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Kevin, xti4000 bridged for subs?


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#1 glenn0

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Posted 03 October 2011 - 07:55 AM

Kevin how do you feel about using 2 xti4000 amps bridged to power a pair of srx728s subs, one amp per sub???

#2 Kevin Heber

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Posted 03 October 2011 - 08:37 AM

It will work but is the bare minimum amp power.

Better, but much more expensive, would be two 6002's  (driven with a Driverack PA+ to manage power) or a single MAi9000 or iT9000HD.

#3 glenn0

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Posted 03 October 2011 - 08:49 AM

I'm confused, I thought that bridged at 4 ohms, that the xti 4000 puts out 3200 watts, this is the bare minimum for the JBL 728 subs?.



QUOTE(Kevin Heber @ Oct 3 2011, 09:37 AM) View Post
It will work but is the bare minimum amp power.

Better, but much more expensive, would be two 6002's  (driven with a Driverack PA+ to manage power) or a single MAi9000 or iT9000HD.



#4 Kevin Heber

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Posted 03 October 2011 - 01:52 PM

3200W is the recommended power, and 4-ohm/bridged is the most demanding load these amps will tolerate.  It's like hauling a large trailer up a mountain with a sedan.

#5 dakos

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Posted 04 October 2011 - 03:39 AM

Dear glenn0,
Every kind of music needs a bit of "Amp headroom" for peaks in the music, that number ranges from a minimal +3db (two times the wattage) for the most compressed coffee house music, up to +24db for uncompressed live band shows. Most amps have almost no headroom built in them (i-tech/HD and MA-i's excluded) while speakers do, that's why you need an amp at least twice as powerful as your speakers, especially for sub duty, that's why a couple of 4000/4002 are not a good match for two 728's and the 6000/6002 are better. Despite the i-tech's haveing a bit of headroom built in them for those peaks, I'm not sure a single the 9000HD is better, I think a single 8000 or the 12000 just might be enough.
For a single amp application you need to connect the two 728's to get 8 ohms total and then you need 6400W plus a bit of headroom to run it all,

The 9000HD will give you 7000W at 8 ohm bridged.
The 8000 will give you 8000W at 8 ohm bridged.
The 12000HD will give you 9000W at 8 ohm bridged.
They all have a little extra headroom built into them.

For a two  amp configuration, you need to connect each of the 728's to a single bridged amp at 4 ohms each so you need at least 3200W from each amp plus the headroom,
Two 6000/6002 will give you a total 12000W at 4 ohm bridged total.
Two 4000/4002 will give you a total 6400W at 4 ohm bridged total. On this configuration you have almost no amp headroom.

The headroom is also the reason working with a compressor such as the DRPA+ would be advised since it would compress the peaks in the music to a reasonable level so the amp and speakers would be able to handle without the amp clipping or putting the speakers into over excursion.

IMHO for the best $$$ for Watts, I suggest you try to get a used i-tech 8000, they run for about $1700-$2000. Next runner up is the 2X6002, they are about $1525 each on eBay, you will get all the power you need + the headroom for the subs to sound great. Using DRPA+, even the DRPX would suffice for your application, is extremely wise!!

Kevin, please correct me if I'm wrong...

#6 glenn0

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Posted 05 October 2011 - 11:24 AM

Thanks Kevin,  I took your advice and bought the MA9000i for my subs.  I'll let you know how it all works out.

quote name='Kevin Heber' date='Oct 3 2011, 02:52 PM' post='15230']
3200W is the recommended power, and 4-ohm/bridged is the most demanding load these amps will tolerate.  It's like hauling a large trailer up a mountain with a sedan.
[/quote]


#7 glenn0

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Posted 05 October 2011 - 11:39 AM

Thanks ndakos, good stuff.  I purchased the MA9000i before I saw your post so I'm kinda committed at this point.  Hope you agree with Kevin that this will do nicely, 3500 watts per side into 4ohms. Byt he way what do you think of a single xti 6000 powering a pair of JBL 725 tops??

quote name='dakos' date='Oct 4 2011, 04:39 AM' post='15237']
Dear glenn0,
Every kind of music needs a bit of "Amp headroom" for peaks in the music, that number ranges from a minimal +3db (two times the wattage) for the most compressed coffee house music, up to +24db for uncompressed live band shows. Amps have almost no headroom built in them while speakers do, that's why you need an amp at least twice as powerful as your speakers, especially for sub duty, that's why a couple of 4000/4002 are not a good match for two 728's and the 6000/6002 are better. Despite the i-tech's haveing a bit of headroom built in them for those peaks, I'm not sure a single the 9000HD is better, I think a single 8000 or the 12000 just might be enough.
For a single amp application you need to connect the two 728's to get 8 ohms total and then you need 6400W plus a bit of headroom to run it all,

The 9000HD will give you 7000W at 8 ohm bridged.
The 8000 will give you 8000W at 8 ohm bridged.
The 12000HD will give you 9000W at 8 ohm bridged.
They all have a little extra headroom built into them.

For a two  amp configuration, you need to connect each of the 728's to a single bridged amp at 4 ohms each so you need at least 3200W from each amp plus the headroom,
Two 6000/6002 will give you a total 12000W at 4 ohm bridged total.
Two 4000/4002 will give you a total 6400W at 4 ohm bridged total. On this configuration you have almost no amp headroom.

The headroom is also the reason working with a compressor such as the DRPA+ would be advised since it would compress the peaks in the music to a reasonable level so the amp and speakers would be able to handle without the amp clipping or putting the speakers into over excursion.

