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Old 4th May 2021, 10:29 pm   #1
Rogercov
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Default Replacement 4 ohm speaker help please

Hi All i want to replace the 20cm base speaker unit in my Hitachi speakers as they are getting a bit worn and spliting. the speakers are ss-8470g MK2 from a old music centre . The speakers are 4 ohm , could they be replaced with 8 ohm ? and would modern speakers cause any damage , there is a unit inside speaker cabinet (see picture attached) that i dont know what it is for , does it split sound to tweeter unit? is there a good place to buy them from here in the UK many thanks for all help Rog
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Old 5th May 2021, 4:51 am   #2
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Default Re: Replacment 4 ohm speaker help please

Is the actual driver 4 ohm? It may not be. The "unit" is a cross over and as you say "splits" music off to the tweeter or more correctly forms a filter so that low frequencies go to the woofer and highs to the tweeter.

What exactly is splitting? Woofers, drivers can be repaired and re foamed. You could replace it with a car speaker perhaps but it may or may not sound right.

Andy.
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Old 5th May 2021, 7:04 am   #3
Edward Huggins
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Default Re: Replacment 4 ohm speaker help please

You would do far better to change these whole speakers for a S/H pair of English made speakers. A pair of half decent 8" Bass/Mid range drivers will cost you 30-00 or more, when for the similar money you could buy a really decent pair of 1980s Wharfedales, Celestions, Goodmans or Tannoys. If you are concerned about originality, then first of all try to repair the cone/s if the surrounds have come away. There is much on this site to guide you - search "Repairing Loudspeaker Cones".
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Old 5th May 2021, 8:50 am   #4
simpsons
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Default Re: Replacement 4 ohm speaker help please

Hmmm. Well a picture says a thousand words and so it is with the Hitachi speakers you have.

From just a cursory look at eBay, the foam surrounds are the weak link and can easily be replaced for pennies.

The picture also tells me that the tweeter was made by Goodmans and I guess so will the bass unit.

The small printed circuit board is, as said, designed to filter or split low notes for the bass large speaker and the tweeter.

Goodmans made 2 tweeters which look the same. DT3 for low cost boxes and type 571071 which according to Pink Fish Media are as different to chalk and cheese. Both are said to 8 ohm units. The better ones are used in the Goodmans Magnum and Minister Loudspeakers both also specified as 8 ohm impedance. Look at the back of yours to find out which type you have.

Using a "Car" loudspeaker, even if you could find one 20cm or so, would be, in my opinion, throwing good money after bad as the printed circuit board is designed to be used with specific speakers only.

Replacement 20cm or 8" (as when made) speakers are expensive and to answer you question 8 or 4 ohms I wonder if the bass is 4 ohms to tame the brightness of the tweeter.

To cut a long story short, my recommendation would be to re foam them.

Sorry if I was a little long winded but when a label says one thing "4 ohms" and the speaker manufacturer says something different, the first question must be why.

Chris

Last edited by simpsons; 5th May 2021 at 8:58 am.
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Old 5th May 2021, 6:30 pm   #5
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Default Re: Replacement 4 ohm speaker help please

Thank you for reply , My tweeters are the 571071 so that is good news. The bass unit is indeed 4 ohms, it looks like I may not be able to refoam as someone has stuck them with all sorts of glue. I have found some speakers at 19.99:-

Peak power: 200W
Power max: 100W
Speaker size: 8"
Impedance: 4 Ohm
Frequency response: 65Hz - 4kHz
SPL @ 1W/1m: 89dB
Voice coil: 38mm
Magnet weight: 20 oz

Do you think these would replace mine? I know they are cheap but hopefully better than my split ones.

Many thanks, Rog.
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Old 6th May 2021, 9:42 am   #6
Edward Huggins
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Default Re: Replacement 4 ohm speaker help please

These are liable to be better than the originals, but those Hitachi cabinets were not the best constructed. You may never get you money that on these so you still might be better off with a pair of (always saleable) Tannoy M2 or Mercury Tannoys for 40-00. My view only!
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Old 6th May 2021, 4:29 pm   #7
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Default Re: Replacement 4 ohm speaker help please

A 571071 eh?

