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Old 20th January 2009, 05:37 PM   #1
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Default Low end support for single driver monitors

Having built a pair of single driver Fonken speakers from the plans on Planet10-hifi.com I am interested in augmenting them with support in the mid-bass to bass region. The Fonkens are the first pair of speakers that I've constructed, I've found that I really enjoy the woodworking and assembly end of DIY speakers. My overall goal with this project is to have a better understanding of how a speakers design affects it's performance. I've been reading articles and books about speaker design, visiting links found through forums, and playing around with various computer programs such as winISD, I think I've gotten to the point now where I've got a better idea of the many things I don't really know anything about. More then likely it's the tip of a really big iceburg.

So far I've figured out my "design goal" for the speakers: bass units that would be able to run from about 200hz down to around the high 30 or low 40 hertz range, providing tight, fast bass such that it will compliment the characteristics of the Fonkens, in a cabinet that will function as the stands for the Fonkens and mirror the front profile of the Fonken cabinets. Before I go any further I must make it clear that this design goal is most definitely based on the Fonkenwoof that Planet10 (Dave) and Chrisb have referred to a few times, especially in
this post in the full range forum. Rather then ask them for their plans, I'd like to learn more about the process myself, build something that will sound great of which I can be proud of because I've been more involved with it's design. To be honest, I also would like to do it this way because there's a "parachute" of a design from proven designers.

When I get more time I'll add some more specifics of what I'm thinking of in terms of cabinet size, design, drivers, and crossovers. Hopefully I won't wear out my welcome with questions.

Thanks,

Ben
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Old 20th January 2009, 06:52 PM   #2
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Default Cabinet design

Taking into account the Fonken's footprint and the fact that stands of 26" give the best imaging I've heard so far, I come up with a box of 2566.2 in^3, or 42.0l, as the biggest volume I could fit using the bass units as a stand. This accounts for the 45 degree chamfer of the baffle but ignores volume lost to the thickness of the material used for the cabinet, drivers, and bracing.

I've been using winISD pro to model boxes based on these dimensions. A box, wether vented or sealed, seems to be pretty straight forward to model for a single driver per cabinet. I'm also interested in modeling a cabinet with 2 drivers mounted in a push-push configuration. Is there a program that simulates this scenario? If not, can I infer that they'd react in a certain way when set up like this?

My train of thought is this: I figured out what I want to acheive with this project first (design goal). I know what physical parameters I have to stick with to make the cabinet work within my goal (fitting under the Fonkens as stands) so I know what volume cabinet I'm playing with. Using that volume, I'd start to figure out what driver's would work to give me the frequency response I want. Does that make sense?
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Old 3rd February 2009, 07:55 PM   #3
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Ben,

An interesting post. I am following not too far behind you in this process.

I am just finishing off a pair of Fonkens. I too took inspiration from planet10 and benefited from a lot of help and encouragement from Dave and Chris. In the end it was important to me that I participate in the design and I came up with my own Fonken design with a Vb of around 6L (which I have since extended to designs for 8L and 10L). The woodworking has been really enjoyable and although they are not yet 100% finished I am already looking forward to building more.

In my case I'm aiming for something that can be used for Stereo and HT and to this end I am designing the Fonkens to reach down to 80Hz at worse (rear surrounds, requires Vb just around 6L) and perhaps a little lower (front speakers, probably go with Vb of 8L minimum). Then I can add a subwoofer/woofer that takes it from there.

I too am thinking along the lines of both designing and building a sub which would act as a support for the Fonkens. I'm a bit concerned about physical box vibration when using the sub as a support so like you I am considering a two-driver solution to cancel out the box movements. I'll start with one, used to support the central HT Fonken and if I need go to with a pair then I'll build a 2nd and set them up as supports for the L and R.

I've just started my research on this topic and I think you are on a similar tack so I'll be interested to see what you decide on. Note that as I've designed my own Fonken, the physical dimensions of my supports (if they are to match my Fonkens) will be quite different from yours - most likely mine will have a smaller footprint (roughly 21cm x 22cm).
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Old 3rd February 2009, 08:51 PM   #4
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I think a subwoofer to augment a FR driver is the way to go. I've heard significant tuneful bass from FR speakers, but it always seemed to come across as somewhat slow. I listen to a bunch of electronic music. I've put together a fairly modest sub (compared to some), and it helps a great deal.

