Hello all,
I am considering a FAST-like speaker with :
I am afraid that would be misusing the woofer, because when simulating it (WinISD) in a sealed 38 litres I hit xmax with only 15W (out of 100W admissible) with 100dB SPL. Further more, the SAM-300D includes a 3dB bass boost at 40Hz, which adds a little excursion, reducing admissible power.
Is that a design flaw ?
Is the 100dB SPL too low ? I suppose that is RMS value, so what margin does it leave in terms of crest factor headroom, could I actually play music at 100dBrms SPL ?
I don't particularly play music loud, I just want to avoid an undersized system (FWIW the room is about 5m x 5m 3m ceiling, open into a 2nd room the same size, open into a third).
Thanks for your advice and input.
I am considering a FAST-like speaker with :
- Full range Fostex FE126En
- Woofer Monacor SPH-220HQ in 30 litres sealed enclosure
- Monacor SAM-300D plate amp for the woofer
I am afraid that would be misusing the woofer, because when simulating it (WinISD) in a sealed 38 litres I hit xmax with only 15W (out of 100W admissible) with 100dB SPL. Further more, the SAM-300D includes a 3dB bass boost at 40Hz, which adds a little excursion, reducing admissible power.
Is that a design flaw ?
Is the 100dB SPL too low ? I suppose that is RMS value, so what margin does it leave in terms of crest factor headroom, could I actually play music at 100dBrms SPL ?
I don't particularly play music loud, I just want to avoid an undersized system (FWIW the room is about 5m x 5m 3m ceiling, open into a 2nd room the same size, open into a third).
Thanks for your advice and input.
Greets!
No design flaw, just not designed for high power down low.
Well, you can pump 100 W into it down to ~100 Hz = ~110 dB/2pi, but due to only having a 5.5 mm Xmax it's only ~95 dB/40 Hz/4 W/2pi according to Hornresp plus whatever room/boundary gain boosts it, so WinISD is off a bit unless it's a corner loading sim.
Factor in the bass boost and it can only handle ~2 W/40 Hz, though the drivers can be over driven a bit, but we don't know how much since its Xmech spec isn't published.
Add +3 dB for stereo.
No, this is peak transient power, so 'music' power is anywhere from a few dB to -20 dB depending on the recording, so figure ~78 dB/m/stereo avg. worst case since with such a large room open to others there won't be much room gain. Factor in up to -6 dB/doubling of distance beyond 1 m and it might not be loud enough for some music, though if in an apartment or similar attached housing even this will likely be too loud unless your neighbors like your music.
For music [I prefer going 'live']/HT [THX Reference], so it's very undersized for my ~4.877 m x 7.315 m x 2.438 m open format room, but for TALK radio, FM, basic TV shows it's loud enough with ~ daily used since new 1978 Radio Shack Minimus 7 'bookshelf' speakers: Minimus 7
GM
edit: FWIW, found my ancient Radio Shack SPL meter with a so-so calibration many decades ago, so only trust it in the ~100-5 kHz AM radio band, but listening to an older woman with a fairly deep voice on the news it was bobbing around from as little as 60 dB to 74 dB peaks and a vintage R&R music Infomercial at ~10 dB higher in front of my face.
No design flaw, just not designed for high power down low.
Well, you can pump 100 W into it down to ~100 Hz = ~110 dB/2pi, but due to only having a 5.5 mm Xmax it's only ~95 dB/40 Hz/4 W/2pi according to Hornresp plus whatever room/boundary gain boosts it, so WinISD is off a bit unless it's a corner loading sim.
Factor in the bass boost and it can only handle ~2 W/40 Hz, though the drivers can be over driven a bit, but we don't know how much since its Xmech spec isn't published.
Add +3 dB for stereo.
No, this is peak transient power, so 'music' power is anywhere from a few dB to -20 dB depending on the recording, so figure ~78 dB/m/stereo avg. worst case since with such a large room open to others there won't be much room gain. Factor in up to -6 dB/doubling of distance beyond 1 m and it might not be loud enough for some music, though if in an apartment or similar attached housing even this will likely be too loud unless your neighbors like your music.
For music [I prefer going 'live']/HT [THX Reference], so it's very undersized for my ~4.877 m x 7.315 m x 2.438 m open format room, but for TALK radio, FM, basic TV shows it's loud enough with ~ daily used since new 1978 Radio Shack Minimus 7 'bookshelf' speakers: Minimus 7
GM
edit: FWIW, found my ancient Radio Shack SPL meter with a so-so calibration many decades ago, so only trust it in the ~100-5 kHz AM radio band, but listening to an older woman with a fairly deep voice on the news it was bobbing around from as little as 60 dB to 74 dB peaks and a vintage R&R music Infomercial at ~10 dB higher in front of my face.
