure. I can provide any technical information needed, as I have these on hand.

I want to build the best for this system to sound as well as it should. Here are my first question:

Should I built enclosures for the 3 components or built separate ones for the 12inch woofers and others for the loudspeaker and tweeter?

Any guidelines as to which way I should dive into this project would be very pleasing! Thanks

kevinkr 13th June 2006 12:29 AM

I just built a speaker system based on a design originally from a Jensen manual published in 1955. (See the Onken enclosure thread, my first speaker project.)

Perhaps EV published a project book in which this driver complement appeared. You could do much worse than to just follow the documentation you have, paying particular attention to box rigidity and panel damping.

mashaffer 13th June 2006 12:53 PM

Are the 8"s capable of reasonably good full range operation? If so you could try those on an OB with the HF horn crossed as high as possible and the 12"s in matching ported boxs with slight bass extended tuning (tuned a bit lower than optimally flat). Of course that is just based on my current tastes. All subject to change (viva la DIY). ;)


matjolic 13th June 2006 02:00 PM

Thanks for your input,

first, please explain what an OB is, i'm fairly new to this... lol

I've looked into this project further and i might opt to make 2 sets of speakers, for two different rooms in the house. The EV X36 crossover is rated at 3500Hz, and the horn from 3500-20000Hz. They are recommended for use with the SP12Cs as a two way system and should provide for good enough sound for my sound listening/ party room... The SP12C is designed as a loudspeaker, but can also act as a woofer... I'm beginning to think I'd be overdoing it with a loudpeaker at low frequencies (1st crossover, the X8, at 800Hz) a second loudpeaker for the mids (2nd at 3500Hz) and a horn for the rest... Seems like overkill to me...

So I might design a bass reflex enclosure based on the EV instructions I have in hand (the SP12C and T35 were made for one another) and another bass reflex, single-way enclosure for my MC8s to put in another room... with a range of 50-13000Hz these should be sufficient for "ambient" purposes in my work room, and i can always add a horn to it later on...

Keep me posted with any ideas that cross your mind, and I be sure to give you input as the project goes on. Many thanks.

kevinkr 13th June 2006 02:22 PM

It's not really overkill to use the three drivers together, I lived for a long, long time with a 2 way system (jbl) that sounded quite good, having recently switched to a 3 way system I now realize that the midrange was significantly compromised by the large driver (15" woofer crossed over at 2.4kHz) used to reproduce it. (Directionality, doppler distortion, transient response.)

Crossing over a 12" woofer at 3.5kHz is going to be far from optimum even though the driver might be stated as a full range type. (Common JBL parlance actually.) Think break-up modes in addition to the things I have mentioned above.

I think you'll be a lot happier in the long run if you stick to your original plans to use the three in combination.

There are many instances in the product lines where Jensen, JBL or EV had 2 way or three way systems that were basically identical except for the addition of the mid-range driver and an additional cross-over box. The 3 way system was always regarded as the performance leading package at significantly greater expense.

The open baffle suggestion with the MC8 and the T35 sounds interesting and the SP12C's installed in an appropriately sized BR enclosure. I would imagine that you also have the information in your possession for a suitable 3 way cabinet design.

You can probably find the TS parameters for the SP12C by googling for it. Possibly the parameters can be found here: Knowing this will allow you to design the optimum box, you also need to know the required box volume for the MC8 if you use it as a midrange within an enclosure. (It can't share volume with the woofer.)

Just my thoughts, YMMV..

mashaffer 14th June 2006 03:40 AM

OB=open baffle. Essentialy mounting the drivers on a big flat piece of wood. Gives nice imaging. Putting the Big woofs in a nice ported boxes to cover everything below 80Hz or so makes up for the lack of bass in the OB. The horn tweeter crossed very high 5K at least better 7K-10K if possible fills in the really high stuff and gives enough dispersion without destroying the great full range imaging from the OBs.


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