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-   -   FR125 / Comb effect (http://www.diyaudio.com/forums/full-range/58767-fr125-comb-effect.html)

CoryLee 8th June 2005 10:06 PM

FR125 / Comb effect
 
I am thinking of starting my first speaker project I thought full range would be a good way to go for cost and sound reasons.

I have read up on the CSS WR125 and think it sounds promising I was thinking of using two WR125st per speaker and running them full range similar to rosa plans I have seen but with out a tweeter. I have two questions

1. The last few days I have read about a FR125 with a better top end depending on price I might upgrade to the FR does any one know if a FR125st is planed? That is a 16 ohm version with a truncated surround.

2. I have heard about comb effects when largish drivers are run full range and in the same speaker is that still a problem when using only two drivers or just in larger arrays?

My room is 10 by 20 and I can only use half of it for audio – HT I am at least interested in dipole designs but could I use them is such a small space. Another limitation is SAF and they need to be toddler proof or they wont last long.

Thanks
CoryLee

Luke (Uof Iowa) 8th June 2005 10:13 PM

1. They already priced the FR125 at $150/pair. I wouldn't be surprised to see the 16 ohm version follow soon after as it did with the WR125 and at a slightly higher cost.

2. I think I've also heard the same, but I don't know how prominent it would actually be with two drivers though I'd guess minimal but someone else can probably better answer that.

I'd be interested to know the answer myself.

Timn8ter 8th June 2005 10:52 PM

Last I heard is that there would not be a 16 ohm version. The impedance curve is such that even two FR125 in parallel would still maintain a friendly load for most amps. I would still hook them to the 4 ohm taps but I know the minimum impedance would be above that. You may want to consider making it a bipole if you're not going to have a tweeter. That would eliminate pushing them up against a wall but you may only need a foot or two of space.

SCD 8th June 2005 11:01 PM

FR125 impressions
 
I heard this driver on the weekend @ the RAW event in Surrey BC. I was very impressed with the performance and the potential of this driver. It was a prototype driver in a small cabinet. You will have to check with others for the specifics on the cabinet. I thougfht it sounded great and for me was one of the hits of the show.

SCD 8th June 2005 11:05 PM

If I recall correctly I think the driver is 8ohm only no 16 ohm version at this time.

Variac 9th June 2005 12:21 AM

you could roll off one of the drivers with a filter, but maybe you think that would ruin the purity of a single driver. Often fullranges need a baffle step filter anyway and this would be one.

Bipole addresses the baffle step and probably the full range issue wthout any filter probably, so would be a good solution also.

Myself, I was thinking about two facing forward and two back. In theory I think I would need to at least roll off one of the front drivers, but I'm not ver good on theory, and theory doesn't always predict accurately.

Or maybe you could run a WR125 next to your FR125 and the WR would roll off soon enough to reduce the problem. Its probably too wide range though.

SCD 9th June 2005 03:23 PM

I have listened to and built a few bi-poles. I think this is an incredible design and if the room is wide or large enough it can create an amazingly large sound stage. The cabinet can be adjusted back and forth from the rear wall to tune to room needs and things just seem to disappear. In a small or conjested room the rear drivers add to the sound yet they do not seem to develop into as big a sound stage. Therefore IMHO bipoles are not for every room, they sound better in a room that has a bit of space to the side.
If you amp is stable to 4ohm or below there are not too many problems to worry about. Parralel conection will bring the efficiency up a bit.
I intend to try this driver in a bi-pole TL design. I am keen and think the drivers that are designed by CSS are just begining to get noticed. As I indicated in the Northwest audio thread I was quite impressed with all the designs that Al put together and could easily live with most of them. The room we were in caused a lot of colouring and bass boom but the mid range was marvelous. The WR125 coupled with a nice tweeter and not too much crossover yeilds a very nice sound to my ears. THe lower efficiency of these drivers is the primary challenge as it tends to eliminate the low power SET options.
The FR125 prototype was great. I am very interested in getting a few and working up some designs.
Good things are happening in the FR world these days.

CoryLee 9th June 2005 07:06 PM

Thanks for all your input

Quote:

Last I heard is that there would not be a 16 ohm version. The impedance curve is such that even two FR125 in parallel would still maintain a friendly load for most amps.
I don't have an amp yet but was hopping to use a low to mid line Denon or Yamaha receiver and I am not sure about there 4 ohm stability

Quote:

Bipole addresses the baffle step and probably the full range issue wthout any filter probably, so would be a good solution also.
OK this will show all of you how new and naive I am but what is baffle step? I have read about people compensating by boosting the sound around 150 hz but I don't understand what baffle step is A link would be fine as I am sure others have asked this question


Quote:

I have listened to and built a few bi-poles. I think this is an incredible design and if the room is wide or large enough it can create an amazingly large sound stage.
I am in 10 X10 ft space with one of the side or back wall (depending on furniture set up) being open to another 10X10 foot space. Is that wide or large enough?

it would be easier to put the speakers against a wall because of space issues so a dipole is a consideration but only if it would make a bigish difference in SQ


Quote:

you could roll off one of the drivers with a filter, but maybe you think that would ruin the purity of a single driver.
I haven’t yet formed an opinion on this keeping additional components out is just a way to KISS (keep it simple stuxxx)

again thanks for your input!! I would like some more opinions on if comb filtering will be a problem?

Timn8ter 9th June 2005 07:18 PM

Quote:

I don't have an amp yet but was hopping to use a low to mid line Denon or Yamaha receiver and I am not sure about there 4 ohm stability
Modern receivers are built to handle 4 ohm loads but check to make sure. I'm reasonably certain Denon and Yamaha make 4 ohm stable amps.

Quote:

what is baffle step?
http://www.t-linespeakers.org/tech/b...intro-bds.html

If you're only trying to fill a 10 x 10 room I don't think you'll need two FR125 per channel. The single driver in the 7 liter cabinet with 1.5" rear port can be placed very close to a wall which will take care of your space issue and the baffle step issue. If you have doubts about this we may be able to arrange an audition for you.

Also, an FYI. BI-pole typically refers to two drivers firing in phase in 2 different directions. DI-pole is typically two drivers firing in different directions but out of phase or it can be an open baffle speaker.

Variac 9th June 2005 07:32 PM

Timn8ter has a design that has 2 125's stacked. He might have an opinion about comb effects, etc... I guess he wouldn't have posted it otherwise! In theory if it is crossed over pretty high, there should be some effect I think, but sometimes these things aren't as audible as people claim..

http://www.timn8er.com/alegria_audio_rosa_tl.htm

How about it Timn8?


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