Crossover Settings / Subwoofer Question

[brand]

Hi guys

I have two "stupid questions" that I'd appreciate some help with.

I'm currently running 2x RF 7 IIs, RC 64 II, 2x UPA 1, SW 115 and a Denon 2313. I did run Audyssey but ended mostly using my system for music in Direct Mode so I didn't even bother with crossover settings until now when I started to look into it. So after running Audyssey I set the 3 front speakers back to small and the crossover to 80 because I'd always read that's just what you do. Now I did search the forum and google the topic but I haven't quite found the answers I was looking for. The RF 7s go pretty low and I'm not a big fan of using subs for music listening. I have no idea if there is truth to this but I listen to a lot of electronic music and I just feel like the sub won't be able to keep up, won't be as fast and hard as the RF 7. So what do I need to think about when setting the crossover? Why wouldn't I set it at 40 or 60? What should I try to listen for when I experiment with crossover settings? 

My other question is regrarding subwoofer and wattage. I currently have a SW 115 and I'm happy with it but I haven't heard many different subs especially in my living room so I'm curious to whats out there. For example if we take the SW 115 compared to the PB13 Ultra. I understand that the Ultra seems to go a bit lower (at least on the data sheet) but what's the difference / the point of 400 vs 1000 watt? Is it comparable to using different amps with regular speakers?

I also have a Denon/Audyssey specific question but I don't know if anybody on here uses Denon AVRs or if this is the place to discuss it.

Cheers
brand

[KeithL]

Not at all stupid questions - and the first one isn't necessarily simple to answer completely.

That 80 Hz value is a sort of de-facto standard (and the one specified by THx), but isn't exactly set in stone.

The decision of what frequency to use is based on several things:

1) At frequencies above about 100 Hz, we become able to tell what direction sound is coming from, so letting a sub go much above that opens the possibility of things sounding odd because you hear stuff coming from the sub that belong somewhere else. How much this happens, and how soon, will depend on your speakers, your room, and where you put your speakers (if you have one sub behind each main front speaker, then you can go much higher). Also, a shallower crossover slope, since it allows a wider area of overlap, usually means you would want to set a lower crossover point.

2) Most speakers, especially smaller ones, have a limit on how low they can go - and how loudly. In general, asking a speaker to reproduce frequencies that are too low for it to handle well results in higher levels of distortion. Since you're pumping more power into the speaker, and not getting out more clean sound, you're using up amplifier power, heating up your speaker, and not gaining much else. In fact, you're probably causing more distortion at higher frequencies because you're overworking everything trying to force the issue. (This is why you DON'T want to use EQ to boost the low frequencies and force a speaker that really isn't capable of producing them to try.)

3) The "transition" or "crossover" area - where both speakers are reproducing a range of frequencies - can be tricky. It can be difficult to configure things so the sound transitions smoothly from the mains to the sub - and you neither hear the sound "move around" or end up with funny sounding bass. Some speakers simply "fit together" better than others. Generally, this is less noticeable at lower frequencies.

4) Many subs simply don't produce very clean or "musical" bass. For those, you really want to limit what they're doing to thumps, scrapes, and dino-stomps, and keep the music away from them. If you set the crossover very low (like 40 Hz), there isn't much music way down there, so your sub will end up doing mostly SFX. However, a really good musical sub should be able to make much more very low bass than most speakers... it really all depends on the sub.

In short, the whole point is to configure things so each speaker does what it does well, and doesn't try to do stuff beyond that. As long as your mains go pretty low, you will probably get the most musical sounding result by setting the crossover frequency at the lowest frequency where your main speakers sound good, and can play loudly with no problems or strain. (Since low frequencies tend to need more amplifier power, this will also depend on how much power you have driving them.)

As for the power of the amp in the sub, many people are convinced that "more is better", but it's really mostly irrelevant to you as an "end user". All that really matters (unless you're fanatical about your electric bill) is how the sub performs overall; there are subs with a few hundred watts inside that perform better - and sound better - than other subs with thousands of watts. (There are design tradeoffs. For example, all else being equal, a small sub that goes low will be less efficient, and so will need more power to go equally low equally loud - compared to a larger one with equal performance; a massively powerful amplifier may make the sub designer's job easier by simplifying the choice between tradeoffs, and is pretty well necessary if you insist on getting lots of very low bass from a tiny cabinet, but there are many very good subs that seem to get along fine with a few hundred watts. The difference between 400 watts and 1000 watts is about 5 dB - which isn't all that much anyway.)

 

Jun 2, 2014 22:36:15 GMT -5 brand said:

Hi guys

I have two "stupid questions" that I'd appreciate some help with.

I'm currently running 2x RF 7 IIs, RC 64 II, 2x UPA 1, SW 115 and a Denon 2313. I did run Audyssey but ended mostly using my system for music in Direct Mode so I didn't even bother with crossover settings until now when I started to look into it. So after running Audyssey I set the 3 front speakers back to small and the crossover to 80 because I'd always read that's just what you do. Now I did search the forum and google the topic but I haven't quite found the answers I was looking for. The RF 7s go pretty low and I'm not a big fan of using subs for music listening. I have no idea if there is truth to this but I listen to a lot of electronic music and I just feel like the sub won't be able to keep up, won't be as fast and hard as the RF 7. So what do I need to think about when setting the crossover? Why wouldn't I set it at 40 or 60? What should I try to listen for when I experiment with crossover settings? 

