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sjrand96

Member
2016-04-25 5:29 pm
Hello DIY Audio Community,

I'm a rising Junior at college studying Physics and Engineering. I'm a newbie to the audio scene, but after hearing a friend's wonderful speakers in his dorm room I was hooked. After ending many a night in his room listening to all types of music (and irritating neighbors), I resolved to obtain my own set of quality speakers. After a bit of research and thought, I decided to DIY my own speakers, and to construct them at the machine shop at school. This was my first set of speakers I'd ever made, so I went for a simpler 2 way design. My criteria were as follows:

  • Deep Bass
  • Non-Fatiguing Treble
  • "Warm" overall tone
  • Louder than my neighbor's speakers (JK, sorta)

After doing some research, primarily on DIY Audio & Video, I learned a ton about enclosure design, construction, and modeling using their calculators. I decided to use the Dayton RS225-8 Woofer, and well reviewed Dayton Audio DC28F-8.

I read a decent amount about crossovers, but didn't feel up to the task of designing a proper crossover in addition to the enclosure, especially as I had no idea of what to expect, so i purchased a premade 2kHz crossover, also from Dayton.

The calculator at diyaudioandvideo.com stated that I should probably use a sealed enclosure, but could choose to use a ported one if I wanted to. Hearing that the ported enclosure produced a warmer tone and greater bass extension, I chose to go for that route. The enclosure calculator gave me a ported box volume of 1.65 ft^3, and an f3 of 30.87 hz with a 3" diameter, 10.31" long port. I designed an enclosure with this volume in CAD, and then constructed it from 3/4" MDF, and wrapped the whole thing in Vinyl. (Photos coming soon).

I only constructed one speaker to start, in order to learn about the process and determine if my experimental and relatively blind attempt was worth the additional investment of creating another speaker. I plugged in the completed speaker and was very excited by the sound quality, especially in the bass frequencies, I'd say it definitely outperformed my laptop speakers :D. I was obviously excited because I had made it myself, and many speaker demonstrations were put on for friends, much to the chagrin of those living adjacent to me. The sound is slightly muddier than my friend's system, and definitely lacking somewhat in the mid-range. Both bass and treble are fairly clear and good, but the mids feel a bit recessed.

Regardless, I've decided it's a good enough design to make a 2nd one, and the lack of stereo was really bugging me, so I'm currently in the process of constructing a 2nd speaker (again, pics to follow). I'm obviously making it an exact match, but I was thinking about things that I should have done better in the design process and places to still improve the current design.

I would love some constructive feedback on this pairing of drivers, enclosure design, and crossover, and I also have a few questions for the community.

  1. I purchased some polyfil material, but have not yet installed it into either speaker, is this worthwhile, and if so how much should be used?
  2. Is this enclosure too large? Parts-Express lists the bassbox6 suggested vented enclosure as 1.26 ft^3, what gives?
  3. Is it worth the effort to design my own crossover for this set of speakers, or is the current one adequate?
  4. Am i more likely to damage the speakers from over excursion or electrical power? I don't fully know when I should start to be worried about the power being too great for the drivers.
  5. Any additional thoughts/concerns/ideas?

Thanks so much for your time and support!

--Spencer
 

eriksquires

Member
2013-05-10 4:11 pm
1 - Polyfill is greatly misundrstood. It will increase the effective size of the cabinet, by about 10-15%. I find it usually reduces boominess, but if you want to be most accurate, you should measure as you stuff. :)

2 - Get WinISD to simulate different cabinet sizes and port options. Free.

3 - Crossover design is a deep art. To do it correctly requires measurement and simulation tools. I like OmniMic, DATS and XSim, of which only XSim is free. Room EQ Wizard is free however, and together with a Dayton imm6 microphone you can really do a lot.

4 - Depends. WinISD will also simulate this for you.

Lastly, you should search for kits with your drivers, someone probably has a better tuned crossover you can use. Unfortunately part of the equation is the baffle size and driver locations.
 
Your woofer of choice is very nice, but not appropriate for a 2 kHz crossover. Response is already falling off at 2 kHz and starts to rise again at 3K, peaking 6 dB @ 5.5 kHz. This might be audible with an "off the shelf" crossover. Impedance at 2 kHz is around 10 ohms, and rising at 6 dB/octave. This might not play well with your crossover, making these peaks even more audible.

I've been looking for an 8" woofer for a 2 kHz crossover in a 2 way and this is what I'm thinking about. Dayton Audio RS225P-8 8" Reference Paper Woofer 8 Ohm which is very similar to your choice. It has a similar impedance regime but if you look at the frequency response it's way smoother to 2 kHz, with a 10 dB peak at around 3.5 kHz that could maybe be tamed with a notch filter on the woofer.
 
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sjrand96

Member
2016-04-25 5:29 pm
1 - Polyfill is greatly misundrstood. It will increase the effective size of the cabinet, by about 10-15%. I find it usually reduces boominess, but if you want to be most accurate, you should measure as you stuff. :)

2 - Get WinISD to simulate different cabinet sizes and port options. Free.

3 - Crossover design is a deep art. To do it correctly requires measurement and simulation tools. I like OmniMic, DATS and XSim, of which only XSim is free. Room EQ Wizard is free however, and together with a Dayton imm6 microphone you can really do a lot.

