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

[IAmOrion]

If the grommet sits in item 9: item 9 is a soft piece. I dont think thats the box, but rather the dampening material? I'm not sure whats behind that.
If the boot is behind that, its an open air setup and not a box of any kind.

(9) is indeed soft dampening material. The area it sits in, is enclosed as part of the chassis. (6) is just a "faceplate" for want of a better word. When in place it forms an almost sealed "box"

[ph001]

Yes, I got similar port dimension when simulating the D-165!! Might look a bit odd with a piece of pipe stuck out of the window

In terms of the enclosure, the soft piece (no.9) sits directly into the sheet steel enclosure which forms the rigid speaker cabinet. The grommet goes through the soft piece and locates on a rectangular hole in the sheet metal. I think the cables come in through the circular hole at the back. The rectangular hole forms the 'port'.

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[GuidoK]

Ok thats odd.
Whats behind the round and rectangular holes?
Is it directly open to the boot or sealed off again?
Or does it extend the volume of the box?

To have a sealed box principle its important that holes and cracks are sealed as good as possible. It also helps with the power handling/capabilities of the driver.

If the grommet is the port it wouldnt be very effective as it doesnt ventilate in the same compartment as where the listner sits....

A ported box works on the principle that the mass of air situated in the port forms a virtual 2nd speaker/resonator.
Its excursions are in phase with the loudspeaker membrane.
There is no point having that resonator in a different sealed cavity than where the listener sits.

[ph001]

Ok thats odd.
Whats behind the round and rectangular holes?
Is it directly open to the boot or sealed off again?
Or does it extend the volume of the box?

Well the grey you can see behind the round hole is the back of the carpet trim in the boot, but remember that the soft box (9) does not have a corresponding hole, it just has a cross cut 'slice' for the wire to penetrate through. The rectangular hole kind of goes out to the cd changer / roll hoop space (which is pretty much open to the entire boot volume) and has a corresponding hole in the soft box and out through the grommet (10)

I think as you say, it can't be effective as a true port as such. I suspect it is there to increase the air volume of the enclosure.

That's why I'm interested to hear (and measure) how both installations sound. I suspect the Morels will certainly be more suited to the 'ported' configuration but it does make you wonder what the OEM subwoofer parameters are.

[GuidoK]

Odd.
I cant make any funded theoretical statements about that or that it would be able to simulate that in a physical model.
Maybe they experimeted with it and just decided that this sounded best
Or there is some other reason like they need the holes for draining when the chassis gets submerged in the anti corrosion process tank or need the holes for mounting purposes in the assembly process or whatever and its an acoustical trade off.

All I can say is experiment with your reckhorn speakers. Do a listening test with the holes open and one with the holes closed (preferaby with somethin hard, like a small piece of plywood sticked over the hole with double sided tape), and decide which sounds best.
Also look at the driver and see if one has more distinct uncontrolled excursions of the membrane on low frequencies/high volume passages.
Thats something to avoid, because blowing a sub usually is a result of membrane excursions being too large so the voice coil slams into the pole plate of the magnet damaging/warping the voice coil as opposed to thermal overload.
So play a song with lots of bass at a certain set volume (or any other specific sound source) and compare the excursions of the membrane.
Be sure that the 2 tests are equally loud on radio and amp setting.

My guess is that a completely sealed box will sound more punchy and will allow for more power input (because it dampenes the membrane better), so you can compensate the possibility that the strangely vented system has a slight efficiency advantage by turning up the sub amp a little bit.

[ph001]

Will let you know how I get on.

[Magicarcher]

I made a quick simulation, for the Reckhorn D-165 to go ported, you need a 89cm long port with a 2" diameter to get it tuned, and then it simulates beautifully, goes really deep (-3dB at 47Hz). But where do you leave that 3' long pipe? With a bigger diameter pipe you only need more lenght and if you go smaller, the air speed velocity in the pipe gets really high so you hear pumping air sounds..

If you go to a big tube it will have to be long, bear in mind there are many small commercial two way loudspeakers that use 6" drivers in small enclosures with ports around 30mm diameter (wharefdale diamond, JBL control etc.) and sound perfectly acceptable. Sure they are not going to rock the foundations (or shake your door panels off!) but I would imagine they would produce more base than standard Z4 setup. That suggests to me that it must be possible to get acceptable sound with a smaller diameter port.

At the end of the day it is a balance of compromises, the Z4 can't accommodate a 8-10 inch driver in a 30L enclosure. So something has to be compromised. For me it is either go sealed box and sacrifice some bass extension or go ported with small port and suffer some colouration.

[GuidoK]

If you go to a big tube it will have to be long, bear in mind there are many small commercial two way loudspeakers that use 6" drivers in small enclosures with ports around 30mm diameter (wharefdale diamond, JBL control etc.) and sound perfectly acceptable.

Sure but those speakers usually dont come with a long throw sub having 8-12mm lin. xmax capabilities, the speakers in those kind of boxes usually have half or 1/3rd of that.
In the end it all comes down to air port velocity. In the 90's when I did extensive moddeling on PA subwoofers I used a program that automatically calculated that maximum air velocity in the port in a mach number and also gave an indication whether it was good or not. But I never figured it out how it did that. Probably using SD, Xmax and the tuned frequency or so. I dont know if I even have that program, or if it'll even work on modern windows....need some windows 3.11 emulation

I know WinISD has some capabilities in that area also but I dont seem to get decent results out of that for the reckhorn driver.
But even if you go with a tiny 30mm port, it'll have to be 30cm. From what I can see thats still way to long to fit in the enclosure. If I look at the picture its only half as deep tops, so still no go.