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?

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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My head hurts!

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!!!

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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www.bickerton.co.nz

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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My head hurts!

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!

Quote Scatamonkey:

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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)

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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...

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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J90
Sonic Visions

Edited by Ed_J90 (26/02/12 04:05 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?

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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Audiophiles use phono leads because they are unbalanced people!

Quote dmills:

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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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+1 on that one...those connectors are bobbins!

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My head hurts!

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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My head hurts!

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!!!

Quote:

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

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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.

Quote grab:

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Quote:

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

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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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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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PA stuff on FB

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

Sounds to me like your crossover point on the Behringer is set too high.

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

Quote Scatamonkey:

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...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

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Unless I misunderstand you that should read 'high pass filter' or 'low cut'

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

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!

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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There's nothing we can't face... Except for bunnies

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'?

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.

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.

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!!!!!

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.

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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PA stuff on FB

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!

www.cerwinvega.com/manuals/pro/intense_manual.pdf

http://www.numark.com/images/product_downloads/dimension4_referencemanual. pdf

http://www.allen-heath.com/uk/products/pages/productdetails.aspx?CatId=ZED Series&ProductId=ZED22FX

All the data on the 3 parts of this puzzle !!!

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.



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PA stuff on FB

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!

Balanced Inputs- Connect a balanced signal through XLR input connectors. These should be used for all long cable
runs. Please note: Pin 1 Ground, Pin 2 Positive (+), Pin 3 Negative (-).

SPEAKON Output – For better contact security, use of these outputs is strongly recommended in all applications,
especially mobile systems. Do not use these outputs simultaneously with the output terminals, only alternatively. Note
the correct pin designation for the used speakon connectors: pos=1 + / neg = 1- / 2+, 2- not connected.

This is taken from the Numark manual for the amplifier.

Taken from the Cerwin Vega data sheet!

FULL RANGE MODELS (INT-152, INT-252): These models are equipped with both a 4 pin Speakon connector and two 1/4” phone jack inputs. The 4-pin Speakon connector is configured so that 1+ and 1-
and the 2+ and 2- pins both connect to the input (they are in parallel). The 1/4” phone inputs are also paralleled together, and can be used to daisy chain to another speaker (see below).

SUBWOOFER (INT-118S): This model also uses both 4 pin Speakon connectors and 1/4” phone jack inputs. As in the case of the INT-152 and the INT-252, the 1+ and the 1- of the speakon are paralleled
with the 2+, 2- inputs, so either one will work. These are also paralleled with the 1/4” phone inputs, so that it can be passed through, or daisy chained to another speaker (See below).

DAISY-CHAINING SPEAKERS: Since the INT-152 is equipped with two 1/4” input terminals that is internally connected in parallel, it is possible to daisy chain speakers by connecting the output of the power
amplifier to one 1/4” phone jack, and a second speaker system to the other phone jack. The same is true for the INT-118S.
As mentioned above, the INT-152 and INT-118S have a nominal impedance of 8ohms. Since most professional power amplifiers are designed to provide stable performance at a load impedance of 4ohms or
8ohms, Cerwin-Vega recommends that no more than two 8ohms speaker systems be daisy-chained together. This will allow the amplifier to operate properly and avoid overheating. (Since the INT-252 has a
nominal impedance of below 8ohms, it is not recommended to daisy chain.)

LIGHTBULB PROTECTION CIRCUIT: Your Intense! speaker systems are equipped with a power-limiting circuit on the compression driver, to avoid damage to the device if overdriven. If this happens, a small
flicker of light is potentially visible through the front port vents. If this happens, do not panic. What is happening is that instead of this power going directly to the compression driver (where it would potentially
damage it) it is “absorbed” by a high current light bulb, which dissipates this power by converting it into light.



It says that the speaker does have a 4 pin speakon plug like you thought, but it seems to suggest it is wired that way only to facilitate the daisy chaining of other speakers.

Oops. Well spotted!

Well, there goes that theory. Don't worry about the speakons, then.

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PA stuff on FB

Do you have access to another amp/speakers to help isolate the problem?

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

Yeah, I have a mate with a full PA in his practice room, I was talking to him about this too and this weekend I'm going to head down there and start interchanging amps and speakers and even the desk to help isolate what is going on!

Thanks again to everyone for their input!!! Balanced or otherwise!!!

Good choice.

Good luck and more (phantom) power to your elbow.

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Ohm's Law states, "Your PA isn't as powerful as you think it is".

Quote Guy Johnson:

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

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I think that picture actually shows 1- and 2- unused.

Wiring like that may on some amplifiers produce a reverse polarity effect (with the usual loss of bass)

Given the impossibility of looking at the tiny lettering and the text I included, we can assume the wiring as is said, and not add too much confusion? It was such a sexy picture, much nicer than this!



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PA stuff on FB

Some Progress!!!

I set everything up in the garage tonight again and to be honest, the speakers are not as completely bass absent as I thought. The other night I went from having the 18 bins running to not running to running again so I think my ears were exaggerating the change a bit.

So tonight, no bins at all. I started with the Behringer FBQ on and in the signal path and I think you guys are gonna shout at me after this...

When I bought these speakers the manual said they had a frequency range of 50 to 20,000HZ, so thinking I was protecting them, the first thing I did was set the low and high cut on the FBQ from 50 to 20,000. To be extra careful I also pulled the sliders on the 31 band EQ ALL the way down from 20HZ - 50HZ. (The first four at the left hand side)

Tonight I thought, "I wonder how much music is hiding down in those frequencies?" So I turned the Low Cut pot all the way off, and put all the sliders back in the middle...and low and behold, the speakers started to sound a lot bassier. My mistake and I put my hand up to it. The first 2 didn't change the sound much but I was really surprised by how much 31.5 and 40 did!

However, they still didnt sound fantastic, so I took the 1900 watt amp out of the loop and plugged a 150 watt head (which is worth about 50 quid) in instead and it definitely sounded fuller and with more bottom end. To directly compare I had one speaker running off the big amp and the other off the little one. I panned between them over a couple of songs, 2 cigarettes and much head scratching. The little cheapo amp definitely had more bass!

So my question is this, with eveything else being equal, do different amps produce different tones? Have you experienced one amp being more bottom heavy than another? Cuz I thought an amps job was just to make the signal louder...period! Not effect the sound EQ wise!!!

OK. Now take the low cut filter out of the Numark amp all together and compare the two amps with no Behringer patched in.

It's possible the Low Cut filter on the Numark is set too high.

Bob

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www.bickerton.co.nz