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Old 10th February 2011, 06:40 PM   #1
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Default Analysis Paralysis: Need help moving forward

This is supposed to be fun. OK, but my naturally occurring OCD in combination with my desire to not waste time building something that will be very disappointing is preventing me from getting anything done. I have limited time to myself and a hobby like this with two young kids in the house doesn't mix well. It doesn't help that I'm still a beginner and I wish to understand hugely complex issues of speaker and crossover design before I make decisions. That is not gonna happen any time soon for me. It seems like the more I read, the more questions I have. I need help.

I thought my biggest problem at this point in time was going to be a choice of what plans to use to build some boxes for the Fostex full range speakers I've had waiting to be used for a while. Instead I got thrown a curve-ball when I was gifted these drivers for Xmas from Madisound's Aura sale.

https://www.madisound.com/store/prod...oducts_id=8992

Not what I would have chosen, but the speakers I was interested in were sold out already. My wife was sweet enough to entertain my preoccupation with all things audio. The speakers are considered "full-range" so I did a quick post in the FR forum asking for suggested uses, and got some ideas to try open baffles and etc. I even started to make some baffles, but it occurred to me that they really couldn't serve any purpose for me and would take up too much room.

The purpose I saw these little speakers possibly serving for me was as a HT system that would finally separate that daily duty for my family and its wear and tear from my stereo system which uses mostly tube based amplification.

And so the head scratching began.

My first inclination was to pair these drivers. I have enough to make 5 channels. I could wire them in series to achieve an 8ohm load which would be easy for any HT receiver to drive. However, in my beginners simple view, their response starts to present issues by the time you reach 3kHz where it has already fallen off 6dB from the 2kHz mark and it seems like a bit of a mess when you hit 6kHz. Not issues I thought I would be happy with or that I could figure how to address with filtration. That made me think that I should incorporate a tweeter and accept that these are more of a "extended range" speaker, which brought me to the idea of the seemingly popular MTM format. I searched a bit, and I came across this Dayton tweeter which appears popular for DIY projects.

http://www.parts-express.com/pdf/275-078s.pdf

More questions. What about crossover points? Was there enough overlap in the right frequency range to avoid poor performance from one or the other driver? What order crossover would be needed?...What about attenuation of the tweeter or a Zobel filter for the woofer? Sheesh...I tried to step back and start with the fact that I already had these little Aura drivers and what should I put them in?

I spent some time playing with WinISD to try and find a cabinet design that will be a good compromise between response, SPL and size. Most of the online calculators I have tried appear to want this driver in a vented enclosure. I went through the WinISD tutorial and modeled with two of the Aura drivers in a vented enclosure. The default output gave me a cab somewhere in the range of 11 liters tuned to about 60Hz if I recall, obviously a design trying to maximize bottom end extension. I thought it was too big to be realistic in my living room which is about 14' X 20' with a listening area of about 10' X 10'. I noticed while I was playing with the volume of the box and tuning frequency that I wasn't gaining much in bottom end extension that was usable as response seemed to dip as soon as it hit 100Hz anyway. I decided that since I would be using a subwoofer in the system that I didn't care much about performance below 100Hz and tried to get the smoothest response I could down to that point and then just allow it to roll off. To my eyes 7 liters tuned to about 85Hz seemed to be a good compromise. It made it through 100Hz pretty well, but then fell like a rock at 80Hz. It also appeared that I was able to maintain over 88 to 89dB up to 1kHZ where the graphing ended which matched the specs of the tweeter closely. Beyond that point I was in the dark.

So now comes the real gauntlet, crossover design. I'm assuming that I can trust the WinISD calculations as a good starting point for the box design and that the subwoofer can effectively take over the job from these surrounds at 100Hz. Also that nothing nightmarish happens above the 1kHz plotted point before the tweeter can take over since the factory response curve of the driver looks pretty good there. I'm hoping that I'm not a complete idiot about interpreting the response graphs WinISD generated, as well as my interpretation of the driver's graphs and that I haven't completely missed some other pivotal aspect of speaker design in all my research.

