Supravox 400-2000 - what to do with them?

In a moment of madness i bought a S/H pair of Supravox 400-2000's -- now i have got to decide how best to use them.

I purchased them because they have a low Rms which is meant to be an indicator of LF detail at low listening levels - which is a trait i am after.

I have had a mono set up with the driver in a sealed 160 ltr test cabinet, which with minimal LF equalisation is pretty flat from 50 hz up to 1200hz, where it has a wobble. ( I am only going up to 500hz max)

T/S measurements attached - manufacturers and mine, looks as if things loosen up abit with use.

Wisdom would say not to use this low qts driver in a sealed cab, however with the DSP i can get a pretty reasonable response out of the sealed arrangement.

I was going to experiment with a couple of different cabinet styles before deciding on what to build a pair of.
I suppose i should try a vented cabinet and or a MLTL, but am not sure if the LF boost is worth the sacrifice of smooth phase and group delay.

Any experience of these drivers, in smallish cabinets (200 ltrs max)? and recommendations for the cabinet arrangements?
(I know an Jensen/Onken arrangement is recommended by the manufacturer - my previous experience of Onkens is the bass is not dry enough for me - so its not in the running)
 

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hottattoo

Member
2006-09-16 10:55 pm
Supravox makes excellent drivers and these are similar to the Altec 515b's in that they have an excellent mid range / mid bass. I would put these drivers in a big sealed enclosure that is rigid and well braced ( 150 - 200 liters ) in your case. Do not make the mistake of EQing the bottom end too much as these are not sub woofers. I would use them from 45 -50hz. with sub woofers below ( if in your plans ) and up to 500hz as you mentioned. The rest depends upon your mid range driver selection. A nice horn mid range would be a good match after pad it down several db or bi amp.
 
The Qts is way too low for a sealed enclosure, the f3 is at 87Hz in 200l and they don't have a high excursion.

They work fine in a BR enclosure, 150l, tuned to 41Hz, f3 53Hz, at 40Hz -7dB or 200l, tuned to ~44Hz, f3 at 47Hz. A backloaded horn would work too (probably even better) but will most likely much larger than 200l.

The Supravox can more than the suggested 500Hz, to be honest, that can be done by cheap PA chassis and they give a lot more deep bass and max spl. A 2 way system with a medium sized horn with a xo of ~1,2-1,5kHz will work nicely and uses the advantages of the supravox.
 

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As anticipated - polar opposed recommendations.
Couple of points i thought these drivers were more like the Altec 416's, with a VAS that are 150 ltrs less , so a slightly smaller cab.
I dont consider 10mm as limited xmax, in our smaller european rooms that still will be very loud.
I was wondering whether a BR tunned really low would be the way to go - using the port to reduce the impedance peak, more than boost the LF.
Maybe a TL would be the best approach to minimise the impedance peak? I dont want an over stuffed cabinet to kill the peak, as that over stuffing also kills all the microdynamics, which a PA driver wont give me.
I know i am wasting the midrange of the driver, but the wobble in response means it wont reach the TPL's @ 1400Hz without compromise. So i will have to make it a 3 way slotting my midrange horn in to fill the couple of octaves.
 
Couple of points i thought these drivers were more like the Altec 416's, with a VAS that are 150 ltrs less , so a slightly smaller cab.

Well, you've got the TSP, simulate it yourself. If you go smaller, it costs you a lot of the deep end.

I dont consider 10mm as limited xmax, in our smaller european rooms that still will be very loud.

The 10mm are peak to peak and generousely calculated, if you check the winding height you will quickly notice of the +/-5mm are only +/-3mm left over - at least if you calculate it yourself honestly.

-> (winding depth - magnetic gap depth) / 2

You still get quite high spl but keep in mind that chassis needs to be protected by a lowcut/subsonic filter, otherwise damage to the coil can happen quite easily even without monster loudness.

I was wondering whether a BR tunned really low would be the way to go - using the port to reduce the impedance peak, more than boost the LF.
Maybe a TL would be the best approach to minimise the impedance peak? I dont want an over stuffed cabinet to kill the peak, as that over stuffing also kills all the microdynamics, which a PA driver wont give me.

With a such low Qts a TL is out of the question. Furthermore, it will give you more impedance peaks, not less - unless you are dampening it to death (in which case you can build a closed box anyway).

If you tune the BR to the same frequency as the fb (resonance of the chassis in the box), you'll get an extremely boomy, washed out sound, especally if you go for a smaller enclosure. That looks like this:

attachment.php


Not really something you'd want to listen to, I suppose. So using a BR system to minimize the impedance fluctuation isn't an option. Besides that, any Helmholtz resonator or other ventilation system introduces a 2nd (or more) impedance peak(s).
But please let me ask, why do you want to minimise the impedance peak? It doesn't 'harm' you in any way, even a tube amplifier can cope with that peak.

