Best DIY combination? also posted in Tech questions...

[MikeMilliken]

Thanks for the Danley Link Mike........I have seen that driver partially down the line in order to smooth reponse in TL lines before, never thought about it for a horn. But a TL line is absorbtive down below a 3/8-5/8 wavelength of the line length, whereas a horn should be straight gain. So, I know that works fine when you are trying to lose backwave......And in a line it lowers the amplitude peaks( also frequency as a function of length "behind " the driver) that might not be fully damped

Seems like if would introduce cancellation/peaks from phase anomolies??? To me its almost "sleight of hand" Your thoughts? I only briefly looked at it though. If the "Grail" is in there I had not spotted it yet.

[MikeMilliken]

This is the sub I was talking about..........http://www.royaldevice.com/custom.htm

However I want to run mine from the inside of the building (above ground, got lotsa land) and U it back inside with a 10' x 20' throat termination. I wont use brick. I'll use concrete and I plan to follow a semi tractrix, mine will not only gain width but height as well.

The compression chanber confuses me........

Something else thats eating at me.........

Can ANYONE tell me why, you put a big woofer on a horn throat and then hook to a 3" wide opening. This certainly looks terribly constrictive! Is this PWK's way of making a very short (comparitively) horn work? The motor board's that are used on K Horns, Lascala's, Jub's, just look wrong to me. making that big woofer compress into a little rectangle............... If its done to get the short horn to work, I understand.

But I dont like the looks of it, and would have no idea what thats doing to the cone, loading wise

[Guest " "]

"Can ANYONE tell me why, you put a big woofer on a horn throat and then
hook to a 3" wide opening. This certainly looks terribly constrictive!
Is this PWK's way of making a very short (comparitively) horn work?
The motor board's that are used on K Horns, Lascala's, Jub's, just look
wrong to me. making that big woofer compress into a little
rectangle............... If its done to get the short horn to work, I
understand."

There a ka_zillions of threads on this fourm about this.......

The 3" opening vs the 6" opening discussions center around the bass boost the 3" opeing has vs the 6". There's an upper mid bass cost penalty.

Keep in mind the intended frequency range....the khorn is not a sub woofer horn

[Islander]

Can ANYONE tell me why, you put a big woofer on a horn throat and then hook to a 3" wide opening. This certainly looks terribly constrictive! Is this PWK's way of making a very short (comparitively) horn work?

I can't say for sure, but maybe it's to make a conventional cone woofer behave more like a compression driver, so its sound is closer in nature to the sound produced by the compression drivers of the squawker and tweeter.

[MikeMilliken]

Hi again Pat!

This is something I have noticed while playing with all kinds of horns. One commonality I keep seeing, is that the throat, right after the driver be it dome or cone, is constricted. Altecs, EV's, EAW, Community, and apparently the Klipsch designs......

I have to go did up my books on horn design...... Theres something going on right at the very start of the horn..

I think...... a horn (at its simplest) is no more than an acoustic transformer, and as such its function can be predicted.

I understand what happening at terminus (F3/FC) and I understand how/why you determine length vs area for the different trype of horns.

I also think (plz correct if I am going the wrong way, NEW TO HORNS!) that right at the point of coupling, must be VERY important.. I need to know whats happening there.. and how this acoustic coupling SHOULD take place, and why does it need to be compressed at that point. I think it is an acoustic impedance coupling, though I might be way off. No one seems to address that area of the horn where I think the SECRET to the horns efficiency lies.

Am I way off? I will dig out my books and see what Martin Colloms has to say about this. High Perf louspeakers has been my saviour many times when I got in a corner and couldn't figure my way out

Thanks all who have contributed !

[Coytee]

why does it need to be compressed at that point

I think it's to cause compression and that compression is what gives it a bit of mechanical leverage.

Poor analogy... try blowing through a straw...you will feel the backpressure of the straw preventing you from exhaling very hard. Now, swap out to a 1" PVC jammed into your mouth and blow through that... you will exhale very quickly. Straw gives you compression, perhaps too much and the 1" tube gives you no compression (or pressure to help build volume)

That's my take on it...as you can see by my analogy, I'm not very sophisticated in my understanding. I do however, blow a lot of hot air when talking.

