Tweeter impedance/off axis issues.

ben62670

OK so I said I was going to leave my speakers alone for a while. Didn't happen. I busted out my test tone CD today, and found that I was boosting the upper mids(tweeter level 2.2k+) to compensate for the roll off of the highs due to both listening near 45 degrees off axis, and the rising impedance curve of the tweeter. The speakers are actively crossed, and when the output at the XO point is matched the higher frequencies start rolling off very gradually at 5k, and it starts getting steeper at 8k. Polk used an RC with 2.7r/5.8uf pieces to deal with the off axis/impedance issues. The Vifa has a very simlilar slope to the SL3000's, but it's DCR is seriously nearly exactly half the SL3000's at 2.9 ohms. I am thinking half the R and the C to get my nice highs back without having over bearing mids?
Thanks
Ben

Systems

ben62670 wrote: »

I am thinking half the R and the C to get my nice highs back without having over bearing mids?
Thanks
Ben

Thats probably a good starting point,the bigger the cap the lower in freq the lift in response will begin.With those values your likely only going to see (hear) results in the top octave>10k .


Is it the DT,or XT?


I have experimented with this technique before using a SEAS tweet and it did work.

ben62670

DX25. I was thinking of starting with the 1-1.2r, and and I think the only caps I have are 3, and 4.6uf. I am still using a Rat Shack meter for measure ments, but with the corrected levels you sent me I feel I can get close enough at the XO point, and "ear" the highs. I wouldn't mind if the boost started in around 5-6k, but from what I have been reading it appears that the slope is 6db:(
Here is the twweter I am using. It is great off axis till it gets out of my hearing range.
http://www.madisound.com/catalog/product_info.php?manufacturers_id=153&products_id=1115
Thanks
Ben

Edit: I was digging through my parts and found some 1.5r 12w mills, and some Dayton 3uf caps. Pretty close. The slightely higher R should boost the highs a little more to my liking. I shall test when the girls are at school. I will post my findings.

Systems

Oh yes DX not DT.Experiment and see what you come up with.Keep in mind you are never going to get the 30-45 degree off axis response to match that of the on axis shown in Vifas graph.At best with reasonable size components you might get yourself 2-3 db at the top end.



Or get yourself a parametric EQ. Doh! did I really just type that?

ben62670

GV#27 wrote: »

Oh yes DX not DT.Experiment and see what you come up with.Keep in mind you are never going to get the 30-45 degree off axis response to match the on axis.At best with reasonable size components you might get yourself 2-3 db at the top end.



Or get yourself a parametric EQ.

Yeah I know that if it boosts off axis it will boost on axis. It seems to roll off on axis too. The baffle, the impeadance, my room, or my meter I don't know, but I like my highs nice and crisy. Maybe a super tweeter like a fostex may be in order in the future. As for the EQ [puts on suit of armor] I have thought of that. Recordings are all done different, and rooms are all different. I have no idea where to start to look for a good clean single ended EQ. I have thought of running the PCM through a puter, and sending it back out via COAX to my DAC. BTW I used that little board we have to take care of the buffer stage on the DAC. I can't wait to get it installed:)
Cheers.
Ben

Systems

ben62670 wrote: »

BTW I used that little board we have to take care of the buffer stage on the DAC. I can't wait to get it installed:)
Cheers.
Ben

I was wondering how you made out with that.Hopefully it works good.

As for EQ 's I have no idea other than I have a few schematics.I did a single band parametric (for subwoofer use) on some perfboard but it was a PIB.



Edit.actually IIRC Rod Elliot has an EQ on his site.

ben62670

DIY EQ is out of the question for a while. I can't keep up as it is. I may try the PC based digital EQ. I have a decent onboard sound card, and a nice aftermarket SC so I could in, and out pretty easily. I do want to get an HTPC going for gaming on the projector, and to tweak/measure my in room acoustics VIA REW. As for the daughter card I have been having a hard time with regulators. I have a bunch of 15vdc+ regs that are dead on, but the 15vdc-, and the 5vdc+ are off. I think I am going to shy away from PE for regs in the future. Also I had a little 6-0-6 toroidal transformer that I figured would rectify high enough to use with 5vdc regs, but I am getting only around 4vdc after regulation I will take a peak at the Rod Elliot site. Between the LDR volume control research, and tweaking Jerry's and my speakers I am running out of gas. Did you look into the lightspeed yet?

Systems

ben62670 wrote: »

DIY EQ is out of the question for a while. I can't keep up as it is.

I know what you mean I have several projects uncompleted and 10 more in my head I want to try.

I have a bunch of 15vdc+ regs that are dead on, but the 15vdc-, and the 5vdc+ are off.

Is the -15 reg reading low?Is it a LM7915 orLM337?How many volts are you feeding into it?

I had a little 6-0-6 toroidal transformer that I figured would rectify high enough to use with 5vdc regs, but I am getting only around 4vdc after regulation

That should give you roughly 9 volts,which should be just enough for it to regulate.You could test it with a higher input voltage.

Did you look into the lightspeed yet?

No, I forgot all about that.Ill have to take a look at it if I can find it.

ben62670

1 LOL
2 LM7915 putting out 17-19vdc-
3 tiny toroid? No load though I should get the 5vdc. I may use a 12-0-12 I have floating around somewhere.
4 I am read page 66 now, but I do have to get to bed.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=80194&perpage=25&pagenumber=66
Page 70 has a neat little tube buffer I may want to incorperate;)

Systems

ben62670 wrote: »

L
LM7915 putting out 17-19vdc-

I would double check your ground.

I am read page 66 now, but I do have to get to bed.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=80194&perpage=25&pagenumber=66

Oh yeah it was a long sucker of a thread.:eek:

ben62670

I may be ordering some matched LDRs if you want to build one. I sent one of the guys an email. LMK
Ben

Systems

ben62670 wrote: »

I may be ordering some matched LDRs if you want to build one. I sent one of the guys an email. LMK
Ben

Yeah I would like to try one.But first I better get reading so I can figure out how it works.

Face

http://www.madisound.com/catalog/product_info.php?cPath=45_229_324&products_id=8512

ben62670

OK I am a freak:o I can't stop:(
Well I assembled my RC and installed it this morning. Much smoother not having the HP cranked to compensate for the highs being rolled off. The boost from the RC comes in too early, but did help a lot in the mids. With the components selected it is starting to rise at around 5k. I want tho push the compensation up to around 8k or so. It is real good now, but I know I can get just that little bit more out of it SQ wise. The tweeters are a great buy at the price point. I have some Wima 1.5uf MPK4's here. I know they aren't used in speakers much, but I may try them after I give these caps a while to burn in. My gut feeling says stick with the 1.5R's, and get some 2uf Sonic-Caps. Oh yeah BTW my Active XO has a 2k trim pot to adjust the dip/bump at the XO point. It is a cheap POJ that doesn't belong in any sort of HiFi equipment. It will be coming out soon and replaced by a Vishey R when I figure out the value I want. All in all my speakers were too thin and bright the way I had them setup. Now the curve is getting flatter, and they are nice and full sounding:)
Thanks much.
Ben

Ricardo

Nice talk. I don't know what the heck you're talking about, but you're impressing me

Systems

Face wrote: »

http://www.madisound.com/catalog/product_info.php?cPath=45_229_324&products_id=8512

I want three of those to try.