"Mynamid" - newb 3-way design - diyAudio
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Multi-Way Conventional loudspeakers with crossovers

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Old 21st December 2007, 02:21 AM   #1
ascottk is offline ascottk  United States
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Default "Mynamid" - newb 3-way design

For some odd reason I decided to design my own speakers. I have some experience with wordworking like production in college theater, but nothing as involved as this (I'm not am expert at all!). I have a lot of experience working with audio so these speakers need to be critical.

I'm a grad student with a focus on music composition. Before we get our masters degree we have to have a semi-pro CD prepared. I do a lot of audio engineering so I'm pretty much a DIYer.

Here are the sketches & dimensions, and a cardboard mock-up, of what I call the "Mynamid":
http://picasaweb.google.com/ascottk/...dSpeakerDesign

Inspired by other pyramidal designs & some time-aligned designs.

If you care to comment about the enclosure, please do so, but I'm past the point of no return to do any major modifications to it Maybe I'll be flexible about the drivers since I haven't cut the holes yet. I was thinking about these drivers & components:

Vifa D26NC55
Click the image to open in full size.
http://www.madisound.com/catalog/pro...oducts_id=1078
Good reviews about this one at ZaphAudio http://www.zaphaudio.com/tweetermishmash/

Dayton RS52AN-8 2" Dome Midrange
http://www.partsexpress.com/pe/showd...number=285-020
Click the image to open in full size.

Dayton XO3W-500/4K 3-Way Crossover 500/4,000 Hz (I haven't decided yet)
Click the image to open in full size.
http://www.partsexpress.com/pe/showd...number=260-152

The enclosure will be about 21 liters I guess & I may be wrong since I'm new to this.

Anyway, I need help choosing components! Once again, here's the link to the "Mynamid" design:
http://picasaweb.google.com/ascottk/...dSpeakerDesign
Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.Click the image to open in full size.
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Old 21st December 2007, 06:01 AM   #2
idaho is offline idaho  United States
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Oh man! One of the biggest challenge I can see in what you are trying to do is in the crossovers. I am relatively new to this but I can tell you that premade XO's will not work optimally. Sure you will get sound but it will not be good even with expensive drivers. I have proven this by the hard way-making the same mistake that you are about to make if you don't change course. Build a proven design- is the recommendation at least untill you learn more about speaker building then you can tackle or reconsider building a 3-way.
Pick a design in these sites. Read and learn too!

zaphaudio.com
rjbaudio.com
partsexpress.com
http://www.geocities.com/cc00541/index.html

Theres more but people here can point you to them.
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Old 22nd December 2007, 04:55 PM   #3
ascottk is offline ascottk  United States
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Quote:
Originally posted by idaho
Oh man! One of the biggest challenge I can see in what you are trying to do is in the crossovers.

zaphaudio.com
rjbaudio.com
partsexpress.com
http://www.geocities.com/cc00541/index.html

Theres more but people here can point you to them.
You're right and thanks for the links. I might stick with my existing drivers:
Yamaha NS-A637
Click the image to open in full size.
http://www.yamaha.com/yec/products/p...&CTID=50029000
  • Three-Way Acoustic Suspension, Magnetically Shielded Bookshelf
  • Woofer = 8 in. Hi-polymer Coated Cone
  • Midrange = 4 in. Cone
  • Tweeter = 3/4 in. Dome, Ferro-fluid cooled
  • Input Power Nominal = 70W, Music Input = 140W
  • Frequency Range 90 to 20,000 Hz +/-3 dB

I don't know how accurate the specs are for the original replacements:
Yamaha NS-5 NS5 NS-A636 NSA636 NS-A637 NSA637 Replacement Speaker / Speakers drivers for sale. Used Vintage Yamaha drivers woofer / woofers, mids midrange / midranges tweeter tweeters crossover cross over crossovers overs, cabinets & grills for Yamah