I know i am wasting the midrange of the driver, but the wobble in response means it wont reach the TPL's @ 1400Hz without compromise. So i will have to make it a 3 way slotting my midrange horn in to fill the couple of octaves.

What do you mean with TPL? Sry, not a native speaker. :worried: The measurement shows it to fluctuate around ~ +/-2,5dB in that area. That's not bad at all. A midrange horn won't be much better there. But ofcourse, going up to 500Hz is okay, I just wanted to mention the driver can do more.
 

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TPL. = beyma TPL 150

When said tuning a BR low I was thinking about around driver Fs and then adding a subsonic filter around 30 hz.

Regarding impedance peaks I have always thought it was good practice to have the lowest peak possible, keeps the phase change smoother also.
 
TPL. = beyma TPL 150

Ah, thank you!

When said tuning a BR low I was thinking about around driver Fs and then adding a subsonic filter around 30 hz.

The driver resonance rises with the enclosure. The case I simulated above the fb is in 100l infact actually 66Hz, even if the free air fs is below 30Hz.

Regarding impedance peaks I have always thought it was good practice to have the lowest peak possible, keeps the phase change smoother also.

That's not true. Around the fs (or more, fb -> in the box) there's always the same turn of phase, you can see it in almost all measurements of speakers. It gets more complicated than that, the electrical phase isn't the same as the acoustical phase.

To flatten the impedance makes it easier to create a crossover but the xo-frequency is high enough to have only little influence on the xo, so it's not relevant. You can level the impedance peak with an absorption circuit but that's mostly a hypothetical question because the huge coil and capacitors will cost you around the same as the drivers itself and you don't have a real advantage, a lot of power will be burnt in the xo and the efficiency will drop.

You will benefit of a impedance correction in case you use a tube amplifier. For tube amps it's still almost always the best option only to correct the mid+high impedance peaks/fluctuation.
 
The Qts is way too low for a sealed enclosure, the f3 is at 87Hz in 200l and they don't have a high excursion.
How do you arrive at this? I put the parameters in AJ Horn and have a response down to around 50Hz (-3dB). When you factor in a bit of resistance it goes even lower in 180L. Also around 110dB should be plenty loud in an average room.
 
In my test cabinet the impedance peak is around 44 hz, and 27hz in free air.

I have been wondering about a "leaky" cabinet to mimic a very large box. The super cardioid horn loaded arrangement I currently have works well in the room. I don't think a single 15" per channel will be enough for this OB arrangement though, currently using a pair of deltamax's per channel with a lot of EQ.
 
How do you arrive at this? I put the parameters in AJ Horn and have a response down to around 50Hz (-3dB). When you factor in a bit of resistance it goes even lower in 180L. Also around 110dB should be plenty loud in an average room.

I probably used different TSP than you did, I took them from the 2nd picture. I don't know what enviroment (halfspace? quarterspace?) you've simulated either. This is the simulation (though without serial resistance):

Supravox_CB.jpg

I don't know how you are comming to 110dB spl, according to WinISD the maximum linear excursion (3mm) is reached at 50Hz at 96dB. That's loud but nowhere near something you'd expect from a 15" driver.
 
Here are some measurements for the driver in my 160 ltr test cabinet.
No EQ - just being fed from a 20watt T amp.
First trace is the impedance installed in the cabinet, resonance ~ 47hz. Cabinet is lightly stuffed, with heavy stuffing i can halve that peak, but a heavily stuffed cabinet takes all the life out of the driver.
Second trace is a frequency sweep - 10cm off the driver cone, 30cm and 60 cm. As you can see i have a " floor interaction" occuring around 200Hz which get worse, as expected as you move the mic back. Interestingly the HF smooths up as i go further back, maybe i could do a 2 way (doubt at 1600 hz - 15" beaming will be tolerable)
 

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hottattoo

Member
2006-09-16 10:55 pm
vinylnvalves,

Are you aiming strictly for a 2 way system ? What is your ultimate goal for low frequency ? If going 2 way, you will stretching both the supravox and tpl drivers. The tpl 150 sounds best when crossed above 1600hz. The supravox would sound better crossed up to around 800hz even though it is capable of going much higher. IMHO you would be much better off going to a 3 way system using a ( precision devices,beyma, etc) 10" driver in a fairly small sealed box to cover the approx 500hz to 1800hz or so. You will have plenty of room to experiment crossover wise if you go 3 way. If there is a chance of using these speakers for home theater use, then a subwoofer will be mandatory or you will destroy the supravox driver.
 
No to the 2 way, always have a 3 way as the plan. Midrange horn covering those octaves ( 400hz to 1600hz). Your statement about destroying the drivers worries me. I had assumed as Supravox have a kit for a band pass sub using this driver I would be okay taking it down into the lower octaves (30-40hz)

I know I have posted a trace of the driver in a sealed cabinet, don't assume that this is the final solution. This is where I want to kick some different ideas around in the proverbal sandbox. MLTL, BR etc. Utilising the DSP to boost the LF, if necessary.
 
