Model 14 Crossover Info Needed Again

[Jim Butler]

Well, as is often been the case in my life, I spoke too soon. I hate that.

Seems one of my Model 14's is running with noticibly higher response in the horn. Its the one with the 10 Uf cap arrangement. I'm going to swap out the 902's and see if its them, but I'm wondering if the different crossovers for the Model 14 had audible differences? I have also heard that the driver protection circuit had issues. The light that says "to test" does not light up on either crossover when the button is depressed. Could this indicate an issue with the circuit?

[Richard C.]

Yes, Jim - you really need to "make" both xovers work the same, which means re-capping with the same values. I would suggest making both 6 ?f, install at least a 10 band (31 best) EQ, and than do some measuring tests. Before the flames start - about ONLY trusting your ears; you need to know what the accoustical output is in every band of frequencies.

With that said "IF I didn't somehow know that there was great potential in my Model 14's - I would have sold them after 5 minutes of listening". I felt sick for awhile! All the time gathering up components and researching. I couldn't believe that anyone would listen to these without major work. The upper mids were way too bright, so I got my Stereophile test CD, a tripod, a SPL meter. I measured the response at about 10' (where I listen in my room). I immediatly found that what I heard, I could also see.

I copied the schematic into my spice simulation program, and adjusted the xover design to be more like the Model 19 (I couldn't make the stock design work). I am very happy with the results, and I will be "keeping" these as my living room speakers. My Model 19's don't fit!

As far as the power limiting circuit. That circuit is designed to limit the power to ~70 watts into the "input" of the xover. When the average power is > ~70 watts (the circuit actually responds to voltage), this circuit inserts a 10 ohm resistor in series with the whole speaker! There is a relay that shorts out the resistor almost 100% of the time. I also had one relay with dirty contacts, so I always had the resistor in that circuit.

These Model 14's are 95 or 96 dB SPL/1 watt, so 70 watts in is extremely loud! The red lamp will flash and the test button will work, IF you turn them up enough.

Richard C.

[bfish]

Originally posted by Richard C.:
...(the circuit actually responds to voltage)...There is a relay that shorts out the resistor almost 100% of the time...

<font size="2" face="Verdana, Helvetica, sans-serif">I was wonderin' how that worked, thanks Richard. So you've got a relay coil across the XO in, with the NC contacts across the series R, and when the V is large enough to pull in the relay, the resistor shunt opens?

[Jim Butler]

HI Richard,
Thanks for the info and suggestions. My electronic knowledge is nest to zippo. Why would the 6uF version (having 4 less than 10) allow more high freq signal go thru the circuit?

I'll look over the crossover and see if I can figure out which cap to remove and how to do it. Another learning curve to climb.

Its driving me nuts because the speakers sound great to me. But its way obvious how screwed up things are with the differing crossovers. I totally agree with you, its impossible to "fix" by ear. I'll be getting a meter as well to take measurements (been wanting to do this for a while anyway) and hooking up my 31 band DOD equalizer.

[Richard C.]

BFISH,

So you've got a relay coil across the XO in, with the NC contacts across the series R, and when the V is large enough to pull in the relay, the resistor shunt opens?

<font size="2" face="Verdana, Helvetica, sans-serif">Yes it's very much like the Electrovoice STR, which is used to protect EV compression drivers. Altec adds a switch & lamp to test the circuit, but it doesn't seem to work very well. Both Altec & EV use a smoothing circuit (large cap) to stop relay ******r.

Richard C.

[Richard C.]

Jim,

The 10 ?f version lets thru more of the upper mids. Both versions pass the highs equally, and the woofer is driven full range. I changed that, plus added a Zobel!

I was able to get my Model 14's to sound very much like my Model 19's, even though the f3 is about 50 Hz, compared to the 19's ~40 Hz.

Richard C.