Tiny PA for living room bookshelf + DSP

[HalasKYO]

Dear all,

This will be my "second" build (The first was during Uni a 25l ported box with 2pcs B&C 8NDL51 and a ME20 horn MTM conf. with a DE500 , lot of help from my consultant.
That was build measured (Clio FW, simulated with LSP cad 5.25), braced, stuffed, and documented. I could keep the box and the drivers.
Now ~10 years later I thought to build a stereo bookself speakers from it.
I found 2 Selenium D220Ti online (OMF) so I will not use the DE500 (maybe laster a Center channel ) .
My plan is to build plywood box, round off the edges ~10mm front ported tuned to ~65Hz and use ME20 horns.
I added the 8NDL51 to the WinISD database (data from website) but WinISD shows some "Driver data dails integrity check".WTF??! What did I do wrong ?
Anyway I started to play with the box and port size. The driver has a 94dB sensitivity and my plan is to keep it below 100dB as we live in a small apartment with neighbours.(relevant for port size and length)

My box size: 12l (65Hz tune) ~24cm width (1,8cm ply) internal width will be ~20cm and plan to make the port from the same material.
To keep is short, I used 20W as signal and got ~14,8m/s peak with 103-104dB, port is 20cm x 1,5cm square 13,18cm long. That shold be plenty.

I will use 2x BRU5 for amp (DSP) and cross 1,5kHz 12dB and correct as much us possible, and later I will build a passive crossover (maybe will do a 2nd order to protect the tweeter) plan see at the pics.
Should I be concerned by the phase ? I want to use front port as the speakers will be close to a wall.
I also tryed to model the box on android tablet with Speaker Box Lite (which has a HUUUGE database but quiete a complex GUI)

If I plan to DSP it pull up some of the 40-50Hz region, should I tune it lower as the drop in frequenz will be not that much ?
With 50Hz tune -7dB will be 50Hz which I can EQ out as power handling is 200W and I am nowhere near Xmax.

Win ISD only showd data at the "rear port-air velocity" But as I plan to use front, how can I set it up ?

I added pic from the planned crossover. As I hear quiete a hiss from the 2 selenium (without horn as not yet arrived) the 2x100Ohm should pull that also down (to the 94dB to the 8NDL)
The second order crossing cause a phase change so I reversed the tweeter.

What would you recommend for a linear and a slight V shaped use for living room ? Listening distance ~3m. 25sqm.

Thank you very much!

I also added some pics from the old build

 

[HalasKYO]

Forgot to mention that I will buy a Behringer UMC404 and Behringer measuring mic and a T-bone MM-1 (calibrated) to compare. Later I plan also to build at ARTA box to measure speakers.

 

[Fledermaus]

To my modest knowledge, "rear port" in WinISD refers to port location wrt driver diaphragm, not wrt enclosure (which is mostly indifferent in terms of tuning).

 

[HalasKYO]

To my modest knowledge, "rear port" in WinISD refers to port location wrt driver diaphragm, not wrt enclosure (which is mostly indifferent in terms of tuning).

Thank you I will read up on that thema, but first I will give a go to the Vituxcad , as I have seen that there your also simulate the 2 driver interference to each other. Which could be very interesting.

 

[Fledermaus]

Besides, boosting 50Hz in a ported speaker tuned to 65Hz doesn't seem to be the idea of the century : below tuning freq, the driver operates in "acoustic short circuit" territory, so all driver-port mutual cancelling and no excursion control... you should rather filter out frequencies below 65 IMO, and add a sub if you want serious bass.
Edit : such low-freq boost is best envisioned in the case of a closed box, maybe you could simulate one. VituixCAD enclosure tool might do this fine.

 

[ppataki]

Besides, boosting 50Hz in a ported speaker tuned to 65Hz doesn't seem to be the idea of the century : below tuning freq, the driver operates in "acoustic short circuit" territory, so all driver-port mutual cancelling and no excursion control... you should rather filter out frequencies below 65 IMO, and add a sub if you want serious bass.
Edit : such low-freq boost is best envisioned in the case of a closed box, maybe you could simulate one. VituixCAD enclosure tool might do this fine.

+1 on this

 

[HalasKYO]

Besides, boosting 50Hz in a ported speaker tuned to 65Hz doesn't seem to be the idea of the century : below tuning freq, the driver operates in "acoustic short circuit" territory, so all driver-port mutual cancelling and no excursion control... you should rather filter out frequencies below 65 IMO, and add a sub if you want serious bass.
Edit : such low-freq boost is best envisioned in the case of a closed box, maybe you could simulate one. VituixCAD enclosure tool might do this fine.

