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Old 27th January 2005, 12:41 PM   #1
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Default driver recommendations for front horn ?

I would very much appreciate recommendations (and education as to why !) about choice of driver for a straight (probably tractrix ?) front horn that goes down from HF to ~ 150 Hz, below which an active crossover will cut to a "conventional" sub.

The obvious benchmark, the "Oris", uses Lowther, but since Bert Doppenberg sells Lowthers, I have to consider that is maybe a biased view. I would esp. appreciate independent opinions.

(My horn will most likely be made of 12 or 16 wood "petals" bent in only one dimension, 78 clockwork gramophone style, it sadly wont be perfectly circular as the Oris is due to construction practicalities !) Also it will probably be somewhat longer, having a less aggressive flare.

Most post / articles (including Berts) discuss "using this driver in that enclosure" - but skip how that design choice was made. I would appreciate explainations of what to consider (eg x-max, diaphram diameter, particular TS params etc that are esp. applicable in this application, as well as personal opinions about the relative merits and value of Fostex vs. Lowther drivers.

Oversimplifiying, from reading diverse posts etc I get the impression selection of lowthers seems mostly down to magnet alternatives (?!) . Stronger flux = better damping, OK I buy that. But for Fostex the driver choices seem much wider. Why or when should I choose eg a 168E sigma instead of a 207E or whatever ?!?!?!

At the HF end I have read enough to understand there is unlimited scope for experimentation with different phase plugs, AER cones etc .. it all rather daugnting or a newbe. I am rather worried ater reading too many tales of "I did this, then I changed that, then that, then that, then these drivers, then .... I cant afford to rebuy everything three times

I have also read that new lowthers are too bright and steading loose brightness with use ... ? .. which worries me. OK I understand about "playing in" but I would like to think that these things settle down to a stable sound, not simply one that just steadily gets duller and duller with use .. comments on this also appreciated !

Intended drive for the horns will of course be no-feedback tubes, so damping factors will only be modest at best, so I feel only limited need to go for overkill magnets (or ? .. )

but tube amp design starts to see simple and "science" (yeah, right) compared to horn speakers. Or is that just because this is my first outing into horn speakers ?. To date my speakers have been from the other extreme, linefficient and complex (Quad ELS 57 / Apogee Scintilla "full range (= 3 way) ribbons (87dB and 1 ohm !), Canton digital 1.1's (BIG conventional 3 way boxes). ie bigger amps, but still no-feedback. I als ohave a (water cooled !) Pass Son of Zen.

help ?! .. Thanx !
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Old 28th January 2005, 12:25 AM   #2
GM is offline GM  United States
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>driver recommendations for front horn ?
I would very much appreciate recommendations (and education as to why !) about choice of driver for a straight (probably tractrix ?) front horn that goes down from HF to ~ 150 Hz, below which an active crossover will cut to a "conventional" sub.
====
Hmm, any driver can be horn loaded, it's just a matter of matching the horn to the driver's specs, which choices are dictated by your performance goals/budget, playback system, room, available space, and SAF parameters.
====
>The obvious benchmark, the "Oris", uses Lowther, but since Bert Doppenberg sells Lowthers, I have to consider that is maybe a biased view. I would esp. appreciate independent opinions.
====
Well, it's certainly a good system, but it's only good for you if it meets the needs of your app. I prefer compression loaded horns to 'fullrange' driver ones such as the Oris, but then I have a semi-large/open room.
====
>Most post / articles (including Berts) discuss "using this driver in that enclosure" - but skip how that design choice was made. I would appreciate explainations of what to consider (eg x-max, diaphram diameter, particular TS params etc that are esp. applicable in this application, as well as personal opinions about the relative merits and value of Fostex vs. Lowther drivers.

>Oversimplifiying, from reading diverse posts etc I get the impression selection of lowthers seems mostly down to magnet alternatives (?!) . Stronger flux = better damping, OK I buy that. But for Fostex the driver choices seem much wider. Why or when should I choose eg a 168E sigma instead of a 207E or whatever ?!?!?!

>Intended drive for the horns will of course be no-feedback tubes, so damping factors will only be modest at best, so I feel only limited need to go for overkill magnets (or ? .. )
====
In general, the larger the driver, the lower the usable Fc due to increased acoustic efficiency and the shorter/larger the horn if it's not truncated like a Tractrix or many of the old theater midbass horns. Horns only need a BW sufficient to cover up to the driver's mass corner ((Fs/Qts)*2), so if tube driven then a low Q driver is required to allow for its output impedance increasing the effective Qts, ergo a higher Qts driver can be used when SS driven. Or you can add some series resistance if you prefer to use a low Q driver.

