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My bar owner threatened to fire me last night. He definitely had some sort of issue other than me (his "absentee" business partner in the bar has been hanging around the bar alot lately, so that probably has something to do with it), and was in a bad mood when he arrived, but he took i out on me and decided that my bass was too loud. I cut it by 4db, and he still complained. I have a very well balanced gain structure, and do not boost the bass at all, so it was at program levels in the first place.

He was not happy until I had cut about 12 db from the bass, and my system sounded like a factory car stereo. This bar is a hip-hop crowd, so it REALLY sounded awful. The funny thing is that his main gripe was that he could feel the bass in his chest when he was on the dancefloor, to which I replied, that is exactly what I was going for!

Anyway, later in the night, I adjusted the frequency floor for my subs on my DBX Driverack up to 75hz and creeped the bass up slightly to try to salvage my mix. My subs are rated down to 40hz, but i usually cut them at about 55-60Hz just to keep them well below clip.

Who else uses a crossover on their subs, and where do you set the frequency floor for your subs?

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C Mc
KJ, FL

HPF (High Pass Filter) at 35Hz and LPF (Low Pass Filter or Crossover Frequency) somewhere between 80 and 125 Hz depending on the sublow system. Bass you feel in your chest will be in the 45 to 60Hz range, below 45 is rumble and above 60 is where it really becomes more audible.

Out of curiosity, what does your rig look like (what speakers, subs and amps are you using)?

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DJ Tony
Let It Rip Karaoke

Like Tony, my subs generally see between 80-150 hz, depending on the room and the way I need it set up. No reason to go lower than that - unless you are running a 4 or 5 way system where you are separating between sub/low/low-mid/high-mid/high.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

QSC plx 1804 amp (600 wattsx2 @ 8 ohms)
EV sx300 Mains (600 watts Program, FR of 50-20K)
2 DB Technologies Sub 12 subs (400 watts each powered, FR of 40-150)

I typically feed the subs 60Hz-125Hz and the Mains 125Hz+

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C Mc
KJ, FL

Generally you'd want the sub and mains to cross at the same point. If you you crossed your sub anywhere lower than the mains, then you are losing those frequencies in between those points - whether it will make a huge impact or not is debatable. With the SX300 i'd keep the point between 100-125 hz - wouldn't go any higher. And cross the sub at the same point as the mains - essentially, tops crossed over at 125 HP, sub crossed over at 125 LP.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

Lon I think that's what he described, however here's a problem you may want to address TopherM. Those active subs have their own built-in cross over with a cross-over point of 100Hz. So even if you're feeding it a signal up to 125Hz, you're getting significant drop-off from 100-125Hz. As Lon said you're going to want the LPF on the Sub and the HPF on the full-range cabinets to be the same frequency.

Personally, I'd avoid using a separate cross-over all together and just use those built into your subs. Run your L and R main outs from your board to your Subs and then take the Crossed-over output from your subs and run that to the inputs on your QSC amp for your EV's. If you're going to continue to use the external cross-over, set the frequency to 100Hz to match what the sub woofer is doing. Again I don't recommend this approach but I won't get into the specifics unless you really are interested.

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DJ Tony
Let It Rip Karaoke

Yep I missed that one.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

Sometimes this is true, but often it isn't. Especially with crossovers that have a peak at the crossover frequency, it is absolutely the wrong thing to do.

I believe the dB SUB12 has a 4th order LR LPF/HPF at 100Hz for the subwoofer bandpass and the XLR outputs, respectively. This type of crossover does sum to +0dB (electrically) at the crossover frequency. Whether or not that will be the case acoustically is a complex question that depends on what top boxes are in use.

Unfortunately, dB does not provide the necessary information for anyone to figure out appropriate crossover configuration for this sub with a given set of tops without actually having the subwoofer in their possession and measuring it. They do not tell you the amplifier gain. The sub is about 95dB SPL 1w/1m in half-space, though. They also do not give you a frequency response chart, so you don't know if it's got a peak around 100Hz or doesn't, etc.

Generalizing on crossover advice is certainly not going to be disastrous, but it usually won't be correct, either.

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Jeff Wheeler, moonlight DJ/KJ

120kz is what we use, I have tried crossing at lower point, ie,100kz or even 80hz. Our Chinese-made sub cab is not efficient below 50kz-60hz

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I can neither confirm nor deny ever having or knowing anything about nothing.... mrscott

That seems really low. What gives?

Ahh yes, Jeff's been reading again, book knowledge without any concept of how to translate it to the real world. Dude seriously if you're here to try and prove how much you know, save it, I doubt you're impressing anyone. What you are doing is looking the fool here because you've given absolutely no helpful advice. You've spewed a bunch of great audio engineering terminology that only a small number of folks on this board are going to understand or care about and wrapped it around what is clearly only a loose understanding of the concept you're trying to explain. Ultimately, what you've failed to do is add anything to the conversastion other than "look at what really cool books I've read lately".

