11" Focal 27 V2 subwoofer advice

[buckie]

http://www.sxoc.co.uk/vbb/showthread...ight=enclosure

Firstly thanks for all the replies on the above thread, I took everyones advice and have ditched my 2-way rear speakers.

I now have just my 165 V2 components in the front and have treat myself (funded partly by the sale of my rear speakers) with a Focal 27 V2 sub which should match my front components perfectly.

I was told to stay away from the 8" subs as they are a bit too lightweight and was advised that the 11" size is just the right size for such a small boot and cabin space within the S13's.

I am going to go for a small 15 to 20 litre sealed enclosure as I want a fast and tight bass.........definitely not a ported box.

I have the benefit with this particular sub of having two pairs of connectors for speaker cable. The instruction booklet shows that I can connect using a single amp in 2-channel (stereo) mode, i.e. the left channels positive and negative to one side of the sub ( =4 ohms) and the right channels positive and negative speaker cable to the other side of the sub(again = 4 ohms).

A person from the Focal main dealers has told me I shouldn't connect in this way but the booklet clearly states that I can. I would prefer to connect it in this way as I will get the max power out of my amp which can push out 200Wx2 max and the sub can handle 600W max.

I cannot mono bridge this amp to a x1 format to power a single sub with only one pair of speaker terminals hence why I am keen to wire it up as shown above using both pairs of speaker outputs.

Any advice or comments by fellow ice-heads welcome

[Si]

What you have there my friend is a dual voice coil sub. it's designed to be run from the same source into each coil (i.e. mono). whatever you do do not feed each coil a different signal(i.e. stereo signal) - you run the risk of serious sub and amp damage. Each of the coils will have a resistance and they can be wired together to run from the same source in either series or parallel. You will have to either bridge your amp or run it in mono to use the full power of the sub

Do you know what the resistance of each of the sub coils is (should be written on the sub), and what amp are you using?
EDIT: sorry just re-read your post - so it's a dual 4 ohm sub?

PS cracking sub

[Si]

Just looked on the focal site - it's a dual 4 ohm sub. this means that you can either run the coils in parallel (connect the postitive of one to the postitive of the other, and likewise with the negative) which will show your amp a 2 ohm load, or run the coils in series (run the positive of one coil to the negative of the other coil, and the two other connections to the sub) and show the amp an 8 ohm load.

So you need an amp that can either produce 300w at 2 ohms or 300w at 8 ohms(not many of those around, as that's quite a lot of power)

You say you can't bridge your amp, but you could in theory connect one channel of the amp to each of the coils, but they would need to produce around 150wrms per channel at 4 ohms each, and both channels would have to be run mono. if you don't have a mono/stereo switch on the amp you are going to run into trouble i'm afraid

[buckie]

I have a Maystar QX Series QXT455 amp Spec below

4 ohm: 4 x 50W RMS (400W MAX)
Bridged: 2 x 150W RMS (600W MAX)
2 ohm: 4 x 150W RMS (600W MAX)
Variable 12dB crossovers
Variable 0-18dB bass boost
Induction cooling fan
WRC ready
2 ohm stable
RCA & speaker inputs

Also have an old, but in its day good, Panasonic CY-M1004EN amp. Spec below

4 ohms
2-Channel: 2 x 100W RMS (200W x 2 Max )
4-Channel: 4 x 40W RMS (65W x 4 Max)
102dB signal to noise
Frequency Response: 5Hz - 100,000Hz
Input sensitivity: 200mV

Not bothered which I use to drive the fronts or the Sub but any ideas/recommendations for the best configuration would be welcome.

[buckie]

There is a PDF file that I have tried to download onto here but it's too big.
It shows four different configurations, two of which Midlands_si has mentioned, but there is another two, and one clearly shows one amp using two channels, one going to one pair of inputs on one side of the sub and the other going to the other side. It lists this as 4 ohms per channel and states "connection using 1 ampflifier (stereo)"

[Si]

Sounds a bit strange - it's really not a good idea to send a different signal to each of the coils as if the signal is different on the left and right channels (the whole point of stereo) you could end up with one coil actually working against the other on the same speaker - not good

OK, you could run just one set of RCA's to the amp and split them. Then, if You can bridge the channels, you could run one coil off one pair of channels bridged, and another off the other two bridged, if you see what i mean? the inputs would then be all the same on all channels, providing when you bridged the amp it gives a mono signal (most do)
This way you'd be showing the amp a 4 ohm load from each of the channels, at which the amp would be providing 2x150wrms = 300wrms.

Make sense?

I think that should work in theory, but i'm not 100%

[buckie]

................l---bridged---l..............l---bridged---l
.........+4CH-..........-3CH+.......+2CH-.........-1CH+

The above is what is on my amp. The spec says Bridged : 2 x 150W (RMS) (600W MAX) so if your theory is correct this may be a possibility.

I have four RCA plug sockets on the amp which are simply marked ch1,ch2,ch3 and ch4.

I then have the above configuration for the speaker cable.

Should I run the RCA from my HU SUB output and plug it into ch1 and ch2 and then wire one side of the sub from the 4CH - and 3CH+ slots on the amp and then wire the other side of the sub to the 2CH- and 1CH+ slots. I note I do have a red + and a black - on both the speaker cable terminals on the sub

[Si]

Hang on, genius drawing in a childhood MSPaint stylee on it's way...

EDIT: Here we go, this is what i'm suggesting (Please forgive me, i have the drawing skills of a small boy with leprosy.)

[buckie]

Cheers for that Midlands si, one thing I would like to know, my third RCA out on the rear of my HU is specifically for a sub. It is a pair of RCA plugs which indicate left and right. If this RCA output is tailored for low frequencies to a Sub then will it be in stereo?

