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Multi-Way Conventional loudspeakers with crossovers

Questions about speaker building
Questions about speaker building
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Old 11th July 2018, 04:22 PM   #251
jReave is offline jReave  Canada
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And just in case I'm not posting enough graphs, I thought maybe a visual explanation of room gain and the gentle rolloff idea might help.

chart 1 - a nice gentle rolloff
chart 2 - the same alignment now with the 17' room gain added in. Flat to 30Hz
chart 3 - a sharper knee at the rolloff
chart 4 - and now with the room gain added in. Peaking now instead of flat.
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Old 11th July 2018, 04:46 PM   #252
WillHoog is offline WillHoog  United States
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When I have more time tonight I will read through that again.

About the volume thing, I said very loud. I do not have as much experience knowing exactly how much dB that is but I would say I want them to be able to get louder than my ears would want in the room. I'm guessing this would be possible but I'm not sure exactly how much dB that is. From what people told me, 110dB would be extremely unpleasant
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Old 11th July 2018, 05:49 PM   #253
chrisb is online now chrisb
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If you have any type of smart phone or tablet device, you should be able to download a free or low cost app that would have a rudimentary SPL meter function. While hopelessly inadequate for serious measurement, they can give a rough ballpark as to loudness. Yes, the venue (room) can make some difference, but 110dB at your location is pretty trucking loud, and prolonged exposure would almost guarantee serious permanent damage.
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Old 11th July 2018, 07:41 PM   #254
WillHoog is offline WillHoog  United States
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Yeah the current max I listen to is 80 to 85dB and I don't know how much 90 to 100 is because it is not a linear function. I do know that at least with earphones the higher frequencies do more damage so I should be able to boost the bass a little more.
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Old 11th July 2018, 09:34 PM   #255
jReave is offline jReave  Canada
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Every increase of 10dB is perceived as twice as loud. So 90dB is twice as loud as 80dB and 100dB is twice as loud as 90dB. Which I guess makes 100dB 4 times as loud as 80dB.

So here's a rough guestimate of your needs/desires.

At the listening position, if you want a max SPL a bit louder than you currently listen at, let's call it 90dB. But let's give yourself some headroom for very brief dynamic passages, say 6dB, so now you're up to 96dB at the listening position.

Now the way sound works is that SPL will decrease by 6dB for every doubling of distance. So if your speaker is putting out 110dB at 1 meter, at 2m it'll be at 104dB and at 3m it'll be 98dB. One meter equals 39" so 3m is a listening distance of about 9 3/4ft. Now in an enclosed room, you tend to loose just a little less SPL than the rule suggests, so in this case starting at 110dB, at about 9' you are probably at about 100dB. Maybe actually a bit more than that but I'm being conservative.

But wait, it actually gets a little more complicated than that. You actually have 2 speakers putting out 110dB not just one, so 2 together creates an added 6dB. However, there is this little thing called baffle step in which you loose 6dB in the LF, so those 2 things tend to cancel each other out. But then, wait for it... , there is also this little thing called boundary reinforcement which tends to negate some or all of the baffle step loss depending on how close the drivers are to walls and floors. With large drivers and big cabinets, baffle step loss tends to be closer to 3 or 4dB instead of the normal 6dB so finally, that leaves my example at about 102db max SPL at about 9'.

All of this is why I suggested earlier that a design goal of 110dB max SPL at 1m would be more than enough for a home environment. If you only wanted a max of about 96dB at a 9' listening position, a woofer that does 106dB max at 1m will meet your goals. And save you money too. Because many of the drivers we've been looking at so far can do that with just a single unit.

But they are your speakers, your money, your ears and your choice. Having the extra headroom does mean that the woofers will never be working at their extremes which is a good thing, they play a little cleaner that way.

Last edited by jReave; 11th July 2018 at 09:37 PM.
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Old 11th July 2018, 10:02 PM   #256
WillHoog is offline WillHoog  United States
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Yes and that is what I want, to freely move the volume within the range that my ears want to hear and not work the speakers too much... Some 808s in songs are more demanding than others and I don't want to have to wait for the beat to drop to decide what volume I should put it at like I currently do.

I was building these intending to have extra headroom.

Like I was saying 110 to 120dB doesn't matter and thats true in a way but also not. I want them to be able to play that loud and have that be the where they hit their xmax but I would never be playing music on them that loud.

Last edited by WillHoog; 11th July 2018 at 10:08 PM.
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Old 11th July 2018, 10:13 PM   #257
WillHoog is offline WillHoog  United States
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I don't know why but while trying to make the graph for the DA270 look better it seemed I needed to change the volume and end up with an unwanted F3 but after getting a good looking graph, changing the Fb to get a better F3 didn't screw it up again so now it is all good.

I still want to look at slightly higher quality drivers more in my price range to get better sound.

25.PNG
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Old 11th July 2018, 10:43 PM   #258
jReave is offline jReave  Canada
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That looks better. Very close to what I got. And that's quite a nice response. That'll be good even with movie content almost right down to 20Hz at 110dB at 1 m. And don't forget, that's a 10" not a 12". I would add that to you list of candidates.

Here's the thing - as I said before I'm really not sure what your budget is. I was going to go over that with you after finishing looking at woofers. Maybe do the Peerless and the DSA270-8 next. And if you want to look at higher quality, maybe look at the Dayton Rs270-8 too.
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Old 11th July 2018, 11:28 PM   #259
WillHoog is offline WillHoog  United States
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Ok, I want to spend $70 to $80 for each driver besides the tweeter. I don't want to spend much less than that I want to get the best quality out of my budget. However I will still do the suggested drivers later tonight for practice.
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Old 11th July 2018, 11:45 PM   #260
jReave is offline jReave  Canada
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That's all good as far as that goes. The problem is that I'm not sure that you fully realize what the full extent of the whole project will cost. Not having done this before and all that. Or in other words, what you sort of need to do is establish a budget for the whole project, and I'm not even sure if that will be for speakers only. Do you need an amp for these too?

That's what I'll need to know and then we can start breaking down the budget into individual categories. In the end, $70-80 per driver may be realistic. Or it might be a little on the wishful side. We'll have to see. But we'll get to that when we get there.
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