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1st speaker project - was: New Idea For a Small Business, at age 15! (Moved) (1 Viewer)

Phaseshift

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BobbyG2- While I will not give you specific info on how to build your system, I can give you a few bits of inside info.

The first money you spend should be on Vance’s book – “The Loudspeaker Cookbook” Get it, read it, learn it, live it. Vance knows system design and what you are getting into is mainly system design and actually is perfect as you will have to use off the shelf transducers and filter components. Having read and understanding the basics of that book will let you make your own choices, calculations and decisions and more importantly, give you the understanding necessary to let you learn form your mistakes.

I saw your comment about the test gear and software prices- Get ready for sticker shock, because good test gear is not cheap. Between the electrical and audio labs in my company, I have at least $100K worth of test / lab gear and software and I feel that we need a lot more; some of it used very little, but critical as the results have to be spot on. If you are to purchase your own test software, I recommend that you look for something basic or that you can get a student deal on. As much as I dislike / distrust LMS, I have to say that it is a descent program to learn and if you get it with the LEAP bundle, you can save some $$$ on the package. Having LEAP would be very helpful for you in figuring system and filter specifics. Heck, there are a lot of companies out there that use little more than the LMS – LEAP combo for their engineering wing and do OK with it.

If you do get LMS- when you see your first measurement at 300 points, no smoothing- do not freak out; it is the reality and until you see it first hand, you could never imagine how bad it is. If you want to feel better about it, know that 1/6 octave smoothing is what a lot of people use for their engineering work (looks a lot better) and what is shown on the packaging or literature is often 1/3 octave smoothed or more in some cases.

Do not get the “bigger is better” complex. Yes, sometimes it does work, but in system design; particularly related to low frequency systems, you have to be careful that you do not end up with some ridiculous cabinet to get your el-cheapo 15” PA woofer to act like a sub.

Do your own research and compare it to your better brands out there- Take your pick, there are a ton of brands that are good and would be good targets to emulate.

Do not get too excited about bass only- If you have nothing but bass, you have nothing. On the flip side, this is a good place to start because it is easy in comparison to the upper end of the spectrum. Your transducer is acting as a piston so you are free from a lot of other issues like dealing with modal response issues, alignment, mid to tweeter level matching, complicated filter design and development etc… Basically with a subwoofer system, you are dealing with a few simple calculations and some basic common sense fundamentals- No sharp edges in the vents, keep your vent velocity under m0.8 and make sure that you are not loading a vent into a barrier in actual use (i.e.- a 5” diameter vent pointed at the floor with ½” clearance- that is bad). If you go with a sealed system, all the vent issues go away and it is pretty much down to driver selection, getting your calculations right on the Vb / Fb balance and building a good, solid cabinet.

The one thing I will say about building a home sub is look for a driver that is closer to a car woofer than a PA woofer. From reading through this thread, I see you are looking at some off the shelf drivers and I am afraid that a lot of the stuff you are looking at is closer to a PA application than what you may want. For the woofers, look at Xmax, Qts, Vas Fs and Bl. For a 12” sub, you should be looking for a 12 to 18mm Xmax (linear) as a minimum. Qts is going to be specific to your system design, but will likely be in the 3.6 to 4.0 range for the typical vented cabinet. For Bl, the higher the number the better, but you should be suspicious of a cheap woofer advertising a Bl of 21.5 without it having a very serious motor on it. If it seems to good to be true, it is. For Vas, you do not want to see a very high number- under 50 liters is good, but up to 75 is OK depending on the system alignment etc… Fs- Resonance is one of the keys. Making a system solidly hit 25Hz with a driver reaching resonance at 36 Hz is tough. You can do it, but other significant tradeoffs have to be made- usually the only way to do it is through a monster box volume. You may also look into the compliance (Cms) and keep in mind that you do not usually want a very low compliance Cms driver for a home sub unless you have some big amps to drive the system. Big as real, true big – as in Crown, EV or Peavy pro amps that will really do the numbers and in my book- big = 1KW + per driver.

