Chain Gang

[Splosh 0]

Afternoon peeps...... http://www.dj-forum.co.uk/html//emoticons/biggrin.gif

 

After much grunting and groaning, I am coming round to the fact that my new amp is just not powerful enough for what I want..... http://www.dj-forum.co.uk/html//emoticons/sad.gif

 

So..... I am going to buy another, but I have seen in the past amps that are chained together to bring about a bit more umph!!!! http://www.dj-forum.co.uk/html//emoticons/excl.gif

 

Simple question really, how is this done???

 

I have a Peavey 900 amp, and I think I am going to also buy a Peavey 1500.

 

How do I connect them?

Will I get feedback?

Will I get significant boost in umph?

Will I get time delay???

 

 

Would be very grateful for answers... I have never really bothered to learn about amps before, and with all this new gear, I am really struggling with some of the techy stuff. http://www.dj-forum.co.uk/html//emoticons/omg.gif

 

Cheers Gang

 

Splosh

2J's Roadshow

[RobbieD 0]

Can you make it a bit clearer what you are trying to do?

 

Do you intend to use an extra amp to power some extra speakers?

 

If so are both sets of speakers the same?

 

However, depending on what you want to achieve, your system may benefit more from adding subs (speakers that only produce bass) rather than adding more full range speakers.

 

If you are adding subs, you will need a crossover.

 

Or do you intend to use two amps to drive your existing two speakers?

 

You can do this by "bridging" each amp, effectively turning each stereo amp in to a higher power mono amp. But if you are doing this, it makes sense to use two identical amps, otherwise the left and right channels will not match.

 

If you can give more specific information, I'm sure the members here will be able to help.

[Splosh 0]

QUOTE

Do you intend to use an extra amp to power some extra speakers? If so are both sets of speakers the same?

 

Yes and No!!! http://www.dj-forum.co.uk/html//emoticons/huh.gif

I have:

 

2 x Peavey Pro Messenger Prosubs (250 Watts RMS continuous, 500 Watts program, 1000 Watts peak 4 Ohms)

2 x Peavey Pr 12's (200 Watts RMS continuous, 400 Watts program, 800 Watts peak 4 Ohms)

 

This is run off a Peavey 900 Amplifier..... I feel that this is not enough, so........ I was thinking of buying two more speakers (likely to be Peavey PV215's - yes the American Ones - that are 350w RMS Continuous, 700 Program and 1400 Peak), and also a Peavey 1500 Amplifier....

 

My bright (or not so bright as it may be) idea was to chain the amps together and run the Bin and Pro 12's off of one amp and the PV215's off the other...

 

Am I getting my knockers into a game of twister, or can (as I am led to belive) this be done???

 

I hope this is a bit more info, and that someone can assist me in getting to the best soloution!!!!!

 

Cheers Peeps

 

Splosh

2J's Roadshow

 

 

(It all used to be soooo easy) http://www.dj-forum.co.uk/html//emoticons/wacko.gif

[Andy Westcott 0]

I'm confused by the statement "My idea was to chain the amps together and run the Bin and Pro 12's off of one amp and the PV215's off the other".

No need to chain, surely?

 

I would suggest using an active crossover feeding the 2 amps, and use the P1500 amp, or one similar, to power a decent pair of 600w RMS bass bins, and your existing P900 to power your existing mid-tops.

 

A bi-amplified system like this can run deceptively loud, as the mid-top units don't have to handle the bass, where most of the power goes, and any distortion on the bass channels won't modulate the mid-top channel, as it is independent.

 

I run a total of 1kW, 300W RMS to each bass bin, and 200W RMS to each mid-top unit. That's four amps in total, 2 stereo pairs. This is not a lot of power compared to some rigs, but due to the bi-amping benefits, sounds louder than a single 1KW amp would, and is absolutely fine for what I do.

 

Regarding 'chaining' or bridging, to give it the correct name, don't do it unless you know exactly what you are doing. The power increases can be considerable, possibly taking out your speakers, but more importantly it will probably damage the amps.

