Fitting speakers to the cubbies for those with basic hi-fi...

[ph001]

Ok, decided I'd like to get a better soundstage from the rear of the Z4 so looking at fitting something in the cubby holes. I had already bought a good amp (Hertz HCP 2X) which I plan to mount on the rear bulkhead in the boot and some decent 6x9" Hertz HCX 690
3-way coaxials but unfortunately the speakers don't fit.

I don't want a box in the boot and I tend to have my seats all the way back so I think the cubbies are the only real option for me. This leads me to two questions:

1) The carver subs of the oem DSP systems are 6" (150mm) I believe, which is a bit of an unusual size. What speakers have people fitted to the cubbies that DEFINITELY go in OK. I have a feeling that a lot of 6.5" stuff will be ever so slightly too big. This leaves 5.25" (13cm) but they all seem a bit weedy. Ideally I'd just like to buy the OEM baffle plates from BMW but I think these will be cut for a 6" driver?

2) Can anybody say with certainty if the oem 4" speakers in the rears receive a full range signal or not? I'm expecting the wiring to be full range and maybe they just have a small cap in series locally to block the <100Hz stuff?? It's very convenient to pull the audio signal from these wires, especially as the amp has a remote on (speaker signal detect).

 

[Z4 Gaz]

Why would the 6x9 not fit?
I fitted these Kenwoods, that had a ruddy great magnet, followed by some JBL that are currently in there. Mounted on marine ply, 18m IIRC.

 

[ph001]

I think it’s maybe because i’m using aluminium plate for the baffle rather than mdf. The plate is only 3mm thick so I guess it puts the speaker chassis closer.

I’ll buy some mdf and see if that works.

 

[ph001]

Ok, did a template out of MDF. They won't go in

Seems like the HCX 690 are closer to 7" x 10". Bloody shame as they are great speakers but they will have to go on Ebay. Looking around for some decent component 6.5".

 

[MrPT]

Why do you want a better rear soundstage? Are you watching Saving Private Ryan on the satnav or something?

Seriously though, why not a dedicated, long-throw set of bass drivers and an upgrade of the front 2/3-way set? Unfortunately I don’t know much about car audio so can’t recommend a setup, but given the source material is 2 channel, the most you’d want a the rear is a bit of backfill, which could be delivered (with higher fidelity) by upgraded 4” speakers in the headrests.

 

[ph001]

I suppose it’s just because the rear 4” oem drivers seem woefully inadequate compared to the front. I think the oem front setup is very good - completely satisfied by it, but I like at least a good amount of midbass from behind...hence the upgrade.

I guess soundstage is the wrong word - i’m not really after dolby atmos in the Z as those roof speakers could prove tricky. Let’s call it a better rear ‘presence’.

 

[C8H18]

I've got 6.5" Focal coaxials mounted in a home-made MDF template. OEM speaker grilles covering them. Signal diverted from the original rear speakers. Works a treat!

 

[Tinman6]

I've got 6.5" Focal coaxials mounted in a home-made MDF template. OEM speaker grilles covering them. Signal diverted from the original rear speakers. Works a treat!

+1 for Focal, superb speakers, would definitely recommend

 

[ph001]

Me and Focal had a bit of a falling out with home hifi. The crossovers they were using in their Chorus 826v and 836v floorstanders were utter junk. And we are talking £2k speakers here. Lost all faith in their products after that.

 

[Coffee331]

Why do you want a better rear soundstage? Are you watching Saving Private Ryan on the satnav or something?

Seriously though, why not a dedicated, long-throw set of bass drivers and an upgrade of the front 2/3-way set? Unfortunately I don’t know much about car audio so can’t recommend a setup, but given the source material is 2 channel, the most you’d want a the rear is a bit of backfill, which could be delivered (with higher fidelity) by upgraded 4” speakers in the headrests.

