Suitable midrange cone, for bandpass mid in Unity horn.

I'm looking for a midrange cone, up to 6.5"dia to fit into a Bandpass enclosure which will fire into an odd unity horn (odd because its being re-shaped to fit into a car, but its using the unity concept).

Basically (I think) I need a midrange driver with a relatively high Fs and low Qt, to work in a 4th order bandpass (sealed rear chamber and ported front) and give me a lower cut off of about 200Hz and upper cut of of 1400Hz (-6db) if I can get more bandwidth all the better.

I'd like to go for a single 6.5" driver or smaller, multiple 2" or 3" drivers would be quite acceptable. I would ideally like something that is available in the UK though, importing from the states is an option but something easily available would be prefered. Someone is having reasonable success with multiple AuraSound NS2 'Whisper' drivers, I'm looking at the Eminence Alpha6 as they are cheap and easily available. any other suggestions please?
 
Greets!

To get 'in the ballpark', find one that either is a closed back unit that resonates at ~SQRT(200*1400) = ~529 Hz, or if open back, then ~529 = 2*Fs/Qes. How you get there doesn't matter if you're not trying to get max efficiency out of it with 'X' diameter x 'Y' long vents. IIRC, TD's prototype driver's published specs were ~2*250 Hz/0.99 = 505 Hz, so I wouldn't get too hung up on the apparent need for a low Qt just because it's a horn app.

GM
 
Re: Re: Suitable midrange cone, for bandpass mid in Unity horn.

I'm the guy with the Unity Waveguides in my car, as mentioned above.

GM, I had no idea that there was a formula for this! Thanks for posting it. Honestly, I've spent HOURS poring over the Madisound catalog looking for the best candidate. I purchased and measured half a dozen.

Using the measured data from my Unity midranges, here is what we get.

Aurasound Whisper Suitability for bandpass midrange:
2 x fs / qes =
2 x 164hz / 0.85 =
328hz / 0.85 =
386hz


And here's the measured response of my bandpass midranges, in a real enclosure. As you can see, the bandpass is centered at 380hz, with F3 points at 180hz and 650hz.

In other words, your formula is right on the money! Wish I'd known this three months ago :p

:: PB ::

An externally hosted image should be here but it was not working when we last tested it.

measured response of my mids
 
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Re: pioneer mid...

moray james said:
the pioneer mid (4 inch with a cup) #B11EC80-02F 8 ohms will work in this application. They cost about $25.00 US each. Worth buying one to test out. Regards.

Moray,

I took a few minutes to evaluate the Pioneer versus the Aurasound Whisper. Here are my thoughts:

The Aurasound resonates a bit higher, and will extend higher than the Pioneer. (386hz vs 325hz.)
The Pioneer will be waaaaay louder. It's sensitivity is dramatically higher.
The Aurasound measures flatter.
The Aurasound has a higher xmax.


While the Pioneer gives you more "bang for the buck", the data suggest that the Aurasound is a marginally better choice. But they're close, for sure.
 
Damn, forgot about this thread,

I've gone and bought some Visaton FRS 7 drivers, Fs of 251 and Qes of 2.08

so 2*Fs/Qes = 241

Hmm somewhat low.

So is their any parameter in particular I should be looking for that would suggest I will get a nice wide bandwidth from the bandass enclosure?
 

GM

Member
Joined 2003
Re: Re: Re: Suitable midrange cone, for bandpass mid in Unity horn.

Patrick Bateman said:


I'm the guy with the Unity Waveguides in my car, as mentioned above.

GM, I had no idea that there was a formula for this! Thanks for posting it.

In other words, your formula is right on the money! Wish I'd known this three months ago

Greets!

Yes, I've been following your car audio odyssey. Mine peaked in the early '70s when I modded my then wife's '70-1/2 Camaro with four channel horn loaded surround sound and piped in Altec 411-8A BP sub in the trunk. AFAIK it was the first woofer to have a foam surround and 'high' Xmax, so consequently it was probably the first to suffer from foam rot due to the high pressure/heat of a relatively tiny cab and hot trunk.

You're welcome, it's horn design 101, so published all over the place in one form or another by numerous folks including TD, though normally Qts is used in lieu of Qes. Since I use ML's math, Qes is substituted. Frankly, I wondered why ya'll continued to ponder driver suitability in what seemed like a 'blind leading the blind' manner after I posted it.

GM
 

GM

Member
Joined 2003
Puggie said:
So is their any parameter in particular I should be looking for that would suggest I will get a nice wide bandwidth from the bandass enclosure?

Greets!

As the formula shows, the wider the BW required, the lower Qes must be for a given Fs, ergo for a given Qes the lower Fs must be, but there's still the thorny issue of cab Vb and vent trade-offs just like any vented alignment (especially for a Unity concept), so no simple answer comes to mind at the moment beyond Small's 'EBP' grossly general rule of driver selection where values under 50 suggest the use of a sealed alignment, over 100 suggest the use of a vented, and between 50-100 as adaptable for use in either type.

GM
 
So the 529 Hz value allows you to cross at which points? I want to cross my midrange from 160Hz/6db to 2,500Hz/6dB (or any where up to 6,400Hz, which probably isn't realistic). What value should I be shooting for?

