Combination flare on front (Azura) horn

[limono]

I posted this on AA but I don't count much on responses .It's a little bit unusual .
I wonder if adding an exponential flare from 8" throat(default Azura) to 4" would lower horn cut of frequency or at least help to load driver to 200 Hz.(I mean if I put 150hz (or 100 Hz) into exponential calculator with Azuras 80cm (32") mouth and just use calculated profile up to 8"(170mm) extending horn for about 30cm (12") What kind of results can I expect ?? I aim at 150Hz (200Hz)- 800Hz (1000Hz) bandpass.
I consider B&C 8PE21 pro driver for the task.
Azura 204Hz specs:
Mouth diameter-800mm (~32")
throat -170mm (8")
length -310mm (12,4")
T -0,8

Thanks L

 

[Brett]

The flare rate will define the useable LF limit. Get the 160 and get Martin to make it as long as you need.

I still wanna try one of these (A160 0r 204) with an 8" coax.

 

[limono]

Well , I have Lowther DX4 and had Fostex 208 and I think I don't like this approach. I'd like to convert shallow Azura horn into normal mid-bass horn with bandpass 150-200 Hz -1000Hz .This horn is to shallow to support 150-200 Hz (I heard it drops like a stone after cut-off frequency ) Dr.Edgar (and others) states that tractrix profile doesn't load to the cutoff frequency.Thats why I thought of adding 12" exponential part of throat lowering its diameter from 8" to 4".I may add tractrix extension flare . It will also help to kill HF response of this horn and avoid high order crossover slopes ) I'd like to use B&C 8PE21 driver. Is there a way to simulate this???
I agree that ordering or building a new horn would be the best but round mid-bass horn is very,very expensive (labor intensive ) but if anybody has one to trade for "Full range Azura 204hz' I'm all in.
Thanks, L

 

[Brett]

Well , I have Lowther DX4 and had Fostex 208 and I think I don't like this approach.

Do you mean you used them in boxes or in an Oris or Azura? I heard some Lowthers in an Oris 150 several years ago and recall being impressed, whereas I'd loathed Lowthers before. I still don't like them all that much, so I thought a small coax might do it well.

I'd like to convert shallow Azura horn into normal mid-bass horn with bandpass 150-200 Hz -1000Hz .This horn is to shallow to support 150-200 Hz (I heard it drops like a stone after cut-off frequency )

Most flares do . The LeCleac'h seems to be closest to a hypex in profile and should support loading down to near cutoff. The traces on the Azura site support 200Hz as being useful with Lowthers and CD's.

Dr.Edgar (and others) states that tractrix profile doesn't load to the cutoff frequency.Thats why I thought of adding 12" exponential part of throat lowering its diameter from 8" to 4"..I may add tractrix extension flare . It will also help to kill HF response of this horn and avoid high order crossover slopes )

IME trax flares come on about 1.41x flare freq.
Mixing and matching flare profiles may not work terribly well. Martin can make a 160 or 204 extend using the correct flare rate all the way down to 1". Or wherever you ask him to put the flange.

I'd like to use B&C 8PE21 driver. Is there a way to simulate this???

I asked this on AA HE and JMMLC said to do it as several hypex sections, but never detailled exactly how to do it. Perhaps you could email him after the holidays and he would elaborate.

I agree that ordering or building a new horn would be the best but round mid-bass horn is very,very expensive (labor intensive ) but if anybody has one to trade for "Full range Azura 204hz' I'm all in.
Thanks, L

Time consuming, yes. If you plan it well, no. MDF is cheap.

 

[limono]

Bret
First I had FE208 than I upgraded to DX4 (both in Azura 204) with Klipshorn Bass bins. I was never very happy so I Enabled dx4 and it doesn't work in front horn at all.
Going for Oris like solution wasn't very smart move on my part as I heard them 3 times on audio shows and never was very impressed but at that time there was so much positive noise on this in all forums that I thought something must be wrong with me 😀 (Live and learn )
Actually sticking with original flare and just making extension to 4" throat is not a bad idea. My initial thought was that 80cm mouth could support lower than 200hz cutoff. .I'm going to email Martin anyway as I'd like to order his 550hz horns for mid-range (either altec 288c or JBL2470) the only problem me being poor and totally broke at the moment Current dollar exchange is not helping neither.

 

[Brett]

What didn't you like about the Lowther +204 combo? Where were you crossing?

