Why is slope never discussed wrt subwoofer integration

[tomlinmgt]

It's well established that when designing a loudspeaker with multiple drivers slope plays a critical role in how well the different drivers integrate as the transition from one to another occurs, though you rarely see anyone giving it any consideration when integrating subwoofers into the system to support main speakers. Why is that?

Sure, we can change the frequency at which the subs roll off at the plate amp, but the slope is fixed (I'm pretty sure my Dayton plate amps are fourth order) and who's to say that fixed slope is optimum for integrating with the LF driver in the mains? And then there's the slope of the main as it rolls off naturally or is filtered by a prepro or DSP. I guess with enough digging you could find out what the slope is for a prepro or DSP filter, but how do you determine slope when a speaker is just naturally rolling off. Response curve?

 

[Rob41]

That's an issue I see with plate amps in general and why I don't plan to use them.

I wish I could recall where I read it, but I just read about not only optimizing the subs slope, but having the crossover point overlap with the mids.

In the article the author recommended a shallow first order slope for both the sub and the bottom crossover of the mids. That, along with overlapping the drivers smooths out the frequencies in that range.

 

[whoaru99]

I think sealed box naturally rolls off at 12dB/oct and basic ported at 24dB/oct. Don't quote me on that because I'm just rolling from memory that sometimes ain't so good.

 

[tomlinmgt]

That's an issue I see with plate amps in general and why I don't plan to use them.

Not just plate amps, but most all of the reasonably priced active analog crossovers I've seen are fixed slope as well.

 

[Rob41]

It may be a bit less of an issue at those frequencies but I believe there is a difference. I don't have golden ears to say the least, but I can hear a difference between a very shallow vs a very steep slope.

 

[240sx4u]

I have slope adjustability and I did find that messing with it made a difference as far as how I was able to dial everything in with my OmniMic.

 

[HTWillie]

I think sealed box naturally rolls off at 12dB/oct and basic ported at 24dB/oct. Don't quote me on that because I'm just rolling from memory that sometimes ain't so good.

Those are my off-the-top-o-my-head figures as well.

I'm guessing 12dB/octave slopes are most common on powered subwoofers, because they'll either be in phase or 180 degrees out of phase with the main speakers' natural roll-off.

But does a natural roll-off more closely resemble a Butterworth filter, Linkwitz-Riley filter, or something else? Probably trivial compared to getting the phase right, followed by getting proper overlap/underlap of frequencies.

 

[Bob Orme]

If your mains need a sub, they aren't very good mains. If you need to roll off the low end of your mains, you probably didn't need a sub to begin with, other than maybe to rattle your windows or bother your neighbors. EQ's are cheap and effective.

 

[Coytee]

I agree that there isn't much chat about slopes.

I bought a pair of Danley DTS-10's to go with the Jubilee's.

(preface: I do not have any type of HT processor yet, just a tube preamp)

Although I have the DSP parameters to equalize the Danley's, I don't know where to integrate them with the Jubilee's so I just did some by ear, experimentation.

(second preface: Though I've now owned the Danley's for 2 1/2 years, I've only listened to them for about 2 hours.... currently, they're not setup)

When I had them plugged in (in a little apartment of all places!!!!), I spent about 30 minutes dialing them in. Wasn't enough.

On to what I was hearing...

They remained silent during Finding Nemo. I kept wondering about what I'd heard of the "Glass Tapping Scene".... I was becoming very unimpressed. I thought I'd seen the scene.... when a few minutes later, it happened.

"omg" it was like God opened the heavens and the entire place was being attacked with thunder and everything was vibrating. It put a smile onto my face wider than the grand canyon.


Here's where I finally discovered my problem is... First, I admit they were not very well integrated... that said.... they would lay silent and then when something that had material for them, they would SPRING to life. It was almost like 100% off or 100% on with no buildup in between to prepare you.

It was amazing what they did but it was also a bit startling.

I realized I might need to blend the slope on them in a bit better to allow them to ramp up in a more natural progression than full off or full on.

Today, wife doesn't want them in room downstairs so they're sitting in my garage, patiently waiting.

 

[tomlinmgt]

^^^

It could be slope, but more likely has to do with acoustic room modes creating standing waves that are causing weak reproduction of the frequencies between the ones that are coming on strong from the subs and the lowest ones coming from the mains.

 

[tomlinmgt]

If your mains need a sub, they aren't very good mains. If you need to roll off the low end of your mains, you probably didn't need a sub to begin with, other than maybe to rattle your windows or bother your neighbors. EQ's are cheap and effective.

No.

I can assure you I (and many others) have been down the path you suggest with mains that are indeed very good (in my case, several flagship full range designs from the vintage era and in a room with extensive acoustic treatments) and that does not guarantee flat and accurate low frequency response because room acoustics and the way they adversely affect LF reproduction simply won't allow it. And at one time I thought an EQ was the cure and actually considered it as critical a piece to have in the rig as the source component itself. Experience, experimentation, and knowledge have taken me beyond that highly compromised and flawed methodology and if you'd consider the basic science that dictates all of this you'll understand why.

