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I`m new to horn speakers and would appreciate your comments on a project i have been thinking about. I´ll give a brief description, please feel free to suggest changes.I want to build a front horn with the fostex FF85k from 250 Hz up to the point it needs a supertweeter (I hope to get up to around 8kHz), however I have not seen any such application and I wonder if this drive would work well on this application. As a side note I need moderate output and my listening room is about 18m2. As for the supertweeter I will use a ribbon in a waveguide.
I have been playing around with Martin j King´s model to calculate the horn. Does the model correlate well with measured data? What is the most accurate model available? As for the expansion I probably go with a tractix. King´s model shows choosing a relatively bigger throat vastly improves impulse response, and I think I would trade some dB for a cleaner response. The low frequency response would be taken care of either with a BLH with a lowish qts, or with big W-frame dipoles.
Follow Ups:
You may want to look at the slightly larger FF125 if you are going to horn load - more magnet and plenty of bandwidth for your needs. I don't see how the FF85 would need a tweeter.
Whitch front horn for the fostex? The ff85 might not be the best choice and matching a ribbons radiation patern to a horns doesnt work out so well. Ribbons output drops fast with distance horns not so much.Never could get the match rt when I tried ribbons do match BLH with fullranges but not oris or azura type front horns.
Greets!Between its ~high Qes, low eff./power handling, it's not a particularly good candidate for a FLH. WG (conical), yes, in a low average SPL app. A ribbon's polar response isn't conducive to mating well with a single driver horn and a WG isn't going to change it enough.
MJK's program is good for what it is, but unless you know what to expect in the real world it can be even more misleading than Hornresp since it tries to predict the driver's on axis response above the horn's HF cutoff. AFAIK, all programs assume a rigid flat piston and very low power, so can't take into account the horn's loading affect on the driver's TL properties in a typical app, so what looks good in a sim may cause different types of audible distortion and even damage the driver, particularly relatively flimsy 'FR' drivers, and why Tractrix or WGs are the preferred choices.
GM
Hallo GM,I really appreciate your help and I know you know what you are talking about. I will begin to search for another driver, I would prefer to use a direct radiating small driver, but what the hell, iI can open myself to things I havent considerd before! In adittion to the criteria to use the small driver I mentioned before, I am striving at (here comes the same ´ol story again) covering the "critical" range with one driver. As far as I know compression drivers that achieve this (ie go that low) are either way too expensive for me or too compromised. That`s why I looked into small direct radiators. The higher qts of the ff85k and the less "tilted" FR are points I was aware of, I didn`t think of the low sensitivity as a problem. As I said, my aim is to have the dynamics of a larger driver in the lower mids with a small driver in a horn, with the additional benefit of a more controlled radiation pattern (with the eventual "tradeoff" of having to equalize the upper response digitally with a Behringer) . Can you suggest me better/good candidates?
Regarding MJK model and Honresponse I read your comment as saying direct experience and trial/error is the only way to go. Where would you suggest me to start?
Greets!You're welcome!
Hmm, not aware of any compression drivers that cover this BW and compromised in any substantive way, but you're right, they're not particularly cheap.
Higher Qts drivers don't leave any BW of note for horn action and for this driver it needs around a 100 Hz horn to make it worthwhile. Then there's the problem of the driver's dynamic headroom in the critical mids being very low, so all things considered, the FF85K is much better suited for BLH loading.
WRT having an 8 kHz Fh, this ideally means an effective diameter no greater than ~0.75", so either the driver has to be very lightly loaded to keep its TL properties intact or rely on a whizzer cone. Not being a fan of horn loading drivers with whizzers when a super tweeter is used, the aforementioned FE126E looks good on paper.