 

If you must bridge, look for amps which are capable of feeding a 2 ohm load - the QSC range are worth a look.

[Splosh 0]

But I thought that was the beauty of the Peavey subs that I have......

 

The bass bins send the mid and top out but keep the low end for itself......

It's an inbuilt cross over.....

 

Or am i completely confused????

 

Splosh

[norty303 0]

Basically you can't 'chain' amps together to get a single higher output. If you want to use the internal crossovers then you'll need 1 single bigger amp or 2 separate amps (bridged, each one feeding one sub and top - both MUST be capable of running at 2ohms stereo and 4ohms bridged)

 

You cannot feed the outputs of one amp into the other to get a combined larger output.

 

You could use one amp directly into the subs and another directly into the tops and make use of the low pass filter in the subs however I would advocate use of an active crossover in this case. The problem is that the tops don't have a high pass filter which means that both subs and tops will play bass frequencies and you could experience phase issues such as cancellation or exessive boominess.

[superstardeejay 0]

Your PV900 is a pretty good amp, very similar to the QSC RMX series, they have built-in electronic crossovers as you probably know. (those semi-recessed pushbuttons on the rear will configure them). That means that you can slave an additional (peavey or otherwise) amp off the peavey crossover outputs. The PV900 can be the master amp (ie the one connected back to your mixer) and it will split the bass and high frequencies for you to send to, say, a bass amplifier.

 

The PV900 and its larger sisters will also run into 2 ohms per channel stereo.

 

 

[RobbieD 0]

QUOTE (Splosh @ Oct 27 2005, 12:28 AM)

But I thought that was the beauty of the Peavey subs that I have...... The bass bins send the mid and top out but keep the low end for itself...... It's an inbuilt cross over..... Or am i completely confused???? Splosh

The problem with the speakers built-in passive crossover is that you are splitting each channels power output between the sub, and the top.

 

By going for an active crossover, and extra amp, you can drive each speaker with the full power of an amplifiers output, rather than only part of the power.

 

Also (with an active crossover) a song with heavy bass, wouldn't affect the power available to the tops, keeping the vocals clear and clean. Where as with your current set up, heavy bass reduces the head room available for the tops as both are "sharing" power from one channel.

 

I've tried to explain this in very simple terms, but this article on the Peavey site gives a more accurate explanation:

http://www.peavey.com/support/technotes/po...biamptriamp.cfm

 

My experience when I first went active, after using passive crossovers in subs, was that not only did the system go much louder, but the sound quality increased dramatically as well.

 

As Superstar mentions that your amp has a built in crossover, all you need is another amp (although a separate active crossover would give more control). I wouldn't bother with extra speakers until you have tried this.

 

PS: Although the amp is 2ohm capable, I wouldn't recommend long term operation in to a 2ohm load. It's best to think of it as for emergency use only - ie. if one amp goes down, then the remaining one would be capable of running all the speakers at 2ohm.

[Andy Westcott 0]

I would agree with that - if possible, don't run the amps with the minimum recommended load. This will mean you get a lower maximum power output, but reliability will be enhanced by a huge amount as the amps will have an easy time of it.

[norty303 0]

I run my rig 4 way active (soon to be 5 way with the addition of supertweeters) and the difference in level and quality obtainable is unbelieveable. It also means that i can tailor my crossover points to the drivers i'm using and how their characteristics affect the sound.

 

When i'm running vocals i drop the crossover frequencies of the compression drivers so more of the vocals come from them for a crisper cleaner sound. With heavy dance it goes the other way (higher) to allow much higher power handling (less excursion on the diaphrams).

 

 

[superstardeejay 0]

Mm, well sort of, but the 2 ohm capacity of some amps reflects the circuits capability to provide the extra current. They will already have headroom designed-in to run safely at 2-ohm....at least in a quality amp like the Peavey we're talking about. They're much less likely to clip for a given sound pressure level, since you're getting more wattage developed without having to push out the full amplifier voltage...amps clip when the speaker voltage gets too close to the power supply DC Bus volts.

