Why have full range speakers? Everybody just sets the crossover to 80hz anyways! (1 Viewer)

Christopher_Ham · Oct 10, 2003

I purchased a set of full range passive Def Techs that I am powering with an ATI 1505 amp (150 x 5), and a Lexicon dc-1 pre/pro. I set all of the crossover points to 80 hz, even my mains because after carefull evaluations, I feel it gave me the most impact. My question is, if even on high end full range speakers like B&w and Snells reccomend the same settings for crossover frequencies ran to the sub, why even buy full range speakers. What advantage does it have. The only thing I can think of would be possibly a better midrange. Or is there a better way I should be running my speakers, I have bp8's/clr 2002/ and bpx2's all capable of full range, but my system sounds better with all set on small. When I set them on large, the speakers don't mesh well with the .1 channel. Seems off.

Chris

Dan Driscoll · Oct 10, 2003

Music. Most 2 channel fans run straight stereo to the main speakers with no sub. This is why a true analog bypass is such a big deal on many multi-channel pre-pros. It allows you to bypass the crossover settings in the receiver/processor and send the full range signal to the speakers, including the

Eric C D · Oct 10, 2003

The "audiophile" wisdom is usually that the crossover should be 1 full octave above the -3dB point of your speakers. Someone can write a better description than I, but it's because the crossover isn't a brick wall. The spekaers are asked to put out sound below the crossover, and it can still be audible 1 octave below the crossover. Also, if the speaker is already attenuating the sound at the crossover freq, the effect combines with the crossover attenuation and you start to get a hole at the crossover freq.

So if you are going to use a 80 hz crossover, you'd like a 40 hz speaker. That's pretty full-range. Most sat/sub setups are compromises if you take a really close look at them.

The reason for your system not "meshing" could be because of cancellation effects. That's another reason for going with only one source of low freqs.

I, personally, have been using the sub with 5-channel, and running just my full-range speakers in 2-channel. I like the sound of both setups. Good luck with your choices.

John Garcia · Oct 10, 2003

Sounds like you have room issues with the sub, as noted above. Placement and room treatments can play a very large role in your results. I would recommend revisiting the placement of your sub, and if you haven't already, a complete calibration of your system.

With the capabilities of these speakers, I'd probably lower the x-over point a bit on all but the surrounds.

Heath_E · Oct 10, 2003

Christopher,

The truth is, your speakers don't go nearly as low as Def Tech claims. I also have Def Techs, BP2002TL with built in powered subs. My towers are rated to go lower than yours, 17Hz compared to 22Hz. In reality, mine only get down to the mid thirties, which would probably put yours up around 40Hz, possibly a bit higher. I was given those numbers for my speakers about a year and a half ago by Tom Vodhanel from SVS. I'm not sure whether he tested them or Tom Nousaine did. Anyway, the point is, if the theory about having a speaker capable of going an octave below the crossover point is true, then 80Hz would be about right.

Jason_Me · Oct 10, 2003

The "audiophile" wisdom is usually that the crossover should be 1 full octave above the -3dB point of your speakers. Someone can write a better description than I, but it's because the crossover isn't a brick wall. The spekaers are asked to put out sound below the crossover, and it can still be audible 1 octave below the crossover. Also, if the speaker is already attenuating the sound at the crossover freq, the effect combines with the crossover attenuation and you start to get a hole at the crossover freq.

Having no output from the speakers below the crossover (and the sub above) will give better performance. Most people have trouble integrating subs because of phase problems. A speaker that naturally rolls off at 80 hz, and has a 24 db/octave crossover at 80 hz will have a relatively small null in the crossover region with the speakers and sub completely out of phase. A full range speaker will be canceled out over a broader range, and sound disconnected from the sub.

If the phase is set correctly on both setups, they will sound identical in the bass region (assuming everything else is the same).

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BruceD · Oct 10, 2003

A speaker that naturally rolls off at 80 hz, and has a 24 db/octave crossover at 80 hz will have a relatively small null in the crossover region with the speakers and sub completely out of phase.

Actually most of the receiver's and prepros that implement the 80Hz crossovers (XO) don't use 24dB/octave filters on any of the high-pass XO. Instead, they use a 12dB/octave filter that is supposed to combine with the natural 12dB acoustical roll-off of the speaker itself.

