[stroop]

Hello everyone,

This is my first post on audiocircles. I have been reading here for quite some time about OB's! I got started by being interested in the Darkstars and then have tried to read everything I could.

Now, I have a question!

I remember JohninCR really liked the qualities of the fe108ez in OB. I was wondering if you could possibly share with me a little more of your experiences with them.

I have a pair and thought about trying them in OB. I know they are not ideal for this configuration and will need bass augmentation. I mainly wish to get an idea on where you would cross them over and if a pair 15'' woofers be too big when crossed at 200Hz?

Thankyou in advance and I thankyou all for sharing what you already have!

Stroop

[JohninCR]

Stroop,

A 15" will work, but not a subwoofer type 15.  I used the woofer of my Hawthorne coaxes as the augmenter, with just a first order filter starting somewhere around the 150hz, if I remember correctly.  Don't apply much power to those 108's, especially if you're running them full range.  Ideally, you'll want to filter the lows from reaching the 108's, and they'll sound even better.  I'm just finishing up some dipole waveguides for triple 108's per side.  They're big, but WOW.  Next week I'm going to try some smaller single 108 dipole waveguides, to see if I can get close to the same dynamics.  Even with no horn loading, the controlled dispersion makes for quite an increase in sensitivity.

[stroop]

Ah! Thank you so much!

I will be watching in interest what you do with them!

I'll do a search for that fe108ez project you got going. There are some 15 inch PA Speakers that I can get for about 50 euro....

Do they not like going too loud?

Stroop

[JohninCR]

Stroop,

I a well designed rear horn or front horn for that matter, a pair of 108's will go louder than my ears can handle in my 3.4mX6.4m room, but a good horn will control cone excursion.  In an open alignment, there's no back pressures to help control excursion.  The 108s have only a fraction of 1mm of excursion, so if you apply more than a watt or 2 of power and send a full range signal and moderate bass content, they easily go into overexcursion.  They're well built little drivers, but you don't want to risk damaging them.  They won't make any bass anyway in open air, so don't send it to them.  They'll sound better and be able to play louder too.

[nodiak]

stroop, I damaged the vc's in a pair of FE108ez's by using them fullrange on ob. I thought I was being careful, just testing for sound, turned it up juuusst a touch too much because it sounded so good. From my experience a cap bundle of 30-40uF is a good place to safely start your experiments to blend 108's to a bass driver. You may want the 108's to go lower ultimately but this a quick and safe start for a passive xo. Maybe add caps in 5-10 uF steps, and watch  the 108's excursion. Even still they probably need more than a 1st order xo. Google "Dick Ulsher Augies" for an article that may be a good example if you're going passive.
Careful with those little guys! Yes they are very nice sounding on ob. Their ~ 90db eff. made them able to blend with alot of different midbass and bass drivers.
Just a heads up.
Don

[stroop]

ooooh Ok! Thanks for that!

I would definately reduce the lower frequencies going to them if I'm going to do this!

Do you ever find the crossover at 150Hz audible? I 've just been mucking around with my BIB's to get rid of the dip at 140-200Hz. I found it disturbed cello's and violas a bit making them lack tone.

I've seen suggestions of putting a ribbon with the visaton b200. That looks quite interesting to me!

Stroop

[JANDG]

What amps ya running..? If your running tube amps the B200 & ribbons with bottom support to 150 is nice. With the G2 there is no need for padding. You might be able to use the g2si, which is much cheaper, but have read that it is close to the G2 for performance..If it is 96db eff.. also it would be worth a try..The combo I use is with a 100k input impendance tube amp for B200 & ribbon together is...022uf PIO PLLXO installed on the input of my 300B PP mounted externaly, I made them from a set of Eichman silvers I had. I use Vitamin Q..in that spot. Then put a foil air coil of .22mH in series with the B200, finally a single 2uf cap of your choice on the G2 ribbon..I use a high quality film cap.. I use BASH plates set at 150hz for my Vifa M26wr-09-08's mouted on same baffle, these Vifa's are not what one would think would work well for OB , but they do, for my smaller non square room, they have extreme quality in the 150hz down range..seemless............fast clean & tight.  perfect match.. just not thunderouse.. I run the off the 300B PP speaker outs to high level in on plates.. that works best IMO for these plates..You will not have the tilted responce & a sweet top end.. with no percieved hole in the top. You have to run the 1st order high pass PLLXO on the amp to do all this.. the ribbon will not like bieng ran with a single cap @ 2uf at higher volume if you don't..treble beam is gone on the B200 & midrange is much cleaner.. instruments & vocals still retain there dymanic peaks, but with real nice balance... female vocals of Linda Perry & Loreena McKennitt type will top out perfectly w/ sweetness without a pierce, just sweetly at the edge as they are capable of doing, but no peirce.. There are better drivers for bass augmentation than I use, & hust search & ask, these guys no what is good for the $.. The Vifa I use is also discontinued..I am using no EQ, no op-amps of any sort , even on my source which is op-amp free.. Also since you don't need resistors for padding the ribbon & none on the B200 also, the life doesn't get sucked out of the driver.. dynamics & micro dynamics even at low vlome are retained. So it would be close to what the total active people are doing with the driver in this reguard..I don't like the B200 or ribbons with resistors in play.. If you use the 108, you would probablly be better of running it alone with bass augmentation & no supertweeter if going passive because of having to pad the super tweeter, just PLLXO the amp so you don't pop it..It will play much louder & cleaner with a HP on the amp.. insertion loss is minimal with low order HP. I run a TVC with signal tapped directly off the DAC chip's I/V conversion, total output stage by-pass, & the insertion of the single Vitamin Q @ amp's input doesn't have much if any negs,,way more + than - lets say..simple & very effective..

[stroop]

Welllll...ahem amps... T-amps at the moment but will be a modular system of Ucd 180 or 400 specifically for active systems...soon-ish! There is a cheap but very good active crossover from Mr crypt in Conrad that I think I'll buy. 60 euro - designed by someone good and is perfectly symmetrical whatever that means, just for 4 channels I think. Then eventually PC or behringer EQ. If I do PC then I'll need it dedicated, because i only have a laptop. My lady would not take kindly to me taking it over!!!

There is alot for me to take in there!

I'm just looking forward to swapping stuff around and having a play!

Best regards

Stroop

[JohninCR]

As promised, my latest attempt with the 108's is shown in the directivity OB thread.  I keep inching toward the perfect speaker, at least for me anyway.