a newbie question - optional foam

[donkelly]

I read the insert with the 170s about the foam to put just below the tweeter if the speakers are higher than your ears.

Can someone fill me in on this - any more info than what is in the insert?

Will any old open cell foam do? Is that why it sounds so sharp?

The 170s are just about 6-10 inches above my ears but about 3 feet away.

Thanks

Don (owned 170s for about 36 hours)

[donkelly]

I read the whole thing again. 0.27 ratio or greater then use the foam.

Mine is about 26-27. so I put some door insulation foam on it. Seemed really bright, if that is the word, before. Now? I am not sure - just started listening.

I have only a couple inches behind the spekers which is probably cheating them of some bass. I could buy deeper shelves to go on the brackets screwed to the wall (not a bookcase they are on - just a shelf braketed to the wall).

If I then replace the speakers into a new setting more ear height, should I take the foam off?

[curtis]

Don,

Give Ascend a call. I believe you can get the proper foam from them.

[donkelly]

Apparently from talking to the ascend guy - I have old cbm170s. He said it had been two years since he had that question.

He is going to have an engineer email me with info.

I also asked about the 4ohm / 8 ohm thing. The booklet says 4 ohm, the website says 8ohm. Apparently it is really like 6 ohm on average, but no one has any problem driving them safely.

[davef]

Hi Don,

Many years ago we offered a specialized piece of acoustic foam to place between the woofer and tweeter. This was used to smooth out the frequency response if the listener was located at an extreme vertical angle.

We no longer offer this foam, but instead recommend angling the speaker downward to point it at the listener (this is a better solution, but not always possible)...

Since you are at a rather extreme vertical angle I do recommend angling the speakers downward towards the listening position. If this is not possible, installation of the acoustic foam would be beneficial. However, any old piece of acoustic foam will not work at all.. The foam we offered was a very specific shape and size... I can offer this to you if you wish, but again, the recommended solution is to angle the speaker downward....

Regarding impedance, the CBM-170 has a minimum impedance of 4.2 ohms, and this is what we originally based our impedance measurement on. This caused some confusion as most consumers don't understand how impedance varies with frequency and that many 8-ohm rated loudspeakers have impedance dips well below even 4 ohms... The CBM-170 has an average impedance of precisely 7.8 ohms, fully qualifying it as an 8-ohm average impedance loudspeaker...

In 5 1/2 years of CBM-170 production, I can't recall a single impedance related issue and I can safely say without hesitation that your pair of 170s can be run off any receiver or amp without worry of impedance problems.

Hope this helps!

[donkelly]

Thanks

That answers it.

I suppose my only question remaining - out of curiosity - what would sitting below the tweeter to such an angle do? Would it make it sound too bright? I could see the point of the foam, then. I would think off axis the tweeter would get less bright, less treble.

Maybe below is not the same as off axis.

In any event, I will angle my speakers down.

Thanks