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View Full Version : what amps to power 3-way dipole, $800 budget



thadman
12-01-2006, 11:59 PM
After reading up on diyaudio.com on what amps to use for my 3-way dipole towers, I am absolutely clueless:crap: Im not sure whether pro audio amps vs high end home amps make a difference sonically, and if I'd prefer either over another.

I need to power a pair of Peerless HDS 1" tweeters, a pair of Seas Excel W18Es, and a pair of Dayton RS15 HFs:D

The Peerless has a 93dB (8ohm) efficiency

The Seas Excel has a 86.5dB (8ohm) efficiency

The Dayton RS15 has a 90dB (4ohm), so effectively 87dB efficiency

Since the tweeter is roughly +6dB over the seas+dayton, im going to need 4x the power for both the seas and dayton:D

Im going to be using a DCX2496 for crossover/equalization and maybe a DEQ2496 for RTA use and other equalization purposes, if that means anything. Im also not sure what cd player ill be using (ive got an old cd player from the mid 1990s, sony or yamaha something along those lines)

What combination of amplifiers would you use to power this setup? I have a maximum budget of $800 (although I'd like to spend closer to $600).

I had fancied the idea of using 6 300watt BASH plate amps ($630 shipped from partsexpress), but am wondering about their high frequency performance.

ballstothewall
12-02-2006, 02:34 PM
If your going to use pro amps, do not go cheap and get any Behringer amps, thats all I've got to say.

800 bucks for three amps seems like a pretty small budget to me though...

thadman
12-02-2006, 02:39 PM
In the home environment do amplifiers play a large role in sound quality? Other than having a lot of power for dynamic purposes, do amplifiers have a strong sonic presence?

T3mpest
12-02-2006, 02:44 PM
No, not really, no more than in a car. There are differences, but they are minute and can be EQ'ed out anyway, assuming you hear them in the first place. Secondly, there's nothing wrong with behringer. There's a large difference between bottom end pro audio and bottom end car or home audio, in terms of quality.

ballstothewall
12-02-2006, 04:17 PM
No, not really, no more than in a car. There are differences, but they are minute and can be EQ'ed out anyway, assuming you hear them in the first place. Secondly, there's nothing wrong with behringer. There's a large difference between bottom end pro audio and bottom end car or home audio, in terms of quality.

Theres a reason I replaced my behringer with QSC...

thadman
12-02-2006, 04:17 PM
How are Alesis amplifiers? or gainclones?

Theres a nice 50 x 4 @ 8 gainclone on ebay for $219 buy-it-now

joetama
12-03-2006, 02:28 PM
Theres a reason I replaced my behringer with QSC...

I agree on the QSC > Behringer thing. Behringer amps are nothing special at all and are pretty lame vs. QSC or LabGruppen.


How are Alesis amplifiers? or gainclones?

Theres a nice 50 x 4 @ 8 gainclone on ebay for $219 buy-it-now

It's a good rule of thumb that if it's cheap there is a reason for it ;)....

thylantyr
12-03-2006, 02:45 PM
Gainclones or chipamps are low powered amplifiers with weak low impedance
drive. They are what they are. I don't think they are worth the money unless you
built one for a few dollars buying scrap parts and getting free-bees.

Re: Behringer EP2500.. it's a QSC RMX2450 clone.

RMX2450 pic;
http://home.pacbell.net/lordpk/proamps/RMX2450-1.JPG

EP2500 pic;
http://home.pacbell.net/lordpk/proamps/EP2500_older.JPG

I saw some 2 ohm tests and the EP2500 was a little weak in 2 ohm performance,
otherwise no issues. That pic I saw a couple years ago created an optical illusion
as it appears to have a smaller toroid transformer.

Then I found a new EP2500 pic;
http://home.pacbell.net/lordpk/proamps/EP2500-1.jpg

If you look closely, the EP2500 PCB design is smaller making it appear to have
a smaller transformer in the first pic, but the new pic seems to indicate the
EP2500 does have a nice sized transformer. Who knows, Behringer could have
installed a bigger one in later models.. Point is, it's a valid amplifier to consider
since it's a clone. The only issue would be the transformer and it seems to be fine.