Hello GM,
Thank you a lot for taking the time to answer !
So lesson learned : woofer is not subwoofer.
Now I wonder what the correct integration of the SPH-220HQ would be, it's got to have a purpose !
Am I supposed to add a high-pass to allow for more power ? (without the bass boost of course).
Would it work well as a woofer with a full range (FF85wk) and passive XO ? Or would it still be too low power ?
Thank you again
Thank you a lot for taking the time to answer !
So lesson learned : woofer is not subwoofer.
Now I wonder what the correct integration of the SPH-220HQ would be, it's got to have a purpose !
Am I supposed to add a high-pass to allow for more power ? (without the bass boost of course).
Would it work well as a woofer with a full range (FF85wk) and passive XO ? Or would it still be too low power ?
Thank you again
It's a good 8in paper cone midbass: as GM says, it just doesn't happen to be designed for THX (let alone Dolby) spec. HT, or more broadly speaking high output / high LF dynamic range in large spaces. Like 99.99% of 8in & smaller midbass drivers, it's intended when used by itself for more modest output levels and / or more modest spaces. Running multiples will increase the output potential, but does put the box size up.
Since you "don't particularly play music loud" I would say that it will be fine. I'm using the Monacor SPH8M with Pluvia 7 in a FAST in a 7.4m x 5m room with tall ceiling and open at the side to a 4.5m x 2.5m room. Mine is 46 litre bass reflex so I have a bit more efficiency at the bottom end. Can you switch off the bass boost feature?
Thanks Scott and Stal for your valuable input.
The SPH-220HQ is rated for 90dB/100W/180W, so I expected it to have decent output as I'm not into HT/THX, I just seek "HiFi" with decent bass.
Indeed specs seem much alike the SPH8M, and yes I have just the 8" unit.
The FE126En are 93dB, so I can't match the 220HQ with passive XO. However with FF85wk or PS-95 (I happen to have a pair of those waiting on a shelf) I expect it could go well as they are ~86dB/15~20Wmax.
So I'm thinking about going passive XO 2nd order around 300Hz into the FF85wk or PS95. The unfiltered woofer would hit Xmax at 101dB/20W.
For more headroom, I could high pass the woofer at 30Hz (?), then it can take 40W at Xmax (104dB)
Does that seem correct design ? It would give 60Hz f3, 40Hz f10, I could add a sub unit if I feel the need for more bass (already have a plate amp...).
Thanks !
The SPH-220HQ is rated for 90dB/100W/180W, so I expected it to have decent output as I'm not into HT/THX, I just seek "HiFi" with decent bass.
Indeed specs seem much alike the SPH8M, and yes I have just the 8" unit.
The FE126En are 93dB, so I can't match the 220HQ with passive XO. However with FF85wk or PS-95 (I happen to have a pair of those waiting on a shelf) I expect it could go well as they are ~86dB/15~20Wmax.
So I'm thinking about going passive XO 2nd order around 300Hz into the FF85wk or PS95. The unfiltered woofer would hit Xmax at 101dB/20W.
For more headroom, I could high pass the woofer at 30Hz (?), then it can take 40W at Xmax (104dB)
Does that seem correct design ? It would give 60Hz f3, 40Hz f10, I could add a sub unit if I feel the need for more bass (already have a plate amp...).
Thanks !
Last edited:
The boost cannot be switched off.
I looked at the SPH-8M, I don't how I missed it, it seems hardly less efficient than the 220HQ, but works in much smaller enclosures (22l vs 38l sealed, 46l vs 72l BR).
Edit : Stal, I suppose you put a high pass on the BR to protect the driver, how difficult/expensive is that ? (I always hear low freq filters are expensive/hard to source)
I looked at the SPH-8M, I don't how I missed it, it seems hardly less efficient than the 220HQ, but works in much smaller enclosures (22l vs 38l sealed, 46l vs 72l BR).
Edit : Stal, I suppose you put a high pass on the BR to protect the driver, how difficult/expensive is that ? (I always hear low freq filters are expensive/hard to source)
Last edited:
I'm using a 1st order series crossover, stereo pair of course.
The SPH-8M does have the advantage of relatively compact box sizes. In fact you can go down to 10 litres sealed with a Q of < 1.
The advantage of the 220HQ is a nice flat freq response in the mid range which makes it nice for a 1st order xover.
Its OK to use a passive xover with the FE126En as you can attenuate it with resistors (an L pad circuit for example).
