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DIY bass horn build...Up next

post #1 of 448
Thread Starter 
EDIT: This is for PA, not home audio or HT.


Ok. I've never built a bass horn yet and after experiencing Labsubs and lately the DTS-10's I've gotten the itch to give it a go. The ported 21's are about a week away from being wrapped up and I've finally decided on a horn simulation that I'd like to turn into a pile of sawdust and wood...I think. I figure I'd better get the ball rolling if I expect to get this built before weather turns bad for the winter.

I've run through a ton of simulations in the last 6 months and there are about 20 possible scenarios that I like and about 8 that it was really tough choosing between for the build. I weeded that down to about 3 possibles by eliminating the ones involving drivers I don't already own. Why buy if you don't need to? I ended up deciding on a 380L net, 30hz FLH using the LMS 5400, over a 380L 30hz B&C FLH and a 30hz 380L B&C TH.
The performance of each is close enough on paper to make it a toss up really.

For the curious here's my thought process. The other contenders were involving dual xxx12's in a TH, TC's PA5100 and the 18sound 21NLW9600. The 18sound 21 and the B&C are VERY similar in performance when using the same enclosure, basically interchangeable IMO with very small differences in modeled performance, so that eliminated the 18sound because I already own the B&C. The PA 5100 also models very well, but differently in the same basic horn parameters as the 21's but obviously needs some changes in the overall form factor due to being a smaller diameter deeper driver. Again since none of them really showed a notable performance advantage on paper and I already own the B&C's...The dual xxx 12 sub I would really like to build (sub bass gargantua), but it's the most complicated, expensive, heaviest and largest. Maybe later. The LMS I decided on over the B&C, because it's the less obvious choice and more of a known quantity at this point. Plus I'm already doing a new build for the B&C's. The build I am doing will be leaving some of the LMS's potential on the table. It'd be better in a larger 20hz FLH or an 18hz TH, but I don't want to build anything so large and difficult to move first off. If I can't easily fit it in the back of my Jeep with the help of 1 other guy it was eliminated this is also why I ended up with a 30hz corner. The LMS doesn't like TH's so small tuned so high.




Anyway. This is what I've got. Nothing is set in stone yet. I need help reviewing the model for mistakes and I could especially use some help with folding the horn up. I've never folded one, so help or comments from more experienced guys would be much appreciated. All opinions are welcome. BTW the model is intentionally a very basic single expansion rate conical (parabolic now) type to hopefully keep the folding and build as simple and straight forward as possible.



Input parameters
Attachment 183905

Phase and delay
Attachment 183906

1W into the minumum impedance in half space
Attachment 183907

124v input in half space
Attachment 183908

124v driver excursion
Attachment 183909
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post #2 of 448
Are these the driver parameters numbers you measured yourself?

I would use Par here, and not Con. In traditional horns with straight flares it can make a difference.
post #3 of 448
I will be following this one
What the 20hz lms look like. I love big bass horn
post #4 of 448
You made the right choice going with those designs, Ricci. I would have chosen the same. Work with what you got and know is good. I'm sure you would buy more XXX's or B&C 21's now that you've used them.

Btw, thanks for modeling at half-space and not loaded into a corner or something, lol. Are you going to use them outside for music or inside for HT?
post #5 of 448
Thread Starter 
Scott,

1/8th and 1/4 space graphs sure do look cool don't they? IMO they aren't representative of what you can expect in most cases unless you are putting the sub in a car though.





Quote:
Originally Posted by soho54 View Post

Are these the driver parameters numbers you measured yourself?

I would use Par here, and not Con. In traditional horns with straight flares it can make a difference.

No. They aren't measured by me for the actual driver that'll be used. However, I've measured the parameters on 4 TC sounds drivers and all were very close to the manufacturer specs. Others that have measured their drivers have been close as well. Also TC drivers maintain their linearity much better than most manufacturers drivers from my experience. I'd trust their specs much more than most others. The other more important thing is that the small signal parameters aren't what would be best to have. I'm more worried about what they are at 65v than at 2v and since I don't have access to a Klippel... The small signal ball park parameters are what I have to go on, absent real world testing on the final bass system that is currently still vaporware.

