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Discussion Starter · #1 ·
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.

I'll keep you guys posted.

Mark
 

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Discussion Starter · #2 ·
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.

Mark

 

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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!
 

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Discussion Starter · #4 ·
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.

MArk
 

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Discussion Starter · #5 ·
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.

Mark
 

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Discussion Starter · #6 ·
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!

Mark
 

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Discussion Starter · #8 ·
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.

Mark
 

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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?
 

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Discussion Starter · #11 ·
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:

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

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.





 

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Discussion Starter · #13 ·
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!

Mark
 

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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.
 

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Discussion Starter · #15 ·
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.
Hi ridecolby

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.

The bigger boys are almost done.

Mark
 

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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?
 

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Discussion Starter · #17 ·
SUN OF NO SPUD

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!

Mark
 

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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 !!
 

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Interesting design, do you have an input impedance measurement?

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

Pete B.
 

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Discussion Starter · #20 ·
Short answer 4 Ω.

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.

Mark
 
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