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XSim Power dissipation graph, risk of blowing speakers?


Chronic.sound
(@chronic-sound)
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Joined: 7 months ago
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Hello, I'm a sophomore in college and am new to designing and building speakers. I am currently working on my first speaker building project ever!

I am making two two-way bookshelf speakers on a limited budget.

Woofer: Dayton Audio DC130B-8

Tweeter: Dayton Audio DC28F-8

I am currently using Xsim to design the crossover and I ran into a question removed link When I look at the power dissipation graph (amp is at 40watt) the curves for the tweeter and the woofer are both over their rated RMS. And when I set the amp to 100 Watt, both driver exceed their max Watt rating.

I was wondering if that was an issue and that I was running the risk of blowing out my speakers, or if I was missing something, or how I could fix this issue (without exploding my budget).

Any advice, comments or questions would be greatly appreciated as I am super excited to go on with this project but have been stuck because of this issue for a little over a month.

Thank you!

100 watt
40 watt
DC28F 8
DC130B 8

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TVOR-Ceasar
(@tvor-ceasar)
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@Chronic.sound

First off, welcome to the forum! Glad to have you and we'll do everything we can to help out.

Second, links won't be available until after your 5th post, so we cannot see what you linked. (This keeps Spammers at bay)

Now, to your question(s).

While you can do what the manufacturers do and add up all the driver wattages to get a total, you really need to consider the main driver, i.e. the DC130B-8, for the real power dissipation since most of the energy will be in the lower frequencies. It takes more power to produce good bass than it does to produce good upper mid and high frequencies.

With that said, you are looking at 40W RMS and 80W Max. So, 40W is the safe average power the driver can handle on a continuous basis, while the 80W is what it can handle in short bursts, with enough time between to dissipate the additional heat created by the extra power. To be honest, there is very little music out there that will cause problems since these ratings usually deal with continuous Sine waves at single frequencies (like 1kHz) or something like Pink Noise that has many Sine wave frequencies mixed together. That will stress a driver much more than music, which is full of many varying frequencies at different levels, along with silent or "dead space" mixed in as part of the signal. This lowers the average power needed to actually reproduce music vs. Sine waves.

So I have to assume what you are seeing is the driver in free air, since you didn't say if you had measured them in the intended enclosure. This will have an impact on how well controlled the driver will be. Generally, a sealed box presents more air impedance that helps keep the woofer/midwoofer/subwoofer from very easily hitting such maximum excursions that you are seeing on the graphs. Ported boxes present their own air impedances, just know that below the F3 they tend to get less controlled. Measuring "in-box" will have an effect on the FRD and ZMA files, so take what you are working with at the moment as a starting point that is subject to change in the future. 

Now, you have a 40W amp, so you won't have to worry so much about the higher wattages until such time as you upgrade. And I doubt you'll have any real problems because, most likely, you'll start to hear distortion before any over-driving will occur. That tends to be the nature of the beast.

I hope this helps. If you have any more questions or need clarification, just ask.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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123Toid
(@123toid)
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I'll also get some thoughts on this a little later tonight. But true voice is in is head on with the power dissipation. I'll explain that in a little differently later. another thing to keep in mind, is it looks like XM is showing you that 40 Watts continuous at every frequency. So that would mean that it'd be 40 Watts at every frequency it's showing you. Which it would not happen in real life. Virtuix cad, I believe, has a better way of showing this. I don't use this function, because it really isn't helpful in Xsim

https://www.youtube.com/123toid


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Chronic.sound
(@chronic-sound)
New Member Registered
Joined: 7 months ago
Posts: 3
Topic starter  

Thank you so much for both of your responses, this being my first project I really don't want to make a mistake that will blow out my speakers 🙂

I wanted to clarify a couple of things about my project: It's going to be a vented enclosure and the amplifier I am using is the Kenwood A-63 rated to 100watt of undistorted. The frd and zma files that I am using are the ones I got from parts express as I do not have the necessary equipment to do my own measures (yet:)). The 40 watt I input into the software was just an arbitrary number as I know I probably will never use the full potential of the amplifier. 

With your advice that vituix cad was better for power dissipation, I ran the simulation. However, I have a couple questions for the "Max output" How do I know if the 100 watt advertised on my amplifier is for 4 Ohms or for 8 Ohms?

Also,

If you don't mind I have a last question: What are some things to watch out for so that I don't blow out my speakers? I know this is a repeating theme in my questions but its the one thing I really worried about and there isn't much information of the subject.

Again thank you so much for welcoming me to this community I'm truly greatful to have found this and for the time you are giving to my questions. 

Screenshot 2021 02 20 113736

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TVOR-Ceasar
(@tvor-ceasar)
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Joined: 2 years ago
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@chronic-sound

I looked online, and all I could find is the page on Radio-Museum, which is as you stated: 100W undistorted. Dated around 1989 or so. I found https://www.hifiengine.com/manual_library/kenwood/a-65.shtml and it states 55W/channel at 8 ohms. So I would expect the A-63 is probably 50W/channel (100W total) with pretty good Freq.resp. and low distortion, and rated at 8 ohms. Most home amps/receivers from that time were 8 ohm.

Now, if you keep your speakers at 8 ohm, you'll be fine. And like I said up above, you'll hear distortion before you hit the power limits. You'll be in good shape.

-Charlie
https://www.youtube.com/user/TheTrueVoiceOfReason


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Chronic.sound
(@chronic-sound)
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Joined: 7 months ago
Posts: 3
Topic starter  

Perfect, thank you so much for the help! I really appreciate it! Have a great day!


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