My Transmission Line sounds pretty average :(

[5m3g_head]

Hi Folks, im back again with another n00b question.

As i said last time im building the following

http://www.audiokit.it/ITAENG/KitDif...EL/Line162.htm *****fixed *******

Ive just finished the first box, so i thought id try it out. At this point the crossover is not built and the woofer is doing full range.

The problem is that the bottom end doesnt seem right. Its there and sounds soild, but it doesnt seem to go that low (or loud)
Ive spent a while playing with the stuffing. Basically the bass gets better the more i stuff it. Up to the point that the stuffing is compressing, after which it sounds rubbish.
The only thing I can think of is that I used 12mm thick foam on the side walls and perhaps that is eating up too much volume.
I built it to plans, adding foam and stuffing to only the front part of the line.
Am i on the right track thinking i should get some thinner foam ? maybe 6mm or something.
All advice welcome
Thanks

[Wolf]

Re: My Transmission Line sounds pretty average :(

Hi Folks, im back again with another n00b question.

As i said last time im building the following

http://www.audiokit.it/ITAENG/KitDif...EL/Line162.htm

Ive just finished the first box, so i thought id try it out. At this point the crossover is not built and the woofer is doing full range.

The problem is that the bottom end doesnt seem right. Its there and sounds soild, but it doesnt seem to go that low (or loud)
Ive spent a while playing with the stuffing. Basically the bass gets better the more i stuff it. Up to the point that the stuffing is compressing, after which it sounds rubbish.
The only thing I can think of is that I used 12mm thick foam on the side walls and perhaps that is eating up too much volume.
I built it to plans, adding foam and stuffing to only the front part of the line.
Am i on the right track thinking i should get some thinner foam ? maybe 6mm or something.
All advice welcome
Thanks

From another DIY builder a few years back, I heard of using a lining for the walls. Bill Horn said he was using carpet-padding, but he advised against it after he found out why it didn't dig very deep. The fact is, the lining was not doing the full-job intended. The soundwaves were going behind it and ruining the tuning it was supposed to target. After he switched to another damping that prevented this fact, the tuning he desired was achieved as modeled.

With that said, I would try making sure your sound cannot reach behind the foam. This is what I received from anothers' actual experience, and not my own, so YMMV.
Later,
Wolf

[maynardg]

Re: My Transmission Line sounds pretty average :(

Many of us have had excellent results with TL designs. Here are a couple of thoughts.

This is a fairly old design. I did not see the T/S parameters from which the design was derived. The MW162 is also an old design. How sure are you that the T/S parameters match the original design specs? I've had Morel midwoofs that were way off.

Second, often, TL's rely only on stuffing and not on lining. Experiment without lining.

[5m3g_head]

Re: My Transmission Line sounds pretty average :(

maynard- unfortunatly I dont have any test equipment so i cant confirm the drivers parameters. This is my first project and i chose it because I had the Morel drivers in a small pair of bookshelfs.

Wolf - I used a foam designed of accustic deadening so hopefully it is working as planned. I'll pull it out tommorow and see what happens.

thanks guys.

[brianpowers27]

Re: My Transmission Line sounds pretty average :(

THe link to your project doesn't work.

Let's assume for a moment that the issue is not related to the stuffing. I would encourage you to build the xos and listen to the design before hunting down trouble on the t-line. It is also possible that the design needs BSC>

Do you have a good reference system to compare your work against?

From what I understand T-lines wont give you a huge performance increase over a ported design.

[Paul Carmody]

Re: My Transmission Line sounds pretty average :(

Ive just finished the first box, so i thought id try it out. At this point the crossover is not built and the woofer is doing full range.

The problem is that the bottom end doesnt seem right. Its there and sounds soild, but it doesnt seem to go that low (or loud)

I'd put money on the fact that the bass doesn't seem very full or loud being due to the lack of crossover. With no XO, you have basically zero Baffle Step Compensation. That will balance out the bass with the rest of the frequency spectrum, and therefore make the whole speaker sound FAR more full.