My exposure to Fostex drivers is limited, but of the ones I've auditioned, about all I can say is that WRT the Lowther you get what you pay for WRT sound SQ, though I have to wonder how the AER can be enough better to justify its pricetag. Frankly, for much less $$ I prefer using duplex (horn loaded co-axials) to the high $$ FR drivers, but then I'm big on being able to ~reproduce the dynamics of a live event.
====
>At the HF end I have read enough to understand there is unlimited scope for experimentation with different phase plugs, AER cones etc .. it all rather daugnting or a newbe. I am rather worried ater reading too many tales of "I did this, then I changed that, then that, then that, then these drivers, then .... I cant afford to rebuy everything three times
====
Then maybe DIY horns aren't for you if you can't afford the best from the get-go.
====
>I have also read that new lowthers are too bright and steading loose brightness with use ... ? .. which worries me. OK I understand about "playing in" but I would like to think that these things settle down to a stable sound, not simply one that just steadily gets duller and duller with use .. comments on this also appreciated !
====
For whatever reason they are made inordinately stiff, ergo take some time to loosen up, so need to be broken in by clamping them face-face and fed an out-of-phase wide BW signal that pushes them to Xmax. Don't know how long it will take though, most drivers are ready within 24hrs. If you mount them in a horn and use music it will take seemingly forever, 500hrs is an oft quoted time frame. Note that historically they have notoriously poor QA, so if you choose them, buy from someone who will check/match them before shipment and won't hassle you if there's any problems during the warranty period.
====
>but tube amp design starts to see simple and "science" (yeah, right) compared to horn speakers. Or is that just because this is my first outing into horn speakers ?.
====
For all their seeming complexity, horns are fairly simple boxes once you understand how sound is propogated, and there's plenty of published 'science' to define them. I equate them to pro race car 'rollers' (the racer, less drivetrain) in that they are a highly adjustable design that allows you to optimize their performance for the various intended apps, whereas the electronics/drivers are like its drivetrain, which are built to a set of specs that vary for only a few groups, such as NASCAR Vs NASCAR restrictor plate motor specs.

Viewed from this perspective, it becomes transparent why horn designers tend to be like a race car designer or team in that they don't want to divulge any more of their design/set-up 'secrets' than absolutely necessary.

GM
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Old 28th January 2005, 05:00 AM   #3
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I don't know how much help this will be, but www.madisound.com have some little full range drivers on sale really cheap, Aura NS3-194-8E. Their Qts is low making them ideal for your application, but their sensitivity isn't that great (89dB I think). Still, it's a cheap place to start and they ship to the UK fairly cheaply, and your horns will pull the sensitivity up plenty. I am going for some Fostex drivers from them I think.

Unless you know anywhere in the UK to get fostex drivers?

Alternatively, try www.cpc.co.uk. They have lots of cheap drivers to have a play with if you don't want to commit to expensive drivers just yet. You can experiment with them to get an idea of how different horn shapes will effect the range of a driver.

Good luck on your project and keep us posted on your results!
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Old 28th January 2005, 09:57 AM   #4
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Thanks both for taking the time to reply. I pick up a couple of points ..

Quote:
Originally posted by GM

Hmm, any driver can be horn loaded .. but it's only good for you if it meets the needs of your app. I prefer compression loaded horns to 'fullrange' driver ones such as the Oris, but then I have a semi-large/open room.


====
>Most post / articles (including Berts) discuss "using this driver in that enclosure" - but skip how that design choice was made. I would appreciate explainations of what to consider (eg x-max, diaphram diameter, particular TS params etc that are esp. applicable in this application, as well as personal opinions about the relative merits and value of Fostex vs. Lowther drivers.

>Oversimplifiying, from reading diverse posts etc I get the impression selection of lowthers seems mostly down to magnet alternatives (?!) . Stronger flux = better damping, OK I buy that. But for Fostex the driver choices seem much wider. Why or when should I choose eg a 168E sigma instead of a 207E or whatever ?!?!?!

>Intended drive for the horns will of course be no-feedback tubes, so damping factors will only be modest at best, so I feel only limited need to go for overkill magnets (or ? .. )
====
In general, the larger the driver, the lower the usable Fc due to increased acoustic efficiency and the shorter/larger the horn if it's not truncated like a Tractrix or many of the old theater midbass horns. Horns only need a BW sufficient to cover up to the driver's mass corner ((Fs/Qts)*2), so if tube driven then a low Q driver is required to allow for its output impedance increasing the effective Qts, ergo a higher Qts driver can be used when SS driven. Or you can add some series resistance if you prefer to use a low Q driver.