Look at it as one might a production horn from EAW. They aren't going to individually measure each driver and then modify the horn for slight variances in production tolerance.

Why would you recommend using Par instead of con?
post #6 of 448
I asked about the parameters because they seemed a little off if going by the manual from PE. Looking back at it you just entered the parameters straight out of the manual without letting HR convert them. If doesn't matter too much with this driver, but it is a big no-no for some.

Par: "Hornresp Version 28.00 has just been released. Parabolic horns can now be modelled. Amongst other things, this enables horn segments having two parallel walls and two tapered walls to be more accurately simulated."

Con is old school. Really though, it makes a difference in some models. More so in standard single flare horns.
post #7 of 448
Thread Starter 
Quote:
Originally Posted by soho54 View Post

I asked about the parameters because they seemed a little off if going by the manual from PE. Looking back at it you just entered the parameters straight out of the manual without letting HR convert them. If doesn't matter too much with this driver, but it is a big no-no for some.

Par: "Hornresp Version 28.00 has just been released. Parabolic horns can now be modelled. Amongst other things, this enables horn segments having two parallel walls and two tapered walls to be more accurately simulated."

Con is old school. Really though, it makes a difference in some models. More so in standard single flare horns.

I'm still on 27.10. No wonder I didn't know what you were talking about. I was like Par? Time to update. David is a madman with all of the updates. Seems like he has one every month.

I usually modify the fs to get the correct mmd since most drivers list mms. Do you allow HR to calculate the driver parameters? Why would you do that? I would figure it to be like winisd where the calculated differences are only very minor ones out at 2 decimal places. I've seen some drivers much worse of course but the ones from respected mfr's usually calculate out close enough that the differences in the simulation are negligible.
post #8 of 448
Let's see, Par is a parabolic horn model. As it is more of an oval it is a better fit for the normally rectangle builds that people do. I haven't contacted Bjørn or McBean yet to find out the specifics, as I have a few application questions about the assumptions they made as no new width parameter was added, because all the horns I designed didn't change at all when switching over. As long as you are staying with a simple single non-exponential flare it seems to be the way to go. It makes a minor difference here, but I do not know how long you tweaked this one.

I always allow HR to calculate the parameters. For the life of me I can't remember why you need to do it that way right now, but you do need to do it that way. I know McBean has pointed it out several times over the years. You put in the SD, Re, and Le then double click Cms, Mmd, Bl, and Rms to input Vas, Fs, Qes, and Qms.

The TC factory parameters seem off a little because the Mmd ends up larger than the given Mms, and it should be less.
Fs = 1/(2p * SQRT(Cms*Mms))
Mmd = (Added Mass)/ (fs/(Mass fs))^2 - 1
Cms = 1 / (2pfs)^2 * Mmd
Vas = (Cms * 1.184 kg/m3 * 346.1 m/s * Sd^2)*1000__at 25C
so either the supplied Fs, or Vas is off some. Sorry too much info.

Also I am not really good with the smaller horns. I can help with folding, but not too much with design. My first pass with this driver ended up twice the size with less compression, a flatter curve, and more sensitivity, but it was still on the smallish side to me. I could live with it though, reactance annulling finally kicked in.

I ran the driver through my Leach spread sheet, and it didn't work quite right. Normally, I can design a horn for the driver, and then use that info to input the horn and let the program tell me the driver parameters it needs, and they match up almost if not exactly. This one didn't. I'll take another pass later on.

You also have a lot of Vtc there. Is that because of the surround? Is it that huge?
post #9 of 448
That hornresp can now model parabolic segments is very promising....that in and of itself accounts for the response differences between modeled and measured both in my THT and my 6.5" 30Hz horn....

