Ok proof of concept bass section is alive and kicking.
Side view
In the room being measured, prodded and poked
De plan man
Maximum SPL at just under X-max 500 watts.
So this design quirk of an idea a couple of months ago has grown into something useful indeed. So parts for the dual SDX7 are sitting in the shop and waiting to be assembled.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
One point of clarification on the post above. The drivers used in this test box were two pcs TRIO8 not SDX7.
This was a different application. Basically how loud could I get a pair of 8 inch drivers to go in how small of a box.
The reasoning to use the TRIO8 drivers was to validate the design. This is not a conventional tapped horn but a bit of a hybrid. It's actually quite a bit smaller than a tapped horn. I just had to find out if it works as designed in Hornresp. So now that the concept has been proven on two very different sized box designs I'm going to build the version I started this thread for. The dual SDX7 that goes down lower.
Can never be over confident when you are working on a new design. It's much better to take a look and see what's going on and if you are on the right track. The track is clear and straight the design concept is firmly linked to the actual product. What Hornresp told me was going to happen did happen. A good place to be when you are trying something new.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Mark, can you clarify on the specifics of this design? Looking at that side profile it seems as though putting the side on would result in a totally sealed box. I've always been interested in tapped horns and weird bass boxes; this looks very cool!
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
This view may help a bit:
You guys are just to much into thinkin!
It helps if I post more pictures I guess. I gave this design to a couple of youngins for about 1/2 hour and they toasted it. I'm still trying to figure out the cause of the failure. If I can prove it was the amp then I still have a great design. It performed as spec'd and had a great sound. But if as it is setup it kills woofers then I have a bit of work to do.
Now here are the particulars of what they were doing. They had the sub pumping out 112 db constant and I had the Rat Shack meter set on slow. So the peaks were well above that. I was measuring 5 watts with a slow multimeter. So again the peaks were higher. All this in a car that I have been listening to the sub in for about 5 days before it went boom. I'm pretty tough on speakers. I listen to Monster organ music and large nasty orchestral works with bass drums that double as DIY CPR machines. I never hurt it a bit. In fact I was going to put this design to bed and go for it whole hog. But now I just gotta figure out what went wrong. My car amp is wimpy at about 40 watts. So this is my first point to check. Second point is rather easy in that the inner driver may be woofing alot more than the outer driver. A plastic panel will let me figure that out in short order. So I will do the due diligence and figure out what is going on. I'll keep you guys posted. As it sits the bub end really kicks butt. I'm just a bit on the cautious side before I post the rest of the design.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Ok gents
I had a hunch and a great mind from down under had the same hunch. We have bounced ideas back and forth a couple of times and I think I have a solution proposed to fix what went wrong. So I'll put a bit more elbow grease into the design instead of simulation time and see how she measures. I have to juggle the location of one of the drivers and if it works as planned then we have a go. The new simulation checks out very well. So lets hope this one is a go.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Now hear this!
OK now I'm cooking with gas. This info is for the proof of concept box. The dual TRIO8.
The gentleman who invented Hornresp has made my life very easy by allowing easy porting from Hornresp to a program called AkaBak. AkaBak is a program that is short on the GUI and long on the number crunching.
The out come of all this fooling around is a driver placement that makes everything work as planned. The box has a new fold but the parameters are identical. So here it is:
The size is way smaller. Just over 2 cubic feet from just over 4 cubic feet. All the wasted space has gone bye bye. So to button up the box and do measurements is the next thing to do. THat will happen over the weekend. Weather permitting of course.
Below is an independent simulation done by Don Hills from New Zealand. Power input is 400 watts into 3.6 ohms. 2 Pi space. Or outdoors. If you throw this into a room it gets much louder!
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Looking forward to the measurement results to see how it performs! Will it be measured in car, in room or both? At what frequency is over excursion an issue and will you be applying a Hi-Pass filter?
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Hi Mike!
All good questions I appreciate it Mike.
Measurements will be made for car and home use.
As simulated this is what I get:
The 80 watt post is for people wondering where it runs out of gas without a high pass.
This box is really a car sub masquerading as a home sub. It can do both. But it is the proof in the pudding before I go all the way on the twin SDX7 setup. The SDX7 box will trade efficiency for bandwidth. This box is all about efficiency.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
This is very interesting. I am eager to see the next iteration for the bandwidth optomised box. Is this a folded horn or did I miss something in the post?