Thank you, was also thinking that, but first I will test them without, cutted at 65Hz . Vituix cad I tried, it gave me ~8,5 l box (still ported). But I shall see what it gives in a closed, but I fear the drop would be much more significant, as this driver fall from 120Hz.. even it is falling with 6dB due to box, it will be nowhere near a ported design. If I would not have the drivers already . I could go for a 8BG51 as that can be tuned much deeper with only 2dB lost in sensitivity (92dB compared to 94dB)

 

[Fledermaus]

You still can give it a try in simulation, taking max power curve into account... a closed box might give you some low-freq DSP boost headroom, and you can linearize further with a bit of midrange attenuation - no one escapes Hofmann's iron law !

 

[HalasKYO]

You still can give it a try in simulation, taking max power curve into account... a closed box might give you some low-freq DSP boost headroom, and you can linearize further with a bit of midrange attenuation - no one escapes Hofmann's iron law !

I will, but not with max power (that would be waaay to much). I plan to use them on max 100dB, or lower. If I caclulate that 92dB ~ below 1,5kHz from the 8NDL, quater space room (+6dB) and If I calculate with stereo speakers (+3dB again) that is like ~1W... I thought that I can EQ out until I reach XMAX or Power limit. But if the enclosure cut the freq with ~12dB/oct and the driver is also falling ~12dB that should add up in theory, so even if I boost 12dB on 30-40Hz it would be audiable but not linear (still -12dB). If i am not mistaken in Klinger "bible" I read that a ported box is cutting 12dB, a closed one with 6dB (there the problem only that it is falling from much higher).

 

[smygolf]

JBL 4645C subs are made to have a B6 alignment spot on the tuning freq and a steep highpass right after.
Not the best thing to do regarding Group Delay but it will add 3-6dB output.

Could be a thing to consider when designing the speaker

 

[HalasKYO]

JBL 4645C subs are made to have a B6 alignment spot on the tuning freq and a steep highpass right after.
Not the best thing to do regarding Group Delay but it will add 3-6dB output.

Could be a thing to consider when designing the speaker

Wow , that is some beefy sub. EQ 22Hz with 20Hz 12dB cut probably power limited. but that is only 3Hz below tune freq. (tuned to 25Hz, but based on graph I would say, port is tuned to 35Hz and with EQ usable till 22-25... either way, that is waay to big and very low WAF factor. )
Earlier I had a 12" sub which was big 60x60x50cm. If I will ad one to this setup it must be smaller (with lower sensitivity probably)

 

[smygolf]

Wow , that is some beefy sub. EQ 22Hz with 20Hz 12dB cut probably power limited. but that is only 3Hz below tune freq. (tuned to 25Hz, but based on graph I would say, port is tuned to 35Hz and with EQ usable till 22-25... either way, that is waay to big and very low WAF factor. )
Earlier I had a 12" sub which was big 60x60x50cm. If I will ad one to this setup it must be smaller (with lower sensitivity probably)

Port is tuned at 27hz according to data-bass.
My own test says the same (have 3 of them)

It uses the fact that the cone has near zero movement at the tuning.
I do not use it myself but it is a "feature" that can be used on all bass reflex speakers.

 

[HalasKYO]

Small update, I bought 2 Monacor 100W variable L-pads to get the Compression drivers to not hiss anymore. I calculated ~17dB sensitivity difference between the 8NDL51 and the D220Ti . (B&C gives 94dB on datasheet, but that is including the bump above 1kHz, which I will not use --> 92-93dB will be in reality under 1,5kHz.) Today I will try the CD -s with the L-pad, with DSP , and try different crossings 1,2-1,5-2kHz as I will only use fraction of the power handling. I know ME20 can only load utill 1,5kHz.) I will try to make some measurement and design the box today. Goes is to have a reasonable deep end reflex for small power ~30-50W max, and not too deep port. Hopefully I can finish the boxes during the christmas time. (the 2 woofer is not at my place I will only get to test them in december.) but until , I can still learn and try to measure what I can. In the finished design I plan to use MOX resistors and not the L-pad as I plan to use it on other projects.

 

[Heinrich]

won‘t work too well, sorry, but how to tell more polite?

1. box tuning is off, needs reflex at 40Hz or lower to cope at least w/ standard pop music
2. needs equalizer in-room to flatten frequency response in bass
3. needs port at least 80mm in diameter to prevent noise of rushing air aka chuffing, port needs rounded edges
4. passive crossover is way too simple, I assume, check with measurements
5. don‘t do d‘Appolito, 2 and a half way is the only reasonable option, acknowledge vertical directivity

Hope I didn‘t spoil your fun w/ the project, but better me than the result once finalized.

