[HootisTigglebits]

What amp should I get to improve my hifi audio and mainly get better bass? I was planning on starting with a more powerful amp and see how I like the sound system after the install. How many channels do I need? I'd like to keep the price of the amp below $300 and I don't mind buying used. This is on my 2017 M240i.

[jv92red]

So your budget is $300 or less for a replacement amp and work with the existing speakers and improve the bass? Tall order....

The problem you're up against is the OEM under seat 8" woofers... The under-seat enclosures are not big enough to allow anything but a shallow 8" driver so while there are two of them, they don't do sub-bass well. There are better shallow 8" drivers on the market but the folks that spend the money on those use the underseat drivers as a band passed mid-bass solution for a 3-way front stage, as better bass is really delivered with a sub solution in the back. Can you put better bass focused drivers in the undeseat locations than OEM? Perhaps, but with 4" midrange drivers in the doors you'll find that there will be missing frequency response since 4" midranges don't behave well high passed under 200Hz and subwoofers don't sound good low passed any higher than 70-80Hz.

What would I do with a $300 max budget? I would just replace the front door speakers because if you can find a used 6 channel amp for $300 or less you are still dealing with the OEM drivers.

So for the front doors the HK system allows a seperate tweeter in the sail while or non-HK car does a coaxial in the doors. Both are one channel per door since the tweeters are controlled with a passive x-over.
Here are some new plugnplay sets from a ebay seller to keep costs down. This seller has a 100% feedback rating
For HK you can do separates:
Focal set:
https://www.ebay.com/itm/20300048655...AAAOSw27Zeyi~i
Audison set:
https://www.ebay.com/itm/20327071638...gAAOSwJ0Zgsgm0
For a non HK cars there are coaxials in the doors. You can buy the HK sails and do one of the sets above but that's more money so the coaxials are listed below:
Focal:
https://www.ebay.com/itm/203002561689?hash=item2f43e54499:gRgAAOSwk-NezP50
Audison:
https://www.ebay.com/itm/20348484707...IAAOSwS09gu~aA

If you just want to replace the amp and leave the OEM speakers alone then I would go with this Sony 6 cannel amp:
https://www.sonicelectronix.com/item...XM-GS6DSP.html
Yeah, it's over your budget at $399 but it has DSP built-in so you can tweak the sound out of the OEM drivers. Then when budget allows you can upgrade speakers later. I do believe the current Sony amps can receive Balanced Differential RCA inputs that our head unit puts out, you'll just need a wiring harness. (you can ping Sony support online to confirm)
https://www.ebay.com/itm/16523187293...IAAOSwgQ9V4UKR

Here's one for $240 used on ebay from a 100% rated seller:
https://www.ebay.com/itm/164878407130?epid=23031094996&hash=item266384d5da: gMwAAOSwe99hTXb6

[HootisTigglebits]

Thanks for your input. I purchased the used Sony amp. Should I see an increase in the bass? Currently it feels like there is none even with the bass turned all the way up.

[jv92red]

You can try and dial in more bass with EQ but there is only so much you can do as the factory under-seat drivers just don't have the travel to produce what you're looking for. Bass frequencies need cone area and cone travel to be reproduced properly.

So what I would do with that amp is use it as a 5 channel: two channels for the front stage door speakers (high passed), two channels for the under-seat drivers (band passed), then the 5th and 6th channel is bridged into a 10" or 12" sub that you'll mount in the back either with a custom fiberglass enclosure mounted in the back corner or a self-made or pre-fab sub box. This Sony amp will push 350 watts RMS x 1 bridged at 4 ohms (or 600 watts RMS x 1 bridged at 2 ohms) into your bridged sub channel which is a good amount of power for most SQ subs on the market. Most subs are configured as dual voice coil drivers so a dual 4ohm driver can be wired to a 2ohm load, or a dual 2ohm voice coil can be wired for a 4ohm load.
https://soundcertified.com/how-to-wi...ring-diagrams/

With this set up I think you'll be much happier with the bass and you can squeeze out better response from all of your other speakers using the DSP functions. Dive in on the user manual and learn how to use all of the tools available in the DSP. Download REW, get a mic and have fun tuning.

Oh, I forgot to mention once you get your sub and wire it up like I mention above you'll notice that your rear deck speakers are no longer part of the equation because you'll be using those two channels bridged for your sub and you still aren't able to run a proper center channel. That's because of a few reasons: 1) you don't have enough channels in your amp/DSP to properly drive and process rear fill. Running rear deck speakers pulls the sound stage back behind you if not processed properly (Properly=using time alignment and level control). You want your front sound stage as far forward as possible. 2) No extra channel for your center channel to drive and process it properly so it doesn't ruin your stereo imaging. Proper center channel processing requires using the DSP to send center information to your center channel, not a mono signal or "summed" right and left signal like the stock amp does. (I'm assuming you already disconnected the center channel right? This was the first mod all of us 2 series owners do)

[HootisTigglebits]

Thank you. My last 2 series had HK audio and once I coded the eq to F45 I loved the amount of bass it had so I want to stay with the under seat subs and if need be upgrade them to some used HK's. So with that information what would you recommend? Also what all will I need to install the sony amp? I've done a few amp installs in the past, but it was in vehicles that didn't have a factory amp.

[jv92red]

"coding" to F45 is just a BMW factory preset EQ curve. You'll have more control over the response curve controlling EQ with the built-in EQ on the Sony amp.