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Looks can be deceiving. A conventional horn has a progressive expansion from driver to horn mouth. This is obviously not a progressive expansion. More or less it is two funnels turned spout to spout. What it acts like is two coupled vented enclosures. More or less like a bandpass enclosure. You get a bit more gain than a normal bandpass though. It is tapped in that the drivers are seeing an effectively longer path length than there is in the measured length. So this is a bit of a hybrid enclosure. As far as I know it is rather unique. Probably not a first. There are no audio firsts. Just progressive standing on the shoulders of giants. But I have some results for the frequency response for this cabinet. They are preliminary as my computer and my sound card are at odds. So here it goes:
All referenced to 1 watt 2.00 volts into 4 ohms. Measured by Rat Shack SPL meter at 1 meter with no frequency compensation. So these are indeed raw measurements. But other than the reading at 85hz it is pretty good. Plus or minus 3db around 96db/watt is a very fair assessment of the box. This is in a corner position by the way. The drivers are just under 84db/watt by themselves. So this is not a bad gain in efficiency.
As for listening this is a force of nature. We played around with it yesterday evening and with 16watts we had peaks of 128 db in a 10 x 12 ft room. Response down to 30 hz was solid. Some tracks using a great big pipe organ had notes down to 16hz at 108db. We did not get the full impact of the 16hz but we could count the pulses and feel a hint of that low end. The room was pulsating. So considering the size of this thing I think it is a keeper. It's small enough to use in a car. And it speaks with enough authority to smack down most commercial subs. It's genuinely hard to believe how much bass can come from two 8 inch drivers.
Wow! That is impressive for a pair of 8" subs! Since your concept has apparently proved itself, it would be interesting to see what a "Unhorn" with larger subs will do!
I have to clarify that comment on the power usage. I got my wires crossed on that one . We used an average of 16 watts or less but we peaked at 128 db with 36 volts into 4 ohms which works out to 310 watts. The sub behaved as spec'd if you look at the maximum SPL simulations from Hornresp.
Sorry for the misleading statement.
As for the bigger one with the dual TRIO12's it will come in two sizes. A smaller 260 litre box and a high efficiency box around 560 litres. Been working on this one since late summer. All I could think of when testing the 8 inch box was. What am I doing making this bigger? It's allready a monster as is!
Wow this is very cool. I can't wait to see the larger version. Do you already have the 12's maybe two 10's would be sufficient! LOL. Anyway, way to go on proving this concept.
This box with some muscle behind it (300watts) is very impressive. If you listen to normal rock and such it is more than what most people will ever need.
Re: 2 x EL70 plus 2 x SDX7 = hard to beat combination
Terrific design Mark, I guess the design could be
considered "son of spud", but I'm quite sure it would fit into more modest sized HT rooms than it ever could. Will plans, or a cut sheet be available for the Trio 8 Unhorn?
This is not related to a tapped horn other than the point of the drivers on the path of the enclosure. What it is is a double tapered resonant pipe. It also takes a page or two from the tapped horn idea. Which by the way takes a page or two from other previous work. We all stand on the shoulders of giants!
Nothing new under the sun. Just variations on a theme. The main point being I can listen to those variations on a theme!
I was about to pull the trigger for 4 of the Trio 8 drivers for a traditional PR application, this has me rethinking that project. If I were to replicate your Unhorn Trio 8, could you provide dimensions for the enclosure and baffles? Thanks Mark for a fascinating project !!
Complex answer is I have to remeasure the box and I'll post the complex impedance. That will happen tonight as I am still working.
Point and shoot it into a corner for maximum efficiency. As with all horn type loudspeakers you can really tailor the sound by how close you put it to room boundaries. In a proper basement corner that is 100% reflective you get the maximum reinforcement from the room reflections. Along stud walls depending on how loud you are playing you may find a rub or buzz that you didn't know you had before.
The sound is very clean. Not boomy. If there is no bass in the source material you don't get any. When there is bass you get it loud and proud but very cleanly. It takes a bit of getting used to but it is most life like of all methods of bass reproduction.
During testing I had it hooked up to a bridged Parasound HCA-100A amp so I get 400 watts into 4 Ω. We were testing it using a organ disk that really puts systems through their paces and the peak meter reading for wattage was 310 watts. The peak SPL in a 10 x 12 room was 128 db. Our pant legs were flapping. Has to be heard to be believed. With a 25hz high pass this little monster can knock over quite a few bigger subs.
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!
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:
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
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
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.
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.
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.
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.
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