I've read you can easily spend quite a bit more time and money on a speaker's crossover than its drivers and cabinet materials combined. I believe it. I am trying to figure out what is really necessary to attain good sound, if possible, from these speakers that will leave me with the feeling of "I got a pretty good bang for my buck and the time I put in was worth it." As opposed to "Why did I waste all my time and money on trying to make these speakers sound good." Let's face it...these Aura drivers only cost about $5 each after shipping. The tweeters would come in at about $10.50 each. I have a good amount of plywood and HD particle board on hand...it wasn't free though. Regardless of all the speaker's component costs, or lack there of, I am after a logical design that takes the specifications of the components and their application into consideration.

What should the crossover point between the Aura driver and the tweeter be? 2000Hz? 3500Hz? 5000Hz? and what's your rational behind choosing that point?

In the name of simplicity but also to provide protection for the tweeter from damaging frequencies I thought I should use a 2nd order filter for the high pass...for the low pass to the Aura driver I was hoping to use a simple 1st order filter. I know there are simpler or more complex solutions, which do you feel are necessary or would provide the best result per dollar?

I shouldn't have to worry about anything below 100Hz being delivered to the surrounds from the receiver.

The tweeter is rated at 89dB, and a pair of the Auras graph to an efficiency of about the same level...do I need, or is it worth the investment, to attenuate the tweeter with an L pad?

What of Zobel filtration? I've read it is more appropriate to be used for woofers to keep the impedance level flat as you move up the frequency range. Should I integrate a Zobel in to the Aura's filter? What about the tweeter?

For reference, I have acquired a nice Marantz SR7000 receiver as the heart of this HT system for a very good price. I believe it is rated at about 80 watts into 8ohms (not positive) definitely not more than 100watts though.

I have also acquired a pair of the 10" RPM plus Aura subwoofers that Madisound had on sale with another gift card I got for Xmas. It is my intention to use them in conjunction with my old Counterpoint SA12 amp to provide the systems response below 100Hz . It will deliver about 140watts into a 4ohm load, so I was thinking of simply splitting the subwoofer signal to the stereo amp and allowing each channel to drive one sub. I could also use the sub system to supplement the bottom end of my stereo audio system by taping into the Marantz from my tube preamp if I desired. I'm not sure what enclosure for the subs would be optimal...I have considered separate cabs, push pull etc. but that is on the back burner until I get the surrounds resolved.

Last edited by chromenuts; 10th February 2011 at 06:49 PM.
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Old 10th February 2011, 07:04 PM   #2
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Which Fostex?

If i were you i'd get my feet wet with the FR. You'll learn much. Personal experience can be much more useful than vicarious experience of others.

dave
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Old 10th February 2011, 07:33 PM   #3
badman is offline badman  United States
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Quote:
Originally Posted by planet10 View Post
Which Fostex?

If i were you i'd get my feet wet with the FR. You'll learn much. Personal experience can be much more useful than vicarious experience of others.

dave
What he said. Nobody gets it TOTALLY right the first time, even successful designs that sound superb often teach you something new.
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Old 10th February 2011, 08:10 PM   #4
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Hi Chromenuts. I can relate to the analysis paralysis comment. I think I maybe somewhat OC myself. Hey just have a look here I joined in 2003 and I probably only have three "fully completed" projects in that time... My chipamp amp, my measuring microphone and preamp, and a sound card pre-amplifier (for amp measurements). I originally joined to ask some questions about my upcoming speaker project (My MTM's) which whilst you could say are mostly complete, are still a work in progress.

I third the idea of just doing the fullrange. Don't think of it as being the be all and end all, just a step on the path of a never ending journey

Build a couple of boxes and bolt one in each listen to them...

Put some stuffing in the boxes and listen again. Can you hear the difference. If you want to be obsessive about it, try lots of different materials for lining the boxes and see if it makes a difference (I know I did!)

Get a copy of holm impulse and a cheap computer mic (if you don't already have any gear) do nearfield measurements, you will be surprised about the difference that different materials (in the box) can make to the smoothness of the FR.

Once you are used to the sound of these speakers, you can try your hand at some response shaping circuitry, perhaps a notch filter or two, maybe a shelving filter, see how it affects the sound, and whether there is an improvement or not.

