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  #1  
Old 06-16-2011, 12:46 PM
herbalpudding herbalpudding is offline
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Using front-loaded and rear-loaded horns together?

Hi everyone,

I am going all-in on trying to scrap together a big time system, even though I am new to the sound game. I am sure I will have a number of questions for you guys as I progress, but my first one is this:

Are there any known issues in using front loaded horns along with rear loaded horns in the same setup?

I am looking at pairing four 18" or 15" front loaded speakers with a pair of JBL 15" scoops. The room will probably be square or slightly rectangular, probably about 30x30 or so, possibly larger. I was planning to just get everything together in a room and test it out, but if there's a rule about this stuff I should probably learn it in advance!

Thoughts? I trust you guys for guidance! Thanks!
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  #2  
Old 06-16-2011, 04:36 PM
der geile ami der geile ami is offline
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It is generally a bad idea to mix sub types due to individual phase response characteristics. In simple terms, the boxes will be fighting each other and you can end up with less output than if only using one.

if you HAVE to, put all of one type on one side, and all of the other on another, or dedicate them to separate and not overlapping xover passbands
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  #3  
Old 06-16-2011, 05:03 PM
mg75 mg75 is offline
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are you planning a typical oldschool nyc 4 stack style setup?
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  #4  
Old 06-16-2011, 05:41 PM
herbalpudding herbalpudding is offline
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That's a good question

I'm not sure exactly -- it doesn't have to be a 4-corner setup as far as I am concerned. I prefer sound over aesthetics in this instance. But I also do have an affinity for the NYC setup. My main priority is getting the best sound I can on the cheap and cheap using vintage gear or refurbishing stuff myself.

A lot of my plans have come from what I have found to be available for cheap in my local area. There are a number of nice bass cabinets available right now, and I am debating which I should go for and which I should forget about.

Here are the components I am looking at to build my dream "FRANKENSYSTEM."

4 x 15" Front-loaded horn bass cabinets similar to JBL 4560
2 x 18" Front-loaded horn bass cabinets
2 x 15" JBL 4530 Rear-loaded scoop cabinets

This is just what I am looking at for the lows. Mids and highs are going to require another post! I'll also share my amp stories then.

Thanks for the help guys!

-ben
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  #5  
Old 06-16-2011, 08:15 PM
pbellsound pbellsound is offline
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Lose the scoops. Add more front loaded double 18's. The horn loaded fifteens would be more of mid-bass cabinets in this application.

As our friend in Berlin stated, don't mix different cabinets to produce the same frequencies. Unless you like smeared mud.
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  #6  
Old 06-17-2011, 12:12 AM
George Stavropo George Stavropo is offline
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I agree with Randy and especially Paul.
Dump the scoops. You can get a much better result with either a front loaded, well ported double 15 box or even a sealed double 18 bandpass box.
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  #7  
Old 06-17-2011, 01:10 AM
herbalpudding herbalpudding is offline
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Thank you guys, your insight has been hugely helpful to me! I've got a plan now, I'll let you know when I'm further down the road!

Cheers,
Ben
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  #8  
Old 06-20-2011, 01:31 PM
herbalpudding herbalpudding is offline
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Thumbs up Next steps

Woo!

I got my 4 front-loaded horn mid-bass cabinets. They are big and heavy and look like fun (hopefully more fun to play on than lift by yourself!).

They consist of the following:

2 - JBL 4560 15" cabinets
2 - Kustom FLH15 15" cabinets with woofers

My plan is to buy 4 new speakers to install in all of these cabinets to keep the sound as consistent as possible. Would you guys recommend anything in particular for these 15" drivers?

Fred Bissnette, who was hugely helpful in recommending the Kustom boxes (THANK YOU!!!), suggested I try something from Eminence. Looking through the archives, Scotty always seemed partial to the B&C models for this type of speaker cabinet. I am a newbie to this and all of the reviews on Parts Express are pretty positive across the board.

Thanks!

-ben
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  #9  
Old 06-20-2011, 02:47 PM
Mistick Krewe Mistick Krewe is offline
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what are your plans for HF/UHF reproduction?

where's your anticipated crossover, about?

that'll give you a good idea of what you need in the woofer's
upper end of response...

i've crossed Altec/GPA 416 & 515 series & Tad 160* series drivers
pretty high with good results...

Last edited by Mistick Krewe : 06-20-2011 at 02:51 PM.
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  #10  
Old 06-20-2011, 03:25 PM
jnkarrik jnkarrik is offline
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I have JBL 2220H drivers in my 4560's. I have also heard of others using D130 drivers with some success. I do not have any experience with TAD drivers in this box, but I wonder if a TAD driver might outclass this box slightly. Could be worth it if you found a good deal, but I have no first hand input.

