pre/pro trim level vs amp gain?

[middleman]

I have a UMC-200 powering a Crown XLS1500 amp bridged for subwoofer duty.  In playing around with things, I've settled on either:  a) the UMC-200's sub output at -2 dB and the Crown's gain at max, or b) the UMC-200 at +0 dB and the Crown's gain down two clicks from max.  Either sounds pretty comparable to my ear, but which is better?

As discussed here, "The level controls on the cleanbox and amp are passive attenuators. Turning them to max (minimum attenuation) increases headroom before clipping and SNR. There is no point in turning them down in this application. Turning them down only decreases the already low signal available from the receiver."

I've determined the UMC-200 has plenty of voltage output to satisfy the Crown's 1.4V sensitivity.  But turning its trim down (-2 dB) potentially cuts into whatever safety margin it's got there.  On the other hand, leaving it at +0 dB and turning the Crown's gain down compromises headroom.  So, which is the best compromise?

It might be purely academic, as I'm not hitting clipping at the loudest levels I care to listen at.  I just like to have things set up to best handle the heaviest demands they might be hit with, e.g., huge movie explosions.

[ttocs]

My limited knowledge of Crown amps is that when bridged, they have more noise. So I would say that whichever settings you use should include reducing the gain of the Crown amp.

As always, there's a sweet spot in there somewhere.

[middleman]

I haven't read that about Crown's producing more noise when bridged, and am looking it up now, but if true would make sense to lower its gain instead of the pre/pro's trim. The only related thing I can think of is a bridged amp produces an extra 6 dB of gain, if I'm not mistaken, which is probably only significant when nearing its power supply limits.

I've found several threads talking about excessive hiss from the Crown XLS amps when running RCA inputs, but I'm running balanced inputs and don't have an issue there.

This might be close to what you're talking about:

www.hifivision.com/threads/considering-a-crown-amp-is-it-the-right-choice.85035/page-2

"One of the issues with Crown is that it has a higher noise floor than the other power amps used for HT/stereo. So, turning up the gain all the way will add a bit of noise and it can be heard if one puts his ear to the speakers. Bridging on the Crown will also raise the noise floor but as I have set the gain to 1 O'Clock, it's not noticable."

[ttocs]

Yeah, that's pretty much what I was referring to, the hiss and higher noise floor. Not saying it's going to be noticeable in every system, but just something to consider. So that's why the suggestion for reducing how much effort the Crown is tasked with vs having something else provide a possibly less noisy gain.

[vcautokid]

I have some crowns and noticed that when I bridge noise is up a smidge. Not crazy, but noticeable. So instead of bridging them I leave them stereo and run vertically for my speakers when I did for bi amping. Now I am running Parasound and repurpose the Crowns.

[middleman]

I just checked in and see I missed a reply(s) notification, sorry.

I haven't run the Crown in stereo, so I don't have any comparison handy, but I can't hear any hiss or other abnormal noises from the sub. When looking for bridged noise stuff yesterday, I actually ran across a surprising thread talking about a Crown (XLS2500, I believe) not stacking up well against higher end pro amps for sub duty, but doing well for full-range use. People are usually on the fence as far as pro amps for the mains, but that sort of fits with vcautokid's comments.

I went back to turning the pre/pro's trim up a bit and the Crown's gain down, as it sounds like that might be ideal and there's no compelling reason not to. It sounds good either way.

[leonski]

Does clipping enter into this discussion anywhere?

What I'm getting at is adjusting to the point that when the vol level is MAX, you are not clipping......

One point here? 'Bridged for subwoofer duty'.....

This I think means it is running where the ear may be least sensitive to some distortions and noise.....

but I could be wrong, there, too.....

Pro amp in home duty? I'm not a big fan, either.....

[sebna]

Jun 19, 2023 13:07:08 GMT -5 leonski said:

One point here? 'Bridged for subwoofer duty'.....

This I think means it is running where the ear may be least sensitive to some distortions and noise.....

but I could be wrong, there, too.....

Pro amp in home duty? I'm not a big fan, either.....

Why would you say that about distortion? Can you elaborate.

In terms of Pro Amps for home duty... it is not really fro home duty but for sub-duty. It is not like we need some incredible fidelity for HT sub and 99% of consumer subs also use class-d to power their drivers... I am pretty sure those neither are of audiophile quality.

[leonski]

A REAL can of worms. And most authors are trying to impress rather than simply state a few facts or principles.

And you sort of support what I'm thinking....when you say....."it is not like we need some incredible fidelity for HT sub"

It is very true that maybe not even the sound editor for many movies knows what a given 'effect' is supposed to sound like.

The 5% distortion at 40hz would be ear bleeding if it happened at 8khz.....

Certain properties of 'D' amps make them problematic for my stereo. The Zobel causes phase shifts at higher frequencies and

limits power handling. Other measures of 'D' amps are pure showmanship.

I'll look around a little and see if I can find a good summary article that doesn't get too deep into the weeds.....

[leonski]

www.axiomaudio.com/blog/distortion


This look simple enough and even I was able to understand the graphics....which tend to support, to some extent, my original thought.....


Please let me know if this helps?

[vcautokid]

Intended purpose of use folks. Will the sky darken, and the oceans rise if you use the Crowns for home use? Absolutely not. Whether it is house of worship, large venue, or the recording studio, or home, the Crowns do fine. They are great for Subwoofer applications because of its built in crossover. The most reliable amplifiers I have owned, and weighs nothing, runs cold as Ice.

It comes down to what you like. I think frankly for me at least for my applications I like the BAS-X A2 better. I am also running Parasound too.

Audiophiles give these amplifiers allot of gas. That is fine. I did a video that talks about my Crowns of which I have 2. I am thinking of putting them back in my theater for more applications like maybe Atmos, not sure.

But it is tough to find a more versatile amplifier for money, and does so well in so many applications. Personal taste, and where you are will determine if the Crowns make sense to you. Certainly not perfect. What is?

Plenty of space for everyone here. Crown can fill that space fine, if it makes sense for you. This may or may not help.

[mgbpuff]

The trouble with pro equipment is that, well it's pro equipment with gain based upon +4db signals instead of -10db for home audio components. I had a problem using two Crown amps to power passive subs controlled through the sub output of an XSP-1. I could not get enough volume to the subs to blend in with the mains. I had to buy a Rolls Promatch box specifically meant for -10db to +4db conversions.

www.amazon.com/ROLLS-MB15b-Promatch-and-More/dp/B0002IL4B4/ref=sr_1_1?crid=86EAKJRJUHHO&keywords=Rolls+Promatch&qid=1688010010&sprefix=rolls+promatch%2Caps%2C102&sr=8-1

[vcautokid]

Well at least Crowns I have still have the RCA at the -10db world, so they play nice with most home consumer gear.

[mgbpuff]

When it comes to mixing pro and consumer audio equipment "Caveat Emptor" applies.