[]

[Islander]

I'm only repeating what I've heard on this forum, but it seems that the horn designers want a small amount of air moving at high velocity at the throat of the horn, changing to a large amount of air moving at low velocity at the mouth of the horn. In that way it couples or "adapts" the small area of the driver's diaphagm or cone to the large area of the room.

The horn is a way for the driver to "get a grip" on the air in the room, so the driver becomes far more efficient. Accordingly, it needs much less travel or excursion, so its distortion goes way down as well.

[DrWho]

I never thought of reversing the phase
and trying to tune for minimum bass, thats pretty ingenius;)

Sadly
I can't take credit for that one....I picked it up from a Klipsch
engineer and then heard it from a few other sources so I didn't quote
it [A]

Ok , meat &
potatoes...Theres a couple things going on, My first BIG part of my
shop system will be the big bass horn, it wont be folded but once, and
then only because I'd like to use the backwave. So, my intention is to
make it do a U, you with me?

Are you talking a standard
rear-loaded horn or a tapped horn? With the goal of perfect
reproduction in mind, I'm not sure if either is necessarily an ideal
approach because the rear wave is delayed relative to the front wave.
Low frequencies are generally slow so the group delays aren't as
noticeable, but if it resulted in better sound quality then I think
we'd see Mids and Tweeters doing the same thing...

Now if you
like the general timbre that these designs present, then that's a
totally different story. Have you thought about porting the horn
instead? It's pretty much a free lunch in my perspective (as long as
you do it right...and that seems like a big if since I know Roy hasn't
had the time to iron it out completely)

There will be some acoustic traetment in the but
not a lot, cause its main function is to store my old hot rods,
tractor,and the boats when we have hurricanes. Its all reinforced
concrete, so it will have a huge echo problem.

Any option
for the walls not being perfectly perpendicular? If you're pouring
concrete, then it should be rather easy to have splayed walls (1" for
every foot would be an ideal). If you play your cards right, you might
be able to make the garage behave enough like a horn to further project
the sound outside...

I'll never do those pretty horns you sent, they look very fragile!

Pat posted that picture...I had something very different in mind []

On
that note, I would try to avoid putting anything inside the mouth of
the bass horn...especially the squawker/tweeter as the bass waves will
amplitude modulate the higher notes (especially when the entire mouth
of the tweeter is engulfed in it). It'll sound like your voice does
when talking into a fan (but hopefully not as dramatic). It will also
cause reflections inside the bass horn, which seems kinda contradictory
to the whole notion of making a good horn in the first place.

Considering your
application, I think it would make more sense to have the bass horn "on
the floor" and then mount the mid/tweeter up above the mouth...This
will get you better coverage inside your garage as it gets the majority
of the sound up above all the cars and stuff - and making it easier for
the sound to get outside for the parties. The bass will have an easier
time wrapping around obstacles too.

I
have been watching others projects and trying to figure out why they
are not getting the expected gain from their horns. I am perplexed as
to why........ I got to get up on horn theory!

Probably
because they're making the horn too short...quarter-wavelength is
really a very hard limit - you can do stuff to change how the knee
behaves, but that doesn't change where the rolloff starts to happen. If
you want a solid 20Hz, then you'll need a horn that is longer than
14ft...the size of the mouth will then determine the ripple through the
passband - I would recommend a flare angle of no less than 30 degrees
at the mouth as the acoustic impedance is close enough to flat at that
point - 45 degrees would be better, but it takes a lot to influence the
frequency response. For a 20Hz tractrix flare, that comes to over 100sq
ft for the mouth. 10x20 is 200 sq ft so you're pretty much set there.
In fact, you could easily do a 16Hz flare with 200sq feet.

Btw, are you thinking one or two huge bass horns?

I have some idea's rolling around.........Ever seen
an ATC 3" dome midrange? They have relatively high sensitivity for a DR
at 96, very flat smooth response, they take a load of power with the 3"
VC, I can lower the FS with a mod/larger resonance chamber on the back.
It couldn't be used as an upper bass mid, because it cant go that low,
but it is smooth as silk, and if I could build the right horn for it
and get the gain up to say +7db...It would be a dandy driver. What are
your thoughts on that? They dont go into compression of signal until
well over 125 as a DR, so they are quite impressive and again SMOOTH
!

