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Since there has been some interest in FR drivers on OB with OB bass these days, these are some conclusions from playing around with such a setup this weekend.The speakers are 4x4 plywood with 2x15" bass drivers per side and a Fertin EX20, plus a supertweeter. I've mentioned them before. This basic arrangement is quite nice. The room is about 20x25 with a cathedral ceiling.
I have been feeling like the FR drivers are dynamics-limited and somewhat unsatisfying with "big" music, so I dragged out an Altec 288B on a JBL 400hz exponential horn to play around with. Using the electronic crossover, I hooked this up with a 800hz 24db crossover to the 2x15" woofs. The woofers are really midbass drivers not subs, so they are intended for use up to 1000hz or so. Not bad--the crossover added considerable gunk compared to the FR, but the dynamics and headroom were enticing and the overall effect was good with loud rock. It sounded like a basic prosound setup, which is what it was, and since most rock is listened to on prosound setups, it was a familiar and satisfying effect. I listened to this for a while and appreciated the advantages to the FR setup.
Switching to the FR setup on the same music, the sound was much more coherent and satisfying, but there was the dynamic limitation and tendency to break up. I tried crossing at 100hz using the active XO, which helped a bit but not enough. I then went to 200hz, and this allowed a much cleaner sound with less compression and breakup. Also, the midbass (100hz-200hz) was better for rock via the woofers than the FR. While the FR drivers would eventually run into their limitations again at higher levels, in this relatively large room at relatively high levels (for home use), it worked well and the FR option was clearly better than the horn/bass combo. Virtually all the natural attractions of the FR drivers were retained with a 200hz XO.
So, should you run out and buy an active XO? They're great for experimentation and for bass integration (you can twiddle endlessly), but the longer term solution, in my opinion, is an optional passive XO of about 12db/octave. I say optional because I think you'd want to use a 100hz or no XO for smaller scale music, where you want to preserve the FR's full coherency and aren't worried too much about power handling. It would be nice to be able to choose different XO points depending on music.
Prosound active XOs -- at least mine -- do quite a lot of damage to the midrange, although they are delightful to work with. I think I've mentioned comparisons with the Altec horns before, but this week the conclusions were more clear.
Hope this helps.
Follow Ups:
magnetizer/demagnetizer for their ceramics for certain and maybe the alnicos.when they build drivers they use the demagnetized assemblies for ease of construction then pop the finished driver into the magnetizer for finishing.
so im thinking that a fresh ceramic might be more powerful than an old alnico that hasnt been remagnetized.
Very interesting, and thanks for posting your comments. I currently let my Fertins run fullrange and like you tend to think they can sound overworked on some material. I expect that I'll be trying something similar in the near future.
Agreed that the XO at 200Hz is the best for big music.
I put mine a bit higher with the AER fullrangers at 220Hz
with a digital Xover. Still experimenting...
Went the way with passive XO, did not like it,
sounded muddy to me.
I understand that you want an optional XO.
Hi NL,I'm one of the interested folks, and I found your post quite thought provoking.
I'll ponder more, but have some "quick" questions:
1. What active XO are you using?
2. "but the longer term solution, in my opinion, is an optional passive XO of about 12db/octave" Do you mean line-level passive?
3. Did you try crossing over at just above 200Hz--say 300 or so?
4. Any thoughts on whether the grunge you hear crossing over to the FR is due to the active XO, or is it due to having the XO point in the crucial vocal range (e.g. 800Hz)?
As you demonstrated, higher XO points unburden the FR, so I'm wondering how high (and by what method) I can XO and still maintain exquisite vocals.
More to come. ;^) Thanks again for the info!
George
The XO is a Behringer non-digital model, the CX2200 or something like that. You can get them on eBay for less than $100. They are XLR only so you have to make your own RCA-XLR cables, which is easy.I'm referring to line-level passive. Actually I already made a PLLXO for a 100hz cutoff, but I haven't been using it because it's for 100K input and my amps are 10K. Actually the present amps are inverted chip amps, and I'm not so sure about using filtering before an inverted stage. Maybe it's OK.
I didn't try going higher than 200hz, but I don't think I'd want to. It's fun to play with an active XO because you can do things like mute out individual drivers and listen to what is coming through each driver. 200hz seems like a natural cutoff between bass information (drums and bass) and midrange -- vocals and lead instruments etc. Maybe 300hz would be OK too. But you can really tell why the 800hz-1200hz range is dangerous. You're really splitting the sound in half, with the fundamentals of vocals and lead instruments coming from one driver and the overtones from another. Put it this way -- you can listen to the FRs crossed at 200hz and enjoy the music, but listening to the Altecs crossed at 800hz produces just noise.
As for the "grunge" I was mainly referring to the problems of a crossover in the sensitive voice range. After all, I was using the same XO at a lower point for the FRs as well. However, the XO itself adds a lot of electronic grunge to the sound.
Anyway, I tried 200hz at it was a nice compromise between freeing up the FR by cutting out the bass and preserving the FR cohesive sound.
Hey NL,Thanks for the clarifications--more good stuff.
I'm excited about putting together a system like yours, and appreciate your experiences. For me it's all about the vocals--if those aren't right, nothing else matters. But I'm hoping for some slam too.
Along those lines, could you tell me the power of the amps you're using on the FR, and what is the FR's efficiency? I'm assuming the limit you heard was speaker, and not amp?
I'm encouraged that you seemed able to go pretty "big" in a big room. I'll be in a smaller space, so that's promising.
Thanks again,
They are around 96db (Fertin says 100db but I don't believe them), and I was running a 25W Gainclone amp around 3V = 1W average (10W peaks probably).
I had a good experiment myself today. One basic (obvious) problem with OB's is the size baffle required to get bass. (I have 4x4's myself and they do pretty good, but too big for my room (and they cut out some of the wall bounce I like)). So I decided to try a compensation network to cut down the highs enough to get a balanced presentation with a sub-optimum baffle (12" FR (guitar) driver with only itself as the baffle). First I tried the normal BSC procedure and that worked to some extent but not enough. So I tried a 6db/octave LP coming in @~ 2xFs (lower and you loose some of what little bass you have to begin with). Tonal balance is pretty good!
Bypassing the coil with a resistor and or cap can adjust the highs. BUT :( Mr. Distortion (IM?) The bass fuzzes up the mids and highs since they are at such a comparatively low level......
?
have to bend down for mine
https://www.wmballen.com/ProductDetail.cfm?product_id=215
too far for comfort? - maybe it would be better to make a faux opdn baffle coax with small cone strapped across a 15" woofer?? Eminence 15 (parameters unknown but ~beta size magnet) at e-pay go for ~$55 ea including jacked-up shipping - are there cheap but good lil FR to keep up on a bra-strap so total price won't exceed $75? - shoulda got some of those $15 warrior 15 (~$31ea with shpping)
https://www.wmballen.com/ProductDetail.cfm?product_id=216
how much? - -here's a pigNpoke helper (??) woofer - scroll down to featured items
........
Wow!
http://www.audiocircle.com/circles/index.php?topic=36985.new;topicseen#new
?
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-057
with low-level CR cascaded - will one get generally good enough slope for 100Hz xover blend?some genre or folks like a lot of midbass power and this could compromise FR limits vs a large front load horn system (or even my karlson)
transitions in some coaxial to compression driver & their horn can be a problem.
open baffle and single drivers can be nice and sometimes less fatiguing than multiway. I like CH250 so far with harpsichord although missing some fundamentals.
a nice ringy 511 might work for Bon Scott (?)
When I am in Tokyo I go have a listen at Hino Audio where you can try a wide range of famous speakers. All of the horn systems have that crossover discombobularity in the midrage -- and I'm talking about mega-classics like Tannoy Autographs, JBL Paragons, Urei-modified 604s, etc. You don't really notice it unless you hear a fullrange driver side-by-side, and then the multi-way sounds like it has marbles in its mouth.These experiments make me particularly interested in systems which avoid crossovers in the 300-4000hz range. I have a set of 1936 Western Electric 200hz horns with drivers. They go up to 5K or so. Also, the BMS coaxial compression drivers are intriguing because they go down to 300hz but on the upper end cross at about 6kHz, instead of the 1500hz or so that is common.
Another interesting approach would be to use larger FR (wideband actually) drivers for the 100hz-6000hz range and cross to a tweeter around 6K. Then you could use something like a 12' no-whizzer driver, and I have my eye on the Tone Tubby drivers for this purpose. That would give you a lot of midbass-midrange power and efficiency for larger-scale music, but maybe preserve most of the merits of the FR approach.
Please let us know if you go the TT route for experiments. I am looking hard at the 12 Alnico TT. I run B200 w/ 80hz & 150hz PLLXO 1st, with active OB bass @ 150hz 4th. Cantus G2 at .22uf single cap,.. rotation of very small SET's & PP 300B for FR's. Yep those TT's look very intresting, even the 10's..
Just a thought. Dual drivers would seem to give better power handling, but I have no idea if they would cause more problems than they would solve--interference effects, etc?I've done no searching--I can't imagine this is a new idea. Price wouldn't seem prohibitive, so I'm imagining there's another downside.
Best,
"Another interesting approach would be to use larger FR (wideband actually) drivers for the 100hz-6000hz range and cross to a tweeter around 6K. Then you could use something like a 12' no-whizzer driver, and I have my eye on the Tone Tubby drivers for this purpose. "Hmmm... They look neat on the webpage, and could certainly handle power, but I see no frequency response graphs. I wonder if flat response is important for a guitar speaker?
For another, less burly candidate, how about the Fostex FF225K? That certainly has flat, whizzerless response in the 200-10Kz band. But would it offer more dynamics than your Fertin (sp?)? Maybe not?
I sure like the idea of a single driver for the vocal range.
pusning 12" up might have anohter set of tradeoffs - wonder how T-Tubby's 12" ceramic speaker fares vs their alnico? - its $120 (ebay 220079453842) - -Eminence's 10" lil buddy is $55 (fs~140)
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