My other question is regrarding subwoofer and wattage. I currently have a SW 115 and I'm happy with it but I haven't heard many different subs especially in my living room so I'm curious to whats out there. For example if we take the SW 115 compared to the PB13 Ultra. I understand that the Ultra seems to go a bit lower (at least on the data sheet) but what's the difference / the point of 400 vs 1000 watt? Is it comparable to using different amps with regular speakers?

I also have a Denon/Audyssey specific question but I don't know if anybody on here uses Denon AVRs or if this is the place to discuss it.

Cheers
brand

[DYohn]

An additional point to add to Keith's comments. There is a difference between setting up a subwoofer for 2-channel music and setting one up for home theater. In music the idea is for the sub to seamlessly blend with the main speakers in order to reinforce the lowest two octaves which most speakers have difficulty reproducing with sufficient dbSPL. In this case the crossover (and level) is whatever might be necessary to achieve this blend. In home theater things are different, since the sub's job is to also reproduce the LFE (low frequency sound effects) channel of a cinema sound mix. LFE effects (according to Dolby and dts specs) is cut off at 120Hz. The subwoofer in an HT setup must be able to reproduce the LFE information PLUS the sub-bass information from the main channels (this is one job of the pre-pro: to provide bass management for all program channels.) In a Dolby setup, LFE can be up to +10dba above main program information, which means the subwoofer channel must be capable of twice the dbSPL output levels (10X the audio power) of the mains channels to avoid clipping. Here's a simple paper from Dolby describing this requirement: www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/38_LFE.pdf

This is one reason why designing a proper dual-use setup can be so difficult. The subwoofer has a very different job in a music system than it does in an HT system.

[brand]

Thank you both very much. Seems like I wasn't that far off with my "intuitive" thinking. Unfortunately my current AVR won't allow me to have custom crossovers for different listening modes so I'd always have to go back into the menu and set a different crossover depending on whether im listening to music or using HT. So for now I'll try to find a tradeoff crossover that works for both. I guess I'll always have sort of a trade off when trying to run a music and HT setup in the same living room.

One follow up question:

Does "must be capable of twice the dbSPL output levels (10X the audio power)" translate into "needs x times more wattage than the the amps for the normal speakers"?

[DYohn]

Jun 3, 2014 12:01:56 GMT -5 brand said:

Does "must be capable of twice the dbSPL output levels (10X the audio power)" translate into "needs x times more wattage than the the amps for the normal speakers"?

If the sensitivity is the same, yes.

[bootman]

Jun 3, 2014 12:01:56 GMT -5 brand said:

Unfortunately my current AVR won't allow me to have custom crossovers for different listening modes so I'd always have to go back into the menu and set a different crossover depending on whether im listening to music or using HT.

It is this kind of flexibility that a prepro can offer (if designed to do so) over your typical AVR.

Many times the quote of "my prepro sounds so much better than my old AVR" can just come down to the flexibility of dialing in proper settings for your particular application vs being tied to what the AVR auto eq program set them to during the setup routine.

[brand]

Jun 3, 2014 12:20:43 GMT -5 bootman said:

Jun 3, 2014 12:01:56 GMT -5 brand said:

Unfortunately my current AVR won't allow me to have custom crossovers for different listening modes so I'd always have to go back into the menu and set a different crossover depending on whether im listening to music or using HT.

It is this kind of flexibility that a prepro can offer (if designed to do so) over your typical AVR.

Many times the quote of "my prepro sounds so much better than my old AVR" can just come down to the flexibility of dialing in proper settings for your particular application vs being tied to what the AVR auto eq program set them to during the setup routine.

True but a pre pro still doesn't give me an easy way to have a different crossover for music listening and HT does it? Or am I missing the point entirely?

[bootman]

Jun 3, 2014 12:28:19 GMT -5 brand said:

Jun 3, 2014 12:20:43 GMT -5 bootman said:

It is this kind of flexibility that a prepro can offer (if designed to do so) over your typical AVR.

Many times the quote of "my prepro sounds so much better than my old AVR" can just come down to the flexibility of dialing in proper settings for your particular application vs being tied to what the AVR auto eq program set them to during the setup routine.

True but a pre pro still doesn't give me an easy way to have a different crossover for music listening and HT does it? Or am I missing the point entirely?

If your prepro would let you set LFE and each speaker's xo differently, then maybe.

or integrate a HT bypass 2ch prepro like the XSP into the mix.

