Advice needed to build new 3 way active system

A few comments:

I'd pick a different mid -- the RS180 doesn't go high enough imo. I'd pick something that had a published range extending on the high end to 3000hz or 3500hz at least. That should give you some good overlap with the tweeter. I'd look for something in the 5-5" range. The RS150 already mentioned seems to be where I'd look.

The amps you've listed are a great price/performance model. If you can find something that's less expensive that puts out ~35-50watts, you could do that. Obviously, the tweets don't need the same power that a woofer does.

I'd probably stick with 2 woofers -- it does seem like it would make the speaker prohibitively big. What you could do to get the same dynamics you're looking for is to go with a bigger more efficient woofer. For example, if you went with just one of these, you would probably get a better response than with two of the Dayton woofers you're looking for. It would be a little more expensive, but I think you'd like the results better.

The active crossover you've picked is exactly the one that I will use whenever I finally build my all out acive 3 way system.

I will try to answer everyone, not without to say Thanks to the comments already posted.

First the choice on the RS180. In fact the RS150 was my first choice because of the ability to reach a higher freq. But some DIYers were saying that the RS180 is a better choice, the RS150 has also some nasty picks that I should be able to deal with. I will look for more freq. response graphics. But now that I have other opinions I might choose the RS150 .

For the XO points I'm thinking in something like this: 250 Hz (4th order) and 2300 Hz (4th order also) for the RS150. For the RS180 I was thinking in 2000 Hz. Want do you think about this choices? Can I push the RS150 to the 2500Hz region?


Using 3 270 is a too low impendance, I'm aware of that. The size of the enclousure is a real problem, not for me, but for my wife. 6 cubic feet sealed is my size limit, so that sets "only" 2 RS270 .

I know that for the tweeters (and also for the midrange) I don't need all the power from one A500, but I thought that would be better to use only one amplifier model. But maybe a could use a diferent one that matches the drivers specifications better. Do you have some sugestions? Please, only amplifiers with passive cooling.

Now the driver that JCD recommended. In fact I don't know that driver. But as I'm living in Portugal bying from USA means that I must pay customs. For my TC2000 I had payed nearly as much for customs as I did for TC Sounds Inc. The Dayton drivers I'm buying from bmm-electronics.com
Also, using a 12" driver means that the enclouser front baffle must be very large, WAF comes into play again.
More recomendations?

Thank you all.

Zeverin said:

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.

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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.

JCD said:

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

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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 said:

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.

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I know that I'm wasting amp on the tweeter and upper-midrange driver. I'm still trying to find a cheaper amplifier with good sound quality and adequate power.
What are the advantages going with a passive 2 way just like you said, aside cost?

Do you think that is not possible to achieve a good integration between the tweeter and the midrange using this crossover? Can you be more specific in those issues? A little more info in my speaker configuration. The tweeter and mid drivers wont be centered to reduce baffle diffraction.

lsiberian said:

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.

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Whichever amplifier I choose I will give them enough breathing room. Thanks for reminding that. I already have a EP2500 to driver my subwoofer. For this purpose I think the EP2500 is too much, and will raise the system cost, and I would like to stay with passive cooling.

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 said:

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.

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I will not claim to be an expert regardless of whatever "mod" status I may have, but I have some followup questions/comments

1. Isn't this satisfied by buying a commercial product like the Behringer unit Zeverin mentioned? I would agree that building from scratch would be a LOT more difficult, but something like the Behringer with it's variable crossover point takes most of the complexity out of the equation.
2. I have some potential problems with that one as well. My understanding is that you gain ~3dB's by going active. If you go from a 100 watt amp to a 50 watt amp, you loose ~3dB's. That's pretty much a wash. And if we're talking about a tweeter, you're still going to never use 50 watts unless you want ear-damaging loudness.
3. The potential phase issue can be "fixed" by physically moving either driver forward or backwards a little. Also, the Behringer unit has the ability to adjust the phase of the drivers independently, so you should be able to get the drivers in phase with a little bit of testing -- , you can maybe even get the drivers not just in phase, but perfectly time-aligned. With a passive crossover, you're much more limited in adjusting the phase of the drivers. Granted, whatever phase issues that come from the amp are negated, but there are still going to be some phase issues that you will have less ability to deal with at the electronic level.
4. I do agree -- it will cost more to go active. However, as you can see from the above comments, I think it simplifies the process, assuming you buy a unit like the Behringer DCX2496.

Again, just my semi-informed opinion.

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.

Zeverin said:

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.

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That is actually something I hadn't really thought about, but adds to my pro active approach. And depending on the parts you get, and how complicated the crossover scheme is, 80€ for the crossover parts may be on the low side.

Zeverin said:

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

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I posed this question to someone I know that has the technical backround to address this point -- his contention is that a 200 watt with a full range signal is more likely to clip than two 100 watt amps with an active crossover between them. There is a thread someplace on the web that this arguement has been addressed -- if I can find it, I'll post a link. I think lsiberian addresses the issues in most real world examples by actively crossing the <250hz signals, but I really don't think this is going to be an issue if you've got ~50 watts for the tweet and ~80 watts for the mid. , the tweet probably can't even handle a sustained 50watts.. but I digress.

Zeverin said:

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

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Absolutely. There are dozens more advantages to active systems that we haven't fully discussed, such as the ability to perfectly time align the drivers using a well designed crossover, the ability to accomplish perfect phase and impulse response without much effort and without the terrible side effects of passive components attempting to pull it off, improved power response, elimination of microphonics, the ability to create the absolute most ideal filter with virtually no tolerance, the elimation of shift in tolerance related to input voltages. the elimination of back-current artifacts in the crossover, increase in realized damping factor, and many more. (note, this paragraph is shamelessly copied from another thread on another forum)

This doesn't even take into account the ability to subsequently tweak the system using different types of crossovers (e.g., Bessel or LR or Butterworth) or different orders (6dB, 12dB, 18dB, 24dB, etc).

I don't want to completely oversell an active system -- it will still take time, skill, testing, etc to create a good system, but I do think it's simpler to do and offers a lot of tangible benefits over a passive system. And I will put my money where my mouth is -- when I finally build my "all out system", I'm going fully active in a 3 way system and I'm going to use that same crossover you've picked.