Doesanyone cross horn subs to sealed for low bass ? - diyAudio
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Old 21st March 2005, 10:58 PM   #1
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Question Doesanyone cross horn subs to sealed for low bass ?

I was just wondering if anybody uses sealed eq'd type subs below horn subs. I'm guessing a digital delay would help.

The reason I've never tried a horn sub is the higher cutoff of horn subs (I know thats a limitation of my rooms size, rather than horn subs btw )

I'm thinking my 3 tempests below a pair of 30Hz horns could be very interesting, giving me the 15Hz extension that I get now, with better defined bass and more 'dynamics' in the lower mid stuff (40 - 80Hz)

At the moment my mains have 2x10" s-speaks per side, and they sound great flat to 20Hz at lower volumes. Crossing to the tempests at 40Hz, 24dB xo gives no loss of quality, but better extension, and allows dynamics at a higher volume. Crossing them to the tempests at 80HZ gives even better dynamics, but lower definition of bass. I'm thinking maybe a pair of horn subs to replace the s-speaks will give better dynamics/definition, and crossed to the tempests will still give me low bass I need

Any input is appreciated

Cheers,

Rob
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Old 26th July 2005, 06:27 AM   #2
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Rob, looks like we're on the same page there. My feeling is with my AV12s that double bass in particular sounds just a little muffled/lacking definition in the upper bass range. This is true even with a calibrated perfectly flat response.

I'm curious to try dipole bass in that range, but it's not going to get the dynamics I want without being larger and more expensive than I can live with for now.

I've been considering a 40 Hz horn with a high excursion 8" like the Apex Jr / TB / MCM ... however these are cheapies and only likely to be more accurate due to the (compromised) horn loading. As I understand, the rear compression chamber equalises pressure on either side of the cone and in effect forces it to be more linear, while at the same time, increasing efficiency. Hence distortion is lower in two ways.

However, I wonder if a better approach is to start with a driver which has lower distortion in the first place. The koda 8" appears an excellent candidate with high xmax and fs, and its xbl2 motor, although it's likely hard to get hold of now

Just a thought. I wonder if you may have better options than the Lab subwoofer. Of course there is a good compromised horn design. Then on the other hand you miss the learning curve, and the chance to remove some compromises and make something better.

* compromise 1 - size - can you live with bigger?
* compromise 2 - driver - how about a driver that is more linear?

I believe horns are made small by doing things like using an 8" or 12" high excursion driver, but what if you started with a driver that is more linear in the first place? Say for example a number of horns based on the Eminence Magnum 12HO? It's the cheapest high efficiency driver I've seen that is designed for bass and has a shorting ring and it's very solidly built. I can get it for the price of a scan speak, yet I suspect it has the same quality ... just more quantity!

I had a play with hornresp last night, and I'm finding it's very easy to get a VERY BAD horn if things aren't quite right. Change a few numbers and instead of flat response to 40 Hz, you get the worst kind of response you can imagine, with huge sharp spikes and a very high F3. Hmmmmm, not as easy as I'd hoped!
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Old 26th July 2005, 07:59 PM   #3
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Thanks for you response Paul.

For me -personally- I am a lot happier building the labhorn as I honestly feel that I couldn't design a better basshorn than Tom Danley. Also the lab12 driver was designed to work in that enclosure. I doubt I'd be lucky enough to arrive at the exact right enclosure for a different driver.

Also, the cad files are available and I've already converted them for my system at work , and have the sides cut for 4 cabinets already....


In hindsight I reckon a pair of decent commercial servo subs 30 - 80Hz (Paradigm servo15 / velodyne dd-18 etc) would also give excellent results, though far more expensive, and a lot less output than the labs (and you'd still need the tempests etc underneath them)


As to the compromises, The size is huge with the labs anyhow, and I'll be using 2 stacked against my back wall, firing into the corner. The linearity of the drivers I doubt will ever be a compromise in home use. (esp with 2 units)


Your definition of double bass is spot on btw
Cheers,

Rob
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Old 27th July 2005, 07:46 AM   #4
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Quote:
For me -personally- I am a lot happier building the labhorn as I honestly feel that I couldn't design a better basshorn than Tom Danley.
I see your point, and it's a point that I've considered as well. Can us diyers design a better COMPROMISED horn? Probably not.

Can we do a better bass horn if in our situation we can remove some of the compromises? I think so. With less restrictions Tom Danley could do it better, but with some of the constraints he works with being removed, we have a chance at doing something better.

Granted, the labhorn is very big. It's bigger than I can live with for now. Let us know how it goes.

What do you plan to do about the response? ie. it's not very flat ...

I've seen a modified version of the lab horn which was used in a church. The folds were removed and it was built as a single horn which was built into the ceiling space. I still don't know much about horns, but I wonder if you could either make it into a shape that removes some folding (which might or might not make construction easier). I also wonder - someone might have made a version which removes some of the compromises.

