16 replies to this topic

[Falc]

if a 4 channel amp had a T.H.D spec of 0.02 @4 ohm will the T.H.D. become crapty when you bridge 2 channels to make it a 2 channel amp? I cannot find the T.H.D. specs listed for 2ohm loads but lets assume it's 0.2% for 2ohm loads will the bridged T.H.D. be 0.2% into a 4 ohm load?

Also what is a good seperation factor for a entry level comp SQ amp?

[~thematt~]

Total Harmonic Distortion will tend to rise as you bridge down, yes.

However, if you can hear THD below 1%, Ill need you to tune my car

THD is the spec quoted, but its not even the most audible of all the distortions. Ignore it.

Seperation factors generally wont be more then around 60dB for high-end amps. Its another one of those specs that dont mean a thing when starting or upgrading a decent system. People who are after strict seperation choose dual monoblocks (2-channel amps with dual power supplies) or run amps per side (one for left and one for right).

On my list of important things to look for in an amp, THD and Seperation rate right up there with ability to blow bubbles and draw cartoons.

My list is as follows (no particular order)
-Build Quality - Have a look at the guts. Is it a logical flow, or is it haphazard?
-How stable is it? What is its lowest rating?
-What is its power ratings into the drivers Im using (CEA2006 ratings only)? Does it have the power supply capable?
-What does it look like? Does it match everything else I have?
-Price. Is it too cheap for its 'claimed' figures? Indicates corners cut in manufacture. Pay peanuts, get monkeys.
-Does it have any 'special' bits of gear that are unique to that brand? Why? Do I need them, or just want them?

[Falc]

thanks for that, I'll post up my situation tonight

[DG Phil]

~thematt~, on Jan 5 2007, 11:40 PM, said:

However, if you can hear THD below 1%, Ill need you to tune my car

Hallelujah!!!

I used to have arguements with customers who were worried that one CD player had 0.005%THD and the other 0.007% THD.

When I played a test CD with the same track recorded at increasing distortion levels. a lot of the time it would get to 10% before most people picked it.

Maybe it's because I wasn't using $3000 directional RCAs.

Phil

Edited by DD Phil, 06 January 2007 - 09:25 AM.

[~thematt~]

DD Phil, on Jan 6 2007, 08:25 AM, said:

Maybe it's because I wasn't using $3000 directional RCAs.

But now you know your problem Phil, so you can now go and do something about it!!!

[DG Phil]

~thematt~, on Jan 6 2007, 10:14 AM, said:

But now you know your problem Phil, so you can now go and do something about it!!!

But I'm broke after buying my $50k speaker cables.

Phil

[mad89]

DD Phil, on Jan 6 2007, 04:49 PM, said:

But I'm broke after buying my $50k speaker cables.

Phil

that are also directional!

- mad89

[DG Phil]

I'm saving for some special spikes for my home CD player as we speak.

Phil

[~thematt~]

Just remember to cover ALL the internals with a special 'sound deadning' glue. Its very important. Especially all the moving parts, to stop them from vibrating.....

[Falc]

Ok, thanks for the info.

do you think its worth me getting another 4 channel amp (a crossfire 404 specifically) so that I can bridge all the channels effectively giving me 4 channels each with seperate gains, and at least 150WRMS to each speaker.

I dont need anywhere near that power for my system as I want SQ not SPL, but I figure that if your not working the amp as hard you wont have any distortion/clipping ect.

Do I have the right idea?

The new system will be
-Alpine headunit with bass engine pro, 9855R most likely
-Peerless HDS 6.5" mids
-Vifa XT25 tweeters
-At least the alpine 3554 4 channel amp, maybe the crossfire 404 as well
-Boston G2 12" sub
-Crossfire 602 Class A/B sub amp

I have bought or ordered all but the headunit, and sold off my current headunit, splits and front stage amp.

I plan on competing in CAASQWA

Links
Crossfire amps (602, 404)- http://www.crossfirecaraudio.com/frameset.asp (tech info>amplifiers>class AB)
Alpine -http://ampguts.realmofexcursion.com/Alpine_3554/
Alpine 9855R- Alpine.com.au (search)

[~thematt~]

You can get the crossfire to replace your Alpine, but you dont need it in addition to. Overkill and wastage of money. Better off investing in Phils fancy cables and speaker spikes.

You have all the power you need to maintain linearity, dynamics, clarity and headroom. More is just wasted, because it really wont be used.

[Falc]

~thematt~, on Jan 6 2007, 07:00 PM, said:

You can get the crossfire to replace your Alpine, but you dont need it in addition to. Overkill and wastage of money. Better off investing in Phils fancy cables and speaker spikes.

You have all the power you need to maintain linearity, dynamics, clarity and headroom. More is just wasted, because it really wont be used.

ok and the specs on the crossfire are good enough for competition use?

[~thematt~]

Does it play music?

'being good enough for competition' isnt what you should be designing your system for. You should be designing it for your pleasure, nothing more. And the crossfire is perfectly fine for that.

That being said, seeing as I may be some of your 'competition', Id say No

[Falc]

~thematt~, on Jan 6 2007, 08:43 PM, said:

Does it play music?

'being good enough for competition' isnt what you should be designing your system for. You should be designing it for your pleasure, nothing more. And the crossfire is perfectly fine for that.

That being said, seeing as I may be some of your 'competition', Id say No

I've seen your car in the flesh and if it sounds half as good as the setup looks we wont be competition

I say good enough for competition because competition spec is a benchmark for clarity, I wont care if I LOVE my sysstem yet dont place well in a comp, but I see the competition as a way of getting useful feedback and the factor to keep striving to get the most out of my system.

Cheers for your help

[~thematt~]

Thats a fair pursuit. Also the main reason I intend to enter. Progression and continuously improving.

Crossfire amps arent bad, they certainly do produce some decent power, but I havent heard any myself to determine whether or not I could consider them sufficient SQ material for my tastes.

I have an amp with approx the same specs, and Ive bridged it to my midbass. Personally (just my opinion), but if you were to get an amp such as that one, it would be best NOT bridging the channels and just running all 4. If its anything similar to my SRx4, the bridged channels actually muddy up the midbass quite a lot. Not favourable for accuracy.