JSS
post #10 of 448
i was looking at EAW's top of the line horn sub a few days ago and realized how pointless it is. it doesn't reach max efficiency till 100 hz. but you need max efficiency where max power is - 45 hz today and ~ 30 hz in the future.

what good is it that ur sub is 115 db @ 150 hz if it is only 90 db @ 30 hz and you need more SPL @ 30 hz than at 150 hz ?

below 30 hz they all work like sealed boxes. and below 30 hz is precisely where help is needed - there aren't any issues above 30 hz. so effectively you get a 20 cubic foot box doing the job of 2 cubic foot box - that's all horns are.

what horns do is they trade drivers and amps for plywood and cubic feet. only the days where plywood and cubic feet were cheaper than drivers and amps are gone.

sealed indoors. PR outdoors. horns for mid and high frequency only where they can be used for directivity advantages.
post #11 of 448
Quote:
Originally Posted by vasyachkin View Post

i was looking at EAW's top of the line horn sub a few days ago and realized how pointless it is. it doesn't reach max efficiency till 100 hz. but you need max efficiency where max power is - 45 hz today and ~ 30 hz in the future.

what good is it that ur sub is 115 db @ 150 hz if it is only 90 db @ 30 hz and you need more SPL @ 30 hz than at 150 hz ?

I think that's the only useful post you ever produced. Yeah getting crazy high SPL at 100Hz is pointless, you'll just end up with a boombox, just bigger. A lot of people tend to forget the human hearing curve, and that a measured flat response does not = audible flat response, especially down low.

Knowing the human ear's particularities and designing with them in mind is what makes crap like Bose sell. They are worth 1/8th of the price paid at most hence they are a major ripoff, but they DO sound decent.
post #12 of 448
Quote:
Originally Posted by maxmercy View Post

that in and of itself accounts for the response differences between modeled and measured both in my THT ....

It shouldn't affect the THT very much. No more than a dB bottom, and one in the middle.
post #13 of 448
Quote:
Originally Posted by vasyachkin View Post

i was looking at EAW's top of the line horn sub a few days ago and realized how pointless it is. it doesn't reach max efficiency till 100 hz. but you need max efficiency where max power is - 45 hz today and ~ 30 hz in the future.

what good is it that ur sub is 115 db @ 150 hz if it is only 90 db @ 30 hz and you need more SPL @ 30 hz than at 150 hz ?

Because they are designed to be used in groups and the LF will come up with that. The LABhorn for instance was designed to be used in groups of 4 or more packed together. The horn them effectively becomes a multi driver sectoral with a mouth 4x the size.

Try some modelling of multiples and you might get the idea.
post #14 of 448
the only thing that jumps out at me at this point is the compression ratio. do you think the lms' suspension will survive high power with a 4:1?
post #15 of 448
Thread Starter 
Quote:
Originally Posted by soho54 View Post

Let's see, Par is a parabolic horn model. As it is more of an oval it is a better fit for the normally rectangle builds that people do. I haven't contacted Bjørn or McBean yet to find out the specifics, as I have a few application questions about the assumptions they made as no new width parameter was added, because all the horns I designed didn't change at all when switching over. As long as you are staying with a simple single non-exponential flare it seems to be the way to go. It makes a minor difference here, but I do not know how long you tweaked this one.

I tried switching to parabolic and it did change the response but only subtley. It did add about 23L in cabinet volume according to the schematic tab. I'm wondering the same thing. Shouldn't there be a width parameter that has it's own entry or a slider in the wizard? Otherwise what generic profile is being calculated?

Quote:
Originally Posted by soho54 View Post

I always allow HR to calculate the parameters. For the life of me I can't remember why you need to do it that way right now, but you do need to do it that way. I know McBean has pointed it out several times over the years. You put in the SD, Re, and Le then double click Cms, Mmd, Bl, and Rms to input Vas, Fs, Qes, and Qms.

Here's my deal. When I start messing with a new driver I take the parameters and enter them into winisd first. That tells me if anything is glaringly off. Usually the specs end up VERY close with small changes. For example the qes might come in at 0.316 instead of 0.317, or the FS might come in at 20.53 instead of 20.5 as in this case. I don't worry about discrepencies that small. That have virtually no effect on the simulated performance and as we know production variance might be a couple of magnitudes bigger than this.

I did this driver in HR as you indicated and it did change a little, but most of them fall into the above noted range of not enough to worry about IMO. I had forgotten to calculate the MMD previously though. Anyway I always key off of the SD, BL, RE and mms. Those are the parameters that I expect to vary the least from driver to driver in a production run. The CMS, FS, VAS wander the most driver to driver. That's why I don't like calculating what I consider to be the more concrete parameters off of those.



Quote:
Originally Posted by soho54 View Post

The TC factory parameters seem off a little because the Mmd ends up larger than the given Mms, and it should be less.
Fs = 1/(2p * SQRT(Cms*Mms))
Mmd = (Added Mass)/ (fs/(Mass fs))^2 - 1
Cms = 1 / (2pfs)^2 * Mmd
Vas = (Cms * 1.184 kg/m3 * 346.1 m/s * Sd^2)*1000__at 25C
so either the supplied Fs, or Vas is off some. Sorry too much info.

I'm not seeing this. The factory mms is 501g, which is right. Once I calculated the mmd in HR is came in at 481.24g. Should be about right no?

Quote:
Originally Posted by soho54 View Post

Also I am not really good with the smaller horns. I can help with folding, but not too much with design. My first pass with this driver ended up twice the size with less compression, a flatter curve, and more sensitivity, but it was still on the smallish side to me. I could live with it though, reactance annulling finally kicked in.


Compression is 3-1 on this horn. I think it'll be ok. I always try for maximum bass from minumum space, or some other clear design goal. A 1000L horn looks better for sure but damn is it big. The goal for this one is to keep the external size at 18 to 19cu ft and be able to provide similar or better performance than most top of the line pro bass cabs on a DIY bassis for less money for my own personal use in that role. In that size range is JBL SRX728, EAW SB850Z, 24" THT, etc.

I will say this, after a lot of modeling it is very hard to beat vented cabinets while using the same total external cabinet volumes and trying to cover the same f3, at least on paper anyway. I could not get any horn with those constraints to outperform my control simulation of the double woofer pro bin I would personally build. The best I could do was match it on the same amount of power and the vented won out on cone displacement used per output level and by having twice the vc's.

Quote:
Originally Posted by soho54 View Post

I ran the driver through my Leach spread sheet, and it didn't work quite right. Normally, I can design a horn for the driver, and then use that info to input the horn and let the program tell me the driver parameters it needs, and they match up almost if not exactly. This one didn't. I'll take another pass later on.

I'm not familiar with the Leach sheet. I did happen to download B. Steele's TH folding excel app today though.



Quote:
Originally Posted by soho54 View Post

You also have a lot of Vtc there. Is that because of the surround? Is it that huge?

I'll need to re check that. From what I remember it was a rough guesstimate at what it would be. I don't remember it making a whole lot of difference.



Here is the difference between the original sim and the corrected one modeled as a parabolic. Not much to write home about. I'll take the extra 1db at 30hz though. Gray is the updated sim.


Attachment 183553

Attachment 183554
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post #16 of 448
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

the only thing that jumps out at me at this point is the compression ratio. do you think the lms' suspension will survive high power with a 4:1?

Compression is 3 to 1. S2 is your mid driver line. IE average cross sectional area the driver sees. Yes I think it will. If not...We will still have learned something no?
post #17 of 448
Thread Starter 
Quote:
Originally Posted by vasyachkin View Post

i was looking at EAW's top of the line horn sub a few days ago and realized how pointless it is. it doesn't reach max efficiency till 100 hz. but you need max efficiency where max power is - 45 hz today and ~ 30 hz in the future.

what good is it that ur sub is 115 db @ 150 hz if it is only 90 db @ 30 hz and you need more SPL @ 30 hz than at 150 hz ?

below 30 hz they all work like sealed boxes. and below 30 hz is precisely where help is needed - there aren't any issues above 30 hz. so effectively you get a 20 cubic foot box doing the job of 2 cubic foot box - that's all horns are.

what horns do is they trade drivers and amps for plywood and cubic feet. only the days where plywood and cubic feet were cheaper than drivers and amps are gone.

sealed indoors. PR outdoors. horns for mid and high frequency only where they can be used for directivity advantages.

