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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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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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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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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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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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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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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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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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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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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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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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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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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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Discussion Starter · #42 ·
Hi Brett

Here is the File that you can import into Hornresp. If you can import this you can do a AkaBak export from Hornresp. So you will have a leg up on the foollings around.

Mark
 

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