Schematic available for 604 xo with Mid Freq EQ

[jmarkwart]

Hi All,

I just updated my web pages at http:/home.earthlink.net/~jmarkwart/ to include both pdf and jpg downloads of my 604B phase correct crossover with Mid Freq EQ. If you use one of my earlier 604 or 605A/B 16 ohm crossover designs, I urge you to consider modifying it by adding a Mid Freq EQ circuit.

Jeff

[Richard C.]

Jeff,
I looked at your web pages and downloaded the Xover diagrams. I will use Electronics Workbench (Multisim) to simulate these circuits. I have found this analog simulation program to be very valuable in predicting the electrical performance of crossovers. I can plot freq. response of each filter section and the phase relationship between the drivers thru the crosover region. It can't predict sound level variations or really what it will sound like, but I have found that I now want more than a 1st order HF crossover! I include the inductance of the drivers (as best I can measure) in the simulations-about 2mH for 12" Model 14 LF and .15mH for the 902. I want to look at the phase relationship of your phase correct 604B crossover. I am using 902/811B horns with 416-8B's(Model 19)and it would be nice not to have to bi-amp in order to have correct phasing at crossover. I have simulated the crossovers of the model 14, 15, & 19; and the model 19 is much more complex (better). Thanks for the info and I enjoyed your web pages!
Richard C.

[jmarkwart]

Hi Richard,

Glad to hear you are going to have a look at my designs. Welcome to the time domain world.

I have found that a major challenge in proposing crossovers for Altec speakers is properly accounting for horizontal driver offsets, and there doesn't seem to be much readily available information on this subject. Check out Bruno Carlsson's article, Driver-Offset-Related Phase Shifts in Crossover Design, Speaker Builder, issues 1&2 of 1995, for a rare, interesting discussion on this subject. Compression drivers in Altec cabinets generally have their acoustic center situated well behind the woofer's, and the resultant phase interaction between the two driver's combined outputs in the crossover region should be considered. I looked at a number of software tools for modeling filters but finally settled on CALSOD (http://members.optusnet.com.au/~audiosoft/). I not familiar with Electronics Workbench, but CALSOD not only allows a filter's electrical performance to be predicted, but models the drivers, as well as the combined driver/filter's performance at a common observation point with horizontal driver offsets taken into consideration. CALSOD is a great tool for playing "what if" games with differing Altec horn/woofer spacing and proposed filter types and orders.

While phase is important, I'm actually very excited right now about the vintage Altec inspired Mid Frequency EQ circuitry I recently incorporated into my designs. It seems to me that re-shaping the 1" compression driver's response has produced more audible results that make them a pleasure to listen to than the earlier crossover phase improvements. But hey, you might as well have both!

Happy Hunting,

Jeff

[frankmalz]

Hi Jeff,

how can i implement the mid freq eq in your 605A crossover schematic?

Thank you very much

frank

[jmarkwart]

Frank,
Delete the L-pad and substitute the MF EQ circuit. Same EQ circuit as the 604B. I'll email you a marked up copy of the 605 schematic.
Jeff

[Richard C.]

Hi Jeff,
I am interested in this Mid freq. EQ circuit. I ran a slow sweep from 20kHz down on my Model 14's at 5V RMS and I was not pleased with the raspy sound at 400 to 800 Hz out of my 902A drivers! Since this is a 1500 Hz crossover, they should have been fairly quiet. I'm using an "original" crossover, which only has a single pole HF section (and virtually nothing between the input terms. and the woofer). Your post made me think about improving my crossovers; I just didn't know what I needed to do. I just bought a pair of Model 19's, but I really can't set them up for testing, yet. Jim Easley sent me a Model 19 crossover schematic and I have verified it with my crossovers. One thing I've noticed is the HF section is very similar to yours. All the componants are in the very same locations, but with different values (8 Ohms and 1200 Hz). I think I have every issue of Speaker Builder magazine, so I found #1 & #2 of 1995. This article is very technical and will take me awhile to absorb it. I hope this isn't too far off topic.
Richard C.