My exposure to Fostex drivers is limited, but of the ones I've auditioned, about all I can say is that WRT the Lowther you get what you pay for WRT sound SQ, though I have to wonder how the AER can be enough better to justify its pricetag. Frankly, for much less $$ I prefer using duplex (horn loaded co-axials) to the high $$ FR drivers, but then I'm big on being able to ~reproduce the dynamics of a live event.
====
>At the HF end I have read enough to understand there is unlimited scope for experimentation with different phase plugs, AER cones etc .. it all rather daugnting or a newbe. I am rather worried ater reading too many tales of "I did this, then I changed that, then that, then that, then these drivers, then .... I cant afford to rebuy everything three times
====
Then maybe DIY horns aren't for you if you can't afford the best from the get-go.
====
>I have also read that new lowthers are too bright and steading loose brightness with use ... ? .. which worries me. OK I understand about "playing in" but I would like to think that these things settle down to a stable sound, not simply one that just steadily gets duller and duller with use .. comments on this also appreciated !
====
For whatever reason they are made inordinately stiff, ergo take some time to loosen up, so need to be broken in by clamping them face-face and fed an out-of-phase wide BW signal that pushes them to Xmax. Don't know how long it will take though, most drivers are ready within 24hrs. If you mount them in a horn and use music it will take seemingly forever, 500hrs is an oft quoted time frame. Note that historically they have notoriously poor QA, so if you choose them, buy from someone who will check/match them before shipment and won't hassle you if there's any problems during the warranty period.
====
>but tube amp design starts to see simple and "science" (yeah, right) compared to horn speakers. Or is that just because this is my first outing into horn speakers ?.
====
For all their seeming complexity, horns are fairly simple boxes once you understand how sound is propogated, and there's plenty of published 'science' to define them. I equate them to pro race car 'rollers' (the racer, less drivetrain) in that they are a highly adjustable design that allows you to optimize their performance for the various intended apps, whereas the electronics/drivers are like its drivetrain, which are built to a set of specs that vary for only a few groups, such as NASCAR Vs NASCAR restrictor plate motor specs.

Viewed from this perspective, it becomes transparent why horn designers tend to be like a race car designer or team in that they don't want to divulge any more of their design/set-up 'secrets' than absolutely necessary.

GM [/B]

Quote:
Originally posted by bobhayes
I don't know how much help this will be, but www.madisound.com have some little full range drivers on sale really cheap, Aura NS3-194-8E. Their Qts is low making them ideal for your application, but their sensitivity isn't that great (89dB I think). Still, it's a cheap place to start and they ship to the UK fairly cheaply, and your horns will pull the sensitivity up plenty. I am going for some Fostex drivers from them I think.

Unless you know anywhere in the UK to get fostex drivers?

Alternatively, try www.cpc.co.uk. They have lots of cheap drivers to have a play with if you don't want to commit to expensive drivers just yet. You can experiment with them to get an idea of how different horn shapes will effect the range of a driver.

Good luck on your project and keep us posted on your results!
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Old 28th January 2005, 12:36 PM   #5
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Quote:
Originally posted by GM
Frankly, for much less $$ I prefer using duplex (horn loaded co-axials) to the high $$ FR drivers, but then I'm big on being able to ~reproduce the dynamics of a live event.
This is an area I've been thinking about for some time. I've been keen on the idea od a set of Azura's with something like a PHL coax driver with a Beyma 1". Have you built something similar, and do you have any driver / flare recommendations?
I currently use BMS 4590 coax compression drivers.
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Old 28th January 2005, 12:46 PM   #6
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Default please skip previous post - submitted in error ! - retry here.

Many thanks to you both for taking the time to reply. i pick up just a couple of points

[QUOTE]Originally posted by GM

Hmm, any driver can be horn loaded .. but it's only good for you if it meets the needs of your app. I prefer compression loaded horns to 'fullrange' driver ones such as the Oris, but then I have a semi-large/open room...Frankly, for much less $$ I prefer using duplex (horn loaded co-axials) to the high $$ FR drivers, but then I'm big on being able to ~reproduce the dynamics of a live event.

- I would describe my design process as the other way around : I have decided that on this occasion I wish to make a full range horn (OK, down to 150Hz) using a full range driver. My problem is now to select the best driver for this application. I may some day decide to make a compression horn or use co-axials. And maybe that will be better. But thats not what I am trying to do now. In the same way, I have made DH-SET's, PP amps using 807's, KT-88's & even 813's. and even water cooled MOSFET amps. I like to experiment

- but as a curiosity, please can you explain why a co-axial can reproduce *dynamics* better than a full range ? I can see that a co-axial makes the design & production compromises simpler in some ways since the BW of the component sections is reduced, and this might eg affect efficiency etc. But how are the dynamics affected ?


====
.... I cant afford to rebuy everything three times
====
Then maybe DIY horns aren't for you if you can't afford the best from the get-go

- to be clear, I can (and prefer) to buy the best from the get go. what I seek to avoid is wasting money buying thewrong thing at the get go and then having to buy something else, then something else, and "progressing" more or less by trial and error. Horns have been around a long time and as you noted elsewhere in your reply there is a lot of science around now : I would prefer to stand on the shoulders of giants and do it more or less right first time. I am *not* aiming or claiming to be advancing the state of the art ! .. I just want to make a horn to listen to (and then I can maybe make some flea powered amps and experiment with them too, which today isnt an option with the speakers I have.)