When you have exhausted the possibilities you could decide to try adding a tweeter, or you could just decide OK I'm ready for something a bit more challenging now and gve them to the kids and start on something new Better to have played around and learnt on some $4.50 drivers, that to buy some $100+ drivers not quite liked the results and gotten disheartened.

Hope that helps and doesn't make things worse

In a way I was lucky, when I started playing with speakers I didn't have access to any info on how to design speakers, I just bought drivers and pre made crossovers and put them together. I didn't have the knowledge to make my own crossovers and didn't have access to information to tell me how to so made do with what I could get. It wasn't optimal (not by a long shot) but my friends were jealous because they sounded better than what they had bought... many drivers crossovers lpads etc later, I had learnt a lot, then I stumbled upon diyaudio If I'd had access to all the info I do now when I first started, I probably never would have gained the experience that I did. Sometimes you've just got to build it, learn from it, and make something better next time

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Last edited by wintermute; 10th February 2011 at 08:16 PM.
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Old 10th February 2011, 08:50 PM   #5
ScottG is offline ScottG  United States
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Almost everyone seems to do this wrong.. (and I include myself in this list.)


I'd never recommend starting off with drivers - even if you already have some.


Instead start off with *full* modeling software where you can input any number of drivers and create *many* "virtual* designs. (Sound Easy, LspCad, Leap 5 Complete, Basta, or even a "mixed" grouping of freeware from the FRD Consortium and other sources.) "Full" meaning enclosure modeling, baffle modeling, and crossover modeling - preferably with measurement capability integrated. You will of course still need measurement capability, but you won't need if for virtual modeling to learn the software, and you won't need it integrated into more sophisticated modeling packages (..that have import capabilities).

THEN form an idea of the design you are interested in. Apply that to software you are experienced with, and finally go out and purchase the drivers to make it a reality, or use the drivers you have.

Analysis is good, it's just a matter of properly leveraging it.


There are of course other avenues: purchase retail/wholesale, or choose a well documented proven design, or consider an active solution with measurement capability.
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Old 10th February 2011, 09:45 PM   #6
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Originally Posted by planet10 View Post
Which Fostex?

dave
I have a pair of 206e and a pair of 107e. Building the FR drivers into some kind of horn is really where I WANT to be right now as far as my own audio interests are concerned. I've been waiting to use them with a pair of Quicksilver Horn Monos I purchased around the same time for that purpose.

The Aura drivers have my focus for a few reasons:

#1 By building some kind of HT system I can isolate my tube audio equipment which has seen daily use for almost two years now playing audio for movies/videos and then use it only for my music enjoyment. I don't want that kind of daily use to continue. I know the tubes need replacing, and I want to isolate the equipment and then invest in the new tubes.

#2 As a family we really spend a lot of time watching movies together in the evenings and on weekends. Instead of spending a fortune going to the theatre all the time, we browse the discount DVD bins and find stuff we each like and then watch them together at home where we can make our own snacks and relax. We've only ever had the stereo audio from my system, which does quite a good job, but I think they would really enjoy having a "real" HT system.

#3 Maybe this should be #1, wifey got me these drivers as a gift. I don't want her to think I didn't appreciate that fact by putting them on a shelf. I think she already regrets it to a degree since she has had to listen to my techno-babble for two months while I tried to figure out what to do with them

This whole process does seem a bit backwards and too complicated as Scott mentions, and its due to my preoccupation of using these drivers.

Perhaps a forced simplification is in order. If I want the Auras used for an HT system then maybe I should decide to use ONLY the Auras in the cabs I had experimented with modeling in WinISD. This would remove all the complexities of the two way crossover if I ran them full range. They still wouldn't receive anything below 100Hz in this application if I use the separate sunwoofer.

The only question I would have in this kind of application of these drivers, which seems to be line very much with the general advice of experimenting with simple designs first, is how would I go about trying to smooth out the response of these drivers above 3kHz?

