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Where is the Bass???

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Where is the Bass???

Postby Scatamonkey » Sat Feb 25, 2012 7:49 pm

I took the advice of Guy on another post. I have a pair of Cerwin Vega Intense 252s and a pair of Cerwin Vega Intense 118s and in an effort to try and get a bit more bass for the kick Guy suggested I rely more on the tops as well as the bins.

So today I set eveything up in the garage and put some thumpy dance music on to experiment with. I found that even though it was thumping bass in my headphones when I had JUST the 252s on there was virtually NO bass at all.

The signal is coming from an Allen & Heath ZED 22FX desk, into a Behringer FBQ3102 and then to a Numark Dimension 4 amp.

I tried it with the FBQ, then I bypassed it altogether and went straight to the amp. The mids and highs are clear and strong but almost no bass at all. I can induce some bass by cranking the low EQ on the channel strip up full so I at least know the bottom 15s are connected, but now the sound is awful in the headphones.

I have another Dimension 4 running the bins so I tried that to and same result. Both speakers sounsd the same. Almost as is there was a low pass filter on robbing all the bass frequencies from the signal. And these are full range speakers that go from 50 - 20,000HZ.

Are they broke? Are they just rubbish speakers? Or am I just doing something wrong?
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Re: Where is the Bass???

Postby turbodave » Sat Feb 25, 2012 8:20 pm

Hi, without going into a protracted diatribe regarding equipment and its relative merits...if you think bass heavy headphones and bass light speakers you may find the answer. Try different headphones and see, if the problem persists try another environment. There are so many variables that the very last one considered should be equipment failure. Dave
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Re: Where is the Bass???

Postby Scatamonkey » Sat Feb 25, 2012 8:32 pm

Headphones are a pair of 20 quid Philips jobbies. Not particularly bass heavy at all. And the speakers have two 15" drivers and a horn. I would expect them to be bass heavy.

To clarify though, in the headphones I am hearing a full range signal, exactly what I would expect to hear, but from the speakers I am hearing only mids and highs but no bass. Like I said it sounds like someone has sneaked a low pass filter in there somewhere.

I have to crank the low EQ up full to even get anywhere near a normal sounding full range signal.

There isn't anything on the desk that I could have missed is there??? There is a low pass on every channel but if that button was in or faulty I would hear it in the headphones too wouldn't I?

I'm gonna pull all that gear out again tomorrow!!!
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Re: Where is the Bass???

Postby Bob Bickerton » Sat Feb 25, 2012 10:27 pm

Presumably when you run the 252s and 118s together, you have a crossover somewhere between the mixer and the speakers. Sounds like its still switched in when you're running the 252s on their own.

Bob
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Re: Where is the Bass???

Postby turbodave » Sun Feb 26, 2012 12:43 am

Try your speaker polarity on the 15s..it may be that you have red /black on one and black/red on the other, which would thin out the sound somewhat. Dave
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Re: Where is the Bass???

Postby Scatamonkey » Sun Feb 26, 2012 4:18 am

Bob - I normally use a Behringer FBQ to give a sub out to the bass amp. It 'should' still give a full range signal to the top amp. However just to be sure I bypassed it altogether and went straight from the desk to the amp. No other crossovers present.

Dave - I use speakons, I have heard that running 2 speakers together with one at the wrong polarity will induce some noise cancellation. But again, I tried one speaker at a time, then both together, different speaker leads, then swapped to the other amp. Always the same sound, very clear and strong but with absolutely no bass.

I tried looking at the manuals for the amps and the speakers in case the output of the amp was at one polarity and the input of the speaker at another but I'm not sure how to check this. They both say 1+ and 1-. I think they're matched but I'm not 100% certain.

I should really check the polarity from the desk to the Behringer to the amp AND to the speaker. What am I looking for though in the manuals just in case the polarity is getting reversed somewhere along the way. And if it was....would that be the cause of a bassless signal????

Thanks again guys for your patience!
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Re: Where is the Bass???

Postby Mike Stranks » Sun Feb 26, 2012 9:06 am

Scatamonkey wrote:I should really check the polarity from the desk to the Behringer to the amp AND to the speaker. What am I looking for though in the manuals just in case the polarity is getting reversed somewhere along the way. And if it was....would that be the cause of a bassless signal????(empahisis added by M Stranks)
No; only if you end up with the signal at one speaker being at the inverse polarity ("out of phase") to the other and both are running at the same time. (If you think this may be a factor - and your comments suggest that it isn't - then you should be able easily to find a CD or downloads of test-tones and phase-tests etc which will enable you to check this.)

I replied to your post last night, but ended-up deleting it....