This is good news. Now before any recommendation on the speakers you have sourced, would you please advise the value of the capacitors used on the crossover printed circuit board and if the coils have a value.

The capacitors will read, for example, 2.2 mF and the coils 10mH. Each will be different and for reference, a capacitor will be in series with the tweeter with a coil across its terminals so only high notes are fed to it whilst, the woofer will have the coil in series with it and the capacitor across its terminals.

It would be helpful if you would also advise the source of the 19.99 woofer which sounds, on the face of it, good value.

In the meantime, I'll try and find the tweeter details so that, probably with the help other members, we can ensure you have enough information to make a decision on the woofers you have found.

Again, sorry if this is all a bit long winded but, and I mean but, there is an awful lot of detail required when choosing speakers, cross over frequencies etc.

Chris
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Old 6th May 2021, 7:08 pm   #8
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Default Re: Replacement 4 ohm speaker help please

This is not a recommendation but there are 2 off Goodmans 8" Havant Loudspeakers for sale on the well known site for 15 each inc p&p.

They have rubber suspension. The seller states 8 ohm but Goodmand's say the Havant is 4 ohms.

The Havant is a 3 way speaker but the tweeter you have works well with a crossover frequency of as low as 2kHz which if the capacitors values are OK, these Havant speakers should be a good match.

The Havants appear to be housed in the same pressed steel chassis as the Goodmans 8HPA speakers which are also general purpose speakers.

Anyway, search "Goodmans Havant vintage" and see what you think.

Should other members have a view on this post please add to or challenge my views.


Chris
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Old 6th May 2021, 10:25 pm   #9
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Default Re: Replacement 4 ohm speaker help please

Let's rewind back to the beginning.

The speakers supplied with music centres were usually far from the best, and it was a common upgrade at the time to buy it without speakers and get some British made ones instead, from a reputable brand.

8 Ohm speakers in theory won't play quite as loud as the original 4 Ohm ones, from the same amplifier. In reality, speaker efficiency varies quite a lot, and the 8 Ohm ones will not be quite so hard on the amplifier. So the simple theory isn't a reliable guide. 8 Ohms should be fine.

Which would be the best ones to get?

Beats me! they all have advantages and disadvantages. Practically speaking, it's a case of which ones turn up when you start looking.

Size is important. Bigger speakers are less compromised than smaller ones. In general, go for the biggest you can get away with because larger ones not only are better, they are cheaper because they are unfashionable. This tells you a lot about fashion!
Speakers with removable fronts are the best bet, you can remove the grilles and check that the foam or rubber surrounds on the driver cones aren't splitting.

With a bit of care you can get something good for little money. With some luck and a tolerance of larger cabinets, for free is a possibility. Expect to have to collect them. Heavier is also a good sign.

KEF
Goodmans
Wharfedale
Celestion
Monitor Audio
Mission
Bowers and Wilkins aka B&W
Tannoy
Spendor
Rogers
Mordaunt & Short

There are many more British makes worth having. Some are still expensive, but sometimes you come across someone who just wants rid with minimum effort.

These things are fully depreciated. If they are in good order and you don't in the end like them, you can flog them for about what they cost and try again.

Good hunting!

David
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Old 6th May 2021, 10:43 pm   #10
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Default Re: Replacement 4 ohm speaker help please

Again thank you all for the help . The cheap speakers I found were on ebay Skytec 902.245 8 Inch Replacement Speaker Driver 100W.

CCA0183 - Skytec 8" SP800 Voice Speaker Driver 100W

A 100 watt 8 Inch 4 Ohms replacement chassis speaker with a stiff suspension and vented magnet producing an excellent sound quality. Ideal for use in sound combinations too.

