Lowering the crossover point.

[aditya]

I guess my argument isn't that I think the HF needs to be down to 1000 but that the LF doesn't have the ability to stay at 98-100db efficiency up to 1600. sounds like it's down to about 70-80db by the time it gets there and is leaving a huge gap in the loudness between about 1000 and 1600. Also going by 515 specs just because they have the same cone and voice coil I think isn't a very good decision either since about half the cone is robbed by a giant 6 inch felt dust cap behind the horn which coincidentally is also blocking the sound path as opposed to a normal 515 which has a much less restricted cone and 3 inch dust cap. It would be nice to have the ability to measure the actual response of the LF side of these things to get a grasp on how they are performing.

Yes you are quite right here about the differences between the standard 515 and the one in the 604. Yes, in the case of the 604, it will have a drooping o/p post 1K Hz compared to a standard 515. All the points that you have mentioned will have their influence. But I don't have any actual 'db' figures with me. But i think the combination that the 604 has with the Hf horn, it should be able to match it up. I have listened to them for nearly 2 years, and I am yet to find a substitute to be sounding so good and so full !

[aditya]

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.

[juniper]

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.

[GM]

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

[aditya]

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.

[Alien_Shore]

I'm never touching them again.

hahaha ok, if you say so!

[Alien_Shore]

35422-SMARTYPANTS.jpg
OK Let us know how they sound!

[Old Guy]

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.