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Discussion Starter · #21 ·
Ok gents here is some background info on the design. It was simulated using Hornresp. A great program created by David McBean. The true aim for this box was for a car sub-woofer. But when I did some testing in my home I found that it was a little bit better than I expected. Let me rephrase that. A lot better than I expected.

It is interesting to compare the simulations to the actual measurements posted above. Now when comparing remember that I couldn't get a proper floor wall corner in this room. So I did the second best thing. Close!

Here are the simulations:



Here are the actual measurements:

30hz 84db
35hz 92db
40hz 100db
45hz 101db
50hz 96db
55hz 95db
60hz 95db
65hz 95db
70hz 94db
75hz 93db
80hz 92db
85hz 85db
90hz 97db

Taken with a Rat Shack SPL meter at 1 meter distance no use of a calibrated correction. I know you guys are well aware of this meter having a roll off starting around 35 hz. That was going to be my next statement. The sub is almost flat to 30 hz when located in a corner.

Why post the simulation? Well just to show that it is pretty close to real life.

Now there is some work being done on a couple of TRIO8 boxes and the plans and cut sheets. So bear with me a bit and as soon as I have everything worked out you will know.:foottap:

Mark
 

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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
 

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Discussion Starter · #23 ·
Hi Pete

AkaBak calculates Spl in 2 Pi environment. I measured in a lossy .5 Pi environment. Hor resp has been presented in 1 Pi which is usually the closest to what I get in real life
 

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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.
 

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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
 

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Discussion Starter · #26 ·
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.
With this box the efficiency is interesting. If you are inclined download hornresp and plug in the numbers and see for your self at different frequencies how it fares. In a normal wall location you'd expect 92 to 93 db. Your estimations for ultimate loudness in the conventional box are a bit optimistic when you consider that X-mechanical in the deign is 18mm and that is getting some greater amounts of distortion.



Mark
 

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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.
 

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I have been reading it. I am not one for graphs and such but I am still very intrigued by this idea. I hope you are still going to do a larger one with 10's or 12's. Glad you're happy with it.
 

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Discussion Starter · #30 ·
I have been reading it. I am not one for graphs and such but I am still very intrigued by this idea. I hope you are still going to do a larger one with 10's or 12's. Glad you're happy with it.
Hi Colby

Unfortunately graphs work well on the net. I agree that they can be fudged and so on. But I try very hard to present as close to real life the simulations and then the measurements. I have been doing this long enough to come to respect the programs that I use. They generally paint quite a realistic picture when you understand what they calculate and what conditions you are asking the program to calulate relate to the real world.

As an example the .5 Pi measurements for this UNHORN box are not pposted yet because I have not had the time to actually do them. When I do I will do it in a car at 100 hz because a car is the closest thing to a true .5 Pi space that most of us have. I choose 100hz because it is just at the beginning of the cabin gain that we usually get from loading a box into a very small sealed space (a car cabin).

One thing is for certain. This box does not break any efficiency records. It is much more efficient than either a vented or sealed cabinet the same size. It does beat them in it's ability to play louder by 3 to 4 db. It does do this with very low levels of distortion from 35 hz up. In a car with a bit of EQ and a 25 hz highpass filter it is solid to 25 hz which is down right fun. I love it when I'm driving in the city and kids are booming away in a car next to me and I pop in a roaring pipe organ track. I generally get more than a couple of looks! Even us old fogies who listen to classical stuff like to rock and roll in our own way!

Adam tested out some nasty low frequency rap music and the box shined. Not a bit of problems. So As far as I know when I get a good readable set of plans they will become available.

Pete

I have some proper test results but I have had to format my computer twice in the last week to try and kill a very nasty worm. I think I have fianally vanquished the sorry little beast. IT found it's way onto anything that was plugged into my computer including mu cell phone that I take all my pictures with. Evill little thing. So as of now if I get a clean bill of anti virus health I will try over the next couple of days to post a comprehensive discussion as to the pro's and con's of this design. Maybe it will be of interest.

Mark
 

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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.
 

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Discussion Starter · #33 ·
Pete you are absolutely correct. The TRIO8's are excellent drivers. And yes you can get great results from venting them. I have run all the sims as well. Remember that this is an experiment. Nothing greater or less than that. It works well. Sounds great and definitely not box like. So there is something to be had from this type of a design. But break all efficiency records it does not do.

