80Hz or 100Hz. Which crossover is better? (1 Viewer)

[GregBe]

Here is my dilemma. My front three speakers have a +-3db of 65 Hz. My choice in crossover for my receiver is 80, 100, or 120. If I am understanding this correctly, it is a borderline choice between 80 or 100. When I listen to music, they sound pretty similar. 100 Hz sounds slightly fuller, but slightly boomier. These characteristics are very subltle, and I had to listen very hard to distinguish them. To be honest, in a blind test, I am sure that I would have trouble picking out which was which. In my mind, here are the things I am weighing.
1) Go with 80 Hz because it is the standard
2) Go with 80 Hz because my sub is in the rear of the room, and I will have less problems with localization.
3) Go with 80 Hz, because if I don't hear a difference, you want as much playing from your fronts that you can.
4) Go with 80 Hz so the sub won't have to work as hard and in theory should be cleaner and less boomy.
5) Go with 100 Hz, so the fronts and receiver don't have to work as hard at higher volumes and and would have less distortion.
6) Go with 100 Hz, because my surrounds play down to 90Hz. I know this is less critical than my front soundstage, but I am sure 100 Hz is a better crossover for them than 80 Hz.

Normally, I would just go with what sounds better, but since I really can't distinguish the difference, what direction makes for a better choice in theory.

Greg

 

[ScottCHI]

the actual "rule" is to set the xover an octave above your F3. an octave above 65Hz is 2x65=130Hz.

 

[Phil Iturralde]

The x-over will help blend the lower frequency (sub) to your HT speakers.

If your surround speakers honestly** have usable lower frequency that goes to 90 Hz, then you're right, use 100 Hz x-over all-around.

Make sure you have turned-off your sub's x-over if you can, ... if you can't, then dial the sub's x-over to MAX and let your AV Receiver handle the x-over chores.

**Objective tests @ the Front Speaker location usually reveals speakers not meeting their lower frequency MFG. spec'd.

Some Examples: (S&V = Sound and Vision OBJ Test Benchmark)

Acoustic Research HC6
AR HC6 MFG. Frequency Response: ....... 80 Hz-20KHz+/-3dB
AR HC6 S&V HC6 front left/right... 125 Hz to 20 kHz ±5.1 dB

Energy Take 5.2
Take 2.2 MFG. Frequency Response: ... 80Hz -20kHz +/- 3dB
Energy S&V Take 2.2 front left/right........ 110 Hz to 16.3 kHz ±4.5 dB

Klipsch Quintet
QUINTET SAT. II MFG. Frequency Response: ... 100Hz-20kHz±3dB
Klipsch Quintet S&V front left/right. ............... 188 Hz to 20 kHz ±3.4 dB

Phil

 

[Brian Fellmeth]

The only downside to 100 Hz is the localization. Repeat you listening test and try to focus just on that. I don't think points 1,3 and 4 on your list are significant.

 

[ChrisDixon]

I think it depends on the sub as well. The Paradigm PS1000 that I used to own was a bandpass sub, so 100 Hz was not an option since it was too slow and boomy for tight music. If you have a faster, tighter sub then you may find that 100Hz has fuller mid-bass.

Chris

 

[JohnDG]

The room also is a factor. My fronts are corner loaded (no choice) and I found that moving the cross-over up to 100Hz tamed a peak at 80-90Hz.

I would suggest running some tones through both your front left and front right to see how the cross-over options hurt and/or help your room's frequency response curve.

In addition by using semi-cascading cross-overs, that is using cross-over settings on both the sub and the receiver within a 10-20 Hz range, you can further tweak the curve for peaks. Note: cascading cross-overs are normally not recommended.

jdg

 

[GregBe]

Thanks for all of the input guys. Maybe because it has been drilled into my head, I want to like the sound of 80Hz better. It is really hard to be objective. I will try all of the above advice this weekend. It looks like in the end (assuming that localization is not an issue), that 100Hz may be a better choice. Any additional thought and things I should be listening for this weekend would be much appreciated.

