Slatted wood grille speakers - Retrofitting - How to select new full-range drivers?

[boven]

Hello everyone, I'm starting my first DIY audio project and I have a few questions about the best approach.

I recently picked up two wooden speakers with a slatted grill from a thrift store ("kringloopwinkel") in Amsterdam. I reckon the speakers are from the 1960-1970s and were a DIY build - perhaps the housing was sold as a kit (I believe that was common at the time).

Now this pair of speakers contain two different drivers, one seemingly made by Philips and the other one by Isophon.
I'm thinking about replacing these with modern, full-range drivers that can work with the enclosure. Currently, using two different drivers won't give the best output. But I'm not so sure how to find a possible match for the housing.
My initial idea is to replace the drivers, and install a Raspberry Pi with HiFiBerry AMP2 in one speaker (the speaker which is slightly larger) to make it a TIDAL Connect speaker (a speaker pair that won't break the bank). A friend of mine who is a luthier can help me to repair the damaged wood veneer.

Both speakers have 8 openings/gaps, of which the top and bottom ones are slightly smaller.
The inner dimensions of the housing are as follows.

Speaker 1
230mm x 210mm x 125mm
6.04L
0.213 cubic feet

Speaker 2
230mm x 250mm x 125mm
7.19L
0.254 cubic feet

CAD drawing of front of speakers

Front of speakers photo

Speaker 1 photos

Speaker 2 photo

Isolation photo

The isolation probably needs replacing.

Question about selecting full-range driver

• How do I select the full-range driver that works with the enclosure?
  • Note that I can make the larger speaker the same inner size by compartmentalizing the Raspberry Pi + HiFiBerry amplifier in a 40mm space.
  • So far I have tried fiddling with WinISD, but I'm just not sure how to take into account the slatted grill/vent situation when modeling.
  • PartsExpress also notes the optimal vented volume. Is it enough to select a driver by matching their vented volume with mine for +/- 10% ?
• What is the best way to mount the full-range driver?
  • Should I mount the driver in the same way as the current ones, or should I ensure that the speaker covers the six larger middle vents while keeping the top and bottom vents open for bass? If so, this would probably require a 4-inch full-range driver.

Thank you for your time!

 

[WhiteDragon]

It is sealed, so the volume needed for a sealed enclosure usually has a pretty wide forgiving range.
Or at least could be sealed if a second baffle was made to fit behind.

Is interesting how the last 2 slots of the grill would function as a port since open.
Basically a second baffle made to fit inside could block them off with a round cutout.

Think you could use something up to 5 or 5 1/4 inch.

WindIsd you can calculate a sealed box for the driver you like. Calculate a .8 Qtc and a .5 Qtc and you will see how wide the range is.

Speakers have a equation which combine mechanical and electrical properties. called Qts

If it is a high number like .5 to .6 it wants a big box, very low number like .3 or .2 is a small box.
.4 being pretty average.
I would ignore PE recommended enclosure post, many of them total nonsense.

Say you wanted to or if you could get a big 6.5 inch in there. likely look for a low Qts around .3 many Daytons will have low Qts.
Same with 5 inch.
A 4" or 3" maybe even if Qts was high around .5 could work, it wants a large box.
But likely within your box size.

Basically as noted with WinIsd calculate sealed Qtc at .8 to see the small side of what works and .5 be very large side of what it wants
.7 or .707 being the normal flat response.
You will see with many speakers the volume range they work in is rather wide.

 

[wg_ski]

Those aren’t exactly “sealed”. “Poorly baffled” being the operative word. The drivers almost certainly have Qts significantly north of 1.0. That was the old school way of dealing with LF losses.