BillFitzmaurice.info

If I know I will never drive a T39 past 100W or so (no point in it anyways), and
will low pass it at 50Hz, do I need more than about 300W of amp per T39 with
a 3012lf? For that matter, do I even need a 3012lf?

Same thing for DR200s: I'd rather build more cabs than push them harder. If a
cab is rated for 325 watts (Delta Pro 8A + 2 ASD1001), can I feed it 75 watts
without a problem?

Frankly, I'm trying to do this as cheap as I can: I'm not going to be making
tons of cash doing gigs every night that would pay back my expenses in
putting together a decent PA for what I do, and the cost of amps rises
geometrically with the number of watts they put out. Just can't afford 2 or
3 crown xti 4ks.

I'm not sure how you know up front that you will never use more than 100 watts. But wouldn't you rather build 2 T39s with 3012LFs than to build twice as many with a cheaper speaker? Don't forget - lumber, hardware, etc all cost money too. I'm sure you meant to say that you are going to high pass at 50hz.

If you want to save money, go with the Crown XLS Drivecore amps - much cheaper. Bridge an XLS1000 to run the subs. Run the tops off either an XLS1000 or 1500 depending on the speaker used.

I can understand the idea of more cabs and not pushing them too hard, but if you are only going to use 100 watts on a box that can take 400, then you aren't making use of your equipment. Like taking a dump truck to the store for a loaf of bread. Build half as many cabs and run 'em at 200 watts and you still are only half way to what they will do.

I played last night with 2 T39s and 2-OT12s and was told we were really loud....I never got past -20 on the board..and this was an open air pavilion.

So, my advice is to build with the quality components, power them properly and it will be less expensive than building twice as many with cheaper components and double the amps (even though they are less powerful).

If you read the recommendations on how much watts of amplifier to by, they say to get roughly 2 times the rated capacity of the speakers, so you don't blow things up.

So for 2 DR200s with Eminence Delta Pro 8A + 2 compression drivers, that's 1300W. If I biamp, I'm still looking at 900W and 400W for mids and highs. Any way you look at it, that's quite a lot of amplifier, even monoblocked.

If I can, I'm wanting to buy used amps. So, I guess what I'm asking is, can I get away with less than the recommended wattage, and how do I figure out how high I can turn things up before I need to worry about clipping?

el_ingeniero wrote:If you read the recommendations on how much watts of amplifier to by, they say to get roughly 2 times the rated capacity of the speakers, so you don't blow things up.?

'They' are wrong. Read this.
http://billfitzmaurice.info/forum/viewt ... =10&t=1886

That helps a lot! Thanks!

Looks like I could get started with a couple of XLS 202s and something smaller for the compression drivers.

el_ingeniero wrote:That helps a lot! Thanks!

Looks like I could get started with a couple of XLS 202s and something smaller for the compression drivers.

I would not even consider bi-amping DR200s unless you have a stack of at least four per side. Only at that point would there be some benefit in dividing the power chores between the woofers and tweeters. The main reason for bi-amping is low sensitivity direct radiating woofers, which suck power so hard that there's not enough left over for the tweeters. DRs don't have that problem.

I thought the reason for biamping wasn't so much for power draw, but cleaner
sound from having the amp directly interact with the drivers. Anything that
improves sound quality is an important consideration for me.

Another personal consideration is that I know almost nothing about electronics
(I know it's sad), but I'm fairly comfortable setting up a Driverack unit. Not that
I couldn't hose things even more completely with the Driverack.

There are many ( at least 8 ) major advantages of active crossovers over passive.

Syd

el_ingeniero wrote:I thought the reason for biamping wasn't so much for power draw, but cleaner
sound from having the amp directly interact with the drivers.

The main reason bi-amping sounds better with most commercial gear is the strain put on an amp driving inefficient direct radiating woofers. That strain carries over to the HF elements and is audible. With horn loaded woofers the drivers are loafing, and the amps are loafing, so everything sounds cleaner. Use enough cabs and the amp's not loafing anymore, so if you need more power to handle the load you might as well bi-amp, and save $ by using a smaller amp to handle the HF drivers.
There is the matter of passive crossovers introducing distortion, but that's also related to power. Horns=less power, lower distortion.

el_ingeniero wrote:Frankly, I'm trying to do this as cheap as I can: I'm not going to be making
tons of cash doing gigs every night that would pay back my expenses in
putting together a decent PA for what I do, and the cost of amps rises
geometrically with the number of watts they put out. Just can't afford 2 or
3 crown xti 4ks.

A passive crossover is cheaper than buying additional amps. If you are running a bunch of cabinets and have to add more power amps to power them, then it makes sense to buy smaller wattage amps to run the highs....but you are going to spend a lot of money before you get to that point .... doesn't jibe with the statement above.

Build with the passive crossovers, then when you build the PA bigger - consider bi-amping (I'm sure someone will buy your passive crossovers from you).

I see what you're getting at. I guess I can at least try the passives. If I
am feeling rich, I can buy another amp later.

I found a killer price on Crown Drivecore amps at Northern Sound & Light,
low enough that I can pop them in the 8U rolling flight case I have instead
of getting a separate amp case to cart around a pair of XLS 202s, without
costing much more.

el_ingeniero wrote:I see what you're getting at. I guess I can at least try the passives.

Another consideration is that we don't use generic off the shelf passives. They are optimized for the designs and improve/flatten frequency response. That's less of a concern with a stack of cabs, which also improves and flattens response, but with a smaller rig they work better with passives than without.

Hi from France!

I'm a brand new member on this forum, and this is my first post...

I play bass guitars and i'm looking for building a Jack 210 or 2 jack 10 cabs.

I've just read the topic on amps clipping, but they are some things i don't understand...

I think i'm right when i say that when clipping, an amp gives more watts that it's supposed to be.

And this can damage the speakers.

So Maybe the solution is to choose a speaker that can easilly handle the max rms power of the amp.

Am I right?

Then a second question comes in mind : I play rock music, that means growling bass sound, and supposes to push the amp gain. But then, the amp often clips...

So, in this case, with a powerfull speaker, over the amp power, but playing with some gain on the amp, sometimes or often clipping, is there a risk of damaging the speakers?

Is it the same when playing on a "standard" cab, is it worth on a BFM cab?

And at last, is there a risk for the amp?

I hope my questions are clear, thanks for your answers!

I've just read the topic on amps clipping, but they are some things i don't understand...

Try to visualize.
An amp that is not clipping will faithfully reproduce a sine wave without altering it's shape.
The waveform will be a copy but larger.
When an amp is driven beyond it's design capability it will distort the signal by adding additional content ( both harmonic and non-harmonic ) to the signal and it will not be able to reach the peak power at the top of the signal.
In essence, like being on a trampoline - hitting a ceiling it "Clips" off the top of the wave and effect turns clean sine waves into dirty square waves.

Speakers are grossly inefficient converters of electricity into sound.
So the goal is to make the most of the power available by using cabs that produces more SPL for the watts given.
N'est Pa?

Syd

The area contained between the +/- voltage wave and the baseline is proportional to the amount of power being made. So with the same peak voltage the clipped square wave is putting a lot more energy thru the speaker.

If you buy a preamp to make a dirty sound and then amplify it with a clean poweramp it's still a dirty sound but you can control the volume level.