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Multi-Way Conventional loudspeakers with crossovers

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Old 29th January 2013, 02:21 PM   #1
Fradbut is offline Fradbut  United Kingdom
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Default First Timer Loudspeaker Constructor

Hi Folks, my first loudspeaker and before I put hand to saw, any ideas, good or bad on the following ? Help much appreciated.

SEAS CA22RNX
SEAS MCA15RCY
SEAS 27TFFC
Box volume 65 L tuned to 26 Hz
Port 7cm diameter pipe, 21.3cm long.
Winspeakerz gives a flat response giving F3 at 36 Hz

I'm trying for a 1970's 8 inch rock sounding system !!

Many thanks
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Old 29th January 2013, 03:18 PM   #2
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Have you got measuring gear and crossover design software?

If not, i'd build these.
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Old 29th January 2013, 03:41 PM   #3
Fradbut is offline Fradbut  United Kingdom
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Thanks for the response. I've got Winspeakerz software from which it gives me a flat response tailing off at F3 at 36 Hz. (In theory). I'm going to download the True Audio real time analyzer, get myself a mike, knock up a demo and test it. I got the idea from Troels Classic but wanted the challenge to try it on my own. Probably a bad decision.

Do you think I'm going in the right direction ??
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Old 29th January 2013, 07:18 PM   #4
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Three way speakers are very hard to get right. A two way has a much better chance of success. Parts Express sells a calibrated usb omni Mic for less than 100. Then you wouldn't need any other hardware to run it. Also check out ARTA for measurement software. The best xo design software that I have used is Jeff B's PCD.

Have fun.
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Old 29th January 2013, 07:28 PM   #5
ScottG is offline ScottG  United States
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Generally for a first time build you should always work from a proven design, with no significant changes.

The exception would be when utilizing a digital "active" crossover like from minidsp:
miniDSP 2x8 kit | miniDSP

-in combination with a usb calibrated mic:
UMIK-1 | miniDSP
or:
Dayton Audio UMM-6 USB Measurement Microphone* 390-808

You should still do some modeling first with respect to the baffle:
http://www.tolvan.com/edge/help.htm
(..though it appears that Winzspeaker covers diffraction loss.)
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Last edited by ScottG; 29th January 2013 at 07:43 PM.
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Old 29th January 2013, 08:45 PM   #6
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by Fradbut View Post
Thanks for the response. I've got Winspeakerz software from which it gives me a flat response tailing off at F3 at 36 Hz. (In theory). I'm going to download the True Audio real time analyzer, get myself a mike, knock up a demo and test it. I got the idea from Troels Classic but wanted the challenge to try it on my own. Probably a bad decision.

Do you think I'm going in the right direction ??
Yes you are going in the right direction just from one thing you said. "knock up a demo" This tells me you understand speaker building in an iterative engineering practice. So many people think they can build a masterpiece first time out. They build beautiful cabinets, but don't have the rest of it right. The result is gold plated turds and the builders loose their enthusiasm because they spent the time and money and did not get what they expected. Speaker designing is not easy, but an amateur can, and many do, build world class systems.

TrueRTA is great. Used it for years. (paid full version) Very good for tracking down noises in the room and I prefer it's quick sweep for tuning subs. But for designing a speaker, download ARTA so you can do MLS measurements. You have to get the midrange right. You need the resolution as well as the gated measurements. Some people like HOLM. I also own SoundEasy. Expensive, capable but easy it is not. Read their users manual as it is quite informative. I also always suggest reading D'Appolito's Testing Loudspeakers to understand what you are measuring.

Go ahead and spend the very few extra bucks to get a calibrated mic. If you don't, you'll just be doing it later. The small M-Audio USB preamp-phantom power unit works fine. I have had nothing but grief with emu/Creative.

An 8" three way is a wonderful combination, but I agree with the other post, not easy. For first build I would steer you to a two way. If for not the complexity, that is is so darn hard to find a really good midrange. What is complex? Phase. You have already picked very good drivers, so take your time, the result will be on your shoulders, not the drivers.

Oh yea, that 70's sound. A.K.A. the West Coast sound. Made JBL famous. Just boost the mids. May it RIP.
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Old 29th January 2013, 08:59 PM   #7
Fradbut is offline Fradbut  United Kingdom
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I hoping that with winspeakerz, TrueRTA, ARTA and a calibrated mike, I'll be heading the right way. I'll stick with the 3 way as I've already got the units but start with a test cab first.

Thanks guys for your help.
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Old 30th January 2013, 05:13 AM   #8
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Fradbut,
SEAS CA22RNX works better in 90L (BR) tunned to 22Hz.
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Old 30th January 2013, 07:31 AM   #9
Fradbut is offline Fradbut  United Kingdom
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Originally Posted by Inductor View Post
Fradbut,
SEAS CA22RNX works better in 90L (BR) tunned to 22Hz.
Ahr.... this where I get stuck. You're right, I seem to remember modelling the CA22 RNX in a 90 Litre behemoth until I thought of my wife, lounge, big boxes etc

However Troels, aka "millimetre man" models the Classic 3-Way Classic in a 37 Litre box, both vented. I've managed a theoretical flat response for a 65 Litre system, so which one's right ??

Before I threw the baby out with the bath water and falter is it possible to have one or many correct arrangements of a CA22RNX to box size and port dimensions or is one design the best ?

Also when I've tried to confirm a design I've made in Winspeakerz within another software program, they never appear to be the same ?

Thanks chaps
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Old 30th January 2013, 09:30 AM   #10
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They are as many alignments as you want. Many are possible. If you use a/various software from different "builders of speakers" they will give you different designs, dependent of the constrains. I believe that if you try the one by Wayne Parham, from Pi Speakers, (that was not the case) it will give you a compacted design. There is only one alignment that is maximized. There is no best following your constraints like WAF, or it was just not accounted for in these calculations.
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