I am very interested in getting a mic/preamp setup with some sort of laptop USB interface so that I can measure and learn about what I am accomplishing with some of the freeware like TrueAudio, ARTA or any other shareware applications you guys might recommend. Thank you very much for your feedback.
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Old 10th February 2011, 10:17 PM   #7
ScottG is offline ScottG  United States
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Quote:
Originally Posted by chromenuts View Post
I have a pair of 206e and a pair of 107e. Building the FR drivers into some kind of horn is really where I WANT to be right now as far as my own audio interests are concerned. I've been waiting to use them with a pair of Quicksilver Horn Monos I purchased around the same time for that purpose.

The Aura drivers have my focus for a few reasons:

#1 By building some kind of HT system I can isolate my tube audio equipment which has seen daily use for almost two years now playing audio for movies/videos and then use it only for my music enjoyment. I don't want that kind of daily use to continue. I know the tubes need replacing, and I want to isolate the equipment and then invest in the new tubes.

#2 As a family we really spend a lot of time watching movies together in the evenings and on weekends. Instead of spending a fortune going to the theatre all the time, we browse the discount DVD bins and find stuff we each like and then watch them together at home where we can make our own snacks and relax. We've only ever had the stereo audio from my system, which does quite a good job, but I think they would really enjoy having a "real" HT system.

#3 Maybe this should be #1, wifey got me these drivers as a gift. I don't want her to think I didn't appreciate that fact by putting them on a shelf. I think she already regrets it to a degree since she has had to listen to my techno-babble for two months while I tried to figure out what to do with them

This whole process does seem a bit backwards and too complicated as Scott mentions, and its due to my preoccupation of using these drivers.

Perhaps a forced simplification is in order. If I want the Auras used for an HT system then maybe I should decide to use ONLY the Auras in the cabs I had experimented with modeling in WinISD. This would remove all the complexities of the two way crossover if I ran them full range. They still wouldn't receive anything below 100Hz in this application if I use the separate sunwoofer.

The only question I would have in this kind of application of these drivers, which seems to be line very much with the general advice of experimenting with simple designs first, is how would I go about trying to smooth out the response of these drivers above 3kHz?

I am very interested in getting a mic/preamp setup with some sort of laptop USB interface so that I can measure and learn about what I am accomplishing with some of the freeware like TrueAudio, ARTA or any other shareware applications you guys might recommend. Thank you very much for your feedback.


So you want to get some use out of those drivers for your wife..

My suggestion would be keep it simple, but useful:

an "upward firing" radial configuration used for rear/side channels for your HT. Placed up against the wall, a small driver in this application can do wonders for HT immersion.

Basically you need only make a small "flat" (low depth) box to hang on the wall. It could even be as simple as sealed, OR it could be a Bass Reflex design. WinISD would handle either.

Enlist your wife's help in figuring out it's shape and exterior finish (..which could be a nice fabric she picks out).

This configuration eliminates many technical hurdles.. like baffle step loss, crossover design, additional drivers, etc..

You could always augment them with a plate-amp powered subwoofer for extending low freq. use.

I'd do this all with a nearly invisible wall connector so that you can remove them after you are finished watching your movie. (..bundle up the speaker and speaker wire and put it away once you are finished.)

(..of course you'll need an HT receiver to power them, and those can be pretty cheap.)
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Last edited by ScottG; 10th February 2011 at 10:20 PM.
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Old 10th February 2011, 11:23 PM   #8
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Originally Posted by chromenuts View Post

The only question I would have in this kind of application of these drivers, which seems to be line very much with the general advice of experimenting with simple designs first, is how would I go about trying to smooth out the response of these drivers above 3kHz?

I am very interested in getting a mic/preamp setup with some sort of laptop USB interface so that I can measure and learn about what I am accomplishing with some of the freeware like TrueAudio, ARTA or any other shareware applications you guys might recommend. Thank you very much for your feedback.
If you can measure it, you can tame the response for a 2-way for sure. I can help you with the x-over, as can others on the forum. Do you have other restrictions on the speaker you build? You could use these as mids in a 3-way for example. Can you drive a 4 ohm load? If you stick with a MTM, do you object to spending a bit more on a tweeter? Do you plan to hide the drivers with grill cloth? I have several ideas, but a lot depends on what you want. What about using a receiver with Audicy? Spelling??? Let the automatic EQ fix some of the ripples.