Proamp SQ is fine, don't worry about it.

thadman
12-03-2006, 04:25 PM
How much of a difference would I notice between say a QSC PLX1602 and a Behringer EP2500? The QSC would cost a lot more, and 98% of the time im going to be playing these speakers at extremely low volumes. The lowest impendance I'd expect the amps to drive would be 4ohms (all others would be 8ohms), and that would be for the Dayton Reference 15s. The amp would be running stereo (not bridged).

Would a Behringer EP2500 be just as good as the PLX1602 (insert other awesome proamp here), considering my circumstances?

thylantyr
12-03-2006, 05:45 PM
You want to build a fully active 3 way loudpeaker + sub.
You need 6 amplifier channels + sub.

The tweeter and midrange amplification doesn't have to be as robust
as the woofer and subwoofer amp.

To drive the woofers in your 3 way loudspeaker, I would get a beefier amp,
no chipamps, no gainclones, and I don't even think I'd run the Behringer A500
in spite that can probably drive them ok since you don't plan to push the system
hard. The A500 is a clone of one of the Alesis amps.

To drive the tweeters and midrange you can drive them with chipamps,
gainclones, low powered tube amps, etc., but I can't guarantee that you
will be satisfied.

Also, there are issues to examine. Do you three proamps stacked? If so,
do you want the same brand? if so, do you want the same model number or
scale the amps according to duty? ie, lets say you went with A500 amps,
a three stack would look nice but the A500 driving the woofers might be
anemic, I don't know if it will satsify you. Suppose you went with a three stack
of EP1500 amps, the same question comes up. Will one EP1500 drive the woofers
to your liking? What if mixed models? What if you did two EP1500 to drive mids/tweeters and one EP2500 for woofers? Looks nice and more power allocated to the woofers? What if you bought a PLX amp and added two A500,
the three stack would look funny mixing brands. Aside from functionality, you
have the cosmetic issue to think about.

Another variable is fan noise and interfacing to consumer gear. The A500 is
RCA input, no fans. A nice bonus. Two of these amps, one for a pair of tweeters
and one for a pair of midrange might be pretty cool as you don't have to worry
about the fan noise issue, no need to worry about fan mods if you think the fan
noise is too high, and if it has RCA input, one less worry about interfacing. You
could buy one A500 and test it. Connect the tweeters only and listen? Is it ok?
if so, connect the amp to the midranges only and listen. Is it ok? If so, try the
amp driving the woofers. Is it ok? If not, then get the bigger proamp just for the
woofers and use A500 for the top end. The six pack of Bash 300w is a neat
idea too if you can bypass the internal crossover.

Compare these ideas to a normal home audio idea. Someone would normally
suggest getting an ATI 1506 power amp for your application as it would make
alot of sense. A six channel amp in a single chasis. Perfect! But the price is high.
SQ won't be any better than the other ideas.

thadman
12-04-2006, 06:10 PM
How does (2) Crown XLS-202D amplifiers (1 for tweeter, 1 for midrange) + (1) Crown XLS-602D for the Dayton Reference 15s sound?

I could get them all brand new for $794 +s/h

thylantyr
12-05-2006, 02:51 AM
You can make that setup work. Just note that XLS has no 2 ohm power ratings
as it is an entry level amp, hence the lower price. Many people on the AVS
forum had great success with the XLS driving ordinary HT speakers. A few had
problems driving subwoofers at low impedance with higher power, the XLS
didn't deliver. You won't have any issues driving tweeters and mids with the
XLS and to drive the 4 ohm woofer it will probably work fine for your application.

but....

Another idea if you are patient.

Get two used QSC RMX850's on Ebay for ~$200 each.
Get one used QSC RMX1850HD or RMX2450 on Ebay for ~$400.

More power than XLS and RMX has 2 ohm power ratings.

Probably the best bang for buck is those 'buy it now' EP2500's on Ebay
for $246 - $269 each. Even if you derate them, they still have alot power
for the money, way better than spending over $1000 on a fancy high powered
reciever, should outperform the XLS series thermally as the XLS has weak
internal heatsinking.

Crown XLS402 guts;
http://home.pacbell.net/lordpk/proamps/Crown_402a.JPG

Where's da heatsinks? lol ... It's just a piece of metal, not a heatsink
extrusion normally found in better designs. This is one way to reduce the cost
but performance suffers, ie .. no 2 ohm ratings.

