Re: Lowering the crossover point.
Quote:
Originally Posted by
cradeldorf
Yep putting the caps before the attenuator has made a difference. They sound better and stay sounding better. Before it seemed like they sounded good for a little bit but then fell off like the resistor/attenuator was heating up and building resistance. The 2.5 inductors will be here tomorrow and I'm hoping they'll quell the boxy cabinet sound more. I'm basing that on the fact that when I had no inductor on them the boxyness was worse than it is now with the 1.5 inductors.
Good to hear that. Did you check with the 1.5mH+10mfd combo or the earlier 1.5+6.3 combo ?
Yes, about the attenuator, I think it must have got fried already. Better to get it replaced, at least for dependability sake.
Talking about the xover, you can not (should not) put a cap higher than 10 mfd on the HF side. Yes, you can play with the inductor value.
Another good thing will be to procure a db meter, (the standard 30-8KHz type if not more), and take a real mesurement. B'coz, even with a pair of trained ears, it still gets at times very tricky to tame down things in audio. At least one will know for sure where what is, and then adjust accordingly.
Re: Lowering the crossover point.
Quote:
Originally Posted by
cradeldorf
Which model of 604's do you have? Mine are 1954 604C's.
I was actually talking about a pair of 604-8Gs at my friend's place. We both were put up together there for 2yrs, and everyday we used to listen to them in the late evenings. The cabs were BR, approx 12 cu.ft.
Just read about your plans to go for a db meter. I am sure you are going to make those 604s rock. I love their resolving abilities. Good wishes in advance.
Re: Lowering the crossover point.
I run my 604's at 1250 per what my tech measured? and they sound really good to me, with a little eq. I have GPA crossovers, and that mellowed the sound a bit, and they sounded more like M19's, so I put the original xover that came with the speakers back in. I am glad I have never put more than 3 watts into them after reading this thread.
Re: Lowering the crossover point.
Apparently ya'll haven't seen Jeff's 604E HF measurements, which should be pretty typical. Ditto his thoughts WRT loading caps [which mirror mine]: Altec Compression Driver Rear Loading Caps
GM
Re: Lowering the crossover point.
Quote:
Originally Posted by
cradeldorf
I was not aware of that. Is that because your calling the DCR the ohm resistance? I didn't think they are the same? Because measuring DCR and measuring ohms seem like two different processes when I read up on testing inductors it wasn't a simple measurement like a DCR measurement is?. I was calculating them using the 16 ohm rating.
The 16 ohm thing is called as the impedance, which is DCR+reactance. DCR is constant, but reactance varies with frequency, and as a result impedance varies. To calculate xover component values at a particular 'f' one has to know the impedance at that 'f'. The specified impedance (ohms value as you have said) for a driver generally means it to be valid at 1KHz. At other freq it will be different, even may become the same as the DCR. So here comes the 'impedance-graph'. Now just b'coz the graph is in hand does not mean that the computed values will be the workable ones. This is so b'coz, as the graphs are not straight lines, the resultant filter response slopes will be far from what what was calculated. So now comes the difficult part, that is to adjust the values of the components, type of the filters, choice of xover-'f' etc., so that it can deliver the goods.
Re: Lowering the crossover point.
Quote:
Originally Posted by
cradeldorf
I'm never touching them again.
hahaha ok, if you say so!
1 Attachment(s)
Re: Lowering the crossover point.
Attachment 1481
OK Let us know how they sound! :)
Re: Lowering the crossover point.
Quote:
Originally Posted by
cradeldorf
I was not aware of that. Is that because your calling the DCR the ohm resistance? I didn't think they are the same? Because measuring DCR and measuring ohms seem like two different processes when I read up on testing inductors it wasn't a simple measurement like a DCR measurement is?. I was calculating them using the 16 ohm rating.
DCR is DC (direct current, or zero Hz) resistance. There is no such term as ohm resistance. If specified as resistance, it is DCR. If specified as impedance, a much bigger can of worms opens. To vastly over simplify, impedance is effective resistance at a specified frequency, an impedance curve is specified at enough points to allow a curve to be drawn between. Impedance is higher than DCR, which is why an 8 Ohm speaker measures less on DC multimeter. 8 Ohm would be "nominal" generally a mean figure. Not to be confused with Sports Illustrated models, who have mean figures of their own.
Re: Lowering the crossover point.
You know the old saying goes something like this.. "If it Ain't Broke, it Doesn't need Fixing" ? :p
But FWIW Jeff Markwart gave me some great advice.. I have 604-8G's which are a little different then your 604C's. But his 604-8H crossover sounds great with my 604-8G's.. I would check his site and go over the schematic for that network...
http://home.earthlink.net/~jmarkwart...les/604-8h.pdf
http://home.earthlink.net/~jmarkwart...4-8h_gsmpl.pdf
http://home.earthlink.net/~jmarkwart..._8Hpcwmfeq.pdf
http://home.earthlink.net/~jmarkwart/id4.html
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Re: Lowering the crossover point.
The Jeff-xover for cradeldorf will be this one.
Altec Lansing 604B Phase Correct Crossover
This has been modified (16 ohm version) to suit the 604B, and hence will also be good for 604C.
Is the DCR of a 604B/C is at 8.3 ohms ? Jeff's site says nothing about this. Also there is no imp-graph. Only the HF side is there. He only mentions it as a 16 ohms driver. After GM's hint in this thread earlier about Jeff's work, I have been searching everywhere. Finally I found one page from somewhere on the net that I have lost trace of, and it says the 604B to be of 10.59 ohms, and the 604C of 11.10 ohms. The measurements were taken in the yr 1971. The Altecs are towards the bottom of the page.
Attachment 1482
Cradeldorf had got these refurbished at GPA. I think they can confirm about this parameter issue. Otherwise the xover may not match. Ofcourse the best will be to measure them up.