Yes, at one time I thought my EQ assisted JBL, Infinity, Polk, etc. full range designs with an EQ made some pretty awesome sounding bass...but then I embraced the science, took the proper approach and realized how much I'd been missing and, frankly, screwing it all up. This could be a game changer for you, too...if you're willing to let go of your methods and beliefs. This is the other side, the next level, the place you get to and say "holy ****...I've been doing it all wrong".

Have a look at this link and you'll start to understand the concepts at play here.

http://www.audiokarma.org/forums/showthread.php?t=291904

 

[Rob41]

If your mains need a sub, they aren't very good mains. If you need to roll off the low end of your mains, you probably didn't need a sub to begin with, other than maybe to rattle your windows or bother your neighbors. EQ's are cheap and effective.

Bob, I can assure you from a technical standpoint, there are no mains in a home listening environment that can't benefit from the addition of a sub, and in particular, a distributed bass system.

While your opinion maybe valid for you subjectively, a single pair of mains in a home listening environment will have uneven room modes. It is simply unavoidable. Regardless how effective your mains may be, they do suffer from room modes. You may be fine with this and it's certainly your choice as you may be pleased with your results.

Placement of the drivers producing the lowest frequencies, woofers or sub woofers, is highly unlikely to optimal when simply placed below the other drivers as the lower frequencies behave differently due to the wave lengths.

To make a statement declaring "If your mains need a sub, they aren't very good mains" is simply incorrect. :yes:

Here is a link that goes into a bit more detail that may interest you: http://www.audiokarma.org/forums/showthread.php?t=291904

 

[tomlinmgt]

So, before anyone else decides to jump in here and try to convince me (or the other respondents who are making positive contributions to the topic) by saying "good main speakers don't need a sub", understand that this is not what this thread is about. As a matter of fact, this thread is about fine tuning the LF reproduction at a level that transcends just having a pair of full range mains and tone/controls EQ. And it's orders of magnitude beyond just plopping a single sub in the corner and fiddling with the knobs a little bit. If that's the playground where you want to hang out then great...have a good time there. But don't come over here where we've found a better place after having spent a good deal of time where you are and tell us what we should be doing or that we're wrong, wasting, time/money, etc. You're welcome to join us and we'll be happy to show you what we've discovered, but please avoid making yourself look like a jack ass by arguing against fundamental science.

 

[SleeperSupra]

I had a pair of original Carver Amazing Loudspeakers that were flat to 18 Hz and I can tell you one sub made a nice difference, later I had up to six subwoofers in the room and the difference was night and day. Their is no such thing as a full range speaker that will not benefit from a quality sub, and multiple subwoofers, when properly setup and integrated, are even better.

 

[Rob41]

Your thread makes me wonder how many subs have been ditched due to the perception of only playing one note. Standing waves, resonances, room modes and slope can all play a part.

I've been playing a bit with the slope and crossover overlap and it makes a notable difference in both the integration to my mains as well as what I consider musical. By musical I mean not just a droning thump-thump, but rather hearing the bass as the instrument that created the tones. IMO, the slope of a sub is just as critical as it is with any other driver.

 

[tomlinmgt]

Your thread makes me wonder how many subs have been ditched due to the perception of only playing one note. Standing waves, resonances, room modes and slope can all play a part.

I'm totally convinced the reasons you cite are why subwoofers carry their (undeserved) stigma.

 

[Rob41]

I'm totally convinced the reasons you cite are why subwoofers carry their (undeserved) stigma.

Until not long ago I attached a stigma to sub woofers myself. I associated them with booming, thumping bass like is so often heard in HT systems and even worse, in cars. And as you know, I'm someone who likes his bass.

 

[edwyun]

Sure, we can change the frequency at which the subs roll off at the plate amp, but the slope is fixed (I'm pretty sure my Dayton plate amps are fourth order)

Not true; there are many SWs with built in adjustable slopes.

And then there's the slope of the main as it rolls off naturally or is filtered by a prepro or DSP. I guess with enough digging you could find out what the slope is for a prepro or DSP filter, but how do you determine slope when a speaker is just naturally rolling off. Response curve?

To correct this, instead of relying on the natural roll off of your LF mains, you typically would use an active crossover to control the crossover point, slope, etc., between the LF mains and SW.

 

[edwyun]

IMO, the slope of a sub is just as critical as it is with any other driver.

Definitely. It is all one "system" from the tweeters to the SW. It's not just a simple matter of adding a SW. There should be some careful thought into how to best integrated it.

 

[dc270]

I have been fascinated with slope effect for some time now, both electronically induced and passively offered. One of my last attempts at steep slope networks was with an Ashsly Electronic two way, -24 per oct. While it did sound good, and worked well with my bi-amped speakers- I much better enjoyed that of an 18db/oct unit! I suspects it boils down to human harmonics interactions. Beyond that, I have now reverted to passive x-overs and specifically built my last speaker set with a pure 6db/oct network in mind. I enjoy this set immensely over my active, biamped sets of last!
FWIW I would look into the relationship of our mental interactions with that of various octave slopes, there are papers written about this very subject! There IS a sharpness I can detect with sharper sloped networks that leaves the music somewhat lacking for me. I am not sure if it is a concern of making a driver do something it cannot- creating overhand or ring, or just me....both?
In my corner is the shallow sloped networks, experience has told me so. I would not be averted to listening to an active multi-slope crossover unit- it may even compliment some music as well as some personal tastes!
DC