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.
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.
paulspencer said:
I would say they're up there with the best _grin_
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_
Regards
Ken L
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_
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!
Dave
Dave
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 ....
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
Hi Paul
"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 Kreskov’s new NaO design www.geocities.com/kreskovs/NaO.html, a simpler 3 way dipole than SL’s Orion, has cardiod bass, and supposedly is +6 dB on SL’s diploe bass.
You’re right that the Lab 12 sound a great option for horn bass.
There must be someone who’s heard both H & D??
Richard
Hi Paul
"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 Kreskov’s new NaO design www.geocities.com/kreskovs/NaO.html, a simpler 3 way dipole than SL’s Orion, has cardiod bass, and supposedly is +6 dB on SL’s diploe bass.
You’re right that the Lab 12 sound a great option for horn bass.
There must be someone who’s heard both H & D??
Richard
hurdy_gurdyman said:
I haven't heard this before, but I do know that you can work out how much VD displacement you need to get an SPL level with dipoles. There is a spreadsheet for this at Linkwitz Lab.
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/showthread.php?s=&threadid=35437 would be hard to beat and relatively easy to make.
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/showthread.php?s=&threadid=35437 would be hard to beat and relatively easy to make.
Re: A very good question
Hi Richard, is that you from the Melb Audio Club? If so this is Paul, we chatted on the basslist one time and from that I ended up going to the DIY night last year and have since joined up.
...
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:
http://www.geocities.com/kreskovs/NaO-Woofer1.html
I have seen this and it does indeed look interesting, haven't been able to find it since I first found that page.
regards,
Paul
rick57 said:
Hi Richard, is that you from the Melb Audio Club? If so this is Paul, we chatted on the basslist one time and from that I ended up going to the DIY night last year and have since joined up.
...
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:
http://www.geocities.com/kreskovs/NaO-Woofer1.html
I have seen this and it does indeed look interesting, haven't been able to find it since I first found that page.
regards,
Paul
Magnetar won't agree
Hi Paul
Yes I’m your fellow MACer. You must be professional poster! I’ve been having a debate with another MAC DIYer on the same issue.
The general consensus sound wise appears to be a trade off:
detail & fidelity vs dynamics and volume; or
hard/ heavy/ rock/ disco/ elecronica and vs HT most other music.
Any agree/ modify?
Cheers Richard
Hi Paul
Yes I’m your fellow MACer. You must be professional poster! I’ve been having a debate with another MAC DIYer on the same issue.
The general consensus sound wise appears to be a trade off:
detail & fidelity vs dynamics and volume; or
hard/ heavy/ rock/ disco/ elecronica and vs HT most other music.
Any agree/ modify?
Cheers Richard
Magnetar said:
Magnetar,
Could you elaborate a little more?
It is one thing to say that A sounds better than B, but another thing to explain WHY.
As has been discussed, horns are sealed boxes on one end with an acoustic transformer on the other. The result is more efficiency and output for the amount of distortion that would normally come from a sub with much less output. This is achieved by making the bass more directional. This means that the interaction with the room is reduced as the relative proportion of direct to reflected sound is increased.
I am probably mistaken in saying their polar response is cardiod, it is more likely to be like the front half of a dipole.
Dipoles aren't pressure loaded by a sealed box and this eliminates box coloration and I suspect that this makes them a little more "accurate."
I can't see how dipoles would actually be any better with room modes than horns. If I'm mistaken, then could someone expand on why?
What if an attempt was made to get the best of both. A dipole where both the front and rear wave was horn loaded. Or, perhaps more practical, an Infinite baffle where the front wave is horn loaded.I believe they excite less room nodes due to cancellation in the directions parallel with the front baffle. eg, you stand on the side of a dipole and you hear very little bass. The front and back waves meet as they disperse to the top and sides and cancel each other out leaving only those propagating in the front and rear directions.
The same is not true for a horn. The waves exit the mouth and disperse with nothing to cancel them out on the top and sides.
That's why a dipole sub must move a lot more air to create high SPL's, because a significant portion of the energy is lost due to cancellation of the waves at the perimeters.
