Fostex fe108 eSigma in OB ?'s

[serenechaos]

Serenechaos, I wonder if an experiment for you could be to try the OB approach as before, but add a few thick layers of say acoustical batting insulation over the back of the drivers to absorb some sound.. It would still be OB, but perhaps that could settle some of the frequencies bouncing around that offend the sq to you? I've read before that your not a fan of OB and thought about that idea but never thought to state it till now.. I've never heard an OB myself so I cannot comment, but seems like a fun experiment to try and I've already got most of the parts etc.. I think if the same happens to me as with you and your wife after listening to them, I may try some type of absorbing trick while still basically keeping it an OB type approach, then if still a no go at least it wasn't a pricey gamble and worth the learning and experience etc..

I've tried it--
to me, the more damping material behind the driver, (and less the rear wave is heard) the clearer the sound @ the listening position became.
Started w/ wool sweaters, then pillows, then 4" mineral wool "enclosure" from the wall damping experiments.

--Sounded better, more natural, but not really an open baffle anymore, is it?
(And still had all the OB problems; over excursion waiting to happen, no bass, no dynamics...)

Those who like the OB sound, that "extra reverb" added on top of the recording, the extra delay/echo of the back wave they call "open" sound, wouldn't like it though.

--But then I've always thought a three-way "full-range" with a woofer and tweeter required is more of a "multi-way," and doesn't even belong on this forum...

And yes, fortunately it was an inexpensive, easy series of experiments. Just a board w/ a hole in it.
Not really out anything.
I've now given away all the TLs, BVRs, and BLHs that were taking up space. Hopefully stick w/ front loaded horns.

It is fun experimenting, and hopefully we'll all find a sound we like...

 

[DaveCan]

Agreed Finding the right combination of what sounds good to each of us personally, and what we can live with and enjoy is the main thing..

Dave P10,
I was fortunate as my pair were unmolested raw drivers with no coatings or treatments etc. Ed shot me a mail back then that he had some new in box at a good price, so I went for it.. I was previous going to try the fe206, but that event helped make my decision, and was my first foray into the single driver approach...

Anyhow looking forward to giving the 108's a try in a new home, and the ease of build is right up my ally

 

[Jim Shearer]

DaveCan,

Sorry to be late replying, but I was off visiting a friend in Montreal.

I would not run the FE108eSig OB w/o a filter! or at least not at any significant volume or with any significant bass content. Way too easy to exceed Xmax! In the BIB you have much more control over the cones at LFs.

I did break in a pair of FE127e's on OB using a filter at 70 Hz and with peak levels around 76dB.

Maybe I worry too much, but I don't want to release the magic smoke!

Cheers, Jim

 

[chrisb]

DaveCan,

Sorry to be late replying, but I was off visiting a friend in Montreal.

I would not run the FE108eSig OB w/o a filter! or at least not at any significant volume or with any significant bass content. Way too easy to exceed Xmax! In the BIB you have much more control over the cones at LFs.

I did break in a pair of FE127e's on OB using a filter at 70 Hz and with peak levels around 76dB.

Maybe I worry too much, but I don't want to release the magic smoke!

Cheers, Jim

Jim:
I almost posted the first paragraph myself yesterday, but had no anecdotal experience on which to base the intuition.

Dave:
At the very least, you can expect substantially less IM in the lower mid-bass / midrange of the 108s when filtered. The fun part of course is deciding at what Freq and how to power the bass drivers.

For cheap experiments, a small plate amp with built-in XO could work for mono; but for stereo, you'd probably want to conscribe a 50-80 watt stereo amp/receiver and play with PLLXO.


It's a little harder to release the magic smoke from Fostex drivers with the shear power of Dave's Decware Taboo, than with the full DC rail from a chip amp.

 

[serenechaos]

I wasn't suggesting long term w/o hi-pass--
That was part of what the comment about this becoming a multi-way, etc...

And was just sharing my personal anecdotal experience, using decware, and homemade EL84 SET and PP amps for a couple months or so, @ moderate listening levels; no filters, and no smoke...
just long enough to make a decision.

-I apoligize for any confusion if not communicated clearly-

 

[DaveCan]

Thanks guys And no confusion at all

I will give them a try unfiltered just to check it out, and will keep the volume and material content in check.. My little 108's have acquired many, many hours on them now, and the last thing I'd want to do is release that magic smoke... If I enjoy what I hear then I'll do whatever is recommended in the simplest way to keep the lows out of the 108's.. I know the OB will be a much different application, but every time I've ever crossed in a sub to any of my systems previous whether it be in a auto or home, the magic number for me has always been to cross the sub at around 70hz or thereabouts.. I would imagine in the OB app we are probably thinking more like high passing the 108 at 100+ hz, so I guess I'll see when I get there..

Chris, wish you guys could hear my amp after all these hours on it now but I've gone and moved 6000+ kms away... I think way back when you and Dave gave it a listen, it was still pretty new and fresh out of the box with not much run time on it at that point.. It's settled into quite a nice sounding unit indeed.. One things for sure is the little 108's seem to match very well with that amp, and it seems a nice partnership.. Won't rock a party, but then I'm not a party guy anyhow, and I can get loud enough for my listening enjoyment...

Anyhow, even though the BIB's can extract a surprising amount of low content out of the 108's, there is still plenty more low notes that are not being delivered that I miss on some music.. So while they do a good job of providing an illusion even when playing the material with the missing info, it's time to bring in the big guns to retrieve what is begging to come forth, hence the Alphas or Goldwoods as an experiment along with the 108's on OB..

 

[Jim Shearer]

Thanks guys And no confusion at all

I know the OB will be a much different application, but every time I've ever crossed in a sub to any of my systems previous whether it be in a auto or home, the magic number for me has always been to cross the sub at around 70hz or thereabouts.. I would imagine in the OB app we are probably thinking more like high passing the 108 at 100+ hz, so I guess I'll see when I get there..

I tend to believe Martin has it right, setting the XO at 500 Hz on the mid/tweet. This really is a two-way, not a speaker plus sub such as you were previously trying. The XO point on the woofer seems strange when you first see it, but, trust me, Martin has that correct as well. With the (more or less) U-frame I built, the ~160 Hz XO plus the response characteristics of the baffle and Alpha 15 add together so that there is no hole in the freq response.

And the lower you set the XO point, the higher the cost for the parts...at least if you are doing a passive XO. If you are using a fancy programmable line level XO and bi-amping, then of course you can experiment to your heart's content.

Cheers, Jim

 

[DaveCan]

Thanks Jim... I was just generalizing about the woofer crossover point and have zero experience with the OB approach.. I totally have much more reading to do about Martins methods, and really had hoped that he had already pieced together the 108esigma on OB ,but it was the 103 that he used as far as I could find.. So much study so little time and the math makes me sleepy I love the imaginative math like what is going on at CERN and the LHC , but those equations and electrical values to do with audio etc wipe me out lol..

 

[DaveCan]

Well I've decided to get on board and try out the Alpha's in the H-frame to augment my BIB's instead of trying the 108's on OB for now.. Then if all works out well, I'll cut off the added length that I used to invert the BIB's, flip them to fire upward and stack them atop the H-Frames..

Will the H-Frames with the Alphas work okay positioned right in the room corners, angled out towards the listening position? I'll be using them as low end fill powered by a Reckhorn sub amp crossed under 100hz I imagine, and will keep my 108's as before running unfiltered in the BIB's.. The room I'm using now, there is no option to have the H-Frames well out from any room boundaries ... Wondering if it matters so much if using just for low end etc or if maybe the Betas or other may be better?

Can't seem to find the H-Frame dims again where I found them before.. Assuming 3/4inch material external dims = 17''w x 17''h x 15.75''d ? Driver baffle centered inside H-frame, with 7.5'' of cab in front of driver baffle and 7.5'' behind?

 

[Jim Shearer]

I have doubts about putting the OBs right in the corner. Normally, placing OBs 2 ft. from each wall would be considered pretty close.

Cheers, Jim

 

[DaveCan]

Thanks Jim.. I guess I will just experiment with placement/design etc, as they will be well within the min 2' distance but not right up against the walls, although still quite close though.. At least the expense to find out is not so much as to thwart the idea to try, so that's all good to have a bit of fun etc...

 

[Rudolf]

Thanks Jim.. I guess I will just experiment with placement/design etc, as they will be well within the min 2' distance but not right up against the walls, although still quite close though...

Did you take a look at the corner dipole on Linkwitz' site? Sadly Larry Selmers own site on geocities doesn't exist any longer. He suggested to rotate the H frame 90° when putting it into the corner. Very clever.

Rudolf

 

[DaveCan]

Thanks for the link Rudolf I hadn't seen that info before..

I tried to make a drawing but cannot get it to attach.. The Bass H-Frames would be angled towards the listening position close in the room corners and would still have lots of room for the back wave to escape .. Perhaps that bit of added pressure on the driver may take it lower ?? not sure...

Is there anywhere to see the exact dims for an Alpha H-Frame to use as bass augmentation? All I can find is pages of numbers and graphs which are over my head, way over

 

[rjbond3rd]

Hi DaveCan,

The internal dims MJK uses are 16" height x 16" width x 7.5" depth (on each side of the woofer).

He chooses 7.5" because that will have a quarterwave resonance of 262Hz, and unlike his MLTL's, in this case he basically "throws away" the QW resonance by crossing over around 200Hz. So the dims aren't carved in stone -- you could tweak away based on your situation if you wanted.

This is on pg. 3 of his "Comparison of the Bass Performance of Passive Open Baffle, U Frame, and H Frame Speakers".under "Geometry Definitions".

 

[DaveCan]

Thanks Robert I thought I had seen it some where before.. I can easily get lost in the mire of so many pages of info and math equations etc..

I'll be keeping my BIB's running fullrange, so I imagine the Alphas will be crossed somewhere under 100hz with this amp that I got from CSS some years back.. I couldn't see the older A-400 amp specs at CSS so here they are at this site: Funky Waves

 

[rjbond3rd]

Wow, nice amp. If you haven't bought the Alphas, you might consider the Goldwoods!

 

[DaveCan]

I had thought about that, but wondered if an 18'' can be as nice for sq as a 15'' and under? Also I had read somewhere that the Goldwoods are a step down in build quality over Eminence?? The room I'm listening now is only 10'x14' and the ceiling height is low at just under 7', so I'm thinking 15's should still knock my socks off although wouldn't get as low I guess?

 

[Rudolf]

This is the way Larry Selmer would place a H frame in an edge:

 

[rjbond3rd]

Hi DaveCan, well I'm sure opinions vary but I recently heard an OB with two Goldwood's per side (John Busch's rig at the LSAF audio event). That was the deepest bass I ever heard, deeper than in a movie theater (on certain songs). And it didn't boom one single bit.

I think one of MJK's "discoveries" is that inexpensive drivers can outperform expensive ones, in the right application. Of course neither of these are expensive. I'm sure either one will make more bass than a 4" (ha ha).

 

[serenechaos]

What do you mean by "deep?"
Low?

Have you heard simple sealed boxes w/ LT?
like bag ends? e.g.: Bag End Infrasub-18
the pair i have are +/- 3dB to 8 Hz...

lower than that?

or something else?