[buckie]

I wish I could mono bridge it into 1 single channel to get the full power of this amp to drive my sub but it will only do 2,3,4 channel configuration.

My dealer reckons I should bridge it and run my sub rca from my HU into channels 3 and 4 of the amp and use one pair of cables from this bridged setup into the sub which he recommends I configure in "parallel series" which is to attach + to + and - to - on the two sets of voice coils.He then told me to switch the amp onto channel 3.

I still feel this setup is only using half of the amps power. I just need to know if there is any way I can safely hook up my amp to maximise its total power. I may try Midlands si's theory out but if anyone else has any suggestions it would be welcome.

[Si]

My dealer reckons I should bridge it and run my sub rca from my HU into channels 3 and 4 of the amp and use one pair of cables from this bridged setup into the sub which he recommends I configure in "parallel series" which is to attach + to + and - to - on the two sets of voice coils.He then told me to switch the amp onto channel 3.
.

I REALLY wouldn not do that mate that would be running the coils in parallel and showing the amp a 2 ohm load - that's the problem here, your amp is not 2 ohm stable when bridged, so it would probably overheat and blow You could run one of the coils like that, but not both and it's not really a good idea to only use one coil of a DVC sub.

As for the RCA's from the head unit for the sub - most Head units that have a sub out onyl ut a mono signal into the RCA's for the sub, but have a pair of them - it's a bit strange!

[buckie]

About my amp.....from another website.

"its 2 ohm stable in stereo only 4ohm stable when bridged offcially. My local ice dealer says they have run them at 2 ohm bridged with out problems"

I'm no expert but I realise there is a big difference between it being 2 ohm safe in stereo as opposed to in bridged mode, which is the problem here.

[Si]

Yup, nail on the head mate - generally if an amp is 2 ohm stable stereo, it's stable at double that bridged. As said above - it probably has been done, but you run a big risk with your amp. personally i wouldn't do it, but i'm a very cautious person with things like this!

[buckie]

Been looking at your drawing again Midlands si,

Thinking aloud...I currently drive my current sub with an old Alpine amp which has only two rca outs and is only capable of driving a pair of speakers or bridged in order to drive a sub. I have it configured for the latter at the mo and only the right output (red rca out) is powered in this mode. If this is the case then why is there two rca outs on the HU for the sub, is it for powering a second sub? maybe.

Transfer this to a 4 channel amp and I now have 4 rca outputs instead of two. In bridged mode to power a pair of speakers I assume only 2 RCA's are live and the other two are dead (Don't know which it will be at the mo). One will be for the right and one for the left (I note on your diagram you have front and back but I think it will be left and right.) Now won't these signals be different as one is for the left channel and one for the right ie stereo, which means they will be fed different signals.

That's why I ask if the RCA's specifically designed as a sub out on the rear of the HU is fed a stereo signal. It's the HU rca's that determine whether the signal feeds the front or back speakers isn't it. My rear RCA plugs are currently redundant since I got rid of my rear parcel shelf speakers.

Just found these useful threads

http://mobile.jlaudio.com/support_pages.php?page_id=161

http://mobile.jlaudio.com/support_pages.php?page_id=163

[Si]

The sub outs on most HU's are usually a mono signal - i.e. a merged mono signal, identical in each of the RCA's from that pair. This is certainly the case on my unit
How this is used depends on the amp - most amps still need a pair of inputs, even if they are both the same. My helix still needs both, even for a bridged output Some, however, are happy taking the entire signal from one RCA, and split it internally.

I used front and back as that is for a 4 channel amp, and what i was suggesting you do with your 4 channel.
Bridged, the amp can only go down to a 4 ohm load, that means that each of the pairs of channels could drive a single coil of the sub. i split the RCA's so that identical signals were being sent to both of the coils. You then use both front channels bridged to run one coil, and both rear channels bridged to run the other

I know exatcly what you mean about the head unit giving out a mono signal. however, even if it does, if you follow through the logic of my drawing above, both front and rear channels are receiving the same left channel, and the same right channel. assuming that when the amp is run in bridged mode, it creates a mono signal and runs the sub with this, then you should have no problem, as each of the coils should be shown an identical signal
make sense?

[buckie]

I'm still a bit confused on the "front and back" issue as this is determined by my HU and not my amp. My amp simply has 4 channels and they will be dictated to by whichever RCA I plug into it from the HU.

[Si]

The amp has two sets of imputs - one for the front, one for the back. what you do is take the sub output and split each of the rca's - so the red RCA turns into 2 RCA's - one into the red socket on the front channel of the amp - and the other into the red socket on the rear channel of the amp.
likewise with the white

[buckie]

I'm afraid my amp just has 4 rca inputs two x two (like the four on a dice)
they are all black ........top left ch4, top right ch2, bottom left ch3 and bottom right ch1.

[buckie]

Midlands si.....I have sold my amp and bought an Alpine MRD-M300 mono amp to drive my sub as it is a dedicated amp for a sub and it is definitely 2 ohm stable. One question however, it is 300W x 1 (2ohm 14.4V) and only 200W (2ohm 12V) which is its RMS power rating.
I'm assuming I will be powering it at 12V as it's straight to my car battery. How do you power it at 14.4V, do you need some kind of transformer.

[Si]

14.4v more what the alternator supplies when the car is running although tbh it's usually more like 13.8

A lot of manufacturers quote power at both levels, as amps usually produce more power at higher voltages

Are you ok with wiring the sub? as it's happy to be shown a 2 ohm load, just wire the terminals in parallel, and you'll be fine then sit back and enjoy the sound