I am crossing my cabs at approximately 800hz to a 2441 driver with a UREI 525 X-over. I let them roll off naturally on the lower end.

As with anything you read on the internet, take my suggestions w/ a grain of salt. I am new at this too, and learned what little I know from Scott and the few others on this board who have been willing to share.

~Jason
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  #11  
Old 06-30-2011, 07:13 PM
herbalpudding herbalpudding is offline
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follow up

I was poking around the site and saw this photo that LimeTwig had posted of the El Dorado stacks - and it appears that Scott had the double JBL scoops with double 15" front loaded speakers on top. That's what I was talking about doing, wasn't it?

See what I am talking about here:
http://farm5.static.flickr.com/4065/...74407c8b_b.jpg

This is essentially what I was talking about from my initial post - stacking 4560's on top of the scoops. I want to do the exact same thing, except instead of doubles mine would all be singles.

What gives? Was Scotty breaking recommended rules or was I using the wrong terminology in my post (more likely)? It could be any number of things, but I figure you guys could help steer me right.

Also, I picked up an Ashly XR-2000 3-way crossover for cheap that I plan to use to get started. Hopefully further down the line I can get my hands on a Marchand!

Thanks,
Ben
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  #12  
Old 06-30-2011, 08:36 PM
atf104 atf104 is offline
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I will add that you can sometimes split a range (sub or mid-bass for instance) with frequency shading, where the same or similar speakers are covering slightly different frequency ranges with good results. I personally agree with dumping the scoops in this particular scenario as I'm just not a fan of them either.
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  #13  
Old 06-30-2011, 09:20 PM
Elliot Thompson Elliot Thompson is offline
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Quote:
Originally Posted by herbalpudding

This is essentially what I was talking about from my initial post - stacking 4560's on top of the scoops. I want to do the exact same thing, except instead of doubles mine would all be singles.


What gives? Was Scotty breaking recommended rules or was I using the wrong terminology in my post (more likely)? It could be any number of things, but I figure you guys could help steer me right.

Also, I picked up an Ashly XR-2000 3-way crossover for cheap that I plan to use to get started. Hopefully further down the line I can get my hands on a Marchand!

Thanks,
Ben


You were using the wrong terminology.

JBL 4560 are Straight-Horn Vented cabinets.

JBL 4520/4530/C3 are Rear-Loaded (vented) cabinets.

Folded horns are almost always sealed cabinets with a horn.

The midrange cabinet shown appears to be a sealed cabinet with a horn.

Phase issues will always occur using a sealed cabinet with a vented cabinet
on the same frequency band.

That is the law of physics.

Best Regards,
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Last edited by Elliot Thompson : 06-30-2011 at 09:25 PM.
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  #14  
Old 07-03-2011, 02:51 AM
Lime Twig Lime Twig is offline
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Elliot,

Could you explain why this is? I've never quite understood it. Here's why, specifically:

Phase, as I understand it, is essentially about timing, correct? Timing, as it relates to the sound waves being produced by different drivers (in a stack of speakers in this case).

The drivers are in phase when they are are producing the sound at the same time and are physically in the same plane. They are out of phase when either one driver is electronically delayed (for whatever reason) or when one driver is physically delayed, for example, when they are not physically in the same plane.

This latter situation is why you shouldn't mix types of sub as far as I understand. Combining a direct radiator with a folded horn, for example, would mean the drivers are out of phase because the driver in the horn is physically further back from the direct radiator.

If this is true (and I'm hoping you'll correct me if I've got it wrong) then there shouldn't be a problem combining sub types provided you physically positioned them so they would be in phase, right? Or, in cases where the subs are in a completely different location (like in Scotty's system where the J-scoops are on the other side of the room) it shouldn't matter at all I'd think. Your problems with phase cancellation would be a whole different ball game.

Am I on the right track here? If not, what am I missing?


Quote:
Originally Posted by Elliot Thompson
Phase issues will always occur using a sealed cabinet with a vented cabinet
on the same frequency band.

That is the law of physics.

Best Regards,
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  #15  
Old 07-03-2011, 09:41 AM
der geile ami der geile ami is offline
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There is a delay for the sound to leave any box, but it varies with respect to frequency. This is due to electronic crossovers and eq causing a frequency specific delay (fir filters as opposed to iir filters are better at that, at the expense of delaying the entire signal for the algorithms to do their work) and also the physical design of the box.

