Little help setting up my system

[Lance_S]

Hey guys,

Need some advice. I purchased a couple of 2125's a long time ago and have been working on an install recently. I had what I thought to be twin 2125's. I sent them both out to Alek for a refurbish and come to find out one of them is a cheater amp. This is news to me. One of the 2125's is actually a 2250 (mac500). Sooooo, now I have to figure out how to setup my system and which amp to go where:

Here is the setup:

Head unit Alpine 7998
Crossover 3 way active off the deck
Sub Single Alumapro mx12 sealed in a box to manufacturers specs just behind the
rear seat.
Mids 6.5 Inch Massive Audio RK6's
Tweets Tweets that came with the RK6's

So here is the issue. I have a MS275 running the tweets straight at 4 ohms
I currently have the 2125 running the mids at 4 ohms
I was planning on running the other 2125 mono into the sub but now I have a 2250.

So the question is, do I run the 2125 mono into the sub and run the 2250 @ 4 ohms into the mids or do I run the 2125 into the mids @ 4 ohms and run the 2250 mono into the sub.

I am afraid the 2250 will overpower the sub even with the gains all the way down the beast is going to run well over 1000 W into a sub rated for around 400. Do I sell the sub and pick up something that will handle more power??? I want to stay with the best SQ sub I can find and the alumapro is pretty good, I just think I will rip it apart with the 2250 bridged.

The other option would be to run the 2250 into the mids. The RK6's are beasts. They will easily handle 250W continuous. I could then run the 2125 mono into the sub. That would probably be the best combo as far as gains goes but I am not sure.

What would you do?

Thanks.

L

[ttocs]

I will always opt to send more power to a sub then less. The max power rating on a subwoofer is one of the more useless numbers. Keep the signal clean and out of clipping and throw as much power as you want at it with that amp....

[Mr. Wild]

My feeling is that MS2125 would be better for the sub. Mids need lots of power too, if you are after some serious impact.

MS2125 can handle 2 ohms bridged, but MS2250 can't. What I'm getting at is that MS2250 would be closer to its limits bridged@4ohm than MS2125. When SQ is the goal, I never load amps to their limit.

The balance of power would be better too.

If you had a monster sub and listened to rap, then things would be different.

[Lance_S]

I was thinking the same thing, to run the 2125 to the sub. I ran the 275 bridged on the sub for a while Nd was surprised how well it ran it, the 2125 should really move it. The mx12 is pretty efficient and won't need the bridged power of the 2250. And the mods I am running should be able to handle the power, they are huge for 6.5's. They weigh in at 5 lbs a piece. I haven't seen larger magnets on anything in their size out there. They Need big power to get them going.

[Virtue]

Back in the day, one of the PG reps were using a Son of Frank in their car. The 2125 was powering their front stage (stereo) and the 275 was bridged into their sub. Very impressive. I have a Mac500 and I did run my fronts with it... wow, way too much power. The fronts had a tough time with that kind of power and I had to turn it way down. If I had your system, I would run the 2250(mac 500) for your sub (actually 800 watts 4 ohms bridged) and the 2125 for your fronts... If need be, your 275 for your tweets, although, the 2125 would do just fine running your entire front stage if you had passive cross overs for your mids and tweets.

If need be, the gains will be turned down a bit, but, why waste a 2250 for your fronts, use the power for your sub!

[JayGold]

MS2125 can handle 2 ohms bridged, but MS2250 can't.

I thought the original MS2125 can't handle 2 ohms bridged, but 2 ohms stereo it can.

Also what engineering changed form the old MS amps to the TA amps which state the MS2125 and MS2250 can both handle 2 ohm bridged stability?

[Lance_S]

I need to stay active to tame the tweets and I already have the 275 so I am going it use it. I want to run full active. I get what your saying about the mac up front being a waste but I am wondering if it's a bit of a waste either way. Bridged at 800W that MX12 Alumipro is gonna pop if I am not careful. I actually don't run my sub very hard so i won't blow it but I didn't know the 2125 couldn't be run bridged. It has a bridge switch on it. And it should be stable at 2, at least the owners manual says it is.

