bass cab q questions

[slr 5000]

hi all im about to start building the basscabs for my new speakers and would like some advice on what q to use
ive modeled them in a sealed cab with a q of .707 and it comes out to 46l
f3 54hz
fb 53hz
they are eton 12" hexacones and will be crossing over to manger transducers at 150 to 200 hz
the specs are 8 ohm
resonence freq 26hz
qms 3,52
qes 0,38
qts 0,34
vas 150l
does this setup sound ok? im not after sub type bass i just want it too be fast ,tight and as low as possible .i dont want to run ported as i feel the bass drivers will integrate better with the mangers in a sealed cab .what are the pro,s and con,s of using different q,s for the bass cabs .say .505 as opposed to ,707
cheers

[gtforme00]

This depends a lot on what your room is like. If you have a smaller room and solid walls, go with the lower qts. If you have a large open room, you may find a qts of .5 to be too lean and may want to stick with a higher qts.

Ideally, you could build the box large for the low qts and then add blocks of wood or closed cell foam to the box to reduce the effective volume to tune the qts for your preference.

If you are willing to consider a different approach, you may find that ported systems are not as objectionable as you think if they are not tuned to be "flat". Start with a box of recommended volume and port length (a "flat" response). Keep the volume the same but lower the tuning frequency by making the port longer. You will end up with a similar sound to a sealed speaker, but with much better low end extension.

Regards,
David

[The golden mean]

Tolerances in manufacturing of drivers cause to the fact that manufacturer´s data are at best an average. Thus building a box that is up to 20% too big is a good idea. Then you have the possibility to experiment with the volume of the box as stated above.
I have put bags filled with sand in my big ported enclosures in a way so the bags aids as resonance dampening.

Ported design have their advantages and people saying they never can sound excellent have probably stayed away from listening to the really good incarnations!

I think one drawback is that they are more demanding to get right as there are more parameters to consider and experiment with. One way is to measure, but in my experience it´s hard to predict from diagrams which tuning is the best.

I would say that building a rigid box that is absolutely airtight is the starting point both for a vented and closed cabinet. Some people believe that this isn´t that important for the former type as the vent in itself seems to be a "big hole" but this isn´t true.

You can build an temporary box to do some experiments and these will take time but the result will most likely be pleasing to you. Or you can measure the woofers and then determine a target and simulate the result.

In my experience which now is a quite long one, you have to listen and make choices out of this. The positioning of the loudspeaker and room tuning makes up for more variables so this is indeed a time consuming approach.

I have considered the Eton woofers you are about to use for a sub project for a friend and rejected them as he wants a very small sub. For the 12" Etons I would start with bigger boxes to take advantage of their low end capabilities.

T would make the cabinets solid and use a combination of different materials and use braces. By combining different materials as particle board and MDF you get a better result than by solely using one, this is confirmed in Hifi World magazine recently. I have used several materials as lead filled aluminium bars, granite, slate, ceramic slabs, real wood together with some
intelligent placed braces and this has really payed off! The woofers you have chosen are very good ones and now you have the chance to explore their potential.

Good luck!

P.S. I did a quick simulation and for a closed box with a Qtc of 0,57 got a volume of 80 liters. A ported design would require 85 liters and a port tuned to 31 Hz and as we know, there are an infinite numbers of tunings for a reflex design.

[The golden mean]

FWW. Here you can download a free demo version of the Loudspeaker Lab 3 software. It´s a combined simulation/measurement program of Swedish origin I think. Downloaded it yesterday so I am unable to evaluate it yet. I also own an older version of Bodizio Software (of Melbourne) Sound Easy program. Their latest versions are also a combined program.

http://wduk.worldomain.net/acatalog/Software.html

I am a bit confused about the name of the program as installed it´s called Loudspeaker Lab 3 demo and on the site Loudspeaker CAD 6 lite.

[slr 5000]

thanks for your help guys it is much appreciated

[sreten]

Hi,

Around 50L sealed stuffed works, as does 100L lined vented tuned
to 22Hz to 25Hz. 50L to 100L sealed will also work but IMO for 100L
the very low tuning will not be audible as slow.

70L sealed is a good compromise. (q=0.6)

/sreten.