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jazzmessengers

Bass horns operating below K-402

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There was some discussion about this in the "dissect polar patterns" thread.

 

Bass horns to operate below the K-402 beside the Jubilee bass bin for a couple of reasons.

 

To get the K-402 at a lower height to facilitate listening to the speakers closer and still get a point source image. There are a couple of designs that I can think of that do this and I think that 3 feet tall bass horn is a decent upper limit to shoot for. For instance Inlow Sound has a dual 15", 60 Hz straight horn that is 36x36 at the mouth and 48" deep.

 

And a horn that can match the wide polar pattern of the K-402 at its lower limit.

 

For me 60-80 Hz lower cutoff for the bass horn is fine because I will be using multiple tapped sub horns to fill in the bass below that as well as smooth in room response. And my preference is for straight horns to cover that critical 60-450 Hz region. @Bjorn created a 100 Hz horn that had very nice response, and started a thread about it, I'm looking for something that will extend lower.

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Perhaps @Bjornwill share what he's doing, and/or Mike Bentz ( @DrWho) might relay their own mid-bass horn designs here.  I'll be a fly on the wall. 

 

Note that the Jubilee bass bin and Khorn bass bin both start to lose their full-space pattern control around 110-130 Hz (due to limited mouth dimensions), while the K-402 begins to lose it's full-space pattern control around 170 Hz due to length but about 40 Hz based on mouth size.  Having a horn that's about 3 feet in length will support about a 70 Hz quarter wave before the room corner or wall/floor constraint is needed, like a corner horn uses the corner of the room.  The mouth size needs to be on the order of the K-402 in order to not lose it's pattern control unless you're designing the mid-bass horn for corner (eighth space) or quarter space. 

 

Chris

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Will give this a bump, and add a picture- visually this is basically what I am trying to achieve, a midbass horn that keeps the K-402 at a reasonable height. This is just for illustration only not to show the exact type I'm looking for. I don't think Tractrix or other rapidly expanding throat horn is the way to go for my application. This came up on a Google image search originated from this forum.

 

a4boDf4.jpg

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Probably to big/wide for what you're looking for ?........... but 33 1/2" tall

mwm (27).jpg

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JWC's Mini Punch is about 30 inches tall and 32 wide (approx.)

 

Bruce

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the University Dean would fit and depth right when shoved into a corner 

here's a rough sim of the Mini-Punch, University Classic

 

 Note the Lil B__tard vented with a strong motor driver - whether it would sound "open" like a bigger mouthed horn = ?  12pe32 seems overdamped to make the best of a reflex/horn combo. (same in my K12 vs Kappa12 spec)

 

IG81 came up with a little horn for TF1020, shown below - not built so performance not known.

 

jrMbAVq.jpg

 

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On 26.11.2017 at 5:20 PM, jazzmessengers said:

There was some discussion about this in the "dissect polar patterns" thread.

 

Bass horns to operate below the K-402 beside the Jubilee bass bin for a couple of reasons.

 

To get the K-402 at a lower height to facilitate listening to the speakers closer and still get a point source image. There are a couple of designs that I can think of that do this and I think that 3 feet tall bass horn is a decent upper limit to shoot for. For instance Inlow Sound has a dual 15", 60 Hz straight horn that is 36x36 at the mouth and 48" deep.

 

And a horn that can match the wide polar pattern of the K-402 at its lower limit.

 

For me 60-80 Hz lower cutoff for the bass horn is fine because I will be using multiple tapped sub horns to fill in the bass below that as well as smooth in room response. And my preference is for straight horns to cover that critical 60-450 Hz region. @Bjorn created a 100 Hz horn that had very nice response, and started a thread about it, I'm looking for something that will extend lower.

The midbass horn I got designed would have to be deeper if it were to go lower. I didn't want to do that because:

1. The depth it requires.

2.  I believe crossing over higher is really a better option in terms of quality. Both related to frequency response and distortion, a separate bass solution will perform better. And as a side-not; contrary to what many audiophiles believe, there's no reason to run stereo below these frequencies. 