Thus, the TL is not the issue. You'd still have the thin sound if it was vented or sealed. Finish the XO, then start playing with the bass alignment and stuffing. Then let us know how it sounds.

[billfitzmaurice]

Re: My Transmission Line sounds pretty average :(

maynard- unfortunatly I dont have any test equipment.

Can't comment on the design, as your link is a dead-end, but getting the stuffing right on a TL demands measuring the impedance. A TL will show an impedance spike at the pipe frequency and a series of lesser spikes/ripples above that, caused by pipe resonances above the quarter-wavelength fp. Those spikes/ripples coincide with response spikes/ripples. Stuffing is added until those impedance ripples disappear, and the response ripples along with them, leaving only the spike at fp. Too much stuffing will kill the vent output and result in a loss of bass.

[5m3g_head]

Re: My Transmission Line sounds pretty average :(

sorry

fixed link

http://www.audiokit.it/ITAENG/KitDiffusori/trasmiss/MOREL/Line162.htm

[Dirk]

Re: My Transmission Line sounds pretty average :(

T-Lines aren't some magic bullett, either. :rolleyes:

But I vote with Paul. Get the crossover in place.

[curt_c]

Re: My Transmission Line sounds pretty average :(

Archived data of the MW-162 indicates it has an fs of 55 Hz, and a Qts of .95. The Q would suggest this driver is best suited to open back enclosures. In a TL I suspect it it will have a bump in the mid-bass response but will not have great bass extension, in spite of the tuning frequency, which appears to be around 35 Hz.

Something along the lines of the Dayton RS180 should work well in this enclosure, and provide much better bass extension than the Morel.

C

[Paul K.]

Re: My Transmission Line sounds pretty average :(

I took a quick look at the cabinet design you linked and I agree with Curt that the line's 1/4-wavelength resonant frequency is likely too low for this driver. The system response is probably along the lines of a "classic" tuning, meaning a highish F3 with a shallow rolloff, and that will definitely end up sounding very lean or lacking in "real" bass (not special effects bass).
Paul

Archived data of the MW-162 indicates it has an fs of 55 Hz, and a Qts of .95. The Q would suggest this driver is best suited to open back enclosures. In a TL I suspect it it will have a bump in the mid-bass response but will not have great bass extension, in spite of the tuning frequency, which appears to be around 35 Hz.

Something along the lines of the Dayton RS180 should work well in this enclosure, and provide much better bass extension than the Morel.

C

[5m3g_head]

Re: My Transmission Line sounds pretty average :(

Thanks everyone for the feedback

The crossover parts arrive early next week. So I'll built it and test further before I build the second box.

Curt reccomended replacing the mw162 with a dayton rs180. If I were to do this would the mdt29 work well with it ?

Obviously I would need a new crossover, anyone care to help me with that. Designing a crossover is beyond my skills at the moment.

cheers

[billfitzmaurice]

Re: My Transmission Line sounds pretty average :(

I took a quick look at the cabinet design you linked and I agree with Curt that the line's 1/4-wavelength resonant frequency is likely too low for this driver.
Paul

If the impedance chart is accurate fp is 55 Hz. Unfortunately the SPL chart doesn't go low enough to see what it does below 100Hz, but the claimed 30 Hz response seems overly optimistic.

[5m3g_head]

Re: My Transmission Line sounds pretty average :(

It seems the concensus is that this is a poor choice of cabinet for the mw162.

so does anyone know of a more suitable design useing the mw162 and mdt29 ?

[billfitzmaurice]

Re: My Transmission Line sounds pretty average :(

It seems the concensus is that this is a poor choice of cabinet for the mw162.

Not necessarily. A driver with a 55Hz fs isn't going to go much lower than 50 Hz no matter what the cab design. With that high a Qts it would probably work well enough to 80-100 Hz in a sealed alignment, crossed to a sub below that.