 

Turning up an amp increases the output voltage (and current follows depending on frequency..). Loading an amp down with more speakers only increases the current and does not necessitate higher gain/voltage for equivalent SPL's.

 

Just to complicate matters the PV900 has DDT which is a peavey feature to prevent overdriving, clipping and overheating due to misuse!

 

I know thats getting technical but thats the way they work.

 

 

 

 

[norty303 0]

QUOTE

They're much less likely to clip for a given sound pressure level,

 

To achieve a certain SPL you require a certain amount of power.

 

If an amp is loaded to 4R and is capable of 1000w at this load then it will clip at a certain point.

 

If you take an amp that is capable of giving 1000w into a 4R load but is also capable of driving 2R loads it will still clip at the same point as the previous amp into a 4R load. The fact it could run at 2R is of no consequence.

 

Assuming they both give a genuine 1000w at 4R they will both achieve the same SPL from the speakers and clip at the same point.

 

2R running (or not) is normally a thermal issue for amp designs

[Andy Westcott 0]

Although if you then connected another identical 4 ohm speaker load in parallel to the one already connected, the amp, assuming it could survive a 2 ohm load, would put out almost double the power, depending on the internal resistance of its power supplies, and that would increase the SPL developed by the two speakers by close to 3 dB.

 

I love these tech. discussions! http://www.dj-forum.co.uk/html//emoticons/tongue.gif

 

 

[Splosh 0]

Lol,

 

I put in a little post thinking there would be a simply answer!!!!

 

little did I know that you buffs, would confuse the eck out of me!!!!!

 

Think I need to do a little homework on amplifiers and the techy stuff!!!!!!!

 

Splosh

[norty303 0]

QUOTE

would put out almost double the power

 

Not in all cases, depending on amplifier and PSU type.

 

E.g. PLX3402 700 at 8R, 1100 at 4R, 1700 at 2R.

[transeurope 0]

Norty, I am interested in running a 3/4way system and I like your ideas.

 

I would be very interested in your real world experiences.

 

Firstly, most tweeters are rated at approx 50-100w RMS, what power are you putting into them? I would like if you would be kind enough to state the nominal power you put into them, taking into account the ohmage of the amp and the speaker (oops impedance or should that really be reactance in this case? I worry about these things...)

 

For example, if the tweeter is 100w 8 Ohm, do you run it off an amp that puts out 100W at 8 Ohm, or do you overpower it, like 120W, 200W, or even, as I have seen suggested 300W.

 

Secondly, I like your idea of driving more midrange through, but are you not worried of blowing the tweeter? Could you outline how you make your decisions?

 

Obviously it is all working out for you, so some real world help would be fantastic?

 

Thanks

[norty303 0]

All of my rig is custom built from proven plans so the components are selected for their suitability to the job.

 

My tops are P-audio compression drivers BM-D450 which are 1" throat. They're rated at 80w/rms and 8R and i power them off a Warrior RS-500 amp (to be changed for a Chevin A500 when funds permit) which gives 175w/ch at 8R. I run the amp at full power but use a hard limiter to stop it clipping and i've not had any failures.

 

A friend only buys QSC PLX3402 amps (it's not cost effective to buy the smaller ones really) and he runs his 2" compression drivers off them. Thats 700w/ch at 8R but obviously he doesn't crank it and uses effective limiting.

 

 

I'd always use an amp of at least 1.5 times the rms rating of the driver but i'd be sure the cab was well designed and capable of it first. I've seen too many boxes that use inappropriate drivers for the job which bottom out or exceed xmax on less than rms power. All of my boxes can safely take 2 times their rms rating at least.

 

I'd like to put a little more power into the compression drivers just to give me some more headroom when running hard.