I have 4 VIFA 10MD1908 that have parameters:

*L1: .48 mH
*Znom: 8 ohms
*Re: 5.20 ohms
*Frequency range: 300-8,000 Hz
*Fs: 190 Hz
*SPL: 88dB 2.83V/1m
*Vas: .02 cu. ft.
*Qms: 4.80
*Qes: 1.30
*Qts: 1.03
*Xmax: 1 mm

These Vifa's give me a 292.31Hz value, which is not close to the 529Hz value. However, would they be better for my application?
 
LOL, are you starting to see why both John Sheerin and myself had such a hard time finding an appropriate midrange? It's because an ideal midrange doesn't exist! ;)

So back to your question.

You want to go from 160hz to 6400hz in a bandpass. I know intuitively that it's impossible, but let's do the math anyways.

Here's the math:

Fb = SQRT (F1 x F2)
Fb = SQRT (160hz x 6400hz)
Fb = 1012hz

So you'd have to find a mid with a Fb of 1012hz that has enough excursion to go down to 160hz. Good luck with that!

Would you mind if I scaled down the expectations a bit? Your goal was to cover 5.5 octaves. Even with a direct radiator, that's tough. What if we pare it down to THREE octaves? How about 175hz to 1400hz?

Here's the math:

Fb = SQRT (F1 x F2)
Fb = SQRT (175hz x 1400hz)
Fb = 495hz

As you can see, once you scale down your expectations, there are a handful of candidates that will do the job. The Eminence line array midrange will fit this job, and so will the now-discontinued JBL 400gti. I've personally measured the JBL, and I have one of the Eminence drivers on order.

:: PB ::
 
Puggie has a couple threads going on the same basic topic, so I'll cross post my previous cross post. DJK over on AA dug this guy up. No previoius exposure/experience, but the numbers look perfect, or at least better than anything I've seen previously if they're being honest. Looks like loudspeakersplus.com is the distributer in NA, although they aren't listed on the site.

http://www.paacoustic.com/Product_D...oductID=WN-520N

The summary:
5.5" nominal frame
1.5" CCA coil
0.14mH
80W
173hz Fs
0.200 Qts
1.23L Vas
2mm overhang
cloth edge
paper cone
carbonfiber/kevlar dustcap
smooth on-axis to 4Khz
 
Thanks for the explaination. I just modeled my first 4th order bandpass enclosure in WINISD and I now understand that covering 5 octaves is pretty much impossible. I wanted to use my Aura monopole combined with the unity waveguide as the mid. Is it difficult to get a 2,000Hz+ low-pass with the unity? When I construct the waveguide, would I only need one throat from the (2-3) midrange ports (the throat where you have the BMS compression driver)?

Why do you take the FS of the driver instead of the FS of the enclosure? Trying to get a flat response with a bandpass enclosure is a daunting task. I know you are using passive crossovers but would I be fine using an active crossover with 7 adjustable points of eqing?
 
Doug,

Nice catch!

I just got off the phone with Loudspeakers Plus. I'm going to find out what quantity is needed to get these over here stateside. If I have to buy 20 or 50 and sell the rest, I'll do it.

I'll let everyone know how soon we can get it.

As I see it, the problem with the Unity midrange is that it's hard to find a small woofer with a huuuuge motor. I'm kind of a noob when it comes to motor design; but I think this is inherent to small woofers. Basically, if you put a big ferrite motor on tiny driver, the flux isn't concentrated into the gap. Of course it's not such a problem with large woofers, because the gap is much larger.

This could explain why the JBL GTI400, the Aurasound Whisper, and the P-Audio Winner are good candidates; they're all neo.

:: PB ::
 
omarmipi said:
Thanks for the explaination. I just modeled my first 4th order bandpass enclosure in WINISD and I now understand that covering 5 octaves is pretty much impossible. I wanted to use my Aura monopole combined with the unity waveguide as the mid. Is it difficult to get a 2,000Hz+ low-pass with the unity? When I construct the waveguide, would I only need one throat from the (2-3) midrange ports (the throat where you have the BMS compression driver)?

Why do you take the FS of the driver instead of the FS of the enclosure? Trying to get a flat response with a bandpass enclosure is a daunting task. I know you are using passive crossovers but would I be fine using an active crossover with 7 adjustable points of eqing?

What is your "aura monopole?" Do you mean to say that you're using an Aurasound woofer at the apex of the horn or waveguide?

:: PB ::
 
Patrick Bateman said:
Doug,

Nice catch!

I just got off the phone with Loudspeakers Plus. I'm going to find out what quantity is needed to get these over here stateside. If I have to buy 20 or 50 and sell the rest, I'll do it.

I'll let everyone know how soon we can get it.

As I see it, the problem with the Unity midrange is that it's hard to find a small woofer with a huuuuge motor. I'm kind of a noob when it comes to motor design; but I think this is inherent to small woofers. Basically, if you put a big ferrite motor on tiny driver, the flux isn't concentrated into the gap. Of course it's not such a problem with large woofers, because the gap is much larger.