Take a ported box for example, the sound leaves the cone at one rate, but travels through the box and out the port at another. A the bends of a folded horn will influence its phase response. However, with complex electronics, the phase response of a box can be somewaht controlled, so subs *might* be able to be mixed within a specific manufacturers product line, such as meyer or d&B. Additional delay might still be necessary, but 50hz might be tamed.

im fighting a cold, but does that help?
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  #16  
Old 07-03-2011, 10:32 PM
Elliot Thompson Elliot Thompson is offline
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This photo illustrates two enclosures using the same internal cabinet dimensions and, same driver. The only difference is one is sealed while the other is vented.





As you can see, the phase separation begins approximately 80 Hz and, begins to widen as the frequency decreases.

Under such circumstances, the only remedy is to either seal or vent both cabinets. Reversing the polarity generally gives many the assumption it will solve the problem.

What will occur by reversing the polarity is, alter the direction on how the loudspeaker will cancel. So the yellow line will face donward but, will still be
out of line with the red line.

This is a mechanical error which cannot be fixed electronically. Both lines must be curved below 80 Hz or straight below 80 Hz to prevent any phase cancellation below 80 Hz.

This is why using sealed and vented cabinets on the same frequencies (particular within the bass region) is not recommended.

Best Regards,
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Last edited by Elliot Thompson : 07-03-2011 at 10:39 PM.
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  #17  
Old 07-03-2011, 11:45 PM
pbellsound pbellsound is offline
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Very nice images and description!
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  #18  
Old 07-04-2011, 04:40 AM
Lime Twig Lime Twig is offline
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Sadly, Elliot, I think I must have misunderstood the concept completely, because I don't understand your explanation at all!

This is partially because I don't understand what I'm looking at in that diagram, but mostly because I don't understand why a sealed and vented cabinet would start to diverge at low frequencies if they were in the same physical plane to start with.

Wait: is it because one driver can respond more quickly to low frequency notes than the other - because one is sealed and one is not?

...
I went looking for an old website where I remember reading about this for the first time and, when I discovered it, realized that I was thinking about time alignment, not phase (though I still don't quite understand the difference).

Here's the link, the pictures illustrate the phenomenon I was trying to describe: http://www.lenardaudio.com/education/06_x-over_4.html

Best,

Quote:
Originally Posted by Elliot Thompson
This photo illustrates two enclosures using the same internal cabinet dimensions and, same driver. The only difference is one is sealed while the other is vented.

As you can see, the phase separation begins approximately 80 Hz and, begins to widen as the frequency decreases.

Under such circumstances, the only remedy is to either seal or vent both cabinets. Reversing the polarity generally gives many the assumption it will solve the problem.

What will occur by reversing the polarity is, alter the direction on how the loudspeaker will cancel. So the yellow line will face donward but, will still be
out of line with the red line.

This is a mechanical error which cannot be fixed electronically. Both lines must be curved below 80 Hz or straight below 80 Hz to prevent any phase cancellation below 80 Hz.

This is why using sealed and vented cabinets on the same frequencies (particular within the bass region) is not recommended.

Best Regards,
__________________
Good Faith
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  #19  
Old 07-04-2011, 12:34 PM
herbalpudding herbalpudding is offline
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Thanks for that info Elliot, that's very cool stuff.

I think I was mislead from the get-go (again!) in that I was under the impression that scoops were designed to hit lower frequencies (i.e. sub-bass) than the direct vented straight horns. It sounds like what you guys are saying is that they were designed to do the same exact thing as the direct vented enclosures (mid-bass).
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  #20  
Old 07-04-2011, 02:56 PM
Elliot Thompson Elliot Thompson is offline
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Thanks Paul.

Happy Independance Day!

If I could do it again, I would have worded it differently.


Limetwig, the answer is very simple. The back wave of the speaker (which is escaping through the vent) is out of phase with the front wave (This is the frontal part of the loudspeaker).

Since all reflex cabinets will be out of phase at and below the tuning (fb) frequency, whereas a sealed cabinet is in-phase at all times, the graph shows a cancellation (or phase shift) which, begins approxiamately 80 Hz. Such a phenomenon is like trying to join oil and water. No matter how hard you try to mix the two together, they will not blend together.

Bare in mind, the example shown is based on all things considered equal. The only exception is having one enclosure vented while the other is sealed. Under real-world conditions, there will be more things to take into consideration due to different cabinet sizes and/or loudspeaker TS Parameters.


Herbalpudding, I am in the same camp as Paul in terms of Scoops. Scoops offer an exaggeration around 60 Hz, cancels itself at 80 Hz and, offers more exaggeration from 90 Hz onwards. Scoops work well for music that offers sustained notes like old Reggae, in addition to Drum & Bass. This is why Scoops are popular in that market.