Mark
 

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Discussion Starter · #34 ·
So as of now if I get a clean bill of anti virus health I will try over the next couple of days to post a comprehensive discussion as to the pro's and con's of this design. Maybe it will be of interest.

Mark
What this box configuration does best is load a driver into the room and simulate a vented enclosure. At it's worst it equals the efficiency of a normally vented enclosure.

So what's the benefit?

The sound. It's all about the sound. It's more lifelike. More like a horn.

Many have made comments about open baffle systems sounding more lifelike. Some have designed "u" and "h" baffles that partially load an open sided woofer into the room they placed in. The resulting sound is exceptionally clean. If the woofers have sufficient excursion capability they can even generate decently high SPL's. But they are at best 3 db less efficient than a comparably loaded driver in a vented enclosure that is used to isolate the rear wave from the woofers cone.

You have to trade some efficiency to get the low distortion sound in an open baffle.

With the unhorn enclosure you get your cake and can eat it to. The sound of an open baffle and the efficiency of a vented enclosure or slightly better. What has been built and simulated is proof that it works.

To compare the acoustical environments on an equal footing when modeling vented enclosure and the unhorn enclosure I worked up the following examples in Hornresp. When using different programs there is to much variability in the formulas used in the programs that can calculate sound pressure level in a range of reflective environments. As the only other program I know of that can do this type of a comparison is AkaBak or Hornresp I used Hornresp as it is a bit easier. It has allready been demonstrated that Hornresp is pretty close to the actual measurements so I think that the resulting graphs speak for themselves.

All of them are modeled in a true corner loading. All have 1 watt into 4 Ω or 2.00 volts

The first is a dual TRIO8 vented to 30 hz

The second is the same drivers in the as built UNHORN.

The third is an example of a tweek'd UNHORN type enclosure using two TRIO8's. The volume is greater by a factor of two and the flares are slightly different. But the point being the unhorn type enclosure can be tweeked to bring out even greater efficiency. It can even be pushed farther up in efficiency idf a narrower pass-band is acceptable. Just as in a bandpass enclosure. The benefit is that there is not the packed port distortion that so often accompanies a bandpass sound. This happens because the ports sizes are usually compromises between what will fit and what will work. The optimum size port in a bandpass enclosure is usually to large to work in a given box. There are many ways to balance that design challenge in the unhorn box design.

This may very well be a new type of enclosure for loading woofers. I'm not sure. I know one thing that when ever you think you have invented a new widget there is some old patent around that shows you there is nothing new under the sun. Just variations on a theme.

But this is an example of working out of the box. It's all to easy to say something can't or won't work. It's a lot harder to come up with a why or a because. This little thread is an example of a why not question that worked itself through to a useful end.

The final prototype to be sent off for testing is almost done. It's hard to get paint to dry in a cold shop! A prototype built by an independent party is up and running and he is getting the same results. So when all people are happy more info will be posted.

Mark
 

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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
 

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Discussion Starter · #36 ·
Hi Pete

When I finish this crazy hecktic job I'm on I plan exactly that. A head to head comparison. But the comparison will be fair. Both boxes about the same size and tuned to 30 hz. No smoke a mirrors.

From listening to many boxes and drivers here is my comparison. There will be but one thing to differentiate the two lack of overtones from the Unhorn. That is the greatest difference that I'm hearing for what three months now. Efficiency is close to the same. It can be tailored a bit as I have posted and as I have measured.

New is a very dangerous word in loudspeaker design. I'm guessing somewhere someone has done this before. But I for one enjoy listening to it. There is a gentleman who has built one to and has raved about it's sound quality as well. So I'm not the only one. It is a fairly simple box that gets you some very clean sound. I just have to put some more time into measuring a direct comparison against a vented design with the same drivers.

Something called work and making a meager living is getting in the way!

Mark
 

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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
 

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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.
 

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Discussion Starter · #39 ·
Ok Pete given that you have some definite ideas as to what you would like to see and given that in about a week and a half i will have the time lests iron out the details. How big of a box and at what tuning frequency. And from that point how do you think it would be a fair comparison? You convince me I build and test. Sound fair enough?

My thoughts are two boxes one Unhorn that I have. The other tuned opitmaly in an enclosure to 30hz. i agree that with two TRIO8's a 30 hz enclosure with optimal tuning will be smaller. Why do you feel that going down to 20 or 25 hz is a good comparison to a box design that poops out at 25hz?

Mark
 

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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.
 
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