I wonder if your perception of 'bass' is what's at the root of this? Are you looking for the "oof!" factor as the bass hits you in the chest or gives an almighty thump? I've been in venues when I've thought the bass sound was very tasty and well-balanced and someone else has strolled by and commented that they "always knew those speakers weren't much good - no bass at all." Subsequent conversation and demonstration of their home system revealed their "hifi" had 15-inch woofers which were set to give trouser-flapping bass. Sounded very unnatural to me, but to him it was normal.

No offence intended... just a thought...
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Re: Where is the Bass???

Postby Ed_J90 » Sun Feb 26, 2012 4:02 pm

Sounds like a phase issue to me too, unplug one bin and see if you get some low end back.

Also where are you crossing over? if there is too much info getting into the bins they wont be as efficient.

Edit: sorry didnt read your 2nd post so ignore top part

Also realise what you have and what they are capable of....
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Re: Where is the Bass???

Postby Scatamonkey » Sun Feb 26, 2012 6:26 pm

I spent about 2 hours reading up on phasing and polarities last night. Your right, this would only be an issue if the speakers were wired opposite each other. I dont think this is the case.

Also, this isn't an issue with the bins, but with the full range tops I have. They have 2 15" drivers and a high range horn. Which should be capable of providing a decent amount of bass all by themselves. I'm not after trouser flapping bass. Just a full range signal.

When I say there is no bass...I mean absolutely NO bass. You have to put your ear right against the bottom 15 just to hear anything, but like I said, cranking the bass EQ on the channel strip all the up gets it closer to normal.

This was all just in my garage at fairly low volumes. Is it a power issue? If I increased the volume would the bass start to come in by itself?

I was thinking that maybe the internal crossover was faulty, but normally that would be more present in the horn wouldn't it?
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Re: Where is the Bass???

Postby dmills » Sun Feb 26, 2012 6:54 pm

Daft thought, but by any chance are you getting the music into the system via some sort of lead plugged into the headphone socket on a portable music player?

If so, does this lead look something like a 3.5mm mini jack to a single 1/4 inch jack plugged into a line input?

That does NOT work and will sound VERY thin, because the line input socket is usually not stereo but balanced and that results in the system producing only the difference between the two stereo channels.

If pulling the input jack out slightly makes things come right (possibly in mono, but better) then you just need a different input lead that is wired correctly for this application.

Regards, Dan.
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Re: Where is the Bass???

Postby turbodave » Sun Feb 26, 2012 10:37 pm

dmills wrote:Daft thought, but by any chance are you getting the music into the system via some sort of lead plugged into the headphone socket on a portable music player?

If so, does this lead look something like a 3.5mm mini jack to a single 1/4 inch jack plugged into a line input?

That does NOT work and will sound VERY thin, because the line input socket is usually not stereo but balanced and that results in the system producing only the difference between the two stereo channels.

If pulling the input jack out slightly makes things come right (possibly in mono, but better) then you just need a different input lead that is wired correctly for this application.

Regards, Dan.

+1 on that one...those connectors are bobbins!
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Re: Where is the Bass???

Postby turbodave » Sun Feb 26, 2012 10:43 pm

OK..if you wanna get to the bottom of it then plug in the most basic configuration and disconnect the top end. Listen to what you have and if you are not getting anything , look at connections and if they are good , look to replace your drivers...if all other avenues have been attempted. Dave
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Re: Where is the Bass???

Postby Scatamonkey » Mon Feb 27, 2012 10:23 am

Interesting, I was using a Sony MP3 player with a mini jack to two 1/4 jacks plugged into 2 mono channels. If I DO turn the Bass bins on there seems to be a normal full range signal with plenty of bass. Using bins and tops together sound great, but there doesnt seem to be bass going to the tops at all.

I am going to head down to a friends practice room at the weekend and experiment with different speakers, different leads, even a different desk. Every possible combination I can think of to get to the bottom of this.

Thanks again to everyone for your advice!!!
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Re: Where is the Bass???

Postby grab » Mon Feb 27, 2012 12:16 pm

but there doesnt seem to be bass going to the tops at all


If you're using the sub out from the FBQ (or any other crossover), that's the idea.

What you said earlier about "full-range going to the tops" is wrong. The idea is that the tops *ONLY* get the frequencies that the subs aren't doing. So you set your crossover to 100Hz, you can forget about any bass from the tops.

This is the whole point of it. Delivering bass takes a lot of oomph, so you give that to the subs to deal with. Meantime you've now got a whole lot more power free for mids and highs, bcos your tops are not having to do bass.
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Re: Where is the Bass???

Postby Guy Johnson » Mon Feb 27, 2012 1:10 pm

grab wrote:
but there doesnt seem to be bass going to the tops at all


If you're using the sub out from the FBQ (or any other crossover), that's the idea.