This could explain why the JBL GTI400, the Aurasound Whisper, and the P-Audio Winner are good candidates; they're all neo.

:: PB ::

I think that you may be jumping to some wrong conclusions. Rather I believe that the problem lies in the specific application of the driver required to do this type of job. This is a very odd application and there is practly no demand for a driver with these caracteristics so few are made. I really think that is the simple answer.
To say that big ceramic magnets on a small driver cannot be made to keep the flux concentrated in the gap is fiction the motot structure and magnet is not to blame. Flux is flux no matter if the source is a ceramic or a neo magnet. How much flux from the magnet that you can concenrate into the gap is dependant upon the size of the top plate and the geometry of the motor structure. Once you saturate the top plate and or the pole piece then you have hit you max flux. The answer is more and better quality iron for you motor parts. I think it is just that simple. Regards Moray James.
 
Patrick Bateman said:

What is your "aura monopole?"
:: PB ::

No it is a transducer that Aurasound use to make. I believe they bought the technology from Raido Shack as it is similar to the linaeum dipoles that they had in the LX-5 and some other loudspeakers.

Here is the pdf:
http://www.aurasound.com/pdf/ntl25-354-4a.pdf

So are drivers with large motors good, bad, or indifferent for this application. I am still confussed as to what specs the midrange enclosures are suppose to have.

Awesome! I got a value of 491Hz with the Audax HM100C0 drivers that I am currently using. I am not sure if the 54Hz Fs matters though. The motor on this thing is freakishly large too.

I just modeled it in WINISD and it has a super flat response compaired to the Vifa that I just modeled.
Vf = 0.6L, Vr = 0.6L, Tuning Freq. = 183.67Hz.
 
moray james said:
To say that big ceramic magnets on a small driver cannot be made to keep the flux concentrated in the gap is fiction the motot structure and magnet is not to blame. Flux is flux no matter if the source is a ceramic or a neo magnet. How much flux from the magnet that you can concenrate into the gap is dependant upon the size of the top plate and the geometry of the motor structure. Once you saturate the top plate and or the pole piece then you have hit you max flux. The answer is more and better quality iron for you motor parts. I think it is just that simple. Regards Moray James.

Moray, we're looking for a small woofer with a ridiculously powerful motor. Wouldn't a neo motor be better?


moray james said:
I think that you may be jumping to some wrong conclusions. Rather I believe that the problem lies in the specific application of the driver required to do this type of job. This is a very odd application and there is practly no demand for a driver with these caracteristics so few are made. I really think that is the simple answer.


Funny you say that. Once GM and Puggie clued me in to what parameters to look for, Unity midranges started falling out of the sky. I can literally name 5-10 now.

Do you know what 75% of them have in common? You guessed it, neo motors.
 
ceramic 0r neo...

the advantage that a neo will have is strictly physical they are smaller for a given strength. If you have ever played with any of the small full range driver that Fostex make the magnet is only marginally smaller than the cutout for the driver. That simply means that if you wanted more flux with a ceramic you would have to start stacking magnet slugs. So yes neo magnets would be easier to work with and lighter. That does not mean that they are better in terms of the flux they provide. They simply present a way to shrink your physical magnet size as compared to ceramics. You would be surprised to see what kind of increases in flux density are possible with top quality ceramic slugs (there are a number of grades available) when combined wit computer designed geometries top quality iron and super tight tolerences in build/ Today neo magnets are available at better prices than ever before so yes they are worth taking advantage of. This will result in a more reliable driver as big motors on the back of tiny frames have a habbit of being easily knocked off due to the small area availabe to secure the magnet.
Ok so you have found a dozen candidates that's good and I look forward to seeing the list. This is still a tiny number in the grand sceme of things. This is not your normal run of the mill mid driver. As you can see I have not disagreed that neo is nice for all the stated reasons I only wanted to point out that they do not make any better flux than would a ceramic magnet. No magic. Regards Moray James.
 
Patrick Bateman said:
Doug,

Nice catch!

I just got off the phone with Loudspeakers Plus. I'm going to find out what quantity is needed to get these over here stateside. If I have to buy 20 or 50 and sell the rest, I'll do it.

I'll let everyone know how soon we can get it.

As I see it, the problem with the Unity midrange is that it's hard to find a small woofer with a huuuuge motor. I'm kind of a noob when it comes to motor design; but I think this is inherent to small woofers. Basically, if you put a big ferrite motor on tiny driver, the flux isn't concentrated into the gap. Of course it's not such a problem with large woofers, because the gap is much larger.

This could explain why the JBL GTI400, the Aurasound Whisper, and the P-Audio Winner are good candidates; they're all neo.

:: PB ::

Get prices I'm interested! another option would be www.bandor.co.uk, if you want really tiny drivers I could source some neo magnets and have Doreen build us a run of Bandor 50s with neo motors, but just replace the ceramic with say N40 neo keeping the physical magnet dimentions the same (I think we would be looking at about £50sterling per driver).

I like GM's analogy on carsound, speakers are similar to cars, fast ones are generally expensive and I guess fast small ones as standard are quite rare!!