BillFitzmaurice.info

Hello

Up until now I've asked som quite vague questions. Sorry about this.
Now I've actually built a Table Tuba with the DCS 205-4 11 inch wide panels (narrowest version).

It gets stupid loud at >30hz - no question.

But! At lower frequencies the level obviously go down. But it starts making a locateable "humming" sound. It will shake the glasses in the kitchen at 20 hz - but its also making a very audible humming sound.

I would think that it would just stop making a sound, when the frequency is low enough - But the subwoofer is making noise at 11-15 hz aswell. Not bass, a "humm" of some sort.

Any ideas?

Most likely it's harmonics of the root note.

Haven't really noticed the same issue with my SVS. Maybe I need to pull out the mic, and measured the actual level I'm playing at while hearing these harmonics. It may be way louder than the svs?

Does the tone of the hum change with the frequency being reproduced or is it the same tone from 11-20Hz?

Also, is it noticeable while playing movies/music, or just when playing test tones?

I believe the humm changes. There's actually sound to 13 Hz from this monster, which I don't really "believe". I shouldn't be able to hear anything here.

I heard this sound, while breaking in the driver (ticking sound) is this a bad driver?
https://photos.app.goo.gl/CMDmHbGKhwrxMMTz7

You don't hear 13Hz. You do hear the harmonics of 13Hz. The way to trace a vibration is with a sine wave generator. When you find the frequency that causes the vibration it shouldn't be difficult to feel the vibrating part. I don't hear anything unusual in that video. When a cone moves that far it will make noise, even in free air.

Tell me a little about your signal path, including connection types, from the source to the amplifier.
- What's the source (CD, Web Site, REW, iTunes... ?)
- What equipment is the source being played on (PC?)
- What's the next piece of equipment in the path (AVR? Model number?)
- how is the source equipment connected to the next piece of equipment (3.5mm TRS to RCA, Bluetooth... ?)
- What's the next piece of equipment in the path (Sub amp? Model number?)
- How is that connected (RCA to RCA?)

and so on

I'll do a full write up later when I get time

I just tried again, going from 15 Hz to 30hz. The bass I deeper, the closer I get to 30 Hz. Everything up to that tone is a much higher frequency. It's clear that the horn take over At 30 hz, I just don't want it to make this higher sound below.

Right now it's running on a digital board amp 100w. Tpa-something. Input is RCA from the phone. Tone generator.

Got the same sound from the avr (chromecast-youtube-20 Hz tone video-rca from subwoofer out-tpa Amp)

Right. I connected the miniDSP and highpassed the sub at 24 hz, 48 db.

I think it's a placement issue, as the SVS also had a lower level below 30 hz in this position. So playing the sub in a null it makes sense, that I can only hear distortion / harmonic overtones.
Also - I think I had a groundloop, which is amplified as i turn up the sub. I've placed the amp near the AVR - no groundloop issue.

So. Playing at a high level, in a null, and amplifying a ground loop.

The sound is excatly the same as this, when he starts the sweep. When it's starts the sweep, you should be able to hear it play 20hz - but you do.
https://www.youtube.com/watch?v=aAhwElT ... nnel=ecut1

Once again, but with feeling...
You're not hearing 20Hz. You're hearing harmonics of 20Hz, probably sourced in the electronics

The only way to know what's in the signal is by doing an RTA. That said, I can tell that there's major midrange content, because I can hear it on my laptop speakers, which only go down to 150Hz.

You shouldn't be trying to get 20Hz out of an eleven inch TT anyway, it's a 30Hz horn.

Understood. When i built it, I hoped for some 20 hz extension because of the intro "You want a horn loaded home theatre sub that can deliver over 110dB at 20 Hz. Your wife's reply..."
Is 20 hz in this sentence a typo, or is it a wider version that is capable of this?

Anyway - The 30 hz extension is awesome, and I really feel it's more dynamic than the vented sub i have. The cannons in Greyhound doesn't go "bang" with the TT. It's more like "BAAM!"

+ it's a fun build, impressive output, and a less locatable bass.

And yes, i know I'm not supposed to hear 20 hz.

20Hz response is there, but not in an 11" width.

Right - I thought the low frequency extension had to do with the length of the horn.
Plus, i don't get why the THT 20 hz sensitivity doesn't rise from 24 inch wide to 36 inch wide. On the graphs it seems to stay at 100db, but everything else rise in sensitivity.
Is there something else in play here? What am i missing?