Mackie SRM 450 replace Amp

[Spencerleehorton]

What about this amp delivering 600 watt per side at 8 ohm with that passive cross over?

http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=352135538801&category=14970&pm=1&ds=0&t=1505805441000&ver=0&cspheader=1

Bit more power than needed but could run amp on halfway, or just over right?

Seems like the cheapest option so far for about £200 all in for powering both speakers.

 

[abbey road d enfer]

Bit more power than needed but could run amp on halfway, or just over right?

There is no way to run an amp halfway; the gain potentiometer just changes ...gain, not power.

Seems like the cheapest option so far for about £200 all in for powering both speakers.

I would rather buy a second-hand amp of a reputable manufacturer.

 

[scott2000]

There is no way to run an amp halfway; the gain potentiometer just changes ...gain, not power.

I thought it changed the input going to the amp?????( input sensitivity)  Lowering it's amplification output as a result???? Or are we talking actual power consumption??

I would rather buy a second-hand amp of a reputable manufacturer.

For sure..... Even an old tank like a Crown Micro/Macro/Com Tech would eat any unknown brand for lunch and probably outlast it.....

Or just buy two replacement Mackie amps for a bit more

 

[abbey road d enfer]

I thought it changed the input going to the amp?????( input sensitivity)  Lowering it's amplification output as a result????

If you increase the input signal, the amp is still capable of producing its nominal power. Turning down the pot is not a safe protection against excessive level, unless the attenuation is so great that the source cannot supply anymore signal, but then you would be in very uncomfortable territory, operationally speaking.

 

[scott2000]

If you increase the input signal, the amp is still capable of producing its nominal power. Turning down the pot is not a safe protection against excessive level, unless the attenuation is so great that the source cannot supply anymore signal, but then you would be in very uncomfortable territory, operationally speaking.

Of course.... Makes sense......
Are there advantages in regards to limiting(not limiting but attenuating) the input signal and using an over rated amplifier to stay well in the amp's comfort zones??? I see it brought up quite a bit although, I've never had the opportunity to put it to use...... like using an amp that is rated 4x what you need increases the quality quite drastically by preserving headroom???  Just trying to get my head around the concept....

 

[Spencerleehorton]

This is such a mine field, 450 Watts is the total max watts of both the driver 350 and the horn 100 but some say to have an amp that is over rated ? Some say not?
Could we get a bit more specific please?
If I had a 500 watt amp at 8 ohm with passive crossover would this work?
What max watt amp would work?
Replacement mackie amps would end up costing £500+ for both of these!

 

[abbey road d enfer]

Of course.... Makes sense......
Are there advantages in regards to limiting(not limiting but attenuating) the input signal and using an over rated amplifier to stay well in the amp's comfort zones???

In most professional installs, the amps are all the same and tuned individually to the speaker they drive. Since HF require a higher peak factor than LF, it's a good thing. For HF, the average power is limited but the instant power is not, which is consistent with the requirement for a high peak factor. Attenuating the input of an oversized amp is not a proper solution.

 

[abbey road d enfer]

This is such a mine field, 450 Watts is the total max watts of both the driver 350 and the horn 100 but some say to have an amp that is over rated ?

For HiFi or studio monitoring, yes.

Some say not?

These are PA speakers, where every drop of available power should be put to use.

Could we get a bit more specific please? 

Yes, we could, but your lack of basic technical knowledge regarding power handling of speakers makes it difficult. A proper answer to your questions would need a lengthy analysis of the destructive factors in loudspeakers, but you seem to accept only yes or no answers, such as ...

If I had a 500 watt amp at 8 ohm with passive crossover would this work? 

Yes it would, but you would have to have a x-over tuned to your speakers, solve the EQ issue, and it would still not offer the degree of protection of the original arrangement.

What max watt amp would work? 

Any amp would work (make some noise); with 50W you probably would never have to worry about power handling, with 5kW you would need to seriously control the gas pedal.

 

[scott2000]

This is such a mine field, 450 Watts is the total max watts of both the driver 350 and the horn 100 but some say to have an amp that is over rated ? Some say not?
Could we get a bit more specific please?
If I had a 500 watt amp at 8 ohm with passive crossover would this work?
What max watt amp would work?
Replacement mackie amps would end up costing £500+ for both of these!

