Bi-amping or not?

[willeywilson]

Hi, I have been meaning to do my install for a while but keep putting it off.

I have a JBL GT5 A604, 4 channel amp, a set of EDGE components that come with 2 crossovers, and a FLI trap "1000w" sub amp package that I bought for about 5 pence of my cousin, so I may aswell use it although I dont expect too much from it. The FLI comes with a monoblock 250w amp which I plan to run the sub off of, inside a custom enclosure in the wheel well. I already have the specs I need to build it so shouldnt be too much trouble.

However, to my question... I plan to amp the front speakers using my JBL amp. I have had a quick look at passive and active / Bi-amping and wondered whether or not it would be sensible to use the crossover provided with the components AFTER amplifying the signal, as is traditional. Or to move the crossover to the boot and use it BEFORE amping the signal then run four cables instead of two to each of the front doors. What are the advantages of either, besides more cable? Especially as my amp has somewhat of a remedial crossover built in. As the amp is 4 channel I thought I may aswell use them all and go down the Bi-amping route:devil:, using the front input for the left door and the rear input for the right door, but obviously using the correct feeds.
BTW I will also be using a line level converter as I want to keep my Blue and Me and standard head unit. This will be connected up to the existing wiring for the factory sub, although it never came with one.

Thanks
Adam

 

[volxstu]

it would be good to have a look at your amp to see what it is really capable. If im correct you are not suggesting going fully ative as you will still passivly x-over the signal due to the limitations of your head unit and amp?
As for the advantages of doing this!!! Who knows, there are massive advantages to be had by going active and having more control over each speaker. I have never really seen anybody passivly filtering a high level signal to stop the amp geting, therefore only puting certain signals. At the end of the day it may be complex to work out which wire go's where on the high level input. perhaps using a high to low level converter might help. Also you aught to consider how you will be able to control L and R. The point of active is having that contro to even up the sound and center the stage.

 

[willeywilson]

Thanks for the reply Stu, yes I will be using a line level converter, coming of the factory sub feeds in the boot.
However, the crossovers that came with the speakers aren't adjustable, although I haven't had a look inside them yet. And the crossovers in the amp are a simple screw that says 32hz at 7o'clock and 320hz at 5o'clock. So these limitations seem to undo all the work i would be doing by using them in an active setup anyway, don't you think?
I would also control left and right by using the front and rear amp divide. As I won't be amping the the speakers. But as I say, there wouldn't be much point as the only thing I can control is frequency, gain and bass boost of front and rear (left and right) which should probably be the same. It would only be sensible to do this if i had better crossovers with more control, although I have read active setups have better sound quality. Although cheap budget speakers won't help.

 

[willeywilson]

P.s. this is my amp http://www.jbl.com/EN-US/Products/Pages/ProductDetails.aspx?PID=GT5-A604

 

[volxstu]

I forgot to say i will answer but im so tired my brain isnt in gear ATM. If i forget then drop me a PM.

 

[volxstu]

I think it will work if you use 4 channel input converters. then you can put the one that takes the mid signal on one side of your amp and the high on another. I think it is as simple as that. Then you will ultimately have control of the gain and shoukd have better quality sound.
Its a shame you dont want to change your head unit. This would be far easier.

 

[willeywilson]

I agree it would be a hell of a lot easier. Although if I change my HU then I would want one of the double din, car-pc type headunits that Pioneer offer. This would mean doing some damage to the dash getting it to fit. Hence me just sticking with the crappy standard one.

As for using the 4 channel converter, could this not be overcome by using the crossovers before the amp, as then the amp would be recieving high and mid feeds?

 

[volxstu]

Alpine do a lot of solutions around this with hideaway brains and motorised single DIN screens. If you know exactly what is what then you can get change for £300 on the second hand market. I can find out somebody in the know if you want me to. An aftermarket solution seems to be exactly what you need.

 

[willeywilson]

It does... but at this moment in time i just cant justify buying one. I'm saving for a project car at the same time as doing small things to the Punto and being a student it's fair to say, I am skint.

 

[volxstu]

But a HU can last between cars. Speakers not so much. Also a half decent HU with no dvd ETC can be had for pennies.

 

[Shadeyman]

I'm not very "clued up" with ICE but I do appreciate High End Home Audio so understand the advantages that can be gained when using Channel Seperation by Bi-amping and Bi-wiring, it eliminates "crosstalk", I use the horrizontal method at the moment but I'm thinking about swopping to the vertical method.