[cd]

>> True but a pre pro still doesn't give me an easy way to have a different crossover for music listening and HT does it? Or am I missing the point entirely? <<

Actually, this is exactly one of the benefits of having a modern prepro. For example, my UMC-1 allows me to have 3 different EQ profiles. Any one of these can be assigned to a given Input. So, it is quite possible to have one EQ profile that would be optimized for music listening and another one for HT duties. And, since it is possible to create your own labels, you could build one Input profile called HT and another one called Music.  Then you'd simply select the Input that matched what you're listening to...

Pretty cool, huh?

CD

[brand]

Well I already own a USP 1 but I never used it in combination with my AVR because it doesn't offer full range HT bypass so I was already planning on buying a XSP anyway. I don't know why I only just now realized that the XSP will also fix the "having different crossovers" problem right?

Although I just looked at the backplate of the XSP and I'm still now sure exactly how I'll have to set it up. Would the sub be connected to the XSP or the pre out of the AVR? Lets say I wanna use the Denon/Audyssey for HT (5.1,7.1 whatever) and the XSP for 2.1. I wanna have the Denon crossover at 80 and the XSP crossover at 40 (hypothetical values). Is that possible?

EDIT: I just realised I'm mixing up pre (amps) and pre pros, I think meaning what I'm suggesting won't be possible unless I switch out the AVR for a pre/pro capable of what I'm looking for here?

[cd]

>> I think meaning what I'm suggesting won't be possible unless I switch out the AVR for a pre/pro capable of what I'm looking for here? <<

Correct. You would seem to be a perfect candidate for the XMC-1, if Emo ever releases the doggone thing. If I were you, I'd sell the USP-1 and use the funds to help purchase the XMC-1. This will give you a world-class HT/multi-channel setup as well as a world-class 2-channel setup. In addition to that, you'll also have a world-class room correction setup for both 2-channel and multi-channel listening. And you can do all of this with a single box, making for a simple and elegant do-it-all audio system...

CD

[KeithL]

Good point - and the upshot is a different set of priorities....

The highest priority for a sub for music is that it sounds "musical" - nice and clean and blends well with the music. For home theater, arguably, being able to play very low frequency special effects very loudly is a higher priority. While there's no reason why a well-designed sub can't excel at both, it's obviously going to be easier to design one that excels at either one alone.

Note, however, that you do have some leeway with those priorities. (For example, if you have a low powered sub that sounds very good with music, you CAN turn it down; even if Godzilla doesn't actually rattle the prisms on your chandelier, and you don't 100% meet the Dolby spec, it will still sound excellent with music, and not so bad with movies...) Unfortunately, if you have a sub that gets very loud, but sounds muddy or boomy with music, you're really going to want to NOT use it for music. In that case, you might consider using Direct Mode for music - and only using the sub for those "special" movies.

In general, there are a lot of subs out there that are "good enough for special effects, but not good enough for serious music listening"... especially among the lower priced ones.

Jun 3, 2014 10:01:58 GMT -5 DYohn said:

An additional point to add to Keith's comments. There is a difference between setting up a subwoofer for 2-channel music and setting one up for home theater. In music the idea is for the sub to seamlessly blend with the main speakers in order to reinforce the lowest two octaves which most speakers have difficulty reproducing with sufficient dbSPL. In this case the crossover (and level) is whatever might be necessary to achieve this blend. In home theater things are different, since the sub's job is to also reproduce the LFE (low frequency sound effects) channel of a cinema sound mix. LFE effects (according to Dolby and dts specs) is cut off at 120Hz. The subwoofer in an HT setup must be able to reproduce the LFE information PLUS the sub-bass information from the main channels (this is one job of the pre-pro: to provide bass management for all program channels.) In a Dolby setup, LFE can be up to +10dba above main program information, which means the subwoofer channel must be capable of twice the dbSPL output levels (10X the audio power) of the mains channels to avoid clipping. Here's a simple paper from Dolby describing this requirement: www.dolby.com/uploadedFiles/Assets/US/Doc/Professional/38_LFE.pdf

This is one reason why designing a proper dual-use setup can be so difficult. The subwoofer has a very different job in a music system than it does in an HT system.

[brand]

Jun 3, 2014 13:39:57 GMT -5 cd said:

>> I think meaning what I'm suggesting won't be possible unless I switch out the AVR for a pre/pro capable of what I'm looking for here? <<

Correct. You would seem to be a perfect candidate for the XMC-1, if Emo ever releases the doggone thing. If I were you, I'd sell the USP-1 and use the funds to help purchase the XMC-1. This will give you a world-class HT/multi-channel setup as well as a world-class 2-channel setup. In addition to that, you'll also have a world-class room correction setup for both 2-channel and multi-channel listening. And you can do all of this with a single box, making for a simple and elegant do-it-all audio system...

CD

USP will go into bedroom for 2nd setup anyway but I was already interested in the XMC. I'll wait for reviews when the XMC has been out for a while but this increases my interest in the product.

For now I'll run Direct Mode so no need for a separate crossover for now. 2.1 stereo sounds terrible through the "Stereo" sound mode on the Denon. I'll give 2.1 another shot once I have the XSP to see how it sounds and decide whether I want to change something in the sub department. Thanks for explaining and resolving this with me.

Plenty of punch and power with just 2.0 for now.