Hope this helps. Best of luck.
 

bobbyg2

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Alright, thanks for the info Phil. I'll order that book from Parts Express on Friday, and probably wont get that testing software for a little while... I'm not making "audiophile" subwoofers at this time, just a test subwoofer for my room which doesn't need to sound 100% at this time.

Would you consider a Dayton DVC subwoofer as close to PA? 'Cuz, I can't afford to go buy a $300+ driver on the amount of money I'm making right now... Eh, later on when I get a better job, will probably be when I get more into this.

I don't like the idea of getting something close to a car subwoofer... I hate the sound of the MTX, and Audiobahn subs. They are made for pure volume, and crap quality... I know I said I'm not looking for 100% quality, but those are almost unacceptable...

Again, thanks for the info Phil! :)
 

Phaseshift

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Post a link of the driver you are currently considering.

You mentioned not liking the sound of an MTX sub. Ask yourself, are you listening to the driver or the system? If the system tune is incorrect or inappropriate for a large environment, yes, it is going to sound crappy. However, do not be to quick to blame the driver alone.

Also keep in mind that the subwoofer is a piston- no modal response going on unless your crossover point is way up there. The loudspeaker cookbook will teach you how to know when the cone will go into modal response- find that and post it here.
 

Phaseshift

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I suppose that will work, but the box is going to be big. As in very big. Look at the Vas on that driver- 280 liter is a deal breaker in my book; I would spend some time looking for a better driver and build a reasonable sized, good sounding sub with some power handling.

I attached a screen grab from an old project which would probably suit you very well. It is a 12" driver, high power, 4 layer coil, nomex damper, strong motor, high Xmax / Xmech and plenty of power handling. Mmd is fairly typical of a 12" cone with a large (heavy) VC.

The model shown is in a 1.8 cubic foot cabinet and has fair response. This is not what we ended up with for the product that hit the shelf, but it would have a bit more of a boomy / punchy signature and I recall that this was a very strong performer when prototyped with a 400 watt amplifier. Not necessarily my preference, but I do not build them for myself.

The main thing to look at are the driver parameters on the right- these are in the ballpark you will want to look for in a 12" driver. I know you were looking at a 15, but if you put that 15" in a small cabinet, it will not perform anything like this or your typical home theater sub.

If you are dead set on that 15, I suppose you could do a pair of them in an isobaric configuration and get your cabinet volume down in the 3 to 3.5 cubic foot range with good performance. It may be worth doing the math and seeing where you end up. Do a web search for isobaric loading and also for a subwoofer cabinet calculator or something like that- there are a ton out there that work well enough for the piston mode stuff. If you only do a single driver, you are probably looking at 5 to 6 cubic foot for the cabinet. Play with the figures and see for yourself.
 

Robert_J

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It sounds like you are in the audio industry in some form or fashion. Care to give us any details? Most insiders like Ron and Tom from SVS, Mark from AV123, Chad from Ascendant Audio, Deon from Klipsch/TC Sounds/???? and Dan from Adire all make it known where they work. Also, this is DIY and not retail. We are not constrained by shipping so our enclosures tend to be larger and more efficient. Therefore Hoffman's Iron Law works in our favor.

-Robert
 

bobbyg2

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I really don't care what the size of the enclosure is, well, hight-wise. I could make a 2'x2'x4' (16cf) enclosure if needed.
 

Phaseshift

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Robert-
You are entitled to your opinion of that driver as am I. For me, my comment about the driver stands as is, but I will explain a bit further.