The EP2500 has real heatsink extrusion with the fins pointing towards each
other, then the fan blows air through the slots, ie wind tunnel type of cooling.
http://home.pacbell.net/lordpk/proamps/EP2500-1.jpg

thadman
12-05-2006, 04:52 PM
I have no need to run the amplifiers below 4ohms:)

3 EP2500s runs $820 shipped from eBay vs $860 shipped for the Crowns (they come with $100 of mail-in-rebates, so effectively $760)

The QSCs are an option, but them being used vs new is kind of putting me off.

Would the Behringers still be better?

thylantyr
12-05-2006, 05:06 PM
I don't see any issue with used amps vs. new. This is one area of audio that
you shouldn't worry too much about. I bought 12 proamps used last January and
saved huge $$$ and they all worked. All they needed was the covers removed
and blow in some compressed air to get rid of dust. I don't think people scam as much
with proaudio gear vs. maybe car audio stuff because you know those *kids* in
car audio like to pull off the scams more than the folks spending big coin on proaudio rigs.
// harr harr // joke

There is always risk of buying used gear and it not working so you have to
analyze that risk/reward ratio and determine what is best for you. Even if
you don't plan to abuse the Crown XLS amps at 2 ohm per channel, it is always nice to know that
the amps you buy are over-engineered as you may do something esoteric in
the future.

The good news is. The folks on the AVS forum said that rev D XLS amps
have variable speed fans, they just came out recently so if you do buy XLS,
verify that you get rev D amps as it won't be fun doing fan mods as the older
models have no variable speed fans so when you turn on the amp, you get
high speed fan noise. People have done resistor mods or fan replacement
mods to reduce the fan noise, the resistor mod reduces fan speed which
reduces air flow and you reduce cooling - not cool [pun :laugh: ]

If you still can't decide on EP vs. XLS, one idea is to buy one of each and play
around with the amps to see what you really like then re-selling or returning
the amp you dislike, albiet you lose some $$$ but you gain peace of mind
that you made the right decision considering you need three amps.

thadman
12-05-2006, 05:14 PM
Yeah, the crowns are "D"

thadman
12-05-2006, 05:18 PM
The issue with used vs new is that, I doubt ill drive them hard enough to notice the difference sonically or enough to break them. I will however notice a difference aesthetically, throwing down $800 on a bunch of used gear is hard to swallow, at least on my budget.

If the QSC RMX amps are that much better though, I'll highly consider them

thadman
12-05-2006, 06:02 PM
I've heard crowns fans are 71dB, if so what frequency is that? Is it the same as the RPM of the fan?

Could I simply replace the fan with another fan of the same size?

Im considering building an amp rack, so I could line the sides of the inside with acoustic absorbing foam/fiberglass:D It should quiet them down a good deal:D

thylantyr
12-05-2006, 08:01 PM
Proamp cosmetics arn't a big deal. The face is usually ok and not messed up,
but you will find scratches on the top/bottom of the amp because they may
have been stacked on top of each other. If stacked, you won't see the scratches
anyways and chances are you will scratch your new amps if you stack them
or even if you made an amp rack with shelves, you can make the rack tight
so there is little gap to notice any scratches.

The non-variable speed Crown XLS runs their fans at full speed, ie lots of noise
as the fan blade spins at high RPM, akin to your computer fan making noise.
The variable speed design may spin the fan at three speeds, low - medium - high.
If the amp starts to get hot, the fan RPM rises to cool the amp. The higher the RPM, the more wind noise you hear.

You can replace the fans with lower noise fans but remember that there is a trick
in the fan business. To get a fan to make less noise, the easy way to accomplish
this is to reduce it's speed, which reduces air flow. You need to find a fan with
equivalent CFM spec for the same physical size so it fits and check the dB noise
rating of the fan. It's counter productive to find a low noise fan with lower CFM
than the original one - hehe

To reduce noise, make a sealed cabinet amp rack with air flow vents,
maybe an intake and exhaust somewhere and then install sound absorbing
stuff inside. If the amp rack is 'open', then the fan noise will still be heard.