Features

4 Ohms impedanceVented magnetsStiff suspensionSpade terminals

Specifications

Peak power: 200WPower max: 100WSpeaker size: 8"Impedance: 4 OhmFrequency response: 65Hz - 4kHzSPL @ 1W/1m: 89dBVoice coil: 38mmMagnet weight: 20 oz

Any more thoughts Are they a waste of money . Thanks again for all your help . Rog
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Old 6th May 2021, 10:48 pm   #11
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Default Re: Replacement 4 ohm speaker help please

Also found these
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Old 7th May 2021, 6:02 am   #12
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Default Re: Replacement 4 ohm speaker help please

This is what is inside the speaker boxes Many thanks
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Old 7th May 2021, 7:53 am   #13
Edward Huggins
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Default Re: Replacement 4 ohm speaker help please

In your Post #10 you ask if these new Bass/Mid drive units are a waste of money?
No, they are not, and they appear to be of good quality.
What is a waste of your money is you putting these into those enclosures!
You are trying to make these modest Hitachi speakers something they never can be......
Take the well-intentioned advice of me and others - just go buy a decent pair of British Hi Fi speakers for the same money. Simples.
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Old 7th May 2021, 8:48 am   #14
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Default Re: Replacement 4 ohm speaker help please

OK. The first picture is of the bass loudspeaker capacitor which shows a value of 16MF. The second pic, which is for the tweeter shows that it has a 50 volt rating, important but would you rotate it so that the MF value can be seen.

Now on to the ebay woofers. Unlike the original speakers which had a flexible suspension, the Skytec 902.245 has as stiff suspension, this is important.

There are members who have a better understanding of loudspeaker design, but from my experience, the suspension is important. For example a bass guitar speaker will have a stiff suspension to handle high volumes in an open enclosure. A flexible suspension is needed in an enclosed or bass reflex loudspeaker to obtain the maximum sound for a given input.

Your loudspeaker designer will have chosen a speaker with just enough flexible suspension so that bass notes do not move the speaker cone too far but certainly enough to create a balanced sound with the music center it was designed for. Note, the Hitachi speakers you have were made by Goodmans.

Unless a more knowledgeable member says otherwise, for the reasons said, I would not buy the eBay Sktec speakers.

Now, both David, of Radio Wrangler, and Edward Huggins makes some good points however it depends on your budget and what amplfier/music center you have and its intended use. Good HiFi speakers come at a price and 100 plus postage isn't unknown and the more sought after well, 250 is not unreasonable.

So its back to you Rog.
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Old 7th May 2021, 7:23 pm   #15
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Default Re: Replacement 4 ohm speaker help please

Hi Again . First i would like to say a big thankyou to all who have helped and commented on this, what a weath of knowledge you have.

Firstly to Simpsons, please see picture attached of the tweeter capacitor i see it says 3.3 MFD. The music center i have is a Hitachi sdt400 please see attached picture.

To Edward Huggins , i totaly understand what you are saying but will have to save for a bit to get a full new set ( richer sounds) have some speakers
Mordaunt Short
Colour Black
Impedance (ohms) 8
Power Rating (Watts) 80
Weight (KG) 3.1
Black Yes
Freq Response (Hz) 41 - 20,000
Speaker Enclosure Type Bass Reflex
Speaker Dimensions WxDxH (mm) 165 x 218 x 290
these are 99

These are 8ohms my question, if i get these in the future will using 8ohm speakers instead of 4ohms cause any damage to my music center over time?

Back to the ebay Skytec 902.245 speakers with its stiff suspension, if i bought these as a stop gap and used these in the old enclosures (which i like the look of) i know Edward said this was not great, would they still sound ok i dont have the volume up high and to be fair the old speakers with rotted foam and a poor repair dont sound too bad to me ?? and would this stiff suspension make the sound poor in some way.

would these be better than the skytec Monacor SP-202E 8" 4 Ohm HiFi bass midrange speaker from the Blue Aran http://www.bluearan.co.uk/index.php?id=MON103980 but not much info on them? and i dont understand the graph on the page

Many thanks Rog
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Old 7th May 2021, 8:26 pm   #16
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Default Re: Replacement 4 ohm speaker help please

Hi Rog,

Your SDT400 music centre is a lovely thing, but the speakers that came with it weren't, even when new! Yes, they have Goodmans drivers, but they were their bargain basement range. I really wouldn't throw good money after bad by replacing the bass drivers.

