Crossover question

[Fitts]

Question:

If no crossover is the best crossover and a woofer can not be harmed by HF, why don't we design our systems to make full use of the woofer's range with no crossover and then just use a crossover for the HF that picks up where the woofer leaves off in a complimentary fashion?

Wouldn't the woofer sound clearer and better with no inductors or capacitors in the signal path?

Has anyone done something like this giving careful consideration to the natural rolloff of their woofer (like an Altec 416) and then matched the natural rolloff of the woofer to a 12 or 18 db per octave crossover feeding a quality Altec horn?

I am just curious about this and would appreciate any insights anyone has to offer.

Thanks,

[GM]

Uh, due to the well damped roll off of the 416/421/515 series, many folks over the decades used either just a choke or nothing at all on the LF for HIFI apps.. The 515 goes so high, just a tweeter horn XO'd around 5kHz IIRC is required if you like a laid back presentation and don't mind a relatively narrow 'sweet spot' like a fullrange driver gives. At this frequency, a compression driver with no lens except for a chamfered hole in the baffle works fine if a 2nd order XO is used.

What you do WRT XOs is about distortion/power handling, so if you're like me and prefer to be 'front row center', then you need all the dynamic range (transient peak SPL) you can eek from the system, but if you're using SET or modest power tube P-P, then either using digital EQ or only enough parts to do a line level contour to get a ~flat in-room response is the way to go IMO.

GM

[Richard C.]

Dave,

Altec had at least two home HIFI speakers that were just like what you were wondering about. The Model 15 has nothing but wire between the input terminals and the 12" woofer. The Model 14 only has a very small inductor, (part of the HF adj - 10kHz), in series with the 12" woofer. It has no effect at less than 5kHz or so. These two models crossover at ~2kHz or so.

I am sure other people could come up with more Altec models that wire the LF driver direct.

Richard C.

[selmerdave]

The N1500A for the 604 as far as I can tell has the LF running full-range. My 604E's have just a cap and 2 resistors for an l-pad on the HF, nothing else.

Dave

[Mirrophonic Sound System]

Some say the steeper the X'over slope the better. One company
offers crossovers that are up to 300db/oct - see http://www.clarityeq.com

By feeding above-crossover audio to the woofer the result will
be undesirable byproducts - that is additional midrange from
an "inferior" HF driver (the woofer having higher mass and time
displacement will create phase and transient smearing

[jmarkwart]

Dave,

I'm no series-type filter expert, but the schematic of the N1500A shows a second order low pass filter for the woofer (1.5mH series inductor, 14ufd parallel cap), that is further modified with two resistors (R1 & part of R2) parallel to the inductor. That would provide a -3dB point for the woofer of approximately 1500Hz. I've measured the SPL of Altec 604E woofers running un-filtered, and they can get pretty bumpy (+ & -6dB peaks) above 2kHz.

Jeff

[selmerdave]

Jeff,

Obviously my electrical knowledge and schematic-reading stands to improve. I now see you are right. Funny thing is, I quite like the sound I get with the woofers full-range, for me considerably more transparent than when I had the LP at 1500 (the exact same component values now that I realize it). Maybe it's time to do some more investigation, this is getting off topic but I was not fond of the sound I got with a first-order on the HF at 1800, it sounded like there was a "gap" in the spectrum (with the LF full-range). Since you said that you got the best results with a 2nd or 3rd order at 1800 I think I'm going to have to revisit that too.

Dave

[HiFiPlayer]

I have tried cut away all coils and parts from LF Xover, just a capacitor as bypass on woofer's +- .

[dennis gilliam]

Some old Biflex 15" speakers had the VC tied to the input terminals direct, with a small NP cap in one leg going to the tweeter (paper cone job) suspended on a steel strap across the front. I have a pair fo these, and will look for a model #.

I've also run 416's and 515's on moderate power (<20W), in 828 & 816 cabs with just an oil cap and pot for the horn driver with very good-sounding results.

DG

[Fitts]

Thanks to everyone who replied. I think I am going to wire up and A/B comparison switch so I can flip my woofer between filtered and unfiltered and do some listening tests.

Regards,