Woofer Towers, front-ported or rear-ported?

[Goldenboy]

Hello! I'm almost finished my bass towers, each is about 30" high by 11.5" high, and 17" deep. All in all, minus the braces, the volume is 70 liters.

Each of these towers will house a Focal 11" Polykevlar woofer. These two towers will be mating to an Open baffle MT portion in the likeness of the Linkwitz Orion. I will be crossing at 120hz.

This is for a music system, looking to remove any boomy sound if possible. So should I front port these bass towers, and thereby have the advantage of placing them closer to the front wall, or should I rear-port them. I am looking for the best and most articulate bass using these drivers that I can get. Keep in mind that I'll be crossing at 120hz with a LR4 XO. I'll be ready to cut the driver and port holes in a week, so all input is welcome.

Look forward to your opinions!

[gvinson]

Being the fanatic as suggested in the catch phrase of the forum...build it SEALED.....everything will be better.

[Goldenboy]

qvinson, I've definately considered that. But some of the reasons I chose to do a ported was because I have heard these woofers in ported 3ways, and it was amazing. No boom at all, but the room was large, thats why I'm worried that the front/rear thing might make a difference in my smallish room.

I guess I could still do it sealed, but the F3 would rise from 33hz (anechoic) to about 55hz. I know that inroom it will be better, but still it doesn't look great. Also, I've already built 70 litre enclosures, and the volume required for a sealed Focal 11K is about 37 litres. So I'm almost double the size.

But, keep the suggestions coming!

[Goldenboy]

Also, another reason I chose ported was because two different DIY'ers that have used this woofer ported, preferred them to sealed Scanspeak 8565 10" woofers. This leads me to beleive that if you match speakers with the right enclosures, they can defy common audiophile "rules". I will also be using parametric EQ on these woofers to tame the in-room response.

[planet10]

Originally posted by gvinson
Being the fanatic as suggested in the catch phrase of the forum...build it SEALED.....everything will be better.

And better than sealed, IMHO, is an aperiodic, or TL box... to turn your ported box into aperiodic box (TL is no doubt out of the question at this point), stuff the port with something with high acoustic resistance -- to reverse it pull it out. I don't often build BRs, (i do do ML-QW) but i like the port out the bottom -- if that doesn't work then out the back.

dave

[gvinson]

Golden...I understand the trade offs one has to make....it is just a measurable reality that sealed boxes offer advantages on so many fronts that they become hard to ignore, while having very few disadvantages.....and you are quite correct, some of the most admired designs that have been commerccially available are ported for their own reasons.....yet......bottom line: best of luck with your project. Let us know your results.

[BillFitzmaurice]

With the port in the back you have the option of gaining boundary reinforcement of the port output if you place the speaker close enough to the wall, or not by pulling it away. Booming is not a problem since that phenomenom takes place in the 80 to 160 Hz octave while the port only passes frequencies in the octave or two below that, depending on the box frequency.