 

If we use the acoustic roll-over of the horn in the filter, around 90 Hz is about the lowest it can be crossed. 

 

I personally don't think a dual solution is a very good option for something crossed over in the 450-600 Hz area. The drivers will not sum very well and create phase issues in what I consider to be a critical range. So if you desire to extend lower, I would simply increase the depth of the horn with a single driver. A simple straight horn will not minimize the floor bounce as the horn I have, and probably not have an equal uniform polar either but it will still work well.

 

 

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On 12/27/2017 at 4:45 AM, Bjorn said:

The midbass horn I got designed would have to be deeper if it were to go lower. I didn't want to do that because:

1. The depth it requires.

2.  I believe crossing over higher is really a better option in terms of quality. Both related to frequency response and distortion, a separate bass solution will perform better. And as a side-not; contrary to what many audiophiles believe, there's no reason to run stereo below these frequencies. 

 

If we use the acoustic roll-over of the horn in the filter, around 90 Hz is about the lowest it can be crossed. 

 

I personally don't think a dual solution is a very good option for something crossed over in the 450-600 Hz area. The drivers will not sum very well and create phase issues in what I consider to be a critical range. So if you desire to extend lower, I would simply increase the depth of the horn with a single driver. A simple straight horn will not minimize the floor bounce as the horn I have, and probably not have an equal uniform polar either but it will still work well.

 

 

 

I thought the research showed that bass localization couldn't be detected below 80 Hz which is why I set that as my cut off. If it's 100 Hz then that does make it much easier.

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9 hours ago, jazzmessengers said:

 

I thought the research showed that bass localization couldn't be detected below 80 Hz which is why I set that as my cut off. If it's 100 Hz then that does make it much easier.

You can cross over as high as 120 Hz to a single bass unit without having it conflict with the stereo image in my experience. Perhaps slightly higher to, but around 150 Hz one either need two separate units close/behind the fronts or a single unit in the middle between the speakers.

 

It's also somewhat depended on how far it is from the mains. Placing it on the opposite side of the room to the mains would obviously not work well with a cross over at 120 Hz.

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11 hours ago, Bjorn said:

You can cross over as high as 120 Hz to a single bass unit without having it conflict with the stereo image in my experience. Perhaps slightly higher to, but around 150 Hz one either need two separate units close/behind the fronts or a single unit in the middle between the speakers.

 

It's also somewhat depended on how far it is from the mains. Placing it on the opposite side of the room to the mains would obviously not work well with a cross over at 120 Hz.

 

Do you think tapped horn subs on either sides (or behind) of the main speakers operating up to 100 Hz would be high fidelity? All of the ones I have looked at require a decent amount of EQ to flatten the response.

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I don't have experience with tapped horn subs myself but from what I hear from other that do, they don't seem to equal a front loaded horn in quality.

 

Personally I would go with a large front loaded horn or stacked 15" bass reflex subs. The latter equals a horn sub in quality when you have several, but the price is higher due to more drivers, cabinets and amplifier power needed to drive them. An advantage though is they can be crossed over high without any issues.

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15 hours ago, Bjorn said:

I don't have experience with tapped horn subs myself but from what I hear from other that do, they don't seem to equal a front loaded horn in quality.

 

Personally I would go with a large front loaded horn or stacked 15" bass reflex subs. The latter equals a horn sub in quality when you have several, but the price is higher due to more drivers, cabinets and amplifier power needed to drive them. An advantage though is they can be crossed over high without any issues.

 

For front loaded horns these tend to become enormous (even say ones that load down to 50 Hz) unless you were thinking something like an array of multiple woofers horn loaded so the increased radiating area at the throat allows for a shorter length (ie pictures below if I didn't describe it correctly, I know these are more upper midbass type horns, just using them for illustration)?

 

I have no "as much horn loading as possible" dogma :) I'm an AES paper/Toole fan just trying to put something together for music use only that is objectively high fidelity.

