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

[Denzil]

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

Hahaha, yes ! I'm puffin all the way

[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.

Yes Matt,

I do believe the boom has reduced, which is great ! So I'm going to keep the rock wool in the lower section once I put the aperiodic shelf back.

Denzil

[Denzil]

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.

Yes, I know that reducing port length will raise the tuning frequency. My gut feeling is that the ports are not really working as tuned ports with the aperiodic shelf in place. I think ports need a certain velocity, speed of air in order to work as tuned ports. With the aperiodic shelf the velocity will be reduced considerably and they will probably only act as vents.

Denzil

[Denzil]

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.

Yes Macca, there's no point in having any length of port in a aperiodic cabinet. However the Tannoy York aperiodic shelf cabinets did have a shallow port which may only have been there for aesthetics. I will eventually remove the ports. Because they also reduce the volume of the cabinet unnecessarily. But I need help to remove the ports and with social distancing, that will have to wait.

I'm going to leave the rock wool in the lower section because I do believe it's reducing the boom.

Thanks,

Denzil

[walpurgis]

You could experiment with temporarily blocking the ports. Some speakers work well with sealed boxes. You'd get a slower bass roll-off and possibly more extended bass at the cost of reflex reinforcement. If you can locate plastic document mailing tube stoppers the right size, try those. They can always be BluTacked in place.

[Denzil]

You could experiment with temporarily blocking the ports. Some speakers work well with sealed boxes. You'd get a slower bass roll-off and possibly more extended bass at the cost of reflex reinforcement. If you can locate plastic document mailing tube stoppers the right size, try those. They can always be BluTacked in place.

I tried doing that, right in the beginning Geoff, blocked all three, two and one port. Nothing sounded right. The bass reduce considerably and the speakers sounded shallow, no depth.

Denzil

[walpurgis]

Ah well. That could be because the drivers have a fair degree of self damping (powerful magnets and stiffish cone surrounds). I'm wondering if a resistive port might offer something? Goodmans did an ARU that worked that way, but for 12 inch drivers as I recall.

[Denzil]

Ah well. That could be because the drivers have a fair degree of self damping (powerful magnets and stiffish cone surrounds). I'm wondering if a resistive port might offer something? Goodmans did an ARU that worked that way, but for 12 inch drivers as I recall.

Yes Geoff, it's called an aperiodic port. In the case of Tannoy, they used a aperiodic shelf (with a resistive felt sheet on the shelf), which I had put in and then taken off. That's the topic of this disconnection which you may not have realised because of what we are calling it "aperiodic shelf)

Regards,

Denzil

[struth]

Used to be called variovents

[Puffin]

You could experiment with temporarily blocking the ports. Some speakers work well with sealed boxes. You'd get a slower bass roll-off and possibly more extended bass at the cost of reflex reinforcement. If you can locate plastic document mailing tube stoppers the right size, try those. They can always be BluTacked in place.

Reducing the air flow with drinking straws has been said to work quite well.