250ti question

[FredEmmerich]

I recently picked up some 250tii speakers. I run them with a McIntosh amp, about 110/channel. They sound great but as I crank up the volume the bass seems to get muddy. Does this mean I need more power?

thanks
Fred

[johnaec]

What's the damping factor of the amp?

John

[FredEmmerich]

The owners manual says:

20 at 4 ohms
14 at 8 ohms
11 at 16 ohms

[Audiobeer]

That doesn't sound right Damping (Factor specs)? That seems very low to me. Are you sure of this? Not meaning to tick you off. And this may really get you mad but I don't want you to overlook the basics but is the polarity correct on the speaker cables?

[speakerdave]

Those damping factor numbers are about right for a McIntosh solid state amp with output transformers.

David

[Audiobeer]

Actually it should be about 100 without the autoformer and your right Speakerdave 30 or greater with. Which model do you have FredEmmerich?

[FredEmmerich]

I checked the polarity and it is correct. I have a Model MC2100 ampl. SOlid state, 105/channel. The damping factos are exactly as stated in the manual.

And I appreciate any and all help, so don't worry about making me mad, it won't happen!!

[Mr. Widget]

And I appreciate any and all help, so don't worry about making me mad, it won't happen!!

Let me try...

The amp is the problem. You need a better amp. Unfortunately that is an early Mac solid state design and they are not particularly great, especially with JBLs. The large motor structure of JBLs really work best with amplifiers with incredible damping factors. The amps I run have a damping factor of 1000. If you had a tube MC275, I would recommend you get a big solid state amp for the woofers and use the Mac for the highs in a bi-amp scenario. With this amp, if you really want to hear those speakers sound their best, you will need a different amp.

Widget

[GordonW]

Most likely, what's happening is that you are saturating the output transformers of the Mc. amp at high volume, trying to deliver the current necessary to move the LE14-1 woofers. Lot of motor, lot of moving mass= lot of current to drive them.

The suggestions here are right on, I think. A bigger, newer-design amp (say, at least 150w/ch, preferably 200 or more per channel), such as an Acurus A250, Aragon 4004 or 8008, JBL/Urei 6260 or 6290, NAD 218THX or 272, Mc. 7270, something of that ilk, should be much better suited for the 250Tis.

Regards,
Gordon.

[jblnut]

I'll cast a vote for the classic 80's Yamaha Pro gear. P2201, PC2002, PC4002, PC5002, PC2602, etc. All are at least 200wpc amps and will make your 250's come alive. Watch ebay - they come around fairly regularly....

jblnut

[FredEmmerich]

Damn, I thought I had a good amp!

Can someone explain what the damping factor is?

Thanks
Fred

[Robh3606]

Here give this a read, You are about to open a very lively discussion if history repeats itself

I use older Crowns either 150 Series 2's or PS-200's and there are no issues as far as "uncontrolled bass" with 2235's or Le-14A's. Their numbers are <400 but once you read the article you will be scrathing your head. Just get a loaner so you can to see for yourself what the differences are.

http://www.lansingheritage.org/html/...ing-factor.htm

Rob

[Mr. Widget]

Thanks Rob, I had missed that article.

Fred, sell the amp.

Widget

[Ian Mackenzie]

Damn, I thought I had a good amp!

Can someone explain what the damping factor is?

Thanks
Fred

Could be the amp needs servicing, the PS capacitors could be shot. Try another amp just to compare (borrow).

Damping factor...the most missunderstood term, do a search, plenty of articles.

If it sounds okay at normal volume levels I doubt if the damping factor is the issue, sounds like a stability problem with the amp, or feedback via the source. It could also be the back EMF from the speakers effecting the stability at high drive levels. High damping factor amps tend to be less effected by this as they represent a perfect voltage source with almost absolute zero output impedance.The transformers could be saturating as mentioned above.

Ian

[Don McRitchie]

Important factors to consider are your room characteristics and speaker placement. It would help if you could elaborate on this.

These factors, more than any hardware issue, can lead to poor bass response. Due to the human ear's response curve, it can become much more noticable with increasing volume. Even the most dynamic and articulate bass driver can be made to sound like boomy mush in the wrong environment.