You can horn load both a front and rear wave of a driver, but that's much more difficult to get right than either a typical front loaded or rear loaded sub. In doing so you wouldn't get the dipole benefit of exciting less room nodes anyway because your effective baffle width would be so wide due the long lengths needed for bass horns that there would be little, if any cancellation at the sides.
The same is not true for a horn. The waves exit the mouth and disperse with nothing to cancel them out on the top and sides.
That's why a dipole sub must move a lot more air to create high SPL's, because a significant portion of the energy is lost due to cancellation of the waves at the perimeters.
You can horn load both a front and rear wave of a driver, but that's much more difficult to get right than either a typical front loaded or rear loaded sub. In doing so you wouldn't get the dipole benefit of exciting less room nodes anyway because your effective baffle width would be so wide due the long lengths needed for bass horns that there would be little, if any cancellation at the sides.
Wow. That idea put a grin on my face, just thinking about it. The sheer wanton impracticality makes me want to run out and try it, if only I had the space.paulspencer said:
Please don't take offense, it's really a very interesting idea - I just thought immediately about the unwieldy size of many bass horn designs, then doubling the depth to horn-load the back, then needing to place the whole thing a couple meters out into the room in order to take advantage of the dipole aspects. If sound quality is inversely proportional to WAF, this monster would be world-class.
Slam
There are horn designs that load the front and back. The front is not loaded all the way to the bass.
In the tests i have done there was definately less slam with the dipoles than my horns. This was on 1/2 inch chipboard though. It colored the sound alot ofcourse. Im sure it would improve alot with a very heavy baffle but doubt that it could slam like horns.
Collin
There are horn designs that load the front and back. The front is not loaded all the way to the bass.
In the tests i have done there was definately less slam with the dipoles than my horns. This was on 1/2 inch chipboard though. It colored the sound alot ofcourse. Im sure it would improve alot with a very heavy baffle but doubt that it could slam like horns.
Collin
Many talk about "slam" in relation to horns, but I wonder what they mean in more precise terms. Are dipoles being compared at the same SPL level?
Lower distortion means that speakers don't sound as loud for a given SPL. So consider this: play dipoles and horns in a comparison at what appears to be the same volume. Due to the lower distortion, the horns may not sound louder, but if measured, the SPL may in fact be greater. Yet, the impact of the bass on your body will be felt as greater as it is in fact playing at a higher level. Perhaps this has a part to play in the "slam" factor that is often talked about.
Or perhaps it is something else ...
Lower distortion means that speakers don't sound as loud for a given SPL. So consider this: play dipoles and horns in a comparison at what appears to be the same volume. Due to the lower distortion, the horns may not sound louder, but if measured, the SPL may in fact be greater. Yet, the impact of the bass on your body will be felt as greater as it is in fact playing at a higher level. Perhaps this has a part to play in the "slam" factor that is often talked about.
Or perhaps it is something else ...
re:colourations
i really dont think this is a factor in basshorns
because: colourations in the midrange horns(and HF) are due to
parallel walls,bell mouth modes, etc etc
the waves are so long on the basshorns it doesnt matter
aslong as the approximations of the 'expo' horn then no worrys
my 40hz horn went fine first time sounded great
Im building 30hz next time with jbl 2226
It comes down to what you want
a 40hz horn will be easier and smaller(ofcourse most music is here or higher)
Try both and tell us what you think.
spend more on amps + lots of cheap speakers
or lots of wood and 1 speaker and 1 amp
my 40hz horn caused my US $ 9 woofer sound okay! cant pick it out from my jbl 2226 until the 33hz starts then the horn has no output and the low tuned jbl shines ;-)
i really dont think this is a factor in basshorns
because: colourations in the midrange horns(and HF) are due to
parallel walls,bell mouth modes, etc etc
the waves are so long on the basshorns it doesnt matter
aslong as the approximations of the 'expo' horn then no worrys
my 40hz horn went fine first time sounded great
Im building 30hz next time with jbl 2226
It comes down to what you want
a 40hz horn will be easier and smaller(ofcourse most music is here or higher)
Try both and tell us what you think.
spend more on amps + lots of cheap speakers
or lots of wood and 1 speaker and 1 amp
my 40hz horn caused my US $ 9 woofer sound okay! cant pick it out from my jbl 2226 until the 33hz starts then the horn has no output and the low tuned jbl shines ;-)
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