THX certified speakers are probably the only speakers that really have an 80Hz 12dB acoustical roll-off.

For most of the receiver's and prepros, the sub output's low-pass XO does use a 24dB/octave filter.

The entire objective is to get a smooth transition across the XO frequency range between speakers and sub. This typically takes place across a full octave or more of frequencies and you want the combined signal at equal SPL levels throughout that frequency range.

Mismatched high-pass vs. low-pass XO filter slopes (12dB/octave vs. 24dB/octave as an example) will definately make that a tougher task.

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Jason_Me · Oct 10, 2003

The entire objective is to get a smooth transition across the XO frequency range between speakers and sub.
This typically takes place across a full octave or more of frequencies and you want the combined signal at equal SPL levels throughout that frequency range.

The problem is getting a smooth transition that dosen't include a huge null around the crossover point.

If you get the phase correct, I fail to see how a speaker with additional output below 80hz makes a positive difference. Your speakers and sub are in different locations, when they're all playing the same signal it creates timing issues (delay settings aren't precise enough). A lot of speakers cant handle any kind of bass at high spls, which introduces lots of distortion to the signal. The amp has to work harder as well.

Overlap is not good with a sub.

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John Robert · Oct 10, 2003

If you listen to Hi-Res music, most systems do not have BM for this analog signal. Full range speakers are a real advantage here...

dave alan · Oct 10, 2003

THX designed bass management to be used with sealed satellites, which have a natural roll off of 12 dB/octave.

When a 12 dB/octave high pass filter is applied, the resulting slope is 24 dB/octave.

Thus, the 24 dB/octave low pass filter applied to the sub makes for a proper 4th order crossover.

The problem with this system is that most of us have ported satellites, which have a 24 dB/octave roll off.

When the 12 dB/octave high pass filter is applied, the resulting slope is 36 dB/octave, which makes unity gain at and around the crossover point impossible. A 'hole' results. Phase alignment won't correct this mismatch.

The so-called 'seamless blend' between sub and sats is impossible with most pre-pros and receivers because most sats are ported and most BM chipsets don't offer selectable filter slopes.

In any case, when using a 4th order crossover, the crossover point should be set from 1/2 to 1 octave away from the F3 of the satellite (meaning some experimentation is called for).

If the crossover is set at 80 Hz, the satellite should be capable of 40 Hz F3 and the sub, likewise, should be able to play to 160 Hz.

Bill Polley · Oct 11, 2003

I have been asking the same questions. My mains are ported Axiom M80ti speakers, my center is a sealed Axiom VP 150, and my surrounds are sealed Axiom QS-8 quadpolars. From What I am reading here, I should set my mains crossover at a minimum of 60hz and let the crossover perform all of the rolloff, set my center at 80hz, and my surrounds at 100hz, allowing the natural sealed box rolloff to occur (-3db points of 85hz for the center and 95hz for the surrounds).

My SVS is an outstanding sub but it tends to roll off in my room at about 105 hz very quickly. The setup I have described seems to work very well to my ears, but I have no way of measuring phase and time-delay problems. To me it sounds better than other crossover points, but how can I measure these parameters without expensive equipment so that I can truly know if I am making the best choice of settings?

PhilBoy · Oct 11, 2003

Trust you ears.

I have been experimenting with small/large combos for 2 months now and I find that setting all speakers to small and letting my HTR5540 to the crossover at 90Hz works the best for me for both music and surround.(Turn the crossover setting on the sub all the way up).

I think the days of fridge size speakers are over with all of the advancements in subwoofer technology. Smaller speakers are easier to place and with a good set of stands the installation and balancing possiblities are endless.

With a 'large' set up I was having standing wave/cancellation problems.

N.B. I don't have Hi-Res DVD-A or SACD so I can't comment on large/small for that set up.

Mark C. · Oct 11, 2003

I figured that out about three years ago. Out with the floorstanders, in with the satellites. It's the way things were meant to be, at least for home theater. Music is a completely different requirement.

Christopher_Ham · Oct 11, 2003

You all have overwhelmed me with info. It seems there are advocates on both sides of the fence. I need to learn more about how to use my spl to determine the right crossover frequency. I have a Dolby Digital test disc that has both high and low frequency testing material. All speakers are in phase, including the sub.

