Advice on rear ported speakers "rasping"

[alb]

Do you have access to another amplifier?
At least you could eliminate a possible cause, while you are waiting for Epos to respond.

[Phil Bishop]

Thanks Alb, I do have a Tag p60 amp recently purchased off ebay - I will try just using this and see what happens. Phil.

[Phil Bishop]

I have tried blocking the rear ports with tissue and it reduces the problem, but of course one loses bass! A question for DSJR - with the ES14s having sponge bungs etc, why was this? Surely, one does not design a speaker with a hole and then block it up? I'm on a steep learning curve. Thanks, Phil.

[Prince of Darkness]

It's not uncommon for ported 'speakers to be provided with some form of bungs. This is to allow for tuning the bass to the room. In some cases, especially with smaller rooms, the bass can be excessive. Blocking the ports can reduce this. Alternatively, altering the distance from rear walls can affect the bass characteristic as well.

[The Grand Wazoo]

A slightly amusing story about ported speakers.
Years ago, I had a pair of B&W DM110's in a 2nd system. I often had the opportunity to play music very, very loudly without upsetting anyone. I was trying to explain the theory behind putting ports in speaker cabinets to a friend, and to illustrate a particular point, I held a small strip of paper up near to the port - while he turned the volume up.....way, way up. Of course the paper flapped about in the flow of air. Now, I wondered to myself, how far across the room can we get the port to blow the paper? So I let go. This is where I lost sight of the piece of paper as it got sucked into the hole. So my friend learnt that reflex ports suck as well as blow!

About a year later I was listening to something at a reasonable volume and happened to be looking directly at the port in question when something flopped out & landed on the floor. It was of course, the piece of paper, but the thing that I found quite interesting (and please bear in mind here before you pronounce me insane, that I work in the forestry industry and have an interest in the structure and properties of wood products) was that it had broken down into a matted blob of broken fibres. I find it intriguing that it was subjected to quite such a battering inside the cabinet.

[Filterlab]

Charming story there Wazoo, and a true indication of how much spare time you've had over the years.

It is amazing though just how much energy is transmitted through a port and indeed inside a speaker cabinet.

[The Grand Wazoo]

So my friend learnt that reflex ports suck as well as blow!

About a year later I was listening to something at a reasonable volume and happened to be looking directly at the port in question when something flopped out & landed on the floor.

I forgot to mention that I didn't actually sit there waiting patiently for a year for the paper to reappear - I did, in fact, manage to drag myself away and conduct something of a fulfilling and interesting life in the interim period.

[anthonyTD]

Thanks Alb, I do have a Tag p60 amp recently purchased off ebay - I will try just using this and see what happens. Phil.

hi phil,
this might be a daft question, but, are you sure both speakers are in phase!
in other words, positive terminal to positive on both speakers etc, because if they arent, and one bass unit is out of phase not only will you get an unusual sound, but the bass response will be lacking, and the cones on the speakers will move further than their normal travel and make the kind of sound you describe!
just a thought.
regards,anthony,TD...
PS, when checking this dont take for granted that just because the plug thats in the positive socket is red that is on the positive side of the cable!
trace it all the way back to the amp and make sure its going to the positive terminal!

[Phil Bishop]

Wow, What a lot of interesting debate and reminiscences this subject has generated! As for the phase issue Antony, reds certainly go to red, black to black, etc. However, someone once told me to muck around with this and experiment with different permutations. Also, I remember once having a hi fi test disc which was suposed to check phase (years ago) and my speakers then certainly did not do what they wer supposed to. I seem to have a lot of bass....perhaps too much "boomy" bass, but it seems to vary a lot. What do you suggest I should do to experiment? Just swap the terminals round on one speaker? Many thanks - all so helpful - Phil.

[anthonyTD]

Wow, What a lot of interesting debate and reminiscences this subject has generated! As for the phase issue Antony, reds certainly go to red, black to black, etc. However, someone once told me to muck around with this and experiment with different permutations. Also, I remember once having a hi fi test disc which was suposed to check phase (years ago) and my speakers then certainly did not do what they wer supposed to. I seem to have a lot of bass....perhaps too much "boomy" bass, but it seems to vary a lot. What do you suggest I should do to experiment? Just swap the terminals round on one speaker? Many thanks - all so helpful - Phil.

hi phil,
all speaker drive units have to be in phase with each other, ie, both bass units must be either positive or negative phased, sometimes the tweeter is deliberately put out of phase with the main driver on both speakers. what you can try is this, if the speakers your using are bi -wire-able, and thats how you are using them, then you can try putting the tweeters [high frequency units] out of phase with the bass drivers and see if that helps.
if your not sure how to do that, all it means is instead of the positive wire going to the positive of the tweeter, put the negative wire to the positive on both the speakers but leave the wires as they are on the bass drivers, see how that sounds, any thing your not sure about just ask...
anthony.