I used the 10" Foster driver NPT-11-083 from Jhidley
http://home.comcast.net/~jhidley/

Along with the Apex Sr. sub amp from Apex Jr.
http://www.apexjr.com/Apexsenior.htm

The driver looked like it had been sitting on its face for too long when I got it, but it performs fine. The amp is probably more powerful than I need. I think the XO freq on it only goes up to 160, it might be nice to have higher if you're going to integrate w/ a smaller driver. For my own use I'm very pleased with both items.

Setup is a sealed box that I computed up based on WinISD. I think it's about 4 cuft, minus bracing and internals. Construction was very simple with 3/4" oriented strandboard. I am always suprised how stiff and solid the box feels. I built it in a weekend. Caulk your seams, I was able to pop mine during testing.

It makes solid sound down to 30 hz. I could have gone deeper ported, but I haven't missed the depth and wanted good impulse response. They augment Fostex 167 metrinomes. While the mets actually got down about equally deep in my room, the sub has MUCH greater authority and impact, while also making things easier for the rest of the system. It took several days of fiddling to get the integration right. Phase knob was important, as was getting past the "LISTEN TO MY SUB MUAHAHAHA" volume phase. Now listening buddies report that it is integrated very well.

I'm very pleased with it. And it was, what, maybe $200 to implement? A bit less? Sometimes I see people in the subwoofer forum talking about "I want to make my first DIY Sub, my budget is $600 or so..." I don't know what to think. Maybe their requirements are much greater than mine? Or they (or I) don't know what they're talking about? Maybe I have put together a sub of uncommon value? Perhaps others desire a weapon of mass destruction, but this setup seems very capable and musical to me.

Now I think with the sub that I could make smaller cabs for the 167's. I'm considering the 167-fonken cab for next summer... Not exactly your own situation, but perhaps interesting info anyway.
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Old 3rd February 2009, 10:06 PM   #5
JVA is offline JVA  Canada
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Look up creative sound solution's web site. On their SDX-7 7 inch woofer it has various box designs for this woofer, both vented and acoustic suspension. I myself build two of these woofers each in one cubic foot parts express pre-built boxes. I did use a seperate subwoofer amps for each side.

I found them very fast, tuneful, and a perfect match for my small line array. I would reccomend that the amps used would have a complete cross over and room equalization. This way you can play with the woofers to blend in with your fonkens. It's a little more expensive than a simple subwoofer, but you get a lot better result.

By the way, I forgot to mention that the subs were acoustic suspension.

-JVA
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Old 4th February 2009, 02:03 AM   #6
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JVA,

I like the smaller size (and cost) of the SDX7 vs the SDX10 but I wondered if it had enough 'gumption' to make a sub. It seems that it would be happier around 150Hz than below 80Hz where I want it. As I know virtually nil about such things can you give a bit more detail on your experience with the SDX7 and your opinion on whether it can do double duty between music and light-home-HT use ?

How does an amp have room equalization ?
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Old 4th February 2009, 09:33 PM   #7
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Planet 10 can tell you more about the sdx7. He uses 2 in a TL under each of his fonkens (4 drivers tot). He said about how low they go, but I don't recall what the number was.

Here, he throws out some figures
http://www.diyaudio.com/forums/showt...t=#post1665607

My (perhaps flawed) understanding is that the driver is still fairly comfortable below 80 hz. Maybe less so below 40...
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Old 5th February 2009, 12:06 AM   #8
JVA is offline JVA  Canada
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Gareth,

These speakers have plenty of "gumption" for a medium sized room.
I'm very satisfied how the woofers blended in with the Line array. The sub amp does not have room equalization but does have an equalizer in it and has 10 various controls to boost or bring down the various frequencies from 20HZ to 150HZ. The amplifier (in case you are interested) are Reckhorn 400. Check on their website for information. I used 2, one for each side for stereo effect and I cross over at approx. 100HZ. CSS did sell them and they still may. As mentioned before, Planet 10 has a fair amount of info on these woofer drivers.

Joe
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Old 5th February 2009, 12:09 AM   #9
JVA is offline JVA  Canada
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Here is a picture of the woofer box ready for the woofers.

Joe
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Old 5th February 2009, 12:12 AM   #10
JVA is offline JVA  Canada
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Here is a photo of my line array on top of the woofer box. They blended in perfectly. This may give you an idea if you built a box below your speakers.

Joe
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