[Lance_S]

Just read an email from Alek. He said that the Mac would overheat bridged which makes sense because it's in a 2125 case without the fan shroud that the 2250 has so I guess that makes the decision for me. Mac500 to the mids, 2125 mono to the sub and the 275 to the tweets active.

Edit. I re-read the email. Alek said at 2 ohms. At 4 it would be fine so I guess the option is again up. The sub I am running is a 4 ohm sub.

[Virtue]

I need to stay active to tame the tweets and I already have the 275 so I am going it use it. I want to run full active. I get what your saying about the mac up front being a waste but I am wondering if it's a bit of a waste either way. Bridged at 800W that MX12 Alumipro is gonna pop if I am not careful. I actually don't run my sub very hard so i won't blow it but I didn't know the 2125 couldn't be run bridged. It has a bridge switch on it. And it should be stable at 2, at least the owners manual says it is.

The MS2125 is stable at 2ohms bridged mono which is the same as 1ohm stereo. I ran (4) MS2125 all day long at 2 ohms mono. Just supply it with proper power. I actually ran those same (4) MS2125 at 1 ohm mono at one time... it will do it, but, it had crappy sound and not too controlled. How are you running the Alumipro, in what kind of box? If you go sealed, it will sound better/more controlled and it will handle the MAC500's power due to the fact that since there is more pressure keeping the sub from moving, you will need more power to get it going. As for the MAC500, it is not recommended to run 2 ohms mono, but, I am sure it will do it well. It has a high dampening factor (good torque and control) The new MS2250TA had a circuit in them that would turn the amp off(go into protection) if you ran it at 2 ohms mono. I believe PG made the new MS2250TA this way because most people did not supply the original MS2250 with the proper power, which cooked the amps. Also the new MS2250TA does not have a cooling fan shroud. The MAC500 does not have this circuit. It's old school. I believe that's the amp you have. As for heat. It all depends on the make of the sub. I had a Lanzar OPTI 500 amp bridged at 2 ohms. It would thermal quite quickly with the Lanzar 15inch sub. I hooked up my Focal multi-magnet 15's and the amp pounded all day without heating up. Why? Because the voice coil on the sub was better. If the sub's voice coil stays in the magnetic gap, it puts less stress on the amp. I don't know if you can see the voice coil on your Alumipro sub, but if you can, physically push the cone up and see where the voice coil is. And then push it down. The voice coil should stay in the magnetic gap which is (within) the top plate on the magnet of the sub. It is normally steel. It is the steel plate on the top of the magnet structure. DD Audio uses a very thick one, hence the huge excursion. When the voice coil stays in that magnetic gap, all is good. If you totally leave the magnetic gap, you will hear the sub make a pop sound, so you turn down the volume. I know your sub is well made and the voice coil will be in the magnetic gap, so, if it was me, I would put the MAC500(MS2250) on your sub and put it in a nice strong sealed box. You will be amazed. But this is my humble opinion...

[Lance_S]

The MX12 Alumipro is sealed in a very strong enclosure to manufacturers specs. I hit's hard and is very tight. It's a 4 ohm sub so I could run either amp mono into it. I just run a single 12. I am currently running the 275 mono into it and a 2125 into the mids and highs passive but want to get away from passive and go active. The mids are strong with the 2125 at 4 ohms though I doubt I am pushing the amp very hard. The 2125 mono would be really strong into the alumipro as the 275 moves it pretty well, the 2125 mono is double to power.

It's a tough call. Does the mac500 drop to a 2 ohm load when bridged or does it stay at 4 ohms? Seems like a stupid question but I thought bridged they stayed at 4 ohms unless I ran 2 subs which would split the load. If the amps split when they get bridged then I will run the 2125 mono as it won't overheat. If they don't drop down to 2 ohms mono then I could run either the mac500 or the 2125 in either situation.

Probably the best thing would be to just test them out and see what is best. It would be easy to switch and test.

[ttocs]

maybe get an mq430, less power but still sounds good.