BruceD · Oct 11, 2003

I completely agree with Dave and because most prepros and receivers don't offer flexible bass management for speakers that are not THX certified, I rolled my own.

I found the best solution to be an external active crossover between my main towers and the sub(s). Even though my main floor standers are very good speakers ($5800) with a -3dB of 32Hz, I cross them over to a sub.

This allows a more precise transition to the sub at the best frequency for my room and speakers, which @ 60Hz is almost an octave above my main speakers -3dB of 32Hz. Because my sub is less than 6 feet from my left main speaker, phase and timing issues are not a problem.

I set my mains to Large, center=small, surrounds=small, and sub=NO. This sends all bass (re-directed plus LFE) to the main speakers. Click-on my Equipment list below for more details on hookup.

My crossover is a Marchand XM-9L with stereo symmetrical (low-pass & high-pass) 4th order (24dB/octave) Linkwitz-Riley (zero degree phase offset) filters.

BruceD · Oct 11, 2003

I need to learn more about how to use my spl to determine the right crossover frequency

Christopher, you need to be careful about what you use for source material when searching for the right XO (crossover) frequency.

Because your room's dimensions produce what we call room modes (frequency SPL peaks and valleys) at certain frequencies (mostly from the sub output), the SPL meter will register those peaks, instead of the original calibration signal.

That means you should use a source signal comprised of warble tones, like the 1/3 octave frequency tones on the Stereophile CD #2. These warble tones don't let the room modes (also called standing waves) build up and influence the meter's readings.

This also means you will do the testing from a source CD with a digital connection to the receiver or prepro which is set to stereo mode (music with sub) and not analog bypass.

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dave alan · Oct 11, 2003

BruceD, you got it goin' on.

Excellent configuration, and Dr. Phil (Marchand) makes deadly accurate, very high quality crossovers (as you no doubt know first hand).

Now, if you set your center and surrounds to 'small', doesn't your pre apply a crossover, and which one did you use, and why? (sorry, just curious)

LanceJ · Oct 11, 2003

.....and if you really don't want to mess with a sub, just don't.

In other words, program your receiver for "NO" sub and it will reroute the low stuff to your front mains (I'm doing this right now with Bostons that use 8" woofers). Tada! no messing with sub placement, fussing with crossover points and related phase cancellation worries (assuming the soundtrack engineer knew what he was doing :frowning: ). If you can't tell by now, I'm not into rattling my walls with bass.

The only reason I am researching a subwoofer now to buy is to complete my dvd-audio music surround system.

So personally speaking, I'm still "into" large floorstanders. And IMO from strictly a sound quality viewpoint, large speakers still sound better--fuller and richer, with wider more three dimensional imaging--than small satellite speakers.

So in a "typical" house living room (say $200K range), for boring people like me a pair of good floorstanders with two 8" woofers or one 12" should give a person just enough rumbly bass to let you know a starship is passing overhead or if an ammunition depot is exploding.

And when I get married? To keep my big speakers, I'll let her keep the pink lacy curtains. I've been told a good marriage includes being able to compromise gracefully.

LJ

BruceD · Oct 11, 2003

Lance,

In other words, program your receiver for "NO" sub and it will reroute the low stuff to your front mains (I'm doing this right now with Bostons that use 8" woofers). Tada! no messing with sub placement, fussing with crossover points and related phase cancellation worries

Just a little more info; the mono bass being sent to both your left and right mains (two simultaneous bass sources) will typically cause phase problems in most rooms. Also, the typical best location for left and right mains is not typically the best location for a

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BruceD · Oct 11, 2003

Dave,

Now, if you set your center and surrounds to 'small', doesn't your pre apply a crossover, and which one did you use, and why? (sorry, just curious)

Yes, that is true. I cannot select a frequency with my current prepro, when I set the speaker (center and surrounds) to small I believe it sets the XO @100Hz. Not ideal but good enough for the $$$ since I'm 90%/10% 2channel-music/HT.

Yes, I really like the Marchand because it has level controls for both channels of high-pass and low-pass as well as a level "Q" control at the exact XO frequency. It also has a bass SUM switch to combine L+R bass output to mono.

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