Martin may make an extension for you. Or he might not. However, get the spreadsheet from JMMLC's site and calc out the flare and make something. I'd try a conic extension made from cardboard first. Cost is nearly zero and will give you an idea if you're heading in the right direction.

 

[limono]

What didn't you like about the Lowther +204 combo? Where were you crossing?

I used welborne labs active /passive crossover ~200-250 Hz . Mid-bass was non existent , mushy, ill defined and upper mids were getting on my nerves. My room is not small 21'x21' but 10' dividing wall (open kitchen) makes the speaker placement 11' corner to corner apart . With Klipshorns in the corners there is no other option as put Azuras on the Klipshorns. I have mono EV Patrician iV in one corner and its nearly as irritating as Azura /Klipshorn . To be honest I lent those Azuras to a friend with DX3 and huge place and in the middle of the room there was some magic in performance . Midbass was week too and highs recessed but he said that he never heard such "uncanny" performing speakers . To each his own.
I will build some prototype flares .I think that in the beginning of a throat all flares are similar and in the bandpass of 200-1000 it won't matter as much as the mouth size and horn length .

 

[Frode]

I don't know how to sim the combination flare, but I did som sims with the flare used in the Azura 204. Here we go:

Original Azura 204 with ~6.7" throat, length ~12.2".

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

4" throat, 17.6" length

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3" throat, 20.6" length. This is included as the grey curve in the two previous plots.

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

Frode

 

[limono]

Frode
Thanks so much for the simulations ! Seems like going for extension throat is not such a bad idea . Ones I get the drivers I start experimenting with the flares .Anybody has an experience with Altec 288c VS Jbl2470 ??
Regards, L

 

[Brett]

Frode, what driver did you use in those sims

 

[Frode]

Frode, what driver did you use in those sims

I used the B&C 8PE21.

Frode

 

[Brett]

I used the B&C 8PE21.

Frode

Thank you. Looks like I have some more simming to do. Hornresp gave me lots of difficulty when I tried to model the Azuras a while back.

 

[Frode]

I haven't had any problems with Hornresp, but I'm still learning to use all the functions. It's a nice tool.

Frode

 

[limono]

Frode
Could you simulate 8PE21 in exponential horn with the mouth size of 80cm and 4" throat? Also in your previous simulations I'm not sure how to interpret those spikes at 2khz 4khz and if they will be a problem to deal with in real life application.
Regards, L

 

[Frode]

First of all I would say that I'm NOT an expert in horn design. I've just played around with Hornsresp and software/formulas found at the Single Driver Website.

The spikes are resonance in the back chamber. In the sims I've used an 8 cm back chamber depth which gives a wavelength of 4300Hz or half a wavelength at 2150Hz. I'm not sure how much this affects the sound, but I guess it could be reduced/avoided by using non-parallell walls in the back chamber.

A 140Hz exponential horn would have just below 80cm mouth diameter and 80 cm length. Here's a sim:

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

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

According to one of the formulas at the Single Driver Website, the 8PE21 would like a throat size of ~40cm^2 or 2.8" diameter. Then it would look like this:

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

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

The two compared, with the 4" throat in black:

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

Frode

 

[Frode]

I changed the input voltage on the 2.8" throat horn in order to make the level at 300Hz the same. It looks like this(2.8" in grey):

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

Frode

 

[GM]

Greets!

Some stuffing or lining of the walls in the rear chamber takes care of any horn HF resonances and just click 'yes' when asked if you want resonances masked to see its effect. ~0.2 lbs/ft^3 density is usually sufficient unless the chamber is very deep or wide, so golden or acoustic ratios is a good plan. Excessive damping will reduce its gain BW and in case you don't know, Hornresp only shows the horn's BW, not any of the driver's HF BW and how the horn's throat reactance and directivity affects it.

GM

 

[Frode]

Greets!

in case you don't know, Hornresp only shows the horn's BW, not any of the driver's HF BW

GM

Hi Greg!

Do you mean that the HF is only a function of the horn? When I change the Le of the driver, the HF response also changes. And two different drivers on the same horn gives different HF response.

Frode

 

[GM]

No, I mean the horn system's (horn gain BW + driver's theoretical on-axis pistonic BW) isn't shown as it is in MJK's WS.

Yes, for a given horn design, the horn's HF response will be affected by the driver's HF mass corner (2*Fs/Qes) and its rising inductive response, so both these should be taken into account when designing an optimum gain BW horn.

GM