I think an amp with around 500watts/channel @ 8ohms would be nice and reasonably safe once you get your crossovers sorted..... and if you add the protection circuits, it should help add to the peace of mind....I think the drivers are rated continuous power so, they will handle a bit of funny business for short periods if that were to happen???

I do  know when I push some of my smaller amps to some speakers that have more power handling than the amp, I find myself wanting to push the amp to it's max sometimes and it sounds pushed...(probably overloading the amp's input too far even though the specs rate it fine,,,,and not good for the drivers to be fed any of the resulting distortion  from what I understand)..  So, 500 watts per channel will be putting you right there and it'll probably sound good enough at pretty good volume???

Like it was mentioned, this set up won't be the same as the engineered plate amps with all of the limiting circuitry and tricks but, I'd be curious to hear what a different approach sounds like in these.

Very interesting......

 

[Spencerleehorton]

Ok, so yes I know it’s frustrating for you to explain this to someone who doesn’t understand all the parameters but I am here to learn and gain a better understanding. As I have for microphones and outboard gear, I am shifting my focus to PA amplifiers and speakers for my live setup.

So we are in agreement that 500watts per side at 8 ohms is good with this x-over from the passive version.
The focus now shifts to the protection circuit?
Has this been covered?

 

[scott2000]

The focus now shifts to the protection circuit?
Has this been covered?

I think 500/side is fine and should sound good and be pretty loud...... If you find you want louder, safer to get additional speakers and amps probably......

Yes.... earlier in the thread the protection circuit was mentioned and the circuit is on the crossover schematic......

From Abbey.......

It's a crowbar protection. When the voltage exceeds a given threshold, the MOSFET turns on, actually shorting the x-over's output.

 

[Spencerleehorton]

Ok great stuff, once I get back from France I’ll mock up the x-over and protection circuit and try out as I have a 500 watt amp.
I’m also looking at building a 500 watt amp as well, so will submit the plans for it including the x-over.

 

[scott2000]

Ok great stuff, once I get back from France I’ll mock up the x-over and protection circuit and try out as I have a 500 watt amp.
I’m also looking at building a 500 watt amp as well, so will submit the plans for it including the x-over.

Awesome!!!

Thanks!

 

[JohnRoberts]

I have avoided this thread so far,,,,  The Mackie powered speaker probably involves a lot of internal EQ and a specialized crossover built in.

You are unlikely to get similar results DIY unless you replicate their processing....

It will be a good learning experience if you keep your expectations modest.

JR

 

[Spencerleehorton]

That’s all this is John!

 

[Spencerleehorton]

I also did wonder about this way:

2 x 350 watt amp at 8 ohm and another 2 x 150 watt amp at 8 ohm, I can get both for about £150 skytech (don’t know if they crap? Probably?)
Skytech do a 1000 watt which at 8 ohms is 350w and 400 watt version which does 150w at 8 ohm. There might be a 300 watt version which does 2 x 100w at 8 ohm?
Is this was a better way to run it or stick with the 2 x 500watt amp for both speakers?

 

[scott2000]

I also did wonder about this way:

2 x 350 watt amp at 8 ohm and another 2 x 150 watt amp at 8 ohm, I can get both for about £150 skytech (don’t know if they crap? Probably?)
Skytech do a 1000 watt which at 8 ohms is 350w and 400 watt version which does 150w at 8 ohm. There might be a 300 watt version which does 2 x 100w at 8 ohm?
Is this was a better way to run it or stick with the 2 x 500watt amp for both speakers?

I've never heard a skytech.....

I guess your after getting as close to the original srm design with the separate amp per driver??? The srm uses two different types of amp topology for the drivers....

I was thinking you were going for the c series set up which is the crossover with a separate power amp of your choice to just power the unit......

I'm thinking that the c series and the srm might have similar drivers and the crossover used in the c series is probably the best option              if running these drivers without the specialized amps that are made for the srm. You're not going to replicate the srm sound as there is limiting, compression, etc going on in the srm amplifiers along with a kajillion 4560s so, I'd just look for enough power in one amp to run the two cabinets once you get the crossovers installed. Or if you're building plate amps, 1 for each cabinet.......

too bad the v2 amp doesn't work for the v1 set up. They're less than $200 usd here for a replacement amp.....

