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Re: B&C Sub designsSo these measurements are just the old OAP boxes with a 2.5" tall port and you added an 8" port wall and a 12" port wall and measured? Interesting that 3db peak at 38 hz on both versions. What freq was the excursion minimum at? I would be a little careful about a boost at 54 hz on that as it may be a frequency rangewhere you are excursion limited. Certainly much better than the original. BTW I would think that what you call port choking at 50hz and then abruptly cutting off at 45 hz would more accurately be just the fact that the output of that design drops abruptly at those frequencies. That is because the "port" in the original OAP design had a resonance around 75 hz that just failed to help the box's output down low. All it did was provide a big hump in the response around 75 hz. The term port choking would refer to the idea that at high output the port airflow becomes turbulent and the port fails to perform as it did at low drive levels. It is likely that your 8" and 12" deep port designs will experience port compression effects at high drive levels using those TBW100 drivers. So if you measured either of those ports with 2.83v and again with 115v (for example) you would find that there would be significant differences between the two with the output in the 35 to 45 hz range being sacrificed at the higher drive level because the port isn't able to perform properly and provide the output in that range that it did with the lower drive level.With all that said, either one will be much better than what you had.Loren
Re: B&C Sub designs
So these measurements are just the old OAP boxes with a 2.5" tall port and you added an 8" port wall and a 12" port wall and measured? Interesting that 3db peak at 38 hz on both versions. What freq was the excursion minimum at? I would be a little careful about a boost at 54 hz on that as it may be a frequency rangewhere you are excursion limited. Certainly much better than the original. BTW I would think that what you call port choking at 50hz and then abruptly cutting off at 45 hz would more accurately be just the fact that the output of that design drops abruptly at those frequencies. That is because the "port" in the original OAP design had a resonance around 75 hz that just failed to help the box's output down low. All it did was provide a big hump in the response around 75 hz. The term port choking would refer to the idea that at high output the port airflow becomes turbulent and the port fails to perform as it did at low drive levels. It is likely that your 8" and 12" deep port designs will experience port compression effects at high drive levels using those TBW100 drivers. So if you measured either of those ports with 2.83v and again with 115v (for example) you would find that there would be significant differences between the two with the output in the 35 to 45 hz range being sacrificed at the higher drive level because the port isn't able to perform properly and provide the output in that range that it did with the lower drive level.
With all that said, either one will be much better than what you had.
Loren
