Enclosure design help

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duanestorey

duanestorey

Member
Joined 2010
#1
Hey everyone,

I've been reading some books on designing/building a speaker cabinet. It seems like a fun project over the winter, and I'll have some time.

I do have a question though about speaker enclosures. I look at a speaker, for example the DA175-8 7" aluminum cone woofer. It has parameters of 8 ohms, Qts of 0.58, Vas of 16.3L, Fs of 39Hz. When I use online calculators to determine the optimum enclosure size for sealed vs ported, I get 33.5L for sealed, and 54L for ported (using this calculator - https://www.diyaudioandvideo.com/Calculator/SpeakerBoxEnclosure/)

But when I go to various websites, it lists this:

Optimum Cabinet Size (simulated using something called Bass box 6 pro):
Ported: 1.2ft^3 (33L)
Sealed: 0.46ft^3 (13L)

So what's the deal? Why is there such a huge discrepancy between what's listed on the manufacturing website, and what the online calculators show? When I look for completed builds as well, many of them look pretty small based on these numbers, so I'm a bit confused.

Thanks.
 
#2
The deal is that there are many degrees of freedom. In a sealed box you essentially have system Q and box volume. Box volume increasesa s Q decreases. A system Q between 0.5-0.8 is typical.

Put a hole in the box and the number of degrees of freedom explodes. Now you have to look at the curve shape, and much more.

Now stretch that box so that one dimensions is considerably larger than the others (ie a typical tower) and the reflex morphs into a quarter-wave resonator, a ransmission line of some sort. That can be taken even further by playing with shape.

Qts of 0.58, Vas of 16.3L, Fs of 39Hz
Click to expand...
Sufficient to design a basic sealed or vented enclosure. Not enuff to properly do more.

Looks like 35-40 litres for sealed (as small as 10 doable), the Q makes a reflex tricky, i can’t (quickly, find an alignment i could live with. It would probably work in a heavily damped TL.

dave
 
#3
planet10 said:
The deal is that there are many degrees of freedom. In a sealed box you essentially have system Q and box volume. Box volume increasesa s Q decreases. A system Q between 0.5-0.8 is typical.

Put a hole in the box and the number of degrees of freedom explodes. Now you have to look at the curve shape, and much more.

Now stretch that box so that one dimensions is considerably larger than the others (ie a typical tower) and the reflex morphs into a quarter-wave resonator, a ransmission line of some sort. That can be taken even further by playing with shape.


Sufficient to design a basic sealed or vented enclosure. Not enuff to properly do more.

Looks like 35-40 litres for sealed (as small as 10 doable), the Q makes a reflex tricky, i can’t (quickly, find an alignment i could live with. It would probably work in a heavily damped TL.

dave
Click to expand...

So how are you exploring these degrees of freedom (ie how did you know that 10L might be doable)? Is there some software you are using? Should a person ignore those online calculators then and invest in some software to be able to tweak volume etc to see end result?
 
#7
duanestorey said:
So how are you exploring these degrees of freedom (ie how did you know that 10L might be doable)? Is there some software you are using? Should a person ignore those online calculators then and invest in some software to be able to tweak volume etc to see end result?
Click to expand...

Yes i am using a software aid. MacSpeakerz. Only available for Windoz now.

The online calculators tend to be too simplistic and try to remove some of those degrees of freedom.

There is decent free software.

dave
 
#9
However, in this forum you can receive better help from the other members of two programs that are the most used:
Win Isd : Ideal for those who start from scratch. There are several tutorials. It is the one I use

http://www.linearteam.org/


Horn Resp : Here is the favorite and there are very good advisors. I don't know if have tutorials, because when I modeled my speakers, I directly said to myself, "this is not for me"
 
#12
Here's the link for The Hitmakers, Paul Carmody's web site:

https://sites.google.com/site/undefinition/bookshelf-speakers/hitmakers

The Karma Indignias are in the Parts Express Project pages:

https://projectgallery.parts-express.com/speaker-projects/karma-indignia/

Both are bookshelf size, ported enclosures, Paul's use the Vifa BC25TG tweeter and the Karmas use the Dayton DC28F.

I've seen a German DIY project which use a transmission line enclosure but can't find the link, some Googling on 'DA175 DIY speakers' might turn up something.

Geoff
 
#13
duanestorey said:
Hey everyone,...So what's the deal?
Click to expand...

The deal with loudspeaker design is to try all viable options before making final decision, possibly practicing your own T/S parameters measurement. Qts of 0.58 isn't suited all that well to a vented cabinet, neither is to a sealed one. In a vented one, bass might appear a little bit unprecise or boomy, depending where you put the speakers in a room. Sealed version could potentially sound better, thinner in bass, which can be compensated by being closer to room corners.
 