From what I see after reviewing the listed specs, that is a basic driver and yes, you can do a lot better. I did not say it would not work, but I did say it would require a large cabinet to get good performance. Your comment indicating a 4Cf cabinet sealed is in my opinion a pretty big cabinet. If shipping, WAF, power handling and other things are not a factor, then by all means, do a huge cabinet and enjoy the SPL numbers you can get until the thing runs out of steam or bottoms out (I bet that driver will hard bottom – as in VC former to back plate – CLANK!) Yes, it may have a power handling of 350 watts, but that is very likely a thermal number and is validated with EIA 426-a or B noise which will not drive it to Xmax therefore no bottoming, but a lot of heat. The Bl is low and the mass is high and you can see that the Vas is way out there. There are way better drivers out there and to me, that price looks rather expensive for a basic driver – nothing special, no shielding etc… Oh, it does have a rubber magnet boot; forgot about that “performance enhancement”. Sort of like a racing gas cap sticker. ;)

Using RevSpeaD and FineBOX, I ran the driver and find that several of the published parameters have to be kludged beyond a decimal place or two in order to work- maybe that comes out of the old Dumax era, but still, it is what they publish.

Also note that I did indicate that the driver in the screen grab was not my preference - It is however a pretty close relative to what is in the majority of the consumer level and similar cabinet subs out there. If I recall correctly, we changed the thread count in the damper to increase the compliance a bit; I belive the Fs ending up at about 27 or maybe 29 on a new driver. Also note that this data was taken using MLSSA on a brand new driver- swept at 5 to 7 volts to identify any potential RVC issues and then onto testing. Typical situation is that the Fs will shift down between 5% and 15% from new to broken in- depending largely on the damper construction (thread count + weight, phenol impregnation, roll count, diameter etc...) 5% being topical of a lighter weight, high compliance driver such as a mid, and 12% to 15% for a woofer such as the one I was dealing with at that time. That said, you are looking at an end Fs in the 28 ballpark for a working production unit if we had we used the mechanical model used in that illustration.

Xmax at 14mm linear - that is a pretty healthy Xmax if the driver will do it linear. I believe the driver ended up with a thinner front plate and the Xmax ended up at 16.5mm (winding edge to front plate)

I posted a image of one of many, many files I have on hand showing the development steps of a subwoofer system and indicated that it was not my preference, but that is does represent typical values that you may see. I suppose my error here is not listing a hell of a disclaimer about the numbers not being identical to that of the perfect sub.

Yes, I know Eminence, and yes, I am familiar with the stuff Anthony did.

And, yes, I am in the business and have been for many years. I run a service company that does design work for the big guys and some little guys as well. I have been involved with the design and manufacturing of hundreds of products ranging from cheap-o car and home speakers to super high end THX certified speakers and full range studio monitors.
 

bobbyg2

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Got any better ideas for a driver? I was looking into upgrading to a 15" TC Sounds driver later on in the future (about 1 year, no rush) and wanted to have an enclosure that can accumilate the TC Sounds driver as well. And, as I said, size isn't an issue at all. 2' deep x 2' wide is the limit though. The hight limit isn't definite, but it'd be nice if it was shorter than my ceiling! ;)
 

Phaseshift

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Bobby- I suggest reading the book and learning all that you can. In the mean time, I suggest writing a spec sheet for your system and use it as a roadmap for your project and to identify all the stuff you need to learn.

I am a little reluctant to post specifics or my opinions if I am going to have to come back and defend or clarify a lot of details as above. It is very frustrating.
 

Robert_J

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You come in here and knock the PE driver based on specs alone. I've been a member here and numerous other forums where this driver, along with the Tempest Classic have been used successfully in dozens of subs. Now, I haven't used the 15" version of this sub but I do have the 12" PE DVC in my home theater right now. I've also used the Adire version (the Shiva) as well. Both are great subs for the money.

Please post specifics. I really don't want to be responsible for running off a member of ALMA. We're all here to learn. But if we have differening opinions, that's OK too.

Bobby,
I stand by my recommendation for this driver if you want to stay at a small budget.

-Robert
 

Phaseshift

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OK, It is one of the best 15" DVC drivers for DIY home theater projects for the money. Of all the drivers I have ever seen, it is definitely one of them.

My basis for "knocking it" is not the specs alone. Looking at the published parameters, I have a basic feel for the overall performance level of the driver without running a ton of simulations. If I go into specifics, someone is going to nit-pick the hell out of whatever is published, so why bother?