Do the same rules apply with ICE?

 

[volxstu]

Not strictly as you are in such close proximity in car. We tend to use on/off axis although i may have got the wrong end of the stick.
When running active we have control of the Time Alignment/phasing of each speaker so can add delay both horizontally and vertically to home the stage centre. And also drag the sub forward so you dont hear it coming from behind you.
I actually almost managed to get this spot on the other day. Drums and kick bass were coming from the middle of the bonnet. Vocals eye level just in front of the windscreen dead center. left/ right were just outside the car etc etc. Then i messed it all up. Went to my computer to recall the last saved settings and the bloody things didnt save. So its back to the drawing board

 

[Shadeyman]

Not strictly as you are in such close proximity in car. We tend to use on/off axis although i may have got the wrong end of the stick.
When running active we have control of the Time Alignment/phasing of each speaker so can add delay both horizontally and vertically to home the stage centre. And also drag the sub forward so you dont hear it coming from behind you.
I actually almost managed to get this spot on the other day. Drums and kick bass were coming from the middle of the bonnet. Vocals eye level just in front of the windscreen dead center. left/ right were just outside the car etc etc. Then i messed it all up. Went to my computer to recall the last saved settings and the bloody things didnt save. So its back to the drawing board

I think understand.

ICE uses channel seperation(time delay) to control the sound stage and center it around the user.

Home Audio uses channel seperation to improve the overall quality of the sound the system produces. Although my home system is Bi-amped and Bi-wired I'm not fully convinced of any improvements in sound quality. However there is a huge increase in useable power.

Have a read of the attached PDF document.

 

[Shadeyman]

Bi-amping explained....

Bi-amping is the technique whereby two power amplifiers are used to improve the sound quality of a loudspeaker that can be bi-amped.

Monoblocs (used for ICE I think?)

The simplest form of bi-amping is to use two monobloc amplifiers, one for the left channel and one for the right channel. Most mono amplifiers will have higher power outputs per channel than their stereo equivalent. This has the benefit of having more power on tap than by using one stereo amplifier, as well as reducing the ‘crosstalk’ that occurs when both left and right channels are housed in the same box.

Vertical stereo bi-amping

The preferred method of bi-amping is vertical stereo bi-amping. This is when two identical stereo power amplifiers are used, one for the left speaker and one for the right speaker.

If we consider just the left speaker and amplifier, one channel is used to drive the high frequencies and one is used to drive the bass frequencies. The same, of course, applies to the right speaker and amplifier.

To analyse why this works so effectively, we need to appreciate that the load characteristics of the tweeter and woofer are very different. The woofer requires a large current and if driven with a single channel of power amplifier, a heavy bass transient can absorb all of the available current, causing the amplifier to clip and distort. By separating the current to the tweeter and woofer, we are apportioning the power with a more equitable split – thereby allowing the amplifier much more ‘headroom’.

Horizontal stereo bi-amping

This is when two stereo amplifiers are used with one amplifier driving both left and right tweeters, the other driving both left and right woofers.

Whilst this configuration will offer a performance advantage over using just one stereo power amplifier, because of the increased total current available, the amplifier driving both woofer channels will be working much harder then the one driving both tweeter channels – this will mean the bass will bottom out faster under heavy transients than it would if a vertical orientation were used – also crosstalk between amplifier channels is the same or worse than it would be with a single stereo amplifier

 

[volxstu]

Ahh im with you. I am using effectively 1 amp per speaker and our speakers are not full range cabinets with multiple speakers in. In an ideal world you want for example 1 channel for Left Tweeter 1 channel for Right Tweeter and Active x-over for both, same with Mid Range and same with Mid Bass and Mono for Subwoofer.
This way we can change the x-overs, graphic equalisers and "time delay". This is when you will start to get improvements in quality. Once your speakers start to harmonise in time then you will start to notice the Detail and image. Push one part of the sound out and you will loose that Harmonisation and create mess. The mess is distracting so the frequencies you want can get lost.

 

[volxstu]

I forgot to say i will be competing in my first ever EMMA comp on 20th march.
http://emma-uk.net/
I will do a thread in the events section when i get a chance but if anybody fancies popping in and having a listen to the best sounding cars in the country then please do.

 

[Shadeyman]

Milton Keynes, I fancy that, see ya there.

 

[volxstu]

Cool will be good to see people. I will be the one with the Bright red Stilo :devil: