[ooheadsoo]

I've got one of those new Nady spl meters coming from musician's friend. It's going to be interesting. Too bad it doesn't measure above 10khz.

 

[ooheadsoo]

I feel like I'm blogging.

SPL meter came today. Nice tool. Figured out what it was in the bass that was bothering me. Two things -

1. I figured out before the spl meter came that for the last year or so, I always thought that there was a problem suckout with my room around 50hz in addition to the big suckout I have centered at 100hz, which is why ~50hz notes on a dbl. bass always sounded very bad. Well, I'm stupid. I realized that all along, it was still the 100hz suckout causing the first harmonic of the 50hz note to lack body. Duh. I can be so stupid - moreso than usual, at least.

2. My ears weren't good enough to catch a 6db rise between 125hz and 350hz when listening to a signal generator. I was surprised to see such a big bump. I could tell that the bass was messed up, which was why I bought the meter and that detection with my own ear was not in my range of experience - yet. I think I could spot this in the future with other systems, now, but I won't be trying it without my meter, now that I have one.

Now, about non-bass issues. Jeez, room issues are NASTY. When I bumped the 1khz tone to 80-90db, it was PAINFULLY obvious that the room response was all over the map. No, not dropping off the chart as I go off axis, but as in wild swings up and down the spectrum. I was especially painful when one ear was in a peak and the other was in a null, causing an almost painful out of phase sensation.

Get an spl meter, guys, this is a great tool.

 

[jrosenth]

Depending upon what you mean by cheap, I'm building with 4 1/2" fostex ($35.00 from Madisound) along with their $35 supertweeters - plus good cap and resister (tuned by ear) and cabinet materials - double ported gets down to 55hz and up past 20K witht he tweeter - add an extra bottom chamber for sand and you have a pair of towers for aound $200. Should be interesting to see what comes of of them.

 

[JaZZ]

Quote:

Originally Posted by ooheadsoo Now, about non-bass issues. Jeez, room issues are NASTY. When I bumped the 1khz tone to 80-90db, it was PAINFULLY obvious that the room response was all over the map. No, not dropping off the chart as I go off axis, but as in wild swings up and down the spectrum. I was especially painful when one ear was in a peak and the other was in a null, causing an almost painful out of phase sensation.

That's an absolutely normal phenomenon and not reserved to your room. Room reflections do cause nasty phase effects, that's inevitable. You can only avoid them by listening through headphones.

Quote:

Get an spl meter, guys, this is a great tool.

Yes, but don't draw the wrong conclusions from it. You can't equalize reflection-based FR distortions without distorting the direct-sound frequency response, so it makes little sense to completely rely on SPL meters or frequency-response plots. The only area where equalizing based on room-measurements makes sense is low frequencies where speakers and room form an acoustic entity.

 

[ooheadsoo]

Quote:

Originally Posted by JaZZ That's an absolutely normal phenomenon and not reserved to your room. Room reflections do cause nasty phase effects, that's inevitable. You can only avoid them by listening through headphones.

Obviously. Did I say it was reserved for my room? We're both merely stating the obvious for the sakes of others on this forum. Knowing it happens, hearing it happen, and verifying and measuring it are different things, though.

Quote:

Originally Posted by JaZZ Yes, but don't draw the wrong conclusions from it. You can't equalize reflection-based FR distortions without distorting the direct-sound frequency response, so it makes little sense to completely rely on SPL meters or frequency-response plots. The only area where equalizing based on room-measurements makes sense is low frequencies where speakers and room form an acoustic entity.

I have over 50 lbs. of fiberglass in my room already doing room treatment duty. You need A LOT of this stuff to make a significant difference, and lacking that, EQing the bass for the listening spot is mandatory. I've planned to buy 3 or 4 more bags of fiberglass for bass treatment for a while, and some 6lb.pfc rigid fiberglass for reflections but there's nowhere in my room to stash it all...As you may be implying, the room response varies by over 30db all over the room and the problem lies in the time domain, not the FR domain, so EQ is only a bandaid in the end. Room treatment is still the answer. However, if you looked at these in room measurements, you could almost come to the conclusion that all our technical discussions on speaker dispersion are well null and void, given these +/-20db in room fluctuations compared to some measly 3-6db drop off in the high frequencies. I might hypothesize that you would need either a rather well treated room or speakers with very limited dispersion for an objectively significant difference. Failing that, the room modes may overwhelm any significant on and off axis discrepancies. Perhaps my next experiment should be constant directivity given a lack of room treatment...

Given what a cross over does, I have no problem with using EQ. However, you do raise a good point. Unfortunately, I don't have RTA software...yet

Looks like more fiberglass is ultimately the order of the day...

 

[rickcr42]

Real cheap would be to cannibalise older "el cheapo" stereos including consoles from the sixties and seventies.What we consider "audiophile" now was once commonplace just put into bad boxes.
I have some sriosly good ancient Anico Fostex,Pioneer,Jensens plus many off brand/rebranded full rangers i got for like $2 by pulling them from the crap boxes that once applied to a good enclosure kicked major a*s (either small monitors for nearfield listening or TQWT or "pipes",all good).

Weaknesses ?

Ultimate volume levels,extreme highs and extreme lows AWOL,both easily remidied with the addition of a sun and a supertweeter (70hz/10khz),can be FUBARed with improper driving (use a SE amp either SS or Triode)

Strengths ?

The middle where most music lives is done pretty much as good as it can be done there being no crossover to muck things up.Small scale music,the human voice,acoustic instruments,and if at the computer about as good as it gets in the nearfield plane of listening with a 2W SET amp.Ten feet out more TQWT/Pipe/Rear Horn/Open Baffle (BIG !) and 10W SET and you will know why so many like the single speaker single stage amp sound.

at least that has been my experience screwing around with speaker DIY.YMMV

 

[ooheadsoo]

I couldn't figure out who asked for a pic of my setup (did someone ask?...I don't remember clearly and I can't find the post,) so I just decided to throw it up here. It's hardly ideal, but that's what I have to work with, for now.