Unfortunately I don’t know much about car audio so can’t recommend a setup, but... :lol: :surrender: :surrender: ldman:

 

[GuidoK]

I'd always go for a more dedicated 6,5" long throw subwoofer set.
The sets you've selected arent at all suitable for subwoofer applications.
You have to so some simulations to see which ones are suitable, which is a combination of the driver and the available space/box volume.
For the JL audio there are no thiele small parameters available (usually a sign for cheaply made lower end speakers) so no simulation is possible at all.
For the herz speaker I made a simple simulation and I set it out to a more dedicated 6,5" 4 ohm sub (a Tangband W6-1139SIF):
The red one is the Herz and the green one is the tangband and I've simulated them in a 5L closed chamber



You can see that the Herz woofer is completely blown away by the tangband that goes about 1 octave(!) lower
I'm sure there are loads more woofers that perform similary to the tangband or better, but this one was a fast and easy pick
The tangband is about 65-70quid/piece I believe
http://www.tb-speaker.com/products/w6-1139sif

It has an xmax (maximum linear throw of the conus) of 11,5mm (compared to the 4mm of the Herz speaker)
But I dont know if it'll fit. Tangband are specialized in small speakers so they have smaller dedicated long throw woofers.

Whatever you do, provide the subs with their own amp, with an active crossover (your herz amp already has that).
That will let you tune in the bass much better and a passive crossover always has a bad effect on low frequencies (the series coil in the low frequency filter changes the thiele/small parameters in such a way that it hurts the low frequency response)

If you have the normal sound system (so I believe also no mids in the doors) you can also upgrade the woofers in the footwells.

 

[MrPT]

Why do you want a better rear soundstage? Are you watching Saving Private Ryan on the satnav or something?

Seriously though, why not a dedicated, long-throw set of bass drivers and an upgrade of the front 2/3-way set? Unfortunately I don’t know much about car audio so can’t recommend a setup, but given the source material is 2 channel, the most you’d want a the rear is a bit of backfill, which could be delivered (with higher fidelity) by upgraded 4” speakers in the headrests.

Unfortunately I don’t know much about car audio so can’t recommend a setup, but... :lol: :surrender: :surrender: ldman:

Hah. I mean I don’t have a clue about brands of speakers, amps etc, but yeah, fair point and strong emoji-fu

Probably just jealous that ph is upgrading his car and I’m shopping for off white emulsion paint...

 

[ph001]

This is impressive work. I have to admit I'm very surprised that different drivers of the same diameter in the same enclosure have such varying bottom end response. Can I ask what software you are using to simulate that, and is there a download link?

I'll have a look at the W6-1139SIF, in the meantime I just spotted some bargain MOREL TEMPO ULTRA 602 on Ebay. I know Morel have a great rep but I'm struggling to find parameters for them. Would be interesting to see how they perform in your simulation.

 

[GuidoK]

I use WinISD for simulating (but there are loads of other programs)
WinISD is free and has a database for lots of speakers, however these kinds of car audio speakers arent in it so you have to add the thiele/small parameters from those drivers to the database
WinISD:
http://www.linearteam.org/

Those morel speakers fall in the line of the earlier JL audio's
Theyre not dedicated subwoofers, but what we call a 'compo set'. Usually designed to be fitted in the doors (so a bass-mid driver and a tweeter). If they publish thiele/small parameters for the woofer, they;ll be in the line of the Herz speakers, so not really suitable for low frequency generation. All those kind of speakers will never perform well in the low frequency range because they dont have the sufficient linear excursion of the membrane and dont have the sufficient mass in the membrane. If they had, they wouldnt be able to produce good mid tones (and wouldnt be suitable for a compo set).
So if you want a dedicated sub in the cubbyholders, look for woofers with a large rubber surround (that usually means large Xmax) and a beefy magnet (needed to drive a heavy membrane).
The DD 506 sub is also pretty good in low volumes:
http://ddaudio.com/products/subwoofers/redline-series/500/
Here it is (blue) compared to the tangband (green) in a 5L cabinet where the tangband imho still performs better and can produce more volume due to its larger xmax (12mm vs 9mm):


But watch what happens in a 2L cabinet:


The tangband will start to sound boomy (bad impulse characteristic in 2l) because the parameter QTC (which is the total dampening of the system) gets too high. (winisd also calculates that number). As a rule of thumb you want to have the QTC (sometimes called Qbox) to be aroud 0,7 (or lower) but certainly not higher as 0,9.