Thanks
Greg

 

[BrianWH]

I had a similar question here a few weeks ago. I have a pair of bookshelves up front with the same specs 65Hz. (Boston CR65). I found that they actually did perform to spec but I still liked my crossover set to 100 for movies, and 80 for music. I don't have a localization issue with 100Hz because I have a second sub mounted opposite the first, but I agree that the difference is somewhat subtle. I just feel that the smaller drivers in the bookshelves produce tighter and cleaner bass above 80Hz than the two subs can produce. Even by themselves, the bookshelves sound great without the subs for music.

Brian
my HT

 

[Brian L]

Can you point me to an authoritative site that lists this as a "rule"? THX? Dolby? M&K? Russ Hirschelman? Anyone?

Its my view that this is a very poor sugegstion, and I want to yack every time someone repeats it. If the -3dB point of my mains is 65hz, an 80 hz crossover will be fine.

Once you get above about an 80 Hz crossover, the sub becomes localizable. And when that happens, you loose the ability to place it optimally in the room. Thats why THX standardized on 80 Hz. As long as your mains are OK to 80 Hz or lower, then you do not want to go any higher.

And whatever they are capable of, you would want to crossover over at the next frequency above the -3dB point. You want that crossover as low as it can be without having holes in your response.

BGL

 

[ScottCHI]

i understand the importance of keeping the xover as low as possible. i also understand the reasoning behind that "rule". and i also purposefully bound the word, rule, in quotes in an effort to emphasize what is perhaps, at best, optimism and at worse, a misuse of the word. would the word "recommendation" be a better choice?

unless you're filthy rich, ht is all about compromise, btw. i'd run my stuff at 80Hz, too, in this case.

 

[Brian L]

No problem ScottCHI, and I am not trying to bust your stones. I just find an octave above to be a really bad idea, and it is repeated in many threads on many forums.

I wish I could track down the origin of that suggestion.

BGL

 

[Edward J M]

Scott's recommendation comes from an analysis of the high pass filter slope, the design (sealed or vented) of the speaker in question, and its F3 point.

A typical BM circuit in an AVR will have a 2nd order high pass filter, and a 4th order low pass filter.

If you set all your speakers to small, each channel will be high passed at whatever frequency you select in the AVR, again typically at a 12 dB/octave rate.

At the same time, the AVR will sum every surround channel, and the LFE channel together, and low pass them at the selected frequency and send the signal on to the subwoofer.

At the selected filter frequency, the amplitude of the signal to both the surrounds and the sub will decreased (typically by 3-6 dB). The sum of the sub output and the surrounds output at the selected xo frequency "should" result in a flat response at that point, but in reality that is not usually the case.

Irregularities in the FR at the xo are all too common, partly due to room acoustics, and also partly due to the fact that the slopes of the high/low pass filters are different, and the natural roll-off of the surrounds is not always 2nd order, and doesn't always start to occur at the chosen xo frequency. A vented surround for example has a 4th order roll-off below the tune point.

In the day, THX recommended an 80 Hz xo and the 2nd order high pass and 4th order low pass filter rates because THX certified surround speakers were sealed units with a natural 2nd order roll-off and a tune point of 80 Hz.

The combined effect of a 2nd order high pass filter at 80 Hz, and a 2nd order natural speaker roll-off at 80 Hz, resulted in a 4th order roll-off - not coincidentally the same as the low pass filter rate imposed on the subwoofer. The final result: a 4th order high pass and 4th order low pass filter rate at the selected xo of 80 Hz and a nice neat crossover.

Unfortunately, nearly all surround speakers these days are vented, and imposing a 2nd order filter on a vented speaker results in a combined 6th order roll-off - not the same as the subwoofer.

In addition, surround speakers can have different tune points and F3 points, making it hard to determine what the combined filter/roll-off slope will look like. Using vented surround speakers with an F3 of say 50 Hz might result in a slight emphasis in the 80-60 Hz region because the vented speaker has not yet begun to naturally roll-off, and is only being artificially filtered at a 2nd order rate.

The only way to really tell what's happening at/near the xo is to run a FR sweep at the listening position. With that said, he will probably be "OK" with an F3 of 65 Hz and an 80 Hz xo, but do realize if the speaker is vented, the combined roll off below 65 Hz will be 6th order.