While I can't say this opinion is firmly grounded in
real world experience, all of the math and programs I've been cranking numbers in seem to
indicate that the "direct radiator sensitivity" is mostly irrelevant in
light of the horn. In other words, I've seen cases where a 96dB driver
and an 88dB driver yield pretty much the same sensitivity when mounted
on similar horns. The biggest difference is the size of the rear chamber...

Also, the advantage of a horn is that it
dramatically reduces the excursion for the same SPL....the implication
being that you usually end up with a system that is thermally limited
instead of mechanically limited. So if you're worried about maxSPL,
then you want to stick to drivers that are good at removing heat - so
basically higher power handling.

Anyways, some of the best
sounding midrange I've heard is with cone-loaded horns....but if you go
that route, then you're gonna have a hard time finding an off-the-shelf
horn to work with a 3" cone. Also, at higher SPL's a standard cone is
likely to run into cone-breakup (assuming it's a paper cone). I know building some wood horns isn't out of the question, but I would plan on building a few if you're gonna get tweaky with it.

The TCI drivers I have are insane subs.... I am not
above having them specifically make what I need for the low bass horns,
they are near me here in Florida. Their drivers are just gorgeous, ever
seen one?

I'm not familier with TCI? Got a link?

These guys are pretty insane too:
http://www.audiopulse.com/products/subwoofer-drivers/lms-ultra
(perfectly linear over 30mm of excursion on an 18" driver that can eat well over 3000W)

Not sure they'd be a good choice for a horn though.

The Mid bass driver should be relatively easy to
source..its the tweeter thats bugging me. I am very picky on tweeters.
Theres very very few that I like and I have played with around 100
different ones over the years. I HATE Piezo's, the little EV's, and
most every compression tweter I have ever heard (yeah, I know...) I
seem to be hyper sensitive to the 4K-12K region and I can usually hear
real well up past that, piezo hiss drives me batty. I can tell if they
are on in a club as soon as I open the door. I am still doing sound for
a local group and I detest the tweeters in the Mackies we use.

Are you familiar with the SA8535?

http://www.stageaccompany.com/en/products/ribboncd.php

I've
not heard one for myself (yet), but I've heard only amazing things from those that have....and
all the measurements are freaky awesome (I've seen more than just what
they publish). However, I think a lot of what you don't like about
compression drivers is portrayed in the waterfalls they advertise with
(lots of ringing from the cone-breakup).

You might also consider
some of the TAD drivers that are using Berrylium diaphragms.....they've
got some impressive waterfalls too. The nice thing about the TADs is
that you'll have an easier time finding a horn for them.

Btw, I would recommend trying to stick a system that has a flat as
possible power response (which would mean constant directivy EQ'd to be
flat on-axis). You mentioned earlier something about EQ'ing for the
outdoor parties, but if you've got a flat power response then you won't
need to do any EQ whatsoever...

On that note, you might look into some of the horns from these guys (if you can't purchase the horns from Klipsch):
http://www.ddshorns.com/catalog.php?page=products

They also do custom designs - and considering their polars, that'd be something I'd definitely want to consider.

As
far as the slot in front of the driver....that acts like an acoustic
low-pass filter. It also presents an extra pole for boosting the HF
performance a bit too. Klipsch classically combines this with a rubber
throat to keep the low frequencies from overloading the horn (which
sounds really nasty when that happens). It also gives you a higher
compression ratio, which gives you more efficiency and the smaller
mouth will tend to improve HF polars. Going too small will sacrifice low-end extension.

[DrWho]

I think...... a horn (at its simplest) is no more than an acoustic transformer, and as such its function can be predicted.

A horn is an acoustic transformer and a wave guide...

All of the flare rates are methods of calculating the acoustic impedance seen by the driver, which then determines its efficiency. However, identical area expansions (flare rates) can have very different polar responses.

I also think (plz correct if I am going the wrong way, NEW TO HORNS!) that right at the point of coupling, must be VERY important.

I agree.

[Marvel]

Low frequencies are generally slow...

Mike, can you explain this a bit more. I have learned that the actual speed is independent of the frequency, i.e., bass freq. speed through air will be the same as mid or treble. It would change with temperature, humidity, etc. but would change for all equally. I thought the bigger problem was the time alignment of the drivers in a given configuration.

