Not getting powerful sound out of Tuba HT LP

[Jan-Kees]

For a long time now, I struggle to get a powerful punchy sound out of my Tuba HT LP. I tried a lot of things. First it seems it was out of fase with the front speakers, now I fixed that with the distance setting in the Lexicon MC-8, it sounded good yesterday, but today it sounds soft again, I just get that somewhat muddy/soft sound from it, not snappy/fast at all. I am combining them with klipsch La Scalas in a THX Baffle Wall. It sounds better with the baffle wall than without it, like I had before, but still not great. I use only Harman Kardon PA200 and PA2400 amps for all my speakers, are those not good for amplifying subs like the Tuba HT? I am also using a MiniDSP for EQ in combination with REW. How can I get that powerful sound everyone is talking about?

[Seth]

Most likely a room placement issue. Have you done a sub crawl? Place the sub at your primary listening position, play the content you like to listen to, and crawl around the perimeter of the room listening for locations where the bass is loudest. Those spots are most likely to be the ideal subwoofer placement locations in the room to get the response you're looking for. It's unfortunate, but the ugly truth is, the place you would like to put the sub is almost never the ideal location for sub performance.

[Jan-Kees]

Well, my HT is my living room and kitchen, and I have a baffle wall now where all the front speakers are housed. The wall does good things for the speakers and bass, because it eliminates the indirect soundwaves. Before I was sitting in a nul, now that's not the case anymore. But I am talking about the sound, I have decent bass, it blends with the front speakers, but it's woolly sounding. Like it has a warm sound signature. I was wondering if I can chance that with a different (plate) amp, maybe a digital amp? What is a good (plate) amp for the Tuba HT?

[Bruce Weldy]

it's woolly sounding.

Sounds like an EQ issue.

[Bill Fitzmaurice]

Whatever is wrong, if anything, would show up on an RTA taken at the listening position. BTW, a baffle wall has no effect on a subwoofer. It only affects speakers that otherwise would be 1/4 wavelength distant at some frequency within their pass band. Crossing at 80Hz the shortest wavelength a sub passes is 4.3 meters, so the only way a THT would have a wall reflection issue is if it was facing out from the wall, which the plans specify one should not do. The LaScalas would absolutely benefit from a baffle wall.

[Seth]

Have you thoroughly checked all the joints, driver gasket, and driver mounting screws to make sure you don't have any leaks in the cab?

Do you have a screenshot of your REW measurement of the tuned system you can post?

[Jan-Kees]

Well there is a boost from 130hz to 200hz from the La Scala's. And a big dip around 40hz from Tuba HT. Green lines with EQ in MiniDSP, not much different, which indicates standing waves...?. (All with 1/6 smoothing).

[Bill Fitzmaurice]

That 40Hz notch is probably a boundary reflection. It's the source of your problems. Either the sub is 2 meters from a boundary or your listening position is.

[Jan-Kees]

This picture shows my situation. Not typical HT room, its a compromise... (it's one open space)

[DaveMacKay]

Following with interest.

I have two THTLPs and La Scalas in a long, narrow room so that I am interested in learning more about how to identify boundary reflections, and how to make the best of limited placement options. Also, can DSP help much in dealing with a room’s shortcomings?

[Bill Fitzmaurice]

I'd say that 2.25 meters to the wall behind the LP is the problem. Take a measurement with the mic 30cm from the wall.

[Seth]

The mouth of the sub is also about the same distance from the side wall. It would be worth flipping it end to end and testing again too, even if it means it's behind the baffle wall.

[Jan-Kees]

I'd say that 2.25 meters to the wall behind the LP is the problem. Take a measurement with the mic 30cm from the wall.

Okey, I will take a measurement 30cm from back wall. But are you suggesting a listening position 30 cm from back wall?

[Jan-Kees]

The mouth of the sub is also about the same distance from the side wall. It would be worth flipping it end to end and testing again too, even if it means it's behind the baffle wall.

Well, I had the sub flipped as a starting point, but the position where it is now is giving a slightly flatter response, not night and day difference.

[Bill Fitzmaurice]

But are you suggesting a listening position 30 cm from back wall?

If that's where the response is best it's either that, moving the LP closer to the front wall, moving the sub to the back wall, or adding a second sub on the back wall. As noted here viewtopic.php?t=398

If there is a 'prime directive' when it comes to sub placement it is this: Never place subs with their radiating planes between 2.5 feet and 8 feet of a boundary. If you do at some frequency the within the 35 to 100 Hz passband, depending on the distance, the reflected wave will be 180 degrees out of phase when it meets the original wave again, cancelling it out.

The same applies to the listening position.

can DSP help much in dealing with a room’s shortcomings?

Not much. If you fill a major dip at one listening position with EQ it will result in a peak at another position. If you and everyone else sit in one small area that may not be a problem, but over a large area it will.