4 - Depends. WinISD will also simulate this for you.

Lastly, you should search for kits with your drivers, someone probably has a better tuned crossover you can use. Unfortunately part of the equation is the baffle size and driver locations.

Thanks Erik, that was helpful. I downloaded WinISD and modeled up the woofer, which showed that my enclosure was indeed the correct volume for the driver as calculated by the other calculator, the volume was nearly exactly the same suggestion. With 50W of input power, excursion shouldn't be an issue above 26 Hz, very good information. I'm reading up now on crossover design, and will likely purchase the aforementioned microphone and attempt to utilize Room EQ Wizard. Thanks again for you helpful suggestions!

Hi,

You still have loads to learn.
Your premade x/o is all wrong, very wrong.

Take a look at these two sites :
https://sites.google.com/site/undefinition/diy
Zaph|Audio

rgds, sreten.

That was the whole reason I joined this forum, to learn. I'd appreciate some constructive advice and a point in the right direction rather than "wrong, very wrong." I am ready to put in the time to learn about crossovers and will work on following some of the information supplied above. The links you provided appear to be just pre-made designs, which I'm sure are excellent and well thought out, but I'm interested in learning to really understand how to design a system, and want to go beyond simply constructing things that others have designed.

Your woofer of choice is very nice, but not appropriate for a 2 kHz crossover. Response is already falling off at 2 kHz and starts to rise again at 3K, peaking 6 dB @ 5.5 kHz. This might be audible with an "off the shelf" crossover. Impedance at 2 kHz is around 10 ohms, and rising at 6 dB/octave. This might not play well with your crossover, making these peaks even more audible.

I've been looking for an 8" woofer for a 2 kHz crossover in a 2 way and this is what I'm thinking about. Dayton Audio RS225P-8 8" Reference Paper Woofer 8 Ohm which is very similar to your choice. It has a similar impedance regime but if you look at the frequency response it's way smoother to 2 kHz, with a 10 dB peak at around 3.5 kHz that could maybe be tamed with a notch filter on the woofer.

Hmm, thanks for the information. I guess I don't really have a finely tuned eye yet for determining where the crossover point really should be, I'm going to do a bit more research and find some other designs that use this driver, but where would you likely cross this system if you were using these components? I recognize that your driver is likely better for the application, but having already purchased these components and being somewhat budget limited I'd like to try to make it work with what I have.

I don't think it's wrong, but it will certainly need adjustment. I would take that for granted if I purchased a product like this, but I know that not everybody does.

For the most part I'd rather buy a blank board or make a board, but that's not everybody's cup of tea.

Thanks for the more positive and constructive response, I appreciate it. I'd love some suggestions for adjustment to better suit this application! I am now in a better position to begin investigating proper crossover design, and would be able to construct a board without an issue provided I was able to come up with a suitable design. Please advise on crossover points and I'll see what I can do with the various calculators and software available. Thanks!
 

giralfino

Member
2009-02-28 9:20 pm
That was the whole reason I joined this forum, to learn. I'd appreciate some constructive advice and a point in the right direction rather than "wrong, very wrong." I am ready to put in the time to learn about crossovers and will work on following some of the information supplied above. The links you provided appear to be just pre-made designs, which I'm sure are excellent and well thought out, but I'm interested in learning to really understand how to design a system, and want to go beyond simply constructing things that others have designed.
The links provided, especially the Zaph pages, contain well designed speakers, including reasons for the choice of the crossover elements. Once you have some idea of the basics of a crossover and speaker response (baffle step, diffraction, slopes, ...), a design that contains info about transfer function, polar response, etc, is good for learning how to model a crossover.

If you are really serious in learning about speakers, your best bet is to buy "Loudspeaker Design Cookbook" by V. Dickason and "Testing Loudspeaker" by J. D'Appolito. I find them a good source of info, although not always in a linear form.

You can also design a speaker without measurement, even if you own measurement capabilities, this is important because you can design on paper before buying drivers and crossover components. I find this paper good in describing the process: http://audio.claub.net/software/DaveDalFarra/Simple%20Loudspeaker%20Design%20ver2.pdf
Here you can find the (free) software needed: software

For box design (vented, sealed), I prefer Unibox, also found in the above link.

About the drivers chosen, a 2KHz crossover point is doable. I find that usually a LR4 crossover is attainable with a 2nd order electrical on the woofer and a 3rd order on the tweeter. Maybe here you'll need a broad notch for the woofer breakup.

Ralf

I hope you braced the speaker. Bracing is crucial in everything above 5L.
 
This sort of speaker is common enough:
TRYM
473078d1426996023-seas-trim-w22ex001-wg-seas-trym-schematic.png


The metal Dayton Audio RS225-8 8" Reference Woofer just needs shallower notch at 6kHz IMO.

So you should be somewhere like this below. Low crossover, but there it is.
 

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The links you provided appear to be just pre-made designs, which I'm sure
are excellent and well thought out, but I'm interested in learning to really understand how to design a system, and want to go beyond simply
constructing things that others have designed.

Hi,

There is nothing premade about the designs and Zaphs site in
particular contains all the information to understand the designs.
FWIW you'll be hard pushed to find a better designer, learn.

Undefinitions site less so, but some of us can join the dots ....