IMHO for the best $$$ for Watts, I suggest you try to get a used i-tech 8000, they run for about $1700-$2000. Next runner up is the 2X6002, they are about $1525 each on eBay, you will get all the power you need + the headroom for the subs to sound great. Using DRPA+, even the DRPX would suffice for your application, is extremely wise!!

Kevin, please correct me if I'm wrong...
[/quote]


#8 dakos

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Posted 05 October 2011 - 12:10 PM

QUOTE(glenn0 @ Oct 5 2011, 11:39 AM) View Post
Thanks ndakos, good stuff.  I purchased the MA9000i before I saw your post so I'm kinda committed at this point.  Hope you agree with Kevin that this will do nicely, 3500 watts per side into 4ohms. Byt he way what do you think of a single xti 6000 powering a pair of JBL 725 tops??


Dear glenn0,
I cannot disagree with Kevin since he has so much more experience then I do!! if he says it's a good match I believe he personally heard and knows it's a good fit.

Since the 725's are 4 ohm, 2400W (program) per speaker, and the 6000 has "only" 2100W per side at 4 ohms without allot of amp headroom, I believe here too you are a little under powered but please let Kevin approve what I'm saying before you go buying another amp.

I would put the MA9000i (Great amp if you ask me) on the 725's and I would get another MA12000i for the subs... for the best sounding system. This option means you need to sell the XTI, they run for about $1000 on eBay.
Another (much cheaper) option would be to get two XTI 6000/6002 and run the subs of the two XTI's and the 725's of the MA9000i. Still very solid system with great sound.

What do you use for processing? how are you tuning everything?

#9 glenn0

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Posted 05 October 2011 - 01:12 PM

I have a older (three years) entry level drive rack. I use as much of the manufacturer recommended timings that my drive rack will allow.

What do you use for processing? how are you tuning everything?
[/quote]


#10 dakos

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Posted 05 October 2011 - 03:56 PM

QUOTE(glenn0 @ Oct 5 2011, 01:12 PM) View Post
I have a older (three years) entry level drive rack. I use as much of the manufacturer recommended timings that my drive rack will allow.


Well, if you go with another MA-i then resolution wise the DRPA will be your week link. The BSS FDS-366T is an audible upgrade with 96khz/24bit sampling Vs the 48khz/24bit of the DRPA (which is like running the sound through an mp3 encoder and then playing it) and a few other great features, the BSS doe's lack the RTA the DRPA has. Do you play allot indoors? Do you use the DRPA's RTA?

If you stick with using the XTI's the DRPA will have no sonic downgrading effect.

#11 Mctwins

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Posted 06 October 2011 - 02:41 AM

Hi

I would go with MAI5000 for the tops. The PA is moore than enough and gets the job done, the dbx 260 is another option. But that's my opinion.

Thanks



#12 dakos

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Posted 06 October 2011 - 02:57 AM

QUOTE(Mctwins @ Oct 6 2011, 02:41 AM) View Post
Hi

I would go with MAI5000 for the tops. The PA is moore than enough and gets the job done, the dbx 260 is another option. But that's my opinion.

Thanks


At least from the specs alone, the MA5000i has 2500W per side @4ohms, the 725's require 2400W per channel so I have to agree, it's a good option as well smile.gif I still think the MA12000i is the better option though.

The DR260 has more options then DRPA and it sounds a little better but it still shares the same low sampling rate of 48khz, if he will buy the MA5000i or the MA12000i there won't be as much gain from changing the DRPA to DR260, it would still be his week link!!!

IMHO The better choice would be to get a unit that is on par with the rest of his system such as a step up to the BSS FDS-366T unless he is using the RTA, DRXX's RTA is more needed indoors that's why I asked glenn0 what is the major usage of the system.

glenn0, if you can go to the shop and listen to the two-three options that are discussed here it would be the wisest thing to do.

#13 Mctwins

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Posted 06 October 2011 - 06:23 AM

Off course, what you say is not wrong either, but I feel that one MAI5000 is enough. Will get twice the rating on both units and plenty of headroom, depends what the system is used for, off course.
It will be more balanced as well.

If the sampling is imported why not dbx4800. BSS is also a good one.
I think that there is settings for these speaker in dbx from JBL.
Thanks

#14 dakos

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Posted 06 October 2011 - 07:02 AM

QUOTE(Mctwins @ Oct 6 2011, 06:23 AM) View Post
Off course, what you say is not wrong either, but I feel that one MAI5000 is enough. Will get twice the rating on both units and plenty of headroom, depends what the system is used for, off course.
It will be more balanced as well.

If the sampling is imported why not dbx4800. BSS is also a good one.
I think that there is settings for these speaker in dbx from JBL.
Thanks


The 5000 has 2500W per side at 4 ohms, just a 100W more then what the 725's need (Kevin uses program power rating for speakers and subs). He will also end up using the 9000 o the subs which is just 300W more then the 728's need, I'm not sure if you even need to use a limiter for such a small gap. That's why I suggested he should go with the 12000 for the subs and use the 9000 he just bought for the 725's. This way you get a little more headroom on both amps and not maxing the system all the time.

As for the BSS, I was looking for something with the same quality as the 4800 with a fewer channels thinking it would be a little cheaper, I didn't know it was so expensive, I only looked on eBay and they run for about $1000 and a used 4800 is harder to find, when you buy them new they are almost the same. Anyway we both agree it's the next upgrade to come :-)

#15 Jon Cooper

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Posted 11 October 2011 - 01:53 AM

Hey guys. Glad to be here. My question is why should you use a separate OmniDrive if the iTech's have one built in? Thanks