TIA,

Bruce

[DrWho]

Yea, the speed of sound is the same at all frequencies (or close enough to what we care about).

I guess you could say I'm talking about the speed of the phase rotation....or basically the fact that lower frequencies take longer to move through an entire cycle (360 degrees of phase). Picture one full cycle of a sine-wave.

For instance, 1 cycle of 100Hz takes 10ms. 1 cycle of 1kHz takes 1ms.

If you have some delay in your system that causes 1ms of group delay, then you're only looking at 36 degrees of phase rotation at 100Hz, but a full 360 degrees at 1kHz. So if you've got two in-phase sound sources, but one of them has 0.5ms of group delay, then you're going to see a huge hole in the frequency response at 1kHz, but you'll barely see any change at 100Hz.

The rear wave on a driver is naturally 180 degrees outta phase with the front wave, so 0.5ms of group delay in the rear channel actually won't phase cancel a 1kHz signal. However, instead of getting one full cycle of the sine wave, you'll end up with three halves....the first will have an amplitude of X, the second will have an amplitude of 2X, and the last will have an amplitude of X. I might need to draw a picture for this to make sense...but the point is that you end up with a signal that lasts too long (even though you got the phase to line up). This is a very singular situation, but the ideas it present should make it clear that any delays result in a smearing of the sound...even though you might be able to get the phase to line up and maintain a balanced tonality.

[MikeMilliken]

Mike the bass drivers are here.......http://www.audiopulse.com/products/subwoofer-drivers/lms-ultra

Its TC sounds, sorry for my crappy typing, I got "sausage" sized fingers. It'd be my guess that TC sounds probably make the drivers you spoke of. Mine have 3" of linear travel.... They are more like air hammers than speakers, crazy heavy too. BUT! with your comment on excursion, these bad boys might just be "wasted" in a horn. So maybe I'll make some headphones out of them with a hahn's brace so my neck doesnt break.

The speed of sound for our uses is 1125 FPS @ 20 cps/HZ that ought to be a wavelength of 56.25'. I know its affected by humidity, altitude, etc... But for my purposes thats fine... I am nearly at sea level where I live.

That being said, I had planned on building either a 1/2 or 5/8 wavelength line since I have 35 acres to work with, size is of no concern. I think a bigger line will be easier to get the expected reults and the gain I am looking for... Right track there?

A 16hz tuning would be fine, as would a 20, I just used 20 as a minimum.

TC is also bringing out a new line of pro drivers and compression drivers. I am going over there in about 10 days to check them out. I got friends there.

I had considered using the backwave off the subs in some fashion, maybe a 6th order tune (like you said free lunch) But with the horn gain, I'm not sure I could even hear it. I just thought it could be useful for tuning in some fashion instead of just letting it heat the air inside the sub enclosure

Any reason I couldn't "fly" the mid/tweeters just above the horn opening? That would let me aim them and keep them out of harms way. I gotcha about keeping them out of the bass horns terminus.

I can do the walls any way I'd like I suppose. I never thought about sloping them out, but I understand what that would do to the room response;) I do want to keep the building in a parallelagram shape though. I had even considered some variation of the "Golden Rule" IE; make the roof higher and the length longer to get closer to it anyways. I am building an apartment upstairs.

Mike, I dont understand the tapped horns, so I had not considered that. I dont see the benefit in it. I remeber seeing a "unity" horn years ago and I figured it was just marketing hype.

I have used beryllium drivers before, Yamaha used to have some. Super strong, very light and pretty cool looking too. That metal has some great qualities, just dont touch it! It has some nasty effects on humans.Thats a great material for a comp driver diaphragm, last I knew it wasnt cheap either.

I just renewed my membership in AES, so I could get back into the archives without dropping a ton of money and I drug out High Performance Loudspeakers, Martin Collum, to brush back up on my theory. I hadn't seriously played with speakers in years, Real Estate development has been crazy in Florida and I simply had not had the time to do anything except play Monopoly for real. I am glad for this break, and the time to pursue my passions.

I am grateful to you and all the others here who have spent their time on/with me. THANK YOU ALL!

[MikeMilliken]

Mike, One thing caught my eye......