Quote:
Originally Posted by Th3_uN1Qu3 View Post

I think that's the only useful post you ever produced. Yeah getting crazy high SPL at 100Hz is pointless, you'll just end up with a boombox, just bigger. A lot of people tend to forget the human hearing curve, and that a measured flat response does not = audible flat response, especially down low..


Yes this would have very good output 80-120 hz also, like the EAW mentioned but I don't consider that a waste, or the main goal. It's just a by product and extra headroom is one thing I'll never turn down. Consider what is happening at 30hz here. This is a sealed enclosure vs the FLH showing what the horn is doing for the driver. Yes you can get some extra output vented but not enough to close that gap. Also don't forget that in live sound or sound reinforcement they do not care about <30hz precisely because it is so difficult/expensive to get adequate output there to cover a few hundred or thousand people in a very large room or outdoor setting. You want the least amount of cabinets and power needed to more than adequately cover your goals. Deeper extension makes this more difficult. This is why so many pro cabs are already dropping off at 45 or even 50hz. It's so much easier if they don't try for even 30hz extension. For HT or a personal music system other compromises can be made.



Attachment 183558
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post #18 of 448
Thread Starter 
That's not a bad looking folding scheme (either one). One thing. The driver itself is 18.5" OD so the cabinet has to be a minimum of 19" internal. I was actually figuring on about 22.5" internal width which would put it at just under 24" wide external.
post #19 of 448
i botched the mouth size, which botched the expansion angle. let me redo using 22.5" width also.
post #20 of 448
it's funny, but after the adjustments, it is looking almost exactly like a tht.
post #21 of 448
Thread Starter 
Quote:
Originally Posted by LTD02 View Post

it's funny, but after the adjustments, it is looking almost exactly like a tht.

That's perfectly fine with me. That form factor would work well.
post #22 of 448
Quote:
Originally Posted by A9X-308 View Post

Because they are designed to be used in groups and the LF will come up with that. The LABhorn for instance was designed to be used in groups of 4 or more packed together. The horn them effectively becomes a multi driver sectoral with a mouth 4x the size.

Try some modelling of multiples and you might get the idea.

no they had response for a multiple array already in the datasheet.
post #23 of 448
Quote:
Originally Posted by Ricci View Post

Yes this would have very good output 80-120 hz also, like the EAW mentioned but I don't consider that a waste, or the main goal. It's just a by product and extra headroom is one thing I'll never turn down. Consider what is happening at 30hz here. This is a sealed enclosure vs the FLH showing what the horn is doing for the driver. Yes you can get some extra output vented but not enough to close that gap. Also don't forget that in live sound or sound reinforcement they do not care about <30hz precisely because it is so difficult/expensive to get adequate output there to cover a few hundred or thousand people in a very large room or outdoor setting. You want the least amount of cabinets and power needed to more than adequately cover your goals. Deeper extension makes this more difficult. This is why so many pro cabs are already dropping off at 45 or even 50hz. It's so much easier if they don't try for even 30hz extension. For HT or a personal music system other compromises can be made.





Attachment 183558

its like you're trying to say that i should read your posts before bashing them ?

are you using an LMS for sound reinforcement or something ? i don't get it.

it's just that to me if you're doing PA you shouldn't be using LMS. and if you're doing home why are you giving up on the bottom octave ?

no ?

well. it's an interesting but also expensive experiment. you are almost certainly going to end up with something out of balance like this:

http://www.youtube.com/watch?v=cugGPkt_Wnc

but as the guy said "it's good fun"
post #24 of 448
Quote:
Originally Posted by Th3_uN1Qu3 View Post

getting crazy high SPL at 100Hz is pointless.

Not at all. EAWs are intended for use in blocks of four or more, which extends the region of flat response far lower, and they're intended for pro-sound applications, which has maximum SPL demand between 50 and 60 Hz. They're not suited at all to HT, but they're not supposed to be.
My pro-sound T48 doesn't look all that impressive with one cab, but a stack of a dozen, typical of a high end pro-sound rig, runs ruler flat to 32Hz.
post #25 of 448
roughly to proportion for 22.5" wide

external dimensions are about 3 feet x 3.5 feet.

edit: image removed so as not to create confusion with latest design.
post #26 of 448
Quote:
Originally Posted by Ricci View Post

Otherwise what generic profile is being calculated?

