Wait !!! You've gone through six different crossovers? Hmm ! The gentleman from Chicago should have suggested L-pads for his second build. This would have given you some control of the slope and the balance (similar to the model 19 crossover).Originally Posted by Seadweller
Seadweller - have you tried removing the 3 ohm resistor on the bass circuit? Or replacing it with a different value one? I know the MLTL design for these drivers call for it, but if the bass is anaemic in your room, maybe this might help tune to your bright room?
David
This is not the best solution but you can try this for an immediate temporary solution.....
Take any one box, and continue.
1) Arrange for some AC capacitors of 2-4-6-8-10 micro-farad values.
2) Arrange for some lamp cords. Connect it directly but separately to the 604's woofer & horn terminals, and bring them out thru the vent opening. Then strech them to a distance of around 10feet, so that you can sit & listen from a comfortable distance.
3) Bring out a similar connection from your amp-output to the same spot.
4) Take the GPA crossover, and connect the amp-cable to its amplifier marked terminals.
5) Now connect the woofer to the X-Over's woofer-output.
6) Do not connect the horn now.
7) Play some known music
8) Now start by shorting the woofer (across both the connection points) with a high value capacitor say 10mfd, and see how much of the shouty-ness has reduced. If too much reduced then use the next lower value.....and go on like that till you reach a position that you like.
9) Now while the woofer stays connected with the chosen capacitor......Connect the horn to the GPA X-Over's horn terminals....and listen.....to the whole thing...and try to asses if any further amount of that shouty-ness is now added due to the horn.
If you feel so, then disconnect only the +ve wires of the horn, and insert a cap (highest value) in series....and listen......if still shouty....then try with a lower value cap.....and continue till you get what you want.
Once you reach a suitable spot, copy the connections to the other box and listen in totality.
Hope this will be of some help and make you carry on with your project.
Aditya
Find some 904-8A or 604-8K crossovers. They are identical and match the manta horn.
Or possibly some 604-8H units, I believe they are the same.
As for the comment from Todd on the -8K magnets. I doubt this is true for the 904-8a as I have never felt mine shout from the midrange. Granted, the 904 has a diff woof cone, and I modified the HF to mimic the -8K and -8H.
I love the sound, mine don't go real low, but subs fix that in spades. The mids blend so well, these things disappear and all you hear is music suspended in space.
I've never heard the GPA 604's.
But I wonder.......
Are they really that good?
Are the crossovers really that good?
Altec got the dual shelved crossovers for these reasonably right, and they flat work.
Your test of removing the horn tells a lot in my opinion......the schematic for the stock crossovers for the woof is a simple 12dB/oct setup.
Maybe the woof of the GPA drivers just sucks?
Ever tried one of the vintage versions?
Ron
I think that Vuki's passive is worth a try. It sims well. Nice spread frequency with a dip in the middle and a rise for the top end of the horn. Looks like a ~2.5K notch.
I might replace the 4R7 and 27R with an L-PAD just for fine tuning. It's doing about ewhat my active crossover was.
Depending on one's listening preferences, room acoustics and system, varying (3R3 - 6R8) the value of 4R7 resistor would give wide enough range for tuning high freq. energy. There is no need to change 27R.
One cannot tune low/midrange with L-pad. It is done with series inductor value. Varying capacitor parallel to woofer would change only the upper part of woofers frequency response.
@ron,
before I decided to purchase the GPA 604H series II I had the opportunity to audit 604E in 602 EMI enclosures and 604H in 612B enclosres side by side. finding a serious pair of vintage 604H (last with alnico and first with tangerine phase plug) is a jackpot. only reason why I would shift from GPAs to vintage Hs when ever I get the chance to buy a pair of those vintage Hs is pure PSYCHOLOGY! and I'm quite sure that if I swap them I already miss the GPAs because I fell in love with this in-between vintage and modern sonic that might distinguish the series II from the original Hs I've audited ...
@seadweller,
I use the 604H series II in 'gutted' 612B enclosures. they are lifted from the ground via spikes, bent and sloped. also my room is quite huge (>40sqm) the distance while auditing is 2.5 to 3 meter. the bass is lovely delicate and subtle I've never heard before with my former audiophile systems that contained all tube gear and speakers for more than 15k. however in my experience cables and amplification are quite important next to the crossover. in my case triode in single ended is an outperforming match ...
good luck
I used a simular procedure when putting together a 3-way system last year. I also used DPDT switches to reverse the polarity on the tweeter and mid range speakers. It turned out that the mid range +/- were stamped incorrectly. I had to reverse the polarity on the mid range to connect it in phase.This is not the best solution but you can try this for an immediate temporary solution.....
Take any one box, and continue.
1) Arrange for some AC capacitors of 2-4-6-8-10 micro-farad values.
2) Arrange for some lamp cords. Connect it directly but separately to the 604's woofer & horn terminals, and bring them out thru the vent opening. Then strech them to a distance of around 10feet, so that you can sit & listen from a comfortable distance.
3) Bring out a similar connection from your amp-output to the same spot.
4) Take the GPA crossover, and connect the amp-cable to its amplifier marked terminals.
5) Now connect the woofer to the X-Over's woofer-output.
6) Do not connect the horn now.
7) Play some known music
8) Now start by shorting the woofer (across both the connection points) with a high value capacitor say 10mfd, and see how much of the shouty-ness has reduced. If too much reduced then use the next lower value.....and go on like that till you reach a position that you like.
9) Now while the woofer stays connected with the chosen capacitor......Connect the horn to the GPA X-Over's horn terminals....and listen.....to the whole thing...and try to asses if any further amount of that shouty-ness is now added due to the horn.
If you feel so, then disconnect only the +ve wires of the horn, and insert a cap (highest value) in series....and listen......if still shouty....then try with a lower value cap.....and continue till you get what you want.
Once you reach a suitable spot, copy the connections to the other box and listen in totality.
Hope this will be of some help and make you carry on with your project
Aditya
Again, don't know much about 604s. But could the L.freq section of the 604 be accidentally connected out of phase with the H.freq section?
Not meaning to say "you" connected the 604 incorrectly.
That's cool.
Vuki did you know that your HP filter (before the contour) has the topology of a 3rd order, but the electrical function of a 1st? You might double check me, but it looks like the filter functions is very near 1st order at 4KHz. A single 5uF cap would do the same. The inductor and resistor do pull it down a little faster. Did you do that by ear?
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