BASS IS SLOW?

Isn't the speed of sound constant? (other than/temp/humidity/altitude) I didnt think it was "frequency dependent"

I know about the wavelength and the phase, I got that down. I know how to manipulate that as well.

OR.....does the compression of the signal in a horn/expansion rate do something wasnt aware of?

[DrWho]

That being said, I had planned on building either a 1/2 or 5/8 wavelength line since I have 35 acres to work with, size is of no concern. I think a bigger line will be easier to get the expected reults and the gain I am looking for... Right track there?

The longer you go, the lower the Fc of the horn....however, for a fixed mouth size, going longer will actually result in a more jagged frequency response. Basically it comes down to the angle of the flare at the mouth causing a discontinuity. Another way to think of it, as you go longer without making the mouth bigger, the horn starts looking and behaving more like a pipe - so you start exciting the pipe modes.

If you stick to parallel walls, are you gonna require that the walls be flat? You could easily integrate a phase grating or some other form of diffraction. If you can't do anything, then you might want to look into narrowing the polar response of your speakers to help keep the sound off the walls.

[DrWho]

Isn't the speed of sound constant? (other than/temp/humidity/altitude) I didnt think it was "frequency dependent"

Correct, it is constant over all frequencies.

What I'm talking about is the period, which is the number of seconds per cycle (which is the inverse of cycles per second). Lower frequencies take more time to complete one cycle.

1kHz moves "back and forth" 1000 times per second, so each cycle takes 1ms. 100Hz moves "back and forth" 100 times per second, so each cycle takes 10ms.

I'm calling bass "slower" because 10ms for one cycle is a lot longer than 1ms for one cycle.

[MikeMilliken]

All over that,,, Thank you Mike, you scared me for a minute. I'd been out of this stuff for about 20 years, but I thought physics involved was still the same

In that vein, thats part of the reason sharp slope crossovers sound better (when you get them right) That "smear" you mentioned earlier.

I am with you on the "time" as being relative to the frequency. Glad you are here. You are seriously helping my re-learning curve along sir!

I think I forgot more than I remember

[MikeMilliken]

Mike, I have those woofers. The 15" ones, they are crazy good:)

That link on the ribbon compression drivers has me thinking. I got 8 Hi-Vi research ribbons left, would you like a pair to play with? You can have a pair, just pay the shipping. These are pretty big, and they sound sweet, just not real efficient, maybe 90 db 1W1M. I was going to do a line array at one time then I lost interest.

I then acquired all the parts to do a Dynaudio Evidence/Consequence. I still got all the stuff for that too. Just no cabinets, I went in the attic to get the 8 woofer's to start the project about a week ago and the surrounds had deteriorated.

So I got 8 brand new Dynaudio 21W 54's, that never had power on them, ruined...........I hate foam surrounds.

I dont know how they are getting the ribbon tweeters to take so much power, they are pretty fragile, and I have smoked a bunch of them. maybe you can figure it out? You want a set?

[Marvel]

Thanks Mike. I understand what you mean. I'm too easily confused, lol.[*-)]I hadn't been thinking about the period for a given frequency.

[colterphoto1]

Sorry, again I was a bit unclear....

Seems to be a habit of mine.

This will better explain it.. take the guy on the forum that has the 2 bass bins, what appears to be a large mid or mid bass bin, and BIG unfolded midrange horn, with a tweeter sitting on top. it looks to be either theater or commercial stuff. I cant see so good, so i dont know if its flying gear or intended to be.

But anyway in my terminolgoy, I'd call his array a WWMMT, IE woff/woof/ mid (mid bass?)/mid/tweet

hope that clears up any confusion I was responsible for.

Mike Milliken

Understood, I thought you were planning on using the Klipsch folded horn MWM for your bass unit.

You're discussing driver configuration on the motor board, something akin to the D'appolito configuration.

[colterphoto1]

Can ANYONE tell me why, you put a big woofer on a horn throat and then hook to a 3" wide opening. This certainly looks terribly constrictive! Is this PWK's way of making a very short (comparitively) horn work?

I can't say for sure, but maybe it's to make a conventional cone woofer behave more like a compression driver, so its sound is closer in nature to the sound produced by the compression drivers of the squawker and tweeter.

spot on