The mid-bass (above 300 Hz?) upwards translate well with my mixes and masters but I always have to guess how the lower bass is doing even with a sub. I'm definitely not crazy about the mylar dome tweeter on these. I don't like the enclosure either.
_____________

When I have some money I'll buy some better drivers (need to find a midrange with a 3 3/4" cutout), and either have someone build new xovers or design my own with some help with this:
http://www.lalena.com/Audio/Calculator/APCXOver/

& there's someone in Oregon who builds custom xovers:
http://www.chokes.com/custom_crossovers.html
_____________

Anyone have suggestions for drivers aside from my own? Here's the requirements:[list][*]tweeter: 2" cutout (3 - 3 3/4" diameter faceplate), 8 ohms, sensitivity around 90 dB, fairly flat response to or above 20 kHz,[*]midrange: 3 - 3 3/4"" cutout (around 5" diameter faceplate), 8 ohms, sensitivity around 90 dB, accurate, works well with above tweeter and woofer[*]woofer: I have a few woofers I can probably use that need testing. 8" woofers. 8 ohms. accurate for a 21 liter enclosure.
_____________
Since I can't edit my posts, here's the front view of my enclosure (cardboard mock-up and the woodworking is nearly done!):
Click the image to open in full size.
I designed it this way because most time-aligned speakers are pointed upwards or stepped. I need the tweeter to be pointing at listening position so it's not angled.

I'll probably move the midrange closer to the tweeter.
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Old 23rd December 2007, 01:30 PM   #4
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You have a nice midrange and tweeter picked out there. Both really good in the distortion area. I have read some good reviews of both. For the woofer, you should consider the Usher 8" 8955A. It has the low-distortion motor found in the 7" woofer that is reviewed on Zaph's website.

http://www.partsexpress.com/pe/showd...number=296-618


Don't forget you have to include some level of baffle step correction, which means you may be hard press to get to 90 dB/SPL.

Another option would be two Dayton RS 8" 4-ohm, it will get you 8-ohm total if you wire in series and more surface area for that deep bass.

http://www.partsexpress.com/pe/pshow...number=295-376
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Old 24th December 2007, 01:16 AM   #5
ascottk is offline ascottk  United States
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Quote:
Originally posted by 69stingray
You have a nice midrange and tweeter picked out there. Both really good in the distortion area. I have read some good reviews of both. For the woofer, you should consider the Usher 8" 8955A. It has the low-distortion motor found in the 7" woofer that is reviewed on Zaph's website.

http://www.partsexpress.com/pe/showd...number=296-618


Don't forget you have to include some level of baffle step correction, which means you may be hard press to get to 90 dB/SPL.

Another option would be two Dayton RS 8" 4-ohm, it will get you 8-ohm total if you wire in series and more surface area for that deep bass.

http://www.partsexpress.com/pe/pshow...number=295-376
Thanks! Okay, suppose I bought a Dayton RS225S-8 (8 ohm) with a 88 dB sensitivity. I need to bring down the tweeter & midrange 3 dB with l-pad circuits?

Without baffle step correction (need more research on that), here's what I came up with (1st order, 500/4000 Hz).
Attached Images
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Old 24th December 2007, 01:48 AM   #6
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ASCOTTK-

I would recommend picking some drivers and first doing a design using the free FRC tools. This is a good way to do a design "on paper".

Here is a quick outline:

1. Trace the mfg. freq. curves and impedance curves.
2. Use Unibox to determine the low-freq. output.
3. Use BSC to determine the baffle loss response. (By the way, you loss -6 dB when the freq. wavelength is wider then your baffle - in simple terms).
4. Use Freq. Response Combiner to combine all of the freq's into one.
5. Extract the proper phase.
6. Then use the crossover designer to design a crossover. (You will need a more complicated X-Over the 1st order I think).

When you get to item #6, people can help and point you in the correct direction. And give some guideness on the necessary steps. I am no crossover pro by any means. When you get to #6, post you results (w/o crossover) and then we can stay adding X-Over parts to see what is needed.

