I can't find a review of these speakers anywhere online. I'm using Cerwin Vega Intense 252s on top and Cerwin Vega Intense 118s bins. These are powered by a pair of Numark Dimension 4 amps.

I honestly think I'm the only person whose bought them!!!!

The tops I love, been using this righ flat out for opver 3 years and never had an issue. The bass from the bins is slightly lacking. Now I'm not trying to shake anyones teeth out, but I feel fractions away from getting that low end punch that I hear in my head. I use an AKG D112 for kick and I read a lot of mised reviews. Somw love it, some people hate it. I personally find it boxy and middy sounding and that seems to be the majority sentiment.

On one DJ forum I found a few guys talking about the Numark amp, they said it is a great amp for the money, lots of features, really reliable, but doesn't seem to live up to its power figures when aske to produce bass.

And that is exactly what I thought. Just when you are getting close...you are in the red. The reason I'm on here is cause as you all know, 99% of fixing a problem...is finding the problem.

Is it a bad amp...bad bins...a bad kick mic....or a combination of all three???

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"Play one the drummer knows!"

Probably the bass amp's not powerful enough, it does about 450 watts/8 ohms and 650w into 4 ohms.

The bass bins can take 1000w peak, 500 program, according to specs, so you'd need an amp delivering 1000w -ish into 8 ohms to get the most from them ... at the moment, you're giving them 450. Don't get too excited about the extra power, twice the power is NOT twice the volume, only 3 Db.

Those 'tops' have two 15s in them, so the single 18 bins won't do much more for the bass. At 98 Db sensitivity, they are not that efficient, either. These for instance can handle 2400w peak, and are anyway twice as loud for the same power (if the specs of both makers are based on the same test, which is not likely.)

So some bigger bins, or two more of the bins you already have, with the same amps, will be good: You'd get roughly 3Db more efficiency for the same watts (twice the cone area) and also draw more current from the amps to give another couple of Db on top of that, so roughly ... a bit louder, but worth it.

Here is a good page explaining stuff.

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Let me begin by saying I am most definietley not an expert.

I try and research what I need and trial and error til I get it right.

With regards to the bins, I daisy chain two 8ohm bins..making them 4 ohm right?

The Dimension 4 amp provides 1900watts at 4 ohm in bridged mono mode...so is that simply divided between the 2 bins giving them 950 watts each ???

I remember doing these sums before I bought all this gear and they seemed reasonably matched. The tops are 4 ohm, 500 watt program 1000 watt peak, so they should be getting at least 750 watts of power instead of the 660 per channel the amp delivers. But the tops sound great and it's the bins that are lacking, even though they have an extra 290 watts each driving them???

Am I completely wrong with my workings out???

Amps and their specifications, especially at low impedance loadings, are often misleading. Maybe the amp will give it's rated power . . . but only for a few milliseconds. Have a look at some forums discussing amps, like the LAB forums.

There are a few potential pitfalls...
Make sure the polarity of the bridged amp's output is the same as the unbridged one's, relative to the + connection on your speaker boxes.
You will be running the individual amps at two ohms, effectively. Most amps don't preform well at two ohms, especially the bargain ones.
As mentioned earlier, doubling the power will only give a slight boost.

Are you crossing over the tops? If so, you'll be wasting the bass potential of those four 15s.

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"Running the individual amps at 2 ohm effectively"

I had not even considered that...I thought that daisy chaining bins to run at 4 ohm was standard practice. And that "bridging" was "combining" to make one BIG amp running at 4ohms..... not 2 amps running at 2ohm. Although that would explain why the bass amp runs so much hotter than the top amp.

To answer your crossover question, I go from an Allen & Heath ZED 22FX desk into a Behringer FBQ3102, this has 3 outs. 2 for the left and right tops and sub out for the bass bins.

I imagine it is cutting bass frequencies to the tops if I use the sub out option. Are you suggesting I should use the pass through, take a full range signal out and use the SUB option on the bass bin amp?

That raises another question, I have been using both actually, the SUB out from the FBQ and using the SUB option on the bass bin amp (a belts and braces approach I guess)

I also have a sweep on both the FBQ and the amp itself, they both go from 20 to 200HZ. On the FBQ I left it full (at 200HZ) this lets all the bass frequencies through (doesn't it?) and on the bass amp I just messed around with it til I got a sound I was happy with.

Am I doing this all arse about tit? Overall I'm very happy with the sound, just slightly lacking in low punchy bass.

As for the polarity questions....I have no idea!

