Posted by Roy on November 13, 2004 at 14:33:19:
In Reply to: Re: Re: Where's the Bass? posted by seadogs1 on November 13, 2004 at 07:36:47:
Seadogs,
My experiences to date indicate that the reason that you are not getting enough bass is that the membranes on your speakers are a little too tight.
The bottom 1/3rd of the speaker is responsible for producing low bass and if the natural resonant frequency for those mini panels are slightly high then you will not get a response that goes down to ~30Hz. Humidity and temperature can also effect the tension of the membrane. It is probably better for a new panel to be slightly on the tight side of ideal, then, at least if any miss handling or temperature/humidity changes occur that would slacken off the membrane your speakers would have either perfect tension or a tension that was slightly on the tight side. If the tension were to be too slack the speaker would lack life and you may even get stator slap on large bass transients.
So far I have applied probably (I have now lost count) 6 membranes to my panels to try out new coatings and charge ring designs. On every occasion (except the last time) on first trying the speaker out I have found that the speaker was bass shy. My experiences so far show me that it is almost impossible to get perfect tension onto the membrane when building the panel up initially and up until the very last covering I had to heat treat the membrane after final assembly to slacken it off.
On my very last membrane application I tried out a new approach. Before I fitted the two speaker halves together I tuned the membrane using my heat gun. I would gently tap each mini panel with my finger and depending on the tone I heard I would apply heat to get what experience told me was the correct graduation in tones from the top of the membrane down to the very bottom. After I was happy with the resultant response I fitted the two speaker halves together.
On an occasion when I heat treated one of my panels I took readings of the response before and after heat treatment, you can look at the curves I took using the link below.
Now, what to do about it.
You could leave the panels to slacken off naturally and given sufficient time you will get a perfect response from them but how long will this take. Well, It depends upon the degree that the membrane is too tight and the loudness and periods of time that you play the speakers. The time period could be weeks to many, many months.
Alternatively, you can heat treat the panel and instructions on how to do this are in our articles section here on SLOG. Great care needs to be taken.
Before you try to heat treat your membranes I would suggest you contact the factory first and talk it through, I believe that Brett is the best person to speak to for this.
Be patient with your speakers and you will be rewarded with some of the very best bass around.
Good luck
Roy