[Virtue]

When an amp says it is 2ohms stable, it actually means 2ohms stereo or 4 ohms mono stable. It is actually the power of both channels at 2 ohms stereo, just added together. So, for example, I have an amp that is rated 100 watts by 2(stereo) at 4 ohms. It is bridgeable and it is 2 ohms stable. Usually, the amp will say that it is 2 ohms stereo or 4 ohms mono stable. So what out put power can the amp do? Well, let's say that at 4 ohms stereo it is 100 watts, at 2ohms stereo it's output is 150watts. Well, in mono mode you take both channels and add them together. So, 150watts @ 2ohms plus 150watts @ 2ohms and you get 300 watts @ 4 ohms mono. Make sense. So, your amp at a 4 ohm mono load into a sub is actually seeing a 2 ohm stereo load. So, the amp is working harder.

For a MAC500 it is recommended to run at a 4ohms mono load and no lower, so, it is actually seeing a 2ohm stereo load. It's rated output is 200watts @ 4ohms stereo, or 400watts @ 2ohms stereo, or 800 watts @ 4ohms mono... Can it do 2ohms mono??? Yes, now read on...

Now, going back, PG amps had a high dampening factor. I believe it was 500 for the MS amps. This is the torque and control of the amp due to the large over head of high quality parts used. Every time you drop the impedance of the amp, the dampening factor gets cut in half. So, at 4ohms mono... it's actually seeing a 2ohms so, it is now at 250. Still good. Once you get at 100 and lower, you can hear the amp struggling and there is little control with subwoofers. I ran my MS2125 at 2ohms mono all day long which is 1ohm stereo, so the dampening factor would be at 125. This is still good. I did run this amp at 1ohm mono which is .5 ohm stereo, which the dampening factor is 62.5 and the amp sounded like crap. Absolutely no control... So, when buying the same so-called power amps and one is much more money, look at the dampening factor. This will tell you how good the amp really is, and if you can load the amp down into a lower impedance.

The MAC500 has a dampening factor of 500, so, you can see that you can load the amp down to a lower impedance than what PG says it can do... Just make sure you have proper power and some large caps to keep this power happy amp, happy and fan cool!

Funny thing, if you read any MS manual, it will say it is good for only 2ohms stereo or 4 ohms mono... I had to laugh. It can do way better than that!

Hope this makes sense.

Truthfully, I love the MS 2125 on the fronts. It has the exact power today's fronts need. I used to use a MS275 and it was not powerful enough at 4ohms stereo. I did try the MQ430 and I had to bridge it in stereo mode to get more volume out of it. It's output then was 100watts by 2 @ 4ohms.

[Lance_S]

Virtue,

K, thanks. I am with you. Just to confirm, because my fronts and subs are 4 ohm, when running the 2125 in stereo into a 4 ohm load, the amp sees and outputs a 4 ohm load. When it's bridged into a single 4 ohm sub, it's still outputting a 4 ohm load (obviously with more power). So whether running stereo into 2 separate speakers for running mono into one individual speaker, it's running at 4 ohms, correct?

I know they are capable of running down to 2 which increases output but also doubles distortion if I am correct (and makes them run hotter and less efficient). And i don't need the extra power so my plan is to run all three amps active, each in a 4 ohm load. 275 to the tweets (overkill I know), 2125 mono into the sub and the Mac500 stereo into the mids or visversa. Either way, the amps should all be running at 4 ohms.

I know this isn't the most efficient way to set it up. But the way I understand it, correct me if I am wrong, is that in this case:

1. It will give me complete control actively off my deck (alpine 9887)
2. It will keep all the amps running at a 4 ohms load which will keep them cooler
3. It will be less demand on the power source
4. It will produce the least amount of distortion possible

The Mac500 stereo might be too much for my mids but they are really power hungry (massive audio RK6). Weighing in at 5 lbs each they are monsters. I have them running off the 2125 stereo right now and they sound great but i can lightly clip the amp when running them at strong listening volume. The alumapro is pretty efficient and may or may not be able to handle to Mac in mono. But like I said, it will be easy to swap them back and forth to see what's best. I guess worst case would be I could sell the alumapro and go with a 12" IDv3 or something similar.

