Should I use a sealed enclosure or a ported enclosure for an mtm when crossing over to a sub? Seems like a ported might help with some of the lower end diffraction loss due to open space on a bookshelf design. Is that really necessary or would it be better to go sealed? Using Dayton audio ds175-8 x2 and dc28f-8 x1.
I had a similar question a while back. I think it depends mostly on your Dayton driver, which kind of box is it best suited for?
I found a quote in another thread, and I recall looking at these specs and dividing the numbers to see what would work for me.
Another thing to consider, is that some drivers can perform well in either type if enclosure. My opinion is that transients will be snappier from a sealed enclosure. Take that with a grain of salt. There are certainly a lot of vented enclosures with lots of kick, and there are also some sealed enclosures that leave a lot to be desired. But generally speaking it's easier to build the sealed enclosure, and it will be more forgiving to slight volume errors, etc. Again that's IF your Dayton is suitable for a sealed enclosure. Personally I think the transients are more important in the mid bass because a lot of the perceived kick and slam from percussion instruments comes from higher frequencies than we tend to think. We tend to think bass is in the 40hz range, but really up around 100 or 250hz is where you'll find the slap of the drum stick against the drum skin, some harmonics of that are even higher.. Sorry I'm rambling on.
One last thing to consider, and at the moment I can't find where I read it, but you'll have an easier time with the crossover if the midrange is sealed. Something about baffle step compensation being more complicated if the mid is ported, or it's easier to sum the frequencies at the crossover region if there is not a port that must be considered.,... Don't quote me on that, but my mid could have worked in either and I chose sealed for it because it seemed to me it would be more simple, and more likely to give me the results I wanted, my bass is ported though.
I found a quote in another thread, and I recall looking at these specs and dividing the numbers to see what would work for me.
Another thing to consider, is that some drivers can perform well in either type if enclosure. My opinion is that transients will be snappier from a sealed enclosure. Take that with a grain of salt. There are certainly a lot of vented enclosures with lots of kick, and there are also some sealed enclosures that leave a lot to be desired. But generally speaking it's easier to build the sealed enclosure, and it will be more forgiving to slight volume errors, etc. Again that's IF your Dayton is suitable for a sealed enclosure. Personally I think the transients are more important in the mid bass because a lot of the perceived kick and slam from percussion instruments comes from higher frequencies than we tend to think. We tend to think bass is in the 40hz range, but really up around 100 or 250hz is where you'll find the slap of the drum stick against the drum skin, some harmonics of that are even higher.. Sorry I'm rambling on.
One last thing to consider, and at the moment I can't find where I read it, but you'll have an easier time with the crossover if the midrange is sealed. Something about baffle step compensation being more complicated if the mid is ported, or it's easier to sum the frequencies at the crossover region if there is not a port that must be considered.,... Don't quote me on that, but my mid could have worked in either and I chose sealed for it because it seemed to me it would be more simple, and more likely to give me the results I wanted, my bass is ported though.
Hi Andrew,
The answer IMHO depends on your primary use of the speakers, placement and their cut-off frequency.
The second largest issue with proper sub integration is the final electro-acoustic slope between the speakers and the subwoofer. THX for home specifies an 80 Hz cut off and a sealed enclosure for satellites. Why? Because adding a 2nd order active high pass filter to the speaker response to a speaker with a sealed cabinet ends in a 4th order, Linkwitz-Riley (LR) aligned filter, which together with a subwoofer with a 4th order active low pass filter will result in perfectly matched satellite to subwoofer transition. In addition to good matching, you'll also be able to reduce the stress on the satellite amplifiers by cutting out frequencies they no longer need to reproduce, or so the theory goes. Alternatively, you can run the L/R full range, use a ported enclosure which will give you a 4th order high pass filter function, and integrate the sub with that. What you won't benefit from is the dynamic range of an active crossover since your amp will still do 20-20kHz.
However, that's not the biggest issue. The single largest issue with proper subwoofer integration is the room itself. Having control of the resonant modes in a room is key. If you are willing to add proper acoustic treatment and measurements, then you can probably align either a sealed or ported speaker with the sub well enough. If not, you'll never be satisfied and integrating the sub will take over your life. 😀 Also, a well treated room may never feel like it needs a sub. If you can't do that, then trying to extend the bass down another octave can wreak havoc on your sound quality. Better to have no sub at all than a poor sounding one say I.
