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give me a suggestion for an 8" sub

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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2020 at 7:20pm
If the amp module is 300 watts @ 8 ohms, you will type in 300 watts total in the Pe for your isobaric design. This will tell you how much dB output you can expect based on the Maximum Acoustic Power chart.

At the same token, if the reflex cabinet is getting (hypothetically speaking) 500 watts @ 4 ohms, you will type in 500 watts total in the Pe for your reflex design.

The Maximum Acoustic Power Chart will tell you which design will be the loudest based on how much power you are feeding the cabinets at the given load. In addition to how much dB you can achieve based on the power fed to the drivers at the given impedance load, the chart will also determine if power compression or xmax limitation will become a problem as you move further down the frequency range. 

Best Regards,
Elliot Thompson
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2020 at 9:16pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

If the amp module is 300 watts @ 8 ohms, you will type in 300 watts total in the Pe for your isobaric design. This will tell you how much dB output you can expect based on the Maximum Acoustic Power chart.

At the same token, if the reflex cabinet is getting (hypothetically speaking) 500 watts @ 4 ohms, you will type in 500 watts total in the Pe for your reflex design.

The Maximum Acoustic Power Chart will tell you which design will be the loudest based on how much power you are feeding the cabinets at the given load. In addition to how much dB you can achieve based on the power fed to the drivers at the given impedance load, the chart will also determine if power compression or xmax limitation will become a problem as you move further down the frequency range. 

Best Regards,




this is the driver ts page, the right column is the ts calculated for the number/connection type. ( 2 in series) 

I'm thinking that my assumption so was correct because, i will not put 600w in it...
the amp is the same for reflex and this test: 300w@8ohm (in cant be load at lower imp) so i choose 2 speakers at 4 and series link...
so maybe is about the rms of the speaker, or i didnt understand?

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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2020 at 10:44pm
Originally posted by _Natty_ _Natty_ wrote:

Originally posted by Elliot Thompson Elliot Thompson wrote:

If the amp module is 300 watts @ 8 ohms, you will type in 300 watts total in the Pe for your isobaric design. This will tell you how much dB output you can expect based on the Maximum Acoustic Power chart.

At the same token, if the reflex cabinet is getting (hypothetically speaking) 500 watts @ 4 ohms, you will type in 500 watts total in the Pe for your reflex design.

The Maximum Acoustic Power Chart will tell you which design will be the loudest based on how much power you are feeding the cabinets at the given load. In addition to how much dB you can achieve based on the power fed to the drivers at the given impedance load, the chart will also determine if power compression or xmax limitation will become a problem as you move further down the frequency range. 

Best Regards,




this is the driver ts page, the right column is the ts calculated for the number/connection type. ( 2 in series) 

I'm thinking that my assumption so was correct because, i will not put 600w in it...
the amp is the same for reflex and this test: 300w@8ohm (in cant be load at lower imp) so i choose 2 speakers at 4 and series link...
so maybe is about the rms of the speaker, or i didnt understand?




I am going to be straight forward with you. I do not have leisure time like I did before. The last thing I want to happen is, you asking me question in which, I won't be back in Months to read.

With that being said. Post a photo of both designs using the Maximum Acoustic Power Chart (both getting 300 watts). It will allow me to see what is the dilemma you are having difficulty understanding when, using Harristech software.

Best Regards,
   


Edited by Elliot Thompson - 18 December 2020 at 10:45pm
Elliot Thompson
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2020 at 11:11pm

first is isobaric,
second double reflex
third the single one powered with same thing
if i put 300 in pe, net will 600w, just say yes you are wrong in case Cry
I set 300w in the costum amplitude response chart.



and this should be what we looking for:



Edited by _Natty_ - 18 December 2020 at 11:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VECTORDJ Quote  Post ReplyReply Direct Link To This Post Posted: 18 December 2020 at 11:29pm
You mean 18 inch sub????? 8 inch sub....no.....8 inch makes nice mids. A 8 could go to 30 hz but will have low output. If it is too Loud You are too old.....

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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2020 at 1:24am
Originally posted by _Natty_ _Natty_ wrote:


and this should be what we looking for:


This is all that matters.

The Yellow Line is already at its limits in terms of Maximum Output @ 40 Hz.

The Blue Line has entered power compression within the 110 Hertz Range. It is the worst out of the three.

The Orange Line hits power compression around 39 Hz but, at least it approaches the lowest frequency as the Yellow Line and, is +6 dB louder than the Yellow Line from 100 Hz - 30 Hz. 