I had not even considered that...I thought that daisy chaining bins to run at 4 ohm was standard practice. And that "bridging" was "combining" to make one BIG amp running at 4ohms..... not 2 amps running at 2ohm. Although that would explain why the bass amp runs so much hotter than the top amp.

> the current draw will be the equivalent of two ohms for each bridged channel.

To answer your crossover question, I go from an Allen & Heath ZED 22FX desk into a Behringer FBQ3102, this has 3 outs. 2 for the left and right tops and sub out for the bass bins.
I imagine it is cutting bass frequencies to the tops if I use the sub out option. Are you suggesting I should use the pass through, take a full range signal out and use the SUB option on the bass bin amp?

> yes, let the bass through, though I think the Behringer is doing that, anyway. You can test this by not using the subs and listening to the tops on their own. The tops are full-range devices; it would be a waste of those nice 15s not to use them for bass.

That raises another question, I have been using both actually, the SUB out from the FBQ and using the SUB option on the bass bin amp (a belts and braces approach I guess)

> Yes, just use the sub out from the Behringer. The less processing the better, generally.

I also have a sweep on both the FBQ and the amp itself, they both go from 20 to 200HZ. On the FBQ I left it full (at 200HZ) this lets all the bass frequencies through (doesn't it?) and on the bass amp I just messed around with it til I got a sound I was happy with.

> I'd start with a top frequency of about 125 Hz on the sub outs. The subs will add a bit more punch to the system, so you won't have to push the bottom-end of the speakers.
Am I doing this all arse about tit? Overall I'm very happy with the sound, just slightly lacking in low punchy bass.

> Basically the tops should sound pretty good on their own, full-range. Adding the subs will give more low-end welly, and if it's too high-bassy, you can bring the crossover down to 80 or 60 Hz. Or, use a graphic and cut 60, 80 and 100 by 3 Db or so.

As for the polarity questions....I have no idea!

> If the polarity is correct, the bass will go up when you fade up the bass-amp's send or volume controls. You could use a 50 Hz tone for this. If the volume goes down, the polarities will be fighting each-other, so reverse the banana plugs (if you use them) or get a polarity (phase) reversing XLR adapter.

And if after all this, all is correct and it's too bass-light, get two more subs...

Have fun!

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Edited by Guy Johnson (23/02/12 01:40 PM)

Guy, thanks for all the great advice, I will defintely sort the crossovers as per your advice. Use the one on the Behringer and NOT use the one on the amp at all.

I'm still a little confused about the "get 2 more bins if the bass is still a bit light"

Wouldn't a better cheaper option be just to get a beefier amp, like an EP2500? If I get 2 more bins then I would need another amp anyway to run them.

Are you generally against running things in parallel? If it were your rig would you have the speakers in stereo.

Again, I apologise if I'm just being thick about this.

Each bin is 8 ohms. Two in parallel will be 4 ohms. This is fine with one channel of your bass amp. And then two bins on the other channel.

Twice the bins will be louder, and you'll also get a little bit more with pore power pulled from the amp.
Twice the amp power into the same bins will stress them too much I suspect, see the above comments on power and volume gains.

Buying a bigger amp ... may be a good idea, but ONLY with more efficient, or more, bins. All the info is in the previous posts...

Nobody's being thick! You just need to absorb power/volume, speaker efficiency/volume and other little things like Ohm's Law etc. Nothing a bit of Googling and Wicki-ing won't solve!

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Edited by Guy Johnson (24/02/12 05:57 PM)

Guy, went out to the garage and set eveything up and played a bunch of thunpy dance music so I could try your suggestions.

First of all, kudos on the crossover settings, bins thunping a lot better now that I have brought the frequency down a bit.

However, tried running the tops by themselves - and I'm getting virtually NO bass from them at all. I tried bypassing the FBQ altogether and going from my desk straight to the amp. Now, hitting PFL and listening through the headphones the bass is properly thumping. But it is almost non existent in the speakers. Mids and tops sound clear and strong....but no bass.

Now, if I crank the low end on the channel strip up full I do get some bass....so I at least know the speakers are working. Tried both amps going to the tops with same result. Both speakers sound identical. If it was just one I would suspect a fault.

Any ideas? Are they just poor speakers?

Just to check, run some other speakers. like monitors, from the amp, and see whether they sound thin or not.

Swap amps too, just to check that there's no actual crossover in the tops amp: you never know!

I'd have thought it was unlikely to be the speakrs themselves.

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I have tried every combination of amps and leads and sources that I have, but I'm gonna take the whole rig to a friends practice room at the weekend and start swapping in his gear, different amps, speakers and desk.

I will get to the bottom of this eventually!!!

Sounds like a Plan! I'd give you a hand if I were anywhere near you.

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