I simulated all closed cabinets.
You can also think of bass reflex, but I dont know if there is room for a suitable bass reflex pipe (both in lenght and in width, but mainly lengt as these combination of parameters usually require long reflex pipes)

 

[Magicarcher]

Why do you want a better rear soundstage? Are you watching Saving Private Ryan on the satnav or something?

Seriously though, why not a dedicated, long-throw set of bass drivers and an upgrade of the front 2/3-way set? Unfortunately I don’t know much about car audio so can’t recommend a setup, but given the source material is 2 channel, the most you’d want a the rear is a bit of backfill, which could be delivered (with higher fidelity) by upgraded 4” speakers in the headrests.

You may claim to know not a lot about audio, but I have you spot on, why have a rear soundstage, that's like going to a concert and turning your back to the band, it just isn't going to sound right.

I'd always go for a more dedicated 6,5" long throw subwoofer set.

With you 100%, have you considered Reckhorn D165, half the price of the Tangband and very well made German loudspeakers.

 

[Magicarcher]

Here it is (blue) compared to the tangband (green) in a 5L cabinet where the tangband imho still performs better and can produce more volume due to its larger xmax (12mm vs 9mm):

Have you by any chance calculated the volume of the rear cubby areas. I tried to calculate it using a series of calculated cube and trapezoid measurements, but it is an absolute pig, the area is so irregular. I read a BMW technical document somewhere that said it was 10-11L but there is no way it is that big. I calculated it is somewhere between 5L and 6L

 

[Anmarube]

I have Morels in the rear cubbies and in the footwells. 10" sub in the boot. Fantastic when roof up but disappointing bass when down so have to find a way to get bass in the cabin when down. Think the Morels in the cubbies are going to be replaced with some long throw drivers.

 

[ph001]

I think it about 4l. Defo less than a petrol can which is 5l. Good shout on the Reckhorns, amazing value. Have a Reckhorn amp powering my 10hz transducer bolted to my settee in my AV room. Nice piece of kit.

 

[GuidoK]

With you 100%, have you considered Reckhorn D165, half the price of the Tangband and very well made German loudspeakers.

I didnt consider/know that one (I've been out of the diy scene probably as long as I've been in it....), but it simulates very nice:


Not quite as good as the tangband (which has the upper hand to the -6db point) in a 5L box (but the difference is minimal), and it doesnt have the massive 12mm xmax from the tangband, which I've not seen in this class before thus quite unique (so the tangband will be able to produce more bass if amplifier power is sufficient), but in smaller cabinets (3L) the reckhorn does better because the Qbox is lower. And indeed very very cheap for that speaker. The tangband is already very cheap (€60) compared to say a JL audio jl audio 6w3v3 (€170) or 6,5"peerless SLS (€90), but €30 for such a nice minisub is crazy.

Have you by any chance calculated the volume of the rear cubby areas. I tried to calculate it using a series of calculated cube and trapezoid measurements, but it is an absolute pig, the area is so irregular. I read a BMW technical document somewhere that said it was 10-11L but there is no way it is that big. I calculated it is somewhere between 5L and 6L

No I just made a guess. Its certainly not 10-11L (thats the size of a bucket!), and dont forget that the volume of the sub itself also has to be subtracted (1-2L)
TBH, if one could get the original carver units for cheap, those would also be an option. They're quite well made. An odd impedance, but you could wire them in parallel and use a 2 channel amp in bridge mode to get the most power out of it (amps usually work to 4ohm in bridge and the nominal impedance of 2 carvers in parallel is 5ohm, so a safe setup. I think the factory hifi pro DSP setup is the same.

I think the biggest question which hasnt been answered yet is: will a normal 6,5" sub fit, or does it have to be smaller.
If it has to be smaller, the availability of long throw chassis decreases significantly.

 

[ph001]

I suppose we ought to consider the fact that the OEM installation IS ported. I think it's done through the oval cutout in the top of the enclosure, You have little chance of finding the thiele small parameters for the oem driver I guess but maybe a fully sealed enclosure is not the way to go.

Would be difficult to model though I bet as the port is effectively cutoff from the front of the driver by the fascia trim (well not completely isolated as there are a few vents and gaps around the cd changer that lead back around to the front), but it's certainly a complex path. It's kind of halfway between using the boot as the box volume (almost infinite baffle) with a bit of leakage thrown in!