What you said earlier about "full-range going to the tops" is wrong. The idea is that the tops *ONLY* get the frequencies that the subs aren't doing. So you set your crossover to 100Hz, you can forget about any bass from the tops.

This is the whole point of it. Delivering bass takes a lot of oomph, so you give that to the subs to deal with. Meantime you've now got a whole lot more power free for mids and highs, bcos your tops are not having to do bass.

Actually this is only correct if the tops cannot handle much bass!
With the 'tops' in question having two 15 inch drivers, they are fullrange boxes, and can deal with low frequencies. And deliberately not using those 15s in the OPs context is plain wrong—if you want a decent amount of bass.

MAny people don't seem to realise that the 'crossover' is only part of crossing-over ... There is always the physical crossover of the natural steep bass roll-off in any ported system. The added subs can then, if they go low enough, add the lowest lows, or can just add to the power of the combined system. In which case, the use of a shelf filter or a graphic can be used to lower everything by 2 or 3 DBs, under the mid-low crossover point on the OPs 'tops', to cater for the extra low frequency drivers.

Note ... Almost all subs* must have a low-pass electronic filter on them to prevent the higher frequencies from ruining the sound and polar patterns of the PA as a whole, and from needlessly over-heating the sub driver(s).

* Some subs are of the band-pass variety, and can be fed a fullrange signal; there are a few nice small systems that use these physical crossovers; the bass roll-off of the top speakers, and the rol-loff of all but the bass notes when using a bandpass bin, saving the unnecessary cost and complexity of extra amp channels and electronic crossovers.

There's some great textbooks which clear up the whole murky and fascinating business of speaker design, integration and system radiation patterns, which I've only lightly touched on, and which I must dig out again!
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Re: Where is the Bass???

Postby sulk » Mon Feb 27, 2012 1:14 pm

Couldn't help notice your post. You are correct to overlap your sub with your main cabs. Only cut bass to your tops if they are not capable of producing bass on their own.(such as mid horns) Also you would be making big reflex cabs act as open back cabs as the XO point would be above tuning and your overall sound would be too dry and crap. If you didn't know that already -regards
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Re: Where is the Bass???

Postby shufflebeat » Mon Feb 27, 2012 2:11 pm

Sounds to me like your crossover point on the Behringer is set too high.
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Re: Where is the Bass???

Postby shufflebeat » Mon Feb 27, 2012 2:16 pm

Scatamonkey wrote:...I am hearing only mids and highs but no bass. Like I said it sounds like someone has sneaked a low pass filter in there somewhere.

...There is a low pass on every channel


Unless I misunderstand you that should read 'high pass filter' or 'low cut'
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Re: Where is the Bass???

Postby Scatamonkey » Mon Feb 27, 2012 2:55 pm

The Behringer crossover was the first thing I checked. The last thing I did was take it out of the loop altogether.

So it's just Desk (A&H ZED22FX) going to amp (Numark Dimension 4) and then to speakers!

This is the simplest setup I can have and still produce sound, the speakers are 2-way full range and have two 15" drivers and a horn. So SHOULD produce a full range signal with plenty of bass.

To clarify, there were NO crossovers present during the final setup!

Other than whatever Cerwin Vega pass-through circuit boards are built into the cab.

Hitting the PFL switch and listening to the music through the headphones confirms a full clear signal with the channel strip completely flat.

Listening to the same source through the speakers sounds like it is only mids and highs, clear and strong but completely bassless. I can get some bass but only by cranking the Low EQ ALL the way up.


Hence the confusion!
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Re: Where is the Bass???

Postby Sheriton » Mon Feb 27, 2012 3:03 pm

Do you have access to a smartphone that can run a freebie spectrum analyser app? Whilst not exactly a high-end measurement tool, it should give you some idea of the frequency below which the bass is dropping off. In my mind, from your description, it's 200-300Hz, indicating a definite problem. If it's actually ~80Hz, that's perhaps just the way those cabs act. Without being able to actually hear what's going on, it's almost impossible to diagnose "no bass".
You'll also need a source of pink noise (another smartphone / laptop / test CD etc.)
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Re: Where is the Bass???

Postby Mike Stranks » Mon Feb 27, 2012 4:37 pm

So let's think about the amp and its connections...

What leads are you using from the mixer to the amp - XLR-XLR or XLR-jack? If XLR-jack did you make them or buy them?

You're using the speakon connectors designated CH-A and CH-B? If not, what?

None of the 'Sub', 'Mono' or 'Bridge' LEDs on the front is lit?

None of the DIP switches is 'on'?
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Re: Where is the Bass???

Postby grab » Mon Feb 27, 2012 5:10 pm

Can you confirm how you've connected the subs and tops to the amp?

