Hi all ..

I am currently in the planning and preparing stage of another SQ install, and I am thinking of trying something a little different with the Midbasses.

My drivers consist of :

Dynaudio sys 220 mk2 (run off MRV-1505)
2 Dynaudio MW170 midbasses (run off another MRV-1505)
2 Image Dynamics IDQ-DVC 12's (run off a MRV-1005)

The sys 220 splits are going in the kicks, and the midbasses are going to go in the doors.

In the past I have run sealed enclosures up the lower part of the doors, and have been really impressed with the transient response and power handling of the drivers (past midbasses include some MBQuart 8's and some old-school Alpine 8's).

I have not really been overly empressed with most of the door mounted IB midbass setups that I have heard up to this point. :-/

The doors on the car that I am installing on at the moment are reasonably deadened (although I am prepared to go further with this if I do run IB).

Door lining

so my main question is :

Can you run midbass 8's in the doors IB without much of a compromise?

In terms of power handling, transient response etc.

I know I can do a lot to make the doors more 'sealed' and less tinny, .. but it'll still be a compromise I feel.

-Fr

ib mid basses in fron doors will always be a compromise. another older selection for this was 6x9 speakers in the front doors, good quality 2 way types that attempted to gain good almost full range freq and single point origin, well as close as two ways can be, but i have heard of a system using very old alpine single points 6 x 9 speakers.

if your really serious about getting this set up to work well, then you should seriously look to a way to enclose those mid basses. you have the ts parameters i hope? other wise get them.

i have heard of it being done before using storm water pvc piping and fittings. you need to get a piece large enough for the speaker to fit inside of, not easy for a 8 incher. you make a mdf baffle inside the pipe for the speaker to attach to and you can use the extension of this pipe as part of a custom front mounting.
then you need to seal the back of the main pipe. i doubt you can get a diamter that large with a screw cap so you will probably need to get a flat piece and glue that on. then, from this main section, you make lengths of pipe and right angle fittings and cut these into the side of the main section. these can be joined using that pvc glue the retic people use.
it all comes down to how much room in your doors.
generally, you may have the room be able to get a 75mm diameter pipe in the bottom of the door cavity, 400-500mm long, but trying to get it into the doors is probably immpossible. usually it is done with a number of short sections, joiners and lots of pvc glue.
that can give you about 6-10 litres overall but most 8 inch speakers need more than this so it really depends of the vas of the mid bassers and how much room you have in the doors and how easy it is to work inside of them.
i wouldnt recomend going much smaller than 75mm pipe other wise the whole enclosure wont "breathe" properly.

[ July 29, 2003, 11:45: Message edited by: audible ]

Hmm ..

I had not thought about using a pipe, I doubt that I would be able to gain enough room in there, .. but I'll look at it tonight and see what can be done.

I have been reading today a lot about aperiodic membranes, and I am almost keen to give some home made ones a go.

TS parameters

Above link for the info regarding the Dyn midbasses.

I am not too sure as to what the recommended sealed size might be for the drivers (in a midbass application) .. but I am only going to run them from ~200hz -> 70hz.

Thanks for the ideas!

-Fr

Don't discount using ag. pipe as suggested.
It is available in large diameters up to 12", with varying wall thicknesses in either PVC or high-density Poly (like the garden irrigation stuff, but a high pressure version used instead of galvanized steel).
There are also myriad connection fittings and end caps to suit.
An irrigation shop is the best place to source this stuff if you decide to take this route.

Definitely check out the t/s parameters to see if the midbasses you are looking at will do better sealed... if not then you are most likely going to loose bass extension over a simple IB door mounted application. Depending on where you intend to High pass it you might not need that much bass extension anyway.

If you want to squeeze even more space out get creative with the fibreglass. Make sure you form a shape that you will actually be able to pull out of the door... so carefully think about it first. I was thinking along the lines of maskingtape and cardboard to form some sort of a mold.

One crazy idea that comes to mind... especially If you want even more space and there is plenty at the bottom of the doors.. how about fibreglassing a bent pipe section that runs along the bottom of the door sealed to the backshell... kinda forming a sealed extenstion to the backshell. Then use some sort of watterproof damping material in case it gets wet and to stop it vibrating against anything metal in the door???

There is little point in using AP membranes for a mid bass driver IMO, as you are not trying to get that low. You might want to try some deflex panels, as these have worked for me on several mid bass set ups, and IMO work really well. Im about to move my 8s to the doors and will be using deflex panels. I have them in the boxes I use now as well.

Anyway Id forget trying to box them and use the door as the box, as it should be fine, appart from the rear wave bouncing off door skin, back at the driver, which is where the deflex panelks fit in. ie to elminate or reduce this colouration.
peace
Cyberpunky

Where do you get these deflex panels from? or do you make your own?

I am keen to try a few things all in the name of experimentation.

-Fr

I threw away the factory door trim and had them redone from scratch, from MDF, with a pod from MDF and fibreglass. The 8 is now sealed and with pillow stuff behind it, sounds quite good.

Go active (fully active) and band pass the 8's.

As far as frequencies go, well it's all trial and error. (I use 50hz to 630hz but it's not staying there and mine's different to yours).

very good speaker and amp choice, will sound perfect with alot of time and care on install and frequncy set up...

Rich

[ August 04, 2003, 10:56: Message edited by: R ]

Cyber you were talking about deflex panels, I was thinking of getting some Focal Plain Chant pads as they stop the waves coming back to the speaker, just wondering if the plain chant and the deflex panels are one of the same?
Thanks

I have never seen the other product so cant say.
peace
Cyberpunky

I'd say that they are. I have the Focal plain chant pads in my sub box - and plan on using them in my next install.

What they're reported to do - is exactly the same as you describe - so I wouldn't see why they aren't.