 

[scott2000]

I figured I'd add to this that the C300z crossover works with the Srm450 v1 just fine. and fits where the old amp plates go...

https://www.fullcompass.com/prod/272691-mackie-0012545-crossover-with-input-plate-for-c300z?gclid=EAIaIQobChMIl9_6heW53QIVBTBpCh1yjAFFEAQYASABEgJSdfD_BwE

Only thing is the connector is reversed for the drivers.... Yellow is HF + Blue is LF+...

Just running 300 watts/channel old QSC amp and they sound pretty good..... The 300z crossover is different than the 300 schematics posted earlier and it doesn't have the protection circuitry..... The sound is definitely not as harsh as the original plate amps.... but a bit looser I guess... . I definitely recommend them if you haven't got yours going yet......

 

[Spencerleehorton]

Yes I want to get back on this at some point, will read it all again as I’ve forgotten where I am with it all.
I have 2 speakers here that I could do with re amping so a project worth going forward with.

 

[JMFahey]

I figured I'd add to this that the C300z crossover works with the Srm450 v1 just fine. and fits where the old amp plates go...
https://www.fullcompass.com/prod/272691-mackie-0012545-crossover-with-input-plate-for-c300z?gclid=EAIaIQobChMIl9_6heW53QIVBTBpCh1yjAFFEAQYASABEgJSdfD_BwE

Excellent.

Only thing is the connector is reversed for the drivers.... Yellow is HF + Blue is LF+...

That´s the right way to do it. 
Crossovers shift frequency so much at the crossover point , typically one by minus 90 degrees, the other by plus 90 degrees, that at crossover point thay are 180 degrees from each other ... perfect out of phase, which produces a severe notch at that frequency.
So the practical solution is to invert phase from one of the drivers, and inverting HF is safest option.

Just running 300 watts/channel old QSC amp and they sound pretty good..... The 300z crossover is different than the 300 schematics posted earlier and it doesn't have the protection circuitry..... The sound is definitely not as harsh as the original plate amps.... but a bit looser I guess... . I definitely recommend them if you haven't got yours going yet......

I was chiming in to suggest exactly that.
I live in Argentina where every commercial product is available, Mackie, JBL,you-name-it but because of distance freight is horribly expensive and Customs Tariff is high .... plus going through all the bureaucracy and red tape.
The end result is that commercial products come in (same paperwork to bring 1 or 1000) but **spare parts** do not, so there are many orphan blown amp powered cabinets all over the place.
Standard and very popular solution is to junk unrepairable/unreplaceable original plate amps, close gaping hole with a piece of plywood , and mount 2 speakons and a passive crossover on it, then power the now passive cabinet with some classic Rack mounted power amp, from old but trusty Peavey CS800 to QSC to no name Chinese ones.
Surprisingly end result is quite good.

2 precautions:
1) don´t drive them with more than, say, 250W or 300W (tops) per cabinet.
Original Mackie built in preprocessor has tons of limiters, variable high pass filters, voice coil current sensors (predict voice coil temperature) , etc; NONE of that is present in the oldschool cruder approach.
IF the power amp has an anti-clipping limiter, by all means activate it.
2) since passive crossover has NO protection at all, PLEASE add a car type lightbulb in series with driver.
A 12V 15W one will protect most common drivers, any size.
In the specific case of SRM450 they have a stronger 44mm voice coil which stands more power (not 150W by any means) so you can use a larger lightbulb, a truck type 24V 30W to 45W should do.
Unprotected drivers will die on the first high pitched microphone squeal.

As I said above, passive cabinets sound very good, just don´t ask stupid high SPL out of them.

Here it´s very common to see, at small Rock Festivals (say a neighbourhood one played in the street or a Club by non Pros) some small PA company with, say, 10 to 20 such speakers, mixed brands and models, a veritable salad, bought dead for cheap and recycled.

Let me tell you that 10/20 recycled ones beat the dust off 2 or 4 "original" ones any day of the week