First problem is that many passive subs have a built-in passive crossover. You can normally parallel up tops on either Speakon. But for these subs, one Speakon will take in the full-range input, and the other Speakon will spit out a top-only signal. So if you stick the amp output into the crossover-output Speakon, you're putting everything through this filter and things are going to go rather strange. I can't quickly find a manual for the sub, but it's very common to see this. Some subs have a switch to turn this off, but some don't.

Also think about the amp outputs. Ideally you probably want four separate amp channels, one for each speaker. If you only have two amp channels, you might want to run in mono, with one amp channel driving the tops and the other driving the subs. If your sub has a built-in crossover then you can have one amp channel running the sub and top on one side - but unless the sub/top sensitivities (and impedances!) match up then you're likely to not get a nice even response. You can try to frig around it with EQ, but honestly it's better just to drive the tops and subs from separate channels and be able to properly control their relative levels. If you've got two Numark amps then of course you're sorted for this.
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Re: Where is the Bass???

Postby Scatamonkey » Mon Feb 27, 2012 5:51 pm

Grab

My normal setup is one amp in stereo powering a top off each channel, then the other amp in bridged mono powering the two subs daisy chained together. With both amps and all 4 speakers together the sound is great, full and rich but maybe just slighly lacking in bottom end punch.

However something Guy mentioned in another post about the sound the tops were producing on their OWN started this thread off.

The problem is only with the full range tops, they are Cerwin Vega Intense 252's, about 4 foot tall and with two 15" drivers and a horn.
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Re: Where is the Bass???

Postby Scatamonkey » Mon Feb 27, 2012 6:01 pm

Desk to the amps - XLR to XLR - 1 meter - bought them.

Using Speakon channels A & B out of the amp.

I think I have all the Dip switches on, Low cut, 50 HZ cut and the Limiter.


[ ****** ]!....Low cut!, how low is the low cut though??? I thought it would be under 50 Hz or so! Right, I'm off to investigate how low is low !!!!! Cuz if its everything under 200HZ or so then that's the problem solved!!!!!
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Re: Where is the Bass???

Postby Scatamonkey » Mon Feb 27, 2012 6:11 pm

2-5: LOW CUT FILTER
The low-cut filter removes ultra-low frequencies from the audio signal. Most amplifier power is consumed by low
frequencies and most speaker woofer damage is caused by them. Activating this switch ensures that more power
can go to the middle frequencies and there is less chance for audio clipping.

3-4: 50HZ/30HZ roll off
If low cut filtering is activated, then the roll off frequency should be determined. At 30Hz, all audio below 30Hz will
be removed, at 50Hz more audio will be removed because all audio below 50Hz will be removed.

I do have this activated, set at 50HZ roll Off as the speakers have an operating range of 50HZ to 20,000HZ.
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Re: Where is the Bass???

Postby Guy Johnson » Mon Feb 27, 2012 6:59 pm

I would set the cut at 30.

As for the main speakers, they may need the XLR to be connected 1+ and 2+ linked, and 1- and 2- linked. They'd do that to allow the speakers to be bi-amped perhaps. So if that's the case, and your XLR is only a two-way one rather than a 4-way one, then you'd only be connecting to the top/mid part of the crossover.

Maybe. But you said earlier that there was a small amount of noise from the 15s.

There is bugger all tech info on the Cerwin Vega website. So maybe you can unscrew the connector plate or a 15, and check the internal connections.

Also you can do a battery test, an A size 1.5v battery across the terminals (make a test XLR; always useful to have) and see if the cones move. Should move outwards when + is connected to the red wire, which should be connected to 1 and 2+, and the black wire to 1 and 2- .
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Re: Where is the Bass???

Postby Scatamonkey » Tue Feb 28, 2012 10:09 am

Slightly confused Guy,

I have XLR leads connecting the desk to the amps, but then I have Speakons connecting the amps to the speakers.

Is it the XLRs or the speakons you think might be wired 2 way instead of 4 way.

I will look for technical data for you, I did find a data sheet before but it was well hidden!
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Re: Where is the Bass???

Postby Guy Johnson » Tue Feb 28, 2012 11:51 am

Yes, I've seen that PDF there's not a lot of detailed info in that PDF ... such as rear views, diagrams etc.
Again, the amp PDF doesn't reveal what the dip-switch settings are. Ho-hum.

Anyway, Speakon connectors for speakers ... This shows the two-pole connetions I mentioned. You can see the unused 2+ and 2- connectors.

Image
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Re: Where is the Bass???

Postby Scatamonkey » Tue Feb 28, 2012 12:15 pm

So If my speakons are like this, what should I do with them? Buy 4 core speakons?

Also the dip switchs do the follwing

1 & 6 to activate the limiter
2 & 5 to activate Low Cut
3 & 4 to select between 30HZ and 50HZ low cut once activated.

I really wish all XLR and speakon connections were standardised, then this wouldn't even be an issue!
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