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Elliot Thompson
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2020 at 12:01pm
I never analize this chart, and i thanks a lot  for letting me understand a new thing.

I forgot to make a description for the graph:
the yellow line is the compound cab, the orange is the double reflex, the blue is the single speaker cab analyzed at the beginning of the post by the meauserement too.

If i well understand from the yellow to the orange difference in almost the same range 30-100hz (where i put my attention for this application) is 6db, thats is a world in this scenario.

I didnt understand how do you catch the " power compression" hit, is where the graph start to raising again after a valley? 

I'd like to mention again the starting point of the post, ive 2 speakers that im listening from alomost 1 month but i cant take a final decision because boht have big pros and cons...
even after inviting at home some experts friends the doubt remains, because when u listen it you heard a deep one but in too much big box against a damn lighter box with some very nice musical notes but less lower...
 as suggestion ive tried to simulate the compound enclosure to try to scale up the big boxes, but it seem that with the help of @Elliot Thompson ive understand that this solution seems not very performant...
do i miss something? :D im at the start again :D

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DMorison View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2020 at 2:10pm
Power Compression is the name for the behaviour of a driver when we start to push it near its limits.
Basically, instead of the driver keeping on getting louder in a completely linear manner as we turn up the input level, there is a curve of diminishing returns.
The main mechanism for this is heat - as the power level goes up, the voice coil heats up and its impedance therefore rises - what was a nominal 4 ohm driver may end up a 6, 7 even 8 ohm driver when we push it hard. This means that at a given drive voltage from the amp, the driver draws less current and it therefore generates less force.
The other mechanism, and this is the one Elliott & your graph are referring to, is over excursion. (I don't know BassBox well, but I assume there's a dedicated graph showing excursion available - all other speaker modellers include this anyway.)
All drivers have a parameter called Xmax, which is the maximum distance the coil can move while keeping a reasonably linear response to the input signal. This is separate from the nominal power handling of the driver.
The "scooped" region on the last graph you show, most obvious in the 50-110Hz region of the blue trace, shows where that driver would exceed its Xmax at your stated input power - so it won't actually get as loud in that frequency range as it could at other frequencies.
HTH,
David.
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_Natty_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _Natty_ Quote  Post ReplyReply Direct Link To This Post Posted: 19 December 2020 at 9:48pm
Originally posted by DMorison DMorison wrote:

Power Compression is the name for the behaviour of a driver when we start to push it near its limits.
Basically, instead of the driver keeping on getting louder in a completely linear manner as we turn up the input level, there is a curve of diminishing returns.
The main mechanism for this is heat - as the power level goes up, the voice coil heats up and its impedance therefore rises - what was a nominal 4 ohm driver may end up a 6, 7 even 8 ohm driver when we push it hard. This means that at a given drive voltage from the amp, the driver draws less current and it therefore generates less force.
The other mechanism, and this is the one Elliott & your graph are referring to, is over excursion. (I don't know BassBox well, but I assume there's a dedicated graph showing excursion available - all other speaker modellers include this anyway.)
All drivers have a parameter called Xmax, which is the maximum distance the coil can move while keeping a reasonably linear response to the input signal. This is separate from the nominal power handling of the driver.
The "scooped" region on the last graph you show, most obvious in the 50-110Hz region of the blue trace, shows where that driver would exceed its Xmax at your stated input power - so it won't actually get as loud in that frequency range as it could at other frequencies.
HTH,
David.

Thanks David. 
The blue single speaker reach is xmax at 41hz that is the also the Fb of the cabinet that can be even seen on the measurement at the beginning on the post.

The yellow (compound, just simulated), and orange (double reflex, light purple in the meas) have almost the same xcursion graph, with no problem untill 23hz.

Dont blame too much the poor blue one, because in 17l, delivers some real musical bass, yes just till 41hz CryCryCry and thats where doubt comes from otherwise it sounds louder and cleaner than the double with the same power, but with just one unit(cheaper). 

In this legaue (8" under 200eu) I didnt find a lot of competitors.

for some strange reason i cant see the image anymore so i upload it again, just in case, the dark purple is the single speaker cab:


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Post Options Post Options   Thanks (0) Thanks(0)   Quote JonB67 Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2020 at 10:22am
Does it have to be 8 inch drivers?

Have you compared your double 8 to a single 12? Worth simmimg one up to compare.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 20 December 2020 at 9:16pm
Check out the SWR-8D4.

I've had excellent results with this in small reflex cabinets, down into the 30s. 

Dual VC too if that helps too.


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