I am guessing your woofers are in that small volume for the sake of Qts, not known yet.
A larger vented cabinet should be able to introduce the desired change, but we are in the dark regarding needed data.
His speaker uses dedicated closed box woofers, with small, weak magnets and limited excursion. These need the air cushion behind them to work.
There is nothing you can improve on such a chassis by enlarging the volume and a vent will not work at all.
Today we are used to much more universal drivers, but these old, high Qts, low Fs, high Vas ones are working in a very narrow region only.
There is nothing but using some tone control, equalizer or DSP to tune them to your liking, if you have a capable amp you can get deeper bass with limited SPL.
I'm a great fan of modifying anything, but these are best used "as is".
There is nothing you can improve on such a chassis by enlarging the volume and a vent will not work at all.
Today we are used to much more universal drivers, but these old, high Qts, low Fs, high Vas ones are working in a very narrow region only.
There is nothing but using some tone control, equalizer or DSP to tune them to your liking, if you have a capable amp you can get deeper bass with limited SPL.
I'm a great fan of modifying anything, but these are best used "as is".
Hi, you can do a very simple port test fully reversible if it doesn't work.
Remove the tweeter or the mid-range, and use this hole as the port.
Install a resistor in place of the disconnected speaker or reconnect it using a wire through the port/tube, just to not let the crossover with an opened connection.
Using a thick paper sheet, create the tube and fix it with a tape - you may need 2 or 3 layers so as to get a rigid tube.
Use tape to around the tube to insert it with some interference.
You can try some lengths and check the result.
Examples for a 94-liter box (you can play with WinISD and try other frequencies, diameters and lengths).
Use the diameter that you have in the tweeter/mid-range.
3" hole and 17cm, Ft=25Hz
4" hole and 34cm, Ft=25Hz
If you like the result, then you go ahead the open a port.
A port can give you a lot of bass increase if it works fine.
Summary:
1. Assuming F3=28 Hz is a real measured data, it should be emphasized - it is very low, even for a big tower/floorstander. And especially low for a sealed box loudspeaker.
2. Assuming F3=28 Hz and Fb=36 Hz are a real measured data, then Qtc=1.1 - which is somewhat on the high side. If original stuffing in the box is too small in quantity, than stuffing with fluffy rockwool up to 100% of the enclosure volume can bring a little bit lower F3 and tighter bass (by decreasing Qtc).
3. High Qtc=1.1 means box volume is lower than optimal, but drivers Thiele-Small parameters maybe can't allow box volume with acceptable dimensions. Maybe Qtc=0.707 is not possible at all. So we can safely abandon the idea of bigger box volume.
4. Porting the original box with tuning lower or equal to Fb=20 Hz will decrease F3, but sound quality will be worse.
5. Qtc=1.1 is ideal value for "third order loading" - big bipolar capacitor in series with woofer. F3 will be appreciable lower.
1. Assuming F3=28 Hz is a real measured data, it should be emphasized - it is very low, even for a big tower/floorstander. And especially low for a sealed box loudspeaker.
2. Assuming F3=28 Hz and Fb=36 Hz are a real measured data, then Qtc=1.1 - which is somewhat on the high side. If original stuffing in the box is too small in quantity, than stuffing with fluffy rockwool up to 100% of the enclosure volume can bring a little bit lower F3 and tighter bass (by decreasing Qtc).
3. High Qtc=1.1 means box volume is lower than optimal, but drivers Thiele-Small parameters maybe can't allow box volume with acceptable dimensions. Maybe Qtc=0.707 is not possible at all. So we can safely abandon the idea of bigger box volume.
4. Porting the original box with tuning lower or equal to Fb=20 Hz will decrease F3, but sound quality will be worse.
5. Qtc=1.1 is ideal value for "third order loading" - big bipolar capacitor in series with woofer. F3 will be appreciable lower.
See Mr. Prescot, you should know a little about the Braun LS200.
This speaker was developed to reproduce the (then) new digital recordings of the TELARC record company. The Telarc recording guys and the Braun engineers did all they could do to get the best sound possible out of the driver material they had. Some of their "usual" drivers had to be modified to give an acceptable result. The size of the speakers and their weight show they were a no compromise poduct.
Do you really thing that you can improve on a speaker that was developed by the best engineers of one of the best Hifi brands of its time and sound tuned with the sound engineers of one of the world best audiophile recording companies, pioneering digital recording?