Yeah, I have a question posted to McBean, and a PM so maybe will will find out in a little. As long as your horn path is a rectangle it will be the way to go.

Quote:
Originally Posted by Ricci View Post

I'm not seeing this. The factory mms is 501g, which is right. Once I calculated the mmd in HR is came in at 481.24g. Should be about right no?

If you use the numbers in the TC PDF manual they are off. I just tried the numbers PE had on their page, and they work better.

Quote:
Originally Posted by Ricci View Post

I'm not familiar with the Leach sheet. I did happen to download B. Steele's TH folding excel app today though.

It is a spread sheet i made using the math Marshall Leach put forth in his paper "On the Specification of Moving-Coil Drivers for Low-Frequency Horn-Loaded Loudspeakers" Recommended reading of anyone playing with horns. The Letters to the Editor section is helpful as well.

Steeles sheet is getting there. Just a few more bugs to work out.

I wasn't trying to say you needed to change anything.
post #27 of 448
Thread Starter 
Quote:
Originally Posted by vasyachkin View Post

its like you're trying to say that i should read your posts before bashing them ?

are you using an LMS for sound reinforcement or something ? i don't get it.

it's just that to me if you're doing PA you shouldn't be using LMS. and if you're doing home why are you giving up on the bottom octave ?

no ?

well. it's an interesting but also expensive experiment. you are almost certainly going to end up with something out of balance like this:

http://www.youtube.com/watch?v=cugGPkt_Wnc

but as the guy said "it's good fun"

None of my current builds going are for home use or HT. I would never intentionally use a 30hz f3 in that case. C'mon now. They are for PA work.

I don't really look at labels and if a tool fits for the job I use it. According to the simulation at least, the Lms driver will be doing quite admirably at PA duties. None of the PA type stuff that I looked at had an advantage on paper as hard as that may be to believe. The only things close were the PA5100 and the 21's.

The only expenses will be time, effort and build materials.
post #28 of 448
Quote:
Originally Posted by Bill Fitzmaurice View Post

Not at all. EAWs are intended for use in blocks of four or more, which extends the region of flat response far lower, and they're intended for pro-sound applications, which has maximum SPL demand between 50 and 60 Hz. They're not suited at all to HT, but they're not supposed to be.
My pro-sound T48 doesn't look all that impressive with one cab, but a stack of a dozen, typical of a high end pro-sound rig, runs ruler flat to 32Hz.

and if you stack a horn array so large in mouth area that there effectively is no mouth - why do you need to have any depth to it ? you can just stack sealed boxes 1 cu ft each with 12" driver in them for a wall of 100 by 100 subs and get the same effect only it will hit much lower and weigh much less.
post #29 of 448
Quote:
Originally Posted by Ricci View Post

According to the simulation at least, the Lms driver will be doing quite admirably at PA duties. None of the PA type stuff that I looked at had an advantage on paper as hard as that may be to believe

have you tried multiples of drivers like this:

http://www.usspeaker.com/B&C-12nw100-1.htm

lets say 4 of them to 1 LMS.

my instinct tells me you would get much better midbass this way and for your stated ( PA ) purposes that should count for something.
post #30 of 448
Quote:
Originally Posted by Bill Fitzmaurice View Post

Not at all. EAWs are intended for use in blocks of four or more, which extends the region of flat response far lower, and (...)
My pro-sound T48 doesn't look all that impressive with one cab, but a stack of a dozen, typical of a high end pro-sound rig, runs ruler flat to 32Hz.

You have a point here. However i'm sick of pro audio "subs" rolling off at 60Hz, coz that's all they have here. No one heard of proper multiple box usage in this country. If you respect the designer's plans (oh, wait, YOU are the designer), then my hat goes off to you. But the way things are going here... Well, i'd rather have multiple small boxes than multiple big boxes.

@ Ricci, i understand what you're saying now. It's gonna be an interesting build to say the least. I'm mostly interested in its final size - ie, how much of a vehicle will be needed to carry four of them.
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