Infinite baffle idea

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karatestu
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Re: Infinite baffle idea

Unread post by karatestu »

Lindsayt wrote: Sun Oct 20, 2019 12:29 pm
karatestu wrote: Fri Oct 18, 2019 1:07 pm Anyone here heard a true infinite baffle loud speaker ?
My Bozak Symphony speakers are not true infinite baffle speakers, but the spring effect of the air in the box is small enough for the drivers to act very similarly to an infinite baffle.

That still leaves the box though. Which is coupled to the floor through the 70kg mass of the speakers via castors. Which would be a different kettle of fish to a thick board screwed to a wall, or a smaller enclosure screwed to the floor with a whopping big hole in the floor.

Nevertheless, I am convinced that infinite baffles are well worth trying for anyone with the means to do so.

Home cinema optimum bass does seem to be about the extension and max power levels. Due to the amount of gimmicky low frequency bumps and thumps in modern Hollywood action films.

Whereas for music listening some of the extension and max power levels can be sacrificed for texture, definition, dynamics, the ability to start and stop quickly.
I agree IB is worthy of serious consideration for those who could do it. I can't believe it took so long for the light bulb to go off in my head, i think i have Simon Hickie's OB adventures to thank for that (thanks Simon :guiness; )

I got a reply on the cult forum from Thomas saying the drivers probably don't have a high enough xmax. And that having the bass drivers a distance from the other drivers would smear the stereo image.

I respect his opinion but then i am not one to be put off trying something. So the plan would be to dispense with isobaric and use two 12 inchers per channel in parallel. I would like to get rid of all speaker boxes in the room so that would mean mounting the 5 inch mid bass in the floor too . All the drivers firing upwards and all clustered together for each channel. If i can get them as near the back wall as poosible then i could mount the tweeters on the wall just behind the other drivers and angle them up so they are on axis at the listening position.

There may be flaws in this plan that i have not considerd yet

+ if the drivers are at floor level then i will get more directly radiated sound from the 12" & 5" drivers than i am getting now.
+ the floor might vibrate too much - i can probably do something about that
+ the 5" mid will be 8 ft from the ceiling rather than 5 ft. Doc said semi omni does not work with high ceilings. Not sure if 8 ft above the driver is too much
+ using two 12 " per channel will boost their output by 6dB. I may need two 5" per channel to balance the spl's
+ my wife may laugh at me. But no speaker boxes in the room may swing it ?

Anyway i can try it at the family farm and see if it works. I have a room available that is similar to my living room at home and a room below for the back wave. I am very excited about giving this a go.
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Lindsayt
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Re: Infinite baffle idea

Unread post by Lindsayt »

For the distance of the bass drivers from the upper frequency drivers, you could always use a miniDSP and active operation to delay the sound to the front most drivers.
Even if it's just whilst you are tinkering with it, to see if the principle works.

I don't think the xmax is an issue for music listening at generous but not crazily loud volumes. Even in a large room.
Especially if you're not bothered about getting a flat frequency response between 20 and 30hz - unlike the cinema enthusiasts.

Could you go for a 12" and an 18" driver instead of 2 x 12"?

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Re: Infinite baffle idea

Unread post by karatestu »

Minidsp - how dare you :lol: Richard will now be loading his lightening bolt :lol: Only joking. I am very hesitant to consider it although everywhere i read these days digital correction comes up. I guess i would not be so bothered if my only source was digital and i could slip it in between transport / streamer and dac. But i have a one box cdp with no digital out and vinyl . Another conversion from anologue to digital and back to anologue does not sit right with me.

Thanks for your thoughts regarding xmax. You are correct, i am willing to accept a falling response low down and won't be playing movies in 5 channel mode at high volumes in a large room. Everything is bespoke with me and designed to work as a whole . I could take very little of my kit to a bake off for that reason..

I see what your saying about using a 18" with a 12" but i would rather use what i have and space taken up in the floor starts to get too big. Plus i can't get 18" driver between the fllor joists. 15" would be very tight if the joist spacing is the standard 16" between centre's. The house was built in 1917 so it may not be exactly 16", i won't know until i rip up a few floor boards.

The distance between drivers thing and smearing of images - with my down firing 12", upfiring 5" and forward firing tweeter set up there is nearly 3ft between the two bigger drivers and they are firing in different directions. I don't have a problem with it but then imaging is not top of my list and semi omni has never been viewed as having the best imaging anyway.

I wonder how it will sound having no box effects or baffle loss or diffraction from the baffle being the floor and wall.

Thanks for your interest Lindsay. The thread i started at pfm has been taken off topic with talk about tannoy drivers :roll:
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Re: Infinite baffle idea

Unread post by karatestu »

More thoughts about this.

Here is a sketch plan of my room

Image

All dimensions are in cm. There is a bay window at the top where i want to place the drivers. The chimney breast may be getting removed in the near future if HS2 gets scrapped from Leeds to York :pray: If HS2 goes ahead then none of this will be happening because i will be moving :cry:

The whole floor is suspended with floor boards over joists and carpeted throughout. Whilst the chimney breast is still there then the seating plan is as it stands now is all that can be done. Any comments welcome. TV is on the wall.

A close up drawing of the business end :grin:

Image

If i put the drivers in the floor then they need to go back to the wall and just within the bay area to get them out of the way. I thought they would be best all clustered together as close as i can manage. Approx void volume under the floor boards is 4000 Litres which is over 10 times the combined VAS of all four cone drivers.

I could maybe squeeze in another 12 incher towards the radiator depending on joist position but the area covered by drivers is getting rather large by that point. I am considering a manifold but don't know if it will work yet. That would be ideal

I have no idea if this design would work.

1) all the drivers are up firing. No problem with the 12" & 5" but i am obviously concerned about the tweeter facing straight up. It would be like listening a long way off axis but reflection might help ?

2) being at floor level i will be getting more direct sound from the 12" & 5". Might not be a problem as Steve's room flooder design seemed to float his boat and i do not dislike the sound of my current speakers when i am stood up.

3) unpredictable effects of being very close to the back wall and the bay walls being angled into the room as they are.

It's a lot of work for suck it see and it ends up sounding awful.
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Re: Infinite baffle idea

Unread post by karatestu »

If i build a manifold for the two 12" drivers and arrange it so they face each other i can cancel a lot of the vibration (apparently). It could be done if the drivers are mounted so they fire parallel with the floor joists.

Tweeter needs to be angled towards the listener to some degree as i have found out through moving my little cabs about.
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Re: Infinite baffle idea

Unread post by karatestu »

It would seem that a tweeter at floor level firing at the listeners head is a bad idea. The sound is clearly located as coming from the floor which is not good. Therefore tweeter at floor level must be either angled for a mix of direct and reflected sound or pointing straight up.

Floor reflections are said to be worst. Speakers in the floor could remove the worst reflection in a room. Second worst reflection is from the ceiling but that is only true when the speakers are conventional and firing forwards. Fire the speaker at the ceiling then that is a different matter altogether.
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