You seem to be very young, don't you think you are a little arrogant? What do you have that the educated professionals that designed and tuned it, did not have?
For a beginning, start to measure the TSP of the drivers used. If you can do such a diffilcult operation. This will give you the option to calculate what you can do with these woofers. In theory, ignoring the excursion limits of the construction. Maybe a quick, rough calculation? The speaker is rated at 200 Watt rms. That may leave 90 Watt rms for each 25cm / 10" driver. Have a look at todays 10" driver, most have a much higher rating. This is because of modern, high excursion motors they have, high temperature voice coils etc.
As I told you (and you ignored) these are classic "air suspension" Hifi drivers of the time. A vented cabinet needs drivers with a very strong magnet.
Look at what you have: A large speaker driver with a small magnet. Take the driver in your hand and push the cone into one direction: It will return slowly to the zero position. If you use them without the air cussion, the power to return the cone will be missing. No good start for precise bass reproduction.
I don't understand why you don't want to use electronic help to adjust it a little, but have no problems to ruin this speakers construction. Doesn't fit together.
Other from renewing the electrolytic capacitors and, maybe, filling the cavity with a little extra rockwool, there is nothing usefull you can do.
Anyway, maybe there are people that buy a Picasso painting and improve it with a Sharpie marker, because they are sure to be a greater artist than Picasso.
This speaker was developed to reproduce the (then) new digital recordings of the TELARC record company. The Telarc recording guys and the Braun engineers did all they could do to get the best sound possible out of the driver material they had. Some of their "usual" drivers had to be modified to give an acceptable result. The size of the speakers and their weight show they were a no compromise poduct.
Do you really thing that you can improve on a speaker that was developed by the best engineers of one of the best Hifi brands of its time and sound tuned with the sound engineers of one of the world best audiophile recording companies, pioneering digital recording?
You seem to be very young, don't you think you are a little arrogant? What do you have that the educated professionals that designed and tuned it, did not have?
For a beginning, start to measure the TSP of the drivers used. If you can do such a diffilcult operation. This will give you the option to calculate what you can do with these woofers. In theory, ignoring the excursion limits of the construction. Maybe a quick, rough calculation? The speaker is rated at 200 Watt rms. That may leave 90 Watt rms for each 25cm / 10" driver. Have a look at todays 10" driver, most have a much higher rating. This is because of modern, high excursion motors they have, high temperature voice coils etc.
As I told you (and you ignored) these are classic "air suspension" Hifi drivers of the time. A vented cabinet needs drivers with a very strong magnet.
Look at what you have: A large speaker driver with a small magnet. Take the driver in your hand and push the cone into one direction: It will return slowly to the zero position. If you use them without the air cussion, the power to return the cone will be missing. No good start for precise bass reproduction.
I don't understand why you don't want to use electronic help to adjust it a little, but have no problems to ruin this speakers construction. Doesn't fit together.
Other from renewing the electrolytic capacitors and, maybe, filling the cavity with a little extra rockwool, there is nothing usefull you can do.
Anyway, maybe there are people that buy a Picasso painting and improve it with a Sharpie marker, because they are sure to be a greater artist than Picasso.
LOL, that's a very good one ! 🙂
@presscot ,
With the number you give, you are not ecperiencing a lack of bass, 99% of the music is above 35 Hz.
If the drivers are old there is more chance the Qtc has increased which is not equaling to a lack of bass as well... imo.
Could you tell why you need to know more about the Qtc of the woofer related to what you experience as a miss or a bad listening experience, please ?
Have you the reference of the speaker or the 10" drivers, perhaps a filter shematic ?
There are a lot of possibilities according the context : room mode (a deep due to the listening position), filter, agging of the drivers and capacitor filter caps, design itself, etc.
It seems not a bass boost is needed and anyway what you are measuring is the room at those low frequencies and where the mic is.
It should be easier to have the 10" driver reference (you need anyway if you want a boost in order to not go beyond the Xmax as all drivers and/or amp cann handle a boost) and if sealed you measure the internall volume box, 3 distances to have the liters. then with Victuixcad you can easily sim to abstract the Qtc with the ref of the drivers. If old, indeed some of the drivers datas have moved : certainly stiffer Qms, etc. So as members said, impedance measurement can help to measure the drivers state. increasing the Vas equals to lowiswh the Qtc.