Thanks,

L

[Virtue]

If your RK6's can handle the 2125, then try the MAC500. I did notice that you mentioned that the 2125 was at slight clipping. If you are looking at the red clipping lights on the side of the amp, those are sooo misleading. I went through this with my amps. Completely ignore them. You physically can hear the amp at clipping. Those LEDs should be flashing, but, should not be constantly on. If you are not seeing a good hard flash of those LEDs, you don't have the amp turned up properly. I now this sounds weird, but, trust me, those clipping lights are not accurate and should be ignored.

Just to clarify your thought, concerning the amp @ 4 ohms mono. Honestly, the amp is actually seeing the stress load of 2ohms...

The only amp that will be heating up a bit, is the one powering your sub. All the other amps will be almost at idle. But, go for it! Your setup will sound amazing with the 275 for tweets, 2125 for sub and 500 for your mids.

[ttocs]

first I have heard ever recomending to push any amp into what it warns is clipping......

[stipud]

In my experience sometimes the clip lights don't come on soon enough. Especially with a subwoofer I would not recommend trusting your ears, as we cannot hear distortion accurately at low volumes. Plus our amps clip pretty soft, so you don't hear it until you are pushing the limits quite dramatically.

As for which amp to use... try it both ways, and see which balance you like better. Personally I'd rather have the added power on the front stage, especially if your sub is designed for 400. A powerful front stage requires proper sound treatments too; this is probably far more important than amp selection.

[ttocs]

I would have to say that unless you have an oscope running next to the amp to see that the clip light is going off early, to pay attention to it.

[stipud]

I would have to say that unless you have an oscope running next to the amp to see that the clip light is going off early, to pay attention to it.

Bingo. PG recommends to tune the gains so that you barely see the clip lights, but I'd suggest using test tones and a multimeter to verify the clip lights are doing their job in the first place. For example my Audiosource EQ didn't turn on the clip lights until 13v, but it's only rated for 8v... with a multimeter you'd have seen that was way out of whack (with my Oscilloscope I confirmed it clips at 9v, before you see the clip lights turn on).

[Virtue]

So, like I said, don't trust the clipping LEDs. I had a Frank, a Son of Frank, and 2, 2125's and the clipping LEDs were a little misleading. I did the oscilloscope on the output and found that my LEDs were really flickering, even though my signal was clean as a whistle and when I backed off the gains to prevent the clipping LEDs from flickering, my output signal was really low... no output power.

So, are we talking input signals here concerning the 9 volts?

Any which way, as you turn up your Mac500 you will hear the 6.5" distort at higher volumes. That is not the amp distorting, it is actually the 6.5" not being able to move back and forth quickly enough with that kind of power...

[Lance_S]

The 2125 clips now at higher volumes but there is no audible distortion. The lights are just barely blinking. The RK6's are really power hungry. 200W continuous is recommended, they will handle 250 continuous with 500 peak. But they are amazing with power. The doors are heavily deadened. They have to be with those speakers with power behind them. I have read that the mac actually puts out around 200 per channel so that might be a good fit. The 275 running mono into the alumipro will pound it. So I think the mac on the fronts, and the 2125 running mono will be the best package. Because the mac doesn't have the fans that the 2250 has, Alek suggested to keep it at 4 ohms or it will overheat. I have the amps on display with clear plexi so I don't have them cooled and they hang upside down which, of course, doesn't help the cooling. I have twin fans running into and out of the space that they hang so they have cooling from the outside but not the inside like a 2250 would have. I think the alumipro will really have it's hands full with the 2125 running mono and it won't over heat. I don't think I will end up using more than 50 percent of the total capable output of the 2125 in this setup. Though I know I am driving the 275 to it's limit. I have had it shut down on me a couple times from overheat during extended loud play.

Either way, I won't be short on power. And running active, all three amps should have tons of head room as they are only going to output the selected crossover points. The 6 1/2's can run down to 63 hrtz so they will get a workout with the mac.

Should be a fun setup. Once dialed in. I have to play with the crossovers since I am currently running just the 2125 and the 275 but the mac should be here on friday, then it's a re-wire and tune. Once up and running I am going to try and find a local shop that has the equipment to do a real tune with an ascope and computer software to really dial it in.

Thanks for all of the input. I will try and post some pics and reply when it's up.

Lance