enclosure size vs. Technical data

[Radioman62]

Hi
I have searched this forum but not found...

I have some to learn when it comes to speaker design. I have read a lot lately but I throw this question in, probably easy answered:

• If the recommended closed cabinet for a woofer speaker is 25-35 litres. Is it doubled with two speakers?
  
• I have an old kit i built more then 15 years ago with two 10" bass woofers where the recomended volume for a closed cabinet is 25-35 litres for one speaker. I have two and the box from that kit was 82 litres inside. Is that OK?

I want to hear some pros an cons from the more enlightened and edjucated DIY guy in this area of the hobby.
Thanks for taking time for a short answer.

[Inductor]

Radioman62,
I (or others) can simulate your kit if you post driver model and/or T/S specs.
If you have two drivers in the same box I would assume double the volume.

[planet10]

Do keep in mind that once large enuff, the size of a sealed box is pretty flexible.

dave

[Ronmeister]

To answer your question, 82 liters should be fine if the kit manufacturer calculated it correctly. To be absolutely sure post the T/S paramaters, there are plenty of us that'll be happy to calculate volume for you. You can indeed double the volume if you use two drivers.

A little too much volume is not an issue with a sealed enclosure. You can experiment with solid fillers to reduce volume. If the volume turns out to be too small there are a few tricks you can utilize, mechanically as well as XO-wise, though this can be tricky.

Hope this helps.

[Radioman62]

I have downloaded the software WinISD Pro (Alpha), two minutes ago.

I will try to fiddle with it but in the meantime it would be great to see if you get other figures then me.

It's a real old element from Seas (Norway)
25F-EWX, 10" High Fidelity woofer.

Thiele - small parameters:
Vas 175 litres
Qms 3.8
Qes 0.24
Qts 0.23

The box is filled with "fill material". There is also a small box with a middle frequensy driver taking some place so lets say 80 liters for the total where the woofers play.

[MJL21193]

Hi Ove,
The woofer is not especially well suited for a sealed box (better suited for vented) and in a 35 litre box (near ideal size for these T/S numbers) F3 (at what frequency the response falls by 3db) is around 80Hz - not great for a pair of 10" woofers.
Putting 2 of these in an 80 litre sealed box will not improve the situation, in fact you may run out of excursion on the drivers in this large space.
If you have 80 litres to work with, consider making the box ported and you will get more low end output.

[MJL21193]

I made a couple assumptions for the figures you didn't supply (Fs=25Hz, Sd=250cm^2) and here's what I see for 2 drivers in a single 80 litre box:

118.PNG

Descent response. Some people are biased against vented boxes (mainly due to ignorance) though so it may not be your cup of tea.

[Radioman62]

Hi John
Nice to meet you again. I see you have been avtive in other threads with speaker building as well as amplifier work.

FS is 26Hz
Effective diaphragm is 350cm^2

I have no religion at all when it comes to designing speaker enclosures. Is it mandatory?
Seas suggest 25 - 35 litres for a closed cabinet (one element) and 30 - 40 litres for a bass reflex cabinet.

So what do you suggest for a hole in the baffle? Also the tube length inside of that hole I guess have influence. See I'm a noob here.

I have wondered if a pushpull approach is a good thing? I mean to turn the bottom woofer the other way and change +- interconnections. If I try, would that configuration also be better with a vented box?

After I have my data at hand I will go for a biamping, partly active filter design and put in two amps and PSU in the cabinet. Heatzinks on the outside.

[Radioman62]

Your link didn't work at first. Now I see the data.
What does "port area" and "port end correction" mean?
How long should the tube be inside the 10cm hole?

[MJL21193]

Here it is updated and refined a bit:

118.PNG

Box volume is 80 litres
Port diameter is 10cm
Port length is 7cm - the effective length of the actual tube is how what I go by. There is a margin of error here, 1 or 2cm either way rarely makes much of a difference.

Good to hear you are agnostic in this religion Ove. Too many come in with preconceptions that they picked up without any real experience or understanding.