 

[HalasKYO]

won‘t work too well, sorry, but how to tell more polite?

1. box tuning is off, needs reflex at 40Hz or lower to cope at least w/ standard pop music
2. needs equalizer in-room to flatten frequency response in bass
3. needs port at least 80mm in diameter to prevent noise of rushing air aka chuffing, port needs rounded edges
4. passive crossover is way too simple, I assume, check with measurements
5. don‘t do d‘Appolito, 2 and a half way is the only reasonable option, acknowledge vertical directivity

Hope I didn‘t spoil your fun w/ the project, but better me than the result once finalized.

You did't spoil, thank you for your input. This is to use the 2 pcs 8NDL that I have on hand. And I've found 2 Selenium D220Ti for ~100€... so that is given. If I would buy it now, I would probably go with a B&C 8BG51 that would go down utill ~49Hz or use a complettly different build like an econowave. (1" CD + 12" woofer reflex or passive membrane, there would be much more wigle room with woofer.)
I already got the 2pcs 8NDL51 ( currently in dApollo from my batchelor but only 2 pieces of woofer) and I wanted to use that to build L+R 1pcs 8" woofer 1" Compression driver .
1 . Box tuning as the woofers are given I can try to make it go deeper but I plan with a sub later on --> 65Hz is the 8NDL capable.
2. I will use DSP, currently 2 BRU5 Class D with DSP (1 for the woofers 1 for the tweeters) CD with L-pad, in the crossover design it is not included YET.
3. My plan was to use ~1,5cm x 20cm port --> 30cm2 ; your recommended 8cm is ~ 50cm2, but you see the port speed , this I wil reevaluate with powerr handling. (in room will not be used nowhere near power handling, so I don't fear that to be a problem. I want to be under ~14m/s in the max power planned scenario.
4. passive crossover is very simple, I will first du measurement when the box is built, measure near field, mid field crossed both at 1,5kHz, and start from there. Then far field and DSP to flatten (L-pad will be implemented in the crossover as I want to use the L-pad for future projects.
5. as I wrote above, it will not be a d' apollo sorry for the confusion it will be 1 tweeter 1 woofer / box --> more like a bigger bookself like Klipsch RB-81 ish design...
I don't really get why the 2,5 way would be better (same woofer diferent crossing) more than a proper 3way ?

 

[Heinrich]

You did't spoil, thank you for your input. This is to use the 2 pcs 8NDL that I have on hand. And I've found 2 Selenium D220Ti for ~100€... so that is given. If I would buy it now, I would probably go with a B&C 8BG51 that would go down utill ~49Hz or use a complettly different build like an econowave. (1" CD + 12" woofer reflex or passive membrane, there would be much more wigle room with woofer.)
I already got the 2pcs 8NDL51 ( currently in dApollo from my batchelor but only 2 pieces of woofer) and I wanted to use that to build L+R 1pcs 8" woofer 1" Compression driver .
1 . Box tuning as the woofers are given I can try to make it go deeper but I plan with a sub later on --> 65Hz is the 8NDL capable.
2. I will use DSP, currently 2 BRU5 Class D with DSP (1 for the woofers 1 for the tweeters) CD with L-pad, in the crossover design it is not included YET.
3. My plan was to use ~1,5cm x 20cm port --> 30cm2 ; your recommended 8cm is ~ 50cm2, but you see the port speed , this I wil reevaluate with powerr handling. (in room will not be used nowhere near power handling, so I don't fear that to be a problem. I want to be under ~14m/s in the max power planned scenario.
4. passive crossover is very simple, I will first du measurement when the box is built, measure near field, mid field crossed both at 1,5kHz, and start from there. Then far field and DSP to flatten (L-pad will be implemented in the crossover as I want to use the L-pad for future projects.
5. as I wrote above, it will not be a d' apollo sorry for the confusion it will be 1 tweeter 1 woofer / box --> more like a bigger bookself like Klipsch RB-81 ish design...
I don't really get why the 2,5 way would be better (same woofer diferent crossing) more than a proper 3way ?

The data will show if the NDLs were good midranges. Chose your woofer

 

[HalasKYO]

The data will show if the NDLs were good midranges. Chose your woofer

I will post measurements for sure, and experiences, As I remember they are quiete good, until 1,5kHz, even above that if you deal with the bump between 1,5-4,5k and boost a bit on 1,5kHz ~1-2dB. It will not be bass heavy for sure but very fast and clean as I remember. The sound did separated from the speakers. I will try what is the best crossing 1,5 - 3 kHz . And next year I plan to build a sub GRS 12SW-HE reflex if I can plan out a way to the wife to accep it, or maybe I will need to setle for something smaller.