As many people have already said, look out for a secondhand pair of decent hifi speakers from the 1970s/80s/90s. I have bought several in charity shops for 20 or so per pair, including ones by Celestion, Kef, Wharfdale, Mission, Rogers and so on. There will be some on Freecycle too, no doubt. I would be very surprised if a pair of these didn't dramatically improve the sound quality, for very little outlay.

If you ever come up to Oxford, I have a pair of big mid-70s Wharfedales which work perfectly which you can have free of charge, just message me.

Nick.
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Old 7th May 2021, 8:29 pm   #17
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Default Re: Replacement 4 ohm speaker help please

Monacor are reputable makers of good quality speaker drive units. Those have soft surrounds.

speakers with soft surrounds rely on air pressure within the cabinet to provide their restoring force. This could be a sealed cabinet, or the back-pressure from a ported cabinet. Speakers with stiff surrounds provide all their own restoring force and were made to work in very open cabinets. The springiness and the mass of air driven by speakers creates a resonance, and cabinet design and surround design is intended to place this resonance where it is wanted.

Whether this speaker matches up with the simple crossover and tweeter you already have is unknown. Whether they will sound good is also unknown. The only way to find out is to try them. This unfortunately doesn't fix the risk of you wasting your money.

If you aren't fussed about buying new, people are giving away quite decent second hand speakers for free, if you look around.

David

EDIT: Cross-posted with Nick.... there you are, an offer of free ones right out of the blue!
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Old 8th May 2021, 8:39 am   #18
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Default Re: Replacement 4 ohm speaker help please

Rog, the weakest link in the chain when it comes to listening sound will be the loudspeaker.

Your Hitachi music centre when first sold was well regarded and a cut above many others. Although we all have different opinions on how we like to hear sound, you will hear "warm," "bright" and so on, at the end of the day the tone controls can shape the sound. What is difficult is to make a poor loudspeaker sound natural.

Earlier the size of the speaker was highlighted and the reason for this is that all a loudspeaker has to do is move air. Low notes require a lot of air being moved. Small loudspeakers can be built to do this but that comes at price.

I can only find one review on the M20, which is on You Tube. Well words fail me.

The review quite clearly shows them to be, at the best, light in bass to which we are told, "don't worry" all you have to do is use them for a few days, years, well who knows but after that all will be well. The reviewer then offers a link to buy them. An independent review, not sure. Other reviews on Amazon and Richer Sounds you can take or leave them. I would leave them.

The Monacor I'm sure is a good loudspeaker and the technical detail should be sufficient to design a crossover to suit it and your tweeter but I don't have those skills. What I can tell you is how important it is to do that otherwise you will be disappointed. I also see that it has foam suspension, I would always go for rubber.

For my money, either follow up Nick's kind offer, review and buy S/H good quality speakers, increase your budget or for thirty notes buy the used Goodmans Havent speakers which at least come from the same stable, so to speak.

Chris
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Old 8th May 2021, 1:22 pm   #19
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Default Re: Replacement 4 ohm speaker help please

Hi All

Thank you all for help and advice , i have learnt a lot from you all .I have Messaged Nick About his kind offer of the speakers , which i hope to collect next month. I will keep you all informed on how i get on with my Music centre ..

Many Thanks Rog
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Old 8th May 2021, 1:56 pm   #20
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Default Re: Replacement 4 ohm speaker help please

Please let us know how it goes once you try them. It makes a more satisfying ending to a thread than letting it just stop with no conclusion, and avoids discouraging people from helping.

David
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