ScanSpeak Resistive Vents

**Synthsayer** · **02-26-08, 10:19 PM**

This is a totally wrong sub design according to all theory but as an experiment due to tight budget, I used a left over Infinity 1230W Reference car sub in 1.5cu. ft. sealded enclosure. Had trouble getting good bass below 50Hz. Added Scanspeak resistive vent and it made a big difference. I don't understand the physics behind how these work, but others may want to try them, also.
More loudspeaker 'Black Magic'?

**Mike P.** · **02-27-08, 12:31 AM**

There's nothing 'Black Magic' about resistive vents, also known as aperiodic vents. Here's an article on their purpose and function, to give you a better understanding on what it's about.

http://diyaudioprojects.com/Technical/Aperiodic/

**Synthsayer** · **02-27-08, 11:24 AM**

Wow!!! Thanks a lot! That is the best description of this device I have seen yet. I had tried these back in late 1980s w Dynaudio 6 1/2" driver in small cabinet powered by an original NAD 3020. They sounded very good. They sounded so good that somebody offered me a fair price for them and I sold them.
Now I can't get Dyanudio drivers:-( I think the Morel uses the same hexagonal voice coil and magnet configuration. I will use Morel woofers for next project. I am using the Morel MD20T right now and am very pleased.
Back to the subwoofer. The article showed me something I failed to do which is to leave an opening between diver and Scan-Speak flow resistive vents.
These are so cheap and effective, I can't believe more DIYers are not using them. For any sealed enclosure, their benefit seems more than obvious.

Thanks again.
This is a great forum.
Peace

**DRB** · **02-27-08, 12:50 PM**

One thing to realize is that using these "vents" changes to slope of the roll-off at the bottom end of your sub's frequency response. Sealed subs feature a 12 dB per octave slope which can produce more extension when combined with room gain. I believe the aperiodic design is associated with an 18 dB slope.

**Synthsayer** · **02-27-08, 03:10 PM**

Many thanks. I will know to keep the roll-off diference in mind, now.
With the help of the tuning features on the O-Audio 500W sub amp, I think I am near to getting the sub, front speakers, and room, to come together better.
I would like to find a decent quality db meter or spectrum analyzer. An old Audio Control Richter Scale had EQ, low end boost, warble tone generator with meter all in one unit. I wish they were still making those. I have not checked their site. They may be.
Thanks again.

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