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Old 14th October 2012, 12:48 AM   #1
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Default first speaker project

Hello. This is my first post on this forum and my first speaker project. I have chosen the drivers, designed the enclosure and designed the crossover after consulting a few different books and websites, and was hoping someone with more experience would be able to let me know if i am heading towards a decent sounding system.

7" Woofer - Dayton RS180S-8
Tweeter - Dayton RS28F-4

I'm planning on crossing over at 2000Hz using a LR2 crossover with a zobel network on the woofer. The difference in SPL is 0.4db, so i'm not sure whether to put an L-pad on the tweeter or not.

I've gone for a ducted port enclosure tuned to 35Hz. I'm planning on making this a tower with a total height of 1.5m (@5ft) by sealing off the correct internal height with a solid partition.

Is there anything here that seems wrong? or anything that i've missed? Also I am intending to add a sub at some point, is there anything i need to consider before i build these speakers or can i make the sub fit into this system once it's built?

Thanks in advance for any help.
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Old 14th October 2012, 01:25 AM   #2
Jay is offline Jay  Indonesia
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If you have already bought the drivers... because speaker design is not as simple as it seems, first, try to find a working design from internet using the same driver combo. If the design has good review or you know the designer is good, you can use his design. If you are sure you can make a better speaker, use that design to understand a bit about the drivers (assuming that you are new with the drivers).

Are you saying that you will use textbook or online formula for calculating the crossover? If so, then find FRD and ZMA files of both drivers. It is easy to simulate crossovers (without measuring and hearing a prototype) that will outperform online crossover based speaker. Many here can help you design such crossover.

If you plan to integrate a subwoofer, it is better if your 2-way is sealed instead of vented. But you may design the enclosure so that you can easily seal the port when needed.

0.4dB more on tweeter response? I prefer R at the input of the HP filter, than an L-pad.

Port tuned to 35Hz with 7" driver? Seems very low. It is better if you can show your simulation charts.
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Old 14th October 2012, 01:35 AM   #3
tvrgeek is offline tvrgeek  United States
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As with any metal cone woofer, the breakup will cause big problems. My experience with the RS drivers confirms as with every other metal driver, you need a 4th acoustic at least and still may need to put a notch on the woofer breakup. You have picked pretty darn good drivers, and a reasonable crossover point.

To pad or not to pad. Well, only your ears will tell. If you do a good 3/4 inch radius on all 12 of your box sides, you will need less pad that if sharp edges. You did not mention any BSC. Unless you are building in-wall speakers, you will need to deal with this or they will sound terribly bright and pushy. Download The Edge and play with it. Also go over to True Audio and read the excerpts from Olson's original paper. Is I mention radius the edges. Yes, it is important enough to saw twice, or maybe three times.

Adding subs is easy. The 180 goes low enough that you have a lot of choice in crossover point. 60 is a good number.

Now, has all your work so far been on paper? Do you have any measurement capability? Without measurement, the final voicing is a longer process. Just like we did in the 70's, you sit around with some brews and listen, discuss what you think you hear and tweak. It can be done. Measuring finds the issues much quicker but your ear is always the last word.

Very low tuning. Remember, that this is a pretty small driver and I would not use it much below 50 or so at anything like music levels. So, just be very careful. When you add a sub, use a real external crossover so you can take the lows out of the mains and turn them up. ( plug the port is not a bad idea ) Have you thought about a low Q sealed box? If you have not already, get WinISD so you can see the frequency/displacement/power rating charts and it will tell you if you can really use it that low. 35Hz is more like a 12 inch woofer, not a 7. Music levels at 35 Hz may produce displacement the driver can do only once.

One last bit of advice. PROTOTYPE. Don't make fancy cabinets just to find out when you measure the impedance or response it was wrong.

Note, my RS150's have a third order electrical LP on the woofer at 1800 and a second order electrical on the tweeters at, 1900. ( Seas tweeters). That is how they wound up. The result is very close to LR4 acoustic with oversized first inductor on the woofer providing the BSC along with additional tweeter padding. The third order crossover, as well as the 150's breakup being higher than the 180, let me not do a separate notch on the woofer. I was going to add little paint dots to the rim if I still had problems, but it was not needed.

I don't do a conventional L-pad on the tweeter. I add a series resistor which makes for a more stable load for the crossover, and then do the final pad with a second resistor on the input of the network. Unconventional, but I find it works very well.
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Old 14th October 2012, 01:36 AM   #4
tvrgeek is offline tvrgeek  United States
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Seems like we have a quorum.
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Old 14th October 2012, 01:44 AM   #5
sreten is offline sreten  United Kingdom
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https://sites.google.com/site/undefinition/core-2-way

Hi,

Forget your (very wrong) crossover design and use the above.

No point making it 5ft tall, just put the tweeter at or slightly above ear height.

35Hz tuning sounds very reasonable for this driver, in 20L to 25L.

rgds, sreten.
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Old 14th October 2012, 01:46 AM   #6
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maybe you want to check this out

https://sites.google.com/site/undefinition/diy/amiga

@streten you beat me by 2 minutes
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Old 14th October 2012, 02:08 AM   #7
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by sreten View Post
No point making it 5ft tall, just put the tweeter at or slightly above ear height.
What is the height of your ears, sreten?
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Old 14th October 2012, 03:37 AM   #8
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Jay View Post
What is the height of your ears, sreten?

Hi, very near most peoples sat on a couch or an armchair, rgds, sreten.
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Old 14th October 2012, 01:02 PM   #9
Dissi is online now Dissi  Switzerland
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Hi newbuilder,

Just to give you an explanation to the statements above, a simulation of the RS180 in 25 litres without crossover:

RS180.jpg

The spl rises because of the baffle step and heavy resonances show up at the top end. The art of crossover design is to find a filter, that brings the frequency response close to the desired target function. If successful, the woofer will have a flat spl around 81 dB. As the tweeter has 90 dB, you will need a L-pad for sure.
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Old 14th October 2012, 02:15 PM   #10
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Hi, thanks a lot for all the replys. I havnt bought anything yet, as i wanted to see the response to my plans. So far all my calculations (crossovers, enclosure frequency etc) have been based on textbook charts, i dont have any computer programmes. I don't think I'll my box design other than dropping the height to 4' and rouding the edges. I'll use the crossovers from that link provided by sreten and lduarte, keep it external for a while and tweek the crossovers and pipe length with listening tests.

One thing i am a little confused about is that i was under the impression that the RS180's were designed to be in a ported enclosure due to their EBP = 75, but a few people have suggested that they shouldnt be ported when i add the sub. Would pluggin the port mean i would need to change anything about my original crossover or would that be solved by having a low pass filter on the woofer when i cross it over with the sub?

Once again, thanks for all the suggestions.
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