The Supravox isn't anything you'd become happy with in a home cinema with that kind of volume. It's a bass, not a subwoofer. It simply doesn't go deep enough in BR, CB or BP. The cause is the very low Qts and ofcourse the low maximum excursion. Any ventilated box would need a strict subsonic/low cut filter too anyway to prevent damage below the port tuning frequency.

If you want to use it for really low frequencies, you'd have to go for a front loaded horn, but that will be big. And if I say big, I mean REALLY big, easily above 5-600l.
 

hottattoo

Member
2006-09-16 10:55 pm
vinylnvalves,

Glad to hear you are going for a 3 way system. A horn mid range is an excellent choice but you will have to pad it down to the Supravox driver level. Do you already have the tpl150 and mid range compression drivers ?

My reason for suggesting caution when using your Supravox driver with EQ at low frequencies comes from an experience at the Newport audio show 2 years ago. My friend is the USA importer for Cessaro speakers which uses a modified Supravox 285-2000 ( If I recall right ) in the Chopin model. It is a 2 way speaker using a TAD 2001 for mids and up and the Supravox in a back loaded horn. On the second day of the show a cable got pulled out accidentally while the system was powered up. My friend was using a Tron preamp and 300b mono blocks so needless to say there was a fairly loud pop but the system played just fine. The next morning (6 am) my friend checked over the system and heard a slight buzz, upon inspection of the Supravox drivers there was 2 or 3 25mm to 35mm slits going around the surrounds of both drivers. OMG, what to do, so I went to Home Depot and got some crazy glue gel and we spent the next 3 hours repairing both drivers before the show started--what a royal PIA !! However, luck was on our side, and we received best sound of the show by several reviewers. This damage happened with an 8 watt 300b amp---and NO driver eq. If the drivers would have had some low frequency eq the cones would have been in the middle of the floor !!! Drivers with light paper cones and powerful motors are more prone to this type of damage. So...use those nice drivers in their comfort zone, don't push them and you will be rewarded with excellent sound. Use subs if you want frequencies below 40hz.
 
Drivers with light paper cones and powerful motors are more prone to this type of damage. So...use those nice drivers in their comfort zone, don't push them and you will be rewarded with excellent sound.

That's right. Especally because the Supravox drivers are built like the classic drivers, in every regard and these drivers are much more sensitive to manhandling. Home cinema with high volume effects at very low frequencies
is exactly what they can't do - at all!

Use subs if you want frequencies below 40hz.

I fully agree there but - then there's no need for a 15" driver above the sub since a 10 or 12" will do everything better with much less volume.
 
I am a little confused by the concerns over the robustness of the drivers. Same concerns for altec drivers? I have a pair of Altec 414's and they have the same surrounds and weight of cones. How I am reading the comments is that these 15" drivers don't really have a place in modern playback systems that require a response below 50hz.
I do find the presence of 15" drivers with the body they add is something I miss from a 12" driver. ( the reason why I have a pair of beyma 12p80nds gathering dust)
BTW- I had found a discussion thread on a French audio site of somebody using them in a karlson style cabinet. Very interesting but is probably as far away from the sealed baffle, with multiple passage resonances and a combined front and rear wave. The compactness of the karlson is appealing though.
 
I am a little confused by the concerns over the robustness of the drivers. Same concerns for altec drivers? I have a pair of Altec 414's and they have the same surrounds and weight of cones.

What's your point? The parameters often dictate what can be done with drivers and what not. Not every speaker works in every enclosure. The 414 can be tuned much deeper because they have different TSP, in this case it's the (relatively) heavyer Mms (66g vs. 53g for the smaller driver), which allows thirtysomething Hz quite easily. In a sealed box however it isn't going to be great either.

How I am reading the comments is that these 15" drivers don't really have a place in modern playback systems that require a response below 50hz.
I do find the presence of 15" drivers with the body they add is something I miss from a 12" driver. ( the reason why I have a pair of beyma 12p80nds gathering dust)

Well, then go for 15" for music, but that doesn't change the fact the Supravox performs poorly in a sealed enclosure and even ported it's still not fit for home cinema, because besides not going deep enough, it will reach the Xmax way too fast. You've mentioned the DSP but that won't help you either because boosting the low end won't give your driver more excursion, it's the opposite, it will push it over the limit even faster. Yes, it will go deeper that way but not deeper louder, instead deeper and LESS loud.

BTW- I had found a discussion thread on a French audio site of somebody using them in a karlson style cabinet. Very interesting but is probably as far away from the sealed baffle, with multiple passage resonances and a combined front and rear wave. The compactness of the karlson is appealing though.

As I said before, the Karlsson won't help you because the low end is the limit and the Karlsson doesn't perform in that range any better than a BR enclosure.