Horn vs Open baffle bass
It seems to me that one area where DIYers have a huge advantages over comercial systems is in bass. Conventional woofers and subwoofers suffer problems with uneven in-room response due to room modes or resonances.
Horns and open baffle dipole bass seem to be options open to the DIYer that deal with this problem the best.
1. Bass horns have a cardiod polar response pattern (I think) which means that they interact much less with room modes. In addition they have very low distortion, a very good transient response and very high output and efficiency.
2. Dipoles have a figure of 8 polar response pattern, with the same advantage regarding room modes. I'm not sure which is better. Although they need extremely large VD to get high output, they also have a very good transient response.
I'd like some comments and discussion on how they compare in terms of accuracy and their interaction with room acoustics.
* Which deals with room modes most effectively?
* Which system is more accurate?
* Which has a better transient response?
Excluding the obvious output difference as dipoles could be made with large baffles and a numbef of 18" woofers to get the desired output.
Re: Horn vs Open baffle bass
Caveat - I am prejudiced towards horns -
They're really a different approach -
Dipoles are known for dealing well with room modes.
Horns are known for feeling the "kick" in your chest -
I have never heard a dipole but considered building some - I may yet do it _grin_
However, I'm into horns at this point and am moving along those lines.
Horns generally seem to " uncompress the music" - You should hear more micro detail and resolution, and some think that this is where the magic is _grin_ - However, due to the physics involved it is hard to fit bass horns into many rooms, not to mention WAF _grin_ Horns generally have excellent or superb transient response -
I think you would do better to make your choice from type of music that you listen to and personal preference along with fitting in correctly with your listening room.
A smaller room, where you a nearfield or close to nearfield - and you listen to classical music and chamber music and don't like Rock - sounds made to order for dipoles.
OTOH, if you like to hear a heavy bass line with _slam_ now and then - and have a larger room and listen to a lot of Rock and heavy metal _grin_ - you would do better with horns -
If you have a good size listening room and want the best you can have - go _horns_ - I did warn you I was prejudiced _grin_
Always the trade offs _grin_
I posted to this thread partly to bring it back up to the top _grin_
What you wanna bet I get two posts immediately saying I'm wrong _really big grin_
of course you are terribly wrong, horns are ideal for classic and chamber music _grin_
The way I understand it, if the radiating area of the drivers in an OB are the same size as the mouth on a bass horn, you will get similar response, including 'slam'. In other words, if your bass horn has a 4' x 4' horn mouth, an OB with enough drivers to have a 4' square radiating surface would have similar capabilities. Of course, that many drivers may actually cost more to buy then building the horn!
Yes, the strengths of horns that you mentioned are well known. But still, my questions remain unanswered.
Horns are often criticised as having coloration. Does this occur in bass horns as well?
Horns are often criticised as being very large when used for bass. However, I consider the Lab 12 subwoofer isn't really that bad.
If you have a large HT or music room, then it seems to me you could fit it in. But this brings up questions of how a bass horn should be placed. If there is just one then perhaps it could be placed on its side in the middle of the main speakers, lying flat on the ground. If there are two then perhaps they should be placed either side of the main speakers.
Suppose however, that difficulties in placing them in the room meant that it was desirable to place them along the middle of the rear wall so that it fires towards the corner. Is this likely to be undesirable placement?
I'm not clear on how bass horns are different from monopoles in terms of room interactionj and placement issues. Perhaps if someone could clarify for me ....
A very good question
"Bass horns have a cardiod polar response pattern (I think) which means that they interact much less with room modes"
Where did you hear this? They have directionality, but is it cardiod?
John Kreskovís new NaO design www.geocities.com/kreskovs/NaO.html, a simpler 3 way dipole than SLís Orion, has cardiod bass, and supposedly is +6 dB on SLís diploe bass.
Youíre right that the Lab 12 sound a great option for horn bass.
There must be someone whoís heard both H & D??
The Lab12 subwoofer produces 98db @ 35 Hz at 1m. It uses two drivers with a total VD of 2.6L. You only need 10 watts to reach 108db, 100w ~ 118db.
To match this output using a dipole based on Linkwitz W-frame design, you would need:
1. 98db -> 1.6L VD required
2. 108db -> 5.2L VD required ... 4 woofers like the Lab12 driver will just make it
3. 118db -> 16.5 VD required ... 12 x Lab12 driver.
To get the high output, you would need three stacked dipole woofers on either side, each with 2 drivers.
The combined SD of all the drivers is 0.6m2
The mouth area of the Lab12 is 0.55m2
So, assuming that the Lab12 has a power handling of 100 watts, the above statement holds true.
However, with the two drivers together in a horn, I'd guess that they could handle up to 1000w. At this point the dipoles become ridiculously expensive and large.
A front loaded horn is just a sealed box with an acoustic amplifier and because the driver doesn't have to work hard, distortion is lower. It's still a monopole speaker, so floor ceiling and side wall reflections will be more of an issue than with a dipole. Also, a horn is harder to get right.
I would characterize it as a dipole is more accurate in terms of being able to clearly identify the different notes and instruments but in terms of dynamics and impact a horn is the way to go.
Something like the dipole sub consisting 6 15's per side discussed here http://www.diyaudio.com/forums/showt...threadid=35437 would be hard to beat and relatively easy to make.
Re: A very good question
Good question, I don't really know, I was hoping someone else might be able to clarify the polar response pattern. I was guessing cardiod and I'm probably wrong.
I wasn't able to open the link you included but I managed to find it anyway:
I have seen this and it does indeed look interesting, haven't been able to find it since I first found that page.
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