The fact here is simple, he's got a set of active subs with built in cross-overs. It's not a good idea to completley complicate the scenario by introducing the characteristics of a second cross-over in the same signal path. So that leaves the OP with two options, use the internal cross-overs in his subs to handle the full signal path by feeding his amp with the High Pass output from the subs or send the full range signal to both the subs (letting them use their cross-overs) and also to his other cross-over and use the High Pass signal to drive his full range speakers. That former option is the one that pretty much every manufacturer of a active subwoofer recommends for this application and that latter option simply introduces more complexity than is required.

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DJ Tony
Let It Rip Karaoke

Tony, I would be interested to know if you don't mind because I was under the impression that an external active crossover was better

It's a really small, light-weight subwoofer. Its main feature is portability, not efficiency or maximum output.


Thanks for insulting me as I correctly point out that neither Lonman, nor anyone else who does not own that subwoofer, can correctly determine the crossover parameters for use with their top speakers; and that you can't just generalize crossover configuration and expect it to work optimally, or even well, with most speakers.

I suppose you've also considered that the subwoofer in question has non-trivial acoustic delay and phase change which will have a large impact on sound around the crossover frequency. Again, the OP has been told by erroneous forum posters to ditch his external crossover (which may have an adjustable output delay.) Does the SUB12 have any additional delay on its high-passed outputs? Who knows, but the answer is probably not.

The point of my posts on this thread is to make the OP aware that he has not received correct, or even necessarily useful, suggestions; and he may benefit from doing more research. Like, a call or email to dB Tech to request more detailed information about the product.

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Jeff Wheeler, moonlight DJ/KJ

Actually go ahead and post it here. I (with over 20 years myself and always willing to learn something new) have always been taught & worked with externals - as long as it did not conflict with an internal - ie trying to cross over higher than the internals own.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

Nope just going by 'real world' experience on the characteristics of MOST no not all subs. Remember - and anyone using a sub to begin with is a step ahead of 90 percent of everyone out there. They don't necessarily need the mathmeticians equations of why this won't work with that. I've had some pretty mismatched systems that I made sound good in both kj & LIVE situations. It's called on hands! Books are great, but actually working with stuff is better IMO! And yes, there are things that can be done against what the 'specs' specify or even recommend!


The one you arguing against is the only one that recommended 'ditching' the external crossover. Sometimes (for karaoke purposes) running the crossover with the subs own crossover is pretty much the right one. I've even ran LIVE shows with a subs own crossover - imagine that!

Seems the point of your posts are to shows what you've read and really don't have any street smarts when it comes to sound. There are times rules need to be broken!

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

No Jeff, I'm not insulting you, just calling a spade a spade (I'll leave the insulting you to the guys over at the Pro Sound Web forums). You do this on this forum all the time, you post a bunch of crap about concepts that your own description makes it clear you only have a loose understanding of and then to top it off you offer no solutions whatsoever (most likely because you don't understand enough real world application of the concepts you're struggling to master to even begin to fathom an appropriate response). You continue to over think things which again is a demonstration of someone who has little to no real world application experience.

Specific to this application, we've been down this road before. The linear phase issues introduced through the use of a Linkwitz-Riley crossover are so insignificant in terms of actual audibility that they warrant little consideration, least of all in the practical setting of a mobile PA rig where simplicity is key and few have the time to do multi-point room analysis and loud speaker system design. Especially dealing with sub-low in a short throw environment like we're talking about here, the effects of time alignment again are so minor that few real world audio engineers are going to consider trying to compensate through crossover delay. Also consider that by using the internal crossover, much of this has already be accounted for. Sure not perfect because it wasn't designed with these specific boxes in mind, however far closer than one would get trying to set an external crossover, especially in the absence of mapping software and real time analyzers.

So again Jeff, get your head out of the books, articles and other crap you've been reading and try returning to the real world. We're not setting up a 15,000 seat amphitheater with line arrays and wave formed sub-low arrays where we have a full day to analyze and configure. We're trying to fill a club with sound using a reasonable but limited set of hardware that must be installed in the best possible configuration within a very short timeframe.

So no, you didn't correctly point out anything, what you did was demonstrate why it is that you're taking extremely low paying charity gigs and undercutting as a way to try and build your business. Get out and work with (not talk to on the PSW forum) real people in real life situations, it would be a major learning experience for you. Stop trying to impress folks with your vast knowledge and figure out how to live in the real world.