I'd use something more like this tweeter. https://www.madisound.com/store/prod...oducts_id=8354

What if you back mounted the woofers for a different look?

Last edited by kbgl; 10th February 2011 at 11:35 PM.
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Old 11th February 2011, 02:40 AM   #9
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OK...I know I ramble as I'm trying to express what is going through my head with these types of projects and often its not all clear what I want in the end. I'll try to clarify my goal.

I would like to use these Aura speakers somehow to create a HT system that will deliver a Dolby 5.1 surround signal.

So far, I have 10 of the same small NS35-255-4A extended range drivers. I also have 2 of the RPM plus 10" Aura subwoofers to use in the system.

I have acquired a Marantz SR7000 receiver to do the surround processing and provide amplification to the front, rear and center channels in this system. I believe this receiver provides 80 to 100 watts to an 8 ohm load. I am not sure if it is stable to 4 ohms.

I can utilize a Counterpoint SA12 amplifier I have for subwoofer duty. It will only play in stereo mode, but will provide 80 watts per channel into 8 ohms or 140 watts per channel into 4 ohms (the 10" subs are 4 ohm).

I was having problems sorting through the complexities of a speaker design that would utilize the small Aura drivers in conjunction with a tweeter (specifically the Dayton unit I noted in my first post).

In the end I felt ill equipped to make the decision as to what I needed to invest into the crossover and how it should be designed in order to walk away from this project with a warm fuzzy DIY feeling instead of disappointment.

I'm not limiting design proposals. The MTM just seemed popular for this purpose. I think a 3 way speaker is too big and complex for the proposed use and my abilities. The speakers will probably be covered to prevent little fingers from perforating the cones.

These drivers were very affordable. I would expect a similar or slightly higher investment in other drivers I might require to use with them. I also would expect to invest a proportionally similar amount of money into a passive crossover if I were to integrate a tweeter. How much is required to feel warm and fuzzy I suppose is the question.

I have noted some of my investigations with these Aura drivers in a vented box design using WinISD in my first post. However, I think it has already been established that I should probably be working with the simplest design possible, which is perfectly fine with me.

My last idea was to consider simplifying the speakers by eliminating the use of a tweeter. Subsequently, I asked if there was a method, whether it be through passive filtration or other means, to smooth out the problems in the frequency response of these small Aura drivers above say 3kHZ.

Scott...thank you for your response. I did a quick search into radial speakers and wasn't able to find a whole lot that illustrated the design in a way that made me feel like I would pull it off easily. I think it might just be another can of worms I shouldn't open at this point.

I really would like to somehow get the five channels I need for the HT system out of these drivers. I'm not expecting to be astounded by them, merely pleasantly surprised.

I do not yet have a way to measure my speakers...I am at the mercy of the factory data sheets and any shareware modeling software I can figure out.
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Old 11th February 2011, 03:14 AM   #10
Ron E is offline Ron E  United States
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Quote:
Originally Posted by chromenuts View Post
I would like to use these Aura speakers somehow to create a HT system that will deliver a Dolby 5.1 surround signal.

So far, I have 10 of the same small NS35-255-4A extended range drivers. I also have 2 of the RPM plus 10" Aura subwoofers to use in the system.
The tweeters look fine, have you bought them tweeters? If not, these might be another inexpensive choice:
https://www.madisound.com/store/prod...oducts_id=8264
Using the Auras vented is probably a waste of time, try bringing your sub xo up to ~120 and make sure it is fairly centered or use stereo subs as stands. Use a sealed box about 5-7 liters per woofer. Using them fullrange may be a disappointment as those peaks are right in the sibilance range.

Get a mic and Holmimpulse, build your boxes, measure them, then use Jeff Bagby's PCD software. For a mic you can get a calibrated one for ~$40 at PE, then you need a phantom power preamp like a Rolls MP13 or MAudio audio buddy for another $50 and some hookup cables.

If you don't want to buy a mic, get cozy with a local audio club and you might find some hands on help there if you sound serious.
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