Right, unless you get lucky, horn programs will quickly lead you astray when designing 'FR' driver horns, especially front loaded ones. Just for giggles, I did a RadioShack 40-1271 40 Hz FLH MathCad sim using Leach's math. This driver is 8" diameter with a ~83 Hz Fs, 2.446 Qts! and 90 dB eff.. It has a flimsy curvilinear diaphragm with whizzer to give it solid response out to 20 kHz. Now everything about this driver shouts that it's about as bad a candidate for horn loading as can be realized, yet the sim says its +/- 1 dB half space flat from ~36 Hz to ~175 Hz, rising to ~104 dB out to ~410 Hz where it rolls back down to ~98 dB/610 Hz before rolling off at ~36 dB.
Yeah, right. Even at very low power, the compression would keep the diaphragm from moving properly, so the little 1" VC would cook trying to flex just the immediate area around it when asked to reproduce any BW below Fs, and even if it didn't, it would roll off on both ends much sooner than predicted.
GM
Kloss,I will be making the horn myself. Why do you think the ff85k might not be the "best" driver? Is there a small driver that you could recommend above this one?There was a measurement from the german mag. Hobby-Hifi which shows a FR of the ff85k that climbs quite a bit more that the response graph available from Fostex. I`m not sure that the measured response is correct, but if it is, the climbing response coud be a plus when putting the driver into the horn. What I am aimig at is basicly to use a small driver (nice midrange) with the dynamics of a larger driver on the lower mid range trough the use of a horn. I really dont care if I have to compensate things digitally with a Behringer rig.
Did you put the ribbon on a horn/waveguide? This is how I plan to use, so that I can match the directivity at the crossover point (or perhaps use a little wider dir. on the tweeter). I would really like to know if you tried this with your 208S horns. As I side note, the system will be triamped.
Of primary importance are suggestions as to the math model to use.
I have used ff85k in a pair of 1907 edison triumph front horns they sounded pretty good didnt have a great deal of output driver gives a bit more hi frequincy in a front horn.Tried driver in fostex cabs its just ok like a good computer speaker system.If you could upsize to a fe126e think about $6. more for a pair you would get a better sounding front horn its a better sounding driver.And since you are using a tweeter fe126e would match.Most hi eff ribbons have a wave guide built in and adding anything extra doesnt help much in my opinion YMMV.I tried a wooden one on my raven r2 when run with dual lowther pm4a it only sounded good in near field when I moved about the high fequincy fell apart or greatly reduced in level with distance. Maybe a ft17h with fe126e would be close if fe126e was in a front horn.Remember just because you horn load it you cant turn a turd into a gold brick.Best to start with driver worthy. Unless your doing a budget system then I say go for it might be a good idea.But you said triamp so maybe not a affordable system??
Kloss,Nice to see you´re gone the same way. I have some experience with the fe126e (in a simple BR box), as although I like it I thought the ff85k could be better. So the point is taken, the 85 is not the driver. The JBL le-5 is one driver that is reported to work well on a mid FH. Is the 126 the best fostex candidate in your opinion?
I have read different opinions on the ft17h, Ill be trying to find information about it and other non-ribbon tweeters.
I will triamping with chip amps, the expense there is not a very big one. Later on I might get into a tube amp proyect for the mids. The budget is limited, but I am willing to spend as much as I can to build a system that does not get me wanting to build another one right after finishing it :-) regarding the mids I see them as the heart of the LS system so I would not try to save a few bucks there; lets say the budget is up to around USD 150 /each.
Thanks again.
Thanks too to Ronnie as well as to all others that have posted so far.
The FE108(E?) is similar, in size and T/S, to FE126E. A bit more $.I remember someone reported good results with them in front horns. It's in the archives.
Yep I'm using them in front horns down to about 300Hz. Was thinking (like you) of using the FF85K for exactly the same reason (high Qts, but rising response might work out OK). 108ES is good, you may be able to pick up a pair second-hand cheap, as Ed Schilling's Hornshoppe customers are upgrading from the 108ES. I'm using a FT17 to augment the highs.
Did you do any measurements on the Fostex/Horn combo?
