Small La Scala Tutorial for noob

[sumotan]

Hi Guys
Came across this article it being scale down interest & intriques me. All that I could find is that it only handles 500 hz down to 100 hz. Don’t know what woofer was used. My question is, is it the woofer choosen that dictates the upper cut off frequency or is it the folds & the cut out slot that dictates it ?

Thank you all

Sorry Guys, Here’s the link : https://volvotreter.de/downloads/lascala10inch.pdf

 

[zobsky]

The horn geometry, in this case

 

[moray james]

If you are looking to squeeze a little more top end response you could add corner reflectors as used in the Peavey FH1 (these are at the end of the first section of expansion where the wave front turns from horizontal to forward) but you will not gain a lot. What is your intend end use with this home HiFi or PA?

 

[sumotan]

Hi Guys
Thank You. Yes Moray thinking for using if for home. The size of this bin makes it managable. Yes would be great if I can move up the cut off frequency of 500hz.

 

[GM]

Don’t know what woofer was used.

Have you tried asking him?

GM

 

[sumotan]

Did send an email GM but no reply yet

Thks

Hi Guys A little advice. After searching through Google I managed to find a guy whose using the Goldwood GW-1058 for this bass bin. Problem for me is shipping cost. Was looking at some Eminence 10 inch woofer which I can purchase locally & would appreciate if you guys can recommend a version that I can use in replacement.

Thank you kindly

Sorry guys, just found the Eminence Basslite to be the closest match to the GW-1058 but in Eminence specs it says not applicable for seal box. Am I missing something, thought that low QTS is good for seal box .

Thanks again

Hi Guys Managed to get in touch with the designer of this Mini La Scala. I was seeking for his advice about upper crossover frequency & this is the formula he gived : 2x Fs/Qes. Now I’ve tried this on a number of 10 inch woofers & none of them can make it to 400 hz. All the while I thought upper frequency was dictated by the design of the woofer & we just work within these parameters. Question pls : Is this formula specific to or does it applies to all horn loaded bass bins ?

Thank you all

 

[GM]

Sorry guys, just found the Eminence Basslite to be the closest match to the GW-1058 but in Eminence specs it says not applicable for seal box. Am I missing something, thought that low QTS is good for seal box .

Thanks again

??? They recommend it, but is medium Qts: https://www.eminence.com/pdf/Basslite_SC10_16.pdf
GM

 

[sumotan]

No GM found out that he uses an Eminence EM 10-100.
The Goldwood was what I found Googling that someone was using it in this enclosure.

 

[GM]

All driver box loading bandwidth [BW] is defined by its lower, upper mass corner per T/S including horns as proven by both D.B. Keele and Prof. Marshall Leach: http://www.xlrtechs.com/dbkeele.com...Preprint) - LF Horn Design Using TS Paras.pdf

Flc = Fs*Qts'/2

Fhm = 2*Fs/Qts'

Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

Note that Prof. Leach chose to use Qes' in lieu of Qts' in his similar paper: https://leachlegacy.ece.gatech.edu/papers/HornPaper/HornPaper.pdf

I added the series resistance since it can be significantly raise Qes/Qts, narrowing box loading BW when powered by SET tube or similar.

GM

 

[GM]

No GM found out that he uses an Eminence EM 10-100.
The Goldwood was what I found Googling that someone was using it in this enclosure.

Then why the Basslite question?

Anyway, no [EM] 10-100 at Eminence, though did find this, which gets 'close enough' to 400 Hz based on Qes: www.selfmadehifi.de

GM

 

[sumotan]

Thank you kindly GM for the advice . I did find some info on the EM10-100 but not detailed FS 100hz. Think it might be an old Eminence. So basically I should be looking for woofers with very high Qes ?
Question pls: will the frequency in this box not go higher even if I set the electrical XO at say 600 hz ?

Thank you again

 

[freddi]

due to various problems - then winter with no heat in my big room (to save $), I've not yet loaded my "baby" Belle. It should run ok with my 12pe32 or Kappa12a. That's a Klipsch K700 horn (from Heresy I) sitting on top for size comparison. The initial problem was with a thin spacer warping when trying to load a speaker - there has to be something to keep the cone from hitting the throat plate.


A Question - - GM, when using hornresp and looking at the directivity of these little midbass, its typical to see a predicted on-axis rise of 7dB or more vs "flat" response. In practice - does that happen? (didn't see that with the 100Hz "hypex" Edgarhorn and 2220H on-axis outdoors) What I think may have happened was it was "flat" on axis and would have dropped that much off axis at a certain point. Maybe its case by case ?