 

OnXiow6.jpg

 

jVg0prK.jpg

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Seems to me your best bet is to go with stacked woofers. Sealed enclosure will give you the smallest footprint. Well designed horn subs become big.

 

Toole and objective high fidelity; Does that go together? :)

IMO he advocates mediocre quality in every area. Speakers with serious vertical phase issues and quite high distortion, and poor acoustic environment with lateral high gain specular reflections. Not much high fidelity in that if you ask me.

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1 hour ago, Bjorn said:

Seems to me your best bet is to go with stacked woofers. Sealed enclosure will give you the smallest footprint. Well designed horn subs become big.

 

Toole and objective high fidelity; Does that go together? :)

IMO he advocates mediocre quality in every area. Speakers with serious vertical phase issues and quite high distortion, and poor acoustic environment with lateral high gain specular reflections. Not much high fidelity in that if you ask me.

 

Well I need to start somewhere, being an MD I don't have any engineering/professional audio background and I think him and Olive's papers/book are a good starting point. One specific area I do agree with him is lateral reflections adding to perceiving better sound. He is a primarily classical listener like myself and in my own experiences with all speakers (controlled directivity and not) these are desirable. And I think evidence from controlled blind listening tests are very important, which he has plenty of data on. No doubt there is still room for plenty of improvement which is why I didn't just go out and buy a pair of Revel Salons :lol:

 

The array sealed subs is also interesting. What do you think of PPSL?

 

Cost of drivers/building isn't an issue at all. I am really going for as few compromises as possible.

 

Back to the issue of tapped horn subs, the very small mouths on them for the low frequencies they reproduce has also been something that has bugged me.

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What would you choose a horn speaker like K-402 if you desire lateral reflections? A horn like K-402 minimizes side wall reflections with it's high DI. If you want lateral reflections, a horn is isn't the right choice and you might want to condsider a CBT speaker. 

 

A traditional CBT speaker has a wide horizontal dispersion, avoids the floor bounce and minimizes ceiling reflections. FIY: I'm working on a CBT design with Don Keele.

5a4ccbddeb1b8__MG_2364(Large).thumb.jpg.2ed22f8ab54341223d6561777dcc08d7.jpg

 

 

 

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Perhaps the difference in the two sides of the present discussion is really related to the difference in talking about extreme nearfield reflections (less than 3 milliseconds) rather than all "side wall reflections" of longer duration?  The K-402 is most effective in this range when placed nearer room boundaries.

 

To my knowledge, the Haas research and perhaps later psychoacoustics research hasn't shown the effects of 1-3 millisecond delays in perception by the human hearing system (relative to the 20 to 30 ms delays characteristic for the full precedence effect) but it's quite clear to me that there is a regime change in terms of phantom center channel and soundstage perception in this range of 1-3 ms. 

 

Chris

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High fidelity is accuracy. High gain lateral reflections isn't accurate no matter how constant the directivty of the speaker is. Early arriving reflections always has a negative effect on intelligibility, clarity and localization, thus accuracy. How much of the tonality is effected is dependent on the speakers directivity and surface of the room.

 

If one wants the combination of high fidelity and enveloping sound, the way to achieve this by attenuating early reflections and have late lateral diffuse energy. Which implies diffusion in the rear of the room with a good distance. This is something Toole never tried in his experiments by the way. It's also worth mentioning that Tool's research did on preference of lateral reflections wasn't very conclusive. One study was conducted in a anechoic room and it's no surprise that people preferred naked side walls in such dead environment. 

 

But either way and preference set a side; high fidelity and early arriving side wall reflections is a contradiction.

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I think that you may need to reexamine your comment:

1 hour ago, Bjorn said:

Early arriving reflections always has a negative effect on intelligibility, clarity and localization, thus accuracy.

In Toole's 3rd Ed., he references research that directly negates what you've said here, depending on your definition of "early".  So does Griesinger's latest presentations on clarity.

 

Chris

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1 hour ago, Bjorn said:

If one wants the combination of high fidelity and enveloping sound, the way to achieve this by attenuating early reflections and have late lateral diffuse energy.

This is true enough.

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