What 1" compression tweeter and crossover unit should I put in my cab?

[Dev R]

Hi. I am building my own 2 x10" bass cab and used the WinISD programme to design it. I am using 2 x Celestion BN10-300X watts speakers at 8ohms each wired in parallel making the cab  600 watts in total at 4 ohms. My question is, What compression tweeter and crossover unit should I put in my cab to match? Do I need to buy a tweeter that is rated 4 ohms and 600 watts? The same question with the crossover unit. I see a lot of tweeters and crossover units on the market that all seem to be rated at 8 ohms. I will be powering the speakers through a Markbass amp at 500 watts. Thanks in advance!

[Bill Fitzmaurice]

With bass cabs I use the Eminence BGH25-8. It's rated at 25 watts, because that's all there is above 2kHz with 500 watts program. There are few, if any, off the shelf 4 ohm crossovers, but off the shelf crossovers aren't very good. I design my own. This is an 8 ohm 2kHz 4th order high pass filter, which you can't buy from anywhere in the UK. The capacitors are poly or mylar, rated for at least 100 volts. The coils are air core, of the smallest available wire gauge with no more than 0.5 ohms DCR. A plus/minus 10% tolerance of the component values is permissible.

                                                                              

 

This is a 4 ohm 2kHz 2nd order low pass filter. The capacitor is a non-polar electrolytic (NPE), rated for at least 50 volts. The coil may be solid or air core; what’s critical is that the DCR (resistance) of the coil for a 4 ohm system be less than 0.2 ohms. A plus/minus 10% tolerance of the component values is permissible. Being 4 ohms you can't buy one of these either.  

                                              

                                                                      

I always build my filters on separate boards, it's too easy to get confused with the layout and wiring putting them on the same board.

 

 

 

 

[Dev R]

Thank you very much Bill for answering my question. Great stuff. I will now look into obtaining all the components needed.

[Dev R]

Hi Bill. So you wouldn't recommend an off the shelf crossover like this example?

[Bill Fitzmaurice]

That only has a 2nd order high pass, which is totally inadequate. 3rd order is the minimum acceptable for pro use. The 4th order I use reduces the power to the tweeter an octave below the knee frequency by an additional 12dB compared to a 2nd order. That makes the difference between clean and distorted, as well as between functioning and blown. 

[Dev R]

Thank you once again. I will use the same design and components you have given me above for the crossover! Cheers Bill

[BassmanPaul]

@Bill Fitzmaurice Y'know Bill, I have been reading your posts both here and the dreaded TalkBass for many years. I, for one, appreciate the time and effort you invest to help folks with their loudspeaker problems. Thank you sir for what you do.

 

[Bill Fitzmaurice]

Aside from playing golf I've nothing else to do. 😄

[Dan Dare]

23 hours ago, Bill Fitzmaurice said:

Aside from playing golf I've nothing else to do. 😄

 

Take up fishing. I find it a great way to while away my twilight years.

[Dev R]

Hi Bill. Just about to order the parts for the crossovers. Would you recommend an  L-Pad Attenuator to go with this build or not? And one more question. Is it right that you have to wire one speaker (tweeter) backwards (+ to -) because of 180 degree phase shifting? Thanks

[Bill Fitzmaurice]

The LPad can't hurt, but since you have dual woofers at 4 ohms that will even things out a bit. You usually have to reverse wire the tweeter with a 2nd order/2nd order crossover, another reason why I never use them. But it doesn't hurt to run a 2kHz tone through the system before you button it up, trying the tweeter wiring both ways, going with whichever is louder if there is any difference.

[Dev R]

Thank you again Bill

[Dev R]

I shall obviously use the L Pad to control the tweeter volume. Would I have to get an L Pad rated at 8ohm to match the Eminence BGH25-8 tweeter or 4 ohms to match the woofers?. That is my final question on this matter....I promise!! Thanks

[Bill Fitzmaurice]

The LPad goes between the high pass filter and the tweeter, so it's 8 ohm. Besides, you can only find them in 8 ohm. Where questions are concerned better to ask than to have a problem.

[Dev R]

            Hi Bill. Before I solder the components on the board, I just wanted to be re-assured that you're happy with this layout. Cheers

 

[Bill Fitzmaurice]

It looks fine. Much ado is made about inductor orientation, but it's moot with that much spacing.

[stevie]

As it happens, I have a pair of 8-ohm Celestion BN10-300X drivers here, with measurements saved on my PC. Having run these through a crossover simulation program, I'd recommend that you do not use a low pass filter because the driver rolls off naturally quite early anyway and you don't want to run the risk of dropping the impedance too much below 4 ohms. Just run the driver full range.

 

I see you've already bought the components - so try it with and without and see which you prefer.

Edited November 29, 2023 by stevie

[Dev R]

Thank you for your input Stevie. I will try it both ways!

[JohnDaBass]

On 24/12/2023 at 11:50, Dev R said:

Thank you for your input Stevie. I will try it both ways!

Which sounded the best?

[BassmanPaul]

On 24/12/2023 at 06:50, Dev R said:

Thank you for your input Stevie. I will try it both ways!

Wot? and risk having kids?

 

[Dev R]

Hi Bill Fitzmaurice. Just giving you an update on my crossover progress. So I've been running my bass cab with the crossover unit I built, as in the above photo, for about a year now but for some reason I'm getting a lot of "clipping" on my low notes, most notably on the E string. The amp I use to run the cabs is an Little Mark Tube 500 watts. My speakers are as I explained In my first question to you dated July 23rd. 2023. Do you think it could be the crossover unit causing the "clipping?" Should I try something else? Thanks. Dev

[stevie]

If you're using that crossover, I'd say it's highly likely to be the cause. Try bypassing the LF section of your crossover and wiring direct to the bass drivers. Then you'll know. 

[JohnDaBass]

48 minutes ago, stevie said:

If you're using that crossover, I'd say it's highly likely to be the cause. Try bypassing the LF section of your crossover and wiring direct to the bass drivers. Then you'll know. 

I followed this thread and repurposed a SWR Goliath Junior Mark 1 (Eden USA made) 2x10 cab.

Used the same two Celestion BN10-300X and an Eminence BGH25-8 as recommended by Bill Fitzmaurice.

I only used the HF part of the crossover and followed @stevie advice and connected the two BN 10 -300x direct to the input.

With new ports the system worked really well. I integrated the variable HF control which provided extra control over the HF.

I have been very happy with the performance of the modified system and I am grateful for the help and advice from @stevie and @Bill Fitzmaurice.

It's a very loud versatile cab with huge tight bottom end.

Edited 47 minutes ago by JohnDaBass
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[Bill Fitzmaurice]

Unless the low pass inductor is seriously undersized, resulting in high DCR and potentially going into saturation, a low pass filter won't cause clipping of the low notes. That's usually the result of inadequate driver xMax/Vd, sometimes by the cab size and tuning. If you went with the WinISD default of 41 L per driver with 58Hz tuning you'd run out of excursion at only 80 watts per driver at 50Hz and lower. Without knowing the cab specs that's all I can offer. If I was using that driver I'd ignore the WinISD default and go with 30L per driver and 45Hz  tuning. If you did use the WinISD default making the port(s) long enough to get to 45Hz tuning would be better, and since the net box volume should be smaller as well you've got the room for it.