[lsiberian]

Hi.
I'm planning my new system. I want to build a 3 way active system (front speakers).
My current ideia is to use the ULTRADRIVE PRO DCX2496 as the crossover. The amplifiers will be 3 A500 also from behringer (one for each channel).
The drivers configuration will be MTMWW. The tweeter is the Seas 27TBFC/G, the midwoofers Dayton RS180 and the woofers RS270. The box will be sealed because I want the most clean and "fast" sound I can achive. The midwoofers and woofers will be wired in parallel (4 ohm load on the amplifier). I would like to add a third woofer (MTMWWW), but that would have a dificult impedance for the amplifier. Why another 3rd woofer? Because of the added dinamics and lower distortion numbers at a given listening level. Any solutions?
I currently have a TC 2000 15" subwoofer in a sealed box with 110 L crossed over at 60Hz.

I'd suggest you do a passive 2-way for the top and then go active with a bottom driver.

1 Your wasting amp on the tweeter and upper-midrange driver.
2 There are a lot of issues your are gonna have trying to actively cross the tweeter and upper-midrange driver.

The A500 has a known defect with a distorted note at around 1000hz I believe. This has been shown in one case to be caused by being placed on another warm device. I do suggest you give them some breating room in your rack as such. I'd also propose you look into the EP2500 amp instead. The versatility and limitless power of these amps will do the trick with no concerns for defects.

I was able to get a Rotel 75watt stereo amp for ~$150US that I'd argue is going to be better than A500.

Maybe in terms of non defects, but a consumer level amp is going to complicate things a lot.

You can't use the XLRs on them with Pro-Audio devices so you'd need to attenuate the signal after passing it with an XLR to RCA cable. It's doable, but for only 75 watts per channel I think it's a bad tradeoff. Besides despite repeated arguments about amplifier sound I've never seen a DBT show anyone able to detect differences between solid state amps.

If you're truly on a budget you may comb Craigslist and ebay for QSC amps. They are kind of a first level pro-audio gear company.

As this is a high expense project I suggest you do it the best you can and not cut corners. Even if it takes longer.


If this is gonna be your first build. I suggest you get your feet wet with the Recession Buster Kit from Madisound first. It comes with the crossover and drivers for 59 bucks. Not bad at all in my book.

For fill you can get fiber very very cheap at home depot. It's not quite OC 703 or rockwool, but it's still more effective than Polyfill and a cheaper. I saw a roll for 10 bucks the other day.

 

[lsiberian]

Quoted from Mark(one of the smartest and most experienced speaker builders on the planet) I don't want to reinvent the wheel so I'll use his summary.
Advantages of biamping.

1). Reduces insertion loss of passive crossovers. This is negated unless active crossovers are used.

2). Reduces distortion and problems of reactance of passive crossovers, especially with lower crossover points. Again this advantage is only gained with active crossovers.

3). Increases power available to the speaker as long as the crossover point is around 400 Hz. 400 Hz is the area of the power divide. As the crossover point is raised the power advantage is rapidly lost, as the power required to produce those frequencies rapidly diminishes.

4). Theoretically biamping can reduce inter modulation distortion. However this is a non issue with competently designed amplifiers.

Disadvantages of biamping.

1). Requires a complex electronic crossover that has to be designed to the drivers just like a passive one. So advantages of biamping are only truly realized with a design done from the ground up with active crossovers.

2). One amplifier with twice the power versus two amps of half the power biamped is less likely to clip. The reason is that program is variable. Say we have one 200 watt amp versus two one hundred watt amps biamped at 400 Hz. If the program calls for 150 watts below 400 Hz, then the HF amp sits idly by while the LF amp clips. The 200 watt amp might well not have clipped.

3). If different amps are used there is great opportunity to introduce serious phase problems at crossover, unless the amps phase responses are known and corrected.

4). Generally costs will be increased as well as complexity.

In general the advantages of biamping are only realized with crossover points below 500 Hz using active crossover as part of a total design solution.

The reason being that passive crossovers in the 1.5 to 5 kHz range are far less deleterious than passive crossovers below 500 Hz. In my view crossover points below 350 Hz are best accomplished with active crossovers.


So basically you are correct for bi-amping the lower part of the 3 way. But the upper part is just silly if you think about it. If crossover design is a concern remember that madisound will do a design for less than 40 bucks usually. I'd just pass off the design to them for the upper 2-way portion and then you eliminate extra amps and make you life easier.

You should only need 1 driver per speaker per range. Pick good ones and you'll be set.

Tweeter, Midrange, Mid Bass Module(I use a small sub for this), Subwoofer.

 

[lsiberian]

This is getting interesting.
I want to think the sugestions already made.

lsiberian in fact I have readed those informations about bi-amping. But sometimes I miss some points.

I'm just going to discuss the disavantages.
1- If I go the bi-amp way, I would save money from one amplifier (aprox. 200 €). Great. But, I will need to spend on the passive crossovers. Maybe 80 € for both. That saves me 120 €. Also I will be loosing 2 outputs on the DCX, right?
I agree that 120€ is a considerable amount of money, with that I can almost build the rear speakers for a 5.1 system. But also look at this, I'm young, and certanly I will want to do more teaking and some upgrades in the future, going tri-amp (or 3 way fully active) I'm not going to loose the money spent on the passive crossovers. But I'm still considering any reasonable option.

2 - I completly agree that "one amplifier with twice the power versus two amps of half the power biamped is less likely to clip"

3 and 4 - I make JCD my words.

JCD by your comments I assume that you encourage the 3 way full acive, right?

Please, lsiberian and JCD (and others), don't be affraid to discuss more issues, better now then later when money is spent.

1. Not sure how you are getting that a passive crossover is going to cost you 80 euros. Most can be assembled for far less.

2.You can still manipulate the entire sound of your system with the DCX. You'd be giving yourself the ability to hook up your subs to the DCX. Meaning you could have a 4-way setup with the subs fully eqed.

3. Fully active is just as time consuming as making a 2-way upper module filter. I"m not talking about passive between your bottom driver and the top. Only between the tweeter and the midrange.

4. Don't forget that XLR cables aren't cheap either.

Ultimately the choice is yours.

But I would encourage to at least give the passive crossover a go. If anything it will be a valuable learning experience.

If this is your first project I still suggest you start with a simple 2-way build before you undertake this beast. I don't think stepping into this as your first project is wise. There is a lot to learn that you will want to get before you build your longtime main speakers.

Either way make sure you treat your cabinets with fiber or rockwool and that you brace the out of them.