So the Sony amp will have 3 sets of RCA inputs: front, rear and sub:
https://images.sonicelectronix.com/i...g/xmgs6dsp.jpg
The wiring harness (more on that below) only outputs 4 RCA channels (front L+R and Rear L+R) so you'll need 2x RCA Y connectors (1 female to 2 male configuration) to split one of the RCA sets to 4 to get a total of 6 channels.
https://www.amazon.com/ROCKRIX-Femal...16&sr=1-8&th=1
I say "one of the RCA sets" because which set depends on how you want to fade the speakers. If you want to fade the underseat subs in and out separately from the front and deck speakers you'll split the front RCA's to the amp's front and mid inputs. If you want to fade the front speakers separately from the back deck and underseat speakers then you'll split the rear RCA's to the amp's rear and sub inputs.

Regarding the wiring harness, you'll need this to bypass the factory amp and to provide the wiring needed to hook up the Sony amp. To my knowledge there are two different options:

Technic harness:
https://technicpnp.com/product/7ch-h...hk674-harness/

or there is a seller on ebay (73mustangconv) who has one without the relay for $5 less:
https://www.ebay.com/itm/16523187293...IAAOSwgQ9V4UKR
Don't get the $35 basic version. You'll want the $68 "deluxe" version which has the factory 7 speaker channels. (center channel connector won't be used) Don't get the optional relay. I actually prefer the one on eBay over the Technic version because it doesn't have a relay and looks to have better RCA connectors. You don't need a relay to turn on just one amp. That sony amp will probably pull less than 50miliamps of power from your remote wire. That Bosch style relay pictured in the Technic harness uses male spade connectors, not solder connectors so that tells me it's at least a 30 amp or 40 amp relay. Those relays pull 150 to 200 milliamps from the remote line just to energize thier internal coil which is WAY more than the 50 or less milliamps your Sony amp will be pulling from the OEM remote line so there is no point in it. If you were running led lights and fans then I would say go ahead with the relay but then I would make sure you have a quenching diode wired on it or run better yet a solid-state relay but that's a whole other topic.

[HootisTigglebits]

Thanks! What's the difference in the $10 and $17 RCA splitters? I'll want to fade the under seat subs separately from the other speakers.

[jv92red]

Looks like the $17 ones are Nickel plated. Not sure it would matter either way. But I just linked those as an example. Any other brand would do I'm sure. What's more important is that you buy the correct length for your install. Depending on where you mount the amp you may need a few feet or you'll need 10 foot lengths.

[HootisTigglebits]

Originally Posted by jv92red

Looks like the $17 ones are Nickel plated. Not sure it would matter either way. But I just linked those as an example. Any other brand would do I'm sure. What's more important is that you buy the correct length for your install. Depending on where you mount the amp you may need a few feet or you'll need 10 foot lengths.

Im hoping the aMp will fit where the factory one is located.

[HootisTigglebits]

The amp arrived today. Will I need to buy plugs for these?

[jv92red]

The amp comes with these plugs:
https://images.sonicelectronix.com/i...g/xmgs6dsp.jpg

If you bought your amp used then ask the seller for them.

If the seller doesn't have them then you can try to contact Sony support and buy them direct from Sony?

EDIT: If you do have to buy these and can buy them piece by piece then don't bother with the "High-Level Input" harness as that one won't be needed. You'll need the other two

[HootisTigglebits]

I bought a set of plugs and pins from a place that sells all kinds of electronics.

[jklaz]

Originally Posted by HootisTigglebits

I bought a set of plugs and pins from a place that sells all kinds of electronics.

Hate to bring up an older thread but I don't have the ability to send PMs yet. Did you end up hooking this all up? Is it a fit in the stock location? Looking to do something similar but don't want to spend 1k on an amp

[HootisTigglebits]

Originally Posted by jklaz

Hate to bring up an older thread but I don't have the ability to send PMs yet. Did you end up hooking this all up? Is it a fit in the stock location? Looking to do something similar but don't want to spend 1k on an amp

Yes it has been hooked up since March without any issues. I bought HK speakers off AliExpress and that saved a lot. The subs came out of a car with under 1,000 miles. To mount the amp is removed the bottom piece off of the factory amp and bolted it to the Sony amp. Then I wired it all up and put it where the original one was.

[Ahorowitz]

Originally Posted by HootisTigglebits

Yes it has been hooked up since March without any issues. I bought HK speakers off AliExpress and that saved a lot. The subs came out of a car with under 1,000 miles. To mount the amp is removed the bottom piece off of the factory amp and bolted it to the Sony amp. Then I wired it all up and put it where the original one was.

I just also bought the used Sony amp on eBay and the eBay harness. HootisTigglebits how exactly did you wore it in? There seem to be a lot of choices. Thanks

[Ahorowitz]

A few more questions: the Sony amp only does DSP with two channel input. Is there anything wrong with only hooking up the front input channels from the technic harness and using DSP?

What voltage are the BMW hifi input channels?

[jv92red]

Originally Posted by Ahorowitz

A few more questions: the Sony amp only does DSP with two channel input. Is there anything wrong with only hooking up the front input channels from the technic harness and using DSP?

What voltage are the BMW hifi input channels?

If your talking about the XM-GS6DSP it has six channel input, not two: Front L&R, Rear L&R, Sub L&R



I believe the factory wiring harness RCA out voltage is 2 volts but I may be wrong. The Sony XM-GS6DSP has an input sensitivity range from .6 to 6 volts so you're fine.