Hornresp

Has anyone modeled Just he top of the Altec A7(825) cab.

I simmed the compression loaded ones I use to do in MJK's original FLH WS to proof its overall accuracy. It has maybe a bit too much built-in acoustic smoothing though for some of the folks here though. I'm busy with house repairs ATM, but as time permits I'll load them into HR to see if they look as ugly ;) as Lars indicates. For sure, me and the folks I did them for thought they sounded pretty good at the time [~1968-1975].

GM
 
djn,

I have done the 828 together with 416-8B. Not a pretty sight! What driver do you have?

"not a pretty sight" How so? I will be using the Lambda TD15x drivres. interestingly....the T/S of the TD15x is VERY VERY similar to the 416.


I simmed the compression loaded ones I use to do in MJK's original FLH WS to proof its overall accuracy. It has maybe a bit too much built-in acoustic smoothing though for some of the folks here though. I'm busy with house repairs ATM, but as time permits I'll load them into HR to see if they look as ugly ;) as Lars indicates. For sure, me and the folks I did them for thought they sounded pretty good at the time [~1968-1975].

GM

Thanks GM, much appreciated. I also have 4 really good subs to fill in the bottom end.

I will be using the red Edgarhorn and Heil in this pic on these cabs. I am moving to a smaller place and the big scoops are too big for my new room.
 

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I simmed the compression loaded ones

Hey GM,
What, compression? Do we mean the same cabinet? Didn´t everything sound great for a couple of years after Woodstock;)? Yes, it is a joke so don´t mind:)! I for some reason liked the dreadful production Klipshorns.

djn,
About not a pretty sight they aren´t! Needs smaller box other porting and maybe another flare in the horn.

OK, here is what comes out of HR. All dimensions aren´t exact but good enough. On-axis is acceptable.

There is an interesting article somewhere about Exemplar.
 

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:cool::)


About VOTT, tune it to ca 40Hz. With 1,8cm baffle thickness it will be something like 200cm2.

Lambda TD15x

djn,

where are the T/S parameters? They are not AE´s site. This is all there is:

FS: 23.2Hz
Qts: 0.28
Vas: 467L

Estimated the other values in course sim and I guess it is better to check the drivers from Great Plains. The main reason is TD15x´s high cone mass.
 
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:cool::)


About VOTT, tune it to ca 40Hz. With 1,8cm baffle thickness it will be something like 200cm2.



djn,

where are the T/S parameters? They are not AE´s site. This is all there is:

FS: 23.2Hz
Qts: 0.28
Vas: 467L

Estimated the other values in course sim and I guess it is better to check the drivers from Great Plains. The main reason is TD15x´s high cone mass.

The T/S are kind of hiden on the site. When you go to a particular driver, there is a "down load plans" in the bottom right corner. Click that and you get a page with a link on it to there forum. Click that link and you get a list of all there drivers, click the driver you are looking for and you get a page with all the T/S. Here is the T/S for the TD15x

TD15X- 8ohm
Fs 23.2 Hz
Qms 3.82
Qes 0.31
Qts 0.28
Vas 467 Liters
Cms 0.45 mm/N
Mms 105 grams
Sd 855 cm2
Rms 4.0 Kg/S
Bl 16.7 T/m
Re 5.6 ohms
Z 8 ohms
Le 0.3 mH
Pe (max) 500 Watts
Pe (transient) 1000 Watts
"no" 1.82 %
1WSpl 94.8 dB
Linear Xmax 14 mm (peak)
Mech Xsus 20 mm (peak)
 
"VOTT" is for the whole cab. It is somewhat troublesome to sim as we can not combine Off-axis response with Combined(shown here). Combined is only with Constant Directivity.

Unfortunately the AE speaker is not suitable if we should believe the sims. The low mass-corner makes it perform bad in the midbasshorn/upper register. Nor will it perform well this type of basscab in the lower range.
 
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Thanks Lars. I was planning on just using a vented cab with the Lambdas, but these half VOTTs came my way and I thought I give them a try.

Maybe I will still use them just to get a real world measurement and see how them compare. I don't have vented cabs at the moment anyway so I'll see what happens.
 
Here is a pic of the actual horn that I have. I am not sure how to estimate the volume with those curved walls. My best guess is 1.5 cu ft??? The back volume is everthing behind the horn flare so I can close off as much as I need to achieve the best results.

I will be using them standing tall unlike the picture. I will be crossing over to the midhorns from 500 to 700hz
 

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Ok, I ran the cut down A7 horns in HR and here is what I came up with. Can someone check my math here. I am really not good at this.

The SPL responce is just a bump. Can that be flattened out or does is not take into account the higher freqs the driver will produce?

I will be crossing these over at 500hz but the SPL responce shows it is near 10db down at 500hz. Is that right or is that where the horn effect is down?
 

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Attached files to load into HR are the compression loaded 416-8A and AE TD15X in A7 horn sections. Back when I was doing these conversions I just kept reducing the rear chamber's Vb until I found the flattest impedance, so each one was custom tuned. This included blocking off the horn cavities and filling them with expanding Styrofoam, though for HIFI/HT, filling them with sterilized sand, kitty litter/oil dry or similar is preferred. The rest was filled in as required with scrap wood/whatever and fine tuned with R-19 fiberglass insulation wadding.

To ~ mirror the measured flatness of the impedance plots though, I had to increase MathCad's rear chamber's net Vb for HR's to match up, so I'm guessing this is where the acoustic smoothing/whatever comes into play, but again, each cab ideally needs to be custom tuned.

To get a simple pistonic horn + driver summed response, use TOOLS/Directivity/Response and 0 degrees off axis. The Altec's is 'in the ball-park', so I assume the AE's will be also, i.e. a poor driver/horn match for compression loading.

Of course, you can use the full space to lower tuning and use EQ to smooth out the leftover 'bump', but power handling is dramatically reduced.

GM
 

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