Eminence Delta Pro 18 A in prism sealed 150 liters

[academia50]

Do not be impatient, there are other prorities and first things first ...

 

[academia50]

I found this SPL calculator.

After entering the data of this project, the result is excellent, but a question arises here.

Within the values to be introduced, the sensitivity of the speaker refers to 1 W / 1m) but, and the gain or loss of the cabinet?
It is not the same a bass reflex, horn or sealed, correct ?

Thoughts ?

 

[David Morison]

I found this SPL calculator.

After entering the data of this project, the result is excellent, but a question arises here.

Within the values to be introduced, the sensitivity of the speaker refers to 1 W / 1m) but, and the gain or loss of the cabinet?
It is not the same a bass reflex, horn or sealed, correct ?

Thoughts ?

I think the writer of that tool expects this to be used for finished speakers with a flattish frequency response, thus one can expect there to be one sensitivity value that is a reasonable approximation of the whole speaker's response level.

Your project is a bit different in that you are accepting a loss in sensitivity as frequency decreases, so if I were you, I'd input whatever value corresponds to the expected sensitivity at the lowest frequency of interest rather than the nominal sensitivity which would only be relevant at higher frequencies. I thin that will be about 86dB for one speaker in your case.

HTH,
David.

 

[academia50]

I think the writer of that tool expects this to be used for finished speakers with a flattish frequency response, thus one can expect there to be one sensitivity value that is a reasonable approximation of the whole speaker's response level.

Your project is a bit different in that you are accepting a loss in sensitivity as frequency decreases, so if I were you, I'd input whatever value corresponds to the expected sensitivity at the lowest frequency of interest rather than the nominal sensitivity which would only be relevant at higher frequencies. I thin that will be about 86dB for one speaker in your case.

HTH,
David.

Sure help, thanks !

I will make the new calculations within the range I need, and upload them again.

I forgot the link, here goes :

Peak SPL Calculator

 

[academia50]

Well, here the final results, two subwoofers of 18 inches, sealed cabinets of 150 liters and located in two corners.
Listening point 6 feet (4 meters).
I have drawn a graph for a quick comparison of the SPL obtained at 20,30, and 40 hertz, with 1 Watt and 250 Watts ....

 

[academia50]

The rest ...

 

[academia50]

Please, read:

40 hz 1 Watt , 92.80 Db at 6 ft.

I'm sorry, there was an error in the graph ...........

 

[academia50]

I built a fully braced tansmission line last week in 2 days(without paint time) and tested.

Well, we do not all have the same skills, congratulations for it !

All of these tiny braces etc will do very little, the box sides aren't that big and you're using low power anyway so the box flex will be minimal as is with such a thick baffle. The triangular braces would probably be plenty already.

The idea is to go to more power with DSP if the result is not as expected.
That's why I'm building the strongest possible box.

Also, the resale value will be better, would you be interested ?

 

[academia50]

At last the sun has come back and today I advanced preparing the parts for the last reinforcement.
We had two simultaneous catastrophes, one is very well known here, it occurs minimally once a year, during a week followed by the city of Buenos Aires, fall on her the famous "sudestada", the sea wind coming from the south- east, works as a plug to the natural drainage of the Rio de la Plata, accompanied by copious rains and electrical storms, also raising the level of the river flooding the surrounding coasts .....
But the most worrying was to cope with this natural climatic phenomenon, accompanied by another unprecedented event, a tremendous blackout of electric power (never seen here, remember when something similar happened that affected the USA and Canada?).
So this time I have a good excuse for the people here who are asking me to hurry up the work!
How do you expect me to work under these conditions ?

Massive power outage hits Argentina, Uruguay

Apagon historico: otros cortes masivos de luz en el mundo

 

[academia50]

I have finished the last reinforcements in the interior area of ​​the cabinet.
I was thinking that placing the speaker on the outside of the baffle panel will help to compensate a bit for the excess reinforcements. Anyway, a lot of stuffing will return things to their place, the big question is:
How much exactly? I think I remember an article about how to calculate it, but I'll have to dig into " Markers " of Win .....
If someone provides a link, it will be very appreciated

 

[freddi]

here's an article by the late Tom Nousaine

Polyfill stuffing in car audio subwoofer systems

 

[academia50]

here's an article by the late Tom Nousaine

Polyfill stuffing in car audio subwoofer systems

Thank you very much freddi, that will do.
The example of 5.1 cubic feet is practically the volume of this cabinet ....

I have read something that woke me curious, many people prefer to leave the speaker compartment free, without polyfill there.
What would happen if I do that and compensate for that with more compact filler in the middle and above ?

Is there any benefit ? The only thing I find is that the polyfill can interfere with the cone if I put stuffing down, which can be avoided by putting a net, etc., but I would prefer not to do that ....
This concern is because the basket of this speaker is quite open to be 18 inches !

 

[freddi]

perhaps there's an inexpensive plastic netting which could be put in place or right over the magnet and basket which would keep damping material from directly coming in contact with the cone. (you've done a great job of curring and bracing those cabinets)

Steel "chicken wire" probably would work and help space damping material away from the speaker - if that's desirable.

Amazon.com : BirdBlock 604 Reusable Netting for Bird Protection, 7 feet x 20 feet, Black : Bird Netting : Gateway

 

[GM]

FWIW, the pioneers used cheesecloth: NGUYENMANHTOAN (nguyenmanhtoan) on Pinterest

GM

 

[academia50]

perhaps there's an inexpensive plastic netting which could be put in place or right over the magnet and basket which would keep damping material from directly coming in contact with the cone.

Yes, I thought about those networks but maybe it would be better to wrap the filling directly in pillow mode in that compartment.

(you've done a great job of curring and bracing those cabinets)

Thanks for that, it gives me the strength to finish ... ( before they ask me for a divorce ! ) .........proposal that maybe I would not have missed a few years before

Steel "chicken wire" probably would work and help space damping material away from the speaker - if that's desirable.

I used it in my vintage JBL when the kids put their fingers everywhere and then I took it out ....
I will use something similar but of plastic when I make the guards for my DTQWTII, many things are accumulating ....

 

[academia50]

FWIW, the pioneers used cheesecloth: NGUYENMANHTOAN (nguyenmanhtoan) on Pinterest

GM

Thanks for the link, GM, but I think I will do as I mentioned above

 

[academia50]

Wow, it seems that people have seen that I used marble for my subwoofer and got excited ! ......



Ekta-Grande_Piero

 

[academia50]

Today in the morning I went to buy the filling material (polifyll) and in the afternoon I calculated the real volume (net) of the cabinet, that is, discounting everything that occupies space within the gross measurements of it.
The calculations are very encouraging, the final volume is very close to the statement in this post, and I can still increase the virtual volume.
So, I will be below Qtc 0.707, that is, an underdamped cabinet that is what I need.

Soon more details .....

 

[academia50]

So, I will be below Qtc 0.707, that is, an underdamped cabinet that is what I need.

I meant overdamped

I sorry ...

Sealed enclosure explained in detail and calculator | Audio Judgement

 

[academia50]

Well, it seems that neither over nor under, I'm finally closer to "critically cushioned" .....
Gross volume of each cabinet (external measurements):
150 liters
Net volume (internal measures - free interior):
121 liters
Total internal reinforcements, marble block, etc:
16.5 liters
Final : 104.5 liters

Then, I will have to put a lot of filler material inside to add the maximum virtual volume.
Will it be possible to reach 25%?

Thoughts ?