Personally, my stereo speakers are ported and go down to about 40Hz (-3db). I run them full range at all times. The subwoofer comes on only for movies and to fill in for the small center and surround speakers that can't do less than 120Hz.
Best,
Erik
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I just checked out the Dayton audio ds175-8. Given the specs I would say you must go vented. The 106Hz cut off of the ported enclosure is just too high. Plus, those are some tiny cabinets either way, might as well get as much bass as you can. 🙂
With a ported cabinet you can get to around 70 Hz. Since you'll automatically have around a 4th order high pass function, a subwoofer should be easy to cozy up to that without needing extra filters except perhaps for movies.
Best,
Erik
So if I understand this correctly, the diffraction loss is basically like a second order high pass filter? I will probably go with .85 cu ft with a 3" port 8 in long tuned to 45 hz. Does anyone think it might be wise to consider designing a transmission line versus the bookshelves I'm planning? Would the difference in stability of a tower vs. bookshelves on a stand make much difference? I personally prefer the look of the booksheves but don't want to sacrifice low end response. Would TL maybe bring up the low end to give me a more extended rolloff. By the way, I like to run full range with a sub for movies and no sub for music usually. When I upgrade my sub I'll run mains active crossed at 80hz.
I think you should go ported too. I ran the math on the formula I mentioned and got 115.xxx something like that if I remember. Also, thanks to the other poster, I didn't know that about THX standard of 4th order roll off above the sub.
It makes sense.
The transmission line idea is interesting. Do you already own these speakers, or are you still choosing?
I started my project almost a year ago it seems, my goal was high efficiency. I spent every weekend and several evenings for months reading at diyaudio, other books, and simulating different drivers in WinISD.
Someone suggested early on that I find a well reviewed good sounding complete plan and follow it to the letter. I didn't do that because I wanted to "learn" and "design my own". I am pleased with how it sounds, and I've even measured it with a measure mic and I think it's decent.
Point is, it will be a faster path, and you may even get better results if you can find a TL that someone more experienced has figured out. If you follow such a plan, it must include crossover details as well (you probably already know the importance of getting that right)
Many people complain about MTM being a flawed kind of design, but I don't understand exactly why, but driver placement is critical.
For a transmission line, I think hornresp is the program to simulate box and port sizes, but that one for me is harder, and I still haven't learned it yet.
I'm at a loss to advise you, other than to say I like the floor stander idea. Look for someone's proven plan for a TL with your driver would be my suggestion.
You may want to search and/or post in the Multiway section of DIYaudio too.
Good luck, and be sure you have fun. I love this stuff!
It makes sense.
The transmission line idea is interesting. Do you already own these speakers, or are you still choosing?
I started my project almost a year ago it seems, my goal was high efficiency. I spent every weekend and several evenings for months reading at diyaudio, other books, and simulating different drivers in WinISD.
Someone suggested early on that I find a well reviewed good sounding complete plan and follow it to the letter. I didn't do that because I wanted to "learn" and "design my own". I am pleased with how it sounds, and I've even measured it with a measure mic and I think it's decent.
Point is, it will be a faster path, and you may even get better results if you can find a TL that someone more experienced has figured out. If you follow such a plan, it must include crossover details as well (you probably already know the importance of getting that right)
Many people complain about MTM being a flawed kind of design, but I don't understand exactly why, but driver placement is critical.
For a transmission line, I think hornresp is the program to simulate box and port sizes, but that one for me is harder, and I still haven't learned it yet.
I'm at a loss to advise you, other than to say I like the floor stander idea. Look for someone's proven plan for a TL with your driver would be my suggestion.
You may want to search and/or post in the Multiway section of DIYaudio too.
Good luck, and be sure you have fun. I love this stuff!
No idea what you mean by diffraction loss here, but a sealed cabinet behaves like a 2nd order high pass filter, yes. A ported cabinet like a 4th order.
If you could get your -3 db around 40 Hz or so you'd be in better shape. This is possible with a 6.5" driver, in a ported environment, or TL design with the right driver. Try this one instead:
http://www.parts-express.com/visaton-w170s-4-65-woofer-with-treated-paper-cone-4-ohm--292-566
Best,
Erik
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