I built some large transmission line speakers a while ago. The bass response is epic, but they are quite large. So I've had a play with making a compact transmission line. Stood half a metre away, they're quite good. Two metres away, though, and the bass halves in volume. You can still hear that the deep notes are there, but just quieter. What's going on? And can it be fixed?
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Sound power falls 6 dB/doubling of distance and your small ones perched up somewhere in the middle of the room vertically, so 'sounds' like it should. Set on the floor where the big one is and it should do much better. Stacking a bunch of weight on top will help too.
GM
GM
1) With distance SPL falls, but our perception of bass is dependent on SPL so the bass will sound weak as SPL reduces Equal-loudness contour - Wikipedia
2) To a smaller extent, you will hear uniform bass near the speaker but as you move away the bass also contains the room signature and that would also contribute to what you are hearing
2) To a smaller extent, you will hear uniform bass near the speaker but as you move away the bass also contains the room signature and that would also contribute to what you are hearing
OK, I'll try them on the floor when I get back this evening. It happens way more than any other speaker I've had. Could there be something going on with this particular design?
You will have standing waves in your room for such low bass. If you move around you have zero points where it is weak. If you move around more you will discover other points where you have lots of bass.
At these low frequencies there is no directivity so the level does not go down due to distance.
Jan
At these low frequencies there is no directivity so the level does not go down due to distance.
Jan
And yet the big TLs sound the same in every part of the same room. There is something different about these small TLs.
You are more than likely standing in a room mode. The bass is weak due to standing waves cancelling in and out of phase waves. Sometimes if it's just right it may be plus and minus 30 db or more. All rooms have this problem and there are different ways of making it livable.
Room modes - Wikipedia
Room modes - Wikipedia
In addition to all else said so far - “compact TL” and deep bass response - wouldn’t that be an oxymoron?
How small? Too little bass could be a symptom of too small a TL. The classic case is d’Appolito's Thor.
The other potential issue is that it is producing nice bass but you are used to overblown bass.
dave
OK, so I've tried them in a different room. The difference in near field and far field bass response has gone. It seems they don't like a long thin room.
Internally, they're 430mm tall, 150 wide and 200 deep. The cross sectional area is a little bigger than the Sd of the driver, and they have a 2:1 taper ratio. I was just seeing if it could be done.
I think that's it really. The bass is pretty good. I'm listening without EQ and the deepest notes can be heard without them sounding quieter than they should. It's just that bass drums lack a bit of thud and low bass notes feel a bit thin. Compared to a TL with an F3 of 35Hz, they would, I guess.
Internally, they're 430mm tall, 150 wide and 200 deep. The cross sectional area is a little bigger than the Sd of the driver, and they have a 2:1 taper ratio. I was just seeing if it could be done.
I think that's it really. The bass is pretty good. I'm listening without EQ and the deepest notes can be heard without them sounding quieter than they should. It's just that bass drums lack a bit of thud and low bass notes feel a bit thin. Compared to a TL with an F3 of 35Hz, they would, I guess.
Exactly my experience when the bass appears to disappear.
Play some sinus waves at low frequencies and walk around the room, you will be surprised how at some positions there is just nothing...
I have listening room 16 meters by 8.
With horn speakers the best bass is 14/15 meters from the speakers.
With horn speakers the best bass is 14/15 meters from the speakers.
You can easily calculate where the max and min points are. With 16 and 8 meters wavelength, calculate the frequency that go with that wavelength. Those are the freqs whose level varies with position in the room. Best experienced with discrete tones of course.
Wavelengths that do not 'fit' exactly in the room still have the effect but less pronounced and it will slowly vary in a certain position.
Jan
Yes. Todd Welti has experimented with it (he's one of the head scientists at Harman) and wrote about it. With 4 subwoofers dispersed in the room you get a good sound level in all spots. More than 4 subs gets you into diminished returns.
Here's a laymans version: The Benefits of Using Multiple Subwoofers
Jan
Here's a laymans version: The Benefits of Using Multiple Subwoofers
Jan
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