Love or hate speaker cabinets I made for Tannoy MG 15's

[Denzil]

I agree. I'd take out that shelf and see how it works just as a ported design. As it is it is trying to do two separate types of bass reinforcement at the same time. Not to say that won't work it's just likely to be sub-optimal.

Yes, I'll experiment with taking the felt off the shelf and filling the bottom with glass wool.

Will keep you posted.

Thanks Macca !

Denzil

[Denzil]

Thanks so much Matt,

I'll work on taking the felt off and filling the bottom with glass wool. It's difficult to work on these cabinets. Each weights 143 kgs.

Regards,

Denzil

Hi Matt and Macca,

So I opened them up today and took off the felt from the aperiodic shelf and loosely filled the bottom with glass wool.





Here's what happened. If at all there was a boom earlier, it went away. However, along with it what disappeared is the lower end bass which I could feel in my chest. Also what happened is that the soundstage became much less impressive, there's a flatness now, the 3 D has gone. The depth has vanished. I'm not sure why all this happened. Because of taking away the aperiodic shelf ? Or was it because of filling the bottom with glass wool, or both ? I'm not really sure. But I know I need to get back to how they were earlier. I could experiment by putting the aperiodic shelf back and keeping the glass wool there. However it's very difficult working with these monsters, just moving 143 kgs is tough (with limited help due to Covid). So for now, sometime this week, I'm going to put the aperiodic shelf back and take the glass wool out. What I would like to do at a later stage (when I have more help) is keep the aperiodic shelf and reduce the port length to around 3 inches (so the ports are not tuned), making them more or less typical Lockwood aperiodic shelf cabinets.

But I'm glad I did what I did today. It was a worthwhile experiment.

I'll let you know when I experiment further but I think that may be a couple of weeks from now.

Thanks again for all your suggestions.

Regards,

Denzil

[fatmarley]

Here's what happened. If at all there was a boom earlier, it went away. However, along with it what disappeared is the lower end bass which I could feel in my chest. Also what happened is that the soundstage became much less impressive, there's a flatness now, the 3 D has gone. The depth has vanished. I'm not sure why all this happened. Because of taking away the aperiodic shelf ? Or was it because of filling the bottom with glass wool, or both ? I'm not really sure. But I know I need to get back to how they were earlier. I could experiment by putting the aperiodic shelf back and keeping the glass wool there. However it's very difficult working with these monsters, just moving 143 kgs is tough (with limited help due to Covid). So for now, sometime this week, I'm going to put the aperiodic shelf back and take the glass wool out. What I would like to do at a later stage (when I have more help) is keep the aperiodic shelf and reduce the port length to around 3 inches (so the ports are not tuned), making them more or less typical Lockwood aperiodic shelf cabinets.

But I'm glad I did what I did today. It was a worthwhile experiment.

I'll let you know when I experiment further but I think that may be a couple of weeks from now.

Thanks again for all your suggestions.

Regards,

Denzil

Well, that wasn't what I expected to happen

It looks like I'm going to have to get my measuring gear out and do some experiments....

[topoxforddoc]

Denzil,
Can I ask why they sound like in the initial new cabinet incarnation? Did you like the sound, or did you feel that something wasn't right? If they sounded good in your room, then why not just put it back to the mark 1 new cabinet configuration?
Charlie

[Denzil]

Well, that wasn't what I expected to happen

It looks like I'm going to have to get my measuring gear out and do some experiments....

I too was surprised Matt,

I thought there would be more bass but it's less, at least at the lower frequencies (at the point where you can't hear it but start to feel it). Also I think the bass was tighter, with a little more punch and better defined with the aperiodic shelf. However I do believe that there was some amount of boom with my earlier configuration which has reduced. Also, if you go by measuring equipment, it's possible that the new configuration may actually show up as being better. But there seems to be a bit of a loss of that typical Tannoy sound now. They still sound great and better than the original Lancaster cabinets but the dramatic soundstage and depth and the deep lower bass has reduced. I'm toying with the idea of leaving the bottom most part of the glasswool when I put the aperiodic shelf back which may reduce the boom but bring back all the other elements. What do you think ? Does glass wool absorb bass ? Does it reduce bass if there's too much of it ?

Also, do you have any idea what the specifications of the felt of the original Lockwood cabinets was ? In terms of thickness and air resistance ?

Regards,

Denzil

[Denzil]

Denzil,
Can I ask why they sound like in the initial new cabinet incarnation? Did you like the sound, or did you feel that something wasn't right? If they sounded good in your room, then why not just put it back to the mark 1 new cabinet configuration?
Charlie

Hi Charlie,

First of all, I'm a complete novice and experimenting. When I first built the cabinets, they were meant to be tuned, ported bass reflex cabinets. Then I suddenly decided to add an aperiodic shelf. But I still kept the ports in place which are tuned to 29Hz. So I ended up with hybrid cabinets and needed to experiment further to check it they would work better as simple bass reflex or as aperiodic shelf cabinets. As of now it appears that they work better as aperiodic shelf cabinets. However the ports are still tuned to 29 Hz, and aperiodic speakers don't have tuned ports. Eventually I would like to do another test with the aperiodic shelf in place and shorten the ports to around 3 inches so they are not tuned anymore. Then they will be pure aperiodic cabinets.

Hopefully, at some point I will come to some conclusion depending on what sounds best. This is a work in progress

Regards,

Denzil

[Puffin]

What an interesting thread this is. Hat off to you Denzil for all the work you are putting in to tune them. Just think of the muscle mass you will be gaining in the process

[fatmarley]

I'm toying with the idea of leaving the bottom most part of the glasswool when I put the aperiodic shelf back which may reduce the boom but bring back all the other elements. What do you think ? Does glass wool absorb bass ? Does it reduce bass if there's too much of it ?

Also, do you have any idea what the specifications of the felt of the original Lockwood cabinets was ? In terms of thickness and air resistance ?

Regards,

Denzil

The glass wool in the bottom will reduce standing waves, and should reduce the boomy sound you often get with ported speakers. I've always preferred it with the speakers I've built (cleaner lows), but your Tannoys are tuned a lot lower than the speakers I've built in the past, and maybe that makes a difference. I really don't know.

There are studies that have been done with enclosure stuffing, but it's still a bit of a black art.

Sorry I don't know what the felt specs are that Lockwood used.

[fatmarley]

Eventually I would like to do another test with the aperiodic shelf in place and shorten the ports to around 3 inches so they are not tuned anymore. Then they will be pure aperiodic cabinets.

If the ports are actually working like conventional ports at the moment (when the aperiodic shelf is in place). Reducing the port length will raise the tuning frequency. Even if there's just a hole in the enclosure it will act like a port. I know this as a fact, not just because of theory, but because I removed my ports once and all it did was raise the tuning frequency. But maybe they aren't working like that with the aperiodic shelf in place?

I'd be interested to know what they sound like with the port lengths reduced, but combined with the aperiodic shelf removed too.

[Macca]

Rather than shorten the ports try removing them altogether just leaving the holes, this will give a vent for the aperiodic loading to work with.

The stuffing is unlikely to have any effect on bass frequencies but you might as well leave it on the bottom there, won't do any harm.