You would need an extra woofer though for passive stereo xovers.
If you went down the WAW route i.e. stereo FAST i.e. 2 woofers then the FF85wk would make an ideal mid/tweeter.
If you wanted to use the FE126Ens then you could run them full range and run the woofers in a 1.5 way configuration. Basically have the woofer wired in parallel with the Fostex and an inductor in series with the woofer. This would give you baffle step compensation.
The SPH-8M does have the advantage of relatively compact box sizes. In fact you can go down to 10 litres sealed with a Q of < 1.
The advantage of the 220HQ is a nice flat freq response in the mid range which makes it nice for a 1st order xover.
Its OK to use a passive xover with the FE126En as you can attenuate it with resistors (an L pad circuit for example).
You would need an extra woofer though for passive stereo xovers.
If you went down the WAW route i.e. stereo FAST i.e. 2 woofers then the FF85wk would make an ideal mid/tweeter.
If you wanted to use the FE126Ens then you could run them full range and run the woofers in a 1.5 way configuration. Basically have the woofer wired in parallel with the Fostex and an inductor in series with the woofer. This would give you baffle step compensation.
Attachments
Thanks Stal.
Forgive my ignorance, I do not understand the advantage of the 220HQ in terms of flat response (up to 2kHz according to documentation), because I believe that the woofer should be XO below the voice range.
Could you bring some light ?
Where I would like to go is a stereo two way with full range and woofer, crossed around 200-400Hz. I know nothing about designing a XO, so the simpler the better. I will try to model your suggestion with VituixCAD.
Anyway I already built a 30l sealed box and put the woofer and plate amp in it, I will post measurements.
Forgive my ignorance, I do not understand the advantage of the 220HQ in terms of flat response (up to 2kHz according to documentation), because I believe that the woofer should be XO below the voice range.
Could you bring some light ?
Where I would like to go is a stereo two way with full range and woofer, crossed around 200-400Hz. I know nothing about designing a XO, so the simpler the better. I will try to model your suggestion with VituixCAD.
Anyway I already built a 30l sealed box and put the woofer and plate amp in it, I will post measurements.
Useful if you want a 1st order (6dB per octave) filter. With your plate amp I read that it has an 18dB (3rd order) filter which is quite steep so you will be nowhere near the midrange which is a good thing. However if you were to use a 6db passive filter you may run into difficulties with some drive units that may have a peaky midrange. Your drive unit is very flat so is a good choice for a shallow filter (1st order 6db).
There are some advantages with a 1st order filter the main one being good transient response. Although it is debated if this is that audible. Another advantage is a simple passive crossover with fewer components and more forgiving of component choice tolerances.
My SPH-8M has some peakiness at 2.5khz and 3.5khz if you look at the graph. My crossover point is at about 270Hz so over 3 octaves before it reaches about 2.2kHz, so it should be enough attenuation by then.
There are some advantages with a 1st order filter the main one being good transient response. Although it is debated if this is that audible. Another advantage is a simple passive crossover with fewer components and more forgiving of component choice tolerances.
My SPH-8M has some peakiness at 2.5khz and 3.5khz if you look at the graph. My crossover point is at about 270Hz so over 3 octaves before it reaches about 2.2kHz, so it should be enough attenuation by then.
Attachments
This would be classed as a 1.5 way. It may be more appropriate with the larger of your Fostex Drivers. On the little FF85WK you would be better with a full 1st order Xover i.e a cap on the FF85WK as well as the inductor on the woofer.
The FF85WK has a fairly high resonance about 120Hz and has a small Xmax so you would be pushing it hard running it full range.
The FF85WK has a fairly high resonance about 120Hz and has a small Xmax so you would be pushing it hard running it full range.
If I add only a cap on the FF85, I get a weird resonance that I don't understand (pic1). I tried to reduce it with a resistor (pic2).
Any way I thought :
Filters now look ugly, response and impedance seem OK, though I'm sure I'm missing a lot...
Would that be acceptable ? Or what would be a proper (simple) crossover ?
Also I traced the response of the woofer box, so I just post it (pic4). Looks like a rollercoaster...
Any way I thought :
- too much HF contribution from the woofer (due to the filter "shelving" ?)
- the slope should be steeper on the ff85 so as to avoid excursion.power limitation problems
Filters now look ugly, response and impedance seem OK, though I'm sure I'm missing a lot...
Would that be acceptable ? Or what would be a proper (simple) crossover ?
Also I traced the response of the woofer box, so I just post it (pic4). Looks like a rollercoaster...
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.