Bringing 828 cabs up to snuff...

[gortnipper]

+ your $75 dollar bucket-subs!

[alancohen]

+ your $75 dollar bucket-subs!

Best investment in years! They really are amazing. I'm making 2 more to run dual mono into 4 Ohms at 525W/ch. This way they'll be barely idling along. I'm putting two behind the A5s and then two more flanking my listening chair, close or far, I don't know yet. I'll have to listen and see what the room tells me.

Ed's instructions on how he sets his up:

I do not use subs as a loudness control! They are NEVER used in my system to make it sound "full" at low volume! I set the subs for the volume the music should be played at........here is how...........I put on something with good LF extension and turn the subs and xover down. I then play the track at a "LIVE" volume, meaning as loud as it should be for the recording to sound "real". I then slowly turn gain and xover up on the subs going back and forth between the two. At some point it will just be "right" and you'll know it. They should blend and not be noticeable until you switch them off and then the "room collapses". When set this way Pink Floyd will shake the room at the proper volume and John Prine will not sound like he weighs 400 pounds at the proper volume for his music. At low levels they will not be making much output but really they are, it's our ears that are the "problem" which is why they gave us "loudness controls" for low level listening.

[GM]

Yep, that's the way to do it.

GM

[alancohen]

In the catagory of "just can't leave well enough alone", I'm thinking about trying a little super tweeter on top of my A5s. I have a pair of Radio Shack 40-1310s from another life and want to see what they will sound like. I think they have a built in (crappy) crossover, but I'll probably make my own simple 2nd order L-Rs.

They can go 5K to 40K. I have a bunch of caps that I can swap in and out to see where they sound best, but I need to buy or make the inductors. What frequency would be a good place to start with my 288-8Ks? Do I use the 5K or 8, 10? I would just parallel the input off the 288 taps.

[alancohen]

With the bucket subs holding their own on the bottom I hooked up my RS super tweeters on top. Stock crossovers for now. They are 96dB so they won't shred the 288s. Actually they are balancing very nicely. I don't want to cut glass, just see if some sparkle makes a positive difference. So far so good.

[Alien_Shore]

man, those horns are sexy. I know why they were the priciest piece of that setup!

[kwingylee]

If you are agreeing to the fact that the loads are not resistive, then this itself is proof enough of the fact that both the sides are not independent of each other, and this is the sole reason why text book calculations for x-overs never work alright, which we all are aware of. Actually speaking, in this particular case of 16 ohms 515 & 8 ohms 288, if one goes for a 16 ohms filter-setup for the LF & a 8 ohms one for the HF in the parallel mode, then the o/p will have a slight bump around 250Hz and a suck out at 1KHz. If one switches to the series mode, then the x-over 'f' will shift to 750 Hz.roughly. This is nothing new, and you surely can visualize it loking at the ckt.

Regarding my suggestion of adding a series resistor to the 288 to make it behave like a 16 ohms driver, this is definitely better than the other choice (while keeping Hiraga's x-over in view). Actually it will help flatten out the dips and peaks of the driver to some extent. Ofcourse we have to bypass the inductive effect suitably. As GM has pointed it out many times....many actually run their A7s with the woofer (416x only as its cone cry helps here) directly hot, and the HF driver hooked via a series resistor (direct again) till the levels are okay, and then the series resistor is bypassed suitably with a capacitor.

And also not to forget the fact that the A7 is a very thrusty/forward sounding setup, and to make the sound flat & smooth is not an easy task. It will just shout back with the smallest error.

ALan, guys:

WHat was the final crossover configuration that was used for this system? Also I appreciate any suggestions you may have for the opposite scenario: a 8 ohm 515 woofer and a 16 ohm 288 series compression driver?

Kwing

[GM]

Nothing fundamentally changes, the horn needs shelving + likes to 'feel' a matching impedance, so theoretically a 16 ohm in series for yours, but always best to find the optimum using a pot, then replacing it with either a non inductive resistor or a grid of small resistors optimized for handling the highest frequencies if no super tweeter is used.

GM