Here is a better step-by-step procedure for using the tools:

http://www.rjbaudio.com/Audiofiles/FRDtools.html
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Old 27th December 2007, 05:39 PM   #7
ascottk is offline ascottk  United States
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Thanks for the link!

Unfortunately the FRC spreadsheet didn't work too well for me so I used the method here:
http://www.angelfire.com/electronic/...rworkshop.html

Here's the frequency response I have in Speaker Workshop so far:
Click the image to open in full size.

& here's the XOver:
Click the image to open in full size.

I chose the RS225S-8 for the woofer. There's no ported box model combined with the woofer's fequencies.

Is the crossover too complicated?
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Old 29th December 2007, 03:22 AM   #8
ascottk is offline ascottk  United States
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Okay, the impedance trace was off & here are the further adjustments:

Modeled frequency in Speaker Workshop with the added ported box:
Click the image to open in full size.

Impedance:
Click the image to open in full size.

Revised crossover:
Click the image to open in full size.

Any further help would be appreciated
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Old 29th December 2007, 05:49 PM   #9
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ascottk,

You have a nice little cabinet design. But I have to ask if these are going to used in the near field as near field monitors. If so, may I make a few suggestions. With a few good design ideas you can make these into a pretty decent pair of mixing monitors.

First, the midrange is the most important driver in this so don't use a dome midrange like the dayton 2 inch dome.

Second as you have been informed the canned Dayton crossover will not work well.

This is what I would do. The cabinet shape is pretty good for spreading out internal standing waves and modes. Use a 5.25 or 6.5 inch high quality mid/bass driver so that it's edges are very close to the 8 inch woofer and the tweeter frame. Since you will be listening at close range the drivers need to be mounted as close together as possible. This is very important for a mixing monitor since the sound from the different drivers need to blend together well at close range. This means that the mid/bass driver needs to be very smooth with no bad spikes or breakups at higher frequencies. The Silverflute Wool cone drivers may work well here and they are inexpensive. Stick with a paper or polycone mid/bass since they are easier to integrate with first order crossovers.



Create an internal shelf that physically divides the woofer and midrange into two separate cabinet spaces. It will act as a brace and to separate the two spaces. Use aperiodic loading for the midrange to get more accurate pitch definition which can approximate an infinite baffle loading in a small cabinet space. Unless the space is big enough for a critical Q sealed loading I would go with aperiodic for the mid/bass loading.

For the 8 inch, you can use aperiodic and sacrifice some bass extension but have better sounding and more tonally accurate bass or go with a bass reflex loading. I would not recommend sealed for the bass for a mixing monitor unless it is critical Q.

Try to find an 8 inch woofer that can get good strong bass in a smallish space. The best one I know of is a HI VI 8.8 in needs about 1 cubic foot and goes down low and strong in that space.

Because you are new to crossover design keep the crossover points out of the fundamental music frequencies. So let the midrange driver cover about 80Hz to 2500Hz where it crosses over to the tweeter. Try to use first order crossovers but no higher than second order since you will likely be listening at close range. This will make mixing a lot easier as there will not be any phase related sound problems in the most important music fundamental range.

Also, once you have the right drivers and cabinet selected and designed Madisound can design a custom Leap crossover for you for about 45 dollars. If you don't want to test and measure the speakers yourself. While not perfect, a Leap design crossover from Madisound would destroy a canned Dayton crossover in sound quality.
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Old 30th December 2007, 07:42 AM   #10
owdi is offline owdi  United States
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The best piece of advise I can give is to build a proven design, this is too complicated for a first DIY project.

However, designing stuff is still fun, so some comments....

Your crossover does not address the cone breakup of the RS52. Try adding an inductor after, and in series with, the lowpass capacitor. Make it a really small value, then adjust it down, until you notch out the 12khz resonance peak.

How are your reverse nulls? If you flip the polarity on the RS52, do both the highpass and lowpass crossovers give you a nice null at the listening axis?

What does your vertical polar response look like?

Have you factored baffle diffraction effects into your design?

Dan
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