What if, for example, you built a pair of single driver versions, with the same width and depth, but a much greater height. This would then fit in the same space in your room. Just a thought. There are so many of the labhorn out there, that there might already be a less compromised version you could copy that would still fit in your room. Just a thought.
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Old 27th July 2005, 04:52 PM   #5
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Hi Paul,

If you lose some folds then you kind of end up with less but bigger folds if you get what I mean. ie 1 fold of the horn would have to be 180 degrees.... Apparently at the freq's these horns are designed for the wavelengths are too big to be affected by the folds anyhow.

I can't make them any higher as 2 stacked will be 1" off my ceiling!

The response will be similar to the plot for 4 cabs due to the wall reinforcement.
(I think..)

http://web1.prosoundweb.com/lsp/4shortlab-wfg-nd.jpg

I should also get some low end boost from room gain aswell (maybe cross at 25Hz ? )

Also I'll be using a dcx2496 to xo to the tempests so I'll have some parametric eq available, as well as the delays needed to make this work. (am planning on using a DEQ2496 aswell as the dcx so I'll have plenty of eq available)

The main advantage is that I don't have to try and work out all the folds to make the horn smooth through them..

Cheers,

Rob
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Old 27th July 2005, 05:07 PM   #6
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I should have added - If you change the mouth size then don't you have to change the length ? If so you'd be making a new horn which would mean designing all the folds etc from scratch. Not easy. (for me at least)

I like the idea of following a plan on this one.

Rob
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Old 28th July 2005, 08:25 AM   #7
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Rob, you and I might sometime in the near future end up with a fairly similar system! I have ultracurve and plan to get ultradrive. I got out a tape measure and walked around the room to see where a lab horn might fit! That thing is HUGE! If I put one flat between my mains, there would not be much space between and it's not far from being a foot rest as well in that position!

I did some simulating in hornresponse last night and managed to get a similar looking response. There is a peak around 35 and 90 Hz. One thing I found is that as you make the throat area larger, the bottom peak becomes more pronounced. As you make it smaller, the peak flattens until it is completely eliminated. It does not seem to affect the rest of the response, although there is a small impact on cone excursion. I also found that adjusting the throat area and the volume of the rear chamber together is a good way to control the bottom end of the response.

The volume in the rear chamber, VRC has a big impact on excursion control and bottom end efficiency. Below fc, you then have a sealed box. So I started to think, what if the rear volume were increased? Another what if scenario I tried, was using my drivers with twice the excursion of the Lab12. With 70L total VRC, I was able to get 115db as I recall @ 20 Hz. Not bad since I can't normally get that in a sealed box!

This approach has a few downsides though. I think first is it may not be as linear over the horn range, since VRC is intended to force the driver to be more linear than it would in any other loading. Second, cone excursion increases rapidly below fc, yet there is no visual feedback to see when the driver is being pushed. Hence damage from overexcursion is possible, although this occurs when there is 135db above 40 Hz and 115db @ 20 Hz with just one of them.

One thing I notice about the Lab12 is that it's designed with a lot of excursion control. The very small VRC restricts excursion very effectively below fc. The axial length is about 3.6m, but it seems for a 40 Hz version you can make it about 3m with a slightly smaller mouth.

Still, this is just a newbie playing around with hornresp.

My (currently novice) opinion is that if you are going to drive it with less than 500w and use a highpass around fc, you might be better with some slight modifications to smooth the response a little for home use. I'd be very interested to hear from some more experienced horn guys on what they think of modifying the Lab12 for home use.

EDIT: not trying to get you to change your mind, just thinking out loud really ...
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Old 28th July 2005, 07:27 PM   #8
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Hi Paul,

""Rob, you and I might sometime in the near future end up with a fairly similar system!""


Reading some of your other posts I think you may be right...

I'm about to build a pair of Wayne Parhams midhorns to have a listen to aswell.. You don't seem to find many midhorn designs for the 300 - 1200 Hz range, which seems strange to me but I'm no horn expert..Is there something fundamentally wrong with this type of horn ?

http://www.audioroundtable.com/PiSpe...ges/14408.html

I liked the look of this implementation :


http://www.audioroundtable.com/PiSpe...ges/17117.html

I'm pretty sure you'll have seen the 'V.3 Labhorn' here :

http://www.geocities.com/hulkss/index.html

He has made some changes to try and smooth out the top end I believe... I think the horn extentions may come into the equation though.



Good luck with the horn building / how to web page btw - I think thats a great idea..

Cheers,

Rob
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Old 28th July 2005, 10:53 PM   #9
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Greets!

There's nothing fundamentally wrong with horn loading any BW, but why only two octaves unless it's strictly for bridging the efficiency gap between a compression driver and HE woofer system, such as Altec did with the A7, which only loads from ~175-337 Hz. Historically, a horn good to a 1200-1600 Hz XO point loaded to 80-100 Hz.

GM
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Old 29th July 2005, 04:41 PM   #10
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Thanks GM.

Waiting for delivery of 9 sheets of mdf at the moment. Looking forwards to hearing what hornloading does for the midrange.

Rob
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