[Pete B]

Interesting design, do you have an input impedance measurement?

Where do you face the opening when using it in room?

Pete B.

 

[Pete B]

Did you notice that if you back compute the 1W sensitivity from the AkAbak simulation - I get about 90 dB/W which does not agree with your figures for hornresp.

Any reason for the difference?

More accurately:
Seems it produces 115 dB at 400 W according to the AkAbak simulation
10 * log (1/400) = -26.0 dB
1W = 115 - 26 = 89 dB

Pete Basel

 

[Pete B]

I see, now, that your more recent sims seem to agree fairly well showing about 90 dB with 1 W. I didn't look closely because they're hard to read. But different figures are shown in post #8 where I was looking, in particular about 9.43% efficiency which I believe is not possible with this configuration.

- 3dB point seems to sim at about 32 Hz.

 

[Pete B]

I simmed a pair in a 55L box vented tuned to 28 Hz, 2pi space as a sanity check:
Passband 2.83V sens is 91.6 dB
1W 1m is 87.6 dB
Max SPL at 400W is 113.6 dB in the passband

-3 dB is 29.11 Hz

Excursion stays below Xmax by 1 mm down to about 25 Hz with 400W input.
Max SPL at 30 Hz is 111 dB
Max SPL at 20 Hz is 101 dB
this is again within linear Xmax, I'd expect 3dB more in actual use,
more for a pair, and more with room gain.

I'd expect it to do 3 dB more with a bit of over-excursion and
more power. The 400W is into 4 ohms, and a 500W amp with
a few dB of peak headroom should handle program peaks and
be a good match for the pair allowing for a bit of over-excursion.

Pete Basel

 

[Pete B]

I am certainly interested, Mark.

 

[Pete B]

Mark and I Tested this little "unhorn" in a relatively small room in his house. It sounded great. The bass had huge dynamic range in the music we were using. It belted out the lows, i expect with some help from room gain. The little box was quite astonishing. It was clean and articulate. The sound itself showed no compromise even when pushed with over 300w, in fact, the more wattage we fed it, the cleaner it sounded. It was kind of impressive. i know the roll off is a little steep for a house, it was great in this small room, but in the car is where it really shines. We still need a bigger amp for in the car to get to the levels i'd like for music, but it did sound great on everything i played. no stress, no complaints, easy 115+dbs in the car on roughly 40w. cabin gain in a small space is like no other i guess.

I don't doubt what you heard, that the system was astonishing, however it might just be mainly due to the exceptional TRIO8 drivers. A properly designed ported box might be as good if not better. The sims when compared on equal ground are not very different. The ported box would also see significant gains in room.

Pete B.

 

[Pete B]

Hi Mark,

Let me just suggest that given the claims of a new and different design here it would be instructive to build an "optimal" vented box system as a baseline for subjective evaluation and comparison. Just my opinion.

Let me also offer a few comments about these recent simulations results. First the vented system would have a flatter response if you either tune lower, say 20 or 25 Hz or make the box smaller. I prefer the lower tuned alternative.

Also, if we consider the range of interest to be 20 to 50 Hz for a moderate sub it is interesting to take a closer look at your simulations. The vented box produces 90 dB at 20 Hz whereas the other two are 5 dB less efficient at 85 dB - and this will only improve for the vented box with a lower tuning. At 30 Hz the vented box is at 102 and horn1 is at 98 for 4 dB less output, horn 2 has 3 dB more being peaked at that freq with about 105 dB output. Horn2 picks up a few dB more in the passband probably due to that fact that the vented section is tuned too high, and there is some horn gain however this horn is optimal with peaked output up around 120 Hz - not down in the 20 to 40 Hz range. Horn2 is twice as big and therefore is not on equal ground with the others.

It would be interesting to build both and use a digital EQ to match their responses and see if the subjective improvement is due to something fundamental or just differences in FR.

Pete Basel

 

[Pete B]

Do me one favor and try tuning the vented design to 20 or 25, it is peaked as your simulation shows at 30 and with room gain will just not be right making it a not so fair comparison.

Pete Basel

 

[Pete B]

I just want to mention again that I think the TRIO8 is an excellent driver and as far as I know the only 8" XBL design. While it is excellent to explore new design ideas we should also get to know the true capabilities in a traditional vented design.

 

[Pete B]

Thanks Mark,

I suggest keeping the box volumes the same to put them on equal
ground from that perspective. I think I did that with the 55l simulation.
Then tune for whatever provides the best in room response. 20 or 25 whichever
sounds better with a 3 or 4" flared port. 25 should do if you
want it as close as possible (without peaking) to the horn.