Note that historically they have notoriously poor QA, so if you choose them, buy from someone who will check/match them before shipment and won't hassle you if there's any problems during the warranty period.

- this is well worth knowing, many thanks indeed. Since 2nd user lowthers are pricey anyway this encourages me to do what I would prefer anyway, ie buy new ..



[QUOTE]Originally posted by bobhayes
[B]I don't know how much help this will be, but www.madisound.com have some little full range drivers on sale really cheap, Aura NS3-194-8E.

Alternatively, try www.cpc.co.uk. They have lots of cheap drivers to have a play with if you don't want to commit to expensive drivers just yet. You can experiment with them to get an idea of how different horn shapes will effect the range of a driver.

- will check these out, many thanks, but we are back on this issue of relative quality. cheaper drivers being less efficient isnt a big issue for me (I have lots of powerful amps) but sound quality is. If I am going to invest time as much as money making some horns, I would prefer to get a "good" driver (for selected values of "good") first time out, especially as the horn has to be optimised to match a specific driver. How much sound quality do I loose getting the cheaper driver ? Some say "you get what you pay for" and that may be true inside eg the lowther range, but how does the lowther range compare to an Aura, Fostex or whatever ? Is more expensiive = better, or simply overpriced to some degree ? If the price difference is large and the sound difference small, then I will of course probably select the cheaper unit for "experiments", but if cheap drivers sound bad, I feel Im kind of wasting my time ? Full range drivers are "on paper" the most demanding design challenge of all because of the problems of providing the BW. I expect to have to pay a reasonable some for a good one - if good ones were cheap, why has the mainstream gone so overwhelmingly multi driver ?!
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Old 28th January 2005, 12:46 PM   #7
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[QUOTE]Originally posted by bobhayes

Alternatively, try www.cpc.co.uk. They have lots of cheap drivers to have a play with

- FYI, This URL is no longer available, but I hit them at http://cpc.farnell.com
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Old 28th January 2005, 05:33 PM   #8
Greg B is offline Greg B  United States
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All the fostex drivers sound different. The better ones have notably better build quality. They usually sound better as well. The sigmas and FXxxx/Fxxxa series have nice cast frames and JBL-esque quality. The FExx3/6/7 have cheap stamped frames. The FF series have very heavy stamped frames and are somewhere in between.

AFA which one to pick, it depends on your goals and system design, budget, etc.
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Old 28th January 2005, 07:34 PM   #9
ScottG is offline ScottG  United States
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You really need to hear what a good front horn is like B4 proceeding down this "path". Controlled dispersion has its own sound that you may or may not like.

As for getting down to 150 Hz you are stuck with either a full range driver with a rising response front horn loaded OR a Unity configuration. Even the best of the coaxials don't go this low, (usually to 300 Hz). Making your own GOOD front horn isn't trivial. Finding a good front horn with driver combination isn't trivial either.

Since your experimenting with amps consider going active with a behringer digital eq. (something you could always modify for better perfomance). This will allow you a great deal of flexibility with respect to drivers, enclosures, etc.. If you do this I'd suggest a BMS 4540ND with a McCauley 6326cx or a PHL1520, then choose a compliment of bass drivers that you prefer in an enclosure of your choosing. (I'm partial to the idea of a T-Line for a Beyma LX60.)
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Old 29th January 2005, 07:59 PM   #10
GM is offline GM  United States
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Quote:
I've been keen on the idea od a set of Azura's with something like a PHL coax driver with a Beyma 1". Have you built something similar, and do you have any driver / flare recommendations?
Yes, though it was long ago using various brands no longer made, and even then I 'cheated' by using either the Altec A7 or larger A4 cinema horn flares. Regardless, I found that I wasn't that keen on the A7's truncated (both ends) 110Hz expo horn once I'd heard them on the much larger A4's truncated (throat end only) 70Hz expo horn.

This led me to doing numerous mouth termination experiments, where I found it wasn't the extra BW so much as the reduced amount of mouth reflections, which needed to be further reduced by getting rid of the parallel sides if the XO point was >300Hz. In this respect, RCA's 'Ubangi' variant was considerably smoother since it's a radial design.

Anyway, all my various experiments led me to what is really an obvious conclusion if you think about it, i.e. that the least distorted horn profile is a round conic terminated with an acoustically large, rounded over flare. I haven't reverse engineered an Azura, but it's my understanding that it has a LeCleac'h flare, which is very similar to what I built when space wasn't a major issue, so it's what I recommend when a ready made one is desired. Otherwise I used expo with at least a 90deg termination if there wasn't space for an optimum design (all too often unfortunately).

GM
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