Help to simulator double bass reflex

[superlian]

Help to simulate double bass reflex

Hi

Is there anyone who can help me to simulate a double bass reflex to Lowther PM8A 15 Ohm with silver voice coil?


Fs 58 Hz
Qts 0,36
Vas 46,2 l (1,63 cubicfeet)
SPL 95,5 dB 1w/1m
Re 12,7 Ohm
Qes 0,39
Piston diam 164 mm (6,46 in)
SPL 93,5 dB 2,83 V
CMS 0,74 mm/N
Le 0,47
Qms 5,1
BL 11,1
N(0) 2,2%
MMS 10,3 gr

 

[Scottmoose]

Just to confirm, when you say 'double bass reflex' are you referring to the Fostex style of box (DBR) or the Augspurgur type double chamber reflex (DCR)?

 

[superlian]

I was thinking about the Fostex style.

But i appreciate suggestions

 

[Scottmoose]

I'll have a look. To be honest, I don't personally find the Fostex type DBR to be especially effective; I'd suggest you look at the Augspurger type DCR or an MLTL variation before committing to the DBR type. Oddly enough, I worked up a DCR for a PM6A only last week; sent the sketch to Dave a few days back to look over. Will see if this unit may be an alternative with a few changes.

 

[freddi]

superlian - hornresp can simulate DBR by using the ABC model and shutting down a port by very small area and very long length input. Augspurger's dual chamber reflex = "ABC" type in honresp.

hi Scottmoose - have you seen these pages? what if anything might it accomplish vs MLTL of equal volume ?

Multiple-Degree of Freedom Cavity Resonator Diary

 

[Scottmoose]

I have indeed.

As-is -depends. Most that I've looked into over the years have fairly characterful alignments but that's more a question of individual design rather than the broad concept itself. On paper, the more chambers you have, the wider the BW you can load so the lower the average driver excursion / the higher the power handling should be. No bad thing in itself, but it usually comes at the price of higher GD and increasing difficulties of maintaining a good alignment, which is why I tend to like MLTL variations or DCRs, since it's usually possible to get some decent loading above the nominal Fb in the main acoustic 'power band', while avoiding too many other issues. I do have some interesting varitions on the theme that Dave & I are working on at present though.

 

[Scottmoose]

Right, I've had a quick gander at the PM8 in the DCR design I mentioned above. It's not quite a drop-in, but with a minor adjustment to tuning (it would be useful to know what the amplifier is), it should work OK. If you're interested, fire me an email.

 

[superlian]

YGM

 

[freddi]

here's some piddling of a DCR of 45 liters size - (I would put it in a Karlson FWIW)

 

[freddi]

superlian - if you take a given DCR and reverse the chamber volumes then the response can be quite different. You might run Scottmoose's design through hornresp to see how close it comes to his simulation. Hornresp has chamber length input which affects the outcome.

 

[David McBean]

hornresp can simulate DBR by using the ABC model and shutting down a port by very small area and very long length input.

Hi freddi,

I'm intrigued .

Wouldn't it be easier to just use the actual DBR loudspeaker configuration option?

Kind regards,

David

 

[freddi]

(blush) - that was an old sim entry with his Lowther spec - plus forgot !!

 

[freddi]

for the OP in case he wishes to simulate the type

David - I've likely asked before but is there a way so simulate a 3-chamber bass reflex with hornresp ?

 

[David McBean]

that was an old sim entry with his Lowther spec - plus forgot !!

Ah, now I understand - thanks .

 

[David McBean]

David - I've likely asked before but is there a way so simulate a 3-chamber bass reflex with hornresp ?

Hi freddi,

I'm not sure how you define your 3-chamber bass reflex topology, but if it is simply a third ported chamber added in series to a conventional DBR system, then such a design could be modelled in Hornresp as shown in Attachments 1 and 2.

Note that this particular design has brought to light a bug in the new system model schematic, which hopefully will be fixed in the next update .

Kind regards,

David

 

[freddi]

Thanks David. FWIW I was thinking of extending the dual chamber reflex type with one more chamber. A non tech late friend did that as he said "designed on acid" for two five inch and two 1" domes - it sounded very good

 

[freddi]

Its interesting to see what happens in your example when all ports are shortened from 10cm to 1.8cm

 

[Scottmoose]

Thanks David. FWIW I was thinking of extending the dual chamber reflex type with one more chamber. A non tech late friend did that as he said "designed on acid" for two five inch and two 1" domes - it sounded very good

3CR-Ti | Parts Express Project Gallery

 

[David McBean]

3CR-Ti | Parts Express Project Gallery

That's definitely one for AkAbak .

 

[freddi]

that's interesting - might the 2-1-1 ratio of chambers with all equal ports be something rather universal ?

not sure what the cascaded extension of the DBR can do