Comparison of Volt B2500.1, B250.8, RV3143 and S/S 25W8565-01

Volt drivers are not usually discussed here on the DIY boards, or if they are nowhere near as often as SEAS, vifa, peerless or SS.
I would imagine less people will have experience with them so you may not get lots of responses. Having said that from bits and bobs that ive picked up over the years, volts are meant to be very good, I have never seem a bad bit of press surrounding them.

I've used all 3 volt driver:-

B250.8 Very Good. Smooth tight Bass
B2500.1 One of the very best bass drivers. VERY tight bass, massive power handling. Very critical on bad recordings
RV3143 Similar to the B2500.1 More forgiving. Don't use above 300Hz.

If you are using the SM75-150 - go with B2500.1 or B250.8
and don't listen to what others say about crossing over at 800Hz.
Use the SM75-150 at 380Hz - As ATC do - Amazing sound
I used 70L tuned to 30Hz. Im building some more at the
moment using 2 drivers in 100L enclosure. These will probably crack the walls! If you use the RV3143 then I would use 75L tuned to around 35Hz. Either drivers will be amazing. The main
thing you will notice is no bass boom
Thank you very much for your information. It allowed my final decision to go with B2500.1. B2500.1 seems to be better than RV3143 at least in 2 aspects:

B2500.1 has lower bottom end response than RV3143 with around 70 liter volume.
RV3143 may not be good for SM75-150 as SM75-150 is not recommended to crossover at as low as 300Hz.

Am I right?
Question for spd.
I just got an offer, at a very good price, of a pair of mothballed unused Volt B250s. They are the original model in the series.
There's no spec sheeet with them. Volt say the specs would be "similar to the B250.8" but don't have a sheet
Do you or anyone else have the parameters for this model lying about somewhere?
I'd use them for bass bins following the suggestion of a 35litre enclosure on the B250.8 page of the website,

but I'd like to run the numbers accurately first
Help gratefully received

If you are crossing over above 300Hz then go for the B2500.
The RV3143 is louder and as I said before it is more forgiving for old recordings. Both units have very similar qualities. The B2500
can be difficult to use because of the low Q. You will need to
fill the enclosure 2/3 with wadding.

Spec for B250.1:-
I got this from an old Wilmslow Audio cat. I'm not convinced
that it's correct but here goes
sens 93dB ??
Fs 27Hz
Qa 1.84
Qe 0.27
Qt 0.24
Vas 116L
Power 125W
Mechanical details are the same as B250.8

It could be the B2500.1 but also it could be a custom
version. Certainly the B2500 would work well for this type of
application. Personally I don't like seperate sub-bass systems.
If you really want bass slam and mid bass drive then put all
the drive units in the same enclosure and forward mount the
bass drivers in-line with the mid and HF units as you would in
a conventional floor standing enclosure.
If you are going to use the B2500 then make sure you use a
mid range unit that is of equal quality. This bass driver is very revealing and does not suffer weaker components in the system.
diyAudio Member
Joined 2004
Thanks spd.

Can I ask another question?

I'm currently researching a sub-bass enclosure and after hearing the Stentor III in Bristol last weekend I'm seriously considering one based on a Volt driver and specifically the 2500.1

My aim is to get the same sort of lows that I experienced whilst there. Pretty sure the Stentor goes to 11hz -6dB so thats what I'm looking at getting.

Anyway what I'd like to ask is would the 2500.1 perform well in a sealed enclosure and what qts value would be acceptable using this driver. I've ran the figures on ISD but the response seems horribly biased to the mid-bass rather than the really low <30hz, which is what I'm after.

Am I doing something wrong?

Or would I be better off designing a transmission line or maybe a reflex enclosure?

Use a ported design for the B2500.1. Not IB
If you use a passive crossover then with a 70L enclosure
tuned to 30Hz you should get -6dB at around 26Hz

If you intend to use an active xover then it's possible by
careful design to trade off efficency for lower frequency response.
I guess this it what Rel do
Digital crossover

Hi All,

It's good to be back here after all. Just for background information, I had Wilmslow build my speakers with a Volt B2500.1, an ATC SM75-150 and a Scanspeak 97000. The enclosure is 70l, but I guess it doesn't matter for my following question:

I am now trying some digital active crossover on a floating-point DSP. There are 3 sharp FIR filters (for linear-phase response), an LPF for the woofer, a BPF for the mid, and the HPF for the tweeter. The filter specification is as below, and I could get acceptable filter length that fits in a powerful 250MHz DSP. But I am not sure if they would sound right, and want experts' review.

1. LPF: transition from 380Hz to 760Hz, -3dB to -130dB
2. BPF: 1st transition from 380Hz to 760Hz, -130dB to -3dB
2nd transition from 3800Hz to 4500Hz, -3dB to -130dB
3. HPF: transition from 3800Hz to 4500Hz, -130dB to -3dB

Passband ripple is set to maximum 0.01dB.

I am especially concerned about the crossover between the mid and the tweeter since mid stretches up to 4500Hz. Could you review the transitions above and let me know what you think?

Thanks in advance for your helps. :)

For the SM75-150 you will need to apply equalisation and also allow for baffle step. Ideally you will need to take measurements using a microphone
Also drive unit baffle location is important especially with the ATC unit. The ATC is difficult to implement but if you get it right the sound is stunning. Theoretcical electrical crossovers are not going to work.
Do you have a passive crossover design for these drivers?

Thank you for your reply. I was not clear about your points, but I definitely agree with you. I am now in the prototyping stage for the FIR crossover S/W, and the equalization for room response and non-flat response of the drivers will be handled by a different S/W module which already exists. So, in this digital FIR crossover module, I just need to apply the theoretical and strict crossover only.

I am currently using the crossover designed by Wilmslow Audio, but I'd like to start from scratch, as FIR characteristics is pretty different from IIRs with similar design parameter. Your advice on transition frequencies (-3dB and -1xxdB) would be greatly appreciated.

I have only used upto 4th order passive filters with these drivers, although the best sounding solution seemed to be 3rd order. The main problem was more to do with equalising the ATC unit and baffle step correction. The ATC is fairly easy to integrate with the HF unit. (I've used both SEAS and Morel tweeters). Bass driver integration is more difficult. The crossover points were:-

Bass LP -9dB at 380Hz (Allowing for baffle step)
Mid HP -6dB at 380Hz
Mid LP -6dB at 3500Hz
HF HP -6dB at 3500Hz

All filters -18dB/octave acoustic and all drive units connected in phase.
Note: The ATC requires equalisation as there is a response peak at around 1kHz

Would you be willing to share your eq at 1khz for the 75-150?
I have a 3 way with Raven r1 / 75-150 / volt 3143 and I notice an edge in that 1k range. I don't think it is very high Q but sticks out in relation to the incredible smoothness of the ATC over the rest of it's range. Do you use a zoebel on either the ATC or your Volt LF? Thanks
Crossover Volt/ATC/SEAS


I have attached the crossover I use for the volt RV3143 and ATC 75-150S. I strongly recommend that the ATC unit be crossed over at 380Hz for best sound, however, this requires equalisation to remove a response peak at around 1kHz. For higher crossover points equalisation is usually not necessary but you won't be getting the best out of the ATC so don't do it. I have also indicated which components can be adjusted for fine tuning. The bass filter also allows for baffle step adjustment . The value shown (1 ohm) gives 3dB bass gain. (0.3 ohms is flat)


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