Scoops also rely heavily on equalisation to attain a substantial amount of low bass. They are not very efficient below 50 Hz, which is not considered low bass in this day in age. Even in the Disco era of yesteryear, Scoops (aka Waldoff) were used more as a bass cabinet with a large folded horn sitting below covering frequencies below 55 Hz.

A reflex cabinet’s low frequency roll-off point varies pending on the design. Nevertheless, you can expect an off-the-shelf sound reinforcement reflex sub cabinet to bring forth anywhere from 40 to 30 Hz, @ –3 dB. This is why reflex cabinets are more popular than Scoops globally. A reflex cabinet offers the lowest bass response in the smallest package with good efficiency.


Best Regards,
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  #21  
Old 07-05-2011, 05:41 AM
Laurin Laurin is offline
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Yeah the scoop thing.

But not all scoops have the frequency dip at 80Hz. I own right now two different type of scoop designs (Besides the 4520 I just sold and my version of the Jensen Imperial).
A 15" mini scoop that has +/- 4dB @40Hz and has a very large dip (10dB) at 160Hz. It works very well for Sub and Kick.

And Rog Mogale's 21" Super Scooper:

(Plot made using 4 cabinets with PD2150 in parallel
1w/1m Half Space with 120 Hz lowpass filter. f3 = 27 Hz)

The 15" mini scoop works well for all type of music, even live sound.
The 21" is a beast for Dub Step/Drum Bass
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  #22  
Old 07-05-2011, 12:29 PM
herbalpudding herbalpudding is offline
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Quote:
Originally Posted by Elliot Thompson

Herbalpudding, I am in the same camp as Paul in terms of Scoops. Scoops offer an exaggeration around 60 Hz, cancels itself at 80 Hz and, offers more exaggeration from 90 Hz onwards. Scoops work well for music that offers sustained notes like old Reggae, in addition to Drum & Bass. This is why Scoops are popular in that market.

Scoops also rely heavily on equalisation to attain a substantial amount of low bass. They are not very efficient below 50 Hz, which is not considered low bass in this day in age. Even in the Disco era of yesteryear, Scoops (aka Waldoff) were used more as a bass cabinet with a large folded horn sitting below covering frequencies below 55 Hz.

A reflex cabinet’s low frequency roll-off point varies pending on the design. Nevertheless, you can expect an off-the-shelf sound reinforcement reflex sub cabinet to bring forth anywhere from 40 to 30 Hz, @ –3 dB. This is why reflex cabinets are more popular than Scoops globally. A reflex cabinet offers the lowest bass response in the smallest package with good efficiency.

That answers everything I wanted to know! Thank you!
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  #23  
Old 07-05-2011, 12:40 PM
Elliot Thompson Elliot Thompson is offline
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Laurin,

Rog never liked Scoops for anything except Reggae.

He only made the Super Scoop due to countless nagging from others to design one. If you look at his company, (http://voidaudio.com/) Rog focuses primarily on folded horns and a few front-loaded designs. I might add, Rog was one of my mentors on learning the fundamentals of horn design.


The 21-inch version phase shift is further down the frequency band, however the 18-inch version falls within the realm I mentioned in my previous post. The15-inch version was the worse in terms of bass, which is why many resorted to an 18-inch version.

Rog and I chatted a lot when everyone would visit Audio Asylum or the original Live Audio forum when Dave was the caretaker pre-dating the dawning of Speakerplans.

There are plenty of mini scoops running about that is more of a reflex than a horn sporting a huge vent. In the States, Yorkville offers such a bin. http://www.yorkville.com/products.as...9&cat=2&id=126

Stapler (or was it Staplier) was the only designer that crafted a mini scoop that followed the horn principal.

Mikey, Rog, and, Tony are the only designers that created proper full sized Scoops. I need not tell you who they are if you are familiar Rog’s designs.

Best Regards,
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Last edited by Elliot Thompson : 07-05-2011 at 12:42 PM.
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  #24  
Old 07-05-2011, 12:48 PM
Elliot Thompson Elliot Thompson is offline
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Quote:
Originally Posted by herbalpudding
That answers everything I wanted to know! Thank you!


I used to own a dozen scoops decades ago. If you have any questions let me know.


Best Regards,
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  #25  
Old 07-05-2011, 02:06 PM
Laurin Laurin is offline
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Hehe I know that Rog doesnt "like" the scoops.
The 21" Scooper is a bad ass scoop.

In the last 2 1/2 years I was fooling around with scoops to understand the Bertha/Levan Horn + Waldorf combination. The 4520 couldnt do the job right the Jensen Imperial/Waldorf does it right. But to be honest I prefer a (ported) front loaded horn for the range from 100Hz upward.
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