Regards,

Ed

 

[Mark C.]

That means you're fine with a 80Hz crossover, just like most of us are.

 

[RichardH]

Upgrade to speakers that can go lower and then use 80 Hz. Isn't that what you really want to hear ???

 

[Mike Co]

I just got the Outlaw ICBM yesterday and their rule of thumb is F3 + 10Hz, then set the xo at next step. (ie 65Hz + 10=75Hz; next step on their unit is 80Hz).

 

[PaulDA]

What happens if you set different crossovers for different speakers? Do you get phase issues or double bass problems? My fronts F3 is about 50hz, rears about 60hz centre at 70hz. If I set fronts and rears to 60 and centre to 80, will I have serious double bass problems? Not all my speakers have arrived from backorder yet, so I haven't experimented. My own understanding of the purpose of a subwoofer has always been that it should supplement the speaker. I suspect I'll be told to try it out or just go with 80hz. Just curious.

 

[Brian L]

There have been articles posted about using different vs. the same crossover points for different speaker positions. IIRC correctly, they suggest using the same settings all around, but I think there are legit arguments posted elsewhere to match the crossover to the speaker if they have different capabilities.

I thing the Secrets site had that article I am referring to, but I could be wrong.

I don't think double bass is an issue (that can happen when the BM does not work right, and sends full range to the main channel while still sending bass below the crossover to the sub), but you may have phase issues at and around the crossover region. Then again, with 5 (or 6 or 7!) speakers being crossed over, it may be impossible for the sub and each individual speaker to be in phase at the crossover when measured at the listening position, even with the same crossover setting for each speaker.

I would stick with the same setting all all around (I have speakers with similar characteristics to yours, and am an 80 hz kind of guy!), but feel free to experiment.

BGL

 

[PaulDA]

One of my concerns regards multichannel audio. With the exception of the Denon 2200/2900 (in my price range--no 5000$ player for me), all of the players appear to have crossovers fixed at 100hz. My receiver (Integra DTR 6.4) allows me to assign time delays and crossover settings to my multichannel input, but it does this by adding a layer of AD/DA processing. Will this really degrade the sound enough for my ears to tell? I don't know. I haven't plugged in a multichannel player yet. (I consider my ears to be sufficiently trained for critical listening--I've been in choirs and have fooled around in my friends home recording studio--but I would never go as far as some of the more "esoteric" audiophile reviewers I've read. They seem to have supernatural abilities far beyond those of mortal men )

For DVD-A, as it is already PCM, I doubt it will make a discernable difference. But there seems to be a reasonably serious concern over converting DSD to PCM (which is the only way that my receiver could apply the processing to SACD) and the potential loss of sound quality. Ah well, I'm sure I'll play with all the permutations (I'm like that) and go with what sounds "good enough" to me. Besides, in the end, with reasonably well-designed and built equipment, speakers are the greatest variable for quality sound and I'm quite happy with mine. Although I'm quite fascinated by all the minutiae in this hobby (moreso the audio than the video, though) sometimes I worry that I might be obsessing over things that are getting in the way of enjoying all these cds and movies, which is the goal of this hobby in the first place.
Whew, that felt good to get that off my chest. Sorry if this derailed the thread.

 

[ScottCHI]

paul, one thing to consider is that the ability to time-manage the material that comes into your pre/pro/receiver's analog multi-channel inputs is a nice feature and something that many players won't allow with sacd playback, so you may want to use it for that, depending, of course, upon which player you get, and it's sacd tm capabilities.

i think that somewhere in that thread you had started about line level vs. speaker level sub connection someone (ed?) posted a link to a good article that discussed the negative aspects of using multiple crossover points, that made a lot of sense.

 

[PaulDA]

You're right, the time management is a nice feature. I guess I just wanted to be able to use the "Pure Audio" mode that bypasses everything, to get the "unaltered" sound. (It's a bit of snobbism, I know, but I've always believed the fewer processor steps, the better, though today's stuff (my receiver included) might be good enough to override this concern.) Ultimately, I guess I have to realize the limitations of my room/speakers and deal with them accordingly.