Enjoy the discussion and hope it all works out for Bobby.
 

bobbyg2

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I hope it does to... But, with my luck, I'd end up wiring it up wrong and melting something. Like I did with my new computer.
 

Phaseshift

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Bobby- My suggestion is to get the book in your hands and go through it a few times. Doing so will let you learn to make a few of the decisions on your own and when something happens (good or bad) you will have a better feel for why that happened.

I did not suggest using that driver mainly because I feel the Vas is very high which is typically going to result in a very large cabinet. I am accustomed to having to make things work as well as that in a smaller cabinet and driver selection is critical.

It will probably work for you if you do the system design correctly. I would not likely use it for myself, but I have a different level of accessibility than most people do to high end drivers for free or in trade for lunch. It is my personal preference and not a slam on Dayton, Eminence or anyone. Just my personal preference.

Most important thing here is to enjoy yourself and learn what you can. I can not stress enough how important it is to educate yourself with the cookbook and other works. Seek (on the internet search engines) and ye shall find.... ;)
 

Phaseshift

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I am not sure what is available to the DIY market. Some stuff may be, but in general, I am doing a transducer design to match the system requirements. A lot of time, this is taking a standard or semi-standard driver or platform that some vendor offers and doing some tweaks to it to change parameters or response characteristics. For instance, you may take a motor that you like which fits a frame with the right geometry and come up with a new cone, surround, damper and DC (Dust Cap) that you like in order to meet the parameters you are hunting for. Another case is that you use existing soft parts and fit them to a new frame geometry where you have to meet CE (the European S&R guys) or other S&R (Safety & Regulatory) requirements (CE is a little nutty about speaker baskets these days- especially when the speaker is used in a system with a built in amplifier in it). In general, I would say that most of the stuff I work on is not something you will ever run across as a DIY piece.

I am not familiar with any of the brands Robert mentioned. I suspect that most are bands that are buying platform transducers from vendors like Emminence, Credence, Misco or others (a short list of companies that I know for 100% sure are making drivers). I could be mistaken about that- maybe those guys that Robert mentioned are making their own transducers, but I have not heard of them.

http://www.tymphany.com/ is a large OEM producer wiht facilities worldwide. Their website that has links to a couple of their brands that may have some stuff available. Scan Speak for sure; Peerless maybe but I am not sure. Both cases are going to be more focused on mids and tweeters- caution, some may be accompanied with sticker shock. I doubt if the LAT's are available at this time unless you are an OEM. If it were, I would say it is one of the better solutions for DIY if you have some room and want something that packs a hell of a punch. Prototypes I have done with that platform are impressive in all sizes. Cool stuff. The currently published specs show higher resonance points than I have seen in practice, but their primary design to start with was the car market and I personally feel that the resonance is too high on the 500, but that is only one engineer talking- they have plenty of smart guys and have done quite well with the product. I think they sold about a jillion of them to Alpine. Note that Tymphany purchased a company called DST (Danish Sound Technology) which was formed when Vifa, Peerless and Scan-Speak merged to be run as a single company. peerless here is Peerless Europe - NOT Peerless India.

For normal woofers, I suppose you guys have that covered with the ones Robert mentioned above.

Note- I did come back and edit for clarity in a few places.
 

Robert_J

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I've seen the Tymphany sub. Interesting technology but I want my sub to move air. That's why I'm looking into getting some soft parts and 18" frames from Fi Car Audio and mounting them to four neo motors that I have.

Since you mentioned Peerless India. What is your opinion of their quality? The guy that runs the DIY Mobile Audio forum contracted with them for a run of subs. They seemed to sell well for him and have some very good reviews from the people who purchased them. Also, based on the looks of the SDX15 sub at Creative Sound who do you think built it? It was sourced from China. Since it is using XBL^2 technology from Adire, it probably has a good relationship with other US companies.

Thanks for hanging around Phil.

Sorry about the thread hijack Bobby.

-Robert
 

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