 

 

I make my decisions by using my ears, applying theory (e.g. the comp driver is better at responding to fast transients by nature of it's small and light diaphragm, so theoretically should produce more accurate sound for vocals, etc) and measurement using RTA and analysis software like SMAART to prove or disprove that. It's interesting what it can show you.

 

Here's a measurement of my mid/tops done on friday which has EQ correction applied to bring the sparkle up in the top end. The rest is corrected by playing with crossover slopes and frequencies. As you can see there is a dip around 2khz. Despite trying a few things this appears to be a characteristic of the comp driver/horn combo. Thankfully the SN15MB is a great midbass driver and performs very well up to 1.8k and fills the gap effectively. I could cure this by going for a 1.5" throat comp driver but it's more cost I'd get some serious SPL gains though.

 

http://myweb.tiscali.co.uk/substance/x15_plot_eq.jpg

 

I might be going for a more single minded 12" or 10" horn loaded mid top though, which should achieve 108db at 1w/1m at least, compared to the 100 or thereabouts of my current setup. To put that in perspective, i can get around 128db from my current boxes by using 700wrms per box. I could get 129db using only 128watts with the horns and peaks of 135+ using full power. Horn loading is sooooo good!! http://www.dj-forum.co.uk/html//emoticons/biggrin.gif

 

 

By having a dedicated bass speaker between the subs and mids adds so much more punch and clarity in that range. I play mainly harder dance music on my system but it also makes the kick drum of a live kit sound superb and tight.

 

To be honest the comp drivers are only £40 andthe diaphragms very cheap so it's not a big issue if you blow one every now and then

Edited October 30, 2005 by norty303

[Andy Westcott 0]

Norty303, that's an interesting spectrum analysis program you are using;

Any chance of sharing the name and price?

 

I still use the SPL meter/analogue signal generator when I design my systems!

 

No mention of bullet radiators so far; Better coverage into the upper treble range than a normal compression driver/horn combination. Ideally, if you have the resources use both!

 

Personally, I use a 3-way system comprising Fane drivers. I've found them to be superbly built and conservatively rated.

 

For bass I use a Colossus 18B-600 on each side in a ported enclosure;

 

For mid-range I use a pair of Crescendo 10Ms on each side;

For treble I use a pair of ST 5022s on each side.

 

I use a 2-way active crossover to separate the bass at 200Hz, and a passive crossover in the mid/tops to split the signal there at 6Khz, along with a 6dB attenuation of the treble to equalise for the 112dB/watt/metre efficiency of the bullet units. As the frequency is higher, the inductors are smaller and therefore it is practical to have a passive crossover at this point.

 

I boost things at around 16Khz with the EQ unit, as my lad says it makes things sound slightly more 'sparkly', but as this is at the limits of my hearing I can barely tell the difference!

 

In theory there should be a 'suck-out' with this system between 4Khz and 5khz according to the driver data, but in fact it isn't noticeable and barely shows on the graphs.

Edited October 30, 2005 by Andy Westcott

[norty303 0]

QUOTE

No mention of bullet radiators so far

 

That's what i mean by supertweeters. I'd probably go for slot tweeters though rather than bullets.

 

The application is SMAART by SIA. I also use SpectraRTA. You can download a 30 day trial of both off the net. Hint - set a system restore point before you install SMAART. When the time runs out, roll it back and start again. SMAART is fairly high end (read - expensive) but really does it all and is industry standard and can interact with other kit too for easier setups.

 

The region from 2k to 6k (varying sections) often needs some attentuation anyway to stop some harshness. CD's especially tend to get very bright in this area with hi-hats becoming very snappy

[Andy Westcott 0]

Yep, I'd agree with some attenuation of the mid-range. I like to have a nice heavy bass output in the 40 - 50 Hz region for when the music contains fundamentals in this range, but without going over the top. I find it makes the system sound powerful without subjecting the listener to too many decibels in that critical mid-range which is the region most likely to cause ear damage.

 

Thanks for the info on the software, I'll have a look at it.

[transeurope 0]

Big up! That was a great answer Norty. Thanks for putting such effort into it.