Curious to hear about the HF roll-off and if there were any spikes in the response.I want to do that with my horns, but haven't got the gear yet.
yep got some measurements with a (borrowed) TacT EQ but lost 'em. Did some measurements with a RS dB meter and warble tones, looks pretty flat thru midrange with some ripples at lower end near 400Hz. Funny thing is I get best/flattest response running out-of-phase w/ woofer, must do some more experiments. Might be able to get some more measurements with the TacT soonish. Top end lacks a bit of "air" without tweeters due to loading of waveguide. Currently running 0.9uF cap to FT17H tweeters. Tweeters are mounted in same plane as 108ES, to the outside, and "shaded" by horn so boosting ambient HF more than direct.Hope this helps!
Don't know if that helps.. but my curiousity is stilled and you inspired me to steal my cousins TacT.I'd like to see the results if you make any more measurements.
I'm using the FE126E in "250Hz tractrix" front horns, but with only 28.5cm depth.
...I'm getting them ready for painting tonight, so I just have to say something!I think they sound... good. I like the HF, and have no idea how high they go.
I haven't done any measurements.
I _believe_ they are more suited for horn loading than the FF85K. Compare the T/S parameters!
A full size tractrix 250Hz horn for the 3" FF85K driver would become very deep, which may or may not screw up the sound...
I really recommend covering the back of the drivers. I'm using underwear that I got for Christmas for the job, but a real back chamber might be even better.
They are crossed over to at 1750Hz or something, 1st order. I'm planning smaller horns with compression drivers, since I believe that might be much more suitable since the XO point is so high anyway.
Have fun! :)
on your horn system. How big are the larger horns and at what frequency do you cross them at? Do you use a sub? Thanks.
Inspired by Romys "Macondo" acoustic system, and I think I've posted most of the details in a thread on his site.Not quite as many LF boxes yet, and no Vitavox S2 ;-)
I'm a happy copycat :)
I happen to have a pair of S2 but I currently use them as "super tweeters." They blow the pants off Fostex supertweeters that I used to use.Your configuration looks similar to Avant Garde Duos, less the "subs." IIRC, I think Duos cross at around 150Hz or so to the midrange horn.
Just curious about integration compared to Edgarhorn crossover points. I'll post an iquiry....
Link? I tried to post, but I suppose someone here is not at peace with the idea of links to his site. :)
I suggest Google!Oh.. and there were tiny LF boxes in those photos. Probably not even visible. Now, I'm building four (to begin with) sealed boxes with Scan-Speak 25W/8565-00.
Yes. I'm curious about the Avantgardes! Haven't heard any yet.
It also makes me curious that S2 is only supertweeting for you! What are you using below them?
...my reply was deleted...Anyway, I run JBL 2441 in RCA Fan's 700Hz conical horns, then to JBL 2226 in RCA Fan's half horn. I use S2 with a single .47 cap with attenuator, which breathes life into the system.
I think my system needs a midhorn. Hence my query.
Your larger horn looks like it is made out of concrete(?)! I think that the advantage of running a 150Hz horn is greater midrange clarity. This is where the Duos have it over the Edgarhorns. However, the Duos have problematic bass integration. I don't think that the Duos subs are any good as I can hear the transition. And this is where the Edgarhorn beats it.
An array of sealed woofer boxes is an innovative way of matching the speed of the midhorn.
There's lots of info about those systems, and the issues you raise, over there.Yes. It is concrete, and a thinner layer of gypsum. There certainly are less resonant materials, but those are common and available.
I'll post some more as the system progresses. Coming up are more boxes and Altec 902 in smaller horns.
Please show off your mid horn solution when you get there! :)
A tractrix would be a good choice for that frequency range (basically above 100Hz), although I have no experience with the particular driver you mentioned. As far as tractrix midrange horns, the guys on the Klipsch forum who use 'em seem to love 'em.
in a situation where a 20cm fullrange with wizzer and finite power response is firing down a waveguide whose throat is ~Sd? - -is the sweet spot about "what one sees is what one gets"? are highest F basically at direct radiator level or somewhat higher?
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