#15
Thanks.. Sorry for the remedial questions, but why would they choose two drivers in that build? Is it because that particular driver is somewhat inefficient? What's happens when you put two speakers in the same enclosure, I guess SPL goes up by 3db? Would they do that to match a bright/sensitive tweeter, or just to get more bass? Just curious about why someone would put two in a cabinet and not just one.
 
#16
Lojzek said:
The deal with loudspeaker design is to try all viable options before making final decision, possibly practicing your own T/S parameters measurement. Qts of 0.58 isn't suited all that well to a vented cabinet, neither is to a sealed one. In a vented one, bass might appear a little bit unprecise or boomy, depending where you put the speakers in a room. Sealed version could potentially sound better, thinner in bass, which can be compensated by being closer to room corners.
Click to expand...

Thanks.. Yah it's an odd duck in the speakers I've listed. I see lots of websites that show speakers like that as Car Audio speakers, but I also show other Hifi websites showing them as hifi speakers. Are they both? I find it interesting that there are several different groups using the same speakers differently.
 
#17
duanestorey said:
Thanks.. Sorry for the remedial questions, but why would they choose two drivers in that build? Is it because that particular driver is somewhat inefficient? What's happens when you put two speakers in the same enclosure, I guess SPL goes up by 3db? Would they do that to match a bright/sensitive tweeter, or just to get more bass? Just curious about why someone would put two in a cabinet and not just one.
Click to expand...
An MTM with two 8 ohm drivers connected in parallel, like the Zaph design, will be 6dB louder than a single driver.

Your amp can driver the speakers at a lower volume (gain) setting, which should mean lower distortion; or you can better annoy the neighbours. I'm sure someone else will have a better explanation!

Main disadvantage of MTMs from my point of view is that they look a little odd and it's harder to get the tweeter at ear level.

The DA175 isn't as efficient as some other 6" drivers such as the DC160, RS180 or Peerless 830657. I haven't used it but it's well liked.

Geoff
 
#18
GeoffMillar said:
An MTM with two 8 ohm drivers connected in parallel, like the Zaph design, will be 6dB louder than a single driver.

Your amp can driver the speakers at a lower volume (gain) setting, which should mean lower distortion; or you can better annoy the neighbours. I'm sure someone else will have a better explanation!

Main disadvantage of MTMs from my point of view is that they look a little odd and it's harder to get the tweeter at ear level.

The DA175 isn't as efficient as some other 6" drivers such as the DC160, RS180 or Peerless 830657. I haven't used it but it's well liked.

Geoff
Click to expand...

I'm not an audio snob by any means, but in Canada I had a set of Paradigm 15B speakers that were absolutely incredible. Every single person that came to my house was amazed, and I loved listening to music on them non stop. I unfortunately had to sell them when I moved to Europe (too expensive to ship), and since them I've been through three sets of speakers, and they all paled in comparison. Maybe I just had a perfect room in Canada, I don't know. But there was something magical about those speakers. The DA175 speakers remind me a bit of how the Paradigm drivers looked (and of course, sound is more important in the long run, but it sure is nice when the speakers look bad-*** too, no?)
 
#19
GeoffMillar said:
An MTM with two 8 ohm drivers connected in parallel, like the Zaph design, will be 6dB louder than a single driver.

Your amp can driver the speakers at a lower volume (gain) setting, which should mean lower distortion; or you can better annoy the neighbours. I'm sure someone else will have a better explanation!

Main disadvantage of MTMs from my point of view is that they look a little odd and it's harder to get the tweeter at ear level.

The DA175 isn't as efficient as some other 6" drivers such as the DC160, RS180 or Peerless 830657. I haven't used it but it's well liked.

Geoff
Click to expand...

In terms of drivers, are there particular ones many people are using for home builds? Any that stand out? Appreciate all your help, I'm slowly piecing the whole landscape together. My current home audio set is Dali Oberon 3s, but they seem pretty boring to me compared to the Paradigms I had in Canada. I just have a Denon home theatre amp here, so maybe my amp in Canada was better, not sure. But I'm looking to try building some stuff that makes me happier -maybe it's objectively worse than the Dalis, but I'm aiming to make myself happy.
 
#20
Hard to say. Sounds like you're looking for design/kit recommendations* rather than drivers. That you preferred the Paradigm bookshelves to the Dali is all one has to go on, so some might say go for metal driver designs.

*INB4 Piccolos or fullranges mentioned 😎

Check out Goran's various designs as a starting point - mainly all high quality drivers and bookshelf designs with some commentary on how they sound

And M Chua has done a couple designs with the Dayton driver you mentioned https://ampslab-spk.com/hifi-drivers-2/ one as a sub, one in a 2-way
 
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