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DJ Tony
Let It Rip Karaoke

To TopherM and Lon:

I'm not sure I would ever generalize that an external cross-over is better than an internal, you'd really have to compare the two. Often times an external cross-over will have capabilities that a crossover network built into an active speaker doesn't have so I guess you could say it would be better.

However, the issue comes from cascading two crossovers (your external and the internal). The key to a Linkwitz-Riley (L-R) crossover is the flat response of the summed signals (both the High and Low pass) across the crossover point. Crossovers work by attenuating the signal at frequencies above or below the crossover point. This is not a hard wall but rather a roll-off. In terms of a 4th order crossover like that in your DB subs, the level is attenuated 24dB per octave (meaning that one octave above the crossover point, the low frequency signal is 24dB at two octaves away it's -48, etc).

So when an L-R crossover is designed it is done so that the frequency response curves of the high and low pass signals intersect at -6dB. This means that the sum of the two will then be 0dB giving you that flat response at all frequencies across the crossover point. The problem is if you now cascade a second L-R crossover ahead of the chain, it too performs the same functions. So now instead of the 24dB per octave rolloff, your sub-low signal that is cascaded through two crossovers is now being attenuated twice completely destroying that flat response and resulting in a significant dip at and just below the crossover frequency. You can make some corrections for this with the external cross-over but there will always be either a dip or peak in response since the two slopes rise at different rates.

Here's a good graph I was able to find that shows the different response curves for different classifications of crossover.

http://www.rane.com/n160fig5.gif

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DJ Tony
Let It Rip Karaoke

This is wrong. While the acoustic delay of the SUB12 is unknown to all of us, as is any make-up delay on its high-passed output; it could easily be significant enough to cause cancellation near and especially slightly above the crossover frequency. This is exactly the reason that products like the DriveRack PA include a delay buffer on the outputs.


He certainly won't get the "best possible configuration" by adopting "general" advice that is so often dispensed as correct on this forum.


I don't see anyone except you insulting me or my work. I don't know what your problem is, but I suggest you deal with it in some other way. There is a pretty big difference between me saying that someone's suggestion is wrong, and you coming out with a childish, personal attack. One can benefit readers and us; the other cannot.

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Jeff Wheeler, moonlight DJ/KJ

Hmmm, interesting stuff, not sure I understand much except the part where you say cascading two crossovers...but the rest is very technical and I couldn't debate or comment.

I need to see what this mean in the real world though, so I'll run some test and will post my results, I probably could have saved $200.00 just by using my sub's crossover

Cancellation will happen in any system where non-coincident drivers are used. It doesn't matter what crossover you use or what delays you set. Time alignment affects the pattern of the cancellation and peaking axis.



He'll get the best possible configuration given the constraints he's working within. Using your lack of advice, he would be left with no choice but to just give up. We've given him something that will work and produce a reasonable level of quality, you've given him nothing but inaccurate "this doesn't work" surrounded by concepts you have demonstrated you don't fully understand.

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How is this a personal attack? It was you who told us in another thread that this is how you get production work (and I'm not even going into the statements you've made on another board). Calling out facts is not insulting, it may hurt when the truth hits close to home but it's not a personal attack.

What's my problem? It's guys like you who come into a thread like this, where a couple good solid answers have been given and start calling out everyone as wrong but then not only can you not justify your position with any actual facts, you don't offer an alternative solution. You continually demonstrate by your own statements the lack of practical knowledge you have in this area. Sure, you've got the book smarts you've obviously read a lot and memorized plenty of theory and concepts but when it comes to how those concepts actually apply to the real world scenarios we face, you don't have any answers.

It is not uncommon for guys to get in your position. You want so badly to learn this stuff that you stuff yourself full of theory and advanced concepts (that generally you don't grasp completely) while ignoring the basics that actually get the job done. There's nothing wrong with building that knowledge but you have to learn how to use it appropriately. I can't tell you how many young bucks come in to a gig raving about our PA and spouting all the specs at us (like we didn't know them already) but look at me like a lost dog when I remind them that "Yeah, and it sounds freakin' great too". This is the trap you're in right now. You're so caught up in what the books say that you're forgetting the basic concept of what we're here for.

I'll be the first to say, you've probably read a ton more on these topics than I ever will. However, when it comes to putting it into play you're still a bench warmer. I don't have problems with guys who have little experience and are excited about building some, but you don't get there by reading specs and theory alone. That's what colleges like Berkley are for. You get experience by working with others who have it and seeing how they handle these common situations. So take a pill or drink a beer or whatever you need to relax and admit to yourself that you don't know as much as you wish you did and stop putting on the act. Accept that you have plenty that you can learn from EVERYONE else on this forum (as we all do) and just enjoy that journey.

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DJ Tony
Let It Rip Karaoke