Here's how hornresp shows a horn scaled roughly from John Inlow's drawing of his 135Hz horn. The back chamber is pretty tight
so M151's xmax would not be exceeded at 40v (it might just burn up - hahaha)

 

[GM]

Thank you kindly GM for the advice . I did find some info on the EM10-100 but not detailed FS 100hz. Think it might be an old Eminence. So basically I should be looking for woofers with very high Qes ?
Question pls: will the frequency in this box not go higher even if I set the electrical XO at say 600 hz ?

Thank you again

You're welcome!

The way it works is one needs a really low/'powerful' Qes/Qts for the HF [~0.1] since each octave is so wide and horns can only do ~three octaves and as we move down in frequency it increases [progressively 'weaker' motor] because the throats, horn need to be bigger due to increasing WL size, narrower BW in three octaves; so yes, down low where the horn is only covering a narrow BW, then no need for much HF extension = high Qes/Qts.

Of course you can use more powerful motors to squeeze more than three octaves out, but compression ratios get extreme unless multiple drivers are used, but the LF suffers, so in the end it's always about trading efficiency for BW.

Not familiar with the Klipsch horns beyond what was recently posted, so nothing about yours, but once above the driver's mass corner, first it rolls off due to decreasing air loading, then inductively rolls off just like Keele shows, so while it will have some extension it will need EQ and what normally is done is to use CD horn EQ to flatten the horn's response down to the driver's, i.e. trading efficiency for BW. Not many 'free lunches' in acoustics.

GM

 

[GM]

A Question - - GM, when using hornresp and looking at the directivity of these little midbass, its typical to see a predicted on-axis rise of 7dB or more vs "flat" response. In practice - does that happen?

Here's how hornresp shows a horn scaled roughly from John Inlow's drawing of his 135Hz horn. The back chamber is pretty tight

DB would have to answer that since I've never measured it nor felt the need to pay much attention to it since I relied on the known excellent HF hearing of others, though IIRC I've got some some accurate Altec polars I can check.

I do know that the ones done for deep cone [Altec] and shallow cone [JBL] woofers showed that Altec's pretty much followed the piston chart whereas the JBL's were 'all over the map', though apparently due to more flex, so would think that a horn would be similar to the piston if just basically a horn, i.e. not multi-cell, Smith, etc..

Well, if the compression chamber is tuned too high, then it will have a rising response like simmed, so tune it to the horn's BW mean for best overall performance: [Fl*Fh]^0.5

GM

 

[freddi]

hey GM - what might I be doing wrong with regards to wanting to "down-scale" a La Scala model in hornresp via the resize wizard ? - its telling me I can't go lower than "1.01" and I've done 0/7, whatever in the past with no problem.

 

[sumotan]

Thank you again GM for the tutorial. Well Im not greedy for lows perhaps 60-70 hz. Lol What I would want to attain is to be able to crossover at around 600-700hz to make a 2 way. I was looking into the Klipsch horn site & aparently someone had measured the La Scala bass bin to go up too 700hz or so with a dip at 500hz. Now if we calculate base on 2xFs/Qes, those woofers too will not make it pass 400 hz. Can I speculate that the slotted mouth woofer opening plays a part too to allow a higher xo frequency ?

Cheers

 

[GM]

No clue, never played with it, but just now took a huge 515-8G 30 Hz expo and it did a 0.7, then 0.5, then did a 0.5 to the 0.7, so dunno. Nifty feature/tool though!

Post your La Scala record, so I can try, 'eyeball' it if I can't.

GM

 

[sumotan]

Far GM & thank you.

 

[freddi]

hi GM- maybe hornresp got damaged when my pc hung up due to low RAM ? I ran the newest setup but that did not fix things - look at he error message

 

[GM]

Thank you again GM for the tutorial.

You're welcome!

Well, the slot area frequency*~0.81 sets the horn's upper cutoff if that's what you're asking.

Anyway, 'sounds' like they used a vintage style horn driver, which makes sense since it's a vintage design and what what guitar driver design are based on, i.e. has a wide BW breakup modes BW to fill in above the horn's roll-off same as the old Altec, JBL small theater/PA horns and since it rolls off around 400 Hz, the dip at ~500 Hz is about right, so a quick trip to Eminence turned up this, which is probably about the best you can do nowadays unless JBL or other cinema sound folks has something better: Speaker Detail | Eminence Speaker

GM